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How to Conclude a Suspended Sports League?

M&SOM-MANUFACTURING & SERVICE OPERATIONS MANAGEMENT 2024年第5期26卷 1692-1711页

作者： Hassanzadeh, Ali Hosseini, Mojtaba Turner, John G. Univ Manchester Alliance Manchester Business Sch Manchester M15 6PB England Univ Iowa Tippie Coll Business Iowa City IA 52242 USA Univ Calif Irvine Paul Merage Sch Business Irvine CA 92697 USA

Problem definition: : Professional sports leagues may be suspended because of various reasons, such as the recent coronavirus disease 2019 pandemic. A critical question that the league must address when reopening is how to appropriately select a subset of the remaining games to conclude the season in a shortened time frame. Despite the rich literature on scheduling an entire season starting from a blank slate, concluding an existing season is quite different. Our approach attempts to achieve team rankings similar to those that would have resulted had the season been played out in full. Methodology/results: : We propose a data -driven model that exploits predictive and prescriptive analytics to produce a schedule for the remainder of the season composed of a subset of originally scheduled games. Our model introduces novel rankings -based objectives within a stochastic optimization model, whose parameters are first estimated using a predictive model. We introduce a deterministic equivalent reformulation along with a tailored Frank-Wolfe algorithm to efficiently solve our problem as well as a robust counterpart based on min -max regret. We present simulation -based numerical experiments from previous National Basketball Association seasons 2004-2019, and we show that our models are computationally efficient, outperform a greedy benchmark that approximates a nonrankings-based scheduling policy, and produce interpretable results. Managerial implications: : Our data -driven decisionmaking framework may be used to produce a shortened season with 25%-50% fewer games while still producing an end -of -season ranking similar to that of the full season, had it been played.

关键词： COVID-19 pandemic sports scheduling rankings concordance predictive analytics stochastic optimization Frank-Wolfe algorithm min-max regret math programming simulation OM practice

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Collaborative Vehicle-to-Grid Operations in Frequency Regulation Markets

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M&SOM-MANUFACTURING & SERVICE OPERATIONS MANAGEMENT 2024年第3期26卷 797-1187, C2页

作者： Mak, Ho-Yin Tang, Runyu Georgetown Univ McDonough Sch Business Washington DC 20057 USA Xi An Jiao Tong Univ Sch Management Xian 710049 Shaanxi Peoples R China

Problem definition: We study the operations of electric vehicles (EVs) providing frequency regulation services to the electric grid in vehicle -to -grid (V2G) systems. In particular, individually owned EVs collaboratively bid in the regulation market, coordinated by a platform that operates the network of charging equipment. We study how the platform determines optimal pricing incentives for drivers to plug in their EVs, accounting for heterogeneous driving schedules. Methodology/results: We model the platform's pricing optimization problem as a bilevel program: At the upper level, the platform determines hourly rebates for EV owners to plug in their EVs and capacity bids in the regulation market;at the lower level, individual travelers optimize their travel and charging schedules in response to pricing incentives. To account for uncertainties and heterogeneity in regulation market prices and travel patterns, we adopt distributionally robust optimization techniques to formulate the problem as a mixed -integer second -order cone program. We conduct a computational study based on the California Household Travel Survey data set and actual frequency regulation prices. Our results show that the ability to offer time -varying rebates and install workplace chargers can significantly improve the V2G platform's expected profits. Managerial implications: As EV adoption progresses past the nascent stage, V2G business models become more viable. Successful implementation of V2G provides economic incentive for switching to EVs, potentially helps sustain adoption growth, and complements the growth of renewable power by helping stabilize the grid. Our findings shed light on the design of driver incentives for V2G systems.

