Lawrence Snyder

Lawrence Snyder
Lehigh University · Department of Industrial and Systems Engineering

PhD

About

118
Publications
59,225
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
6,418
Citations
Additional affiliations
September 2003 - present
Lehigh University
Position
  • Professor (Associate)

Publications

Publications (118)
Book
Addressing the need for the study of supply chain management to evolve at the same pace as its real-world practice, Fundamentals of Supply Chain Theory presents the methodology of the topic, discussing the foundations of this emerging supply chain theory and demonstrating how recent developments build upon classical models. The authors focus on lon...
Conference Paper
Full-text available
We consider mechanisms to optimize electricity consumption both within a home and across multiple homes in a neighborhood. The homes are assumed to use energy management controllers (EMCs) to control the operation of some of their appliances. EMCs, which are a feature of the emerging SmartGrid, use both prices and user preferences to control power...
Article
Full-text available
Abstract Classical facility location models like the P-median problem (PMP) and the uncapacitated flxed-charge location problem (UFLP) implicitly assume that once constructed, the facilities chosen will always operate as planned. In reality, however, facilities \fail" from time to time due to poor weather, labor actions, changes of ownership, or ot...
Preprint
We consider issues of equity in stochastic facility location models for healthcare applications. We explore how uncertainty exacerbates inequity and examine several equity measures that can be used for stochastic healthcare location modeling. We analyze the limited literature on this subject and highlight areas of opportunity for developing tractab...
Article
Problem definition: The beer game is widely used in supply chain management classes to demonstrate the bullwhip effect and the importance of supply chain coordination. The game is a decentralized, multiagent, cooperative problem that can be modeled as a serial supply chain network in which agents choose order quantities while cooperatively attempti...
Article
A generic formulation for the optimal control of a single reacting two-body point absorber type wave-energy converter (WEC) is proposed. The formulation involves hard and soft constraints on the motion of the WEC to promote reduced damage with the aim of increasing the service life of the device. Most of the WEC control literature ignores the cost...
Preprint
Full-text available
We consider electric public transportation buses in an urban area, which can provide ancillary services to the electric grid during times in which they are not serving any public transit demand. Our model considers a single social planner who decides the optimal charging/discharging times and locations for each transit bus. By doing so, the transit...
Preprint
Full-text available
A generic formulation for the optimal control of a single wave-energy converter (WEC) is proposed. The formulation involves hard and soft constraints on the motion of the WEC to promote reduced damage and fatigue to the device during operation. Most of the WEC control literature ignores the cost of the control and could therefore result in generati...
Article
When supply disruptions occur, firms want to employ an effective pricing strategy to reduce losses. However, firms typically do not know precisely how customers will react to price changes in the short term, during a disruption. In this article, we investigate the customer's order variability and the firm's profit under several representative heuri...
Article
This article explores the concepts of ocean wave multivariate multistep forecasting, reconstruction and feature selection. We introduce recurrent neural network frameworks, integrated with Bayesian hyperparameter optimization and Elastic Net methods. We consider both short- and long-term forecasts and reconstruction, for significant wave height and...
Preprint
Full-text available
This study focuses on simultaneous decision making for stochastic multi-echelon inventory optimization problems. Mixed supply chain networks are considered that may contain assembly or distribution nodes, or both, and may use nonlinear cost structure. We present a framework which uses deep neural networks as agents responsible for finding order-up-...
Article
This study introduces a framework for the forecasting and feature engineering of multivariate processes along with their renewable energy applications. Derivative-free optimization is integrated with an ensemble of sequence-to-sequence networks to design a new resampling technique called additive resampling to exploit the repetitive behavior of tim...
Preprint
Full-text available
This research introduces a framework for forecasting, reconstruction and feature engineering of multivariate processes. We integrate derivative-free optimization with ensemble of sequence-to-sequence networks. We design a new resampling technique called additive which along with Bootstrap aggregating (bagging) resampling are applied to initialize t...
