英文原文：
TITLE: MAPCon: AN EXPERT SYSTEM TO CONFIGURE
COMMUNICA TIONS NETWORKS
CONTACT: H. Van Dyke Parunak, James Kindrick, and Tihamer Toth-Fejel
Industrial Technology Institute
PO Box 1485
Ann Arbor, MI 48106
van%iti@https://www.doczj.com/doc/204468636.html,
(313) 769-4049
TOPIC: Case Study: configuration.
ABSTRACT: MAPCon is an expert system that performs off-line parameter configuration for local area networks that use MAP, the
Manufacturing Automation Protocol. This paper describes the
configuration task in general and MAPCon in particular, and
describes its performance as a function of network size.
MAPCon: AN EXPERT SYSTEM TO
CONFIGURE COMMUNICATIONS NETWORKS
H. Van Dyke Parunak, James Kindrick, and Tihamer Toth-Fejel
Industrial Technology Institute
1. Problem Definition
This section outlines the challenge of network management in general and the MAP architecture in particular, and describes the specific functions that MAPCon fulfills.
1.1. The Challenge of Network Management
Management of multi-vendor networks is difficult, since most network management products are designed for a single product line. Network management is especially critical in manufacturing LANs, where real-time manufacturing operations rely heavily on consistent network operation. One way to address this problem is to conform the network to a standard, such as the Manufacturing Automation Protocol (MAP). MAPcon 11, the system described in this case study, is the second generation (11 of a knowledgebased system designed to assist in configuring MAP networks . This function, the first that must be accomplished when designing a network, requires the correlation of a large number of parameters in complex ways in order for the
network to behave properly.
1.2. MAP Architecture MAP complies with the architecture of a set of international standards defined by the International Organization for Standardization (ISO), based on a reference model for Open Systems Interconnection (OSI). OS1 decomposes the problem of communicating reliably between applications into seven layers: physical, data-link, network, transport, session, presentation, and application.
The physical and data-link layers of MAP use the IEEE 802.4 token bus
specifications, in contrast to the CSMA/CD technology familiar from Ethernet. The physical layer can be either broadband or carrierband. WCon distinguishes between broadband and carrierband, and can configure both types of networks. In MAP, the network layer uses the ISO connection-less protocol or the =called Internet protocol. The transport layer uses the IS0 class 4 transport protocol. 1,Session uses ISOsession version 2, which is a small, basic subset of ISO session protocol. Presentation uses the ISO presentation layer.
MAP specifies several application layer protocols: a manufacturing message specification protocol; an association control service element; a file transfer, access and management protocol; a directory services protocol; and a network management protocol. The protocols at layers 1, 2, and 7 of MAP were partially or completely designed with manufacturing automation in mind.
The entities in the MAP network architecture include stations or end systems, subnetworks or LAN [Local Area Network) segments, and interconnections or intermediate systems.
Stations combine hardware and software to provide communications according to the MAP specification. They can have either a full MAP, a mini-MAP, or a MAPIEPA (Enhanced Perjormance Architecture) configuration. The current version of MAPCon handles only full MAP stations.
A subnetwork or LAN segment is a section of a local area network on which all stations share the same token. All stations. on a segment can directly cornmunitate to all other stations on the same segment without any intermediate systems. Subnetworks are of two types: broadband and carrierband. MAPCon handles both types of subnetworks.
Interconnection entities (intermediate systems) are devices that connect multiple subnetworks to form the overall MAP network. They are of three types: bridges, routers, and gateways. A bridge interconnects two or more subnetworks with similar media access control services. A router interconnects two or more subnetworks or nptworks of different types. A gateway interconnects two or more subnetworks or networks of different network architecture by performing protocol translation. The current version of MAPCon supports bridges and the MAP side of routers and gateways.
1.3. Configuration Management
Configuration management is the collection of network management activities that allow the user to know and control the arrangement and state of a network and its entities. The present version of MAPCon lets the user set the network configuration off- line, and thus know its arrangement and state. A future version will let the user control the network configuration as the network operates. The following paragraphs discuss the functions currently provided by MAPCon.
Adding or deleting stations in the subnetwork defines the actual topology of the network. Stations and interconnections that are attached to a subnetwork are specified in order to configure the network. This capability not only allows for examining the current configuration of the network but also permits
incremental changes to the configuration.
Subnetworks are interconnected by attaching interconnection devices such as bridges, routers, and gateways. Adding such devices requires setting or modifying the relationships between two or more subnetworks.
Users need to set the initial characteristics of entities and modify them if the original settings are inconsistent. In general, the characteristics that are set or modified correspond to operational parameters and statistical counters required and maintained by the entities. Each station or interconnection has several layers.
Depending on the configuration of the station or the interconnection, specific layers must be present according to the MAP 3.0 specification. Several characteristics in each layer must be set properly across the subnetwork and network in order to configure an operational network. These characteristics include operational parameters, timers, and thresholds on statistical counters. Some of these characteristics are derived from network-wide parameters such as the type of the traffic intended on the network and the nature of the environment under which network will operate (low noise, medium noise, and high noise). Other characteristics are derived from one another. For example, inactivity time at transport is derived from retransmission time and number of retransmissions.
Stations and interconnections within a subnetwork must have unique names and MAC addresses. However, there are certain restrictions on names and addresses from a global network point of view. It may be possible to have identical MAC addresses in subnetworks interconnected by a router. The configuration function
must check address consistency.
Similar to names and addresses, network managers and load servers must be assigned to stations and interconnections. All stations and interconnections need an associated manager. It is possible to have multiple managers in a network, up to one per subnetwork. A load server for the network is needed if there are any
loadable stations or interconnections in the network configuration.