关键词： energy-related operations environmental operations logistics and transportation math programming

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Reliable Frequency Regulation Through Vehicle-to-Grid: Encoding Legislation with Robust Constraints

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M&SOM-MANUFACTURING & SERVICE OPERATIONS MANAGEMENT 2024年第2期26卷 722-722页

作者： Lauinger, Dirk Vuille, Francois Kuhn, Daniel MIT Energy Initiat & Sloan Sch Management Cambridge MA 02139 USA Direct energie CH-1014 Lausanne Switzerland Risk Analyt & Optimizat Chair Ecole Polytech Fed Lausanne CH-1015 Lausanne Switzerland

Problem definition: Vehicle-to-grid increases the low utilization rate of privately owned electric vehicles by making their batteries available to electricity grids. We formulate a robust optimization problem that maximizes a vehicle owner's expected profit from selling primary frequency regulation to the grid and guarantees that market commitments are met at all times for all frequency deviation trajectories in a functional uncertainty set that encodes applicable legislation. Faithfully modeling the energy conversion losses during battery charging and discharging renders this optimization problem nonconvex. Methodology/results: By exploiting a total unimodularity property of the uncertainty set and an exact linear decision rule reformulation, we prove that this nonconvex robust optimization problem with functional uncertainties is equivalent to a tractable linear program. Through extensive numerical experiments using real-world data, we quantify the economic value of vehicle-to-grid and elucidate the financial incentives of vehicle owners, aggregators, equipment manufacturers, and regulators. Managerial implications: We find that the prevailing penalties for nondelivery of promised regulation power are too low to incentivize vehicle owners to honor the delivery guarantees given to grid operators.

关键词： energy-related operations math programming

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Order-Optimal Correlated Rounding for Fulfilling Multi-Item E-Commerce Orders

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M&SOM-MANUFACTURING & SERVICE OPERATIONS MANAGEMENT 2023年第4期25卷 1209-1621, C2页

作者： Ma, Will Columbia Univ Grad Sch Business New York NY 10027 USA

Problem definition: We study the dynamic fulfillment problem in e-commerce, in which incoming (multi-item) customer orders must be immediately dispatched to (a combination of) fulfillment centers that have the required inventory. Methodology/results: A prevailing approach to this problem, pioneered by Jasin and Sinha in 2015, has been to write a "deterministic" linear program that dictates, for each item in an incoming multi-item order from a particular region, how frequently it should be dispatched to each fulfillment center (FC). However, dispatching items in a way that satisfies these frequency constraints, without splitting the order across too many FCs, is challenging. Jasin and Sinha in 2015 identified this as a correlated rounding problem and proposed an intricate rounding scheme that they proved was suboptimal by a factor of at most approximate to q=4 on a q-item order. This paper provides, to our knowledge, the first substantially improved scheme for this correlated rounding problem, which is suboptimal by a factor of at most 1 + ln(q). We provide another scheme for sparse networks, which is suboptimal by a factor of at most d if each item is stored in at most d FCs. We show both of these guarantees to be tight in terms of the dependence on q or d. Our schemes are simple and fast, based on an intuitive idea;items wait for FCs to "open" at random times but observe them on "dilated" time scales. This also implies a new randomized rounding method for the classical Set Cover problem, which could be of general interest. Managerial implications: We numerically test our new rounding schemes under the same realistic setups as Jasin and Sinha and find that they improve runtimes, shorten code, and robustly improve performance. Our code is made publicly available online.

关键词： inventory theory and control math programming retailing

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Capacity planning and production scheduling integration: improving operational efficiency via detailed modelling

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INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH 2022年第24期60卷 7239-7261页

作者： Yao, Xufeng Almatooq, Nourah Askin, Ronald G. Gruber, Greg Arizona State Univ Sch Comp Informat & Decis Syst Engn Tempe AZ 85281 USA Gen Motors Corp Detroit MI USA Arizona State Univ Sch Comp Informat & Decis Syst Engn Ira A Fulton Sch Engn Tempe AZ 85281 USA

Successful capacity planning and production scheduling is built on the understanding of market opportunities and the costs of capacity, production, sourcing, inventory, and distribution over the planning horizon. Increasingly, companies attempt to integrate capacity planning and production scheduling to improve upon the commonly used sequential decision process, but most related research works fail to capture the granularity of actual operational decisions and therefore may overlook potential cost-saving opportunities. The contributions of this study include: (1) a detailed integrated capacity and production scheduling model with multiple discrete and continuous options for varying short and medium-term capacity, (2) a heuristic algorithm that exploits the problem structure to solve the nonlinear mixed integer problem, (3) an evaluation of the value of the integrated model relative to traditional practice and its sensitivity to parameters, (4) a review of past contributions to integrated planning, particularly focused on IJPR, and (5) a case study originated from a world-class automobile manufacturer illustrating how the model can be applied and confirming its value relative to hierarchical and less detailed modelling approaches.

