外文原文
Study on Human Resource Allocation in Multi-Project Based on the Priority and the Cost of Projects
Lin Jingjing , Zhou Guohua
SchoolofEconomics and management, Southwest Jiao tong University ,610031 ,China
Abstract----This paper put forward the affecting factors of project’s priority. which is introduced into a multi-objective optimization model for human resource allocation in multi-project environment . The objectives of the model were the minimum cost loss due to the delay of the time limit of the projects and the minimum delay of the project with the highest priority .Then a Genetic Algorithm to solve the model was introduced. Finally, a numerical example was used to testify the feasibility of the model and the algorithm. Index Terms—Genetic Algorithm, Human Resource Allocation, Multi-project’s project’s priority .
1.INTRODUCTION
More and more enterprises are facing the challenge of multi-project management, which has been the focus among researches on project management. In multi-project environment ,the share are competition of resources such as
capital , time and human resources often occur .Therefore , it’s critical to schedule projects in order to satisfy the different resource demands and to shorten the projects’ duration time with resources constrained ,as in [1].For many enterprises ,the human resources are the most precious asset .So enterprises should reasonably and effectively allocate each resource , especially the human resource ,in order to shorten the time and cost of projects and to increase the benefits .Some literatures have discussed the resource allocation problem in multi-project environment with resources constrained. Reference [1] designed an iterative algorithm and proposed a mathematical model of the resource-constrained multi-project scheduling .Based on work breakdown structure (WBS) and Dantzig-Wolfe decomposition method ,a feasible multi-project planning method was illustrated , as in [2] . References [3,4] discussed the resource-constrained project scheduling based on Branch Delimitation method .Reference [5] put forward the framework of human resource allocation in multi-project in Long-term ,medium-term and short-term as well as research and development(R&D) environment .Based on GPSS language, simulation model of resources allocation was built to get
the project’s duration time and resources distribution, as in [6]. Reference [7] solved the engineering project’s resources optimization problem using Genetic Algorithms.
These literatures reasonably optimized resources allocation in multi-project, but all had the same prerequisite that the project’s importance is the same to each other .This paper will analyze the effects of project’s priority on human resource allocation ,which is to be introduced into a mathematical model ;finally ,a Genetic Algorithm is used to solve the model.
2.EFFECTS OF PROJECTS PRIORITY ON HUMAN RESOUCE ALLOCATION AND
THE AFFECTING FACTORS OF PROJECT’S PRIORITY
Resource sharing is one of the main characteristics of multi-project management .The allocation of shared resources relates to the efficiency and rationality of the use of resources .When resource conflict occurs ,the resource demand of the project with highest priority should be satisfied first. Only after that, can the projects with lower priority be considered.
Based on the idea of project classification management ,this paper classifies the affecting factors of project’s priority into three categories ,as the
project’s benefits ,the complexity of project management and technology , and the strategic influence on the enterprise’s future development . The priority weight of the project is the function of the above three categories, as shown in (1). W=f(I,c,s…) (1)
Where w refers to project’s priority weight; I refers to the benefits of the project; c refers to the complexity of the project, including the technology and management; s refers to the influence of the project on enterprise .The bigger the values of the three categories, the higher the priority is.
3.HUMAN RESOURCE ALLOCATION MODEL IN MULTI-PROJECT
ENVIRONMENT
3.1Problem Description
According to the constraint theory, the enterprise should strictly differentiate the bottleneck resources and the non-bottleneck resources to solve the constraint problem of bottleneck resources .This paper will stress on the limited critical human resources being allocated to multi-project with definite duration times and priority.
To simplify the problem, we suppose that that three exist
several parallel projects and a shared resources storehouse, and the enterprise’s operation only involves one kind of critical human resources. The supply of the critical human resource is limited, which cannot be obtained by hiring or any other ways during a certain period .when resource conflict among parallel projects occurs, we may allocate the human resource to multi-project according to project’s priorities .The allocation of non-critical independent human resources is not considered in this paper, which supposes that the independent resources that each project needs can be satisfied.
