We review and develop different tractable approximations to individual chance-constrained problems in robust optimization on a variety of uncertainty sets show their interesting connections with bounds the conditional-value-at-risk (CVaR) measure. extend idea joint provide new formulation that improves upon standard approach. Our approach builds classical worst-case bound for order statistics is applicable even if constraints are correlated. an application model network resource allocation...

We develop practical operations research models to support decision making in the design and management of public bicycle-sharing systems. a network flow model with proportionality constraints estimate bicycles within number trips supported, given an initial allocation at each station. also examine effectiveness periodic redistribution greater flow, impact on docks needed. conduct our numerical analysis using transit data from train operators Singapore. Given that substantial proportion...

We study the stochastic transportation-inventory network design problem involving one supplier and multiple retailers. Each retailer faces some uncertain demand, safety stock must be maintained to achieve suitable service levels. However, risk-pooling benefits may achieved by allowing retailers serve as distribution centers for other The is determine which should how allocate centers. Shen et al. (2003) formulated this a set-covering integer-programming model. pricing that arises from column...

We propose a semidefinite optimization (SDP) model for the class of minimax two-stage stochastic linear problems with risk aversion. The distribution second-stage random variables belongs to set multivariate distributions known first and second moments. For problem objective, we provide tight SDP formulation. right-hand side is NP-hard in general. In special case, can be solved polynomial time. Explicit constructions worst-case are provided. Applications production-transportation single...

In this paper, we study the distribution network design problem integrating transportation and infinite horizon multiechelon inventory cost function. We consider trade-off between cost, direct shipment facility location in such a system. The is to determine how many warehouses set up, where locate them, serve retailers using these warehouses, optimal policies for retailers. objective minimize total inventory, transportation, costs. To best of our knowledge, none papers area has explicitly...

This article considers the value of portfolio procurement in a supply chain, where buyer can either procure parts for future demand from sellers using fixed price contracts or, option or tap into market spot purchases. A single-period problem when both product and are random (and possibly correlated) is examined optimal strategy constructed. shortest-monotone path algorithm provided general to obtain solution resulting expected minimum cost. In event that independent, simplifies...

In this paper we investigate a stochastic appointment-scheduling problem in an outpatient clinic with single doctor. The number of patients and their sequence arrivals are fixed, the scheduling is to determine appointment time for each patient. service durations stochastic, only mean covariance estimates known. We do not assume any exact distributional form durations, solve distributionally robust schedules that minimize expectation weighted sum patients' waiting doctor's overtime. formulate...

The concept of chaining, or in more general terms, sparse process structure, has been extremely influential the flexibility area, with many large automakers already making this cornerstone their business strategies to remain competitive industry. effectiveness strategy, using chains other structures, validated numerous empirical studies. However, best our knowledge, there have relatively few concrete analytical results on performance such vis-á-vis full system, especially when system size is...

We examine how to design a flexible process structure for production system match supply with demand more effectively. argue that good structures are essentially highly connected graphs, and we use the concept of graph expansion (a measure connectivity) achieve various insights into this problem. Whereas existing literature on flexibility has focused expected performance structure, analyze in paper worst-case problem under general setting, which encompasses large class objective functions....

In recent years, supply chains are more prone to disruptions. The impact on performance depends the system's ability discover and then recover after disruption has occurred. this paper, we proposed a new method integrate probabilistic assessment of risks into Risk Exposure Index (REI) approach previously by Simchi-Levi et al. measure chain resiliency analyzing worst-case CVaR (WCVaR) total lost sales under We show that optimal strategic inventory positioning strategy in model can be fully...

We discuss some recent developments in smart city initiatives across the world to motivate opportunities and challenges that such pose, we categorize them into three themes: data access collection, end-user utility, economic viability of different solutions. recognize academic literature can help addressing these is at its nascent state provide guidelines on how manufacturing service operations management scholars contribute global movement.