Chapter
Like all mathematical models, inventory models must balance two competing factors—realism and tractability. This chapter discusses deterministic models—first a continuous‐review model, the economic order quantity (EOQ) model, perhaps the oldest and best‐known mathematical inventory model, and some of its extensions; and then a periodic‐review model...
Chapter
Supply chain management is one of the domains in which the tools of operations research (OR) are most widely and successfully applied. But in the past few decades, the theory of supply chain management has matured to the point where it is now applied to other industries and application areas, including energy, health care, disaster relief, the envi...
Chapter
The stochastic inventory models assume that inventory is the only tool for mitigating uncertainty. In contrast, this chapter examines uncertainty mitigation using other means. The chapter deals with risk pooling, in which people physically combine the inventories used to satisfy multiple demand streams, by storing them together in the same warehous...
Chapter
The vehicle routing problem (VRP) is concerned with optimizing a set of routes, all beginning and ending at a given node (called the depot), to serve a given set of customers. This chapter discusses several construction heuristics for the VRP, and improvement heuristics. The Clarke–Wright savings heuristic is one of the best‐known heuristics for th...
Chapter
This chapter explores discusses three types of integrated supply chain models: location‐inventory, location‐routing, and inventory‐routing. It covers a location‐inventory model thoroughly, including details on mathematical formulations, solution approaches, and analytical properties, and considers some basic formulations and possible variations of...
Chapter
This chapter explains the four causes of the bullwhip effect (BWE): demand signal processing (when the demand parameters are unknown and hence forecasting techniques must be used to estimate them), rationing game (when supply is limited), order batching (when there is a fixed cost for ordering), and price speculation (when the purchase price can ch...
Chapter
This chapter examines the demand modeling techniques that can be used to predict demands for new products or products that do not have much historical data. It introduces some of the main machine learning techniques for demand forecasting. Classical forecasting methods use prior demand history to generate a forecast. Some of the methods, such as mo...
Chapter
This chapter considers inventory models in which the demand is stochastic. It focuses on periodic‐review models. The chapter first considers problems with no fixed costs and then problems with nonzero fixed costs. It assumes that unmet demands are backordered. The chapter discusses the lost‐sales assumption. It introduces two important concepts in...
Chapter
This chapter reviews models that consider uncertainty in supply; in other words, what happens when a firm's suppliers, or the firm's own facilities, are unreliable. It discusses the risk‐diversification effect, a supply‐uncertainty version of the risk‐pooling effect. The chapter also discusses models for setting inventory levels in the presence of...
Chapter
This chapter considers a setting similar to the economic order quantity (EOQ) model but with stochastic demand. The mean demand per year is λ. The inventory position is monitored continuously, and orders may be placed at any time. The chapter focuses on the case in which the demands have a continuous distribution. It discusses an exact model for th...
Chapter
Auctions have been around for centuries and the mathematical analysis of auctions dates back decades. Consumer auctions like eBay have become household names, but business‐to‐business auctions have grown even more quickly. In an English auction, there is a set of bidders, each bidding on a single item. In the combinatorial auction, the seller alloc...
Chapter
This chapter covers one important aspect of the transportation‐related decisions a firm must make, namely, routing vehicles among the locations they must visit. It discusses the famous traveling salesman problem (TSP). The TSP is perhaps the best‐known combinatorial optimization problem and has been intensely studied by researchers in supply chain...
Chapter
This chapter reviews inventory optimization models for multiechelon systems with shipments made among the stages. Multiechelon networks can be structured in a number of ways, and the network's topology plays a role in determining how the system is analyzed and optimized. In an assembly system, each stage has at most one successor. Interpretation is...
Chapter
Supply chains are typically composed of multiple players, each with competing goals. This chapter introduces a few contract types that coordinate the newsvendor model, and reviews some important concepts from game theory. The literature on supply chain coordination draws heavily from game theory. The goal of supply chain coordination is to change t...