Engineering projects usually need massive critical skilled human resources in some critical chain ,which cannot be substituted by the other kind of human resources .When the critical chains of projects at the same time during some period, there occur resource conflict and competition .The paper also supposes that the corresponding network planning of various projects have already been established ,and the peaks of each project’s resources demand have been optimized .The delay of the critical chain will affect the whole
project’s duration time .
3.2 Model Hypotheses
The following hypotheses help us to establish a mathematical model:
(1) The number of mutually independent projects involved in resource allocation problem in multi-project is N. Each project is indicated with Q i ,while i=1,2, … N.
(2) The priority weights of multi-project have been determined ,which are respectively w 1,w 2…w n .
(3) The total number of the critical human resources is R ,with r k standing for each person ,while k=1,2, …,R
(4) Δk i = ???others toprojectQ rcer humanresou i k 01
(5) Resources capturing by several projects begins on time. t E
i is the expected duration time of project I
that needs the critical resources to finish some task after time t ,on the premise that the human resources demand can be satisfied .tAi is the real duration time of project I that needs the critical resource to finish some task after time t .
(6) According to the contract ,if the delay of the project happens the daily cost loss due to the delay is △c i for proje ct I .According to the project’s
importance ,the delay of a project will not only cause the cost loss ,but will also damage the prestige and status of the enterprise .(while the latent cost is difficult to quantify ,it isn’t considered in this article temporarily.)
(7)From the hypothesis (5) ,we can know that after time
t ,the time-gap between the real and expected duration time of project I that needs the critical resources to finish some task is △t i,( △t i=t A i-t E i). For there exists resources competition, the time –gap is necessarily a positive number.
(8)According to hypotheses (6) and (7), the total cost
loss of project I is C i (C i= △t i* △C i ).
(9)The duration time of activities can be expressed by
the workload of activities divided by the quantity of resources ,which can be indicated with following expression of t A i =ηi/R i*,.In the expression , ηi refers to the workload of projects I during some period ,which is supposed to be fixed and pre-determined by the project managers on project planning phase ; R i*refers to the number of the critical human resources being allocated to projects
I actually, with the equation R i * =∑=R
k ki 1δ existing. Due
to the resource competition the resource demands of projects with higher
Priorities may be guarantee, while those projects with lower priorities may not be fully guaranteed. In this situation, the decrease of the resource supply will lead to the increase of the duration time of activities and the project, while the workload is fixed.
3.3 Optimization Model
Based on the above hypotheses, the resource
allocation model in multi-project environment can be established .Here, the optimization model is :
F i =min Z i = min ∑∑
==N i i N i Ci 11
ω =min i i N i i N i c t ??∑∑==11ω (2)
=min ∑∑==N i i N i 11ω )
E i R i ki i t - ??∑=1δη i c ? 2
F =min Z 2=min ()i t ?=min )
E i R i ki i t - ??∑=1δη (3) Where wj=max(wi) ,(N j i 3,2,1,=?) (4)
Subject
to : 0∑∑==≤R k ki N i 11δ=R
(5) The model is a multi-objective one .The two objective functions are respectively to minimize the total cost loss ,which is to conform to the economic target ,and to shorten the time delay of the project with highest priority .The first objective function can only optimize the apparent economic cost ;therefore the second objective function will help to make up this limitation .For the project with highest priority ,time delay will damage not only the economic benefits ,but also the strategy and the prestige of the enterprise .Therefore we should guarantee that the most important project be finished on time or ahead of schedule .
4. SOLUTION TO THE MULTI-OBJECTIVE MODEL USING GENETIC ALGORITHM
4.1 The multi-objective optimization problem is quite
common .Generally ,each objective should be optimized in order to get the comprehensive objective optimized .Therefore the weight of each sub-objective should be considered .Reference [8] proposed an improved
ant colony algorithm to solve this problem .Supposed that the weights of the two optimizing objectives are α and β ,where α+β=1 .Then the comprehensive goal is F* ,where F*=αF1+βF2.