Configuration also requires consistency checks to make sure that all entities are configured correctly. Mechanisms must be provided to recognize and identify the inconsistencies for corrective actions. Consistency in addresses, network managers, and load servers must be checked before the configuration objective is completed.
2. Previous Approaches
AI applications in network management have concentrated in the area of diagnosis and fault management rather than configuration.
Expert systems for network configuration have been introduced by some vendors, including BBN and CASE Communications. Technical case studies of these commercial products have not been released, so few details of their structure and function are available. At least one uses OPS-83 rules as its major knowledge representation mechanism. While MAPCon does use some OPS rules, it relies heavily on knowledge represented in frames, to support a structural model of
the network. This type of structure has also been reported in BBN’s Designe t.
Previous systems deal with wide-area networks, and focus on problems of routing and resource allocation. One suggested formalization is to allocate network capacity by maximizing an economic criterion related to network revenues. 1151 However, the complexity of the problem precludes use of standard operations research techniques to address this problem. [I21 BBN’s offering includes a facility to allocate parts, such as cables, boards, and racks, to node sites, much along the lines of RI.
MAP’S open architecture and bus structure remove problems that other networks must address. Because MAP networks use a bus rather than a point-bpoint architecture, routing is less of a problem. Because MAP is an open architecture, supporting equipment from different vendors, problems of configuring the boards and cables in a single station are also outside of its scope. The major problem addressed by WCon is consistency of parameter settings across different stations. This problem is not a critical one in the networks served by the other programs named above, because they are predominantly single-vendor networks, in which consistency among operating parameters can be enforced at the design or manufacturing stage of a station’s life. The open architecture that allows MAF’Con to push the ”board and cable” problem back to the manufacturer, also forces the network administrator (rather than the manufacturer) to worry about parameter consistency. Furthermore, MAP differs from these other networks in conforming to IS0 protocols for the OS1 seven layer model. The complexity of these protocols and the level of service they provide require many station parameters (62 in MAP 3.0), leading to the need for MAPCon.
3. Our Approach
In this section we discuss some details of MAPCon’s inner structure and function. We detail the different techniques of knowledge representation that it uses, and show how it performs both synthesis and analysis in its reasoning. Then we sketch how the interplay between these reasoning domains will increase as MAF’Con evolves from a configuration tool toward a full-fledged network supervisor.
3.1、Knowledge Representation The existing network configuration systems on which details are available use heuristic knowledge in rules as their main knowledge resou rce. MAPCon’s central knowledge structure is a semantic net model of the network being configured, constructed in the Carnegie Representation Language. It does use rules, but as a means of constraining relations among these objects more than to capture shallow information about configuration preferences, It also uses some procedural computation.
3.1.1. Frames
The major domain knowledge involved in MAP network configuration is the identity and interrelation of the network entities, so a frame model is both a natural way to store this information and a reasonable basis for propagating constraints among related entities.
The features of frames that are most important for MAPCon are
modularity, connectivity, inheritance, and demons.
MAPCon interactively guides the user in the construction of the network model. Each network entity (including subnetworks, stations, intermediate systems such as routers or bridges, and points of attachment) corresponds to a CRL frame, and its configurable parameters are slots in the frame.
MAPCon frames are related to each other by relations such as my-intermediate-system, relating a point of attachment to its intermediate system, and has-elements, relating subnetworks to their component stations and points of attachment. Frames conveniently permit the system to maintain a deep understanding about the connectivity of the network. For example, intermediate systems can be one of three types. The type of intermediate system connecting two subnetworks determines the quality of service provided by the network across that connection. One type of intermediate system supports address translation, while another type does not. Thus, two interconnected subnetworks may or may not be required to share an address space, depending upon the type of intermediate system providing the connection.
MAPCon frames make extensive use of inheritance. For example, a subnetwork frame shares many structural characteristics of a network frame, while the three kinds of intermediate systems have numerous points of similarity. The class structur e of MAF’Con’s ontology permits easy addition of new kinds of entities.
In developing a consistent set of parameters, a change in one parameter may have a cascading effect on others. MAPCon uses demons attached to critical slots to propagate these constraints among related objects. For example, mazimum-ring-maintenance-rotation -time is a station parameter based on a user input value for the enclosing subnetwork.
The key subnetwork input value propagates to the component stations over the has-elements relation, and constrains the value of the dependent parameter of each station.
3.1.2. Rules and Procedural Knowledge
In classical expert systems, rules are used to capture the heuristic, shallow knowledge of human experts. While =me MAPCon rules serve this function, most constrain relations among slots on the objects representing MAP network elements. Some relations can be constrained through inheritance among objects. In other cases, particularly when several parameters of a single element interact, procedural code attached by demons to affected slots. In the remaining cases, rules permit straightforward declarative specification of interdependencies that would otherwise require complicated, error-prone and hard-to-modify procedural code. For example, validation of an assigned network manager may require searching multiple interconnected subnetworks and is much easier to understand and implement as a (declarative) rule than an extensive (procedural) search through the semantic model.
3.2. Synthesis and Analysis
It is useful to distinguish between two classes of reasoning objectives: synthesis and analysis. Like many other real-world systems, MAPCon does both,
switching between them when appropriate.
The basic synthesis problem seeks, given a set of elements and a set of constraints among those elements, to assemble from the elements a structure that satisfies the constraints. The term “planning“ is often used loosely to describe this process, though we prefer to reserve it for a more specific case. We distinguish three major types of
synthesis, which differ in the class of data [I71 used to represent time in its constraints. We can thus define configuration as synthesis in nominal time; planning in the strict sense as synthesis in ordinal time; and scheduling as synthesis in interval time.
