Identical Jobs Research Articles

Discovering the Properties of a Problem of Scheduling Battery Charging Jobs to Minimize the Total Time with the Use of Harmonic Numbers

In this work, we consider a problem from the field of power-aware scheduling in which a fleet of electric vehicles have to be charged in a minimum time. Each vehicle is equipped with a lithium-ion battery of a given capacity. The initial power used for charging each battery is known, whereas it is assumed that the power drops to zero at the moment when the battery gets fully loaded. The power usage function is linear and decreasing. The charging jobs are nonpreemptable and independent, whereas the total available amount of power is limited. The objective is to minimize the schedule length. In this paper, we analyze the case of a problem with identical jobs that already cover a wide variety of practical situations. By employing inverses of natural numbers, similar to harmonic series, we prove two properties of this case, and we also discuss the phenomenon of the stabilization of the difference between the start times of two successive jobs in a schedule. We also take under examination a few special cases of the problem. Some conclusions and directions for future research are given.

Common due-date assignment problems with fixed-plus-linear earliness and tardiness costs

We study single machine scheduling and common due-date assignment problems. The cost considered is fixed plus linear, i.e., jobs are penalized by two cost components: (i) a variable cost which is proportional to their earliness/tardiness values, (ii) a fixed cost which is independent of their actual earliness/tardiness values. For the general version of this problem, three heuristics are introduced and tested. We also study a number of modifications and special cases. We focus first on the special case of identical job processing times. Both versions of minsum and minmax are shown to have a polynomial time solution, even with the additional option of job rejection. Another special case of variable earliness cost and fixed tardiness cost is also studied. For this NP-hard problem, a pseudo-polynomial dynamic programming algorithm is introduced and tested. An extension to the case of bounded rejection cost, and a modified version with an additional bound on the total tardiness cost, are also studied. The solution algorithms for these problems are tested numerically as well. The last studied problem is that of job-independent cost components. This version, which generalizes the first and most cited due-date assignment model, is shown to have a polynomial time solution.

Makespan minimization in reentrant flow shop problem with identical jobs

Makespan minimization in reentrant flow shop problem with identical jobs

"Are you feeling safe?": an investigation of psychosocial safety climate in the relations of job characteristics and employee exhaustion and engagement.

Psychosocial safety climate (PSC) is defined as the corporate climate in relation to employees' perceptions of organizational policies, procedures, and practices for the protection of employee psychosocial safety and well-being. The present study was based on the Demand-Induced Strain Compensation (DISC) Model and proposed that the interplay between identical job demands and resources would be conditioned by PSC. Particularly, high levels of PSC would enable employees to optimally perceive and utilize more job resources in dealing with corresponding job demands. A study was conducted among 406 Chinese workers from various occupational sectors. The findings of hierarchical regression analyses suggested that PSC a) mitigates the negative relation between emotional resources and exhaustion, b) enhances the positive relation between emotional resources and work engagement, and c) mitigates the negative relation between emotional demands and work engagement. We also found that PSC is a compensatory factor for low cognitive resources and demands encouraging high work engagement. Although we did not find the proposed three-way interactions, the present findings support the idea that high PSC is a fundamental contextual factor conducive to workers' health and well-being, especially in perceiving and obtaining emotional resources.

Scheduling coupled tasks on parallel identical machines

In many applications in the context of patient appointment scheduling there are recurring tasks with fixed delays between them. These tasks are commonly referred to as coupled-task jobs. In the coupled-task settings, each job consists of two tasks whereby the second task must start processing after an exact time lag following the completion of the first task. In this paper, we introduce the problem of scheduling a set of coupled-task jobs on parallel identical machines with the objective function of minimizing the makespan. We study the computational complexity of the general problem, as well as its special cases. We prove that the majority of these problems are (strongly) NP-hard. Nonetheless, we provide the optimal scheduling policy for two settings consisting of identical jobs. An important result of our work includes showing that the existence of a (2-ε)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(2-\\varepsilon )$$\\end{document}-approximation algorithm for the problem implies P=NP\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$P=NP$$\\end{document}. The latter result improves a recently proposed bound for the open-shop counterpart as well.