Chapter
This chapter begins by discussing a classical facility location model, the uncapacitated fixed‐charge location problem (UFLP). The UFLP and its descendants have been deployed more widely in supply chain management than perhaps any other location model. One reason for this is that the UFLP is very flexible and, although it is NP‐hard, lends itself t...
Preprint
Full-text available
This article explores the concepts of ocean wave multivariate multistep forecasting, reconstruction and feature selection. We introduce recurrent neural network frameworks, integrated with Bayesian hyperparameter optimization and Elastic Net methods. We consider both short- and long-term forecasts and reconstruction, for significant wave height and...
Preprint
Full-text available
Although reinforcement learning (RL) can provide reliable solutions in many settings, practitioners are often wary of the discrepancies between the RL solution and their status quo procedures. Therefore, they may be reluctant to adapt to the novel way of executing tasks proposed by RL. On the other hand, many real-world problems require relatively...
Chapter
Full-text available
We introduce a multistage stochastic programming model to optimize the distribution–production network of medical devices; in particular, artificial hip and knee joints for orthopedic surgery. These devices are distributed to hospitals in kits that contain multiple sizes of the joint; the surgeon uses one device from the kit and then returns the re...
Article
Communications networks play an important role in the operation and control of power grids. The integration of intermittent and stochastic renewable energy sources into the electricity system increases the criticality of these communications systems to maintain the reliability of the overall power network. Communication networks are employed to con...
Article
We consider a competitive facility location problem in which two firms engage in a leader-follower game. Both firms would like to maximize the customer demand that they capture. Given the other player's decision, each player's problem is the classical maximal covering location problem. That is, the leader has to solve a bi-level problem in which th...
Article
Full-text available
We present an end-to-end framework for solving Vehicle Routing Problem (VRP) using deep reinforcement learning. In this approach, we train a single model that finds near-optimal solutions for problem instances sampled from a given distribution, only by observing the reward signals and following feasibility rules. Our model represents a parameterize...
Article
Full-text available
Many retailers discriminate among their customers based on their value to the firm. Instead of losing a customer due to this discrimination or lack of inventory, a retailer might prefer to place a transshipment request with other retailers to satisfy the customer’s demand. The system as a whole can benefit from this type of transshipments. In this...
Article
Full-text available
In this paper, a new modeling approach is introduced for a competitive facility location problem in which multiple competitors aim to maximize their market shares. The problem is called the Competitive Maximal Covering Location Problem (CMCLP) based on the classical Maximal Covering Location Problem. Typically, the CMCLP is modeled as a Stackelberg...
Article
Full-text available
In multi-echelon inventory systems the performance of a given node is affected by events that occur at many other nodes and at many other time periods. For example, a supply disruption upstream will have an effect on downstream, customer-facing nodes several periods later as the disruption "cascades" through the system. There is very little researc...
Article
Full-text available
The beer game is a widely used in-class game that is played in supply chain management classes to demonstrate the bullwhip effect. The game is a decentralized, multi-agent, cooperative problem that can be modeled as a serial supply chain network in which agents cooperatively attempt to minimize the total cost of the network even though each agent c...
Article
When an unreliable supplier serves multiple retailers, the retailers may compete with each other by inflating their order quantities in order to obtain their desired allocation from the supplier, a behavior known as the rationing game. We introduce capacity information sharing and a capacity reservation mechanism in the rationing game and show that...
Article
When an unreliable supplier serves multiple retailers, the retailers may compete with each other by inflating their order quantities in order to obtain their desired allocation from the supplier, a behavior known as the rationing game. We introduce capacity information sharing and a capacity reservation mechanism in the rationing game and show that...
Article
Full-text available
The newsvendor problem is one of the most basic and widely applied inventory models. There are numerous extensions of this problem. One important extension is the multi-item newsvendor problem, in which the demand of each item may be correlated with that of other items. If the joint probability distribution of the demand is known, the problem can b...