Analysis begins with a known structure and reasons about the relation between its behavior and the elements that make it up. The two major forms of analysis are prediction, which reasons from the structure and the behavior of its elements to the behavior of the whole, and interpretation, which reasons from the structure and its observed behavior to the state of its elements. Interpretation in turn can involve monitoring to detect unexpected behavior and diagnosis to explain that behavior.
MAPCon is primarily a synthetic system, performing static configuration in the nominal time domain. 1181 MAF’Con determines values for 62 interdependent, configurable parameters for each configurable element (station or point of attachment) of the MAP network being modeled.
The parameter setting process must follow a partial time ordering, but the resultant configuration itself is nominal with respect to time.
4. Performance
The performance of an expert system can be measured both in terms of how well and how quickly it executes its task. It is also interesting to record the match between domain and knowledge engineering environment by noting the amount of custom code needed to build an application.
4.1. How Well does MAPCon Perform?
WCon's task is to determine whether the parameters in the components of a given network can be configured consistently with one another, and if they can, to perform that configuration. Its structure is such that it always succeeds in configuring a configurable network and in properly flagging an unconfigurable one. Thus, it performs its task well.
4.2. How Fast does MAPCon Perform?
Since expert systems are often applied in domains that suffer from combinatorial complexity, it is important to understand their speed performance as a function of problem size. While analytic complexity bounds may be available for simple cases, the most straightforward way to assess the speed performance of a full-scale system is to gather execution statistics for it. To this end, we have carried out some preliminary experiments on MAPCon.
Leaving aside the user interface, the actual configuration task has three computational phases: procedural computation on the parameters supplied by the user;
rule-directed reasoning; and a final phase of procedural computation. We recorded CPU time (on a TI Explorer) for each of these phases, and total number of rule invocations, for five test networks that differed from one another both in the number of stations and in the number of subnetworks.
Exhibit 1 shows the number of stations and subnetworks in each test network. Note that configurations 2 and 4 both have ten stations, while 3 and 5 both have twenty stations. The differences between them are thus due only to the division into subnetworks in configurations 4 and 5. In both cases, this division takes the form of a star configuration, with a single router connecting the subnetworks.
In all five configurations, the total number of rule invocations per configuration is linear in the number of stations, regardless of the number of subnetworks.
In the plots accompanying this discussion, we use lower case 'x' and '0' to represent configurations 1, 2, and 3, which we will often call collectively "123" and which compare number of stations in a single network. Upper case 'X' and '0' represent configurations 1, 4, and 5 (collectively '145'), which compare results for different numbers of networks. Configuration 1 appears in both sets.
Exhibit 2 plots raw CPU time to execute the OPS rules portion of the inference cycle, as a function of number of stations, for configurations 123. This graph shows a roughly linear increase in execution time with size of working memory, a result in keeping with more general results on the Rete algorithm. But there is a slight convexity (cupped shape) to the curve. To see more detail, we fit by eye a straight line (y = 10.4~ - 25.7) to the data, and subtract it out, leaving the residuals plotted in Exhibit 3. We have removed slope and magnitude information from these residuals, and in exchange can see more clearly the slight (note the difference in scale between Exhibits 2 and 3) convexity hinted at in the earlier exhibit.
翻译
原文著作（期刊）名称：MAPCon: AN EXPERT SYSTEM TO CONFIGURE COMMUNICATIONS NETWORKS
作者：Van Dyke Parunak, H.; Kindrick, J.; Toth-Fejel
原文所在位置：IEEE Xplore数据库
原文出版时间：2002
原文出版地点：美国
MAPCon：配置网络的专家系统
1、问题定义
本节总体概述了网络管理的挑战并且特别说明了MAP体系结构，并介绍了满足MAPCon的特殊功能。
1.1 网络管理的挑战
因为大多数网络管理产品都是为一个单一产品线设计的，所以多厂商网络管理很困难。网络管理在制造局域网方面尤其的重要，在实时制造操
作非常依赖于网络的一致运行。来解决这个问题的一个办法是，整合网络到达一个标准如制造自动化协议（MAP）的标准。在这个案例研究描述的系统，MAPcon11，是第二代。设计出的基于知识系统旨在帮助MAP网络配置此功能，首先，当设计网络时，为了网络运行正常，必须完成就复杂的大量参数之间的关系需要络循规蹈矩。
1.2 MAP 体系结构
在开放系统互连（OSI）参考模型为基础上，MAP符合一个由国际标准化组织（ISO）规定的一套国际结构标准。OS1分解七个层之间的应用程序的问题：物理层, 数据链路层, 网络层, 传输层，会话层, 表示层和应用层.