4.2 The Principle of Genetic Algorithm
Genetic Algorithm roots from the concepts of natural selection and genetics .It’s a random search technique for global optimization in a complex search space .Because of the parallel nature and less restrictions ,it has the key features of great currency ,fast convergence and easy calculation .Meanwhile ,its search scope is not limited ,so it’s an effective method to solve the resource balancing problem ,as in [9].
The main steps of GA in this paper are as follow:
(1)Encoding
An integer string is short, direct and
efficient .According to the characteristics of the
model, the human resource can be assigned to be a code
object .The string length equals to the total number
of human resources allocated.
(2)Choosing the fitness function
This paper choose the objective function as the foundation of fitness function .To rate the values of the objective function ,the fitness of the n-th individual is 1/n。
(3)Genetic operation
It’s the core of GA .This process includes three basic operators: selection operator, crossover operator, and mutation operation.
1)Selection operation is to select the good
individuals among the group .The probability of a
string to be selected as a parent is proportional
to its fitness .The higher the string’s fitness
is, the greater the probability of the string to
be selected as a parent will be.
2)Crossover operator
The so-called crossover is that the paten
chromosomes exchange some genes to yield two
offspring strings in some rule .We can use uniform
crossover ,that the two chromosomes exchange the
genes on the same positions with the same crossover
probability to yield two new individuals.
3)Mutation operator
Mutation adds to the diversity of a population and
thereby increases the likelihood that the
algorithm will generate individuals with better
fitness values .The mutation operator determines
the search ability of GA ,maintain the diversity
of a population ,and avoid the prematurity .There
are several mutation is quite easy .
4)Standard for the terminal of GA
Without human control ,the evolution process of the
algorithm will never end .The population size
affects the final result and the operation
speed .If the size is greater ,the diversity of the
population can be added ,and the best result can
be obtained easier .However ,the efficiency is
reduced .Recently ,in most GA progress , the
biggest evolvement algebra is determined by
human-beings to control the course the algorithm.
5.NUMERICAL EXAMPLE
We use a numerical example to illustrate the
effectiveness of Genetic Algorithm . Assume that there
are three projects with the same network ,and the
priority weights have been put forward .There is only
one critical path in each project . The data we have known are shown in Table 1.
Table 1 Data of the Three Projects
The steps of Genetic Algorithm to solve the model are as follow:
Step1: An integer string is adopted .Encode with [0,1,2] for there are three projects .The length of the chromosome is 16 ,the total number of human resource to be allocated . Step 2: The initial population size is 50.
Step 3: Doing genetic operation .Adopt Roulette Wheel and Elitist tactic to determined selection operator .The offspring can be yielded by uniform cross-over .The mutation operator can be determined by uniform mutation .We assume that the mutation probability equal to 0.001 .
Step 4: Adopt the maximum population size is 100 when terminated.
After the computer simulation, we can obtain the Pare-to results with different importance weights of the two objective functions, as shown in Table 2 :
Table 2 The Solution Result of the Model
From table 2 we can learn that , when αand β change ,the result is different .However we can obtain a series of Pareto results.
6.CONCLUSION
Human resource allocation in multi-project environment is
a complicated problem .This paper analyzes the importance
of project’s priority in resource allocation and establishes a human resource allocation model based on
priority and cost of projects .Finally, genetic Algorithm is adopted to solve the model.
During the construction process of the allocation model, we have put forward some hypotheses in order to simplify the problem .However, when the enterprises practically allocate the resources, hey will face more complexity, which is the focus of our future study.
