An empirical analysis of job shop dispatch rule selection

Job shop scheduling usually includes the process of selecting dispatch rules for loading shops with work. Traditionally, dispatch rules have been formed on the basis of processing time, operating time, or queueing order. A job shop scheduling model was developed to include external factors (such as due dates), internal factors (e.g., capacity), as well as influence factors (e.g., job status). Based on the model developed in this report a survey of industrial engineers, shop foremen, and production control supervisors was undertaken to determine what dispatch rules experienced job shop schedulers would select and if the selection process could be influenced by schedule conditions (status) or other organizational factors. Results suggest that schedulers may be influenced by other factors. This article suggests a model for further research with respect to job shop scheduling.     

An investigation of labor assignment rules in a dual-constrained job shop

One of the management decisions required to operate a dual-constrained job shop is the labor assignment rule. This study examines the effects of various labor assignment rules on the shop's performance. Eleven different labor assignment rules are simulated. A longest-queue rule and the traditional counterparts of the first-in-system, first-served, shortest operation time, job due date, critical ratio and shortest processing time dispatching rules are used to determine to which work center available workers should be transferred. Also tested are five new labor assignment rules that use an average of the priority values of all jobs in queue at a particular work center to determine whether that work center should receive the available worker.A SIMSCRIPT simulation program that models nine work centers provided the mechanism by which these rules were tested. Five dispatching rules, the counterparts of the five “traditional counterpart” labor assignment rules mentioned earlier, provided different shop environments. Also, the level of staffing of the work centers was altered to provide additional ship environments. Staffing levels of 50% and 67% were employed.The results show that none of the eleven labor assignment rules had a significant impact on shop performance. This is an important result because it implies that a manager can make the labor assignment decision based on other criteria such as ease or cost of application of the rules. These results were relatively insensitive to the shop environment, as represented by the dispatching rule and the staffing level.     

Load-limited order release in job shop scheduling systems

This report examines the practice of using work load limits to control the release of orders to a job shop. Load limits function in the following general way. Whenever the inventory of work at a work center exceeds some critical value (its “load limit”), further release of orders which are routed to that work center are blocked from entering the shop. After the inventory is “worked off,” release of work to the shop gateways is again permitted. Load-limited order release is intuitively appealing because it appears to be a method for reducing system inventory and flow times. The practice of load limiting order release is becoming popularized by some of the recent production planning software products now on the market. A notable example is OPT. In this report, analytical results for an M/M/1 queueing model, along with existing simulation studies of multi-machine job shops are interpreted to form a theory about the effects of using load limits.The major finding here is the proposition that system flow time, inventory, and order tardiness all deteriorate to the extent that load limits introduce idle time into the schedule. Based on the arguments presented here, a very cautious approach toward the use of input control schemes for anywhere but gateway work centers would be advised. The conclusions drawn here are to a great extent arrived at by interpreting the research results of others, so there is a clear need for further research which tests these assertions in a more direct and controlled way.     

丰水期节能调度优化研究

文章根据国家节能调度要求,系统分析广西电网丰水期运行特点,初步建立购电成本最低和燃料消耗最少的双目标节能调度优化模型函数,并结合电网运行要求,提出7点改善广西电网节能调度工作的建议,对于充分利用水能资源,做好节能减排工作,提高企业效益具有重要的意义。     

Use of the net present value criterion in a random job shop where early shipments are forbidden

Both practitioners and researchers in the field of Operations Management have suggested that shop scheduling should be an integral component in both the strategic and tactical plans for an organization's assets. This paper examines the use of an accepted measure of return on assets, net present value (NPV), in a simulated shop scheduling environment where early shipment of jobs before their due dates is forbidden. In addition, early shipment of raw materials to the shop is also forbidden. This shop environment is consistent with the prevalent practice in industry of accepting orders only on a just-in-time basis to reduce purchased parts inventories. The NPV measure provides a means of balancing a variety of performance criteria that have been treated as separate objectives previously, including work-in-process inventory, finished goods inventory, mean flow time and mean tardiness, while also providing a means of measuring monetarily the value of various shop scheduling approaches.The NPV performance of priority scheduling rules and order release policies is measured in this research through the simulation of a random job shop under a variety of environmental conditions. It is found in a comparison of priority rules that use time-based information with those that use job value information that the Critical Ratio rule provides higher average performance than the three other rules used in the study. However, in some situations that are consistent with JIT practice, value-based priority rules also perform well. The use of a mechanism for delaying the release of jobs to each work center in the shop provided higher average NPV when shop utilization was set at a low level of 80%, while immediate release of work upon its arrival to the shop provided superior performance at a higher shop utilization level of 94%. While JIT materials delivery and costing yields higher NPV, it did not alter the relative ranking of priority rule/release policy combinations. In addition, it was found that environmental factors, including average job length, average number of tasks per job and level of tardiness penalty, resulted in greater variations in NPV performance than the institution of a JIT raw materials delivery policy.     

