毕业设计外文翻译
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引言概述:在现代高等教育中,毕业设计(或称为毕业论文、学士论文等)是学生完成学业的重要环节。
而对于一些特定的专业,例如翻译专业,有时候还需要完成外文翻译这一项任务。
本文将探讨毕设外文翻译的意义和目的,以及为什么对翻译专业的学生而言这一任务极其重要。
正文内容:1.提高翻译能力和技巧外文翻译是一项对翻译专业学生而言十分重要的任务,通过进行外文翻译,学生们可以通过实践提高自己的翻译能力和技巧。
在这个过程中,他们可以学习如何处理不同类型的外文文本,熟悉不同领域的专业术语,并掌握一些常用的翻译技巧和策略。
2.扩展语言和文化知识毕设外文翻译要求学生们对翻译语言的相关知识和背景有一定的了解。
在进行翻译时,学生们需要遵循目标语言的语法规则,并确保所翻译的内容准确、清晰地传达源语言的意义。
通过这一过程,学生们可以进一步扩展自己的语言和文化知识,提高自己的跨文化沟通能力。
3.提供实践机会毕设外文翻译为学生们提供了一个实践的机会,让他们能够将在课堂上所学到的理论知识应用于实际操作中。
通过实践,学生们可以对所学知识的理解更加深入,同时也可以发现并解决实际翻译过程中的问题和挑战。
这对于学生们将来从事翻译工作时具备更好的实践能力和经验具有重要意义。
4.培养翻译专业素养毕设外文翻译要求学生们具备良好的翻译专业素养。
在进行翻译过程中,学生们需要保持专业的态度和责任心,严谨地对待每一个翻译任务。
他们需要学会如何进行翻译质量的评估和控制,以确保最终翻译稿的准确性和流畅性。
这一系列的要求和实践,可以帮助学生们培养出色的翻译专业素养。
5.提升自我学习和研究能力毕设外文翻译要求学生们进行广泛的文献阅读和研究,以便更好地理解所翻译的内容,并找到适当的翻译方法和策略。
在这个过程中,学生们需要培养自己的自主学习和研究能力,提高对学术和专业领域的敏感性,并能够独立思考和解决问题。
这将对学生们未来的学术研究和进一步的职业发展产生积极的影响。
总结:引言概述:毕业设计外文翻译(Thesis Translation)是指在毕业设计过程中,对相关外文文献进行翻译,并将其应用于研究中,以提供理论支持和参考。
Structure in Design of ArchitectureAnd Structural Material专业:土木工程学生:指导老师:We have and the architects must deal with the spatial aspect of activity, physical, and symbolic needs in such a way that overall performance integrity is assured. Hence, he or she well wants to think of evolving a building environment as a total system of interacting and space forming subsystems. Is represents a complex challenge, and to meet it the architect will need a hierarchic design process that provides at least three levels of feedback thinking: schematic, preliminary, and final.Such a hierarchy is necessary if he or she is to avoid being confused , at conceptual stages of design thinking ,by the myriad detail issues that can distract attention from more basic considerations .In fact , we can say that an architect’s ability to distinguish the more basic form the more detailed issues is essential to his success as a designer .The object of the schematic feed back level is to generate and evaluate overall site-plan, activity-interaction, and building-configuration options .To do so the architect must be able to focus on the interaction of the basic attributes of the site context, the spatial organization, and the symbolism as determinants of physical form. This means that ,in schematic terms ,the architect may first conceive and model a building design as an organizational abstraction of essential performance-space in teractions.Then he or she may explore the overall space-form implications of the abstraction. As an actual building configuration option begins to emerge, it will be modified to include consideration for basic site conditions.At the schematic stage, it would also be helpful if the designer could visualize his or her options for achieving overall structural integrity and consider the constructive feasibility and economic of his or her scheme .But this will require that the architect and/or a consultant be able to conceptualize total-system structural options in terms of elemental detail .Such overall thinking can be easily fed back to improve the space-form scheme.At the preliminary level, the architect’s emphasis will shift to the elaboration of his or her more promising schematic design options .Here the architect’s structural needs will shift to approximate design of specific subsystem options. At this stage the total structural scheme is developed to a middle level of specificity by focusing on identification and design of major subsystems to the extent that their key geometric, component, and interactive properties are established .Basic subsystem interaction and design conflicts can thus be identified and resolved in the context of total-system objectives. Consultants can play a significant part in this effort; these preliminary-level decisions may also result in feedback that calls for refinement or even major change in schematic concepts.When the designer and the client are satisfied with the feasibility of a design proposal at the preliminary level, it means that the basic problems of overall design are solved and details arenot likely to produce major change .The focus shifts again ,and the design process moves into the final level .At this stage the emphasis will be on the detailed development of all subsystem specifics . Here the role of specialists from various fields, including structural engineering, is much larger, since all detail of the preliminary design must be worked out. Decisions made at this level may produce feedback into Level II that will result in changes. However, if Levels I and II are handled with insight, the relationship between the overall decisions, made at the schematic and preliminary levels, and the specifics of the final level should be such that gross redesign is not in question, Rather, the entire process should be one of moving in an evolutionary fashion from creation and refinement (or modification) of the more general properties of a total-system design concept, to the fleshing out of requisite elements and details.To summarize: At Level I, the architect must first establish, in conceptual terms, the overall space-form feasibility of basic schematic options. At this stage, collaboration with specialists can be helpful, but only if in the form of overall thinking. At Level II, the architect must be able to identify the major subsystem requirements implied by the scheme and substantial their interactive feasibility by approximating key component properties .That is, the properties of major subsystems need be worked out only in sufficient depth to very the inherent compatibility of their basic form-related and behavioral interaction . This will mean a somewhat more specific form of collaboration with specialists then that in level I .At level III ,the architect and the specific form of collaboration with specialists then that providing for all of the elemental design specifics required to produce biddable construction documents .Of course this success comes from the development of the Structural Material.The principal construction materials of earlier times were wood and masonry brick, stone, or tile, and similar materials. The courses or layers were bound together with mortar or bitumen, a tar like substance, or some other binding agent. The Greeks and Romans sometimes used iron rods or claps to strengthen their building. The columns of the Parthenon in Athens, for example, have holes drilled in them for iron bars that have now rusted away. The Romans also used a natural cement called puzzling, made from volcanic ash, that became as hard as stone under water.Both steel and cement, the two most important construction materials of modern times, were introduced in the nineteenth century. Steel, basically an alloy of iron and a small amount of carbon had been made up to that time by a laborious process that restricted it to such special uses as sword blades. After the invention of the Bessemer process in 1856, steel was available in large quantities at low prices. The enormous advantage of steel is its tensile force which, as we have seen, tends to pull apart many materials. New alloys have further, which is a tendency for it to weaken as a result of continual changes in stress.Modern cement, called Portland cement, was invented in 1824. It is a mixture of limestone and clay, which is heated and then ground into a power. It is mixed at or near the construction site with sand, aggregate small stones, crushed rock, or gravel, and water to make concrete. Different proportions of the ingredients produce concrete with different strength and weight. Concrete is very versatile; it can be poured, pumped, or even sprayed into all kinds of shapes. And whereas steel has great tensile strength, concrete has great strength under compression. Thus, the two substances complement each other.They also complement each other in another way: they have almost the same rate ofcontraction and expansion. They therefore can work together in situations where both compression and tension are factors. Steel rods are embedded in concrete to make reinforced concrete in concrete beams or structures where tensions will develop. Concrete and steel also form such a strong bond─ the force that unites them─ that the steel cannot slip within the concrete. Still another advantage is that steel does not rust in concrete. Acid corrodes steel, whereas concrete has an alkaline chemical reaction, the opposite of acid.The adoption of structural steel and reinforced concrete caused major changes in traditional construction practices. It was no longer necessary to use thick walls of stone or brick for multistory buildings, and it became much simpler to build fire-resistant floors. Both these changes served to reduce the cost of construction. It also became possible to erect buildings with greater heights and longer spans.Since the weight of modern structures is carried by the steel or concrete frame, the walls do not support the building. They have become curtain walls, which keep out the weather and let in light. In the earlier steel or concrete frame building, the curtain walls were generally made of masonry; they had the solid look of bearing walls. Today, however, curtain walls are often made of lightweight materials such as glass, aluminum, or plastic, in various combinations.Another advance in steel construction is the method of fastening together the beams. For many years the standard method was riveting. A rivet is a bolt with a head that looks like a blunt screw without threads. It is heated, placed in holes through the pieces of steel, and a second head is formed at the other end by hammering it to hold it in place. Riveting has now largely been replaced by welding, the joining together of pieces of steel by melting a steel material between them under high heat.Priestess’s concrete is an improved form of reinforcement. Steel r ods are bent into the shapes to give them the necessary degree of tensile strengths. They are then used to priestess concrete, usually by one of two different methods. The first is to leave channels in a concrete beam that correspond to the shapes of the steel rods. When the rods are run through the channels, they are then bonded to the concrete by filling the channels with grout, a thin mortar or binding agent. In the other (and more common) method, the priestesses steel rods are placed in the lower part of a form that corresponds to the shape of the finished structure, and the concrete is poured around them. Priestess’s concrete uses less steel and less concrete. Because it is a highly desirable material.Progressed concrete has made it possible to develop buildings with unusual shapes, like some of the modern, sports arenas, with large spaces unbroken by any obstructing supports. The uses for this relatively new structural method are constantly being developed.建筑中的结构设计及建筑材料专业:土木工程学生:指导老师:建筑师必须从一种全局的角度出发去处理建筑设计中应该考虑到的实用活动,物质及象征性的需求。
本科生毕业设计(论文)外文资料专业班级:学生姓名:指导教师:年月日cannot be duplicated, transplanted, and copied. Using the fingerprint to carry on the status recognition is one of mature biological recognition technologies. As a kind of information carrier, IC card can carry on the encryption to the stored information. It deposits and withdrawals data quickly, favors carrying on modernized information management. The fingerprint IC card system is a perfect integration of the advanced fingerprint recognition technology and the smart IC card technology. The system can compare the registered fingerprint with original fingerprint saved in the IC card which is taken with the user. In addition, the fingerprint IC card system can save all the necessary information of a person such as fingerprint and identification, thus ensuring its flexibility and generality . So it can be widely used in finance, transportation, medical service, credential and other domains that need identification. It has broad application prospect.This article is from …….指纹是人体生物特征之一。
编号:毕业设计(论文)外文翻译(原文)院(系):桂林电子科技大学职业技术学院专业:工商企业管理学生姓名:方智立学号:010*********指导教师单位:桂林电子科技大学职业技术学院姓名:朱芸芸职称:讲师2016年 4 月 1 日Marketing Strategy Analysis of SportsAbstractSports market is a special industry market, which for provide exchange of sports tangible products and services market. Sports market including fixed type, such as sports facilities, sports goods market, Mobile market, such as all kinds of sports service provided by the fitness club. Sports tourism and advertising business, sports goods should be consumers to accept, and occupy a larger market. If success of the sports marketing involves many factors. According to the specific characteristics of sports marketing, develop and implement appropriate marketing strategy is very important. Sports marketing strategy is to the sports business units within a certain period or stage marketing campaign's overall development plan of decision making.This paper argues that the marketing strategy can be further subdivided into market positioning strategy, market timing strategy, market entry strategy, market development strategy, market competition strategy, Choose a strategy, must conform to the enterprise's own competitive position, product status, to grasp the market opportunity, determined according to the demands of consumers. In this paper, the sports market segmentation marketing strategy for the market positioning strategy, market timing strategy, market entry strategy, market development strategy, market competition strategy, and discusses the sports marketing how to carry out strategic choice.Keywords: Sports bazaar ; Sports marketing; Marketing strategy1.Sports marketing strategy and characteristics1.1Sports marketing strategyStrategy refers to the planning of overall and profound things. Sports marketing strategy refers to the commodity business units under the guidance of modern marketing concept, to achieve its economic goal for enterprise in a certain period of the overall design and planning of marketing development.Inan increasingly competitive market circumstances, sports business units in order to effectively carry out business activities, to achieve its business objectives, must understand and based on the characteristics of marketing concepts and strategies, and Target the demand of the market, comprehensive analysis and marketing of various environmental factors, choose effective market strategy in the background.1.2The characteristics of the sports marketing strategySports marketing strategy has sports business units within a certain period or stage marketing campaign's overall development plan of decision making. It has the characteristics of the following.(1) Overall importance.Sports marketing strategy is a matter of the global business units, including two aspects the meaning of this global:on the one hand, Sports marketing strategy is the overall design, the development of the business units, including overall planning and the overall strategy and means.On the other hand, Sports marketing strategy decision is a matter of global business units and their all-round development in the future.(2)Secular.Sports marketing strategy is really about the future of sports business units: to achieve the goals of sports marketing strategy, will make the sports business units to produce qualitative leap, but this is not usually that can be done in the short term.Important, sports business units of marketing strategy on the strategic period not only very important to enterprise's survival and development, but also to the long-term development of enterprises play an important role.(3) Systematicness.Sports systemic marketing refers to business units, each part of the work of each link is a contact each other, are closely related to the organic unity of the whole.System have layers, the size and the primary and secondary division, at the next lower level to obey and serve at the next higher level.For a certain sports and business operation entity, the strategy of the whole enterprise as a whole system engineering to overall arrangement, the pursuit of the overall development of the biggest benefits.(4)Adaptability.Sports marketing adaptability, refers to the sports marketing and business operation entity is easily affected by external and internal environment, when the environment changes, sports business units made to adapt themselves to the new environment of the characteristics of rapid response.Sports marketing of the external environment including the market demand, political or economic situation changes, policy and law changes. Similarly, sports business entities internal conditions change will impact on marketing.(5)Risk.Due to sports marketing strategy is the business unit for the marketing activities during the period development collection of expected decision, and this decision is absolutely impossible in various conditions fully mature and information fully, make and sports market, especially the intangible product variety and complexity of the market, make sports marketing strategy has the characteristics of uncertainty and instantaneity, many market opportunities tend to be a passes, no longer to, opportunity and risk coexist.2.Sports marketing strategy comprisedand choiceSports marketing strategies mainly include market positioning strategy, market timing strategy, market entry strategy, market development strategy, market competition strategy.2.1 Market orientation strategyMarket positioning refers to the sports business units according to the condition of market competition situation and its own resources, establish and develop differentiated competitive advantage, to make their own products in the consumer formed in the difference between each product unique image and is superior to the competition.This unique image can be tangible or intangible.Enterprise after analyzing the market environment, should highlight its own market advantage, establish market position, Which companies need to know on a certain level of paper generalizes, consumers mind what is the best sports products as expected.2.2 Market entry policyMarket entry strategy is the sports business units at the right time to capture the target market, how to appropriately in the two aspects of production capacity and sales ability to make reliable measures and guarantee, to ensure the decision-making of sports products successfully enter the market.Its content mainly includes the production capacity of decision-making and sales ability to form two aspects.(1) Capacity Decision. In the necessary time, sports business entities formtargetmarket capacity, is one of the important conditions to achieve market goal.Regardless of whether they are sports tangible products and intangible products, generally there are two alternative strategies.①Independent development strategy refers to both tangible products, the development of sports and development of sports intangible products. All on its own strength to expand production scale, enhance the comprehensive production capacity or adjust the structure of the comprehensive production capacity of enterprise, to adapt the demand of product combination structure. ②Comprehensive development strategy, mainly depend on the sports business units of the external forces, namely, through joint, collaboration, subcontract, form a new comprehensive production capacity. Due to participating in planning, control, coordination, etc, are more difficult. Therefore, sports business units must be good at optimizing collaborator, deal with the various cooperation of responsibility, right and benefit, to maintain good relations of cooperation.(2) Sales ability decision. A sports product to enter and occupy the market, production enterprise must have the necessary sales ability and the ability to penetrate the market.Sales ability decision-making main consideration circulation channels and sales, product should be considered when making decisions, market, enterprise, social environment and the factors such as economic effect.2.3 Market development strategyMarket development strategy refers to the perspective of market prospects, the choice of market development means, usually includes two kinds of intensive development and diversified development main form.