Peter C. Bell

Visual interactive simulation - history, recent developments, and major issues

Visual Interactive Simulation (VIS) has dominated discrete-event simulation in the United Kingdom throughout the eighties. Con ceived and initially implemented by Hurrion (1976), who also coined the phrase, VIS first gained widespread exposure through the package SEE-WHY The ideas behind VIS are fundamentally different from what is referred to in the United States as anima tion, since the prime motivator is user interaction with the run ning simulation, rather than just portrayal of the simulation. After presenting a short history of VIS, we will discuss some of the research and development that has been undertaken in the United Kingdom and North America. Following presentation of an example, the state of VIS and a number of generally accepted guidelines for doing VIS are discussed. A number of recent developments, many of them also relevant to animation, and four major issues in the research and prac tice of VIS are presen ted.

Coordinating a decentralized supply chain with customer returns and price-dependent stochastic demand using a buyback policy

We investigate a decentralized supply chain that consists of a manufacturer and a retailer where the retailer simultaneously determines the retail price and order quantity while experiencing customer returns and price dependent stochastic demand. We propose an agreement between the manufacturer and the retailer that includes two buyback prices, one for unsold inventory and a second for customer returns, and show that this type of easy-to-implement agreement can achieve perfect supply chain coordination and be a win-win for both manufacturer and retailer when a complementary profit-sharing agreement is included.

The impact of customer returns on pricing and order decisions

In this paper, we address the simultaneous determination of price and inventory replenishment when customers return product to the firm. We examine cases when the quantity of returned product is a function of both the quantity sold and the price, in single and multi-period problems, with and without uncertainty in demand. We derive results for optimal prices and order quantities and discuss how the firm should change price and inventory quantities in order to mitigate the negative effects of returns from customers.

Visual interactive modelling: The past, the present, and the prospects

Abstract This article presents the conceptual foundations of visual interactive modelling (VIM), and reviews important recent developments in VIM and its application areas. Finally, the prospects for VIM are assessed, together with five areas where there opportunities for operational researchers to continue to play a significant role in the future of VIM.

The effect of market segmentation with demand leakage between market segments on a firm’s price and inventory decisions

Abstract In this paper, we address the simultaneous determination of price and inventory replenishment in a newsvendor setting when the firm faces demand from two or more market segments in which the firm can set different prices. We allow for demand leakage from higher-priced segments to lower-priced segments and assume that unsatisfied demand can be backlogged. We examine the case where the demands occur concurrently without priority and are met from a single inventory. We consider customer’s buy-down behavior explicitly by modeling demand leakage as a function of segment price differentiation, and characterize the structure of optimal inventory and pricing policies.

A visual interactive decision support system for workforce (nurse) scheduling

This paper describes a microcoraputer based visual interactive decision support system for workforce scheduling. A prototype system was first constructed and then tested on a nurse scheduling probl...

Optimal fences and joint price and inventory decisions in distinct markets with demand leakage

This paper evaluates the simultaneous determination of price and inventory replenishment when a firm faces demand from distinct market segments. A firm utilizes fences, such as advance or nonrefundable payment, to maintain separation of its market segments; however, fences are imperfect and allow a degree of demand leakage from the higher-priced to the lower-priced market segment. We investigate the optimal structure of joint price and inventory decisions with fencing, and demonstrate that more segments is not necessarily better, especially when demand uncertainty is high in the presence of lost sales. We also show the impact of imperfect fences on the firms profitability, and evaluate how fencing costs affect the optimal fencing decision.

The impact of customer returns on decisions in a newsvendor problem with and without buyback policies

In this paper, we examine how customer returns influence the retailers ordering decision, the manufacturers wholesale price decision, and the profits of the manufacturer and the retailer, in a single-period, stochastic demand (newsvendor) setting. When the manufacturer is a Stackelberg leader and the retailer is the follower, we also examine how to contract a buyback policy, where the manufacturer buys back both unsold inventory and customer-returned products, so that both the manufacturer and the retailer are more profitable than if they operate independently. We also show how this work can be generalized to the case of multiple retailers.

Simulation modelling: A comparison of visual interactive and traditional approaches

Abstract Visual interactive simulation (VIS) is now an established operational research (OR) technique. While many successful applications of VIS have been reported in the literature, little has been published regarding an appropriate methodology for building a VIS model or of the differences between tackling a problem using VIS as opposed to traditional batch simulation modelling using a simulation language. This article describes the development of a VIS model for a problem where a batch simulation model already existed. An attempt is made to compare VIS modelling with batch simulation modelling with respect to both the modelling process and the resulting model. The usefulness of having an existing simulation model to work from in building a VIS model is also investigated.

Teaching objectives: the value of using cases in teaching operational research

This paper describes our experience with a case study that was intended to provide business students with a straightforward exercise in operational research/management science (OR/MS) but which consistently produces a learning experience for students that is quite different from that envisaged when the case was originally written. An effort is made to explain the surprising results in the classroom. This example demonstrates the fact that building OR/MS models often reveals important dimensions of a problem that otherwise might remain unexplored. The richness of this case also demonstrates the value of exposing OR/MS students to real problems through the use of cases.