Baruch Keren

Trailer to door assignment in a synchronous cross-dock operation

With the advent of lean supply-chain management, cross-docking has become increasingly popular among shippers. Operating a cross-dock facility requires assigning receiving and shipping doors to trailers. The assignment determines the amount of freight handling within the cross-dock facility and therefore its efficiency. Due to the immense complexity of optimal formulations, dock-door assignment has been typically solved using heuristics. This paper discusses the existing approaches, and suggests a new optimal formulation, and a new heuristic approach for assigning cross-dock doors to trailers. In the process, the reader gains insight into several important issues related to dock door assignment.

MBTI Personality Types of Project Managers and Their Success: A Field Survey

This paper describes a survey of 280 project managers that reveals both their personality types (via Myers-Briggs personality inventory) and their success in project management. The results show that a project managers personality is better suited for functioning with partial data and under ambiguity than the rest of the population. These traits were found for both women and men. The conclusion is that project managers (females and males) have a unique personality-type distribution that distinguishes them from the general population. The findings can contribute to better understanding the traits that characterize the project management population, and their relationship to project success.

Hybrid methods for ranking DMUs that combine performance and improvement trend over successive periods

The paper proposes two methods that rank business units (e.g., ports, hubs and restaurants) not only by their performance functions values at certain points in time, but also by the derivatives of the performance functions, i.e., by trends. Two hybrid methods for fully ranking of decision making units (DMUs), where each DMU has multiple inputs and multiple outputs are proposed. The methods combine the performance and the improvement trend over successive periods into one index. The first method, DEA/AHP, is an extension of a known method and is based on two common methodologies – data envelopment analysis (DEA) and analytical hierarchical process (AHP). The second hybrid method DEA/Malmquist ranks DMUs by computing the average relative efficiency and the geometric mean of the Malmquist index. The applicability of the proposed methods is demonstrated for a real-life case study with ten fast-food hamburger restaurants.

Optimal timing of joint replacement using mathematical programming and stochastic programming models

The optimal timing for performing radical medical procedures as joint (e.g., hip) replacement must be seriously considered. In this paper we show that under deterministic assumptions the optimal timing for joint replacement is a solution of a mathematical programming problem, and under stochastic assumptions the optimal timing can be formulated as a stochastic programming problem. We formulate deterministic and stochastic models that can serve as decision support tools. The results show that the benefit from joint replacement surgery is heavily dependent on timing. Moreover, for a special case where the patients remaining life is normally distributed along with a normally distributed survival of the new joint, the expected benefit function from surgery is completely solved. This enables practitioners to draw the expected benefit graph, to find the optimal timing, to evaluate the benefit for each patient, to set priorities among patients and to decide if joint replacement should be performed and when.

ABC inventory classification via linear discriminant analysis and ranking methods

ABC inventory classification is one of the most frequently used approaches in inventory planning and control. Sorting of inventory items into group categories has traditionally been facilitated by means of their relative value. During recent years, a number of attempts have been made to classify items by several criteria simultaneously, but none of them use statistical tools to evaluate the classification quality. This paper proposes to use linear discriminant analysis (LDA) and data envelopment analysis (DEA) in the context of ABC inventory classification. A numerical case study illustrates the applicability of the procedure. This is, to the best of our knowledge, the first work that uses LDA for ABC inventory classification.

A multinomial model for the machine interference problem with different service types and multiple operators

This paper proposes a model for a special case of the machine interference problem (MIP), where each of N identical machines randomly requests several different service types. Each request for a service type is fulfilled by an operator who can provide only one service type. The model allows the calculation of the expected interference (waiting) time in the queue for each service type, according to the multinomial distribution. The uniqueness of the model is that under its assumptions internal service order and queue discipline are not needed for the interference calculations. The model requires as inputs only the machine runtime and the average time of each service type that is needed to produce one unit. These inputs can be obtained by a common work measurement. The model enables practitioners to determine the optimal numbers of operators that are needed for each service type in order to minimize the cost per unit or maximize the profit, or to set other performance measures. To demonstrate the applicability of the model, a theoretical analysis and a case study are presented.

A wage incentive plan for branch managers using the DEA methodology

Purpose – The purpose of this paper is to propose a wage incentive plan for branch managers of multi‐branch firms. The incentive payment is calculated according to each branchs performance and its relative rank, taking into consideration common variables, regional variables and managerial skill variables.Design/methodology/approach – The paper utilizes Andersen and Petersens super‐efficiency model, which is based on the model of Charnes, Cooper and Rhodes, the most widely used and best known data envelopment analysis model. The regional variables and the managerial skill variables are considered as inputs (resources). The periodic measured efficiencies are then translated into a special wage incentive plan with promotive and contrient interdependence between the branch managers.Findings – The regional variables and the managerial skill variables have a significant impact on the efficiency of each branch and on the ranking of the branches. These variables may increase or decrease the relative efficiency ...

The number of measurements to be performed for time study analysis

The setting of time standards by work measurement is costly and consumes much time and effort. Therefore, the aims are to minimise time measurements while guaranteeing that the measurements are sufficient to provide a required statistical precision. This paper presents two methods for determining the required number of cycles to be investigated in order to set time standards. The first method utilises the Pareto principle to compute the required number of cycles, taking into account the cumulative weight of the elements. The second method computes the number of measurements needed to ensure the required inaccuracy of the standard time of the entire cycle. The proposed methods compute the optimal number of measurements to be performed by also taking into account economic considerations. This is done by balancing the cost of performing extra measurements with the benefits achieved by reducing the inaccuracies in the final time standards. [Received 4 November 2011; Revised 2 February 2012; Revised 5 July 2012; Revised 10 October 2012; Accepted 10 October 2012]

Optimising project performance: the triangular trade-off optimisation approach

It is generally accepted that the three major dimensions of project success are time, budget, and quality. Most of the research in project planning is focused on the time-cost trade-off, and only a few papers have considered the three dimensions together. This paper describes the evolution of formulations for optimising project time-cost and quality, and continues by developing a new, non-linear optimisation formulation that better reflects the triangular trade-off structure between time, budget, and quality. In particular, the Cobb-Douglas formula is adopted and its use is illustrated. The model is discussed, and the structure of the trade-off is analysed and illustrated.

ABC Inventory Classification Using AHP and Ranking Methods via DEA

This paper presents methods for ABC inventory classification via the AHP (Analytical Hierarchical Process) and ranking methods via DEA (Data Envelopment Analysis) according to multi-criteria analysis. A numerical case study illustrates the proposed classification. Each ranking method may generate a different rank so it can be useful to use the AHP for setting weights for each ranking method and obtaining a final rank.