(1)Intensive development.When some kind of sports products in the market has the potential of further development, the choice of market penetration, product development and market development of three kinds of intensive development form. As the tangible products market, in sports and intangible products are common market and applicable.①Market penetration. on the basis of the existing market scale, increase the sales of existing products. Can use a variety of measures, consolidate old customers, increase the new user. ②Product development Is through developing and improving existing products, make its have some new properties and USES, meet the social demand more. ③market development. Refers to an enterprise that open up new product sales market, in order to increase sales.(2) Diversified development.Diversity is also called the diversification, basically have concentricity scattered scattered, horizontal dispersion and the integrityof three. ①Concentricity is sports business unit USES the original dispersed development technology and the characteristics, with its as the core, the development use different structure similar products. ②Scattered level of sexual development.Was used in the original market advantage, has occupied the market development of technology, nature and purpose of different products. For example, Sports club olicy makers, can through the player transfer channels, to sell players, profit.Others use their sports club or the player's social awareness to participate in the sales promotion of goods, in order to obtain profits. ③Integrity of dispersed development. Refers to the sports business units to expand the business into its original business, technology, market and the product has no connection in the industry. Such as the sports department construction and run a catering and service hotels, hotels, entertainment city, charge for parking lot, etc., is the form of scattered holistic development. Implement the diversification development, can improve the ability of sports business units to adapt to the environment, reduce the risk of a single business, at the same time, may be more fully use of all kinds of resources within the enterprise, make its have more potential development opportunities. However, the development of decentralized often leads to complication of operation and management, and business operation entities such as diversifying some problems.2.4Strategic Marketing CompetitionThe rules of the development of the market is superior bad discard, its characteristic is the petition can promote the economic development of the enterprise and the improvement of economic benefits.Enterprises should establish a clear concept of competition, flexible use of price and non-price competition means, take a man without I have, people have my good, good people knew, new I cheap, cheap I turn the principle and method of making enterprise competitive strategy, must accomplish know fairly well the competition environment and competition situation, can with ease.Enterprise competition environment factors mainly refers to the enterprise in addition to the social and cultural environment stress factors of various aspects, such as management scientist professor Michael porter of Harvard University famous the competitive offer slightly above, an enterprise usually exist competition pressure from five aspects, namely the industry competition pressure, potential to join the pressure from the industry, suppliers forward pressure (by providing raw materials or semi-finished products, to develop into their production products), buyers.(1) The overall competitive strategy. Under different conditions, the enterprise facing the pressure of competition is different, the analysis of the pressure of competition is to understand the purpose of each kind of competition situation of power, so as to make effective competition strategy.Under normal circumstances, the sports business units of competition strategy in general have a low cost strategy, product differentiation strategy and intensive strategy. ①low-cost strategy. Low cost strategy is to point to in under the premise of guarantee the quality of products and services, efforts to reduce the cost of production and sales so that the enterprise product prices lower than competitors' prices, with rapidly expanding sales increase market share. ②Product differentiation strategies. Product differentiation strategy is to point to create a unique characteristic of the enterprise products, to develop unique products or marketing programs, for in such aspects as product or service than competitors are unique. Thus to obtain the difference advantage.The United States, for example, "NIKE" brand sports shoes, NIKE production due to the appearance of novel design, the innovation of the use function and unique, and exquisite packaging, etc., although the price is surprisingly expensive, but occupies considerable market in China, the teenagers are very loving. ③Intensive strategy. Intensive strategy refers to the enterprises focus on one or several market segments provide the most effective service, better meet certain customers with different needs, so as to strive for the local competitive advantage. It is little different from the above three kinds of overall competition strategy, successfully implement these three strategies need different resources and decision-making, also should have different requirements on organization and management.(2) The competitive strategy of enterprises of different competitive position. Where the status of enterprise in market competition, the enterprise can be divided into: market leader, market challenger, market follower. Different competitive position of enterprises, should choose different market competitive strategy.①Dominant market competition strategy. Market power refers to the related products has the highest market share. Such as the current market position and stable dominated by clothing JinMeiLong, "ADIDAS", they are price changes, new product development, sales channel width and promotional efforts in a dominant position, recognized by other sports enterprises. ②The challenger market competition strategy. Market challenger refers to those in a secondary position in the market of the enterprise, such as "lining" brand garment enterprises .Market challenger to choosechallenge object is closely related to the strategic target, for a same object has different goals and strategies Such as attack market leader to gain the market share and product advantage ;Attack power with yourself quite seize its market position; Attacking small businesses taking their customers even small business itself."Lining" to win market price advantage to the international brand, with product quality advantages to gain "anta" challenger "peak" brand's market share. ③Followers of the market competition strategy. Market followers is to point to in a secondary position, under the conditions of "coexistence" market for as much as possible the benefit of the enterprise. Market followers don't need a lot of money, less risky and can obtain high profits, so many enterprises adopt this strategy, especially the sort of small or no fame and status of sports clothing enterprises. As the current sports "philharmonic" brand clothing enterprise in the enterprise.Reference[1] LiJianJun,WangCuiHua:The Research on Marketing Environment Enterprise of Things for Sports Use in China[J] Journal of NanJing institute of sport (social science edition) 2013.(10),36 ~ 48.[2] Discuss Sports market, products and marketing characteristics. [J] journal of xi ' an institute of physical education,2012.(3)101 ~109.[3] HuZhengMing Ed. Marketing Management[M].Shandong people's publishing house,2012.302 ~325.[4] [US]Kotler write. YuLiJun translate. Introduction to Marketing[M].Huaxia Publishing House,2011.333~389.[5] ZhangTongYao.Application areas to promote the marketing advantage analysis of third party logistics[J].Market of China,2010(3)128 ~136.[6] WangHuaiShu.The influence of the logistics quality of marketing[J].Teacher's Journal,2010(3)31 ~38.[7] WangChenWen.Shallow theory of logistics strategy in the role of marketing management[J].Chemical Enterprise Management,2009(7)175 ~178.。
A Design and Implementation of Active NetworkSocket ProgrammingK.L. Eddie Law, Roy LeungThe Edward S. Rogers Sr. Department of Electrical and Computer EngineeringUniversity of TorontoToronto, Canadaeddie@, roy.leung@utoronto.caAbstract—The concept of programmable nodes and active networks introduces programmability into communication networks. Code and data can be sent and modified on their ways to destinations. Recently, various research groups have designed and implemented their own design platforms. Each design has its own benefits and drawbacks. Moreover, there exists an interoperability problem among platforms. As a result, we introduce a concept that is similar to the network socket programming. We intentionally establish a set of simple interfaces for programming active applications. This set of interfaces, known as Active Network Socket Programming (ANSP), will be working on top of all other execution environments in future. Therefore, the ANSP offers a concept that is similar to “write once, run everywhere.” It is an open programming model that active applications can work on all execution environments. It solves the heterogeneity within active networks. This is especially useful when active applications need to access all regions within a heterogeneous network to deploy special service at critical points or to monitor the performance of the entire networks. Instead of introducing a new platform, our approach provides a thin, transparent layer on top of existing environments that can be easily installed for all active applications.Keywords-active networks; application programming interface; active network socket programming;I. I NTRODUCTIONIn 1990, Clark and Tennenhouse [1] proposed a design framework for introducing new network protocols for the Internet. Since the publication of that position paper, active network design framework [2, 3, 10] has slowly taken shape in the late 1990s. The active network paradigm allows program code and data to be delivered simultaneously on the Internet. Moreover, they may get executed and modified on their ways to their destinations. At the moment, there is a global active network backbone, the ABone, for experiments on active networks. Apart from the immaturity of the executing platform, the primary hindrance on the deployment of active networks on the Internet is more on the commercially related issues. For example, a vendor may hesitate to allow network routers to run some unknown programs that may affect their expected routing performance. As a result, alternatives were proposed to allow active network concept to operate on the Internet, such as the application layer active networking (ALAN) project [4] from the European research community. In the ALAN project, there are active server systems located at different places in the networks and active applications are allowed to run in these servers at the application layer. Another potential approach from the network service provider is to offer active network service as the premium service class in the networks. This service class should provide the best Quality of Service (QoS), and allow the access of computing facility in routers. With this approach, the network service providers can create a new source of income.The research in active networks has been progressing steadily. Since active networks introduce programmability on the Internet, appropriate executing platforms for the active applications to execute should be established. These operating platforms are known as execution environments (EEs) and a few of them have been created, e.g., the Active Signaling Protocol (ASP) [12] and the Active Network Transport System (ANTS) [11]. Hence, different active applications can be implemented to test the active networking concept.With these EEs, some experiments have been carried out to examine the active network concept, for example, the mobile networks [5], web proxies [6], and multicast routers [7]. Active networks introduce a lot of program flexibility and extensibility in networks. Several research groups have proposed various designs of execution environments to offer network computation within routers. Their performance and potential benefits to existing infrastructure are being evaluated [8, 9]. Unfortunately, they seldom concern the interoperability problems when the active networks consist of multiple execution environments. For example, there are three EEs in ABone. Active applications written for one particular EE cannot be operated on other platforms. This introduces another problem of resources partitioning for different EEs to operate. Moreover, there are always some critical network applications that need to run under all network routers, such as collecting information and deploying service at critical points to monitor the networks.In this paper, a framework known as Active Network Socket Programming (ANSP) model is proposed to work with all EEs. It offers the following primary objectives.• One single programming interface is introduced for writing active applications.• Since ANSP offers the programming interface, the design of EE can be made independent of the ANSP.This enables a transparency in developing andenhancing future execution environments.• ANSP addresses the interoperability issues among different execution environments.• Through the design of ANSP, the pros and cons of different EEs will be gained. This may help design abetter EE with improved performance in future.The primary objective of the ANSP is to enable all active applications that are written in ANSP can operate in the ABone testbed . While the proposed ANSP framework is essential in unifying the network environments, we believe that the availability of different environments is beneficial in the development of a better execution environment in future. ANSP is not intended to replace all existing environments, but to enable the studies of new network services which are orthogonal to the designs of execution environments. Therefore, ANSP is designed to be a thin and transparent layer on top of all execution environments. Currently, its deployment relies on automatic code loading with the underlying environments. As a result, the deployment of ANSP at a router is optional and does not require any change to the execution environments.II. D ESIGN I SSUES ON ANSPThe ANSP unifies existing programming interfaces among all EEs. Conceptually, the design of ANSP is similar to the middleware design that offers proper translation mechanisms to different EEs. The provisioning of a unified interface is only one part of the whole ANSP platform. There are many other issues that need to be considered. Apart from translating a set of programming interfaces to other executable calls in different EEs, there are other design issues that should be covered, e.g., • a unified thread library handles thread operations regardless of the thread libraries used in the EEs;• a global soft-store allows information sharing among capsules that may execute over different environmentsat a given router;• a unified addressing scheme used across different environments; more importantly, a routing informationexchange mechanism should be designed across EEs toobtain a global view of the unified networks;• a programming model that should be independent to any programming languages in active networks;• and finally, a translation mechanism to hide the heterogeneity of capsule header structures.A. Heterogeneity in programming modelEach execution environment provides various abstractions for its services and resources in the form of program calls. The model consists of a set of well-defined components, each of them has its own programming interfaces. For the abstractions, capsule-based programming model [10] is the most popular design in active networks. It is used in ANTS [11] and ASP [12], and they are being supported in ABone. Although they are developed based on the same capsule model, their respective components and interfaces are different. Therefore, programs written in one EE cannot run in anther EE. The conceptual views of the programming models in ANTS and ASP are shown in Figure 1.There are three distinct components in ANTS: application, capsule, and execution environment. There exist user interfaces for the active applications at only the source and destination routers. Then the users can specify their customized actions to the networks. According to the program function, the applications send one or more capsules to carry out the operations. Both applications and capsules operate on top of an execution environment that exports an interface to its internal programming resources. Capsule executes its program at each router it has visited. When it arrives at its destination, the application at destination may either reply it with another capsule or presents this arrival event to the user. One drawback with ANTS is that it only allows “bootstrap” application.Figure 1. Programming Models in ASP and ANTS.In contrast, ASP does not limit its users to run “bootstrap” applications. Its program interfaces are different from ANTS, but there are also has three components in ASP: application client, environment, and AAContext. The application client can run on active or non-active host. It can start an active application by simply sending a request message to the EE. The client presents information to users and allows its users to trigger actions at a nearby active router. AAContext is the core of the network service and its specification is divided into two parts. One part specifies its actions at its source and destination routers. Its role is similar to that of the application in ANTS, except that it does not provide a direct interface with the user. The other part defines its actions when it runs inside the active networks and it is similar to the functional behaviors of a capsule in ANTS.In order to deal with the heterogeneity of these two models, ANSP needs to introduce a new set of programming interfaces and map its interfaces and execution model to those within the routers’ EEs.B. Unified Thread LibraryEach execution environment must ensure the isolation of instance executions, so they do not affect each other or accessThe authors appreciate the Nortel Institute for Telecommunications (NIT) at the University of Toronto to allow them to access the computing facilitiesothers’ information. There are various ways to enforce the access control. One simple way is to have one virtual machine for one instance of active applications. This relies on the security design in the virtual machines to isolate services. ANTS is one example that is using this method. Nevertheless, the use of multiple virtual machines requires relatively large amount of resources and may be inefficient in some cases. Therefore, certain environments, such as ASP, allow network services to run within a virtual machine but restrict the use of their services to a limited set of libraries in their packages. For instance, ASP provides its thread library to enforce access control. Because of the differences in these types of thread mechanism, ANSP devises a new thread library to allow uniform accesses to different thread mechanisms.C. Soft-StoreSoft-store allows capsule to insert and retrieve information at a router, thus allowing more than one capsules to exchange information within a network. However, problem arises when a network service can execute under different environments within a router. The problem occurs especially when a network service inserts its soft-store information in one environment and retrieves its data at a later time in another environment at the same router. Due to the fact that execution environments are not allowed to exchange information, the network service cannot retrieve its previous data. Therefore, our ANSP framework needs to