MAP 中物理层和数据链路层使用IEEE802.4规范总线，与熟悉的以太网中的CSMA/ CD技术形成对比。物理可以是宽频带或载波宽带。 WCon可以区分宽频带和载波宽带，并可以配置两种类型的网络。在MAP中，网络层采用无连接协议或是所谓的互联网协议。传输层采用ISO传输层类4协议。会话层使用ISO会话协议的一个小型的、基本的子集：1,ISO会话版本2,表示采用ISO表示层。
MAP明确说明了几个应用层协议：制造报文规范协议；关联控制服务元素；文件传送；访问和管理协议；目录服务协议，以及网络管理协议。这些协议在MAP的1、2、7层都是部分或完全用制造自动化设计出。
在MAP网络架构中，实体包括站点或端系统, 子网，局域网和互联或中间系统。
站点结合硬件和软件，根据MAP规范来提供信息。他们可以有一个完整的MAP，迷你MAP，或者MAPIEPA配置。当前的MAPCon版本只处理完整地MAP站点。
一个子网或局域网段是一个局域网上所有站点共享同样记号的一部分。这一段可以直接同没有任何中间系统的在同一网段上的所有其他系统进行沟通。子网有两种类型：宽频带和载波宽带。 MAPCon处理这两种类型的子网。
互连实体（中间系统）设备，是连接多个子网来形成整体MAP网络的设备。他们有三种类型：网桥，路由器和网关。一个网桥连着两个或更多的类似传播媒介的子网来控制服务。一个路由器连着两个或多个子网或不同类型的网络。网关连着两个或多个子网或不同的通过执行协议转换网络体系架构的网络。当前的MAPCon版本支持网桥和路由器和网关的MAP的一端。
1.3 配置管理
配置管理是一组使用户能够了解和控制网络及其运行实体安置情况和状态的网络管理活动集合。目前版本的MAPCon只能在客户将网络配置状态设置为离线状态时才能知晓其安置情况和状态，而未来版本的则可在网络运行时就让客户控制网络配置。下面的段落将主要阐述目前MAPCon能提供的功能。
以增加或删除子网形式来定义网络拓扑结构。与子网相关联的网站和相互连接器都将被具体说明以便于配置网络。这种设置不仅可以用于检查当前的网络配置，也允许配置发生额外变化。
子网与网桥，路由器，网关等附加装置相互连接。添加这些装置需要设置和修改两个或多个子网之间的关系。
用户需要设置网络实体的初始特性，当与原始设置不同时要进行修改。一般情况下设置或修改的特性需要与运行参数以及实体运行所需的统计数据相一致。每个网站都有几个层次。
根据一些网站的配置情况，特定的层次需要以 MAP 3.0为规范来设置。每一层的特性都要同子网和网络进行准确设置，以便配置一个业务网络。这些特性包括操作参数，定时器和计数器统计阈值。他们有些是来自整个网络的参数，如在网络上的流量类型和网络运行环境（低噪声，中噪声，高噪声）。其他特性是参照一些特性来设置的，比如运输状态下的休眠时间是由转播时间和转播数量来设置的。
有子网的网站等必须要有唯一的名称和MAC地址。然而全球性的网络其名称和地址有一定的限制规定。它需要有和通过路由器相连的子网一样的MAC地址。配置功能会检查其地址的一致性。
类似的名称和地址，网络管理员和负载服务器必须被分配到网站和内部链接中去。所有的网站和内部链接都需要一个相关的管理员，一个网络可以有多个管理员，高达每个子网一个。网络配置中如果有可装载的网站或内部链接则需要有网络负载服务器。
配置也需要有一致性检查以保证所有实体都配置正确。且要设置识别确定需要纠正的矛盾等机制。地址，网络管理员及路由器的一致性也需在配置设备完成前进行检查。
2、以前的办法
网络管理中的人工智能的应用都集中在诊断和故障管理区域，而不是配置方面。
网络配置的专家系统已经由一些厂商介绍了，包括BBN和CASE 通信。这些商业产品的技术案例研究没有被公布，所以其结构与功能等一些细节信息都不知道。至少有一个使用OPS-83规则作为其主要的知识表示机制。虽然MAPCon确实使用了一些OPS 规则，它在很大程度上依赖于框架代表的知识，以支持网络的结构模型。这种类型的结构也有在BBN 的Designet上报道。
以前的系统处理广域网络时，主要集中在路由器和资源分配的问题上。一个建议是形式化，通过最大化的经济准则相关网络收入来分配网络容量。1151然而，问题的复杂性不能使用操作研究技术标准来解决这个问题。BBN 公司提供的产品包括一个设施，分配零件如电缆，电路板，和机架部件，到沿着RI线条的节点网站。随着国际扶轮线了。地图的开放式结构和总线结构中删除的问题，其他网络必须正视的。因为映射网络使用的总线，而不是一个point-bpoint体系结构，路由是一个小问题。因为MAP是一个开放的体系结构，支持不同厂商的设备，配置在一个车站板和电缆的问题，也是它的范围之外。由WCon的主要问题是在不同的处理站的参数设置的一致性。这个问题是不是由上面提到的其他方案的网络服务的关键之一，因为他们大多是单一供应商网络，在这种操作参数之间的一致性，可以在一个站的寿命设计或制造阶段执行。开放式架构，允许MAF'Con推动“板和电缆”问题退还给厂家，也迫使网络管理员（而不是制造商）担心参数的一致性。此外，MAP的不同之处符合为OS1支持ISO七层模型从这些协议的其他网络。这些协议的复杂性和他们所提供的服务水平需要许多台站参数，导致了MAPCon需要。
3、我们的方法
在本节中我们讨论MAPCon的内部结构和功能的一些细节。我们详细的知识表示，它使用了不同的技术，并展示它如何执行其推理合成和分析。然后，我们这些素描如何推理领域之间的相互作用会增加MAF'Con从走向成熟的网监配置工具演变。
3.1.知识表征系统
现有的网络配置上的细节可在规则中使用启发式知识作为自己的主要知识资源。MAPCon的中心知识结构是一个在卡内基表示语言构造，被配置的语义网模型的网络。它使用规则，但由于这些对象之间的制约关系，以多获取有关信息的手段配置首浅，它也使用了一些程序上的计算。
3.1.1框架
在MAP网络配置中涉及的主要领域的知识是身份和网络实体之间的相互关系，因此框架模型是很自然的方式来存储这些信息并为相关实体间传播的限制合理的基础。
对于MAPCon来说框架最重要的特点是模块化，连通性，继承性和可论证性。MAPCon在网络模型构建中交互指导用户。每个网络实体（包括子网，站点，如路由器或桥中间系统，以及连接点）对应一个CRL框架，它的可配置参数在框架插槽。
3.1.2.规则和程序化知识