中文翻译：
forced concrete structure reinforced with an overviewRein Since the reform and opening up, with the national economy's rapid and sustained development of a reinforced concrete structure built, reinforced with the development of technology has been great. Therefore, to promote the use of advanced technology reinforced connecting to improve project quality and speed up the pace of construction, improve labor productivity, reduce costs, and is of great significance. Reinforced steel bars connecting technologies can be divided into two broad categories linking welding machinery and steel. There are six types of welding steel welding methods, and some apply to the prefabricated plant, and some apply to the construction site, some of both apply. There are three types of machinery commonly used reinforcement linking method primarily applicable to the construction site. Ways has its own characteristics and different application, and in the continuous development and improvement. In actual production, should be based on specific conditions of work, working environment and technical requirements, the choice of suitable methods to achieve the best overall efficiency. 1、steel mechanical link 1.1 radial squeeze link Will be a steel sleeve in two sets to the highly-reinforced Department with superhigh pressure hydraulic equipment (squeeze tongs) along steel sleeve radial squeeze steel casing, in squeezing out tongs squeeze pressure role of a steel sleeve plasticity deformation closely integrated with reinforced through reinforced steel sleeve and Wang Liang's Position will be two solid steel bars linked Characteristic: Connect intensity to be high, performance reliable, can bear high stress draw and pigeonhole the load and tired load repeatedly.
机械设计 摘要：机器是由机械装置和其它组件组成的。它是一种用来转换或传递能量的装置，例如：发动机、涡轮机、车辆、起重机、印刷机、洗衣机、照相机和摄影机等。许多原则和设计方法不但适用于机器的设计，也适用于非机器的设计。术语中的“机械装置设计”的含义要比“机械设计”的含义更为广泛一些，机械装置设计包括机械设计。在分析运动及设计结构时，要把产品外型以及以后的保养也要考虑在机械设计中。在机械工程领域中，以及其它工程领域中，所有这些都需要机械设备，比如：开关、凸轮、阀门、船舶以及搅拌机等。 关键词：设计流程设计规则机械设计 设计流程 设计开始之前就要想到机器的实际性，现存的机器需要在耐用性、效率、重量、速度，或者成本上得到改善。新的机器必需具有以前机器所能执行的功能。 在设计的初始阶段，应该允许设计人员充分发挥创造性，不要受到任何约束。即使产生了许多不切实际的想法，也会在设计的早期，即在绘制图纸之前被改正掉。只有这样，才不致于阻断创新的思路。通常,还要提出几套设计方案，然后加以比较。很有可能在这个计划最后决定中,使用了某些不在计划之内的一些设想。 一般的当外型特点和组件部分的尺寸特点分析得透彻时，就可以全面的设计和分析。接着还要客观的分析机器性能的优越性，以及它的安全、重量、耐用性，并且竞争力的成本也要考虑在分析结果之内。每一个至关重要的部分要优化它的比例和尺寸，同时也要保持与其它组成部分相协调。 也要选择原材料和处理原材料的方法。通过力学原理来分析和实现这些重要的特性，如那些静态反应的能量和摩擦力的最佳利用，像动力惯性、加速动力和能量；包括弹性材料的强度、应力和刚度等材料的物理特性，以及流体润滑和驱动器的流体力学。设计的过程是重复和合作的过程，无论是正式或非正式的进行，对设计者来说每个阶段都很重要。 最后，以图样为设计的标准，并建立将来的模型。如果它的测试是符合事先要
NET-BASED TASK MANAGEMENT SYSTEM Hector Garcia-Molina, Jeffrey D. Ullman, Jennifer Wisdom ABSTRACT In net-based collaborative design environment, design resources become more and more varied and complex. Besides com mon in formatio n man ageme nt systems, desig n resources can be orga ni zed in connection with desig n activities. A set of activities and resources linked by logic relations can form a task. A task has at least one objective and can be broken down into smaller ones. So a design project can be separated in to many subtasks formi ng a hierarchical structure. Task Management System (TMS) is designed to break down these tasks and assig n certa in resources to its task no des. As a result of decompositi on. al1 desig n resources and activities could be man aged via this system. KEY WORDS : Collaborative Design, Task Management System (TMS), Task Decompositi on, In formati on Man ageme nt System 1 Introduction Along with the rapid upgrade of request for adva need desig n methods, more and more desig n tool appeared to support new desig n methods and forms. Desig n in a web en vir onment with multi-part ners being invo Ived requires a more powerful and efficie nt man ageme nt system .Desig n part ners can be located everywhere over the n et with their own organizations. They could be mutually independent experts