The Gendering of Job Postings in the Online Recruitment Process

Gender segregation remains a significant problem in many occupations and organizations. To solve this problem, many U.S. employers now seek to craft gender-neutral job postings. In this article, we investigate whether such employer recruitment efforts are successful in encouraging women and men to apply equally for jobs. Specifically, we move beyond the well-studied effects of the gender typing of occupations, organizations, and industries to study the extent to which the recruiting language used in job postings influences the actual preapplication behavior of job seekers of different genders. Using unique data from both a large-sample observational field study (Study 1) and a field experiment study (Study 2) of real online job postings, we first assess the gendered language mechanism by testing whether stereotypical femininity in the wording that recruiters use to advertise otherwise identical jobs differently influences female and male job seekers’ interest in applying. We then assess the recruiter gendering mechanism by testing whether the gender of the recruiter and the femininity in the wording recruiters use when presenting themselves to job seekers further contribute to gender job search disparities. Our analyses ultimately show negligible effects for both the gendering of job postings or of the job poster, and we therefore conclude that, in practice, employers’ efforts to simply tweak the language of recruitment messages do not matter much for gender equality and diversity. This paper was accepted by Olav Sorenson, organizations. Funding: The authors received financial support from the James S. Hardigg (1945) Work and Employment Fund and the Massachusetts Institute of Technology Sloan School of Management. Supplemental Material: The data files are available at https://doi.org/10.1287/mnsc.2023.4674 .

Abstract TMP40: Cost Analysis Of A Pooled Coordinator Model Versus Traditional Staffing For Acute Stroke Trials

Introduction: Enrollment in acute stroke clinical trials (ASCTs) is complex and unpredictable. Traditional staffing models (TSMs) of research coordinator coverage assign a single research coordinator to cover specific clinical trials, whereas pooled staffing models (PSMs) utilize staff research coordinators to cross-cover multiple clinical trials, typically beyond traditional daytime hours. Methods: We calculated actual PSM costs accrued during one year (1/1/21-12/31/21) for two Phase III ASCTs (NCT03735979, NCT03785678). PSM costs were obtained from existing billing records for specific research coordinator tasks billed hourly ($78/hour) and a “retainer fee” ($690/month) for 24-7 on-call research coordinator coverage. Aspects of research coordinator work included: enrollment, data entry, query resolution, monitor visits, regulatory management, meetings, training/retraining, and patient visits. We compared PSM costs to the cost (salary + fringe) of a TSM full-time research nurse (1.0 full-time equivalent [FTE]) in the identical job class and salary as those employed in the PSM. Results: The estimated one-year cost (salary + fringe) of a 1.0 FTE RN research coordinator was $109,755.36. During the study period, there were 19 enrollments in NCT03735979; 9 occurred outside daytime working hours. The PSM cost was $60,813, equivalent to 0.55 FTE of coordinator coverage in a TSM with 90.0% more enrolled subjects. Additionally, there were 6 enrollments for NCT03785678; 4 outside daytime working hours. The PSM cost was $69,857.00, equivalent to the cost of 0.64 FTE of standardized research coordinator in a TSM with 200% more enrolled subjects. Conclusions: We demonstrated that a PSM for ASCT can be cost-effective for individual studies while increasing enrollment opportunities through 24-7 coordinator coverage. PSMs may offer a solution to the staffing and coverage challenges faced by many institutions seeking to participate in emergent clinical trials. Cost increases or savings with the PSM model would be dependent upon staff compensation, rates of enrollment, and reimbursement at individual sites.

Faster algorithms for bicriteria scheduling of identical jobs on uniform machines

