Chapter 07 雷蒙德第七版_Human_Resource_Management
Chapter 07
Performance Management
True / False Questions
1. Visible support of the performance management process by the CEO and senior management ensures that the system is consistently used across the company.
True False
2. The initial steps of the performance management cycle include the employee and manager identifying what the employee can do to capitalize on performance strengths.
True False
3. A performance management system should link employee activities with the organization's goals. This is its developmental purpose.
True False
4. Validity refers to the consistency of a performance measure.
True False
5. The extent to which a performance measure is deemed to be satisfactory or adequate by those who use it is known as its acceptability.
True False
6. Acceptability is affected by the extent to which employees believe the performance management system is fair.
True False
7. Alternation ranking require managers to rank employees within their departments from highest performer to poorest performer.
True False
8. Comparative techniques of performance management virtually eliminate the problems of leniency, central tendency, and strictness.
True False
9. Quality-based performance methods are quite easy to develop and are generalizable across a variety of jobs, strategies, and organizations.
True False
10. Behavior-based performance methods are the most popular performance evaluation approaches in organizations.
True False
11. A behaviorally anchored rating scale is designed to specifically define performance dimensions by developing behavioral anchors associated with different levels of performance.
True False
12. An advantage of behaviorally anchored rating scales is increased interrater reliability.
True False
13. Competencies are sets of skills, knowledge, abilities, and personal characteristics that enable employees to successfully perform their jobs.
True False
14. Result-based approaches to performance measurement assume that subjectivity can be eliminated from the measurement process.
True False
15. Productivity measurement and evaluation system (ProMES) is designed to specifically define performance dimensions by developing behavioral anchors associated with different levels of performance.
True False
16. A disadvantage of the result-based approaches to performance measurement is that individuals may focus only on aspects of their performance that are measured, neglecting those that are not.
True False
17. The assumption of Pareto analysis is that the majority of problems are the result of a small number of causes.
True False
18. The quality approach relies primarily on a combination of the attribute and results approaches to performance measurement.
True False
19. Subordinates are the most frequently used source of performance information.
True False
20. The best use of self-ratings is for administrative purposes.
True False
21. A major advantage of the 360-degree appraisal is that it provides a means for minimizing bias in an otherwise subjective evaluation technique.
True False
22. Central tendency as a rating error reflects that a rater gives high ratings to all employees regardless of their performance.
True False
23. Appraisal politics refer to evaluators purposefully distorting a rating to achieve personal or company goals.
True False
24. Once the expected performance has been defined and employees' performances have been measured, it is necessary to feed that performance information back to the employees so that they can correct any deficiencies.
True False
25. Output is a factor to consider in analyzing poor performance.
True False
Multiple Choice Questions
26. _____ is the means through which managers ensure that employees' activities and outputs are congruent with the organization's goals.
A. Performance feedback
B. Performance results
C. Performance management
D. Performance appraisal
E. Performance strategy
27. The process through which an organization gets information on how closely an employee's actual performance met the performance plan is _____.
A. performance appraisal
B. performance management
C. performance feedback
D. ability analysis
E. achievement discrepancy
28. _____ is the process of providing employees information regarding their performance effectiveness.
A. Performance appraisal
B. Achievement discrepancy
C. Performance management
D. Ability analysis
E. Performance feedback
29. Which of the following is the first step in the process of performance management?
A. Develop employee goals behavior, and actions to achieve outcomes.
B. Define performance outcomes for company division and department.
C. Provide consequences for performance results.
D. Identify the improvements needed.
E. Provide support and ongoing performance discussions.
30. Which of the following fulfills the administrative purpose of performance management?
A. Define the results, behaviors, and, to some extent, employee characteristics that are necessary.
B. Develop employees who are effective at their jobs.
C. Use performance appraisal to make decisions such as pay raises, promotions, retention-termination, layoffs, and recognition of individual performance.
D. Identify employees' strengths and weaknesses, link employees to appropriate training and development activity.
E. Confront employees with their performance weaknesses.
31. _____ is the extent to which the performance management system elicits job performance that is consistent with the organization's strategy, goals, and culture.
A. Specificity
B. Reliability
C. Validity
D. Strategic congruence
E. Acceptability
32. _____ are factors in a company's business strategy that give it a competitive edge.
A. KRIs
B. CSFs
C. NDAs
D. KPIs
E. 360-degree appraisals
33. Which performance management evaluation criterion is the extent to which a performance measure assesses all the relevant—and only the relevant—aspects of performance?
A. Reliability
B. Strategic congruence
C. Acceptability
D. Specificity
E. Validity
34. A(n) _____ measure evaluates irrelevant aspects of performance or aspects that are not job related.
A. unreliable
B. unacceptable
C. contaminated
D. inconsistent
E. unspecified
35. A university assesses its faculty members more on their research work than their teaching abilities. Which of the following measures of the performance management process is it using?