This paper studies how to schedule medical appointments with time-dependent patient no-show behavior and random service times. The problem is motivated by our of independent datasets from countries in two continents that unanimously identify a significant time-of-day effect on show-up probabilities. We deploy distributionally robust model, which minimizes the worst-case total expected costs waiting provider’s idling overtime, optimizing scheduled arrival times patients. model challenging...

Intelligent part‐to‐picker systems are spreading across a broad range of industries as preferred solutions for agile order fulfillment, wherein mobile racks carried by robots and moved to stations where human pickers can pick items from them. Such raise the challenge designing good work schedules pickers; they also give rise new class operational scheduling problems in human–robot coordinated picking systems. This studies problem finding suitable robot schedule that takes into account...

Problem definition: The Singapore government has recently proposed the concept of “Locker Alliance” (LA), an interoperable network public lockers in residential areas and hot spots community, to improve efficiency last mile parcel delivery operations. This is complement existing infrastructure, composed mainly proprietary collection points commercial set up by large companies. How do we determine density coverage LA promote adoption locker pickup Singapore? What will be impact on profile...

Problem definition: Online food delivery (OFD) platforms have witnessed rapid global expansion, partly driven by shifts in consumer behavior during the COVID-19 pandemic. These enable customers to order conveniently from a diverse array of restaurants through their mobile phones. A core functionality these is algorithmic matching drivers orders, which focus our study as we aim optimize this driver-order process. Methodology/results: We formulate real-time algorithms that take into account...

We study the classical stable marriage and roommates problems using a polyhedral approach. propose new LP formulation for problem, which has feasible solution if only underlying problem matching. Furthermore, certain special weight functions on edges, we construct 2-approximation algorithm optimal problem. Our technique exploits features of geometry fractional solutions this formulation. For show that related allows us to express any in polytope as convex combination solutions. This also...

We study strategic issues in the Gale-Shapley stable marriage model. In first part of paper, we derive optimal cheating strategy and show that it is not always possible for a woman to recover her women-optimal partner from men-optimal matching mechanism when she can only cheat by permuting preferences. fact, show, using simulation, chances benefit are slim. second consider two-sided market found Singapore. used Ministry Education (MOE) placement primary six students secondary schools,...

We analyze the problem faced by companies that rely on TL (Truckload) and LTL (Less than Truckload) carriers for distribution of products across their supply chain. Our goal is to design simple inventory policies transportation strategies satisfy time varying demands over a finite horizon, while minimizing system wide cost taking advantage quantity discounts in structures. For this purpose, we study effectiveness restricting class zero-inventory-ordering (ZIO) single-warehouse multiretailer...

Given a discrete maximization problem with linear objective function where the coefficients are chosen randomly from distribution, we would like to evaluate expected optimal value and marginal distribution of solution. We call this persistency for optimization under uncertain objective, probability mass solution is named persistence value. In general, difficult solve, even if coefficient well specified. paper, solve subclass when assumed belong class distributions defined by given...

As organizations globalize to reach new markets and achieve higher production sourcing efficiencies, logistics will play an increasingly important role in moving materials products throughout the organizations’ supply chains. For many companies, third party providers (or providers) represent a viable effective alternative fulfilling their own requirements. Amidst growing competition, must strategize determine how they want position services terms of cost, quality, features, value‐added...

In today’s highly competitive environment, many companies are going global to acquire market share and take advantage of higher production sourcing efficiencies. A key determinant business performance is the role logistics function in ensuring smooth flow materials, products information throughout company’s supply chains. To compete effectively, must recognize strategic importance function. The management chain practices Singapore examined. framework proposed classify according extent that...

Baïou and Balinski characterized the stable admissions polytope using a system of linear inequalities. The structure feasible solutions to this inequalities—fractional matchings—is focus paper. main result associates geometric with each fractional matching. This insight appears be interesting in its own right, can viewed as generalization lattice (for integral matchings) matchings. In addition obtaining simple proofs many known results, is used prove following two results: First, it shown...