Article
Full-text available
The newsvendor problem is one of the most basic and widely applied inventory models. There are numerous extensions of this problem. One important extension is the multi-item newsvendor problem, in which the demand of each item may be correlated with that of other items. If the joint probability distribution of the demand is known, the problem can b...
Article
We study inventory optimization for locally controlled, continuous-review distribution systems with stochastic customer demands. Each node follows a base-stock policy and a first-come, first-served allocation policy. We develop two heuristics, the recursive optimization (RO) heuristic and the decomposition-aggregation (DA) heuristic, to approximate...
Article
This paper considers the reliable capacitated logistics network design problem (RCLNDP) with system disruptions, which is concerned with locating facilities, constructing transportation links, and allocating their capacities to customers in order to satisfy the demand with minimum expected total cost. Both the facilities and the transportation link...
Article
We review the OR/MS literature on supply chain disruptions in order to take stock of the research to date and to provide an overview of the research questions that have been addressed. We first place disruptions in the context of other forms of supply uncertainty and discuss common modeling approaches. We then discuss nearly 150 scholarly works on...
Article
Two players sequentially locate a fixed number of facilities, competing to capture market share. Facilities face disruption risks, and each customer patronizes the nearest operational facility, regardless of who operates it. The problem therefore combines competitive location and location with disruptions. This combination has been absent from the...
Article
Renewable energy, such as wave energy, plays a significant role in sustainable energy development. Wave energy represents a large untapped source of energy worldwide and potentially offers a vast source of sustainable energy. We present models and a heuristic algorithm for choosing optimal locations of wave energy conversion (WEC) devices within an...
Article
This paper investigates a facility location model that considers the disruptions of facilities and the cost savings from the inventory risk-pooling effect and economies of scale. Facilities may have heterogeneous disruption probabilities. When a facility fails, its customers may be reassigned to other surviving ones to hedge against lost-sales cost...
Article
We present methods for optimizing generation and storage decisions in an electricity network with multiple unreliable generators, each colocated with one energy storage unit (e.g., battery), and multiple loads under power flow constraints. Our model chooses the amount of energy produced by each generator and the amount of energy stored in each batt...
Article
We introduce the reliable server assignment problem considering attacks, which seeks to choose the locations of servers on a network in order to maximize the network reliability that results from a worst-case attack on the edges of the network. The problem is formulated on an unreliable network such that edges are subject to fail independently, and...
Conference Paper
In order to obtain the maximum power absorption of wave power devices, the mean gain factor q for the array and its characteristics are discussed in this paper. Some characteristics about the maximum q are studied through theoretical derivation and numerical examples. Also, the relationship between the maximum q and the properties of the optimum li...
Article
Full-text available
The authors consider efficient mechanisms to optimize the power consumption within a home, industrial facility, college campus, or other facility or set of facilities. The system is controlled centrally by an energy management controller (EMC), which determines the timing of the operation of some of the devices within the facilities. The authors in...
Article
Full-text available
Demand-side energy management systems consist of communication links between consumer homes and a centralized scheduler, whose main responsibility is to make decisions regarding curtailment, shifting, or modification of individual loads so that the aggregate load profile closely matches a predetermined supply function for a given time horizon. One...
Article
We investigate optimal system design in a multi-location system in which supply is subject to disruptions. We examine the expected costs and cost variances of the system in both a centralized and a decentralized inventory system. We show that, when demand is deterministic and supply may be disrupted, using a decentralized inventory design reduces c...
Article
The combined facility location and network design problem is an important practical problem for locating public and private facilities. Moreover, incorporating aspects of reliability into the modeling of facility location problems is an effective way to hedge against disruptions in the system. In this paper, we consider a combined facility location...
Chapter
Most of the early research in inventory theory concentrates purely on demand uncertainty. However, models which aim to capture the dynamics of real-world systems must also take uncertainties in the supply side into consideration. One type of supply uncertainty that has attracted considerable attention during the past decade is supply disruptions, s...