A. Deficient
B. Contaminated
C. Unreliable
D. Inconsistent
E. Unspecified
36. The consistency among the different individuals who evaluate the employee's performance is known as _____.
A. internal consistency reliability
B. interrater reliability
C. inter-method reliability
D. test-retest reliability
E. parallel-forms reliability
37. A measure that results in dramatically different ratings over time lacks _____.
A. internal consistency reliability
B. interrater reliability
C. parallel-forms reliability
D. test-retest reliability
E. inter-method reliability
38. Which of the following statements about acceptability is true?
A. It is the extent to which the performance management system elicits job performance that is consistent with the organization's strategy, goals, and culture.
B. It is the extent to which a performance measure gives detailed guidance to employees about what is expected of them and how they can meet these expectations.
C. It is the extent to which a performance measure assesses all the relevant—and only the relevant—aspects of job performance.
D. It is the degree to which a performance measure is free from random error.
E. It is the extent to which a performance measure is deemed to be satisfactory or adequate by those who use it.
39. The extent to which the performance measure gives guidance to employees about what is expected of them is called _____.
A. reliability
B. validity
C. specificity
D. acceptability
E. strategic congruence
40. Which of the following approaches to measuring performance uses some overall assessment of an individual's performance or worth and seeks to develop a ranking of the individuals within a work group?
A. The results approach
B. The attribute approach
C. The comparative approach
D. The consequential approach
E. The behavior approach
41. _____ consists of a manager looking at a list of employees, deciding who the best employee is, and crossing that person's name off the list.
A. Simple ranking
B. Alternation ranking
C. Reverse ranking
D. Probability distribution
E. Forced distribution
42. The technique that ranks employees into predetermined categories or groups according to performance is called _____.
A. forced distribution
B. high/low ranking system
C. paired comparison
D. strictness
E. simple ranking
43. The _____ method requires managers to compare every employee with every other employee in the work group, giving an employee a score of 1 every time he/she is considered the high performer.
A. partner measurement
B. mixed-standard scales
C. forced distribution
D. paired comparison
E. alternate ranking
44. Intech is a company that sells PCs and laptops. The company is projecting an increase in sales in the next six months and is looking at filling senior positions through internal recruiting to meet this demand. The company will evaluate individual performances and seek to develop some ranking of the individuals within a work group to identify the highest performer. This will help them arrive at a decision. Which of the following approaches is the company using?
A. The results approach
B. The attribute approach
C. The comparative approach
D. The behavioral approach
E. The quality approach
45. The _____ to performance management focuses on the extent to which individuals have certain characteristics or traits believed desirable for the company's success.
A. results approach
B. quality approach
C. behavioral approach
D. comparative approach
E. attribute approach
46. Which of the following attribute approaches to performance management is most commonly used?
A. Behaviorally anchored rating scales
B. Mixed standard scales
C. Behavior observation scales
D. Graphic rating scales
E. Simple ranking scales
47. In the graphic rating scale, the manager:
A. defines performance dimensions by developing behavioral anchors associated with different levels of performance.
B. defines the relevant performance dimensions and then develops statements representing good, average, and poor performance along each dimension.
C. considers one employee at a time, circling the number that signifies how much of that trait the individual has.
D. identifies and provides descriptions of competencies that are common for an entire occupation, organization, job family, or a specific job.
E. is required to compare every employee with every other employee in the work group, giving an employee a score of 1 every time he or she is considered the higher performer.
48. In which performance technique are managers given three statements of performance per dimension and asked to indicate whether the employee's performance is above (+), at (0), or below (-) the statements?
A. Behaviorally anchored rating scale
B. Forced distribution
C. Behavior observation scale
D. Graphic rating scale
E. Mixed-standard scale
49. Which of the following is true about the attribute approach to performance management?
A. There is usually high congruence between these techniques and the company's strategy.
B. These methods usually have very clear performance standards because of which different raters provide similar ratings and rankings.
C. They are easy to develop and are generalizable across organizations and strategies.
D. They provide specific guidance and feedback to employees.
E. These techniques tend to reduce defensiveness in employees during feedback.
50. The techniques of which of the following approaches to performance management lack specificity for feedback purposes?
A. The quality approach
B. The comparative approach
C. The behavioral approach
D. The attribute approach
E. The results approach
51. Which performance management technique involves the identification of a large number of critical incidents, the classification of these incidents into performance dimensions, and the rank ordering of these incidents into levels of performance?
A. Behaviorally anchored rating scales
B. Graphic rating scales
C. Comparative rating scales
D. Organizational behavior modification
E. Competency models
52. The performance management method that requires managers to rate the frequency with which the employee has exhibited a behavior during a rating period is the _____.
A. simple ranking method
B. behavioral observation scale
C. graphic rating scale
D. organizational behavior modification method
E. forced distribution scale
53. A(n) _____ identifies and provides descriptions of competencies that are common for an entire occupation, organization, job family, or a specific job.