or teams of tens of employees. This article discussesa task man ageme nt system (TMS) which man ages desig n activities and resources by break ing dow n desig n objectives and re-orga nizing desig n resources in conn ecti on with the activities. Compari ng with com mon information management systems (IMS) like product data management system and docume nt man ageme nt system, TMS can man age the whole desig n process. It has two tiers which make it much more flexible in structure. The lower tier con sists of traditi onal com mon IMSS and the upper one fulfills logic activity management through controlling a tree-like structure, allocating design resources and
外文翻译 英文原文 Belt Conveying Systems Development of driving system Among the methods of material conveying employed，belt conveyors play a very important part in the reliable carrying of material over long distances at competitive cost．Conveyor systems have become larger and more complex and drive systems have also been going through a process of evolution and will continue to do so．Nowadays，bigger belts require more power and have brought the need for larger individual drives as well as multiple drives such as 3 drives of 750 kW for one belt(this is the case for the conveyor drives in Chengzhuang Mine)．The ability to control drive acceleration torque is critical to belt conveyors’performance．An efficient drive system should be able to provide smooth，soft starts while maintaining belt tensions within the specified safe limits．For load sharing on multiple drives．torque and speed control are also important considerations in the drive system’s design. Due to the advances in conveyor drive control technology，at present many more reliable．Cost-effective and performance-driven conveyor drive systems covering a wide range of power are available for customers’ choices[1]. 1 Analysis on conveyor drive technologies 1．1 Direct drives Full-voltage starters．With a full-voltage starter design，the conveyor head shaft is direct-coupled to the motor through the gear drive．Direct full-voltage starters are adequate for relatively low-power, simple-profile conveyors．With direct fu11-voltage starters．no control is provided for various conveyor loads and．depending on the ratio between fu11-and no-1oad power requirements，empty starting times can be three or four times faster than full load．The maintenance-free starting system is simple，low-cost and very reliable．However, they cannot control starting torque and maximum stall torque；therefore．they are
土木工程毕业设计外文文献翻译修订版 IBMT standardization office【IBMT5AB-IBMT08-IBMT2C-ZZT18】
外文文献翻译 Reinforced Concrete （来自《土木工程英语》） Concrete and reinforced concrete are used as building materials in every country. In many, including the United States and Canada, reinforced concrete is a dominant structural material in engineered construction. The universal nature of reinforced concrete construction stems from the wide availability of reinforcing bars and the constituents of concrete, gravel, sand, and cement, the relatively simple skills required in concrete construction, and the economy of reinforced concrete compared to other forms of construction. Concrete and reinforced concrete are used in bridges, buildings of all sorts underground structures, water tanks, television towers, offshore oil exploration and production structures, dams, and even in ships. Reinforced concrete structures may be cast-in-place concrete, constructed in their final location, or they may be precast concrete produced in a factory and erected at the construction site. Concrete structures may be severe and functional in design, or the shape and layout and be whimsical and artistic. Few other building materials off the architect and engineer such versatility and scope. Concrete is strong in compression but weak in tension. As a result, cracks develop whenever loads, or restrained shrinkage of temperature changes, give rise to tensile stresses in excess of the tensile strength of the concrete. In
