Gunter P. Sharp

Order batching procedures

Abstract Computer simulation is used to compare two new procedures for batching orders in an order retrieval system against a baseline procedure. The factors considered are the travel metric, warehouse representation, item location assignments, number of items per order, and the total number of orders considered. The results indicate that the two new procedures, in combination with skewed (ABC) item location assignments can reduce batch tour lengths by up to 44%.

Forward-reserve allocation in a warehouse with unit-load replenishments

Many companies configure their warehouse with a forward area and a reserve area. The former is used for efficient order-picking, the latter for replenishing the forward area. We consider a situation in which orders are picked during a certain time period, referred to as the picking period. Prior to the picking period there is sufficient time to replenish the forward area. Our objective is to determine which replenishments minimize the expected amount of labor during the picking period. Further, we present a second model with a constraint on the replenishment activity. We model the problem as a binary programming problem and present efficient heuristics that provide tight performance guarantees. We compare the heuristics with procedures that are popular in practice and show that significant labor-savings are possible.

A Management Perspective on Risk of Security Threats to Information Systems

Electronic commerce and the Internet have enabled businesses to reduce costs, attain greater market reach, and develop closer partner and customer relationships. However, using the Internet has led to new risks and concerns. This paper provides a management perspective on the issues confronting CIO’s and IT managers: it outlines the current state of the art for security in e-commerce, the important issues confronting managers, security enforcement measure/techniques, and potential threats and attacks. It develops a scheme for probabilistic evaluation of the impact of security threats with some illustrative examples. This methodology may be used to assess the probability of success of attacks on information assets in organizations, and to evaluate the expected damages of these attacks. The paper also outlines some possible remedies, suggested controls and countermeasures. Finally, it proposes the development of cost models which quantify damages of these attacks and the effort of confronting these attacks. The construction of one such cost model for security risk assessment is also outlined. It helps decision makers to select the appropriate choice of countermeasure(s) to minimize damages/losses due to security incidents. Finally, some recommendations for future work are provided to improve the management of security in organizations on the whole.

Geometric Approaches to Solve the Chebyshev Traveling Salesman Problem

Abstract: Several heuristic procedures based on geometric concepts have been developed for the Chebyshev (or too) Traveling Salesman Problem (CTSP),which has numerous applications in materials handling and information storage-retrieval. The following study is concerned with evaluating the performance of geometric approaches as a function of the shape of the service region and the number of points to be sequenced. A new approach, the band insertion heuristic, is also introduced and compared with existing procedures. Trade-offs in tour quality and solution effort are the primary focus of the study, which is empirical in nature; however, the results generally apply to a wide range of configurations.

A structured procedure for analysis and design of order pick systems

We present a structured procedure for order pick system (OPS) analysis and design that has been established on literature review and interviews with and presentations to OPS experts. In particular, we attempt to include the thinking processes that occur between OPS designers and owners. The design procedure and related issues are discussed in the order of input, selection, and evaluation stages.

Quantitative and qualitative indices for the plant layout evaluation problem

In the past two decades, the researchers used to develop simulation models or mathematical programming models to estimate the performance measures of a production system which may or may not include the considerations of layout design, rather than develop indices specifically for evaluating a layout alternative. These models usually ask for very detailed information. Most of them involve oversimplifying assumptions and request overwhelming computational efforts such that they cannot be manipulated with ease in practice. The limitations and deficiencies of previous indices and performance measures include: parameters hard to obtain; inappropriate detailed data requirement; much effort to obtain little accuracy improvement; data available after operations start; no generic approach and no clear validation provided. To overcome these deficiencies, the generic approaches for developing quantitative and qualitative indices are provided and new indices for the flow criterion group and environment criterion group are presented. The parameters of each index are easier to obtain and do not require much effort on data collection. The validations of each quantitative index with examples are also provided. The generic approaches also allow the users to revise the indices according to the specific case considered.

Replacement under ongoing technological progress

This paper evaluates the cost savings achievable in the infinite horizon single-asset replacement problem by considering technological progress affecting assets available after multiple future replacements and allowing variable service lives. Using a simple geometric model to specify asset costs, constant service lives are shown to be suboptimal. It is shown by example that common replacement decision methods yield higher service lives for the first asset and substantially different discounted total costs for the series of assets. This effect is illustrated numerically using automobile cost data.

Application of the integrated framework for the plant layout evaluation problem

During the past two decades, there was not enough research effort spent to study the plant layout evaluation problem compared with that in the plant layout design problem. Only lengthy criterion sets with little structure were proposed for evaluation purpose. Very few quantitative indices were developed for measuring the impacts resulting from the criteria. In addition, there was no reasonable mechanism available to integrate the criteria and indices to obtain a score for each layout alternative. Therefore, an integrated framework for the plant layout evaluation problem is proposed to overcome these three drawbacks. This framework includes a structured criterion set having 18 criteria represented by a three-level hierarchical structure, the corresponding quantitative and qualitative indices for the criteria, and the integration methodology. This paper presents the integration methodology. Six essential issues in developing the integration methodology are discussed (i.e., user flexibility, method of weight assignment, normalization of index values, preceding direction of integration process, insensitivity to intermediate changes, data deficiency and information imbalance). The characteristics of criteria and indices are utilized to reduce the integration effort. For example, the efforts spent in pairwise comparisons of criteria and alternative-criterion comparisons usually seen in the Analytic Hierarchy Process (AHP) are greatly reduced. The application of the integrated framework to two industrial cases including an electronic equipment manufacturer and a home furnishing manufacturer demonstrates the applicability of the research results.

An empirical Evaluation of a General Purpose Automated Order Accumulation and Sortation System used in Batch Picking

Batch picking of orders can yield higher productivity in high volume situations, but necessarily requires subsequent accumulation and sortation. What is the relative performance of the various approaches ?

Example application of the cognitive design procedure for an order pick system: Case study☆

We present a numerical case study to illustrate a cognitive design procedure for an order pick system (OPS), which has been established through a series of interviews with and presentations to OPS experts and literature review. The design procedure and related issues are discussed in the order of input, selection, and evaluation stages along with iterative aspects of top-down decomposition and bottom-up modification. Included are managerial considerations; transaction data description; replenishment fulfillment; overall structure and detailed subsystem specification in reserve, picking, and sorting areas; and subsystem reconciliation and evaluation.