论如何做好新时期企业思想政治工作

文章分析研究现阶段企业思想政治工作面临的新形势、新问题,探讨思想政治工作的新规律、新方法,对企业做好思想政治工作有着十分重要的现实意义。     

浅谈签派安全管理中人因工程学的应用

飞行签派工作是一项高度复杂的系统工程,其工作环境非常复杂,对人员的素质要求高。如何提高飞行签派的安全管控和技术水平是航空公司所面临的一个重大问题。本文将依据签派理论和人因工程学理论提出民航飞行签派管理的控制模型,在飞行安全的管理中尽量减少人为差错,提高飞行安全水平。     

The effects of vehicle ownership on employment

Vehicle ownership may promote work if employment opportunities and job searches are enhanced by reliable transportation. For example, vehicles may serve to reduce potential physical isolation from employment opportunities. I examine the effects of vehicle ownership and vehicle quality on employment for single mothers with no more than a high school education using National Longitudinal Survey of Youth data. I control for potential bias by jointly estimating employment and vehicle ownership in a maximum likelihood framework using state welfare eligibility asset rules as instruments. Results show that vehicle ownership increases employment. Positive effects of vehicles do not differ for urban and rural residents, but they do change with economic conditions. Further, welfare recipients are significantly more likely to exit the program and become employed if they own a vehicle.     

Use of work–nonwork supports and employee well-being: the mediating roles of job demands,job control,supportive management and work–nonwork conflict

Abstract

This paper examines the impact of the use of work–nonwork supports on well-being. It first develops hypotheses regarding how a reduction in job demands, and an increase in both job control and supportive management may explain this relationship. We then test these hypotheses using data from Britain’s Workplace Employee Relations Survey of 2011. The research reveals that the use of work–nonwork supports has a positive association with job control and supportive supervision. These in turn mediate a relationship between the use of supports and three dimensions of employee well-being, job satisfaction, anxiety-contentment and depression-enthusiasm, some of the effect being through their reducing work–to–nonwork conflict. Use of work–nonwork supports is, however, positively associated with job demands, but this effect of use on job demands does not affect well-being. Since job autonomy and supportive supervision are major mediators, and have a direct influence on work–nonwork conflict and well-being, policy should focus on integrating job quality and work–life balance issues.     

企业劳务派遣用工方式的利弊及风险控制

随着我国人事管理管理模式的转变,劳务派遣用工方式成为解决企业用人困难、提高人力资源配置效率的重要举措。虽然企业采用劳务派遣用工方式具有明显的优势,但是其中也存在一定风险。因此,论文立足多年工作实践,阐述了企业劳务派遣用工方式的利弊,进而提出控制企业劳务派遣用工风险的具体对策。     

基于遗传算法的港口堆场入场模型设计

码头堆场的集装箱调度成本过高一直以来都是困扰各港口企业的难题之一。调度成本中又以翻箱成本占最大比重。传统控制翻箱率的方法主要是靠码头调度中心的调度员通过个人经验等方式进行调度控制,不仅对调度员要求很高,而且由于人为判断容易失误,会造成大量翻箱。文中拟通过将堆场流程模型化设计,并通过遗传算法行之有效地模拟出堆场入场的最优方案。     

基于蚁群算法的出租车零空载问题探讨

车辆路径规划是一种比较典型的组合优化问题,新型的仿生算法--蚁群算法,由于具有正反馈性、鲁棒性、并行计算、协同性等特点,非常适合于解决车辆路径规划问题.本文针对出租车的空载问题,通过利用地理信息系统(GIS),通过设立手机短信平台和出租车控制中心的合理调度,结合蚁群算法寻找距离乘客最近的空载出租车,给出了空载出租车到乘客的最优的路径,并通过Matlab实现了其仿真,提出了对出租车控制问题的设想,进而有效地避免出租车的空载问题,实现人力和物力的节约.     

Are contingent jobs dead ends or stepping stones to regular jobs? Evidence from a structural estimation

The proportion of part-time, dispatch, and temporary workers has increased in many developed economies in recent years. These workers receive lower average wages and benefits, and are subject to lower employment stability. This paper analyzes the effects of initially taking such jobs on the employment careers of young workers. We build an on-and-off-the-job search model, using Japanese data to perform a structural estimation of the model parameters and simulate career paths, in order to study the effects of the initial choice of employment on the probability of having a regular job in the future and on the welfare of the worker. We find that although contingent jobs are neither stepping stones towards regular employment nor dead ends, starting a career in a contingent job has a lasting effect on the welfare of the individual in Japan.     