专业资料 学院： 专业：土木工程 姓名： 学号： 外文出处：Structural Systems to resist (用外文写) Lateral loads 附件：1.外文资料翻译译文；2.外文原文。
附件1：外文资料翻译译文 抗侧向荷载的结构体系 常用的结构体系 若已测出荷载量达数千万磅重，那么在高层建筑设计中就没有多少可以进行极其复杂的构思余地了。确实，较好的高层建筑普遍具有构思简单、表现明晰的特点。 这并不是说没有进行宏观构思的余地。实际上，正是因为有了这种宏观的构思，新奇的高层建筑体系才得以发展，可能更重要的是：几年以前才出现的一些新概念在今天的技术中已经变得平常了。 如果忽略一些与建筑材料密切相关的概念不谈，高层建筑里最为常用的结构体系便可分为如下几类： 1.抗弯矩框架。 2.支撑框架，包括偏心支撑框架。 3.剪力墙，包括钢板剪力墙。 4.筒中框架。 5.筒中筒结构。 6.核心交互结构。 7. 框格体系或束筒体系。 特别是由于最近趋向于更复杂的建筑形式，同时也需要增加刚度以抵抗几力和地震力，大多数高层建筑都具有由框架、支撑构架、剪力墙和相关体系相结合而构成的体系。而且，就较高的建筑物而言，大多数都是由交互式构件组成三维陈列。 将这些构件结合起来的方法正是高层建筑设计方法的本质。其结合方式需要在考虑环境、功能和费用后再发展，以便提供促使建筑发展达到新高度的有效结构。这并
不是说富于想象力的结构设计就能够创造出伟大建筑。正相反，有许多例优美的建筑仅得到结构工程师适当的支持就被创造出来了，然而，如果没有天赋甚厚的建筑师的创造力的指导，那么，得以发展的就只能是好的结构，并非是伟大的建筑。无论如何，要想创造出高层建筑真正非凡的设计，两者都需要最好的。 虽然在文献中通常可以见到有关这七种体系的全面性讨论，但是在这里还值得进一步讨论。设计方法的本质贯穿于整个讨论。设计方法的本质贯穿于整个讨论中。 抗弯矩框架 抗弯矩框架也许是低，中高度的建筑中常用的体系，它具有线性水平构件和垂直构件在接头处基本刚接之特点。这种框架用作独立的体系，或者和其他体系结合起来使用，以便提供所需要水平荷载抵抗力。对于较高的高层建筑，可能会发现该本系不宜作为独立体系，这是因为在侧向力的作用下难以调动足够的刚度。 我们可以利用STRESS，STRUDL 或者其他大量合适的计算机程序进行结构分析。所谓的门架法分析或悬臂法分析在当今的技术中无一席之地，由于柱梁节点固有柔性，并且由于初步设计应该力求突出体系的弱点，所以在初析中使用框架的中心距尺寸设计是司空惯的。当然，在设计的后期阶段，实际地评价结点的变形很有必要。 支撑框架 支撑框架实际上刚度比抗弯矩框架强，在高层建筑中也得到更广泛的应用。这种体系以其结点处铰接或则接的线性水平构件、垂直构件和斜撑构件而具特色，它通常与其他体系共同用于较高的建筑，并且作为一种独立的体系用在低、中高度的建筑中。
Commercial Buildings Abstract: A guide and general reference on electrical design for commercial buildings is provided. It covers load characteristics; voltage considerations; power sources and distribution apparatus; controllers; services, vaults, and electrical equipment rooms; wiring systems; systems protection and coordination; lighting; electric space conditioning; transportation; communication systems planning; facility automation; expansion, modernization, and rehabilitation; special requirements by occupancy; and electrical energy management. Although directed to the power oriented engineer with limited commercial building experience, it can be an aid to all engineers responsible for the electrical design of commercial buildings. This recommended practice is not intended to be a complete handbook; however, it can direct the engineer to texts, periodicals, and references for commercial buildings and act as a guide through the myriad of codes, standards, and practices published by the IEEE, other professional associations, and governmental bodies. Keywords: Commercial buildings, electric power systems, load characteristics 1. Introduction 1.1 Scope This recommended practice will probably be of greatest value to the power oriented engineer with limited commercial building experience. It can also be an aid to all engineers responsible for the electrical design of commercial buildings. However, it is not intended as a replacement for the many excellent engineering texts and handbooks commonly in use, nor is it detailed enough to be a design manual. It should be considered a guide and general reference on electrical design for commercial buildings. 1.2 Commercial Buildings The term “commercial, residential, and institutional buildings”as used in this chapter, encompasses all buildings other than industrial buildings and private dwellings. It includes office and apartment buildings, hotels, schools, and churches, marine, air, railway, and bus terminals, department stores, retail shops, governmental buildings, hospitals, nursing homes, mental and correctional institutions, theaters, sports arenas, and other buildings serving the public directly. Buildings, or parts of buildings, within industrial complexes, which are used as offices or medical facilities or for similar nonindustrial purposes, fall within the scope of this recommended practice. Today’s commercial buildings, because of their increasing size and complexity, have become more and more dependent upon adequate and reliable electric systems. One can better understand the complex nature of modern commercial buildings by examining the systems, equipment, and facilities listed in 1.2.1. 