关键词： Production modelling capacity planning integration scheduling math programming

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A note on: "A hybrid Benders approach for coordinated capacitated lot-sizing of multiple product families with set-up times," by T. Bayley, H. Sural, and J. Bookbinder

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INTERNATIONAL JOURNAL OF PRODUCTION RESEARCH 2021年第14期59卷 4453-4456页

作者： Caserta, Marco Voss, Stefan IE Univ Madrid Spain IE Business Sch Madrid Spain Univ Hamburg Inst Informat Syst Hamburg Germany Pontificia Univ Catolica Valparaiso Escuela Ingn Ind Valparaiso Chile

In a recent paper by Bayley et al. [2018. "A Hybrid Benders Approach for Coordinated Capacitated Lot-Sizing of Multiple Product Families with Set-Up Times."International Journal of Production Research56 (3): 1326-1344] on a capacitated lot-sizing problem, a Benders-based approach is described. Strengthening the master problem is based on inequalities that should be valid. We provide insight indicating that this is not the case for those inequalities proposed by Bayley et al. (2018).

关键词： mixed integer linear programming math programming optimisation capacitated lot sizing

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The time buffer approximated Buffer Allocation Problem: A row-column generation approach

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COMPUTERS & OPERATIONS RESEARCH 2020年 115卷 104835-000页

作者： Alfieri, Arianna Matta, Andrea Pastore, Erica Politecn Torino Dept Management & Prod Engn Corso Duca Abruzzi 24 Turin Italy Politecn Milan Dept Mech Engn Via Masa 1 Milan Italy

One of the main problems in production systems is the buffer sizing. Choosing the right buffer size, at each production stage, that allows to achieve some performance measure (usually throughput or waiting time) is known as Buffer Allocation Problem (BAP), and it has been widely studied in the literature. Due to its complexity, BAP is usually approached using decomposition methods, under very strict system assumptions, or using simulation-optimization techniques. In this paper, the approximated mathematical programming formulation of the BAP simulation-optimization based on the time buffer concept is used. Using this approximation, buffers are modeled as temporal lags (time buffers) and this allows to use Linear programming (LP) instead of Mixed Integer Linear programming (MILP) models. Although LP models are easier to solve than MILPs, the huge dimension and the complex solution space topology of the time buffer approximated BAP call for ad hoc solution algorithms. To this purpose, a row-column generation algorithm is proposed, which exploits the theoretical properties of the time buffer approximation to reduce the solution time. The proposed algorithm has been compared with a standard LP solver (ILOG CPLEX) and with a state-of-the-art MILP solver and it proved to be better than the LP solver in most of the cases, and more robust than the MILP solver with respect to computation time. Moreover, the LP model (for flow lines) is able to solve the BAP also for assembly/disassembly lines. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Buffer allocation Simulation-optimization Assembly lines math programming Row and column generation Exact method

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An iterative approach for case mix planning under uncertainty

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OMEGA-INTERNATIONAL JOURNAL OF MANAGEMENT SCIENCE 2018年 76卷 160-173页

作者： Freeman, Nickolas Zhao, Ming Melouk, Sharif Univ Alabama Dept Informat Syst Stat & Management Sci Tuscaloosa AL 35487 USA Univ Houston Dept Decis & Informat Sci Houston TX USA