take into account of this problem and provides soft-store mechanism that allows universal access of its data at each router.D. Global View of a Unified NetworkWhen an active application is written with ANSP, it can execute on different environment seamlessly. The previously smaller and partitioned networks based on different EEs can now be merging into one large active network. It is then necessary to advise the network topology across the networks. However, different execution environments have different addressing schemes and proprietary routing protocols. In order to merge these partitions together, ANSP must provide a new unified addressing scheme. This new scheme should be interpretable by any environments through appropriate translations with the ANSP. Upon defining the new addressing scheme, a new routing protocol should be designed to operate among environments to exchange topology information. This allows each environment in a network to have a complete view of its network topology.E. Language-Independent ModelExecution environment can be programmed in any programming language. One of the most commonly used languages is Java [13] due to its dynamic code loading capability. In fact, both ANTS and ASP are developed in Java. Nevertheless, the active network architecture shown in Figure 2 does not restrict the use of additional environments that are developed in other languages. For instance, the active network daemon, anted, in Abone provides a workspace to execute multiple execution environments within a router. PLAN, for example, is implemented in Ocaml that will be deployable on ABone in future. Although the current active network is designed to deploy multiple environments that can be in any programming languages, there lacks the tool to allow active applications to run seamlessly upon these environments. Hence, one of the issues that ANSP needs to address is to design a programming model that can work with different programming languages. Although our current prototype only considers ANTS and ASP in its design, PLAN will be the next target to address the programming language issue and to improve the design of ANSP.Figure 2. ANSP Framework Model.F. Heterogeneity of Capsule Header StructureThe structures of the capsule headers are different in different EEs. They carries capsule-related information, for example, the capsule types, sources and destinations. This information is important when certain decision needs to be made within its target environment. A unified model should allow its program code to be executed on different environments. However, the capsule header prevents different environments to interpret its information successfully. Therefore, ANSP should carry out appropriate translation to the header information before the target environment receives this capsule.III. ANSP P ROGRAMMING M ODELWe have outlined the design issues encountered with the ANSP. In the following, the design of the programming model in ANSP will be discussed. This proposed framework provides a set of unified programming interfaces that allows active applications to work on all execution environments. The framework is shown in Figure 2. It is composed of two layers integrated within the active network architecture. These two layers can operate independently without the other layer. The upper layer provides a unified programming model to active applications. The lower layer provides appropriate translation procedure to the ANSP applications when it is processed by different environments. This service is necessary because each environment has its own header definition.The ANSP framework provides a set of programming calls which are abstractions of ANSP services and resources. A capsule-based model is used for ANSP, and it is currently extended to map to other capsule-based models used in ANTSand ASP. The mapping possibility to other models remains as our future works. Hence, the mapping technique in ANSP allows any ANSP applications to access the same programming resources in different environments through a single set of interfaces. The mapping has to be done in a consistent and transparent manner. Therefore, the ANSP appears as an execution environment that provides a complete set of functionalities to active applications. While in fact, it is an overlay structure that makes use of the services provided from the underlying environments. In the following, the high-level functional descriptions of the ANSP model are described. Then, the implementations will be discussed. The ANSP programming model is based upon the interactions between four components: application client , application stub , capsule , and active service base.Figure 3. Information Flow with the ANSP.•Application Client : In a typical scenario, an active application requires some means to present information to its users, e.g., the state of the networks. A graphical user interface (GUI) is designed to operate with the application client if the ANSP runs on a non-active host.•Application Stub : When an application starts, it activates the application client to create a new instance of application stub at its near-by active node. There are two responsibilities for the application stub. One of them is to receive users’ instructions from the application client. Another one is to receive incoming capsules from networks and to perform appropriate actions. Typically, there are two types of actions, thatare, to reply or relay in capsules through the networks, or to notify the users regarding the incoming capsule. •Capsule : An active application may contain several capsule types. Each of them carries program code (also referred to as forwarding routine). Since the application defines a protocol to specify the interactions among capsules as well as the application stubs. Every capsule executes its forwarding routine at each router it visits along the path between the source and destination.•Active Service Base : An active service base is designed to export routers’ environments’ services and execute program calls from application stubs and capsules from different EEs. The base is loaded automatically at each router whenever a capsule arrives.The interactions among components within ANSP are shown in Figure 3. The designs of some key components in the ANSP will be discussed in the following subsections. A. Capsule (ANSPCapsule)ANSPXdr decode () ANSPXdr encode () int length ()Boolean execute ()New types of capsule are created by extending the abstract class ANSPCapsule . New extensions are required to define their own forwarding routines as well as their serialization procedures. These methods are indicated below:The execution of a capsule in ANSP is listed below. It is similar to the process in ANTS.1. A capsule is in serial binary representation before it issent to the network. When an active router receives a byte sequence, it invokes decode() to convert the sequence into a capsule. 2. The router invokes the forwarding routine of thecapsule, execute(). 3. When the capsule has finished its job and forwardsitself to its next hop by calling send(), this call implicitly invokes encode() to convert the capsule into a new serial byte representation. length() isused inside the call of encode() to determine the length of the resulting byte sequence. ANSP provides a XDR library called ANSPXdr to ease the jobs of encoding and decoding.B. Active Service Base (ANSPBase)In an active node, the Active Service Base provides a unified interface to export the available resources in EEs for the rest of the ANSP components. The services may include thread management, node query, and soft-store operation, as shown in Table 1.TABLE I. ACTIVE SERVICE BASE FUNCTION CALLSFunction Definition Descriptionboolean send (Capsule, Address) Transmit a capsule towards its destination using the routing table of theunderlying environment.ANSPAddress getLocalHost () Return address of the local host as an ANSPAddress structure. This isuseful when a capsule wants to check its current location.boolean isLocal (ANSPAddress) Return true if its input argument matches the local host’s address andreturn false otherwise.createThread () Create a new thread that is a class ofANSPThreadInterface (discussed later in Section VIA “Unified Thread Abstraction”).putSStore (key, Object) Object getSStore (key) removeSStore (key)The soft-store operations are provided by putSStore(), getSSTore(), and removeSStore(), and they put, retrieve, and remove data respectively. forName (PathName) Supported in ANSP to retrieve a classobject corresponding to the given path name in its argument. This code retrieval may rely on the code loading mechanism in the environment whennecessary.C. Application Client (ANSPClient)boolean start (args[])boolean start (args[],runningEEs) boolean start (args[],startClient)boolean start (args[],startClient, runningEE)Application Client is an interface between users and the nearby active source router. It does the following responsibilities.1. Code registration: It may be necessary to specify thelocation and name of the application code in some execution environments, e.g., ANTS. 2. Application initialization: It includes selecting anexecution environment to execute the application among those are available at the source router. Each active application can create an application client instance by extending the abstract class, ANSPClient . The extension inherits a method, start(), to automatically handle both the registration and initialization processes. All overloaded versions of start() accept a list of arguments, args , that are passed to the application stub during its initialization. An optional argument called runningEEs allows an application client to select a particular set of environment variables, specified by a list of standardized numerical environment ID, the ANEP ID, to perform code registration. If this argument is not specified, the default setting can only include ANTS and ASP. D. Application Stub (ANSPApplication)receive (ANSPCapsule)Application stubs reside at the source and destination routers to initialize the ANSP application after the application clients complete the initialization and registration processes. It is responsible for receiving and serving capsules from the networks as well as actions requested from the clients. A new instance is created by extending the application client abstract class, ANSPApplication . This extension includes the definition of a handling routine called receive(), which is invoked when a stub receives a new capsule.IV. ANSP E XAMPLE : T RACE -R OUTEA testbed has been created to verify the design correctnessof ANSP in heterogeneous environments. There are three types of router setting on this testbed:1. Router that contains ANTS and a ANSP daemonrunning on behalf of ASP; 2. Router that contains ASP and a ANSP daemon thatruns on behalf of ANTS; 3. Router that contains both ASP and ANTS.The prototype is written in Java [11] with a traceroute testing program. The program records the execution environments of all intermediate routers that it has visited between the source and destination. It also measures the RTT between them. Figure 4 shows the GUI from the application client, and it finds three execution environments along the path: ASP, ANTS, and ASP. The execution sequence of the traceroute program is shown in Figure 5.Figure 4. The GUI for the TRACEROUTE Program.The TraceCapsule program code is created byextending the ANSPCapsule abstract class. When execute() starts, it checks the Boolean value of returning to determine if it is returning from the destination. It is set to true if TraceCapsule is traveling back to the source router; otherwise it is false . When traveling towards the destination, TraceCapsule keeps track of the environments and addresses of the routers it has visited in two arrays, path and trace , respectively. When it arrives at a new router, it calls addHop() to append the router address and its environment to these two arrays. When it finally arrives at the destination, it sets returning to false and forwards itself back to the source by calling send().When it returns to source, it invokes deliverToApp() to deliver itself to the application stub that has been running at the source. TraceCapsule carries information in its data field through the networks by executing encode() and decode(), which encapsulates and de-capsulates its data using External Data Representation (XDR) respectively. The syntax of ANSP XDR follows the syntax of XDR library from ANTS. length() in TraceCapsule returns the data length, or it can be calculated by using the primitive types in the XDRlibrary.Figure 5. Flow of the TRACEROUTE Capsules.V. C ONCLUSIONSIn this paper, we present a new unified layered architecture for active networks. The new model is known as Active Network Socket Programming (ANSP). It allows each active application to be written once and run on multiple environments in active networks. Our experiments successfully verify the design of ANSP architecture, and it has been successfully deployed to work harmoniously with ANTS and ASP without making any changes to their architectures. In fact, the unified programming interface layer is light-weighted and can be dynamically deployable upon request.R EFERENCES[1] D.D. Clark, D.L. Tennenhouse, “Architectural Considerations for a NewGeneration of Protocols,” in Proc. ACM Sigcomm’90, pp.200-208, 1990. [2] D. Tennenhouse, J. M. Smith, W. D. Sicoskie, D. J. Wetherall, and G. J.Minden, “A survey of active network research,” IEEE Communications Magazine , pp. 80-86, Jan 1997.[3] D. Wetherall, U. Legedza, and J. Guttag, “Introducing new internetservices: Why and how,” IEEE Network Magazine, July/August 1998. [4] M. Fry, A. Ghosh, “Application Layer Active Networking,” in ComputerNetworks , Vol.31, No.7, pp.655-667, 1999.[5] K. W. Chin, “An Investigation into The Application of Active Networksto Mobile Computing Environments”, Curtin University of Technology, March 2000.[6] S. Bhattacharjee, K. L. Calvert, and E. W. Zegura, “Self OrganizingWide-Area Network Caches”, Proc. IEEE INFOCOM ’98, San Francisco, CA, 29 March-2 April 1998.[7] L. H. Leman, S. J. Garland, and D. L. Tennenhouse, “Active ReliableMulticast”, Proc. IEEE INFOCOM ’98, San Francisco, CA, 29 March-2 April 1998.[8] D. Descasper, G. Parulkar, B. Plattner, “A Scalable, High PerformanceActive Network Node”, In IEEE Network, January/February 1999.[9] E. L. Nygren, S. J. Garland, and M. F. Kaashoek, “PAN: a high-performance active network node supporting multiple mobile code system”, In the Proceedings of the 2nd IEEE Conference on Open Architectures and Network Programming (OpenArch ’99), March 1999. [10] D. L. Tennenhouse, and D. J. Wetherall. “Towards an Active NetworkArchitecture”, In Proceeding of Multimedia Computing and Networking , January 1996.[11] D. J. Wetherall, J. V. Guttag, D. L. Tennenhouse, “ANTS: A toolkit forBuilding and Dynamically Deploying Network Protocols”, Open Architectures and Network Programming, 1998 IEEE , 1998 , Page(s): 117 –129.[12] B. Braden, A. Cerpa, T. Faber, B. Lindell, G. Phillips, and J. Kann.“Introduction to the ASP Execution Environment”: /active-signal/ARP/index.html .[13] “The java language: A white paper,” Tech. Rep., Sun Microsystems,1998.。
A Comparison of Soft Start Mechanisms for Mining BeltConveyors1800 Washington Road Pittsburgh, PA 15241 Belt Conveyors are an important method for transportation of bulk materials in the mining industry. The control of the application of the starting torque from the belt drive system to the belt fabric affects the performance, life cost, and reliability of the conveyor. This paper examines applications of each starting method within the coal mining industry.INTRODUCTIONThe force required to move a belt conveyor must be transmitted by the drive pulley via friction between the drive pulley and the belt fabric. In order to transmit power there must be a difference in the belt tension as it approaches and leaves the drive pulley. These conditions are true for steady state running, starting, and stopping. Traditionally, belt designs are based on static calculations of running forces. Since starting and stopping are not examined in detail, safety factors are applied to static loadings (Harrison, 1987). This paper will primarily address the starting or acceleration duty of the conveyor. The belt designer must control starting acceleration to prevent excessive tension in the belt fabric and forces in the belt drive system (Suttees, 1986). High acceleration forces can adversely affect the belt fabric, belt splices, drive pulleys, idler pulleys, shafts, bearings, speed reducers, and couplings. Uncontrolled acceleration forces can cause belt conveyor system performance problems with vertical curves, excessive belt take-up movement, loss of drive pulley friction, spillage of materials, and festooning of the belt fabric. The belt designer is confronted with two problems, The belt drive system must produce a minimum torque powerful enough to start the conveyor, and controlled such that the acceleration forces are within safe limits. Smooth starting of the conveyor can be accomplished by the use of drive torque control equipment, either mechanical or electrical, or a combination of the two (CEM, 1979).SOFT START MECHANISM EVALUATION CRITERIONWhat is the best belt conveyor drive system? The answer depends on many variables. The best system is one that provides acceptable control for starting, running, and stopping at a reasonable cost and with high reliability (Lewdly and Sugarcane, 1978). Belt Drive System For the purposes of this paper we will assume that belt conveyors are almost always driven byelectrical prime movers (Goodyear Tire and Rubber, 1982). The belt "drive system" shall consist of multiple components including the electrical prime mover, the electrical motor starter with control system, the motor coupling, the speed reducer, the low speed coupling, the belt drive pulley, and the pulley brake or hold back (Cur, 1986). It is important that the belt designer examine the applicability of each system component to the particular application. For the purpose of this paper, we will assume that all drive system components are located in the fresh air, non-permissible, areas of the mine, or in non-hazardous, National Electrical Code, Article 500 explosion-proof, areas of the surface of the mine.Belt Drive Component Attributes SizeCertain drive components are available and practical in different size ranges. For this discussion, we will assume that belt drive systems range from fractional horsepower to multiples of thousands of horsepower. Small drive systems are often below 50 horsepower. Medium systems range from 50 to 1000 horsepower. Large systems can be considered above 1000 horsepower. Division of sizes into these groups is entirely arbitrary. Care must be taken to resist the temptation to over motor or under motor a belt flight to enhance standardization. An over motored drive results in poor efficiency and the potential for high torques, while an under motored drive could result in destructive overspending on regeneration, or overheating with shortened motor life (Lords, et al., 1978).Torque ControlBelt designers try to limit the starting torque to no more than 150% of the running torque (CEMA, 1979; Goodyear, 1982). The limit on the applied starting torque is often the limit of rating of the belt carcass, belt splice, pulley lagging, or shaft deflections. On larger belts and belts with optimized sized components, torque limits of 110% through 125% are common (Elberton, 1986). In addition to a torque limit, the belt starter may be required to limit torque increments that would stretch belting and cause traveling waves. An ideal starting control system would apply a pretension torque to the belt at rest up to the point of breakaway, or movement of the entire belt, then a torque equal to the movement requirements of the belt with load plus a constant torque to accelerate the inertia of the system components from rest to final running speed. This