在传统的专家系统，规则是用来捕捉启发式，浅薄的人类专家的知识。虽然一些MAPCon规则支持这个功能，但大部分约束关系在代表MAP网络元素的对象槽中。有些关系可以通过对象之间的继承约束。在其他情况下，特别是当一个元素多个参数互动。在其余情况下，简单的规则允许的，否则可能需要复杂，容易出错，而且难以修改程序代码的相互依存关系的声明规范。例如，指定的网络管理员验证可能需要搜索多个子网互联和更容易理解和贯彻作为一个比一个广泛的（程序），通过模型语义搜索（声明）规则。
3.2.合成与分析
这是非常有用的区分两类推理的目标：合成和分析。像其他许多现实世界的系统，MAPCo n做着两种工作，在适当的时候在它们之间切换。
综合问题的基本要求，因为一组元素和这些元素之间的约束集，从分子组装结构，满足的约束。所谓“规划”是经常被用来描述这种松散的过程中，虽然我们宁愿保留一个更具体的情况下。我们区分三种主要类型
合成，这在数据用于表示其约束时间不同。因此，我们可以定义配置，如标称时间合成，在合成时间为序数严格意义上的规划，并作为综合调度间隔时间。
分析，首先是一个已知的结构以及与它的行为和因素使得它关系的原因。这两个主要分析形式是预测，从结构和它的元素的行为向整个行为，和解释，这从结构上的原因和理由。
MAPCon主要是一个综合系统，执行的名义时域静态配置。MAF'Con相互依存的价值确定为62，每个配置元素，MAP网络（站或连接点）的可配置参数被建模。
4.性能
一个专家系统的表现，可在如何好，如何迅速在执行其任务方面均。这也是有趣的纪录注意到需要建立一个应用程序的自定义代码的数量之间
的领域和知识工程的环境匹配。
4.1.MAPCon执行得如何？
WCon的任务是确定是否在一个给定的网络组件的配置参数可以与另一个相互一致，如果他们能，以执行该配置。它的结构就是这样，它总是很成功的配置一个可配置的网络，并适当的标记一个不可配置的网络。因此，它能够很好的执行它的任务。
4.2.MAPCon执行有多快？
因为专家系统往往是在复杂的领域，遭受组合应用，所以了解他们的速度性能作为问题规模的函数是非常重要的。尽管分析的复杂性界限可能是在一些简单的情况下可以，但是最直接的方式来评估一个全面系统的高速性能，是收集它的执行统计信息。
Lesson One: The Time Message Elwood N, Chapman 新的学习任务开始之际，千头万绪，最重要的是安排好时间，做时间的主人。本文作者提出了7点具体建议，或许对你有所启迪。 1 Time is tricky. It is difficult to control and easy to waste. When you look a head, you think you have more time than you need. For Example,at the beginning of a semester, you may feel that you have plenty of time on your hands, but toward the end of the term you may suddenly find that time is running out. You don't have enough time to cover all your duties (duty), so you get worried. What is the answer? Control! 译：时间真是不好对付，既难以控制好，又很容易浪费掉，当你向前看时，你觉得你的时间用不完。例如，在一个学期的开始，你或许觉得你有许多时间，但到学期快要结束时，你会突然发现时间快用光了，你甚至找不出时间把所有你必须干的事情干完，这样你就紧张了。答案是什么呢？控制。 2 Time is dangerous. If you don't control it, it will control you. I f you don't make it work fo r you, it will work against you. So you must become the master of time, not its servant. As a first-year college student, time management will be your number one Problem. 译：时间是危险的，如果你控制不了时间，时间就会控制你，如果你不能让时间为你服务，它就会起反作用。所以，你必须成为时间的主人，而不是它的奴仆，作为刚入学的大学生，妥善安排时间是你的头等大事。 3 Time is valuable. Wasting time is a bad habit. It is like a drug. The more time you waste,the easier it is to go on wasting time. If seriously wish to get the most out of college, you must put the time message into practice. 译：时间是珍贵的，浪费时间是个坏习惯，这就像毒品一样，你越浪费时间，就越容易继续浪费下去，如果你真的想充分利用上大学的机会，你就应该把利用时间的要旨付诸实践。 Message1. Control time from the beginning. 4 Time is today, not tomorrow or next week. Start your plan at the Beginning of the term. 译：抓紧时间就是抓紧当前的时间，不要把事情推到明天或是下周，在学期开始就开始计划。 Message2. Get the notebook habit. 5 Go and buy a notebook today, Use it to plan your study time each day. Once a weekly study plan is prepared, follow the same pattern every week with small changes. Sunday is a good day to make the Plan for the following week.