1.2.2 Electrical Design Elements In spite of the wide variety of commercial, residential, and institutional buildings, some electrical design elements are common to all. These elements, listed below, will be discussed generally in this section and in detail in the remaining sections of this recommended practice. The principal design elements considered in the design of the power, lighting, and auxiliary systems include: 1) Magnitudes, quality, characteristics, demand, and coincidence or diversity of loads and load factors 2) Service, distribution, and utilization voltages and voltage regulation 3) Flexibility and provisions for expansion
. 轻型发动机设计方案 摘要： 在过去的一些年里，新一代汽车发动机燃油效率并不是像我们预料中的那样会有所降低。其原因：汽车重量的增加。通过对汽车发动机整车重量以及部分重量的分析知：曲轴箱作为一个单一部件具有潜在的可减少重量的部件，这篇论文讲述的是通过利用轻型材料和现代的设计手段减少发动机重量的方法。 将轻型材料应用于曲轴箱设计构思中包含着广泛的设计理念，这种设计理念就是尽最大可能利用被选材料所具有的可能性去减少汽车重量，以下我将详细的谈论关于直列式和V-型发动机特殊方法的构思，发动机重量减轻也可以利用中小型发动机来代替又大又重的发动机，现代技术以被应用于现存的发动机设计构思中从而增加发动机功率重量比，使发动机性能得到提高因此它的市场价值也得到提高。 新型轻型发动机设计方案中有一个重要方面就是与传统发动机设计理念相比要尽量减小发动机零部件数量，因为这样对于减少整车重量有着非常重要作用。 介绍： 汽车在生态方面和将来继续充当普通交通工具的要求已经显著提高尤其在美国和欧洲。通过合法的要求使那些有压力的顾客在这方面得到缓解。必需考虑到这样的事实，对于燃油的消耗，排放，回收在利用这些中心问题要有一个回应。 在过去的一些年里，汽车发动机的发展取的了进步，使发动机功率得到了显著的提高同时在降低发动机燃油消耗和排放方面已经付出巨大的努力。通过应用直喷，废气涡轮增压和多气门技术于柴油发动机中，使发动机的性能得到显著提高。 新车取代与在它之前所有具有相类似功能车时，其新车发动机工作效率的提高并不是通过对原有车的有效改进。整个交通工具工作效率停滞不前甚至降低的原因是在过去的十五年里增加了15%~20%的车辆（图1）。尽管轻型材料的使用不断增长以及设计者有意识的向轻型结构方面设计但是重量减轻却被其他方面所弥补。读者可以通过以下方面得知：多余的汽车外形 安全方面的改进
PA VEMENT PROBLEMS CAUSED BY COLLAPSIBLE SUBGRADES By Sandra L. Houston,1 Associate Member, ASCE (Reviewed by the Highway Division) ABSTRACT: Problem subgrade materials consisting of collapsible soils are com- mon in arid environments, which have climatic conditions and depositional and weathering processes favorable to their formation. Included herein is a discussion of predictive techniques that use commonly available laboratory equipment and testing methods for obtaining reliable estimates of the volume change for these problem soils. A method for predicting relevant stresses and corresponding collapse strains for typical pavement subgrades is presented. Relatively simple methods of evaluating potential volume change, based on results of familiar laboratory tests, are used. INTRODUCTION When a soil is given free access to water, it may decrease in volume, increase in volume, or do nothing. A soil that increases in volume is called a swelling or expansive soil, and a soil that decreases in volume is called a collapsible soil. The amount of volume change that occurs depends on the soil type and structure, the initial soil density, the imposed stress state, and the degree and extent of wetting. Subgrade materials comprised of soils that change volume upon wetting have caused distress to highways since the be- ginning of the professional practice and have cost many millions of dollars in roadway repairs. The prediction of the volume changes that may occur in the field is the first step in making an economic decision for dealing with these problem subgrade materials. Each project will have different design considerations, economic con- straints, and risk factors that will have to be taken into account. However, with a reliable method for making volume change predictions, the best design relative to the subgrade soils becomes a matter of economic comparison, and a much more rational design approach may be made. For example, typical techniques for dealing with expansive clays include: (1) In situ treatments with substances such as lime, cement, or fly-ash; (2) seepage barriers and/ or drainage systems; or (3) a computing of the serviceability loss and a mod- ification of the design to "accept" the anticipated expansion. In order to make the most economical decision, the amount of volume change (especially non- uniform volume change) must be accurately estimated, and the degree of road roughness evaluated from these data. Similarly, alternative design techniques are available for any roadway problem. The emphasis here will be placed on presenting economical and simple methods for: (1) Determining whether the subgrade materials are collapsible; and (2) estimating the amount of volume change that is likely to occur in the 'Asst. Prof., Ctr. for Advanced Res. in Transp., Arizona State Univ., Tempe, AZ 85287. Note. Discussion open until April 1, 1989. To extend the closing date one month,