A. OSI model
B. mixed-standard scale
C. behavioral observation scale
D. competency model
E. layered model
54. Which of the following is true regarding behavioral approaches to performance measurement?
A. They link strategy to specific behavior needed to implement strategy.
B. They do not provide specific guidance to employees regarding expected performance.
C. They result in techniques that have a low degree of validity and acceptability.
D. The approach assumes that there are multiple best ways to do the job.
E. Despite substantial investments in training, the techniques are not strong enough to be reliable.
55. The _____ assumes that subjectivity can be eliminated from the measurement process and that results are the closest indicator of one's contribution to organizational effectiveness.
A. behavior approach
B. results approach
C. attribute approach
D. quality approach
E. comparative approach
56. Which of the following is a means of measuring and feeding back productivity information to personnel with the main goal of motivating employees to higher levels of productivity?
A. Management by objectives
B. ProMES
C. Assessment centers
D. Critical incidents
E. Multi-criteria decision analysis
57. Which of the following is the first step in the ProMES system?
A. The staff defines indicators of the products to measure how well the products are being
B. The management develops a feedback system that provides employees and work groups with information about their specific level of performance.
C. People in the organization identify the set of activities or objectives the organization expects to accomplish.
D. The employee and manager identify what the employee can do to capitalize on performance strengths.
E. The staff establishes the contingencies between the amount of the indicators and the level of evaluation associated with that amount.
58. Which of the following is true about the results approach to performance management?
A. The results approach relies primarily on a combination of the attribute and results approaches to performance measurement.
B. The results approach virtually eliminates problems of leniency, central tendency, and strictness.
C. The techniques of the results approach usually have very little congruence with the company's strategy.
D. The results approach is usually highly unacceptable to both managers and employees.
E. The results approach minimizes subjectivity, relying on objective, quantifiable indicators of performance.
59. Which of the following is an advantage of the results approach?
A. It can increase interrater reliability by providing a precise and complete definition of the performance dimension.
B. It provides a means for minimizing bias in an otherwise subjective evaluation technique.
C. It links an individual's results with the organization's strategies and goals.
D. It helps employees learn how they need to change their behavior to increase their
E. It does not permit objective measurements to get contaminated or deficient.
60. A performance management system designed with a strong quality orientation can be expected to:
A. emphasize an assessment of system factors in the measurement system, but not of the person factors.
B. emphasize that managers and employees work separately to solve performance problems.
C. involve only the external customers in setting standards and measuring performance.
D. use multiple sources to evaluate person and system factors.
E. share the financial rewards of successes with employees according to how much they have contributed to them.
61. Advocates of the quality approach believe that most U.S. companies' performance management systems are incompatible with the quality philosophy for a number of reasons. Which one of the following is among these reasons?
A. Most existing systems measure performance in terms of quality, not quantity.
B. They involve both internal and external customers in setting standards and measuring performance.
C. Companies share financial rewards of successes with employees according to how much they have contributed to them.
D. Rewards are connected to business results and profits.
E. Employees are held accountable for good or bad results to which they contribute but do not completely control.
62. _____ refers to practices participated in by employees from all levels of the company that focus on continuous improvement of business processes.
A. Quality circle
B. Muda
C. Kaizen
D. Root cause analysis
E. Business process reengineering
63. Which of the following statistical process quality control techniques helps identify redundancies in jobs that increase manufacturing or service time?
A. Cause-and-effect diagrams
B. Control charts
C. Pareto charts
D. Process-flow analysis
E. Histograms
64. A _____ is a quality control technique that lists causes of a problem in decreasing order of importance.
A. cause-and-effect diagram
B. control chart
C. Pareto chart
D. process-flow analysis
E. histogram
65. Which quality control technique is useful for understanding the amount of variance between an outcome and the expected value or average outcome?
A. A control chart
B. A histogram
C. A cause-and-effect diagram
D. A process-flow analysis
E. A Pareto chart
66. Which of the following observations is true about scattergrams?
A. They help in identifying the most important cause of a problem.
B. They are useful for understanding the amount of variance between an outcome and the expected value or average outcome.
C. They help employees determine whether the relationship between two variables or events is positive, negative, or zero.
D. They assume that that the majority of problems are the result of a small number of causes.
E. They are useful for identifying redundancy in processes that increase manufacturing or service time.
67. Which of the following is true about the quality approach to performance measurement?
A. The quality approach techniques usually have very little congruence with the strategic goals of an organization.
B. The quality approach has very low acceptability because they are usually developed without input from those to be evaluated.
C. The quality approach advocates evaluation of personal traits, which are easier to relate to job performance.
D. The quality approach adopts a systems-oriented focus, while traditional performance appraisal systems focus more on individual employee performance.
E. The quality approach relies primarily on a combination of the behavior and results approaches to performance measurement.