Exploring Filipino School Counselors’ Beliefs about Learning Allan B. I. Bernardo [Abstract] School reform efforts that focus on student learning require school counselors to take on important new roles as advocates of student learning and achievement.But how do school counselors understand the process of learning? In this study, we explore the learning beliefs of 115 Filipino school counselors who indicated their degree of agreementwith 42 statements about the process of learning and the factors thatinfluence this process.A principal components analysis of the responses to the 42 statements suggested three factors:(F1)social-cognitive constructivist beliefs, (F2) teacher-curriculum-centered behaviorist beliefs,and (F3) individual difference factors.The preliminary results are briefly discussed in terms of issues related to how Filipino school counselors’ conceptions of learning may guide their strategies for promoting student learning and achievement. [Key words]beliefs about learning, conceptions of learning, school counselors, student learning, Philippines School reform efforts in different parts of the world have focusedon students’learning. In particular,most school improvement programsnow aim to ensure that students acquire the high-level knowledge and skills that help them to thrive in today’s highly competitive globaleconomy (e.g., Lee & Williams, 2006). I n this regard, school reform programs draw from various contemporary theories and research on learning (e.g.,Bransford,Brown, & Cocking, 1999; Lambert & McCombs, 1998).The basic idea is that all school improvement efforts should be directed at ensuring students achieve high levels of learning or attainment of well-defined curricular objectives and standards.For example, textbooks (Chien & Young, 2007), computers and educational technology (Gravoso, 2002; Haertnel & Means, 2003;Technology in Schools Task Force, 2003), and educational assessment systems (Black & Wiliam2004; Cheung & Ng, 2007; Clark, 2001; Stiggins, 2005) are being reconsidered as regards how they can effectively provide scaffolds and resources for advancing student learning. Likewise,the allocation and management of a school’s financial resources are assessed in terms ofwhether these are effectively mobilized and utilized towards improving student learning (Bolam, 2006; Chung & Hung, 2006; Retna, 2007). In this regard, some advocates have also called for an examination of the role of school counselors in these reform efforts (Herr, 2002). Inthe United States, House and Hayes (2002) challenged school counselors to take proactive leadership roles in advocating for the success of all
https://www.doczj.com/doc/204468636.html,/finance/company/consumer.html Consumer finance company The consumer finance division of the SG group of France has become highly active within India. They plan to offer finance for vehicles and two-wheelers to consumers, aiming to provide close to Rs. 400 billion in India in the next few years of its operations. The SG group is also dealing in stock broking, asset management, investment banking, private banking, information technology and business processing. SG group has ventured into the rapidly growing consumer credit market in India, and have plans to construct a headquarters at Kolkata. The AIG Group has been approved by the RBI to set up a non-banking finance company (NBFC). AIG seeks to introduce its consumer finance and asset management businesses in India. AIG Capital India plans to emphasize credit cards, mortgage financing, consumer durable financing and personal loans. Leading Indian and international concerns like the HSBC, Deutsche Bank, Goldman Sachs, Barclays and HDFC Bank are also waiting to be approved by the Reserve Bank of India to initiate similar operations. AIG is presently involved in insurance and financial services in more than one hundred countries. The affiliates of the AIG Group also provide retirement and asset management services all over the world. Many international companies have been looking at NBFC business because of the growing consumer finance market. Unlike foreign banks, there are no strictures on branch openings for the NBFCs. GE Consumer Finance is a section of General Electric. It is responsible for looking after the retail finance operations. GE Consumer Finance also governs the GE Capital Asia. Outside the United States, GE Consumer Finance performs its operations under the GE Money brand. GE Consumer Finance currently offers financial services in more than fifty countries. The company deals in credit cards, personal finance, mortgages and automobile solutions. It has a client base of more than 118 million customers throughout the world
GRA VITY RETAINING?WALL 1. INTRODUCTION Retaining walls are structures used to provide stability for earth or other material where conditions disallow the mass to assume its natural slope, and are commonly used to hold back or support soilbanks,coal or ore piles, and water. Retaining walls are classified, based on the method of achieving stability, into six principal types (Fig.1). The gravity-wall depends upon its weight, as the name implies, for stability. The cantilever wall is a reinforced-concrete wall that utilizes cantilever action to retain the mass behind the wall from assuming a natural slope. Stability of this wall is partially achieved from the weight of soil on the heel portion of the base slab. A counterfort retaining wall is similar to a cantilever retaining wall, except that it is used where the cantilever is long or for very high pressures behind wall and has counterforts, which tie the wall and base together, built at intervals along the wall to reduce the bending moments and sheers. As indicated in Fig.1c, the counterfort is behind the wall and subjected to tensile forces. A buttressed retaining wall is similar to a counterfort wall, except that the bracing is in front of the wall and is in compression instead of tension. Two other types of walls not considered further are crib walls, which are built-up members of pieces of precast concrete, metal, or timber and are supported by anchor pieces embedded in the soil for stability, and semigravity walls, which are walls intermediate between a true gravity and a cantilever wall. (a)(b)(e)