Manufacturing Engineering and Technology—Machining Serope kalpakjian；Steven R.Schmid 机械工业出版社2004年3月第1版 20.9 MACHINABILITY The machinability of a material usually defined in terms of four factors: 1、Surface finish and integrity of the machined part; 2、Tool life obtained; 3、Force and power requirements; 4、Chip control. Thus, good machinability good surface finish and integrity, long tool life, and low force And power requirements. As for chip control, long and thin (stringy) cured chips, if not broken up, can severely interfere with the cutting operation by becoming entangled in the cutting zone. Because of the complex nature of cutting operations, it is difficult to establish relationships that quantitatively define the machinability of a material. In manufacturing plants, tool life and surface roughness are generally considered to be the most important factors in machinability. Although not used much any more, approximate machinability ratings are available in the example below. 20.9.1 Machinability Of Steels Because steels are among the most important engineering materials (as noted in Chapter 5), their machinability has been studied extensively. The machinability of steels has been mainly improved by adding lead and sulfur to obtain so-called free-machining steels. Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions (second-phase particles), which act as stress raisers in the primary shear zone. As a result, the chips produced break up easily and are small; this improves machinability. The size, shape, distribution, and concentration of these inclusions significantly influence machinability. Elements such as tellurium and selenium, which are both chemically similar to sulfur, act as inclusion modifiers in
外文原文 Study on Human Resource Allocation in Multi-Project Based on the Priority and the Cost of Projects Lin Jingjing , Zhou Guohua SchoolofEconomics and management, Southwest Jiao tong University ,610031 ,China Abstract----This paper put forward the affecting factors of project’s priority. which is introduced into a multi-objective optimization model for human resource allocation in multi-project environment . The objectives of the model were the minimum cost loss due to the delay of the time limit of the projects and the minimum delay of the project with the highest priority .Then a Genetic Algorithm to solve the model was introduced. Finally, a numerical example was used to testify the feasibility of the model and the algorithm. Index Terms—Genetic Algorithm, Human Resource Allocation, Multi-project’s project’s priority . 1.INTRODUCTION More and more enterprises are facing the challenge of multi-project management, which has been the focus among researches on project management. In multi-project environment ,the share are competition of resources such as capital , time and human resources often occur .Therefore , it’s critical to schedule projects in order to satisfy the different resource demands and to shorten the projects’duration time with resources constrained ,as in [1].For many enterprises ,the human resources are the most precious asset .So enterprises should reasonably and effectively allocate each resource , especially the human resource ,in order to shorten the time and cost of projects and to increase the benefits .Some literatures have