The blocking job shop with rail-bound transportation

The blocking job shop with rail-bound transportation (BJS-RT) considered here is a version of the job shop scheduling problem characterized by the absence of buffers and the use of a rail-bound transportation system. The jobs are processed on machines and are transported from one machine to the next by mobile devices (called robots) that move on a single rail. The robots cannot pass each other, must maintain a minimum distance from each other, but can also “move out of the way”. The objective of the BJS-RT is to determine for each machining operation its starting time and for each transport operation its assigned robot and starting time, as well as the trajectory of each robot, in order to minimize the makespan. Building on previous work of the authors on the flexible blocking job shop and an analysis of the feasible trajectory problem, a formulation of the BJS-RT in a disjunctive graph is derived. Based on the framework of job insertion in this graph, a local search heuristic generating consistently feasible neighbor solutions is proposed. Computational results are presented, supporting the value of the approach.     

一种求解柔性工作车间调度问题的混合遗传算法

针对柔性工作车间调度问题(Flexible job-shop scheduling problem, FJSP),提出了一种基于混合遗传算法的求解方案,在初始种群中引入基于启发式规则生成的优良个体,并使用有效的交叉、变异算子避免不可行个体的产生,同时利用混沌序列的随机性和遍历性特点,在遗传进化的过程中增加基于混沌序列的邻域搜索功能,以提高遗传算法的执行效率.通过仿真实验验证了该算法的可行性和有效性.     

The no-wait job shop with regular objective: a method based on optimal job insertion

The no-wait job shop problem (NWJS-R) considered here is a version of the job shop scheduling problem where, for any two operations of a job, a fixed time lag between their starting times is prescribed. Also, sequence-dependent set-up times between consecutive operations on a machine can be present. The problem consists in finding a schedule that minimizes a general regular objective function. We study the so-called optimal job insertion problem in the NWJS-R and prove that this problem is solvable in polynomial time by a very efficient algorithm, generalizing a result we obtained in the case of a makespan objective. We then propose a large neighborhood local search method for the NWJS-R based on the optimal job insertion algorithm and present extensive numerical results that compare favorably with current benchmarks when available.     

The permutation flow shop problem with blocking. A tabu search approach

This paper develops a fast tabu search algorithm to minimize makespan in a flow shop problem with blocking. Some properties of the problem associated with the blocks of jobs have been presented and discussed. These properties allow us to propose a specific neighbourhood of algorithms. Also, the multimoves are used that consist in performing several moves simultaneously in a single iteration and guide the search process to more promising areas of the solutions space, where good solutions can be found. It allow us to accelerate the convergence of the algorithm. Besides, a dynamic tabu list is proposed that assists additionally to avoid being trapped at a local optimum. The proposed algorithms are empirically evaluated and found to be relatively more effective in finding better solutions than attained by the leading approaches in a much shorter time. The presented ideas can be applied in many local search procedures.     

Evaluation of scheduling strategies for a dynamic job shop in a tool-shared,flexible manufacturing environment

A two-phase approach is used to examine the impact of job scheduling rules and tool selection policies for a dynamic job shop system in a tool-shared, flexible manufacturing environment. The first phase develops a generalized simulation model and analyses 'simple' job scheduling rules and tool selection policies under various operating scenarios. The results from this investigation are then used to develop and analyse various bi-criteria rules in the second phase of this study. The results show that the scheduling rules have the most significant impact on system performance, particularly at high shop load levels. Tool selection policies affect some of the performance measures, most notably, proportion of tardy jobs, to a lesser degree. Higher machine utilizations can be obtained at higher tool duplication levels but at the expense of increased tooling costs and lower tool utilization. The results also show that using different processing time distributions may have a significant impact on shop performance.     

A mathematical model for job shop scheduling with multiple process plan consideration per job

In this paper, a mixed integer programming model is formulated for scheduling a set of jobs through a shop when each job is supplied or provided with multiple process plans or process routings. Simultaneous selection of a process plan for each job and the sequencing of the jobs through the machines in the shop based on the set of selected process plans is addressed. The procedure developed seeks to integrate the selection of machines for each job and the sequencing of jobs on each machine based on the objective of minimizing production makespan. the application of the procedure is demonstrated with an example problem. The following conclusions were drawn as a result of the research: (1) the procedure developed produces optimal or near optimal solution; (2) the benefit from the developed approach is that it allows a shop to adaptively select process plans for jobs to optimize on production makespan. By combining solution quality with scheduling flexibility and efficiency, the productivity of a shop can be greatly enhanced.     