68. Both, the comparative and the attribute approaches to performance measurement are _____.
A. high on strategic congruence
B. very low on specificity
C. low on acceptability
D. high on reliability
E. very high on validity
69. Which of the following sets of approaches to performance measurement have very similar levels of performance measure criteria?
A. Comparative and attribute
B. Attribute and behavioral
C. Behavioral and comparative
D. Results and quality
E. Attributes and results
70. Which of the following approaches to performance measurement minimizes contamination and deficiency?
A. The comparative approach
B. The attribute approach
C. The behavioral approach
D. The results approach
E. The quality approach
71. _____ are the most frequently used source of performance information.
A. Peers
B. Managers
C. Subordinates
D. Employees themselves
E. Customers
72. Which of the following is true of peers as the source for performance information?
A. Peers have expert knowledge of job requirements and often have the most opportunity to observe the employee in day-to-day activities.
B. Peer evaluations give employees power over their managers, thus putting the manager in a difficult situation.
C. Peers are comfortable providing evaluations for both administrative and developmental purposes.
D. Peers have the ability to discard the fact that they may be friends with the ratees in order to provide an unbiased rating.
E. Feedback from peers is strongly related to performance and to employee perceptions of the accuracy of the appraisal.
73. _____ are a valuable source of performance information when managers are being evaluated and often have the best opportunity to evaluate how well a manager treats employees.
A. Supervisors
第7章 二阶电路总结
第七章 二阶电路 用二阶线性常微分方程描述的电路称为二阶电路，二阶电路中至少含有两个储能元件——当然含有两个储能元件的电路并不一定为二阶电路，比如两个电容（电感）串（并）联情况。 ◆ 重点： 1． 电路微分方程的建立 2． 特征根的重要意义 3． 微分方程解的物理意义 ◆ 难点： 1． 电路微分的解及其物理意义 2． 不同特征根的讨论计算 7.0 知识复习 一、二阶齐次微分方程的通解形式 0'''=++cy by ay ，其特征方程为：02 =++c bp ap ，特征根： a ac b a b p 4422 2,1-± - =。 当特征方程有不同的实根1p 、2p 时，t p t p e A e A y 2121+= 当特征方程有相同的实根p 时，pt e t A A y )(21+= 当特征方程有共轭的复根ω±δ-=j p 2,1时， )sin cos (21)(t A t A e e y t t j ω+ω==δ-ω+δ- 二、欧拉公式 β+β=β sin cos j e j 2 )sin() () (j e e t t j t j β+ω-β+ω-= β+ω β-β=β -sin cos j e j 2 )cos() () (β+ω-β+ω+= β+ωt j t j e e t 7.1 二阶电路的零输入响应 7.1.1 二阶电路中的能量振荡 在具体研究二阶电路的零输入响应之前，我们以仅仅含电容与电感的理想二阶电路（即R=0，无阻尼情况）来讨论二阶电路的零输入时的电量及能量变化情况。