would minimize system transient forces and belt stretch (Shultz, 1992). Different drive systems exhibit varying ability to control the application of torques to the belt at rest and at different speeds. Also, the conveyor itself exhibits two extremes of loading. An empty belt normally presents the smallest required torque for breakaway and acceleration, while a fully loaded belt presents the highest required torque. A mining drive system must be capable of scaling the applied torque from a 2/1 ratio for a horizontal simple belt arrangement, to a 10/1 ranges for an inclined or complex belt profile.Thermal RatingDuring starting and running, each drive system may dissipate waste heat. The waste heat may be liberated in the electrical motor, the electrical controls,, the couplings, the speed reducer, or the belt braking system. The thermal load of each start Is dependent on the amount of belt load and the duration of the start. The designer must fulfill the application requirements for repeated starts after running the conveyor at full load. Typical mining belt starting duties vary from 3 to 10 starts per hour equally spaced, or 2 to 4 starts in succession. Repeated starting may require the dreading or over sizing of system components. There is a direct relationship between thermal rating for repeated starts and costs. Variable Speed. Some belt drive systems are suitable for controlling the starting torque and speed, but only run at constant speed. Some belt applications would require a drive system capable of running for extended periods at less than full speed. This is useful when the drive load must be shared with other drives, the belt is used as a process feeder for rate control of the conveyed material, the belt speed is optimized for the haulage rate, the belt is used at slower speeds to transport men or materials, or the belt is run a slow inspection or inching speed for maintenance purposes (Hager, 1991). The variable speed belt drive will require a control system based on some algorithm to regulate operating speed. Regeneration or Overhauling Load. Some belt profiles present the potential for overhauling loads where the belt system supplies energy to the drive system. Not all drive systems have the ability to accept regenerated energy from the load. Some drives can accept energy from the load and return it to the power line for use by other loads. Other drives accept energy from the load and dissipate it into designated dynamic or mechanical braking elements. Some belt profiles switch from motoring to regeneration during operation. Can the drive system accept regenerated energy of a certain magnitude for the application? Does the drive system have to control or modulate the amount of retarding force during overhauling? Does the overhauling occur when running and starting? Maintenance and Supporting Systems. Each drive system will require periodic preventative maintenance. Replaceable items would include motor brushes, bearings, brake pads, dissipation resistors, oils, and cooling water. If the drive system is conservatively engineered and operated, the lower stress on consumables will result in lower maintenance costs. Some drives require supporting systems such as circulating oil for lubrication, cooling air or water, environmental dust filtering, or computer instrumentation. The maintenance of the supporting systems can affect the reliability of the drive system.CostThe drive designer will examine the cost of each drive system. The total cost is the sum of the first capital cost to acquire the drive, the cost to install and commission the drive, thecost to operate the drive, and the cost to maintain the drive. The cost for power to operate the drive may vary widely with different locations. The designer strives to meet all system performance requirements at lowest total cost. Often more than one drive system may satisfy all system performance criterions at competitive costs.ComplexityThe preferred drive arrangement is the simplest, such as a single motor driving through a single head pulley.However,mechanical, economic,and functional requirements often necessitate the use of complex drives.The belt designer must balance the need for sophistication against the problems that accompany complex systems. Complex systems require additional design engineering for successful deployment. An often-overlooked cost in a complex system is the cost of training onsite personnel, or the cost of downtime as a result of insufficient training.SOFT START DRIVE CONTROL LOGICEach drive system will require a control system to regulate the starting mechanism. The most common type of control used on smaller to medium sized drives with simple profiles is termed "Open Loop Acceleration Control". In open loop, the control system is previously configured to sequence the starting mechanism in a prescribed manner, usually based on time. In open loop control, drive-operating parameters such as current, torque, or speed do not influence sequence operation. This method presumes that the control designer has adequately modeled drive system performance on the conveyor. For larger or more complex belts, "Closed Loop" or "Feedback" control may he utilized. In closed loop control, during starting, the control system monitors via sensors drive operating parameters such as current level of the motor, speed of the belt, or force on the belt, and modifies the starting sequence to control, limit, or optimize one or wore parameters. Closed loop control systems modify the starting applied force between an empty and fully loaded conveyor. The constants in the mathematical model related to the measured variable versus the system drive response are termed the tuning constants. These constants must be properly adjusted for successful application to each conveyor. The most common schemes for closed loop control of conveyor starts are tachometer feedback for speed control and load cell force or drive force feedback for torque control. On some complex systems, It is desirable to have the closed loop control system adjust itself for various encountered conveyor conditions. This is termed "Adaptive Control". These extremes can involve vast variations in loadings, temperature of the belting, location of the loading on the profile, or multiple drive options on the conveyor. There are three commonadaptive methods. The first involves decisions made before the start, or 'Restart Conditioning'. If the control system could know that the belt is empty, it would reduce initial force and lengthen the application of acceleration force to full speed. If the belt is loaded, the control system would apply pretension forces under stall for less time and supply sufficient torque to adequately accelerate the belt in a timely manner. Since the belt only became loaded during previous running by loading the drive, the average drive current can be sampled when running and retained in a first-in-first-out buffer memory that reflects the belt conveyance time. Then at shutdown the FIFO average may be use4 to precondition some open loop and closed loop set points for the next start. The second method involves decisions that are based on drive observations that occur during initial starting or "Motion Proving'. This usually involves a comparison In time of the drive current or force versus the belt speed. if the drive current or force required early in the sequence is low and motion is initiated, the belt must be unloaded. If the drive current or force required is high and motion is slow in starting, the conveyor must be loaded. This decision can be divided in zones and used to modify the middle and finish of the start sequence control. The third method involves a comparison of the belt speed versus time for this start against historical limits of belt acceleration, or 'Acceleration Envelope Monitoring'. At start, the belt speed is measured versus time. This is compared with two limiting belt speed curves that are retained in control system memory. The first curve profiles the empty belt when accelerated, and the second one the fully loaded belt. Thus, if the current speed versus time is lower than the loaded profile, it may indicate that the belt is overloaded, impeded, or drive malfunction. If the current speed versus time is higher than the empty profile, it may indicate a broken belt, coupling, or drive malfunction. In either case, the current start is aborted and an alarm issued.CONCLUSIONThe best belt starting system is one that provides acceptable performance under all belt load Conditions at a reasonable cost with high reliability. No one starting system meets all needs. The belt designer must define the starting system attributes that are required for each belt. In general, the AC induction motor with full voltage starting is confined to small belts with simple profiles. The AC induction motor with reduced voltage SCR starting is the base case mining starter for underground belts from small to medium sizes. With recent improvements, the AC motor with fixed fill fluid couplings is the base case for medium to large conveyors with simple profiles. The Wound Rotor Induction Motor drive is the traditional choice for medium to large belts with repeated starting duty or complex profilesthat require precise torque control. The DC motor drive, Variable Fill Hydrokinetic drive, and the Variable Mechanical Transmission drive compete for application on belts with extreme profiles or variable speed at running requirements. The choice is dependent on location environment, competitive price, operating energy losses, speed response, and user familiarity. AC Variable Frequency drive and Brush less DC applications are limited to small to medium sized belts that require precise speed control due to higher present costs and complexity. However, with continuing competitive and technical improvements, the use of synthesized waveform electronic drives will expand.REFERENCES[1]Michael L. Nave, P.E.1989.CONSOL Inc.煤矿业带式输送机几种软起动方式的比较1800 年华盛顿路匹兹堡, PA 15241带式运送机是采矿工业运输大批原料的重要方法。
本科生毕业设计(论文)外文翻译外文原文题目:Real-time interactive optical micromanipulation of a mixture of high- and low-index particles中文翻译题目:高低折射率微粒混合物的实时交互式光学微操作毕业设计(论文)题目:阵列光镊软件控制系统设计姓名:任有健学院:生命学院班级:06210501指导教师:李勤高低折射率微粒混合物的实时交互式光学微操作Peter John Rodrigo Vincent Ricardo Daria Jesper Glückstad丹麦罗斯基勒DK-4000号,Risø国家实验室光学和等离子研究系jesper.gluckstad@risoe.dkhttp://www.risoe.dk/ofd/competence/ppo.htm摘要:本文论证一种对于胶体的实时交互式光学微操作的方法,胶体中包含两种折射率的微粒,与悬浮介质(0n )相比,分别低于(0L n n <)、高于(0H n n >)悬浮介质的折射率。
球形的高低折射率微粒在横平板上被一批捕获激光束生成的约束光势能捕获,捕获激光束的横剖面可以分为“礼帽形”和“圆环形”两种光强剖面。
这种应用方法在光学捕获的空间分布和个体几何学方面提供了广泛的可重构性。
我们以实验为基础证实了同时捕获又独立操作悬浮于水(0 1.33n =)中不同尺寸的球形碳酸钠微壳( 1.2L n ≈)和聚苯乙烯微珠( 1.57H n =)的独特性质。
©2004 美国光学学会光学分类与标引体系编码:(140.7010)捕获、(170.4520)光学限制与操作和(230.6120)空间光调制器。
1 引言光带有动量和角动量。
伴随于光与物质相互作用的动量转移为我们提供了在介观量级捕获和操作微粒的方法。
过去数十年中的巨大发展已经导致了在生物和物理领域常规光学捕获的各种应用以及下一代光学微操作体系的出现[1-5]。
Produce the design of the tool and realize automaticallyon the basis of JSP webpageIt is an important respect that Internet uses that Web develops technology, and JSP is the most advanced technology that Web is developed , it is present Web developer's first-selected technology. But because JSP has relatively high expectations for Web developer, a lot of general Web developers can not use this advanced technology . The discussion produces the design of the tool and realizes automatically on the basis of JSP webpage of the template and label storehouse, put forward concrete design philosophy and implementation method .With the popularization of WWW (World Wide Web ), the technology of the dynamic webpage is developed rapidly too. From original CGI (Common Gateway In-terface ) to ASP (Active Server Page ), have met the webpage developer to the demand for developing technology of the dynamic webpage to a certain extent. But no matter CGI or ASP have certain limitation, for instance, consuming to resources of the server of CGI, ASP can only be used etc. with Microsoft IIS, all these have limited scope of application of the technology, have hindered their popularization greatly. The vast page developers all look forward to a kind of unified page and develop technology earnestly, characteristic that this technology there should be:①Have nothing to do with the operating platform, can run on any Web or the application program server ;②Show the logic and page of application program that separates ; ③Offer codes to put in an position, simplify and develop the course based on interactive application program of Web.JSP (Java Server Page ) technology is designed and used for responding to the request that like this. JSP is developed technology by the new webpage that Sun MicroSystem Company put out in June of 1999, it is that Web based on Java Serv-let and the whole Java system develops technology, and Servlet2. Expansion of 1API. Utilize this technology, can set up advancedly , safely and stepping dynamic websites of the platform .Java is the future mainstream to develop technology , have a lot of advantages . JSP is Java important application technology on Internet/Intranet Web , get extensive support and admit, it can conbine with various kinds of Java technology together intactly , thus realize very complicated application.As a kind of technology of development based on text , taking showing as centre, JSP has offered all advantages of Java Servlet. Logic function in order to make sure and showing the function was separated , JSP can already work with JavaBeans , Enterprise JavaBeans (EJB ) and Servlet . The developer of JSP can finish the work that majority and website's logic are correlated with through using JavaBeans , EJB and Servlet , and only assign the work shown to JSP page to finish. Content and show advantage that logic separate lie in , upgrade person , page of appearanceneedn't understand Java code , the personnel upgrading Javas needn't be experts who design webpage either. This can define Web template in JSP page with Javas , in order to set up websites made up of a page with similar appearance. Java completion data offer, have Java code among template, this mean template these can write by one HTML person is it maintain to come.JSP develops technology as the webpage of the mainstream at present, has the following characteristics:(1) Separate the formulation and showing of the content : Using JSP technology, the page developer of Web can use HTML or XML identification to design and format the final page . Use JSP identification or bound foot turn into dynamic content of page actually (whether content according to is it come change to ask). Produce logic of content of the identification and JavaBeans package , truss up of the little script encapsulation, all scripts run in the end of the server. If key logic among identification and JavaBeans, then other people, such as Web administrative staff and page designer encapsulation, can edit and use JSP page , and does not influence the formulation of the content .(2) Emphasize the reusable package : Most JSP pages depend on the reusable one, the package stepping the platform finish more complicated treatment with required application program. Benefitting from the independence of operating platform of Java, the developer can be very convenient to share and exchange and carry out the ordinary package that operated, or make these packages used by more users. The method based on package has accelerated the total development course, the efficiency of improving the project and developing wholly greatly.Though JSP is powerful, it requires the webpage developer should be quite familiar with Java. There are still relatively few Java programmers now, for general webpage developer, the grammar of JSP is more difficult to grasp . So, need a kind of webpage developing instrument and offer commonly used JSP application to general webpage developer, is it understand general page develop developer of technology (HTML ) can use strong function of JSP too only to let.Systematic design object and main technology of use:(1)Design objectSystem this design object for understand but HTML understand general webpage developer of JSP offer a webpage developing instrument at all only, enable them to follow the systematic file, use the daily function of JSP through the label, produce one finally and only include static HTML and dynamic JSP webpage of JSP label.(2)Main technologyThis system is in the design, consider using the technology of the template and JSP label to realize mainly.1、Technology of the templateThe technology of the template is widely applied to various kinds of development and application system. It produces some commonly used frame structure in advance , uses the family to choose the template from the template storehouse conveniently according to the needs of one's own one, is it is it put up to go again by oneself to need , save construction period in user , facilitate use of user. In this system , classify the page according to the function type , sum up the commonly used page type, produce the template storehouse.2、Storehouse technology of the labelIn JSP, movements can create and visit the language target of the procedure and influence the element exported and flowed. JSP has defined six standard movements. Except six standard movement these, user can define own movement finish the specific function. These movements are known as the customer movement, they are the reusable procedure module . Through movement these, programmer can some encapsulation stand up too display function of page in JSP page, make the whole page more succinct and easier to maintain. In a JSP page, movements were transfered through the customer label in these customers. And the label storehouse (Tag Library ) is the set of the customer label.JSP label storehouse is that one kind produces the method based on script of XML through JavaBeans. It is one of the greatest characteristics of JSP. Through the label storehouse , can expand JSP application unrestrictedly , finish any complicated application demand.JSP label storehouse has the following characteristic:①Easy to use: The labels in JSP and general HTML marks are totally the same in appearance, it is as convenient as ordinary HTML mark to use.②The easy code is paid most attention to: Every label in the label storehouse can finish certain function . Define ready to eat one label storehouse , is it pack one Jar file the label storehouse to need only, then only need use this label storehouse in other systems afterwards, needn't develop codes again , has raised the system and developed efficiency greatly, have reduced the development cost.③The easy code is safeguarded: All application logic is encapsulated in label processor and JavaBeans, all labels concentrate on a label storehouse. If need to upgrade codes or need to revise the function on a webpage, only need to revise the corresponding label. Maintain way in unison through this kind , it is unnecessary in each webpage is it is it fix to act as to get onning, have reduce the work load safeguarded greatly, has economized the cost of safeguarding.④The easy system is expanded : If need to add the new function to the system , only need to define a new label to finish this function, do not need to do any change to other respects of thesystem. Can inherit JSP normal characteristics of various fields in the label storehouse. Can expand and increase the function of JSP unrestrictedly like this, and does not need to wait for the appearance of the next edition JSP .Systematic composition and realizing:(1)The system making upThis system is made up of four parts mainly:1、The database joins some: This system supports several daily databases , including Oracle, Sybase, MSSQLServer, MySQL and DB2, use JDBC and database to link to each other according to database type and database name , user name , password that users offer that users choose.2、The basic form of system produces some: After joining with the database , produce the basic form TC-Tables and TC-Columns of two systems according to the user name linking to each other with the database , TC-Tables form includes English name , Chinese name and some attribute of form belonging to this user in this database , for instance can revise , can inquire about ; The Chinese and English name of the row and some other attribute that TC-Columns form includes belonging to all forms of this user's in this database . For instance can show , can inquire about . Basic information of the database that these basic forms of two systems provide to user's institute for use in the course of development of the whole system.3、The template is chosen to produce some with the webpage: This part is a key part of a system. It includes two pieces of sub module .