Search based job scheduling and sequencing with setup times

The problem of sequencing jobs on a machine in a job shop has been approached by a number of researchers and practitioners. One of the most popular methods is to apply a priority rule to the queue at each machine. The authors have previously published details of an approach which sets the priority of a job as a linear combination of the operation times and due date for that job. The coefficients in the linear combination are set by a simulation and search procedure so as to give good performance based on the performance measure specified. This paper extends this approach to include setup time factors. This extended approach is then applied to data from an actual manufacturing system. The extended approach is shown to improve the performance of the manufacturing system in relation to existing techniques.     

A genetic algorithm for scheduling on a single machine with set-up times and due dates

This paper presents a genetic algorithm for a single machine-scheduling problem with the objective of minimizing total tardiness. Each job has its own due date and the set-up times are sequence dependent. The parameters of the genetic algorithm are determined by a statistical method. For small problems, the solutions given by the proposed method are compared with solutions provided by a commercial package, and for larger problems, with those obtained by a heuristic proposed in the literature.     

Minimizing makespan in an ordered flow shop with?machine-dependent processing times

We consider a generalization of the proportionate flow shop problem with the makespan objective. Each job has a processing requirement and each machine has a characteristic value. In our case, we assume that the time a job occupies a machine is equal to the processing requirement of the job plus a setup time that is equal to the characteristic value of that machine. In this paper, we consider permutation schedules and show that the problem is solvable in polynomial time when the number of machines is fixed.     

An estimation of distribution algorithm for lot-streaming flow shop problems with setup times

Lot-streaming flow shops have important applications in different industries including textile, plastic, chemical, semiconductor and many others. This paper considers an n-job m-machine lot-streaming flow shop scheduling problem with sequence-dependent setup times under both the idling and no-idling production cases. The objective is to minimize the maximum completion time or makespan. To solve this important practical problem, a novel estimation of distribution algorithm (EDA) is proposed with a job permutation based representation. In the proposed EDA, an efficient initialization scheme based on the NEH heuristic is presented to construct an initial population with a certain level of quality and diversity. An estimation of a probabilistic model is constructed to direct the algorithm search towards good solutions by taking into account both job permutation and similar blocks of jobs. A simple but effective local search is added to enhance the intensification capability. A diversity controlling mechanism is applied to maintain the diversity of the population. In addition, a speed-up method is presented to reduce the computational effort needed for the local search technique and the NEH-based heuristics. A comparative evaluation is carried out with the best performing algorithms from the literature. The results show that the proposed EDA is very effective in comparison after comprehensive computational and statistical analyses.     

A comparative analysis of due date based job sequencing rules in a flow shop with multiple processors

The literature on job scheduling recognizes the importance of due date performance criteria such as mean tardiness and maximum tardiness. A number of studies test a large number of sequencing rules for these criteria in job shop and flow shop settings. The object of this present research is to examine the performance of some well-known priority rules in a flow shop with multiple processors. This study investigates the performance of ten priority rules in terms of mean and maximum tardiness. It examines the effects of problem characteristics, such as number of jobs, number of machines stages and number of parallel processors at each stage, and the performance of priority rules using regression analysis. The findings of the study suggest that the primary determinants of tardiness-based criteria are problem characteristics. In addition, both the regression analysis and the analysis of variance provide strong evidence of the strategy-effect. Finally, a detailed performance review of examined priority rules for various problem characteristics is presented.     

Inspection of an unreliable flexible manufacturing system: with repairable parts and non-negligible inspection times

The purpose of this paper is to address the problem of quality control and repair in an FMS which is described by an open queuing network. We consider two cases: first, all detected defective parts are directed to a special repair facility; second, a defective part is repaired within the machine group where it is detected. Using numerical analyses, we provide some managerial insights regarding the role, position, and distribution of the inspection effort in an FMS, and draw some inferences regarding the design of such FMS when both quality and quantity issues in the FMS are considered.     

The permutation flow shop problem with just in time production considerations

This research presents a variation to the permutation flow shop problem where Just In Time (JIT) production requirements are taken into account. The model developed in this research employs dual objectives. In addition to the traditional objective of minimizing the production makespan, minimization of Miltenburg's material usage rate is also incorporated. In this model, multiple units of any product are permitted in the production sequence. However, the minimization of material usage rates attempts to prevent batch scheduling of products and allows unit flow of products as required in demand flow manufacturing. A solution method is proposed for determining an optimal production sequence via an efficient frontier approach and Simulated Annealing (SA). Test problems and specific performance criteria are used to assess the solutions generated by the proposed method. Experimental results presented in this paper show that the use of the efficient frontier and SA provide solutions that approach the optimal solution for the performance measures used in this research.     

