Risk Management in Strategic Sourcing: An African Perspective

In this paper we survey existing literature from scholarly journals and practitioner literature published from 1980 to 2017 on the risks and mitigation factors of strategic sourcing in Africa and append the same with a detailed exemplar based on a large utility provider in South Africa.  The paper identifies the various supply chain risks facing organisations, contextualizing the same for Africa, and where applicable, the mitigation strategies thereof.  The preliminary finding was that there is generally an underrepresentation of Africa in supply chain management literature. Further, it was found that studies discussing supply chain risk and mitigation issues in Africa have focused mainly on challenges of sourcing in Africa.  A further observation was that literature provides some limited insights on how supply chain management tools such as total quality management, negotiation and supplier selection, and just-in time procurement may be implemented in African countries. However, the available literature manifests significant limitations in scope, both empirically and theoretically, when compared to the vast amount of contributions from emerging economies in Asia as well as developed economies. The study thus demonstrates that that there exists an untapped opportunity for future research in supply chain risk management in order to develop an integrated framework for risk management in strategic sourcing in Africa

Supply facility and input/output point locations in the presence of barriers

This paper studies a facility location model in which two-dimensional Euclidean space represents the layout of a shop floor. The demand is generated by fixed rectangular-shaped user sites and served by a single supply facility. It is assumed that (i) communication between the supply point and a demand facility occurs at an input/output (I/O) point on the demand facility itself, (ii) the facilities themselves pose barriers to travel and (iii) distance measurement is as per the L1-metric. The objective is to determine optimal locations of the supply facility as well as I/O points on the demand facilities, in order to minimize total transportation costs. Several, increasingly more complex, versions of the model are formulated and polynomial time algorithms are developed to find the optimal locations in each case. Scope and purpose In a facility layout setting, often a new central supply facility such as a parts supply center or tool crib needs to be located to serve the existing demand facilities (e.g., workstations or maintenance areas). The demand facilities are physical entities that occupy space, that cannot be traveled through, and that receive material from the central facility, through a perimeter I/O (input/output or drop-off/pick-up) point. This paper addresses the joint problem of locating the central facility and determining the I/O point on each demand facility to minimize the total material transportation cost. Different versions of this problem are considered. The solution methods draw from and extend results of location theory for a class of restricted location problems. For practitioners, simple results and polynomial time algorithms are developed for solving these facility (re) design problems

Competitive Location and Entry Deterrence in Hotelling's Duopoly Model

This paper analyzes the problem of two firms competing in a common linear market with demand distributed continuously over the market. The firms wish to maximize their respectíve profits by appropriate choice of number of facilities and their locations. Equilibrium location strategies are derived for uniform and symmetric triangular demand distributions. It is shown that pioneering advantage may help a firm overcome its cost disadvantage with respect to a competitor

Stock cutting to minimize cutting length

In this paper we investigate the following problem: Given two convex Pin and Pout, where Pin is completely contained in Pout, we wish to find a sequence of ‘guillotine cuts’ to cut out Pin, from Pout such that the total length of the cutting sequence is minimized. This problem has applications in stock cutting where a particular shape or design (in this case the polygon Pin) needs to be cut out of a given piece of parent material (the polygon Pout) using only guillotine cuts and where it is desired to minimize the cutting sequence length to improve the cutting time required per piece. We first prove some properties of the optimal solution to the problem and then give an approximation scheme for the problem that, given an error range &#x03B4, produces a cutting sequence whose total length is at most &#x03B4 more than that of the optimal cutting sequence. Then it is shown that this problem has optimal solutions that lie in the algebraic extension of the field that the input data belongs to — hence due to this algebraic nature of the problem, an approximation scheme is the best that can be achieved. Extensions of these results are also studied in the case where the polygons Pin and Pout are non-convex