+ U 0 C L _ - _ C L 0 + (d) 图8-1 L C 电路中的能量振荡 设电容的初始电压为0U ，电感的初始电流为零。在初始时刻，能量全部存储于电容中，电感中没有储能。此时电流为零，电流的变化率不为零（0 ≠==dt di L u u L C ，0 ≠∴dt di ），这样电流将不断增大，原来存储在电容中的电能开始转移，电容的电压开始逐渐减小。当电容电压下降到零时，电感电压也为零，此时电流的变化率也就为零，电流达到最大值I 0，此时电场能全部转化为电磁能，存储在电感中。 电容电压虽然为零，但其变化率不为零（0 0≠===dt du C I i i C L C ，0 ≠∴dt du C ），电 路中的电流从I 0逐渐减小，电容在电流的作用下被充电（电压的极性与以前不同），当电感中的电流下降到零的瞬间，能量再度全部存储在电容中，电容电压又达到，只是极性与开始相反。 之后电容又开始放电，此时电流的方向与上一次电容放电时的电流方向相反，与刚才的过程相同，能量再次从电场能转化为电磁能，直到电容电压的大小与极性与初始情况一致，电路回到初始情况。 上述过程将不断重复，电路中的电压与电流也就形成周而复始的等幅振荡。 可以想象，当存在耗能元件时的情况。一种可能是电阻较小，电路仍然可以形成振荡，但由于能量在电场能与电磁能之间转化时，不断地被电阻元件消耗掉，所以形成的振荡为减幅振荡，即幅度随着时间衰减到零；另一种可能是电阻较大，电容存储的能量在第一次转移时就有大部分被电阻消耗掉，电路中的能量已经不可能在电场能与电磁能之间往返转移，电压、电流将直接衰减到零。 7.1.2 二阶电路的微分方程 二阶电路如下，其中电容电压的初始值为0)0()0(U u u C C ==-+，电感电流的初始值为 0)0()0(==-+L L i i 。 图8-2 R 、L 、C 串联的二阶电路 根据该电路列写电路方程为0=++-L R C u u u 其电路电流为： dt du C i C -=
类图
UML实践----用例图、顺序图、状态图、类图、包图、协作图 2009-01-20 作者：Randy Miller 来源：网络 面向对象的问题的处理的关键是建模问题。建模可以把在复杂世界的许多重要的细节给抽象出。许多建模工具封装了UML（也就是Unified Modeling Language?），这篇课程的目的是展示出UML的精彩之处。 UML中有九种建模的图标，即： ?用例图 ?类图 ?对象图 ?顺序图 ?协作图 ?状态图 ?活动图 ?组件图 ?配置图 本课程中的某些部分包含了这些图的细节信息的页面链接。而且每个部分都有一个小问题，测试一下你对这个部分的理解。 为什么UML很重要？ 为了回答这个问题，我们看看建筑行业。设计师设计出房子。施工人员使用这个设计来建造房子。建筑越复杂，设计师和施工人员之间的交流就越重要。蓝图
就成为了这个行业中的设计师和施工人员的必修课。 写软件就好像建造建筑物一样。系统越复杂，参与编写与配置软件的人员之间的交流也就越重要。在过去十年里UML就成为分析师，设计师和程序员之间的“建筑蓝图”。现在它已经成为了软件行业的一部分了。UML提供了分析师，设计师和程序员之间在软件设计时的通用语言。 UML被应用到面向对象的问题的解决上。想要学习UML必须熟悉面向对象解决问题的根本原则――都是从模型的建造开始的。一个模型model就是根本问题的抽象。域domain就是问题所处的真实世界。 模型是由对象objects组成的，它们之间通过相互发送消息messages来相互作用的。记住把一个对象想象成“活着的”。对象有他们知道的事（属性attributes）和他们可以做的事（行为或操作behaviors or operations）。对象的属性的值决定了它的状态state。 类Classes是对象的“蓝图”。一个类在一个单独的实体中封装了属性（数据）和行为（方法或函数）。对象是类的实例instances。 用例图 用例图Use case diagrams描述了作为一个外部的观察者的视角对系统的印象。强调这个系统是什么而不是这个系统怎么工作。 用例图与情节紧紧相关的。情节scenario是指当某个人与系统进行互动时发生的情况。下面是一个医院门诊部的情节。 “一个病人打电话给门诊部预约一年一次的身体检查。接待员找出在预约记录本上找出最近的没有预约过的时间，并记上那个时间的预约记录。” 用例Use case是为了完成一个工作或者达到一个目的的一系列情节的总和。角色actor是发动与这个工作有关的事件的人或者事情。角色简单的扮演着人或者对象的作用。下面的图是一个门诊部Make Appointment用例。角色是病人。角色与用例的联系是通讯联系communication association（或简称通讯communication）
一阶电路和二阶电路的动态响应
实验四 一阶电路和二阶电路的动态响应 一、 实验目的 （1） 理解零输入响应、零状态响应和完全响应 （2） 理解欠阻尼、临界和过阻尼的意义和条件 二、 实验原理 用二阶微分方程描述的动态电路称为二阶电路。图所示的线性RLC 串联电路是一个典型的二阶电路。可以用下述二阶线性常系数微分方程来描述： s 2 U 2=++c c c u dt du RC dt u d LC 1． 零输入响应 动态电路在没有外施激励时，由动态元件的初始储能引起的响应，称为零输入响应。 电路如图6.2所示，设电容已经充电，其电压为U 0，电感的初始 电流为0。 (1) C L R 2 >，响应是非振荡性的，称为过阻尼情况。 电路响应为： 图6.2 RLC 串联零输入响应电路 图6.3 二阶电路的过阻尼过程 u L t m U 0