高速视频处理系统中的信号完整性分析 摘要：结合高速DSP图像处理系统讨论了高速数字电路中的信号完整性问题，分析了系统中信号反射、串扰、地弹等现象破坏信号完整性的原因，通过先进IS工具的辅助设计，找出了确保系统信号完整性的具体方法。 关键词：高速电路设计信号完整性 DSP系统 深亚微米工艺在IC设计中的使用使得芯片的集成规模更大、体积越来越小、引脚数越来越多；由于近年来IC工艺的发展，使得其速度越来越高。从而，使得信号完整性问题引起电子设计者广泛关注。 在视频处理系统中，多维并行输入输出信号的频率一般都在百兆赫兹以上，而且对时序的要求也非常严格。本文以DSP图像处理系统为背景，对信号完整性进行准确的理论分析，对信号完整性涉及的典型问题[1]——不确定状态、传输线效应、反射、串扰、地弹等进行深入研究，并且从实际系统入手，利用IS仿真软件寻找有效的途径，解决系统的信号完整性问题。 1 系统简介 为了提高算法效率，实时处理图像信息，本图像处理系统是基于DSP+FPGA结构设计的。系统由SAA7111A视频解码器、TI公司的TMS320C6701 DSP、Altera公司的EPlK50QC208 FPGA、PCI9054 PCI接口控制器以及SBRAM、SDRAM、FIFO、FLASH等构成。FPGA是整个系统的时序控制中心和数据交换的桥梁，而且能够对图像数据实现快速底层处理。DSP是整个系统实时处理高级算法的核心器件。系统结构框图如图1所示。 在整个系统中，PCB电路板的面积仅为15cm×l5cm，系统时钟频率高达167MHz，时钟沿时间为0．6ns。由于系统具有快斜率瞬变和极高的工作频率以及很大的电路密度，使得如何处理高速信号问题成为一个制约设计成功的关键因素。 2 系统中信号完整性问题及解决方案 2．1 信号完整性问题产生机理 信号的完整性是指信号通过物理电路传输后，信号接收端看到的波形与信号发送端发送的波形在容许的误差范围内保持一致，并且空间邻近的传输信号间的相互影响也在容许的范围之内。因此，信号完整性分析的主要目标是保证高速数字信号可靠的传输。实际信号总是存在电压的波动，如图2所示。在A、B两点由于过冲和振铃[2]的存在使信号振幅落入阴影部分的不确定区，可能会导致错误的逻辑电平发生。总线信号传输的情况更加复杂，任何一个信号发生相位上的超前或滞后都可能使总线上数据出错，如图3所示。图中，CLK为时钟信号，D0、D1、D2、D3是数据总线上的信号，系统允许信号最大的建立时间[1]为△t。在正常情况下，D0、D1、D2、D3信号建立时间△t1<△t，在△t时刻之后数据总线的数据已稳定，系统可以从总线上采样到正确的数据，如图3(a)所示。相反，当信号D1、D2、D3受过冲和振铃等信号完整问题干扰时，总线信号就发生
Lesson 1 I’m not feeling well. Let’s talk （M=Mom, T= Tom） M: What,'s the matter, Tom T: I'm not feeling well, Mom M: Do you have a cold T: Yes, I think so. Could you give me some water, please M: Here you are. T: Thank you, Mom. M: Tom, you must go and see a doctor. T: OK, Mom. M: It's cold outside. You must wear your coat. T: OK, Mom. Could you pass me my coat,please M: Here you are. T: Thank you, Mom M: Tell me your teacher's number. I'll call him and tell him you are sick. T: OK. Here it is. 译文 (M=妈妈,T=汤姆) 妈妈:怎么了,汤姆 汤姆:我感觉不舒服,妈妈。 妈妈:你感冒了吗 汤姆:是的,我想是这样的。您能给我一些水吗 妈妈:给你。 汤姆:谢谢您,妈妈。 妈妈:汤姆,你必须去看医生. 汤姆:好的,妈妈。 妈妈:外面很冷。你必须穿你的外套。 汤姆:好的,妈妈。您能把我的外套递给我吗 妈妈:给你。 汤姆:谢谢您,妈妈。 妈妈:告诉我你老师的电话号码。我将给他打电话告诉他你生病了。
文档简介 一，英语翻译经典文章之英文原稿二，中文翻译：这篇英语文章的最好翻译版本！不是俺说的，是俺老师说哒！！ 英文原稿Brian It seems my only request (“please, let me sleep”) is not clear enough, so I made this simple table that can help you when you’re in doubt. Especially during the night
中文翻译小子： 我只想好好地睡觉，你不明白吗？！所以，我做了这个简表。当你不知道怎么办时，特 别是在晚上的时候，你可以看看它。 具体情况行动指南 1，我正在睡觉禁止进入 2，你不确定我是否睡觉，你想搞清楚管你“鸟”事；禁止进入 3，你嗑了药，想奔向我的床你他妈的滚远点 4，你在youtube上看了一个超赞的视频，禁止进入；在脸书上把链接发给我想让我看看 5，就算第三次世界大战开始了管我屁事，他妈的别进来 6，你和你的基友们想和我“玩玩”抱歉，直男一枚。不要碰我的任何东西，门都别碰 7，你想整理我的房间我谢谢你了！我自己会打扫 8，普京宣布同性婚姻合法化终于等到“它”！还好你没放弃！还是不要来我房里！ 9，我不在家进我房间，想都别想 10，白天，我在家。你敲了门，我说“请进” 你可以进来了 福利放送！！
如果你已经看到了这里，那么说明你应该是英文爱好者哦。 下面有一些非常实用，我精心整理的英文资料，你一定用得到！快去看看吧！ 一，最常用英语翻译政治文体句型总结大全完美版 二，英文合同翻译最常用句型总结专业版 三，英语毕业论文提纲模板优秀完整详细无敌版
南京师范大学泰州学院 英文翻译原文 年级： 2011级学号：12110330 姓名：申佳佳 系部：信息工程学院 专业：通信工程 题目：基于C51的数字测速仪设计与仿真 指导教师：焦蓬蓬 2015 年 4 月 5 日
Linux - Operating system of cybertimes Though for a lot of people , regard Linux as the main operating system to make u p huge work station group, finish special effects of " Titanic " make , already can be re garded as and show talent fully. But for Linux, this only numerous news one of. Rece ntly, the manufacturers concerned have announced that support the news of Linux to i ncrease day by day, users' enthusiasm to Linux runs high unprecedentedly too. Then, Linux only have operating system not free more than on earth on 7 year this piece wh at glamour, get the favors of such numerous important software and hardware manufa cturers as the masses of users and Orac le , Informix , HP , Sybase , Corel , Intel , Net scape , Dell ,etc. , OK? 1.The background of Linux and characteristic Linux is a kind of " free (Free ) software ": What is called free, mean users can o btain the procedure and source code freely , and can use them freely , including revise or copy etc.. It is a result of cybertimes, numerous technical staff finish its research a nd development together through Inte rnet, countless user is it test and except fault , c an add user expansion function that oneself make conveniently to participate in. As th e most outstanding one in free software, Linux has characteristic o f the following: (1)Totally follow POSLX standard, expand the network operating system of sup porting all AT&T and BSD Unix characteristic. Because of inheritting Unix outstandi ng design philosophy , and there are clean , stalwart , high-efficient and steady kernels , their all key codes are finished by Li nus Torvalds and other outstanding programmer s, without any Unix code of AT&T or Berkeley, so Linu x is not Unix, but Linux and Unix are totally compatible. (2)Real many tasks, multi-user's system, the built-in n etwork supports, can be with such seamless links as NetWare , Windows NT , OS/2 , Unix ,etc.. Network in various kinds of Unix it tests to be fastest in comparing and ass ess efficiency. Support such many kinds of files systems as FAT16 , FAT32 , NTFS , E x t2FS , ISO9600 ,etc. at the same time .