The meaning of work and job

This article proposes that the concepts of work and job derive meaning from different dimensions. Work is viewed as having meaning that relates to a social framework and goes beyond organizational boundaries. Here two dimensions of work meaning are termed acceptability and instrumentality. Job meaning on the other hand, is viewed to be the result of an interplay between situational characteristics and organizational dimensions, and the value and relevance of those to an individual. These dimensions are here referred to as situational and personal relevance job meaning. It is suggested that making a distinction between work and job meaning will facilitate comparisons between groups that are of different employment status.     

The technician routing problem with experience-based service times

While home services are a fast growing industry, little attention has been given to the management of its workforce. In particular, the productivity of home-service technicians depends not only on efficiently routing from customer-to-customer, but also the management of their skillsets. This paper introduces a model of technician routing that explicitly models individualized, experience-based learning. The results demonstrate that explicit modeling and the resulting ability to capture changes in productivity over time due to learning lead to significantly better and different solutions than those found when learning and workforce heterogeneity is ignored. We show that these differences result from the levels of specialization that occur in the workforce.     

The role of gender and job level in coping with occupational stress

The aim of the study was to investigate the relationship between coping and health problems in the context of gender and level in the organization. Questionnaire data were collected from 279 women and men (100 managers and 179 non-managers) at a sales department in a Swedish telecom company in which men and women worked at similar tasks. It was hypothesized that, if gender and level in the organization were controlled for, the use of problem-focused strategies would be associated with fewer health problems and the use of emotion-focused strategies with greater health problems. It was also predicted that men and women at a similar organizational level would not differ in their use of problem-focused coping strategies. The results showed, contrary to the hypothesis, that when level and gender were controlled for, no relation between problem-focused strategies and health was obtained. Instead the emotion-focused strategy of Seeking emotional support was associated with fewer health problems, whereas Focus on emotions and Alcohol/drug disengagement were associated with more symptoms. Coping was at least partly related to level. At a managerial level the men and the women used basically the same strategies whereas at a non-managerial level traditionally-conceived coping patterns were evident.     

The role of gender and job level in coping with occupational stress

The aim of the study was to investigate the relationship between coping and health problems in the context of gender and level in the organization. Questionnaire data were collected from 279 women and men (100 managers and 179 non-managers) at a sales department in a Swedish telecom company in which men and women worked at similar tasks. It was hypothesized that, if gender and level in the organization were controlled for, the use of problem-focused strategies would be associated with fewer health problems and the use of emotion-focused strategies with greater health problems. It was also predicted that men and women at a similar organizational level would not differ in their use of problem-focused coping strategies. The results showed, contrary to the hypothesis, that when level and gender were controlled for, no relation between problem-focused strategies and health was obtained. Instead the emotion-focused strategy of Seeking emotional support was associated with fewer health problems, whereas Focus on emotions and Alcohol/drug disengagement were associated with more symptoms. Coping was at least partly related to level. At a managerial level the men and the women used basically the same strategies whereas at a non-managerial level traditionally-conceived coping patterns were evident.     

The relationship between newcomer expectations of job stressors and adjustment to the new job

This study examined the relationship between unrealistic expectations of organizational newcomers regarding job stressors and subsequent adjustment to the new job. Using a sample of 91 new employees, measures of expected stressors (gathered prior to the first day of work) were compared with stressors reported after six months on the job. The study examined the relationship between the accuracy of expected stressors (demands) and three indicators of job adjustment: job satisfaction; job involvement; and distress symptoms. The results provided partial support for the hypothesis that newcomers who underestimate job stressors have more difficulty adjusting on the new job than do newcomers who overestimate job stressors.     

The externalized nature of teachers' occupational stress and its association with job satisfaction

The dimension of 'blame' was explored as part of a conceptual framework for teachers' externalization of occupational stress. It was proposed that teachers allocate principal responsibility for their occupational stress to sources external to the individual. The authors suggest that teachers externalize their dissatisfaction to these (external to self) domains. This hypothesis was explored with a sample (n=111) of teachers in the service of the New South Wales Department of Education, Australia. A survey, composed of multiple items, dealt separately with the phenomena of perceived occupational satisfaction-dissatisfaction and stress. Four stress factors were isolated. These were named: personal, student, school and external (to school). These factors were consistent with the authors' hypothesis that teachers generally externalize blame for their stress. Further examination of the association between the satisfaction factor scores and the stress factor scores revealed significant canonical correlations. The main contributors to the correlation between stress and satisfaction factors were the personal domain (stress) and income (satisfaction) and the school domain (stress) and school culture (satisfaction).     

Online scheduling on a single machine with linear deteriorating processing times and delivery times

Journal of Combinatorial Optimization - This paper considers a class of problems with linear deteriorating jobs. Jobs are released over time and become known to the online scheduler until their...