SOME CORRELATES OF DISCRETION FOR CHARTERED SURVEYORS

The discretion of professionals in small organizational practices was examined. This research identified three types of discretion: (1) discretion over clients; (2) discretion over the choice and sequence of tasks; (3) discretion over task rules and procedures. the first two forms of discretion are associated with high performance and job satisfaction. Discretion over rules and procedures in tasks (contrary to the job design literature) is not associated with satisfaction or performance, and is positively associated with role conflict and role ambiguity. Organization size reduces discretion over clients, but not over tasks. Reduced discretion over clients in turn is associated with low ability to attract work.     

Sequencing rules and due date setting procedures in flow line cells with family setups

The purpose of this study is to investigate due date setting procedures and dispatching decisions in a flow line cell with family setups. In this environment, setups are not required when switching from a job in a given family to a job in the same family. However, switching from a job in one family to a job in another family requires a setup. Family setups in this shop are sequence independent. The dispatching decisions in this shop are threefold: (1) when should the decision to switch from one part family to another be made; (2) once the decision to switch families is made, how should the next part family be chosen (next family decision); and (3) how should the jobs within a family be prioritized (next job decision)? If the decision to switch classes can only be made after the current family is exhausted, the rule is called a class exhaustion rule. Otherwise the rule is a truncated rule. The results indicate that the due date setting procedure has a major impact on how dispatching should be performed in the shop. The family exhaustion procedure using the APT next family rule and the SPT next job rule is the best performer for mean flow time. When setup times are long, the SEQ due date rule using the family exhaustion procedure with the FCFS next family and the EDD next job rules performed well for due date criteria. When setup times are short, the EDD/T, Sawicki truncation rule and the family exhaustion rules performed well for due date criteria.     

The effects of input control in a simple scheduling model

Input control is a generic procedure for smoothing production workload by delaying work during intervals of heavy load. While input control techniques have several practical benefits, they also have an inherent disadvantage. By restricting the set of jobs available for scheduling, an input control procedure removes some of the scheduling options that would otherwise be available. This paper examines the impact of such a procedure in a simple simulation model.The simulation model represents a production shop in a simplified way, as a single machine, but the production control system has three distinct parts. The first part assigns due-dates to customer orders, taking into consideration the size of each job and the workload in the shop. The second part is a job releasing rule that implements input control. The third part is a priority dispatching procedure that is aimed at meeting due-dates. By representing this three-part control system the model provides an opportunity to explore the interdependence between input control and other control procedures.Reinforcing previous research, the simulation experiments confirm that modified due-date priorities perform more effectively than other basic priority rules when performance is measured by average tardiness. Moreover, the experiments indicate that performance under the modified due-date regime is never improved by the use of input control. On the other hand, with dispatching rules that rely on shortest-first or critical ratio priorities, the experiments indicate that input control is sometimes advantageous. The effects of input control on scheduling performance thus appear to be somewhat complicated, and further experiments were designed to explore some of the relationships involved. The principal finding, however, provides a warning that input control can be counterproductive.     

新形势下如何做好企业办公室工作

办公室所处的特殊地位和所属的工作性质,决定了办公室工作职能的核心就是服务,发展趋势就是优化服务,实质就是企业的服务中枢。笔者根据工作经验,对新形势下如何做好企业办公室工作提出建议。     

新形势下如何做好企业办公室工作

办公室所处的特殊地位和所属的工作性质,决定了办公室工作职能的核心就是服务,发展趋势就是优化服务,实质就是企业的服务中枢。笔者根据工作经验,对新形势下如何做好企业办公室工作提出建议。     

从人生导师角色定位谈民办高校辅导员的队伍建设

角色定位准确是高校辅导员做好工作的前提和基础,当前由于种种原因,导致民办高校辅导员角色定位有较大的偏差。培育人生导师式辅导员是民办高校辅导员队伍建设的必由之路,而努力谋求学校对辅导员队伍建设的支持力度,把好准入关,加强培训,成立辅导员工作中心,科学考核是民办高校培育人生导师式辅导员队伍的有效路径。     

The Costs of Exhibiting Organizational Citizenship Behavior

Organizational citizenship behavior (OCB) has been associated with positive organizational outcomes and with higher managerial ratings of employee performance. However, concerns have been raised about the possible personal costs of performing such activities. This paper examines the relationship between OCB and emotional exhaustion and work‐family conflict and explores the moderating role of job performance in shaping those relationships. In a time‐lagged field study of customer‐contact center employees the research found that one particular dimension of OCB—conscientiousness—was associated with higher emotional exhaustion and with work‐family conflict. The study also revealed that conscientious employees who performed their in‐role job responsibilities at a high level experienced greater emotional exhaustion and work‐family conflict than conscientious employees who performed their in‐role job responsibilities at a low level. Our findings suggest that organizational pressures to increase the level at which both discretionary and formal role obligations are performed can carry negative consequences for employees. © 2016 Wiley Periodicals, Inc.