Case mix planning refers to allocating available time in the operating rooms composing an operating theater (OT) among different surgical specialties. Case mix planning is an important tool for achieving the goals of a hospital with respect to quality of care and financial position. Case mix planning is becoming increasingly prevalent as hospital reimbursement continues to shift from fee-for-service to reimbursement based on diagnostic-related groups. Existing approaches for case mix planning in the academic and medical literature follow a traditional approach that identifies a single "optimal" solution. To ensure tractability, such approaches often exclude several complicating factors such as uncertain patient arrivals, uncertain operation time requirements, and the arrival of patients requiring urgent care. The exclusions limit the applicability of the, solution in practice. Thus, we develop a multi-phase approach that utilizes mathematical programming and simulation to generate a pool of candidate solutions. Using simulation allows us to evaluate each candidate solution with respect to a broad range of strategic and operational performance measures including expected patient reimbursement, overutilization of the OT, and the utilization of downstream recovery wards. Providing a pool of solutions, instead of a single solution, gives decision-makers several options from which they may select based on hospital goals. We conduct experiments based on a large, publicly available dataset that documents patient admissions in 203 U.S. hospitals. In comparison to a more traditional single-solution approach, we show that our solution pool approach identifies case mix plans with higher expected patient reimbursement, lower overutilization of OT time, and lower variability in the number of beds required in downstream recovery wards. Published by Elsevier Ltd.

关键词： Health care management math programming Simulation

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An Integrated Supplier Selection Model with Product Life Cycle Considerations

An Integrated Supplier Selection Model with Product Life Cyc...

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作者： Titus, Richard PennState University Libraries

学位级别：Doctor of Philosophy

Cost of purchased materials account for up to 70% of the overall product cost and the consequences of supplier delivery, quality performance problems and price fluctuations can have profound negative effects for an organization. Product life cycles are increasing in length for defense applications and shortening in consumer products, such as toys, electronics, etc. These factors make the purchasing function a critical factor impacting the long term health of *** this dissertation, we begin with the investigation of the relationship between supplier quality and delivery performance and supplier attributes as part of an empirical study using an ordinal logistic regression. The results of this study are utilized to develop an integrated supplier selection model with product life cycle considerations. Supplier selection is a multiple criteria optimization problem with conflicting criteria, such as quality, delivery, service, product safety and others. Several multiple criteria sourcing models exist in the literature. Very rarely they have considered the fact that the relative importance of the supplier attributes depends on the product life cycle phase. For example, during the Introduction phase, companies may work with a single supplier emphasizing product safety, quality and delivery. Revenue targets are more important than gross profit margins. However, during the Growth phase, multiple suppliers may be used to meet surging demand and to introduce price competition among the suppliers. In the Mature phase, controlling procurement cost becomes important in order to boost the product gross profit margin. In addition, many suppliers can deliver materials needed for multiple products under various stages of the product life cycle phase. Companies may also limit the business volume to new and existing suppliers. All these factors are integrated into a general *** this thesis, a multiple criteria, multiple products, supplier selection model that explicitly co

关键词： Supplier Selection MCDM Product Life Cycle Goal programming math programming case study

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The math Gap in an Inclusive CS1 Course 18

The Math Gap in an Inclusive CS1 Course

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49th ACM SIGCSE Technical Symposium on Computer Science Education (SIGCSE)

作者： Jordan, Kris Stein, Gabi Univ N Carolina Chapel Hill NC 27515 USA

ISBN: (纸本)9781450351034

This poster investigated the data from the past year of CS1 and found overwhelming evidence that students who have taken calculus are significantly more likely to succeed and less likely to fail that those who do not. On a Fall 2016 CS1 final exam, students who had not earned credit for a first course in college-level calculus were 2.8 times more likely to fail it than those who had (p=<0.0001,N=844). The mean final score for students with calculus was an 84, and those without was 61 (p=<0.0001). The result surprised the instructor, course staff, and faculty familiar with the course because the course itself does not emphasize mathematical or scientific computing. The course was Java-based, objects-early, and introduces both object-oriented and imperative programming fundamentals. The effect was evident across a range of problems, none seemingly requiring beyond basic algebra. In the Spring of 2017, the instructor and course staff set forth to explore these questions and close the math gap discovered in the Fall of 2016. This poster further proposes to develop interventions to aid those with a lower math maturity level through introducing a specialized CS1 to better accommodate those with a lower math maturity level by reducing the pace and installing prerequisites for the established CS1. Prospective Computer Science students at liberal arts colleges and universities enter with a wide range of mathematical backgrounds. Failing to acknowledge these disparities is demoralizing to students during their first course in CS and is counter-productive to inclusivity.

关键词： math background math programming CS1 Object-oriented programming Imperative programming CS Education Inclusivity

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