①The template is chosen some: The system offers the template to user and chooses the interface, let users choose the templates used from the template storehouse according to the need.②The template is dealt with some: According to template that user choose, system transfer designated template deal with module is it punish to go on to these template. When dealing with the label that the procedure meets in the template, offer the mutual interface to user, let user input parameter for designated label , prove system validity of label that user input. Finished the formulation of JSP page systematically finally.Webpage preview is with revising some: After the webpage was produced out, the system has offered a webpage preview window and code to user and looked over that revises the window. Through this preview window, users can look at the result of JSP page produced out in advance . If user static result of respect in page very satisfied, user can through code look over revise window revise HTML code of code. If users have further demands for the static result of the page, the system has also offered a piece of interface which transfers DreamWeaver editing machine to user, users can use it to carry on further modification and perfection to the static result of JSP page that is produced out .(2)Systematic realization1、Realization of the template storehouse and label storehouseThe planning and design of the label storehouse are essential in the whole system design, efficiency that the degree and system that are put in an position have operated that its relation has reached codes. Its planning should follow the following principle .(1) Should try one's best little including static HTML among label. To general user, the label is transparent. Users can not look over and revise labels . If include too many static HT-ML sentence in the label , will influence the modification and perfection of user's static result to the page, limit the use of the label.(2) Try one's best to raise the paying most attention to degree of the code. Is it is it is it is it is it is it get to JSP public JSP out to withdraw to use to try one's best to classify to go on to use, form labels. Do not use and realize this application repeatedly in each label . While revising and perfecting to using like this , only need to revise this label, maintenance of the easy code.(3) Facilitate users' use. While designing the label storehouse , should fully consider users' operating position , it can very easy and understanding and using labels conveniently to use the family.①Definition of the label storehouse: Define a label storehouse, must define a label storehouse and describe the file (TLD ) at first . This is a file of script based on XML, have defined the edition of XML in this file , codes used, the edition , name and definition and parameter of all labels included in this storehouse of the label storehouse of the edition of the label storehouse , JSP used describe, including the name of the label, corresponding Javas of label, description information of the label ,etc..②Realization of the label: One label first special Java type, this each must inherit TagSupports , this each is in javax. servlet. jsp. Define in tagext bag . In the labels, the parameter which includes this label initializes the subject treatment method (Handler ) of method (Set/Get ) , label and method available for making the first class label to adjust,etc..③Realization of the template : A template is that one contains JSP file that labels quoted . In order to quote the labels defined in the template , must introduce the label storehouse at first .<%@taglib uri=“tag.tld”prefix=“ctag”%>Among them uri appoints the label storehouse to describe the route of the file ; Prefixes used when prefix appoints to quote labels.While quoting the designated label in the template , use the designated prefix while introducing the label storehouse, appoint the name of the label; It is the parameter assignment of the label.2、Systematic development environmentWhat this systematic subject procedure making is used is JBuilder 6 of Borland Company. 0, it is Front-Page2000 of Microsoft Company that the template is developed and used, what the label storehouse is developed and used is UltraEdit editing machine, what JDK is adopted is JDK1.4. The system testing environment is JRun3. 0.Java future mainstream to develop language, and Java using JSP will become major technology that Web will be developed in the future too mainly at Web. This system has adopted the label storehouse , one of the biggest characteristics of JSP, enable the general Web developer to use JSP strong dynamic page function conveniently too, develop JSP dynamic Web page of the modern techniques. Because this system adopts Java to develop, can run under the operating system of any support graphic interface , have realized complete having nothing to do with the platform. This system is easy to expand and perfect. Can consider offering the interface to user afterwards , will use the family to expand the template storehouse and label storehouse by oneself, strengthen the systematic function further.List of references:[1] Cay S. Horstmann,Gary Cornell. Java 2 key technology (CoreJava 2 ) [M ]. Beijing: Publishing house of the mechanical industry.[2] Bruce Eckel. Java programming thought (Thinking in Java ) [M ]. Beijing: Publishing house of the mechanical industry.[3] Joseph L. Weber. Java 2 programming is explained in detail (Using Java 2) [M ]. Beijing: Electronic Industry Press.[4] Borland Company. Building Applications with JBuilder.基于JSP网页自动生成工具的设计与实现Web开发技术是Internet应用的一个重要方面,而JSP又是Web开发的最先进的技术,是当前Web开发人员的首选技术。
The effects of surface preparation on the fracture behaviorof ECC/concrete repair systemToshiro Kamada a,*, Victor C. Li ba Department of Civil Engineering, Gifu University, Yanagido, Gifu 501-1193, Japanb Advanced Civil Engineering Materials Research Laboratory, Department of Civil and Environmental Engineering,University of Michigan, Ann Arbor, Michigan, MI 48109-2125, USAReceived 7 July 1999; accepted 15 May 2000AbstractThis paper presents the influence of surface preparation on the kink-crack trapping mechanism of engineered cementitious composite (ECC)/concrete repair system. In general,surface preparation of the substrate concrete is considered essential to achieve a durable repair. In this experiment, the ``smooth surface'' system showed more desirable behavior in the crack pattern and the crack widths than the ``rough surface'' system. This demonstrates that the smooth surface system is preferable to the rough surface system, from the view point of obtaining durable repair structure. The special phenomenon of kink-crack trapping which prevents the typical failure modes of delamination or spalling in repaired systems is best revealed when the substrate concrete is prepared to have a smooth surface prior to repair. This is in contrast to the standard approach when the substrate concrete is deliberately roughened to create better bonding to the new concrete. Ó 2000 Elsevier Science Ltd. All rights reserved.Keywords: ECC repair system; Kink-crack trapping mechanism; Surface preparation; Durable repair1. IntroductionEngineered cementitious composites (ECCs) [1,2] are high performance fiber-reinforced cement based composite materials designed with micromechanical principles. Micromechanical parameters associated with fiber, matrix and interface are combined to satisfy a pair of criteria, the first crack stress criterion and steady state cracking criterion [3] to achieve the strain hardening behavior. Micromechanics allows optimization of the composite for high performance while minimizing the amount of reinforcing fibers (generally less than 2-3%). ECC has a tensile strain capacity of up to 6% and exhibits pseudo-strain hardening behavior accompanied by multiple cracking. It also has high ultimate tensile strength (5-10 MPa), modulus of rupture (8-25 MPa), fracture toughness (25-30 kJ/m2) and compressive strength (up to 80 MPa) and strain (0.6%). A typical tensile stress-strain curve is shown in Fig. 1. ECC has its uniqueness not only in superior mechanical properties in tension or in relatively small amount of chopped fiber usage but also in micromechanical methodology in material design.The use of ECC for concrete repair was proposed by Li et al. [4], and Lim and Li [5]. In these experiments, specimens representative of an actual repair system - bonded overlay of a concrete pavement above a joint, were used. It was shown that the common failure phenomenona of spalling or delamination in repaired concrete systems were eliminated. Instead, microcracks emanated from the tips of defects on the ECC/concrete interface, kinked into and subsequently were arrested in the ECC material (see Fig. 2, [5]). The tendency for the interface crack to kink into the ECC material depends on the competing driving force for crack extension at differentorientations, and on the competing crack extension resistance along the interface and into the ECC material. A low initial toughness of ECC combined with a high Mode II loading configuration tends to favor kinking. However, if the toughness of ECC remains low after crack kinking, this crack will propagate unstably to the surface, forming a surface spall. This is the typically observed phenomenon associated with brittle concrete and even fiber-reinforced concrete (FRC). In the case of ECC, the kinked crack is trapped or arrested in the ECC material, due to the rapidly rising toughness of the ECC material. Conceptually, the ECC behaves like a material with strongR-curve behavior, with low initial toughness similar to that of cement (0.01 kJ/m2) and high plateau toughness (25-30 kJ/m2). After kinked crack arrest, additional load can drive further crack extension into the interface, followed by subsequent kinking and arrest.Details of the energetics of kink-crack trapping mechanism can be found in [5]. It was pointed out that this kink-crack trapping mechanism could serve as a means for enhancing repaired concrete system durability.In standard concrete repair, surface preparation of the substrate concrete is considered critical in achieving a durable repair [6]. In the study of Lim and Li [5], the ECC is cast onto a diamond saw cut surface of the concrete. Hence, the concrete surface is smooth and is expected as a result to produce a low toughness interface. Higher interface roughness has been associated with higher interface toughness in bi-material systems [7].In this paper, this particular aspect of the influence of surface preparation on the kink-crack trapping phenomenon is investigated. Specifically, the base concrete surfaces were prepared by three different methods. The first surface was obtained as cut surface by using a diamond saw (smooth surface), similar to that used in the previous study [5]. The second one was obtained by applying a lubricant on the smooth surface of the concrete to decrease the bond between the base concrete and the repair material. This surface was applied only in one test case to examine the effect of weak bond of interface on the fracture behavior of the repaired specimen. The third surface was prepared with a portable scarifier to produce a roughened surface (rough surface) from a diamond saw-cut surface.Regarding the repair materials, the water/cement ratio of ECC was varied to control its toughness and strength. Thus, two different mixtures of ECC were used for the comparison of fracture behavior in both smooth and rough surface case. Concrete and steel fiber-reinforced concrete (SFRC) were also used as control repair materials instead of ECC.2. Experimental procedure2.1. Specimens and test methodsThe specimens in this experiment were designed to induce a defect in the form of aninterfacial crack between the repair material and the base concrete, as well as a joint in the substrate. Fig. 3 shows the dimensions of the designed specimen and the loading configuration, and these were the same as those of the previous experiment [5]. This loading condition can provide a stable interface crack propagation condition, when the crack propagates along the interface [8].In this experiment, concrete, SFRC and ECC (with two different W/C ratios) were used as therepair materials. Table 1 illustrates the combinations of the repair material and the surface condition of test specimens. The numbers of specimens are also shown in Table 1. Only in the concrete overlay specimens, a special case where lubricant was smeared on the concrete smooth surface was used.The mix proportions of materials are shown in Table 2. Ordinary mixture proportions were adopted in concrete and SFRC as controls for comparisons with ECC overlay specimens. The steel fiber for SFRC was ``I.S fiber'', straight with indented surface and rectangular cross-section (0.5* 0.5 mm2), 30 mm in length. An investigation using a steel fiber with hooked ends had already been performed in the previous study [5]. Polyethylene fiber (Trade name Spectra 900) with 19 mm length and 0.038 mm diameter was used for ECC. The elastic modulus, the tensile strength and the fiber density of Spectra 900 were 120 GPa, 2700 MPa and 0.98 g/cm3, respectively. Two different ECCs were used with different water/cement ratios. The mechanical properties of the base concrete and the repair materials are shown in Table 3. The tensile strain capacity of the ECC materials are not measured, but are estimated to be in excess of 3% based on test results of similar materials [2].An MTS machine was used for loading. Load and load point displacement were recorded. The loading rate in this experiment was 0.005 mm/s. After the final failure of specimens, interface crack (extension) lengths were measured at both (left and right) sides of a specimen as the distance from a initial notch tip to a propagated crack tip along the interface between the base concrete and the repair material.2.2. Specimen preparationMost of the specimen preparation procedures followed those of the previous work [5]. The base concrete was prepared by cutting a concrete block (see Fig. 4(a)) into four pieces (see Fig. 4(b)) using a diamond saw. Two out of the four pieces were used for one smooth surface repairspecimen. In order to make a rough surface, a cut surface was roughened uniformly with a scarifier for 30 s. To prepare a repair specimen in the form of an overlay system, a repair material was cast against either the smooth surface or the rough surface of the base concrete blocks (see Fig. 5). Special attention was paid both to maintain cleanliness and to provide adequate moisture on the base concrete surface just before the casting. In two of the concrete overlay specimens, lubricant was sprayed on the smooth surface just before concrete casting. The initial notch and joint were made by applying a smooth tape on the base concrete before casting the repair materials (see Fig. 4(c)).The specimens were cured for 4 weeks in water. Eventually, the base concrete was cured for a total of 8 weeks, and repair materials were cured for 4 weeks in water. The specimens were dried for 24 h before testing.3. Results and discussion3.1. Comparison of the ECC overlay system with the control systemsFig. 6 shows the representative load-deflection curves in each test case. The overall peak load and deflection at peak load are recorded in Table 4. In the ECC overlay system, the deflections at peak load, which reflect the system ductility, are considerably larger than those of both the concrete overlay (about one order of magnitude higher) and the SFRC overlay system (over five times). These results show good agreement with the previous results [5]. Moreover, it is clear fromFig. 6 that the energy absorption capacity in the ECC overlay system is much enhanced when it is compared with the other systems. This significant improvement in ductility and in energy absorption capacity of the ECC overlay system is expected to enhance the durability of repaired structures by resisting brittle failure. The ECC overlay system failed without spalling or delamination of the interface, whereas, both the concrete and SFRC overlay systems failed by spalling in these experiments (Fig. 7).3.2. Influence of surface preparationBoth in the concrete overlay system and the SFRC overlay system, the peak load and the deflection at peak load do not show significant differences between smooth surface specimen and rough surface specimen (Table 4). The typical failure mode for both overlay systems (for smooth surface) is shown in Fig. 7. In the concrete overlay specimen with lubricant on the interface, delamination between repair concrete and substrate occurred first, followed by a kinked crack which propagates unstably to the surface of the repair concrete. On the other hand, in the concrete overlay system without lubricant, the initial interface crack kinked out from the interface into the repair concrete with a sudden load drop, without any interface delamination. The fractured halves of the specimens separated completely in both smooth surface specimens and rough surface specimens. In the SFRC overlay system, the initial interface crack also kinked out into the SFRC and the load decreased gradually in both surface conditions of specimen. In all these repair systems, a single kink-crack always leads to final failure, and the influence of surface preparation is not reflected in the experimental data. Instead, only the fracture behavior of the repair material (concrete versus SFRC) are revealed in the test data. These specimen failures are characterized by a single kinked crack with immediate softening following elastic response.。
软件工程专业毕业设计外文文献翻译1000字本文将就软件工程专业毕业设计的外文文献进行翻译,能够为相关考生提供一定的参考。