Basic Control Actions and Industrial Automatic Control An automatic controller compares the actual value of the plant output with the desired value, determines the deviation, and produces a control signal which will reduce the deviation to zero or to a small value.The manner in which the automatic conroller produces the control signal is called the control action. Classifications of industrial automatic controllers Induetrial automatic controllers may be classified according to their control action as: ·two-position or on-off controllers; ·proportional controllers; ·integral controllers; ·proportional-plus-integral controllers; ·proportional-plus-derivative controllers; ·proportional-plus-derivative-plus-integral controllers. Most industrial automatic controllers use eletricity or pressurized fluid such as oil or air as power sources. Automatic controllers may also be classified according to the kind of power employed in the operation, such as pneumatic controllers, hydraulic controllers, or electronic controllers.What kind of controller to use must be decided by the nature of the plant and the operating conditions,including such considerations as safety, availability, reliability, accuracy, weight, and size? Elements of industrial automatic controllers An automatic controller must detect the actuating error signal, which is usually at a very low power level, and amplify it to a sufficiently high level. Thus, an amplifier is necessary. The output of an automatic controller is fed to a power device, such as a pneumatic motor or valve, a hydraulic motor, or an electric motor. The controller usually consists of an error detector and amplifier. The measuring element is a device that converts the output variable into another suitable variable, such as a displacement, pressure, or electric signal, which can be used for comparing the output to the reference input signal. This element is in the feedback path of the closed-loop system. The set point of the controller must be converted to a reference input of the same units as the feedback signal from the measuring element. The amplifier amplifies the power of the actuating error signal, which in turn operates the actuator. The actuator is an element which alters the input to the plant according to the control signal so that the feedback signal may be brought into correspondence with the reference input signal. Self-operated controllers In most industrial automatic controllers, separate units are used for the measuring element and for the actuator. In a very simple one, however, such as a self-operated controller, these elements are assembled in one unit. Self-operated controllers utilize power developed by the measuring element and are very simple and inexpensive. The set point is determined by the adjustment of the spring force. The controlled pressure is measured by the diaphragm. The actuating error signal is the net force acting on the diaphragm. Its position determines the valve opening. The operation of self-operated controller is as follows: Suppose that the output pressure is lower than the reference pressure, as determined by the set point. Then the downward spring force is greater than the upward pressure force, resulting in a downward movement of the diaphragm. This increases the flow rate and raises the output pressure.
Engineering with Computers(2002)18:109–115 Ownership and Copyright ?2002Springer-Verlag London Limited Structural Optimization of Automotive Body Components Based on Parametric Solid Modeling M.E.Botkin GM R&D Center,Warren,MI,USA Abstract Abstract::Parametric modeling was used to build several models of an automotive front structure concept that utilizes carbon fiber composite materials and the corresponding molding processes.An ultra-lightweight aluminum body front structure was redesigned to include an all-composite front structure.Two alternative concepts were studied which represent the structure as a bonded assembly of shells.Closed sections result from two pieces–an inner and outer.Parametric modeling was found to be a useful tool for building and modifying models to use in optimization concept studies. Such models can be built quickly and both the sketch dimensions and location dimensions are particularly useful for making the adjustments necessary to fit the various body pieces together.The parametric models then must be joined together as one geometric solid model in order to obtain a surface mesh.Structural optimization input data can then be seamlessly and quickly created from the parametric-modelbased finite element model to begin the tradeoff studies.This integrated process in which parametric modeling was coupled with structural optimization was used to carry out design studies on the lightweight body front structure.Several carbon fiber material combinations were studied to determine mass reduction potential of certain types of carbon fiber products considered to be lower cost than typical carbon fiber materials used in the past.Structural optimization was used to compare several composite constructions for the design of the bonded front structure.Eight cases were studied using various materials and composite lay-ups.Mass savings estimates from45–64%over steel were obtained.The most reasonable design consisted of a combination of relatively low cost chopped carbon fiber and woven carbon fiber and using a20mm balsa core in the top of the shock tower area. This design had a maximum thickness of7mm and a mass reduction over steel of approximately62%.Correspondence and offprint requests to:Mark E.Botkin,Principal