<p style='text-indent:20px;'>This paper studies the problem of scheduling <inline-formula><tex-math id="M1">\begin{document}$ n $\end{document}</tex-math></inline-formula> jobs with equal processing times on <inline-formula><tex-math id="M2">\begin{document}$ m $\end{document}</tex-math></inline-formula> uniform machines to optimize two criteria simultaneously. The main contribution is an <inline-formula><tex-math id="M3">\begin{document}$ O(n\log m+n^3) $\end{document}</tex-math></inline-formula>-time algorithm for two general min-max criteria, improving the previous <inline-formula><tex-math id="M4">\begin{document}$ O(n\log m+n^4) $\end{document}</tex-math></inline-formula> time complexity. For a particular min-sum criterion (total weighted completion time or total tardiness) in combination with a general min-max criterion, <inline-formula><tex-math id="M5">\begin{document}$ O(n\log m+n^3) $\end{document}</tex-math></inline-formula>-time algorithms are also obtained, improving the previous <inline-formula><tex-math id="M6">\begin{document}$ O(n\log m+n^3\log n) $\end{document}</tex-math></inline-formula> time complexity. The algorithms can produce all Pareto optimal points together with the corresponding schedules.</p>

A matheuristic for flexible job shop scheduling problem with lot-streaming and machine reconfigurations

Multi-variety and small-batch production mode enables manufacturing industries to expeditiously satisfy customers' personalised demands, where a large amount of identical jobs can be split into several sublots, and be processed by reconfigurable machines with multiple machining technics. However, such highly flexible manufacturing environments bring some intractable problems to the production scheduling. Mathematical programming and meta-heuristic methods become less efficient when a scheduling problem contains both discrete and continuous optimisation attributes. Therefore, matheuristic, which combines advantages of the two methodologies, is regarded as a promising solution. This paper investigates a flexible job shop scheduling problem with lot-streaming and machine reconfigurations (FJSP-LSMR) for the total weighted tardiness minimisation. First, a monolithic mixed integer linear programming (MILP) model is established for the FJSP-LSMR. Afterwards, a matheuristic method with a variable neighbourhood search component (MH-VNS) is developed to address the problem. The MH-VNS adopts the classical genetic algorithm (GA) as the framework, and introduces two MILP-based lot-streaming optimisation strategies, LSO1 and LSO2, to improve lot-sizing plans with varying degrees. Four groups of instances are extended from the well-known Fdata benchmark to evaluate the performance of proposed MILP model, LSO1 and LSO2 components, and MH-VNS. Numerical experimental results suggest that LSO1 and LSO2 are efficient in different scenarios, and the proposed MH-VNS can well balance the solution quality and computational costs for reasonably integrating the GA- and MILP-based local search strategies. In addition, a complicated FJSP-LSMR case is abstracted from a real-world shop floor for processing large-sized structural parts to further validate the MH-VNS.

Understanding Barriers-to-Hire in Corporate Renewal

I develop a theory to explain why talent acquisition for corporate renewal can be costly for firms. I argue that to attract people who can grow firms in new or different directions, firms may need to offer higher wages to (1) compensate for their industry affiliation as a categorical constraint and (2) overcome frictions associated with hiring across industries. Analyses of more than 14 million online job posts support my theory of talent acquisition for corporate sustainability: firms in environmentally sensitive (or “brown”) industries are found to offer higher wages for sustainability-related (or “green”) jobs than firms in other industries for almost identical jobs; this wage premium decreases with the rising demand for green jobs within a given brown industry over time, and when ideological conflicts or career-related risks are mitigated. Supplemental analyses using survey data, employee online reviews, and field-level placement records render further support for the mechanisms. These findings bring an intriguing paradox to light: despite firms in brown industries having the most urgent need to adopt sustainable practices, hiring people capable of delivering such changes is a real challenge. Although firm-specific efforts that alleviate jobseekers’ ideological and career-related concerns may lower the barriers-to-hire, firms do pay more to hire people for corporate renewal, especially when constrained by the way firms are perceived under the existing market structure.

A multi-machine scheduling solution for homogeneous processing: Asymptotic approximation and applications

In the context of job scheduling in parallel machines, we present a class of binary programs for the minimization of the τ-norm of completion time variances (a flexible measure of homogeneity in multi-machine job processing). Building on overlooked properties of the min completion time variance in a single machine and on an equivalent bilevel formulation, our approach provides asymptotic approximations (with quadratic convergence) in the form of lower and upper bounds. While resulting in almost identical solutions, these bounds can be computed more efficiently than the original τ-norm minimization problem. Further, dominance properties are enforced as linear constraints to improve the characterization of the exact solutions by these asymptotic approximations. On the empirical side, the proposed methodology is applied to three real contexts of processing services: nursing home management, IT troubleshooting service, and 311 call centers. Our numerical studies reveal that the proposed lower bound problem can be solved in less than one third of computation time, in comparison to the exact problem, while resulting in almost identical jobs sequences. Additionally, considering large-scale simulated instances with up to 450 jobs, our upper bound problem outperforms the state-of-the-art heuristic method in terms of solution quality in 100% of the analyzed instances.