外文文献1: Software Engineering Practices in Industry: A Case StudyAbstractThis paper reports a case study of software engineering practices in industry. The study was conducted with a large US software development company that produces software for aerospace and medical applications. The study investigated the company’s software development process, practices, and techniques that lead to the production of quality software. The software engineering practices were identified through a survey questionnaire and a series of interviews with the company’s software development managers, software engineers, and testers. The research found that the company has a well-defined software development process, which is based on the Capability Maturity Model Integration (CMMI). The company follows a set of software engineering practices that ensure quality, reliability, and maintainability of the software products. The findings of this study provide a valuable insight into the software engineering practices used in industry and can be used to guide software engineering education and practice in academia.IntroductionSoftware engineering is the discipline of designing, developing, testing, and maintaining software products. There are a number of software engineering practices that are used in industry to ensure that software products are of high quality, reliable, and maintainable. These practices include software development processes, software configuration management, software testing, requirements engineering, and project management. Software engineeringpractices have evolved over the years as a result of the growth of the software industry and the increasing demands for high-quality software products. The software industry has developed a number of software development models, such as the Capability Maturity Model Integration (CMMI), which provides a framework for software development organizations to improve their software development processes and practices.This paper reports a case study of software engineering practices in industry. The study was conducted with a large US software development company that produces software for aerospace and medical applications. The objective of the study was to identify the software engineering practices used by the company and to investigate how these practices contribute to the production of quality software.Research MethodologyThe case study was conducted with a large US software development company that produces software for aerospace and medical applications. The study was conducted over a period of six months, during which a survey questionnaire was administered to the company’s software development managers, software engineers, and testers. In addition, a series of interviews were conducted with the company’s software development managers, software engineers, and testers to gain a deeper understanding of the software engineering practices used by the company. The survey questionnaire and the interview questions were designed to investigate the software engineering practices used by the company in relation to software development processes, software configuration management, software testing, requirements engineering, and project management.FindingsThe research found that the company has a well-defined software development process, which is based on the Capability Maturity Model Integration (CMMI). The company’s software development process consists of five levels of maturity, starting with an ad hoc process (Level 1) and progressing to a fully defined and optimized process (Level 5). The company has achieved Level 3 maturity in its software development process. The company follows a set of software engineering practices that ensure quality, reliability, and maintainability of the software products. The software engineering practices used by the company include:Software Configuration Management (SCM): The company uses SCM tools to manage software code, documentation, and other artifacts. The company follows a branching and merging strategy to manage changes to the software code.Software Testing: The company has adopted a formal testing approach that includes unit testing, integration testing, system testing, and acceptance testing. The testing process is automated where possible, and the company uses a range of testing tools.Requirements Engineering: The company has a well-defined requirements engineering process, which includes requirements capture, analysis, specification, and validation. The company uses a range of tools, including use case modeling, to capture and analyze requirements.Project Management: The company has a well-defined project management process that includes project planning, scheduling, monitoring, and control. The company uses a range of tools to support project management, including project management software, which is used to track project progress.ConclusionThis paper has reported a case study of software engineering practices in industry. The study was conducted with a large US software development company that produces software for aerospace and medical applications. The study investigated the company’s software development process,practices, and techniques that lead to the production of quality software. The research found that the company has a well-defined software development process, which is based on the Capability Maturity Model Integration (CMMI). The company uses a set of software engineering practices that ensure quality, reliability, and maintainability of the software products. The findings of this study provide a valuable insight into the software engineering practices used in industry and can be used to guide software engineering education and practice in academia.外文文献2: Agile Software Development: Principles, Patterns, and PracticesAbstractAgile software development is a set of values, principles, and practices for developing software. The Agile Manifesto represents the values and principles of the agile approach. The manifesto emphasizes the importance of individuals and interactions, working software, customer collaboration, and responding to change. Agile software development practices include iterative development, test-driven development, continuous integration, and frequent releases. This paper presents an overview of agile software development, including its principles, patterns, and practices. The paper also discusses the benefits and challenges of agile software development.IntroductionAgile software development is a set of values, principles, and practices for developing software. Agile software development is based on the Agile Manifesto, which represents the values and principles of the agile approach. The manifesto emphasizes the importance of individuals and interactions, working software, customer collaboration, and responding to change. Agile software development practices include iterative development, test-driven development, continuous integration, and frequent releases.Agile Software Development PrinciplesAgile software development is based on a set of principles. These principles are:Customer satisfaction through early and continuous delivery of useful software.Welcome changing requirements, even late in development. Agile processes harness change for the customer's competitive advantage.Deliver working software frequently, with a preference for the shorter timescale.Collaboration between the business stakeholders and developers throughout the project.Build projects around motivated individuals. Give them the environment and support they need, and trust them to get the job done.The most efficient and effective method of conveying information to and within a development team is face-to-face conversation.Working software is the primary measure of progress.Agile processes promote sustainable development. The sponsors, developers, and users should be able to maintain a constant pace indefinitely.Continuous attention to technical excellence and good design enhances agility.Simplicity – the art of maximizing the amount of work not done – is essential.The best architectures, requirements, and designs emerge from self-organizing teams.Agile Software Development PatternsAgile software development patterns are reusable solutions to common software development problems. The following are some typical agile software development patterns:The Single Responsibility Principle (SRP)The Open/Closed Principle (OCP)The Liskov Substitution Principle (LSP)The Dependency Inversion Principle (DIP)The Interface Segregation Principle (ISP)The Model-View-Controller (MVC) PatternThe Observer PatternThe Strategy PatternThe Factory Method PatternAgile Software Development PracticesAgile software development practices are a set ofactivities and techniques used in agile software development. The following are some typical agile software development practices:Iterative DevelopmentTest-Driven Development (TDD)Continuous IntegrationRefactoringPair ProgrammingAgile Software Development Benefits and ChallengesAgile software development has many benefits, including:Increased customer satisfactionIncreased qualityIncreased productivityIncreased flexibilityIncreased visibilityReduced riskAgile software development also has some challenges, including:Requires discipline and trainingRequires an experienced teamRequires good communicationRequires a supportive management cultureConclusionAgile software development is a set of values, principles, and practices for developing software. Agile software development is based on the Agile Manifesto, which represents the values and principles of the agile approach. Agile software development practices include iterative development, test-driven development, continuous integration, and frequent releases. Agile software development has many benefits, including increased customer satisfaction, increased quality, increased productivity, increased flexibility, increased visibility, and reduced risk. Agile software development also has some challenges, including the requirement for discipline and training, the requirement for an experienced team, the requirement for good communication, and the requirement for a supportive management culture.。
毕业设计(论文)外文资料翻译系别:专业:班级:姓名:学号:外文出处:附件: 1. 原文; 2。
译文2013年03月附件一:A Rapidly Deployable Manipulator SystemChristiaan J。
J。
Paredis, H. Benjamin Brown,Pradeep K. KhoslaAbstract:A rapidly deployable manipulator system combines the flexibility of reconfigurable modular hardware with modular programming tools,allowing the user to rapidly create a manipulator which is custom-tailored for a given task. This article describes two main aspects of such a system,namely,the Reconfigurable Modular Manipulator System (RMMS)hardware and the corresponding control software。
1 IntroductionRobot manipulators can be easily reprogrammed to perform different tasks, yet the range of tasks that can be performed by a manipulator is limited by mechanicalstructure。
Forexample,a manipulator well-suited for precise movement across the top of a table would probably no be capable of lifting heavy objects in the vertical direction. Therefore,to perform a given task,one needs to choose a manipulator with an appropriate mechanical structure.We propose the concept of a rapidly deployable manipulator system to address the above mentioned shortcomings of fixed configuration manipulators。
Bid Compensation Decision Model for Projectswith Costly Bid PreparationS.Ping Ho,A.M.ASCE 1Abstract:For projects with high bid preparation cost,it is often suggested that the owner should consider paying bid compensation to the most highly ranked unsuccessful bidders to stimulate extra effort or inputs in bid preparation.Whereas the underlying idea of using bid compensation is intuitively sound,there is no theoretical basis or empirical evidence for such suggestion.Because costly bid preparation often implies a larger project scale,the issue of bid compensation strategy is important to practitioners and an interest of study.This paper aims to study the impacts of bid compensation and to develop appropriate bid compensation strategies.Game theory is applied to analyze the behavioral dynamics between competing bidders and project owners.A bid compensation model based on game theoretic analysis is developed in this study.The model provides equilibrium solutions under bid compensation,quantitative formula,and quali-tative implications for the formation of bid compensation strategies.DOI:10.1061/(ASCE )0733-9364(2005)131:2(151)CE Database subject headings:Bids;Project management;Contracts;Decision making;Design/build;Build/Operate/Transfer;Construction industry .IntroductionAn often seen suggestion in practice for projects with high bid preparation cost is that the owner should consider paying bid compensation,also called a stipend or honorarium,to the unsuc-cessful bidders.For example,according to the Design–build Manual of Practice Document Number 201by Design–Build In-stitute of America (DBIA )(1996a ),it is suggested that that “the owner should consider paying a stipend or honorarium to the unsuccessful proposers”because “excessive submittal require-ments without some compensation is abusive to the design–build industry and discourages quality teams from participating.”In another publication by DBIA (1995),it is also stated that “it is strongly recommended that honorariums be offered to the unsuc-cessful proposers”and that “the provision of reasonable compen-sation will encourage the more sought-after design–build teams to apply and,if short listed,to make an extra effort in the prepara-tion of their proposal.”Whereas bid preparation costs depend on project scale,delivery method,and other factors,the cost of pre-paring a proposal is often relatively high in some particular project delivery schemes,such as design–build or build–operate–transfer (BOT )contracting.Plus,costly bid preparation often im-plying a large project scale,the issue of bid compensation strat-egy should be important to practitioners and of great interest of study.Existing research on the procurement process in constructionhas addressed the selection of projects that are appropriate for certain project delivery methods (Molenaar and Songer 1998;Molenaar and Gransberg 2001),the design–build project procure-ment processes (Songer et al.1994;Gransberg and Senadheera 1999;Palaneeswaran and Kumaraswamy 2000),and the BOT project procurement process (United Nations Industrial Develop-ment Organization 1996).However,the bid compensation strat-egy for projects with a relatively high bid preparation cost has not been studied.Among the issues over the bidder’s response to the owner’s procurement or bid compensation strategy,it is in own-er’s interest to understand how the owner can stimulate high-quality inputs or extra effort from the bidder during bid prepara-tion.Whereas the argument for using bid compensation is intuitively sound,there is no theoretical basis or empirical evi-dence for such an argument.Therefore,it is crucial to study under what conditions the bid compensation is effective,and how much compensation is adequate with respect to different bidding situa-tions.This paper focuses on theoretically studying the impacts of bid compensation and tries to develop appropriate compensation strategies for projects with a costly bid preparation.Game theory will be applied to analyze the behavioral dynamics between com-peting bidders.Based on the game theoretic analysis and numeric trials,a bid compensation model is developed.The model pro-vides a quantitative framework,as well as qualitative implica-tions,on bid compensation strategies.Research Methodology:Game TheoryGame theory can be defined as “the study of mathematical models of conflict and cooperation between intelligent rational decision-makers”(Myerson 1991).Among economic theories,game theory has been successfully applied to many important issues such as negotiations,finance,and imperfect markets.Game theory has also been applied to construction management in two areas.Ho (2001)applied game theory to analyze the information asymme-try problem during the procurement of a BOT project and its1Assistant Professor,Dept.of Civil Engineering,National Taiwan Univ.,Taipei 10617,Taiwan.E-mail:spingho@.twNote.Discussion open until July 1,2005.Separate discussions must be submitted for individual papers.To extend the closing date by one month,a written request must be filed with the ASCE Managing Editor.The manuscript for this paper was submitted for review and possible publication on March 5,2003;approved on March 1,2004.This paper is part of the Journal of Construction Engineering and Management ,V ol.131,No.2,February 1,2005.©ASCE,ISSN 0733-9364/2005/2-151–159/$25.00.D o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y N A N J I N G U N I VE R S I T Y OF o n 01/06/14. C o p y r i g h t A S C E . F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .implication in project financing and government policy.Ho and Liu (2004)develop a game theoretic model for analyzing the behavioral dynamics of builders and owners in construction claims.In competitive bidding,the strategic interactions among competing bidders and that between bidders and owners are com-mon,and thus game theory is a natural tool to analyze the prob-lem of concern.A well-known example of a game is the “prisoner’s dilemma”shown in Fig.1.Two suspects are arrested and held in separate cells.If both of them confess,then they will be sentenced to jail for 6years.If neither confesses,each will be sentenced for only 1year.However,if one of them confesses and the other does not,then the honest one will be rewarded by being released (in jail for 0year )and the other will be punished for 9years in jail.Note that in each cell,the first number represents player No.1’s payoff and the second one represents player No.2’s.The prisoner’s dilemma is called a “static game,”in which they act simultaneously;i.e.,each player does not know the other player’s decision before the player makes the decision.If the payoff matrix shown in Fig.1is known to all players,then the payoff matrix is a “common knowledge”to all players and this game is called a game of “complete information.”Note that the players of a game are assumed to be rational;i.e.,to maximize their payoffs.To answer what each prisoner will play/behave in this game,we will introduce the concept of “Nash equilibrium ,”one of the most important concepts in game theory.Nash equilibrium is a set of actions that will be chosen by each player.In a Nash equilib-rium,each player’s strategy should be the best response to the other player’s strategy,and no player wants to deviate from the equilibrium solution.Thus,the equilibrium or solution is “strate-gically stable”or “self-enforcing”(Gibbons 1992).Conversely,a nonequilibrium solution is not stable since at least one of the players can be better off by deviating from the nonequilibrium solution.In the prisoner’s dilemma,only the (confess,confess )solution where both players choose to confess,satisfies the stabil-ity test or requirement of Nash equilibrium.Note that although the (not confess,not confess )solution seems better off for both players compared to Nash equilibrium;however,this solution is unstable since either player can obtain extra benefit by deviating from this solution.Interested readers can refer to Gibbons (1992),Fudenberg and Tirole (1992),and Myerson (1991).Bid Compensation ModelIn this section,the bid compensation model is developed on the basis of game theoretic analysis.The model could help the ownerform bid compensation strategies under various competition situ-ations and project characteristics.Illustrative examples with nu-merical results are given when necessary to show how the model can be used in various scenarios.Assumptions and Model SetupTo perform a game theoretic study,it is critical to make necessary simplifications so that one can focus on the issues of concern and obtain insightful results.Then,the setup of a model will follow.The assumptions made in this model are summarized as follows.Note that these assumptions can be relaxed in future studies for more general purposes.1.Average bidders:The bidders are equally good,in terms oftheir technical and managerial capabilities.Since the design–build and BOT focus on quality issues,the prequalification process imposed during procurement reduces the variation of the quality of bidders.As a result,it is not unreasonable to make the “average bidders”assumption.plete information:If all players consider each other tobe an average bidder as suggested in the first assumption,it is natural to assume that the payoffs of each player in each potential solution are known to all players.3.Bid compensation for the second best bidder:Since DBIA’s(1996b )manual,document number 103,suggests that “the stipend is paid only to the most highly ranked unsuccessful offerors to prevent proposals being submitted simply to ob-tain a stipend,”we shall assume that the bid compensation will be offered to the second best bidder.4.Two levels of efforts:It is assumed that there are two levelsof efforts in preparing a proposal,high and average,denoted by H and A ,respectively.The effort A is defined as the level of effort that does not incur extra cost to improve quality.Contrarily,the effort H is defined as the level of effort that will incur extra cost,denoted as E ,to improve the quality of a proposal,where the improvement is detectable by an effec-tive proposal evaluation system.Typically,the standard of quality would be transformed to the evaluation criteria and their respective weights specified in the Request for Pro-posal.5.Fixed amount of bid compensation,S :The fixed amount canbe expressed by a certain percentage of the average profit,denoted as P ,assumed during the procurement by an average bidder.6.Absorption of extra cost,E :For convenience,it is assumedthat E will not be included in the bid price so that the high effort bidder will win the contract under the price–quality competition,such as best-value approach.This assumption simplifies the tradeoff between quality improvement and bid price increase.Two-Bidder GameIn this game,there are only two qualified bidders.The possible payoffs for each bidder in the game are shown in a normal form in Fig.2.If both bidders choose “H ,”denoted by ͑H ,H ͒,both bidders will have a 50%probability of wining the contract,and at the same time,have another 50%probability of losing the con-tract but being rewarded with the bid compensation,S .As a re-sult,the expected payoffs for the bidders in ͑H ,H ͒solution are ͑S /2+P /2−E ,S /2+P /2−E ͒.Note that the computation of the expected payoff is based on the assumption of the average bidder.Similarly,if the bidders choose ͑A ,A ͒,the expected payoffswillFig.1.Prisoner’s dilemmaD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y N A N J I N G U N I VE R S I T Y OF o n 01/06/14. C o p y r i g h t A S C E . F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .be ͑S /2+P /2,S /2+P /2͒.If the bidders choose ͑H ,A ͒,bidder No.1will have a 100%probability of winning the contract,and thus the expected payoffs are ͑P −E ,S ͒.Similarly,if the bidders choose ͑A ,H ͒,the expected payoffs will be ͑S ,P −E ͒.Payoffs of an n -bidder game can be obtained by the same reasoning.Nash EquilibriumSince the payoffs in each equilibrium are expressed as functions of S ,P ,and E ,instead of a particular number,the model will focus on the conditions for each possible Nash equilibrium of the game.Here,the approach to solving for Nash equilibrium is to find conditions that ensure the stability or self-enforcing require-ment of Nash equilibrium.This technique will be applied throughout this paper.First,check the payoffs of ͑H ,H ͒solution.For bidder No.1or 2not to deviate from this solution,we must haveS /2+P /2−E ϾS →S ϽP −2E͑1͒Therefore,condition (1)guarantees ͑H ,H ͒to be a Nash equilib-rium.Second,check the payoffs of ͑A ,A ͒solution.For bidder No.1or 2not to deviate from ͑A ,A ͒,condition (2)must be satisfiedS /2+P /2ϾP −E →S ϾP −2E͑2͒Thus,condition (2)guarantees ͑A ,A ͒to be a Nash equilibrium.Note that the condition “S =P −2E ”will be ignored since the con-dition can become (1)or (2)by adding or subtracting an infinitely small positive number.Thus,since S must satisfy either condition (1)or condition (2),either ͑H ,H ͒or ͑A ,A ͒must be a unique Nash equilibrium.Third,check the payoffs of ͑H ,A ͒solution.For bid-der No.1not to deviate from H to A ,we must have P −E ϾS /2+P /2;i.e.,S ϽP −2E .For bidder No.2not to deviate from A to H ,we must have S ϾS /2+P /2−E ;i.e.,S ϾP −2E .Since S cannot be greater than and less than P −2E at the same time,͑H ,A ͒solution cannot exist.Similarly,͑A ,H ͒solution cannot exist either.This also confirms the previous conclusion that either ͑H ,H ͒or ͑A ,A ͒must be a unique Nash equilibrium.Impacts of Bid CompensationBid compensation is designed to serve as an incentive to induce bidders to make high effort.Therefore,the concerns of bid com-pensation strategy should focus on whether S can induce high effort and how effective it is.According to the equilibrium solu-tions,the bid compensation decision should depend on the mag-nitude of P −2E or the relative magnitude of E compared to P .If E is relatively small such that P Ͼ2E ,then P −2E will be positive and condition (1)will be satisfied even when S =0.This means that bid compensation is not an incentive for high effort when the extra cost of high effort is relatively low.Moreover,surprisingly,S can be damaging when S is high enough such that S ϾP −2E .On the other hand,if E is relatively large so that P −2E is negative,then condition (2)will always be satisfied since S can-not be negative.In this case,͑A ,A ͒will be a unique Nash equi-librium.In other words,when E is relatively large,it is not in the bidder’s interest to incur extra cost for improving the quality of proposal,and therefore,S cannot provide any incentives for high effort.To summarize,when E is relatively low,it is in the bidder’s interest to make high effort even if there is no bid compensation.When E is relatively high,the bidder will be better off by making average effort.In other words,bid compensation cannot promote extra effort in a two-bidder game,and ironically,bid compensa-tion may discourage high effort if the compensation is too much.Thus,in the two-bidder procurement,the owner should not use bid compensation as an incentive to induce high effort.Three-Bidder GameNash EquilibriumFig.3shows all the combinations of actions and their respective payoffs in a three-bidder game.Similar to the two-bidder game,here the Nash equilibrium can be solved by ensuring the stability of the solution.For equilibrium ͑H ,H ,H ͒,condition (3)must be satisfied for stability requirementS /3+P /3−E Ͼ0→S Ͼ3E −P͑3͒For equilibrium ͑A ,A ,A ͒,condition (4)must be satisfied so that no one has any incentives to choose HS /3+P /3ϾP −E →S Ͼ2P −3E͑4͒In a three-bidder game,it is possible that S will satisfy conditions (3)and (4)at the same time.This is different from the two-bidder game,where S can only satisfy either condition (1)or (2).Thus,there will be two pure strategy Nash equilibria when S satisfies conditions (3)and (4).However,since the payoff of ͑A ,A ,A ͒,S /3+P /3,is greater than the payoff of ͑H ,H ,H ͒,S /3+P /3−E ,for all bidders,the bidder will choose ͑A ,A ,A ͒eventually,pro-vided that a consensus between bidders of making effort A can be reached.The process of reaching such consensus is called “cheap talk,”where the agreement is beneficial to all players,and no player will want to deviate from such an agreement.In the design–build or BOT procurement,it is reasonable to believe that cheap talk can occur.Therefore,as long as condition (4)is satis-fied,͑A ,A ,A ͒will be a unique Nash equilibrium.An important implication is that the cheap talk condition must not be satisfied for any equilibrium solution other than ͑A ,A ,A ͒.In other words,condition (5)must be satisfied for all equilibrium solution except ͑A ,A ,A͒Fig.2.Two-biddergameFig.3.Three-bidder gameD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y N A N J I N G U N I VE R S I T Y OF o n 01/06/14. C o p y r i g h t A S C E . F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .S Ͻ2P −3E ͑5͒Following this result,for ͑H ,H ,H ͒to be unique,conditions (3)and (5)must be satisfied;i.e.,we must have3E −P ϽS Ͻ2P −3E͑6͒Note that by definition S is a non-negative number;thus,if one cannot find a non-negative number to satisfy the equilibrium con-dition,then the respective equilibrium does not exist and the equi-librium condition will be marked as “N/A”in the illustrative fig-ures and tables.Next,check the solution where two bidders make high efforts and one bidder makes average effort,e.g.,͑H ,H ,A ͒.The ex-pected payoffs for ͑H ,H ,A ͒are ͑S /2+P /2−E ,S /2+P /2−E ,0͒.For ͑H ,H ,A ͒to be a Nash equilibrium,S /3+P /3−E Ͻ0must be satisfied so that the bidder with average effort will not deviate from A to H ,S /2+P /2−E ϾS /2must be satisfied so that the bidder with high effort will not deviate from H to A ,and condi-tion (5)must be satisfied as argued previously.The three condi-tions can be rewritten asS Ͻmin ͓3E −P ,2P −3E ͔andP −2E Ͼ0͑7͒Note that because of the average bidder assumption,if ͑H ,H ,A ͒is a Nash equilibrium,then ͑H ,A ,H ͒and ͑A ,H ,H ͒will also be the Nash equilibria.The three Nash equilibria will constitute a so-called mixed strategy Nash equilibrium,denoted by 2H +1A ,where each bidder randomizes actions between H and A with certain probabilities.The concept of mixed strategy Nash equilib-rium shall be explained in more detail in next section.Similarly,we can obtain the requirements for solution 1H +2A ,condition (5)and S /2+P /2−E ϽS /2must be satisfied.The requirements can be reorganized asS Ͻ2P −3EandP −2E Ͻ0͑8͒Note that the conflicting relationship between “P −2E Ͼ0”in condition (7)and “P −2E Ͻ0”in condition (8)seems to show that the two types of Nash equilibria are exclusive.Nevertheless,the only difference between 2H +1A and 1H +2A is that the bidder in 2H +1A equilibrium has a higher probability of playing H ,whereas the bidder in 1H +2A also mixes actions H and A but with lower probability of playing H .From this perspective,the difference between 2H +1A and 1H +2A is not very distinctive.In other words,one should not consider,for example,2H +1A ,to be two bidders playing H and one bidder playing A ;instead,one should consider each bidder to be playing H with higher probabil-ity.Similarly,1H +2A means that the bidder has a lower probabil-ity of playing H ,compared to 2H +1A .Illustrative Example:Effectiveness of Bid Compensation The equilibrium conditions for a three-bidder game is numerically illustrated and shown in Table 1,where P is arbitrarily assumed as 10%for numerical computation purposes and E varies to rep-resent different costs for higher efforts.The “*”in Table 1indi-cates that the zero compensation is the best strategy;i.e.,bid compensation is ineffective in terms of stimulating extra effort.According to the numerical results,Table 1shows that bid com-pensation can promote higher effort only when E is within the range of P /3ϽE ϽP /2,where zero compensation is not neces-sarily the best strategy.The question is that whether it is benefi-cial to the owner by incurring the cost of bid compensation when P /3ϽE ϽP /2.The answer to this question lies in the concept and definition of the mix strategy Nash equilibrium,2H +1A ,as explained previously.Since 2H +1A indicates that each bidderwill play H with significantly higher probability,2H +1A may already be good enough,knowing that we only need one bidder out of three to actually play H .We shall elaborate on this concept later in a more general setting.As a result,if the 2H +1A equilib-rium is good enough,the use of bid compensation in a three-bidder game will not be recommended.Four-Bidder Game and n-Bidder GameNash Equilibrium of Four-Bidder GameThe equilibrium of the four-bidder procurement can also be ob-tained.As the number of bidders increases,the number of poten-tial equilibria increases as well.Due to the length limitation,we shall only show the major equilibria and their conditions,which are derived following the same technique applied previously.The condition for pure strategy equilibrium 4H ,is4E −P ϽS Ͻ3P −4E͑9͒The condition for another pure strategy equilibrium,4A ,isS Ͼ3P −4E͑10͒Other potential equilibria are mainly mixed strategies,such as 3H +1A ,2H +2A ,and 1H +3A ,where the numeric number asso-ciated with H or A represents the number of bidders with effort H or A in a equilibrium.The condition for the 3H +1A equilibrium is3E −P ϽS Ͻmin ͓4E −P ,3P −4E ͔͑11͒For the 2H +2A equilibrium the condition is6E −3P ϽS Ͻmin ͓3E −P ,3P −4E ͔͑12͒The condition for the 1H +3A equilibrium isS Ͻmin ͓6E −3P ,3P −4E ͔͑13͒Illustrative Example of Four-Bidder GameTable 2numerically illustrates the impacts of bid compensation on the four-bidder procurement under different relative magni-tudes of E .When E is very small,bid compensation is not needed for promoting effort H .However,when E grows gradually,bid compensation becomes more effective.As E grows to a larger magnitude,greater than P /2,the 4H equilibrium would become impossible,no matter how large S is.In fact,if S is too large,bidders will be encouraged to take effort A .When E is extremely large,e.g.,E Ͼ0.6P ,the best strategy is to set S =0.The “*”in Table 2also indicates the cases that bid compensation is ineffec-Table pensation Impacts on a Three-Bidder GameEquilibriumE ;P =10%3H 2H +1A 1H +2A 3A E ϽP /3e.g.,E =2%S Ͻ14%*N/A N/N 14%ϽS P /3ϽE ϽP /2e.g.,E =4%2%ϽS Ͻ8%S Ͻ2%N/A 8%ϽS P /2ϽE Ͻ͑2/3͒P e.g.,E =5.5%N/AN/AS Ͻ3.5%*3.5%ϽS͑2/3͒P ϽEe.g.,E =7%N/A N/A N/A Always*Note:*denotes that zero compensation is the best strategy;and N/A =the respective equilibrium does not exist.D o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y N A N J I N G U N I VE R S I T Y OF o n 01/06/14. C o p y r i g h t A S C E . F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .tive.To conclude,in a four-bidder procurement,bid compensation is not effective when E is relatively small or large.Again,similar to the three-bidder game,when bid compensation becomes more effective,it does not mean that offering bid compensation is the best strategy,since more variables need to be considered.Further analysis shall be performed later.Nash Equilibrium of n -Bidder GameIt is desirable to generalize our model to the n -bidder game,al-though only very limited qualified bidders will be involved in most design–build or BOT procurements,since for other project delivery methods it is possible to have many bidders.Interested readers can follow the numerical illustrations for three-and four-bidder games to obtain the numerical solutions of n -bidder game.Here,only analytical equilibrium solutions will be solved.For “nA ”to be the Nash equilibrium,we must have P −E ϽS /n +P /n for bidder A not to deviate.In other words,condition (14)must be satisfiedS Ͼ͑n −1͒P −nE͑14͒Note that condition (14)can be rewritten as S Ͼn ͑P −E ͒−P ,which implies that it is not likely for nA to be the Nash equilib-rium when there are many bidders,unless E is very close to or larger than P .Similar to previous analysis,for “nH ”to be the equilibrium,we must have S /n +P /n −E Ͼ0for stability requirement,and condition (15)for excluding the possibility of cheap talk or nA equilibrium.The condition for the nH equilibrium can be reorga-nized as condition (16).S Ͻ͑n −1͒P −nE ͑15͒nE −P ϽS Ͻ͑n −1͒P −nE͑16͒Note that if E ϽP /n ,condition (16)will always be satisfied and nH will be a unique equilibrium even when S =0.In other words,nH will not be the Nash equilibrium when there are many bidders,unless E is extremely small,i.e.,E ϽP /n .For “aH +͑n −a ͒A ,where 2Ͻa Ͻn ”to be the equilibrium so-lution,we must have S /a +P /a −E Ͼ0for bidder H not to devi-ate,S /͑a +1͒+P /͑a +1͒−E Ͻ0for bidder A not to deviate,and condition (15).These requirements can be rewritten asaE −P ϽS Ͻmin ͓͑a +1͒E −P ,͑n −1͒P −nE ͔͑17͒Similarly,for “2H +͑n −2͒A ,”the stability requirements for bidder H and A are S /͑n −1͒ϽS /2+P /2−E and S /3+P /3−E Ͻ0,re-spectively,and thus the equilibrium condition can be written as ͓͑n −1͒/͑n −3͔͒͑2E −P ͒ϽS Ͻmin ͓3E −P ,͑n −1͒P −nE ͔͑18͒For the “1H +͑n −1͒A ”equilibrium,we must haveS Ͻmin ͕͓͑n −1͒/͑n −3͔͒͑2E −P ͒,͑n −1͒P −nE ͖͑19͒An interesting question is:“What conditions would warrant that the only possible equilibrium of the game is either “1H +͑n −1͒A ”or nA ,no matter how large S is?”A logical response to the question is:when equilibria “aH +͑n −a ͒A ,where a Ͼ2”and equilibrium 2H +͑n −2͒A are not possible solutions.Thus,a suf-ficient condition here is that for any S Ͼ͓͑n −1͒/͑n −3͔͒͑2E −P ͒,the “S Ͻ͑n −1͒P −nE ”is not satisfied.This can be guaranteed if we have͑n −1͒P −nE Ͻ͓͑n −1͒/͑n −3͔͒͑2E −P ͒→E Ͼ͓͑n −1͒/͑n +1͔͒P͑20͒Conditions (19)and (20)show that when E is greater than ͓͑n −1͒/͑n +1͔͒P ,the only possible equilibrium of the game is either 1H +͑n −1͒A or nA ,no matter how large S is.Two important practical implications can be drawn from this finding.First,when n is small in a design–build contract,it is not unusual that E will be greater than ͓͑n −1͒/͑n +1͔͒P ,and in that case,bid compensa-tion cannot help to promote higher effort.For example,for a three-bidder procurement,bid compensation will not be effective when E is greater than ͑2/4͒P .Second,when the number of bidders increases,bid compensation will become more effective since it will be more unlikely that E is greater than ͓͑n −1͒/͑n +1͔͒P .The two implications confirm the previous analyses of two-,three-,and four-bidder game.After the game equilibria and the effective range of bid compensation have been solved,the next important task is to develop the bid compensation strategy with respect to various procurement situations.Table pensation Impacts on a Four-Bidder GameEquilibriumE ;P =10%4H 3H +1A 2H +2A 1H +3A 4A E ϽP /4e.g.,E =2%S Ͻ22%*N/A N/A N/A S Ͼ22%P /4ϽE ϽP /3e.g.,E =3%2%ϽS Ͻ18%S Ͻ2%N/A N/A S Ͼ18%P /3ϽE ϽP /2e.g.,E =4%6%ϽS Ͻ14%2%ϽS Ͻ6%S Ͻ2%N/A S Ͼ14%P /2ϽE Ͻ͑3/5͒P e.g.,E =5.5%N/A 6.5%ϽS Ͻ8%3%ϽS Ͻ6.5%S Ͻ3%S Ͼ8%͑3/5͒P ϽE Ͻ͑3/4͒P e.g.,E =6.5%N/AN/AN/AS Ͻ4%*S Ͼ4%͑3/4͒P ϽEe.g.,E =8%N/A N/A N/A N/AAlways*Note:*denotes that zero compensation is the best strategy;and N/A=respective equilibrium does not exist.D o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y N A N J I N G U N I VE R S I T Y OF o n 01/06/14. C o p y r i g h t A S C E . F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .。
目录介绍: (1)1实验性 (2)1.1污水和活性污泥 (2)1.2实验性设定和过程 (3)1.3测试和监视抽样采取从混杂的醇中过滤 (4)2.结果 (5)2.1泥浆化颗粒化 (5)2.2 EGSB操作流出物的稳定酸碱度 (6)3 .TPD污水的理论演算和讨论 (7)3.1酸平衡和中间转换能力酸碱度 (7)3..2VFA在厌氧过程用二种主要方式的二个主要小组细菌介入降低有机基体 (8)3..3VFA和强碱性平衡强碱性的典型的变异 (8)4.结论 (9)命名原则 (10)参考文献 (10)Introduction (12)1Experimental (14)2 Results (16)3 Theoretical calculation and discussions (19)4 Conclusions (22)recomference: (23)稳定性的膨胀的颗粒状污泥床对涤纶人造丝印染废水的处理摘要涤纶人造丝印染污水(TPD污水),包含平均7.0mg/L对苯二甲酸(技术援助)作为主要碳来源和特性污染物,从属于膨胀的颗粒状污泥床(EGSB)过程。
EGSB过程的稳定由实验室实验首先研究了。
TA电离是影响系统的酸基度平衡的优势的因素。
废水的 TA 的高集中造成充份的缓冲能力使中立脂肪酸 (VFA) 从培养基降格产生而且提供了没有空气而能生活强的系统挥发性基础抵抗 pH 减少到低于6.5 。
挥发性脂肪和不饱和脂肪酸除每小时次于6.35和挥发性脂肪积极从事它的极大值以外几乎没有抑制上去沼气生产。
与颗粒化被激活的污泥一起,有机撤除效率和沼气的生产率逐渐增加了和变得更加稳定。
在启动后,COD撤除效率增加到57%-64%,酸碱度被稳定在范围的7.99~6.04,和沼气的生产率是相对高。
酸碱度污泥颗粒化的,适当的流入物和装载使EGSB过程稳定。
EGSB反应器是稳定的为TPD废水处理。
关键词:膨胀的颗粒状泥床;稳定;绝氧处理;印染污水介绍:为了获得柔韧的和优雅的如丝一样涤纶结构、涤纶本色布总是同碱分解过程被预先处理, NaOH以某一温度和压力涤纶纤维被水解在某种程度上。
毕业设计外文翻译评分标准优秀:外文资料内容与本人毕业设计(论文)内容相关性好,有明显的参考价值;翻译汉字达3000字以上;没有重要误译,忠实原文,准确传达原文内容;遵循翻译的基本原则,能灵活处理一般性翻译技巧和具体句型翻译的关系、概念的直译与意译之间的关系;没有基本的语法错误,用词准确;译文通顺,符合汉语表达习惯;良好:外文资料内容与本人毕业设计(论文)内容相关性较好,有较好的参考价值;翻译汉字达3000字以上;没有重要误译,忠实原文,较准确传达原文内容;遵循翻译的基本原则,能处理一般性翻译技巧和具体句型翻译的关系、概念的直译与意译之间的关系;很少的语法错误,用词较准确;译文较通顺,符合汉语表达习惯;中:外文资料内容与本人毕业设计(论文)内容相关性一般,有一定的参考价值;翻译汉字达3000字以上;没有大的误译,基本忠实原文,基本传达原文内容;遵循翻译的基本原则,能处理一般性翻译技巧和具体句型翻译的关系、概念的直译与意译之间的关系;没有多的语法错误,用词较合理;译文通顺,符合汉语表达习惯;及格:外文资料内容与本人毕业设计(论文)内容相关性一般,参考价值一般;翻译汉字达3000字以上;没有大的误译,基本忠实原文,基本传达原文内容;遵循翻译的基本原则,能适当处理一般性翻译技巧和具体句型翻译的关系、概念的直译与意译之间的关系;语法错误较多,用词较欠合理;译文基本通顺,基本符合汉语表达习惯;不及格:外文资料内容与本人毕业设计(论文)内容相关性差,无参考价值;翻译汉字达不到3000字;存在大的误译,没能忠实原文,不能传达原文内容;语法错误很多,用词较不合理;译文不通顺,大部分不符合汉语表达习惯;多路红外遥控开关的设计课题简介多路遥控开关,有一个遥控接收板,遥控接收板连接多个单通道开关电路,其特征在于单通道开关电路由与门电路、射极跟随器、双稳态电路、继电器电路和电源电路组成。
一种多路遥控开关,包括一个遥控接收板,遥控接收板连接多个单通道开关电路,其特征在于单通道开关电路由与门电路、射极跟随器、双稳态电路、继电器驱动电路和电源电路组成。