) () ()()()(2 1 2 1 120 121 20 t P t P t P t P C e e P P L U t i e P e P P P U t u ---= --= 响应曲线如图6.3所示。可以看出：u C (t)由两个单调下降的指数函数组成，为非振荡的过渡过程。整个放电过程中电流为正值， 且 当2 11 2ln P P P P t m -=时，电流有极大值。 （2）C L R 2 =，响应临界振荡，称为临界阻尼情况。 电路响应为 t t c te L U t i e t U t u ααα--=+=00)()1()( t ≥0 响应曲线如图6.4所示。 图6.4 二阶电路的临界阻尼过程 (3) C L R 2<，响应是振荡性的，称为欠阻尼情况。 电路响应为 t e L U t i t e U t u d t d d t d C ωωβωωωααsin )(),sin()(000 --= +==t ≥0 其中衰减振荡角频率 2 220d 2L R LC 1?? ? ??-= -=αωω ， α ωβd arctan = 响应曲线如图6.5所示。
第七章 二阶电路
§7.1 二阶电路的零输入响应 二阶电路是指用二阶微分方程来描述的电路。下面主要通过分析RLC 串联电路来说明求二阶电路响应的方法。 1.方程和初始条件 图 7.1 图7.1所示的RLC串联电路在t=0时刻闭合开关，设电容原本充有电压U0，此电路的放电过程是二阶电路的零输入响应问题。电路的KVL方程及元件的VCR 为： 若以电容电压为变量，从以上方程中消去其他变量得二阶齐次微分方程： 初始条件为：u C (0+)= U 0 ，i (0+)=0 ，或 若以电感电流为变量，则方程为： 初始条件为：i (0+)=0 ， 根据 得： 2．二阶微分方程的解及其物理意义 以电容电压为变量，电路方程为： 从中得特征方程：
特征根为： 上式表明特征根仅与电路参数和结构有关，而与激励和初始储能无关。当R、L、C的参数不同，特征根为不同的形式。下面分三种情况讨论。 （1）当时，特征根为两个不相等的负实根，电路处于过阻尼状态。 此时方程的解为： 由初始条件：， 得： 即： 因此电容电压为： 电流为： 电感电压为： 图7.2给出了电容电压、电流和电感电压随时间变化的波形，从中可以看出，电容电压和电流始终不改变方向，且最终衰减至零，说明电容始终在释放能量，称过阻尼放电。能量的转换过程如图7.3所示。 图7.2表明t=t m时，i C取得最大值，t=2tm时，u L为极小值。通过对电流求导，可计算时间t m。即： 图 7.2
→ → 图 7.3 （2）当时，特征根为两个共轭复根，电路处于振荡放电状态。令： 则特征根为： 电容电压的u C的通解形式为： 经常把上式写成三角函数形式： 故把ω称为振荡频率。 通解中待定常数A ， b 根据初始条件确定，即： 联立求解以上方程得： 由于ω、ω０、δ、b 满足图7.4所示的三角关系: 所以 则
UML面向对象设计与分析课后习题答案
分析了UML的几个重要图看看是否可以？ 第2章用例图 1．一台自动售货机能提供6种不同的饮料，售货机上有6个不同的按钮，分别对应这6种不同的饮料，顾客通过这些按钮选择不同的饮料。售货机有一个硬币槽和找零槽，分别用来收钱和找钱。现在为这个系统设计一个用例图？ 顾客 2．现有一个产品销售系统，其总体需求如下： 系统允许管理员生成存货清单报告。 管理员可以更新存货清单。 销售员记录正常的销售情况。 交易可以使用信用卡或支标，系统需要对其进行验证。 每次交易后都需要更新存货清单。 分析其总体需求，并绘制出其用例图？ 3．绘制用例图，为如下的每个事件显示酒店管理系统中的用例，并描述各用例的基本操作流程。 客人预订房间。 客人登记。 客人的承担服务费用。 生成最终账单 客人结账 客人支付账单
第3章类图、对象图和包图 1．创建一个类图。下面给出创建类图所需的信息。 ●学生（student）可以是在校生（undergraduate）或者毕业生（graduate）。 ●在校生可以是助教（tutor）。 ●一名助教指导一名学生。 ●教师和教授属于不同级别的教员。 ●一名教师助理可以协助一名教师和一名教授，一名教师只能有一名教师助理，一名 教授可以有5名教师助理。 ●教师助理是毕业生。 创建类图的步骤如下： （1）将学生可以是在校生或者毕业生建模为3个类：Student、UnderGraduate和Graduate，其中，后两个类是Student类的子类。 （2）为“在校生可以是助教的一种”建立模型，即建立UnderGraduate类的另一个超类Tutor。 （3）通过创建从Tutor到Student的关联（名为tutors），建立一名助教指导一名学生的模型。 （4）将“教师和教授属于不同级别的教员”建模为3个类：Instructor、Teacher和Professor，其中，后两个类是Instructor类的子类。 （5）建立“一名教师助理可以协助一名教师和一名教授，一名教师只能有一名教师助理，一名教授可以有5名教师助理”的模型。创建TeacherAssistant类，并使其与Teacher 类和Professor类都建立关联。 （6）将TeacherAssistant类建模为Graduate类的派生类。