Discrete-time strategic job arrivals to a single machine with waiting and lateness penalties

A single machine processes a random number of identical jobs on a first-come first-served (FCFS) basis. Processing times are independent and identically distributed with a general integral distribution. Each job is held by a strategic player who needs to choose a time slot to arrive at. The individual objective is to reduce the sum of two types of linear in time costs: lateness and waiting. The resulting decision making model is, then, a symmetric non-cooperative game. We derive a symmetric Nash equilibrium for this game, and discuss its structural properties.

Estimating the elasticity of labor supply to a firm: results from a field experiment

ABSTRACT ‘New Monopsony’ models imply that firms can possess wage-setting power even in competitive markets so long as they face an upward-sloping labour supply curve due to labour market frictions. However, previous research has yielded wildly different estimates of the elasticity of labour supply to a firm. Using a field experiment where identical job offers were posted with varying wages in statistically matched areas, I estimate that the elasticity of labour supply to a restaurant to be quite high, between 11.6 and 20.9, implying that workers are hired at wages between 92% and 95% of their marginal products. These results provide evidence for a model where firms only possess wage-setting power over incumbent employees, while new employees are hired at wages close to their marginal products. The policy implications of such a model are discussed.

A Boss Like Me*

There is extensive evidence of hiring decisions being biased with respect to applicant race and gender. We look at the other side of the hiring transaction, presenting what we believe to be first systematic investigation of bias in labor supply. In a choice experiment we examine decisions of job seekers faced with 14,544 pairs of job offers, with varying characteristics. White job seekers are around 11% more likely to choose a job offered by a white manager than an otherwise identical job offered by a black, while black respondents are 17% less likely. Estimates of intensity of preference, measured by willingness to accept a lower hourly wage, over employer attributes are reported. We find little evidence of bias with respect to gender. The results suggest a mechanism for disadvantage on basis of race in a competitive market for managerial or entrepreneurial roles

Quality improvement study into the effectiveness of the semi-custom, prefabricated shoe insert program (Quadrastep System) at reducing complaints of discomfort in an industrial setting.

A common source of reduced productivity and lost work time in the industrial setting is musculoskeletal discomfort in the feet, knees, hips, and low back. Even when working identical job posts, these symptoms can vary widely between employees, and could potentially be caused by intrinsic foot biomechanics coupled with long-term standing activities. Therefore, to prevent injury and reduce daily discomfort, onesize-fits-all approaches such as anti-fatigue mats or off-the-shelf shoe insoles may be less effective than treating each employee’s specific biomechanical traits. The Quadrastep System is a prefabricated, semi-custom shoe insert system that bridges the gap between more expensive, fully customized orthotics and off-the-shelf options. We studied the effectiveness of the system in a large manufacturing plant by assessing and providing Quadrastep inserts to 28 volunteers. After 2 months of daily wear, 94% of these volunteers said they received some benefit from the inserts, while 52% reported full resolution of daily symptoms.

Reentrant flow shop with identical jobs and makespan criterion

The article focuses on the problem of a reentrant flow shop with identical jobs and makespan minimisation objective. After presenting an optimal integer programming formulation for the problem, we consider the case of unit processing times. We correct two results published a few decades ago regarding two greedy heuristic algorithms. In some cases, these algorithms lead to an optimal solution, but they are generally not optimal. We point out the advantages of each of the two heuristic algorithms and, by machine learning analysis, discuss features that differentiate between them.

