Identical Jobs Research Articles

Twin sisters on identical job pathways

Twin sisters on identical job pathways

Bounded colouring motivated by the limited resource partially concurrent open shop problem

Partially Concurrent Open Shop Scheduling (PCOSS) is a relaxation of the well-known Open Shop Scheduling (OSS), where some of the operations that refer to the same job may be processed concurrently. Here we extend the study of the PCOSS model by considering an additional resource, which is limited to several units. We deal with the case of preemption PCOSS, where a few polynomial algorithms are known for its OSS counterpart. The scheduling problem is equivalent to the problem of conflict graph colouring. The restriction on the number of resource units bounds the size of colour classes. We thus study the problem of bounded vertex colouring. A new bound for the makespan is presented, and it is shown that for a 2-bounded colouring the bound is attainable. Some insight about a special case of PCOSS, composed of identical jobs, is given. The model correlates to a real-life timetabling project of assigning technicians to vehicles in a garage, with an additional resource, such as vehicle lift.

Complexity of cyclic job shop scheduling problems for identical jobs with no-wait constraints

Complexity of cyclic job shop scheduling problems for identical jobs with no-wait constraints

A subset-sum type formulation of a two-agent single-machine scheduling problem

We tackle a single-machine scheduling problem, characterized by two sets of identical jobs contributing to a common objective function, aimed at balancing the average completion times.For solving this problem, that we show it reduces to a particular case of the subset-sum problem, we propose an exact algorithm, pointing out the existence of different optimal solutions. Without considering explicitly the job-position assignment procedure, which necessarily would require at least a linear time, the problem is solvable in constant time. A variant of such a problem is also considered.

Complexity of Cyclic Job Shop Scheduling Problems for Identical Jobs with No-Wait Constraints

Complexity of Cyclic Job Shop Scheduling Problems for Identical Jobs with No-Wait Constraints

Scheduling with release dates and preemption to minimize multiple max-form objective functions

In this paper, we study multi-agent scheduling with release dates and preemption on a single machine, where the scheduling objective function of each agent to be minimized is regular and of the maximum form (max-form). The multi-agent aspect has three versions, namely ND-agent (multiple agents with non-disjoint job sets), ID-agent (multiple agents with an identical job set), and CO-agent (multiple competing agents with mutually disjoint job sets). We consider three types of problems: The first type (type-1) is the constrained scheduling problem, in which one objective function is to be minimized, subject to the restriction that the values of the other objective functions are upper bounded. The second type (type-2) is the weighted-sum scheduling problem, in which a positive combination of the objective functions is to be minimized. The third type (type-3) is the Pareto scheduling problem, for which we aim to find all the Pareto-optimal points and their corresponding Pareto-optimal schedules. We show that the type-1 problems are polynomially solvable, and the type-2 and type-3 problems are strongly NP-hard even when all jobs’ release dates are zero and processing times are one. When the number of the scheduling criteria is fixed and they are all lateness-like, such as minimizing Cmax, Fmax, Lmax, Tmax, and WCmax, where WCmax is the maximum weighted completion time of the jobs, the type-2 and type-3 problems are polynomially solvable. To address the type-3 problems, we develop a new solution technique that guesses the Pareto-optimal points through some elaborately constructed schedule-configurations.

Scheduling identical jobs on uniform machines with a conflict graph

This paper addresses the problem of scheduling n identical jobs on a set of m parallel uniform machines. The jobs are subjected to conflicting constraints modelled by an undirected graph G, in which adjacent jobs are not allowed to be processed on the same machine. Minimising the maximum completion time in the schedule (makespan Cmax) is known to be NP-hard. We prove that when G is restricted to complete bipartite graphs the problem remains NP-hard for arbitrary number of machines, however, if m is fixed an optimal solution can be obtained in polynomial time. To solve the general case of the problem, we propose mixed-integer linear programming (MILP) formulations alongside with lower bounds and heuristic approaches. Furthermore, computational experiments are carried out to measure the performance of the proposed methods.

Scheduling Dual-Armed Cluster Tools for Concurrent Processing of Multiple Wafer Types With Identical Job Flows

As the order size for modern fabs tends to be smaller, fabs wish to process a class of similar wafer lots at a tool concurrently to reduce the work-in-progress lots as well as the total manufacturing lead time. We examine a scheduling problem for a dual-armed cluster tool that simultaneously produces multiple wafer types with identical wafer flow patterns but different process times. We prove that the conventional swap sequence, which is optimal and prevalently being used for single-wafer-type processing, is also optimal for such concurrent processing. We then propose a way of determining a release sequence of wafer types into the tool, called cycle plan , that maximizes the utilization of parallel chambers and hence increases the tool throughput rate. We present conditions for which the parallel chambers are shared by all wafer types and their workloads are evenly balanced so as to maximize the throughput rate. We also report the experimental results. Note to Practitioners —This paper suggests how to operate cluster tools for concurrent processing of similar wafer types. The results ensure that the conventional swap sequence is still effective for concurrent processing. We also provide a simple strategy of mixing different wafer types and the optimal release sequence for the wafers. We confirm that the tool throughput can be significantly improved when the release sequence of wafers is properly determined.