第七章 二阶电路
第七章 二阶电路 当电路中含有两个独立的动态元件时，描述电路的方程为二阶微分方程，电路称为二阶电路。二阶电路过渡期的特性不同于一阶电路。用经典的方法分析二阶电路的步骤为： （1）根据KVL ，KCL 及元件的VCR 写出以C u 或L i 为变量的二阶微分方程； （2）由(0)(0)C C u u -+=，(0)(0)L L i i -+=确定电路的初始状态，即得出 (0), C C o du u dt + +或 (0), L L o di i dt + +的值； （3）求出二阶微分方程的两个特征根1,2p p ，根据的不同取值1,2p p ，确定方程的齐次通解（也是电路的零输入响应），一般分为三种情况： ()112p p ≠为两个不相等的实根（称过阻尼状态） 通解=1212p t p t Ae A e + ()1,22p j δω=-±为共轭复根（称欠阻尼或衰减振荡状态） 通解= sin()t Ae t δωβ-+ ()123p p p ==为相等实根（称临界状态） 通解=12()pt A A t e + ()4由激励源的函数形式确定方程的特解形式； ()5由初始条件，确定12,A A 或,A β等待定常数，得出确定的解。 二阶电路的重点是掌握其在过渡期的三种状态及物理过程。 7-1 电路如图所示，开关未动作前电路已达稳态，t=0时开关S 打。求 000(0),(0), , , C L R C L du di di u i dt dt dt + + + ++。 解：这是一个求二阶电路初始值的问题，求法与一阶电路类似。先求)0(-C u 和)0(-L i 。t<0时，电路处于稳态，把电容断开，电感短路，电路如题解图（a ）所示。由图（a ）得
UML各种图例齐全—用例图、类图、状态图、包图、协作图、顺序图详细说明画法和功能
UML各种图例 面向对象的问题的处理的关键是建模问题.建模可以把在复杂世界的许多重要的细节给抽象出.许多建模工具封装了UML（也就是Unified Modeling Language?），这篇课程的目的是展示出UML的精彩之处. UML中有九种建模的图标，即： ?用例图 ?类图 ?对象图 ?顺序图 ?协作图 ?状态图 ?活动图 ?组件图 ?配置图 本课程中的某些部分包含了这些图的细节信息的页面链接.而且每个部分都有一个小问题，测试一下你对这个部分的理解. 为什么UML很重要? 为了回答这个问题，我们看看建筑行业.设计师设计出房子.施工人员使用这个设计来建造房子.建筑越复杂，设计师和施工人员之间的交流就越重要.蓝图就成为
了这个行业中的设计师和施工人员的必修课. 写软件就好像建造建筑物一样.系统越复杂，参与编写与配置软件的人员之间的交流也就越重要.在过去十年里UML就成为分析师，设计师和程序员之间的“建筑蓝图”.现在它已经成为了软件行业的一部分了.UML提供了分析师，设计师和程序员之间在软件设计时的通用语言. UML被应用到面向对象的问题的解决上.想要学习UML必须熟悉面向对象解决问题的根本原则――都是从模型的建造开始的.一个模型model就是根本问题的抽象.域domain就是问题所处的真实世界. 模型是由对象objects组成的，它们之间通过相互发送消息messages来相互作用的.记住把一个对象想象成“活着的”.对象有他们知道的事（属性attributes）和他们可以做的事（行为或操作behaviors or operations）.对象的属性的值决定了它的状态state. 类Classes是对象的“蓝图”.一个类在一个单独的实体中封装了属性（数据）和行为（方法或函数）.对象是类的实例instances. 用例图 用例图Use case diagrams描述了作为一个外部的观察者的视角对系统的印象.强调这个系统是什么而不是这个系统怎么工作. 用例图与情节紧紧相关的.情节scenario是指当某个人与系统进行互动时发生的情况.下面是一个医院门诊部的情节. “一个病人打电话给门诊部预约一年一次的身体检查.接待员找出在预约记录本上找出最近的没有预约过的时间，并记上那个时间的预约记录.” 用例Use case是为了完成一个工作或者达到一个目的的一系列情节的总和.角色actor是发动与这个工作有关的事件的人或者事情.角色简单的扮演着人或者对象的作用.下面的图是一个门诊部Make Appointment用例.角色是病人.角色与用例的联系是通讯联系communication association（或简称通讯communication）
第7章-二阶电路-习题库
二阶电路习题 12-1 题12-1图示电路原处于稳态，t =0时开关K 闭合， 求u C (0+)、+0|dt du C 、i L (0+)、+0|dt di L 。 C + - 题12-1 解：t <0时 A i L 23 210 )0(=+= - V i u L C 6)0(3)0(==-- 由换路定则有: V u u A i i C C L L 6)0()0(,2)0()0(====-+-+ s V u C i dt du s A i L u dt di C C C L L L /22 )) 0(0()0(|/14 4 410)0(3)0(| 00=-====+-==++++++ 12-2 电路如题12-2图所示，建立关于电感电流i L 的微分方程。 题12-2图 C + - 解：回路1: S C L L u u dt di L i R =++1……(1) 对A 点:L C C i R u dt du C =+2 ……………(2) 由(1)式得：dt di L i R u u L L L C --=1 代入(2)整理得：