The Impact of Encoding and Transport for Massive Real-time IoT Data on Edge Resource Consumption

Edge microservice applications are becoming a viable solution for the execution of real-time IoT analytics, due to their rapid response and reduced latency. With Edge Computing, unlike the central Cloud, the amount of available resource is constrained and the computation that can be undertaken is also limited. Microservices are not standalone, they are devised as a set of cooperating tasks that are fed data over the network through specific APIs. The cost of processing these feeds of data in real-time, especially for massive IoT configurations, is however generally overlooked. In this work we evaluate the cost of dealing with thousands of sensors sending data to the edge with the commonly used encoding of JSON over REST interfaces, and compare this to other mechanisms that use binary encodings as well as streaming interfaces. The choice has a big impact on the microservice implementation, as a wrong selection can lead to excessive resource consumption, because using a less efficient encoding and transport mechanism results in much higher resource requirements, even to do an identical job.

Appointment scheduling with a quantile objective

Appointment scheduling has many applications (e.g., surgery scheduling, airport gate scheduling, container vessel dockings and radiation therapy bookings) and it has a direct and significant operational and economic impact. For example, in healthcare, surgical departments are one of the main drivers of hospital costs and revenue, and appointment scheduling is used to book surgeries. Effective scheduling not only enables patients’ timely access to care but also enables more efficient operations. This becomes especially important as healthcare costs and demand are on the rise in many countries. We study appointment scheduling where there are jobs (e.g., patients, container vessels, airplanes) with random processing durations, an expensive processor (e.g., a doctor, dock crane, airport gate) and significant costs for processor idle time, processor overtime, and job waiting. The goal is to determine an appointment schedule that minimizes a measure of total costs as the objective. The appointment scheduling problem has been well studied in the literature with the expected cost objective. Almost all papers in the literature on appointment scheduling use the expected cost criterion, which may not be suitable when risk measures and/or service levels are considered. In this paper, we study this problem with a new objective: minimization of any quantile of the cost distribution, e.g., median, 90th percentile. We obtain theoretical results for some special cases and develop an algorithm for the general case. Our algorithm does not require a specific distribution assumption and can work directly with data samples. We present numerical examples with real data on surgeries. Our results show that allocated schedules based on the quantile objective with identical jobs are different than the ones generated by the expected cost objective and they do not show the well-known dome-shaped pattern but a semi-dome-shaped pattern which first increases (like the dome-shaped pattern) but then its decrease is not monotone (unlike the dome-shaped pattern). To the best of our knowledge, this is the first paper on appointment scheduling problem with the objective of the quantile function minimization.

Workload Balancing on Identical Parallel Machines: Theoretical and Computational Analysis

This paper considers the problem of assigning nonpreemptive jobs on identical parallel machines to optimize workload balancing criteria. Since workload balancing is an important practical issue for services and production systems to ensure an efficient use of resources, different measures of performance have been considered in the scheduling literature to characterize this problem: maximum completion time, difference between maximum and minimum completion times and the Normalized Sum of Square for Workload Deviations. In this study, we propose a theoretical and computational analysis of these criteria. First, we prove that these criteria are equivalent in the case of identical jobs and in some particular cases. Then, we study the general version of the problem using jobs requiring different processing times and establish the theoretical relationship between the aforementioned criteria. Based on these theoretical developments, we propose new mathematical formulations to provide optimal solutions to some unsolved instances in order to enhance the latest benchmark presented in the literature.

Congruence Between Leadership Gender and Organizational Claims Affects the Gender Composition of the Applicant Pool: Field Experimental Evidence

The extent to which men and women sort into different jobs and organizations—namely, gender differences in supply-side labor market processes—is a key determinant of workplace gender composition. This study draws on theories of congruence to uncover a unique organization-level driver of gender differences in job seekers’ behavior. We first argue and show that congruence between leadership gender and organizational claims is a key mechanism that drives job seekers’ interest. Specifically, many organizational claims are gender-typed, such that social claims activate the female stereotype, whereas business claims activate the male stereotype. Thus, whereas female-led organizations making social claims are gender-congruent, male-led firms making the same claims are gender-incongruent. Beyond demonstrating a general preference among job seekers for congruence, we also find that female job seekers are most interested in working for organizations that are simultaneously congruent and provide credible signals that they are fair and equitable employers. The congruence of leadership gender and organizational claims thus affects the gender composition of applicant pools for otherwise identical jobs.