The Importance of Gender Congruence in Corporate Social Responsibility: Field Experimental Evidence of Applicant Interest

To uncover the antecedents of workplace gender segregation, scholars have largely focused on how men and women sort into different occupations and industries. Gender segregation does not only vary at the industry level but also at the organizational level, with some firms having greater degrees of segregation than others. This study advances supply-side explanations of gender segregation by drawing on theories of congruence to uncover a unique organization-level driver. We argue and show that congruence between leadership gender and organizational claims is a key mechanism that drives job-seeker interest. Specifically, organizational claims are gender-typed, such that social claims engender the female stereotype whereas business claims engender the male stereotype. Thus, while female-led organizations making social claims are gender congruent, male-led firms making the same claims are gender incongruent. Beyond demonstrating a general jobseeker preference for congruence, we argue and show that female job seekers are most interested in working for organizations that are both congruent and provide credible signals that they are fair and equitable employers. The (in)congruence of leadership gender and organizational claims thus affects the gender composition of applicant pools for otherwise identical jobs.

Scheduling on uniform parallel machines with periodic unavailability constraints

Scheduling problems under unavailability constraints has become a popular research topic in the last few years. Despite it’s important application in the real world, the uniform parallel machine scheduling problem was the least studied due to its complexity. In this paper, we investigated the uniform parallel machine scheduling problem under deterministic availability constraints. Each machine is subject to one unavailability period. Different versions of the problem regarding the type of jobs (identical and non-identical) and the performance measures (the total completion times and the makespan) were studied. For the case of identical jobs and for both performance measures, we developed linear programming models and optimal algorithms to provide a solution to the problem. For the case of non-identical jobs, we proved that the problem is NP-hard and propose a quadratic program. Because, this later cannot solve problems with very large number of jobs and machines, a heuristic was developed to find near optimal solutions to the problem especially with very large number of jobs and machines. The computational results showed that the heuristic’s performance is very high regardless the dimensions of problem instances.

SPA programs as a method of worksite health promotion

Introduction: Recent research has shown, that in the current work environment, there is an established connection between a worker`s surroundings and working conditions, and their level of concentration and awareness, as well as the strong effectiveness of detoxicating SPA treatments in reducing the intensity of stress that an employee endures. The nature of work, as well as the environment in which it is carried out are important factors which affect the health and satisfaction of the worker, carrying it out. The negative effects that these factors contribute to could be counteracted by detoxicating SPA treatments. Aim: To research the positive effects of including detoxicating SPA treatments as a preventative measure against stress and its effects on the efficiency and productivity of employees. Materials and Methods : A comparison has been made between the effectiveness and productivity of people, working primarily intellectually taxing jobs in providing services, in the absence of detoxicating SPA treatments, and the effectiveness and productivity of people working identical jobs, who were given such treatments. The methods utilized for conducting the research are a corrective test, where the experimental and control groups, both consisting of 11 people, were made to mark out specific characters in a random string of characters, and a test, where the same groups were made to draw a curve inside of boundaries, describing a smooth zig-zag pattern, without escaping the said boundaries or lifting their hand. These tests were carried out at the beginning and end of a normal workday. Results and Discussion: A trend of delayed and reduced fatigue has been noticed in the subjects who were given detoxicating SPA treatments. Conclusion: An increase in the health and productivity of employees, primarily carrying out intellectually taxing work under psycho-emotional stress and hypokinesia in the department of provision of services can be achieved by utilizing well-developed regulation of work and rest hours and the inclusion of detoxicating SPA treatments.

Perceived organizational support-burnout-satisfaction relationship in workers with disabilities: The moderation of family support.

Our study tests the perceived organizational support-burnout-satisfaction relationship based on stressor-strain-outcome model of stress (Koeske & Koeske, ) and on the conservation of resources theory (Hobfoll, ) in workers with disabilities employed in ordinary or competitive jobs (open labor market), analyzing the relationship between perceived organizational support, family support, job satisfaction and burnout. We use a sample of 246 workers with physical, motor, sensory and psychological disabilities working in ordinary jobs. To test our proposed model we used a regression-based path analysis using PROCESS software, which is a computational tool for estimating and probing interactions and the conditional indirect effects of moderated mediation models. We find that the positive relationship between organizational support and job satisfaction was partially mediated by the levels of cynicism and the relationship between burnout and job satisfaction was moderated by family support. Employees with low support from family had identical job satisfaction with high burnout or low burnout, but employees with high support from family when they had high burnout had lower job satisfaction than when they had low burnout, indicating that the support outside work could have a negative effect in workers' life. Practical implications and future research are discussed and proposed.