外文原文:The Analysis of Cavitation Problems in the Axial Piston Pumpshu WangEaton Corporation,14615 Lone Oak Road,Eden Prairie, MN 55344This paper discusses and analyzes the control volume of a piston bore constrained by the valve plate in axial piston pumps. The vacuum within the piston bore caused by the rise volume needs to be compensated by the flow; otherwise, the low pressure may cause the cavitations and aerations. In the research, the valve plate geometry can be optimized by some analytical limitations to prevent the piston pressure below the vapor pressure. The limitations provide the design guide of the timings and overlap areas between valve plate ports and barrel kidneys to consider the cavitations and aerations. _DOI: 10.1115/1.4002058_Keywords: cavitation , optimization, valve plate, pressure undershoots1 IntroductionIn hydrostatic machines, cavitations mean that cavities or bubbles form in the hydraulic liquid at the low pressure and collapse at the high pressure region, which causes noise, vibration, and less efficiency.Cavitations are undesirable in the pump since the shock waves formed by collapsed may be strong enough to damage components. The hydraulic fluid will vaporize when its pressure becomes too low or when the temperature is too high. In practice, a number of approaches are mostly used to deal with the problems: (1) raise the liquid level in the tank, (2) pressurize the tank, (3) booster the inlet pressure of the pump, (4) lower the pumping fluid temperature, and (5) design deliberately the pump itself.Many research efforts have been made on cavitation phenomena in hydraulic machine designs. The cavitation is classified into two types in piston pumps: trapping phenomenon related one (which can be preventedby the proper design of the valve plate) and the one observed on the layers after the contraction or enlargement of flow passages (caused by rotating group designs) in Ref. (1). The relationship between the cavitation and the measured cylinder pressure is addressed in this study. Edge and Darling (2) reported an experimental study of the cylinder pressure within an axial piston pump. The inclusion of fluid momentum effects and cavitations within the cylinder bore are predicted at both high speed and high load conditions. Another study in Ref. (3) provides an overview of hydraulic fluid impacting on the inlet condition and cavitation potential. It indicates that physical properties (such as vapor pressure, viscosity, density, and bulk modulus) are vital to properly evaluate the effects on lubrication and cavitation. A homogeneous cavitation model based on the thermodynamic properties of the liquid and steam is used to understand the basic physical phenomena of mass flow reduction and wave motion influences in the hydraulic tools and injection systems (4). Dular et al. (5, 6) developed an expert system for monitoring and control of cavitations in hydraulic machines and investigated the possibility of cavitation erosion by using the computational fluid dynamics (CFD) tools. The erosion effects of cavitations have been measured and validated by a simple single hydrofoil configuration in a cavitation tunnel. It is assumed that the severe erosion is often due to the repeated collapse of the traveling vortex generated by a leading edge cavity in Ref. (7). Then, the cavitation erosion intensity may be scaled by a simple set of flow parameters: the upstream velocity, the Strouhal number, the cavity length, and the pressure. A new cavitation erosion device, called vortex cavitation generator, is introduced to comparatively study various erosion situations (8).More previous research has been concentrated on the valve plate designs, piston, and pump pressure dynamics that can be associated with cavitations in axial piston pumps. The control volume approach and instantaneous flows (leakage) are profoundly studied in Ref. [9]. Berta et al. [10] used the finite volume concept to develop a mathematical model in which the effects of port plate relief grooves have been modeled andthe gaseous cavitation is considered in a simplified manner. An improved model is proposed in Ref. [11] and validated by experimental results. The model may analyze the cylinder pressure and flow ripples influenced by port plate and relief groove design. Manring compared principal advantages of various valve plate slots (i.e., the slots with constant, linearly varying, and quadratic varying areas) in axial piston pumps [12]. Four different numerical models are focused on the characteristics of hydraulic fluid, and cavitations are taken into account in different ways to assist the reduction in flow oscillations [13].The experiences of piston pump developments show that the optimization of the cavitations/aerations shall include the following issues: occurring cavitation and air release, pump acoustics caused by the induced noises, maximal amplitudes of pressure fluctuations, rotational torque progression, etc. However, the aim of this study is to modify the valve plate design to prevent cavitation erosions caused by collapsing steam or air bubbles on the walls of axial pump components. In contrastto literature studies, the research focuses on the development of analytical relationship between the valve plate geometrics and cavitations. The optimization method is applied to analyze the pressure undershoots compared with the saturated vapor pressure within the piston bore.The appropriate design of instantaneous flow areas between the valveplate and barrel kidney can be decided consequently.2 The Axial Piston Pump and Valve PlateThe typical schematic of the design of the axis piston pump is shown in Fig. 1. The shaft offset e is designed in this case to generate stroking containment moments for reducing cost purposes.The variation between the pivot center of the slipper and swash rotating center is shown as a. The swash angle αis the variable that determines the amount of fluid pumped per shaft revolution. In Fig. 1, the n th piston-slipper assembly is located at the angle ofθ. The displacement of the n thnpiston-slipper assembly along the x-axis can be written asx n= R tan(α)sin(θ)+ a sec(α)+ e tan(α) (1)nwhere R is the pitch radius of the rotating group.Then, the instantaneous velocity of the n th piston isx˙n = R 2sec ()αsin (n θ)α+ R tan (α)cos (n θ)ω+ R 2sec ()αsin (α)α + e 2sec ()αα (2)where the shaft rotating speed of the pump is ω=d n θ / dt .The valve plate is the most significant device to constraint flow inpiston pumps. The geometry of intake/discharge ports on the valve plateand its instantaneous relative positions with respect to barrel kidneys areusually referred to the valve plate timing. The ports of the valve plateoverlap with each barrel kidneys to construct a flow area or passage,which confines the fluid dynamics of the pump. In Fig. 2, the timingangles of the discharge and intake ports on the valve plate are listed as(,)T i d δ and (,)B i d δ. The opening angle of the barrel kidney is referred to asϕ. In some designs, there exists a simultaneous overlap between thebarrel kidney and intake/discharge slots at the locations of the top deadcenter (TDC) or bottom dead center (BDC) on the valve plate on whichthe overlap area appears together referred to as “cross -porting” in thepump design engineering. The cross-porting communicates the dischargeand intake ports, which may usually lower the volumetric efficiency. Thetrapped-volume design is compared with the design of the cross-porting,and it can achieve better efficiency 14]. However, the cross-porting isFig. 1 The typical axis piston pumpcommonly used to benefit the noise issue and pump stability in practice.3 The Control Volume of a Piston BoreIn the piston pump, the fluid within one piston is embraced by the piston bore, cylinder barrel, slipper, valve plate, and swash plate shown in Fig. 3. There exist some types of slip flow by virtue of relativeFig. 2 Timing of the valve platemotions and clearances between thos e components. Within the control volume of each piston bore, the instantaneous mass is calculated asM= n V(3)nwhere ρ and n V are the instantaneous density and volumesuch that themass time rate of change can be given asFig. 3 The control volume of the piston boren n n dM dV d V dt dt dtρρ=+ (4) where d n V is the varying of the volume.Based on the conservation equation, the mass rate in the control volume isn n dM q dtρ= (5)where n q is the instantaneous flow rate in and out of one piston. From the definition of the bulk modulus,n dP d dt dtρρβ= (6) where Pn is the instantaneous pressure within the piston bore. Substituting Eqs. (5) and (6) into Eq. (4) yields(?)n n n n n ndP q dV d V w d βθθ=- (7) where the shaft speed of the pump is n d dtθω=. The instantaneous volume of one piston bore can be calculated by using Eq. (1) asn V = 0V + P A [R tan (α)sin (n θ)+ a sec (α) + e tan(α) ] (8)where P A is the piston sectional area and 0V is the volume of eachpiston, which has zero displacement along the x-axis (when n θ=0, π).The volume rate of change can be calculated at the certain swash angle, i.e., α =0, such thattan cos n p n ndV A R d αθθ=()() (9) in which it is noted that the piston bore volume increases or decreaseswith respect to the rotating angle of n θ.Substituting Eqs. (8) and (9) into Eq. (7) yields0[tan()cos()] [tan sin sec tan() ]n P n n n p n q A R dP d V A R a e βαθωθαθαα-=-++()()()(10)4 Optimal DesignsTo find the extrema of pressure overshoots and undershoots in the control volume of piston bores, the optimization method can be used in Eq. (10). In a nonlinear function, reaching global maxima and minima is usually the goal of optimization. If the function is continuous on a closed interval, global maxima and minima exist. Furthermore, the global maximum (or minimum) either must be a local maximum (or minimum) in the interior of the domain or must lie on the boundary of the domain. So, the method of finding a global maximum (or minimum) is to detect all the local maxima (or minima) in the interior, evaluate the maxima (or minima) points on the boundary, and select the biggest (or smallest) one. Local maximum or local minimum can be searched by using the first derivative test that the potential extrema of a function f( · ), with derivative ()f ', can solve the equation at the critical points of ()f '=0 [15].The pressure of control volumes in the piston bore may be found as either a minimum or maximum value as dP/ dt=0. Thus, letting the left side of Eq. (10) be equal to zero yieldstan()cos()0n p n q A R ωαθ-= (11)In a piston bore, the quantity of n q offsets the volume varying and thendecreases the overshoots and undershoots of the piston pressure. In this study, the most interesting are undershoots of the pressure, which may fall below the vapor pressure or gas desorption pressure to cause cavitations. The term oftan()cos()p n A R ωαθ in Eq. (11) has the positive value in the range of intake ports (22ππθ-≤≤), shown in Fig. 2, which means that the piston volume arises. Therefore, the piston needs the sufficient flow in; otherwise, the pressure may drop.In the piston, the flow of n q may get through in a few scenariosshown in Fig. 3: (I) the clearance between the valve plate and cylinder barrel, (II) the clearance between the cylinder bore and piston, (III) the clearance between the piston and slipper, (IV) the clearance between the slipper and swash plate, and (V) the overlapping area between the barrel kidney and valve plate ports. As pumps operate stably, the flows in the as laminar flows, which can be calculated as [16]312IV k k Ln i I k h q p L ωμ==∑ (12)where k h is the height of the clearance, k L is the passage length,scenarios I –IV mostly have low Reynolds numbers and can be regarded k ω is the width of the clearance (note that in the scenario II, k ω =2π· r, in which r is the piston radius), and p is the pressure drop defined in the intake ports as p =c p -n p (13)where c p is the case pressure of the pump. The fluid films through theabove clearances were extensively investigated in previous research. The effects of the main related dimensions of pump and the operating conditions on the film are numerically clarified inRefs. [17,18]. The dynamic behavior of slipper pads and the clearance between the slipper and swash plate can be referred to Refs. [19,20]. Manring et al. [21,22] investigated the flow rate and load carrying capacity of the slipper bearing in theoretical and experimental methods under different deformation conditions. A simulation tool calledCASPAR is used to estimate the nonisothermal gap flow between the cylinder barrel and the valve plate by Huang and Ivantysynova [23]. The simulation program also considers the surface deformations to predict gap heights, frictions, etc., between the piston and barrel andbetween the swash plate and slipper. All these clearance geometrics in Eq.(12) are nonlinear and operation based, which is a complicated issue. In this study, the experimental measurements of the gap flows are preferred. If it is not possible, the worst cases of the geometrics or tolerances with empirical adjustments may be used to consider the cavitation issue, i.e., minimum gap flows.For scenario V, the flow is mostly in high velocity and can be described by using the turbulent orifice equation as((Tn d i d d q c A c A θθ= (14)where Pi and Pd are the intake and discharge pressure of the pump and ()i A θ and ()d A θ are the instantaneous overlap area between barrel kidneys and inlet/discharge ports of the valve plate individually.The areas are nonlinear functions of the rotating angle, which is defined by the geometrics of the barrel kidney, valve plate ports,silencing grooves, decompression holes, and so forth. Combining Eqs.(11) –(14), the area can be obtained as3()K IV A θ==(15)where ()A θ is the total overlap area of ()A θ=()()i d A A θλθ+, and λ is defined as=In the piston bore, the pressure varies from low tohigh while passing over the intake and discharge ports of the valve plates. It is possible that the instantaneous pressure achieves extremely low values during the intake area( 22ππθ-≤≤ shown in Fig. 2) that may be located below the vapor pressure vp p , i.e., n vp p p ≤;then cavitations canhappen. To prevent the phenomena, the total overlap area of ()A θ mightbe designed to be satisfied with30()K IV A θ=≥(16)where 0()A θ is the minimum area of 0()A θ=0()()i d A A θλθ+ and 0λis a constant that is0λ=gaseous form. The vapor pressure of any substance increases nonlinearly with temperature according to the Clausius –Clapeyron relation. With the incremental increase in temperature, the vapor pressure becomes sufficient to overcome particle attraction and make the liquid form bubbles inside the substance. For pure components, the vapor pressure can be determined by the temperature using the Antoine equation as /()10A B C T --, where T is the temperature, and A, B, and C are constants[24].As a piston traverse the intake port, the pressure varies dependent on the cosine function in Eq. (10). It is noted that there are some typical positions of the piston with respect to the intake port, the beginning and ending of overlap, i.e., TDC and BDC (/2,/2θππ=- ) and the zero displacement position (θ =0). The two situations will be discussed as follows:(1) When /2,/2θππ=-, it is not always necessary to maintain the overlap area of 0()A θ because slip flows may provide filling up for the vacuum. From Eq. (16), letting 0()A θ=0,the timing angles at the TDC and BDC may be designed as31cos ()tan()122IV c vpk k i I P k p p h A r L ωϕδωαμ--≤+∑ (17) in which the open angle of the barrel kidney is . There is nocross-porting flow with the timing in the intake port.(2) When θ =0, the function of cos θ has the maximum value, which can provide another limitation of the overlap area to prevent the low pressure undershoots suchthat 30(0)K IVA =≥ (18)where 0(0)A is the minimum overlap area of 0(0)(0)i A A =.To prevent the low piston pressure building bubbles, the vaporpressure is considered as the lower limitation for the pressure settings in Eq. (16). The overall of overlap areas then can be derived to have adesign limitation. The limitation is determined by the leakage conditions, vapor pressure, rotating speed, etc. It indicates that the higher the pumping speed, the more severe cavitation may happen, and then the designs need more overlap area to let flow in the piston bore. On the other side, the low vapor pressure of the hydraulic fluid is preferred to reduce the opportunities to reach the cavitation conditions. As a result, only the vapor pressure of the pure fluid is considered in Eqs. (16)–(18). In fact, air release starts in the higher pressure than the pure cavitation process mainly in turbulent shear layers, which occur in scenario V.Therefore, the vapor pressure might be adjusted to design the overlap area by Eq. (16) if there exists substantial trapped and dissolved air in the fluid.The laminar leakages through the clearances aforementioned are a tradeoff in the design. It is demonstrated that the more leakage from the pump case to piston may relieve cavitation problems.However, the more leakage may degrade the pump efficiency in the discharge ports. In some design cases, the maximum timing angles can be determined by Eq. (17)to not have both simultaneous overlapping and highly low pressure at the TDC and BDC.While the piston rotates to have the zero displacement, the minimum overlap area can be determined by Eq. 18 , which may assist the piston not to have the large pressure undershoots during flow intake.6 ConclusionsThe valve plate design is a critical issue in addressing the cavitation or aeration phenomena in the piston pump. This study uses the control volume method to analyze the flow, pressure, and leakages within one piston bore related to the valve plate timings. If the overlap area developed by barrel kidneys and valve plate ports is not properly designed, no sufficient flow replenishes the rise volume by the rotating movement. Therefore, the piston pressure may drop below the saturated vapor pressure of the liquid and air ingress to form the vapor bubbles. To control the damaging cavitations, the optimization approach is used to detect the lowest pressure constricted by valve plate timings. The analytical limitation of the overlap area needs to be satisfied to remain the pressure to not have large undershoots so that the system can be largely enhanced on cavitation/aeration issues.In this study, the dynamics of the piston control volume is developed by using several assumptions such as constant discharge coefficients and laminar leakages. The discharge coefficient is practically nonlinear based on the geometrics, flow number, etc. Leakage clearances of the control volume may not keep the constant height and width as well in practice due to vibrations and dynamical ripples. All these issues are complicated and very empirical and need further consideration in the future. Theresults presented in this paper can be more accurate in estimating the cavitations with these extensive studies.Nomenclature0(),()A A θθ= the total overlap area between valve plate ports and barrel kidneys 2()mmAp = piston section area 2()mmA, B, C= constantsA= offset between the piston-slipper joint and surface of the swash plate 2()mmd C = orifice discharge coefficiente= offset between the swash plate pivot and the shaft centerline of the pump 2()mmk h = the height of the clearance 2()mmk L = the passage length of the clearance 2()mmM= mass of the fluid within a single piston (kg)N= number of pistonsn = piston and slipper counter,p p = fluid pressure and pressure drop (bar)Pc= the case pressure of the pump (bar)Pd= pump discharge pressure (bar)Pi = pump intake pressure (bar)Pn = fluid pressure within the nth piston bore (bar)Pvp = the vapor pressure of the hydraulic fluid(bar)qn, qLn, qTn = the instantaneous flow rate of each piston(l/min)R = piston pitch radius 2()mmr = piston radius (mm)t =time (s)V = volume 3()mmwk = the width of the clearance (mm)x ,x ˙= piston displacement and velocity along the shaft axis (m, m/s) x y z --=Cartesian coordinates with an origin on the shaft centerline x y z '''--= Cartesian coordinates with an origin on swash plate pivot ,αα=swash plate angle and velocity (rad, rad/s)β= fluid bulk modulus (bar)δδ= timing angle of valve plates at the BDC and TDC (rad),B Tϕ= the open angle of the barrel kidney(rad)ρ= fluid density(kg/m3),θω= angular position and velocity of the rotating kit (rad, rad/s)μ=absolute viscosity(Cp),λλ= coefficients related to the pressure drop外文中文翻译:在轴向柱塞泵气蚀问题的分析本论文讨论和分析了一个柱塞孔与配流盘限制在轴向柱塞泵的控制量设计。
引言概述:
正文内容:
一、外文翻译的重要性
1.外文翻译在学术领域的作用
外文翻译可以帮助我们了解和掌握国外学术前沿,扩大我们的学术视野,促进思维的创新与交流。
2.外文翻译在商业领域的意义
外文翻译在商业领域中,特别是跨国公司的经营中起到了至关重要的作用,能够帮助企业了解竞争对手的动态,并进行市场调研和产品开发。
3.外文翻译在文化交流中的作用
外文翻译是促进国与国之间文化交流的重要手段,能够传播本国文化,增进两国人民的友谊。
二、外文翻译的技巧
1.语言能力的培养
外文翻译的首要条件是具备扎实的外语基础,需要加强对词汇、语法和表达方式的学习。
2.翻译技巧与方法
翻译技巧包括对上下文的理解、逐词逐句的翻译和准确传达原意等。
同时,还可以运用翻译工具进行辅助翻译。
3.灵活运用翻译策略
根据翻译的目的和要求,可以选择直译、意译或文化转换等不同的翻译策略。
三、外文翻译的难点
1.语言和文化差异
不同语言和文化之间的差异可能导致翻译难度增加,需要对原文进行深入理解,并灵活运用翻译技巧。
2.专业术语的翻译
外文翻译中遇到的专业术语需要准确传达,这需要对相关领域的专业知识有一定的了解,可以借助词典和其他资源进行查询。
3.语义和语境的理解
在翻译过程中,对原文的语义和语境理解不准确可能导致误译,需要细致入微地理解每个句子和词语的意义。
四、外文翻译中常见的问题
1.语法和表达问题
外文翻译中经常会涉及到语法和表达问题,需要对原文和翻译文本进行仔细对比和校正,确保语法和表达的准确性。
2.遗漏和加词问题
翻译过程中可能会出现遗漏或者加词的情况,需要细心排查,保持原文和翻译文本的一致性。
3.歧义和模糊问题
外文翻译中可能会存在歧义和模糊的词语或句子,需要根据上下文进行准确的判断和翻译。
五、外文翻译的应用
1.学术研究和论文撰写
外文翻译能够帮助学者了解国外学术动态,并为自己的研究提供参考资料,从而提升论文的质量和水平。
2.商业与经济领域
外文翻译对于跨国公司的运营和市场开拓至关重要,可以帮助企业了解竞争对手和市场需求,为企业决策提供依据。
3.文化交流和传媒行业
外文翻译在文化交流和传媒行业中起到了重要的作用,可以传播本国文化,增进与其他国家之间的友谊。
总结:
本文详细介绍了毕业设计外文翻译的重要性、技巧、难点、常见问题以及应用。
外文翻译作为一项重要的能力,在学术、商业和
文化交流等领域都具有广泛的应用和意义。
通过研究和实践,我们可以不断提高自己的外文翻译能力,为自己的学术和职业发展打下坚实的基础。