Article
Full-text available
We derive an analytic solution for the wave energy converter (WEC) layout problem with N = 2 devices, assuming regular (sinusoidal) incident waves, under the point-absorber approximation.
Article
Many retailers discriminate among their customers based on their value to the firm. Instead of losing a customer due to this discrimination or lack of inventory, a retailer might prefer to request that other retailers satisfy the customer's demand. The system as a whole can benefit from this types of transshipments. In this paper, we study a multi-...
Article
We present a robust optimization model for production planning under electricity supply that is subject to uncertain interruptions caused by participation in interruptible load contracts (ILCs). The objective is to minimize the cost of electricity used for production while providing a robust production plan which ensures demand satisfaction under a...
Article
Full-text available
In this paper, a communication-based load scheduling protocol is proposed for in-home appliances connected over a home area network. Specifically, a joint access and scheduling approach for appliances is developed to enable in-home appliances to coordinate power usage so that the total energy demand for the home is kept below a target value. The pr...
Article
We study two-echelon distribution systems (also known as one-warehouse, multiple-retailer (OWMR) systems) subject to supply disruptions. We propose algorithms to find the optimal or near-optimal stocking levels of all the locations in the system by assuming periodic review base-stock policies, deterministic demands at the retailers and non-overlapp...
Article
We study inventory optimization for continuous-review distribution systems with Poisson customer demands under a first-come, first-served allocation policy. We develop two heuristics, the recursive optimization (RO) heuristic and the decomposition-aggregation (DA) heuristic, to approximate the base-stock levels of all the locations in the system. T...
Conference Paper
In this paper, we conduct performance analysis for a joint media access and appliance scheduling protocol devised for efficient information-management in smart appliances within a home-area network. This protocol enables appliances in-home to coordinate power usage so that total demand for the home is kept below a target value. In particular, from...
Article
We investigate optimal system design in a multi-location system in which supply is subject to disruptions. We examine the expected costs and cost variances of the system in both a centralized and a decentralized inventory system. We show that, when demand is deterministic and supply may be disrupted, using a decentralized inventory design reduces c...
Chapter
Full-text available
Disruptions in supply chains occur routinely—both large ones, due to natural disasters, labor strikes, or terrorist attacks, and small ones, due to machine breakdowns, supplier stockouts, or quality problems (to name a few examples). Companies whose supply processes are affected by disruptions may experience delays in transportation and dysfunction...
Article
This paper studies a strategic supply chain management problem to design reliable networks that perform as well as possible under normal conditions, while also performing relatively well when disruptions strike. We present a mixed-integer programming model whose objective is to minimize the nominal cost (the cost when no disruptions occur) while re...
Conference Paper
Full-text available
This paper proposes a Real-Time Pricing (RTP)-based power scheduling scheme as demand response for residential power usage. In this scheme, the Energy Management Controller (EMC) in each home and the service provider form a Stackelberg game, in which the EMC who schedules appliances' operation plays the follower level game, and the provider who set...
Chapter
This article provides a broad overview of facility location problems, one of the oldest and most widely studied fields of applied optimization. The article presents a standard taxonomy of location models and discusses key dimensions along which they are classified. Mathematical programming formulations and common solution methods for several classi...
Chapter
The mail-order DVD rental company Netflix chooses distribution center locations so that most of its customers receive their DVDs within one business day via first-class U.S. Mail. Similarly, many municipalities aim to have fire crews reach 911 callers within a specified time, such as four minutes. Both of these are examples of the notion of coverag...
Article
a b s t r a c t This paper studies a strategic supply chain management problem to design reliable networks that perform as well as possible under normal conditions, while also performing relatively well when disruptions strike. We present a mixed-integer programming model whose objective is to minimize the nominal cost (the cost when no disruptions...
Article
We consider a firm facing supply chain risk in two forms: disruptions and yield uncertainty. We demonstrate the importance of analyzing a sufficiently long time horizon when modeling inventory systems subject to supply disruptions. Several previous papers have used single-period newsboy-style models to study supply disruptions, and we show that suc...