Stock Cutting Of Complicated Designs by Computing Minimal Nested Polygons

This paper studies the following problem in stock cutting: when it is required to cut out complicated designs from parent material, it is cumbersome to cut out the exact design or shape, especially if the cutting process involves optimization. In such cases, it is desired that, as a first step, the machine cut out a relatively simpler approximation of the original design, in order to facilitate the optimization techniques that are then used to cut out the actua1 design. This paper studies this problem of approximating complicated designs or shapes. The problem is defined formally first and then it is shown that this problem is equivalent to the Minima1 Nested Polygon problem in geometry. Some properties of the problem are then shown and it is demonstrated that the problem is related to the Minimal Turns Path problem in geometry. With these results, an efficient approximate algorithm is obtained for the origina1 stock cutting problem. Numerica1 examples are provided to illustrate the working of the algorithm in different cases

Reverse Logistics Strategies and Their Implementations: A Pedagogical Survey

Reverse Logistics and the management of returned or used merchandise is a growing problem among manufacturers today. In this study we begin by presenting the nature and magnitude of the reverse logistics problem in the industry and a literature survey of the previous research in this area. Reverse Logistics deals with the processes associated with the reverse stream from users/owners to re-users. This paper provides content analysis of scientific literature on reverse logistics. Over thirty articles are included. In addition, we give an overview of particular issues, which we rink with strategies, practices and thus directions for future research

Buyer-Seller Quantity-Discount Strategies Under Profit Maximizing Objectives: A Game-Theoretical Analysis

This paper is intended to provide a detailed game-theoretical analysis of the buyer-vendor coordination problem embedded in the price-discount inventory model. Pure and mixed, cooperative and non-cooperative strategies are developed. Highlights of the paper include the full characterization of the Pareto optimal set, the determination of profit-sharing mechanisms for the cooperative case and the derivation of a set of parameter-specific non-cooperative mixed strategies. A numerical example is presented to illustrate the main features of the model

Budget Constrained Location Problem with Opening and Closing of Facilities

In this paper, we study a budget constrained location problem in which we simultaneously consider opening some new facilities and closing some existing facilities. Motivations for this problem stem from applications where, due to a change in the distribution of customer demand, the existing facility system no longer provides adequate service. The objective is to minimize the total weighted travel distance for customers subject to a constraint on the budget for opening and/or closing facilities and a constraint on the total number of open facilities desired. For this problem, we develop a mathematical programming model and examine its theoretical properties. We then develop three heuristic algorithms (greedy interchange, tabu search and Lagrangian relax-ation approximation) for this NP-hard problem. Computational testing of these algorithms includes an analysis of the sensitivity of the solution to the budget and the desired number of facilities. The intended application in this testing is that of locating/relocating bank branches in a large-size town such as in our data set from Amherst, New York. We also discuss the situation where operating costs are part of the objective function

Identifying Alternate Optimal Solutions to the Design Approximation Problem in Stock Cutting

The design approximation problem is a well known problem in stock cutting, where, in order to facilitate the optimization techniques used in the cutting process, it is required to approximate complex designs by simpler ones. Although there are algorithms available to solve this problem, they all suffer from an undesirable feature that they only produce one optimal solution to the problem, and do not identify the complete set of all optimal solutions. The focus of this paper is to study this hitherto unexplored aspect of the problem: specifically, the case is considered in which both the design and the parent material are convex shapes, and some essential properties of all optimal solutions to the design approximation problem are ascertained. These properties are then used to devise two efficient schemes to identify the set of all optimal solutions to the problem. Finally, the recovery of a desired optimal approximation from the identified sets of optimal solutions, is discussed

Art Gallery Problems for Convex Nested Polygons

In this article, we study a class of Art Gallery problems that are defined on a pair of convex nested polygons. Polynomial time algorithms are presented for all these problems, by reducing them to the Circle Covering problem, or by relating them to the Minimal Nested Polygon problem. Then it is shown that these problems can also be solved In polynomial time by formulating them as Integer Programs with the Circular Ones property. Finally the paper discusses how these algorithms can be efficiently implemented in parallel