Two-machine hybrid flowshop scheduling with identical jobs: Solution algorithms and analysis of hybrid benefits

We study two-machine hybrid flowshop scheduling with identical jobs. Each job consists of two tasks, namely a flexible task and a fixed task. The flexible task can be processed on either machine, while the fixed task must be processed on the second machine. The fixed task can only be processed after the flexible task is finished. Due to different technological capabilities of the two machines, the flexible task has different processing times on the two machines. Our goal is to find a schedule that minimises the makespan. We consider two variants of the problem, namely no buffer and infinite buffer capacity between the two machines. We present constant-time solution algorithms for both variants. In addition, analysing the relationship between the hybrid benefits and performance difference between the two machines, we find that, for the infinite-buffer case, increasing the technological level of the second machine does not necessarily increase the hybrid benefits.

Determining optimal sizes of bounded batches with rejection via quadratic min-cost flow

In this article, we consider a single machine scheduling problem, in which identical jobs are split into batches of bounded sizes. For each batch, it is allowed to produce less jobs than a given upper bound, that is, some jobs in a batch can be rejected, in which case a penalty is paid for each rejected job. The objective function is the sum of several components, including the sum of the completion times, total delivery cost, and total rejection cost. We reduce this problem to a min-cost flow problem with a convex quadratic function and adapt Tamir's algorithm for its solution.© 2017 Wiley Periodicals, Inc. Naval Research Logistics, 2017

Scheduling of unit-length jobs with bipartite incompatibility graphs on four uniform machines

Abstract In the paper we consider the problem of scheduling n identical jobs on 4 uniform machines with speeds s1 ≥ s2 ≥ s3 ≥ s4, respectively. Our aim is to find a schedule with a minimum possible length. We assume that jobs are subject to some kind of mutual exclusion constraints modeled by a bipartite incompatibility graph of degree Δ, where two incompatible jobs cannot be processed on the same machine. We show that the general problem is NP-hard even if s1 = s2 = s3. If, however, Δ ≤ 4 and s1 ≥ 12s2, s2 = s3 = s4, then the problem can be solved to optimality in time O(n1.5). The same algorithm returns a solution of value at most 2 times optimal provided that s1 ≥ 2s2. Finally, we study the case s1 ≥ s2 ≥ s3 = s4 and give a 32/15-approximation algorithm running also in O(n1.5) time.

Construction of cyclic schedules in presence of parallel machines

We consider the problem of processing some identical jobs with a complicated technological route on some production line in presence of parallel machines. Under some constrains on the number of jobs processed simultaneously, a cyclic schedule is desired with minimum cycle duration. Some algorithm for construction of an exact solution is proposed and substantiated. Also, we found the case of pseudopolynomially solvable problem.

Inclusive Recruitment? Hiring Discrimination Against Older Workers

Addressing population ageing requires a rise in the activity rates of older workers. In this study, a field experiment for the period 2013-2015 in the UK, suggests that age discrimination persists at alarming levels. It shows that when two applicants engage in an identical job search, the older applicant would gain fewer invitations for interviews regardless of her/his experience or superiority for the appointment. The results also suggest that older applicants face higher occupational access constraints for blue-collar jobs than white-collar/pink-collar jobs, and that women face greater age discrimination than men. Worryingly, the outcomes suggest that older applicants gain poorer access to vacancies than younger applicants irrespective of written commitments to equal opportunities.The design of the study suggests that discrimination results from distaste for older applicants, which has not been eliminated by the introduction of anti-discrimination legislation. Eliminating ageism in recruitment requires organizations to adopt more inclusive HR policies at the earliest stages of the recruitment process. Social dialogue has a crucial role to play in shaping inclusive and discrimination free recruitment policies such that shared values and beliefs are not age-discriminatory but rather recognize the strengths and potential of workers from different age groups.

Scheduling of Identical Jobs with Bipartite Incompatibility Graphs on Uniform Machines. Computational Experiments

Abstract. In the paper we consider the problem of scheduling of unit-length jobs on 3 or 4 uniform parallel machines to minimize schedule length or total completion time. We assume that jobs are subject to some kind of mutual exclusion constraints, modeled by a bipartite graph of bounded degree. The edges of the graph correspond to pairs of jobs that cannot be processed on the same machine. Although the problem is generally NP-hard, we show that under some conditions imposed on machine speeds and the structure of incompatibility graph our problem can be solved to optimality in polynomial time. Theoretical considerations are accompanied by computer experiments with some particular model of scheduling.

A Faster FPTAS for a Supply Chain Scheduling Problem to Minimize Holding Costs with Outsourcing

This paper addresses a scheduling problem in a flexible supply chain where the jobs can be either processed in house, or outsourced to a third-party supplier with the goal of minimizing the sum of holding and delivery costs subject to an upper bound on the outsourcing cost. The problem with identical job processing times has been proved as binary [Formula: see text]-hard one and a fully polynomial time approximation scheme (FPTAS) that runs in [Formula: see text] time has also been given. The aim of this paper is to derive a more effective FPTAS running in [Formula: see text] time for this problem.

Employee, Contractor, or Student? Four Legal Decisions Illustrate Differences in Laboratory Worker Protections

Many laboratory work settings utilize blended staffing, with employees, contractors, and students assigned duties in the same location. Employees and contractors may have identical job titles and d...