S S L L L u R dt du C i R R dt di R L C R dt i d LC 22121221 )1()(+=++++ 12-3 电路如题12-3图所示，建立关于u C 2的微分方程。 题12-3图 C2 解：列A 点KCL 的方程 )1( (211) ????=-+S C C C i u u dt du 列B 点KCL 的方程 )2(022 1222 ??=-++C C C C u u u dt du 由(2)得：22 132 C C C u dt du u += 代入(1)得：S C C C C C i u u dt du dt du dt u d =-+++22222 223232 整理得：S C C C i u dt du dt u d =++22 2 22252 12-4 题12-4图示电路中，已知u C (0-)=200V ，t =0时开关闭合，求0≥t 时的u C 。 u 题12-4图 u L - + 解：1、列写以u C 为变量的二阶微分方程 电容的电流 dt du i C C 6 105-?= (1) 电阻的电压 dt du i u C C R 6 105200200-??==
第七章二阶电路
142 第七章 二阶电路 本章内容：二阶电路的响应分析 本章重点：根据电路的结构、参数及特征根；电路过渡过程的形成、激励及初 始条件分析二阶电路 本章难点：二阶电路的分析 §7-1 二阶电路的零输入响应 用二阶方程描述的动态电路称为二阶电路，RLC 串联电路和GLC 并联电路是最基本的二阶电路，我们讨论RLC 串联电路的零输入响应。 电路如图，t=0时，开关s 闭合此电路为零输入响应。 一、方程及特征根 将 代入上式有： 上式为线性常系数二阶齐次微分方程，其特征方程为： 解得特征根为： LC 1 = 21p p 012??p p
143 响应为： 式中：A 1，A 2为积分常数由电路的初始条件确定，电路的初始条件有三种情况，分别为： ①u c (0+)≠0 i L (0+)≠0 ②u c (0+)≠0 i L (0+)=0 ③u c (0+)=0 i L (0+)≠0 我们讨论第二种情况，设u c (0+)=u c (0-)=U 0 ，i L (0+)= i L (0-)=0,其它两种情况分析方法相同 式中：特征根p 1、p 2有不等实数根、相等实数根、一对共轭复数根三种情况， 下面就这三种情况进行分析 二、C L R 2 >（p 1、p 2有不等实根）时电路的响应 ：是一个非振荡过程 则有： 联立求解得： 1．电容上的电压和电流及电感上的电压响应表达式为： LC 1= 21p p
144 2．响应曲线 由于012??p p 则t p e 2比t p e 2下降的慢，则u c 、i 方向不变，且大于0，表明电 容在整个过程中一直是释放储存能量，故称非震荡放电，也称过阻尼放电。 （1）极值： 电流极值：电流由0增大到最大再到0的过程，其最大值t m 由di/dt=0确定。可求出 此时电感电压过0，电流取得最大值 电感电压极值：t=2t m （2）能量关系 0
第七章 复习题
第七章 一阶电路和二阶电路的时域分析 一、是非题 1.若电容电压(0)0c u -=,则接通时电容相当于短路。在t=∞时,若电路中电容电流0c i =, 则电容相当于开路。 2. 换路定则仅用来确定电容的起始电压(0)c u +及电感的起始电流(0)L i +,其他电量的起始值应根据(0)c u +或(0)L i +按欧姆定律及基尔霍夫定律确定。 3. 在一阶电路中，时间常数越大，则过渡过程越长。 4.一阶电路的时间常数只有一个，即一阶电路中的各电压、电流的时间常数是相同的。 5. 零输入的ＲＣ电路中,只要时间常数不变,电容电压从100V 放电到50V 所需时间与从 150V 放电到100V 所需时间相等。 6.在Ｒ、Ｃ串联电路中，由于时间常数与电阻成正比，所以在电源电压及电容量固定时，电 阻越大则充电时间越长，因而在充电过程中电阻上消耗的电能也越多。 7.单位冲激函数是单位阶跃函数的一阶导数，因此线性电路的单位冲激响应是单位阶跃响应 的一阶导数。 （ ） 8.一阶RL 电路在冲激函数() t δ作用下，换路定律 ()() 00L L i i +-=不再适用。（ ） 二、选择题 1.RC 电路在零输入条件下，时间常数的意义是 A 、响应的初始值衰减到0.632倍时所需时间 B 、响应的初始值衰减到0.368倍时所需时间 C 、过渡过程所需的时间 D 、过渡过程结束所需的时间c 2.一阶电路的零状态响应，是指： (A) 电容电压()00V C u +=或电感电压 ()00V L u += (B) 电容电压 ()00V C u +=或电感电 流 ()00V L i += (C) 电容电流()00V C i +=或电感电压()00V L u += (D) 电容电流()00V C i +=或电感电流 ()00V L i += 3.R 、C 放电电路经过1.2秒后，电容器电压降为原来的36.8%，则其时间常数τ为 (A) 0.4s (B) 1.2s (C) 0.8s (D) 0.6s 4. R 、C 串联电路，已知全响应 ()() 1083V 0t C u t e t -=-≥，其零状态响应为：( )