Temporary price reductions (sales) as a means of promotion have become an increasingly important tool in the marketing mix of food retailers around the world. This paper investigates the retailers' pricing strategy by explicitly accounting for the multi-product nature of retailing. We find that retailers systematically adjust the breadth and depth of sales over time and they respond aggressively to their rivals' promotional activities. Finally, the breadth and depth of sales are found to be substitutes in the set of the available strategies to increase the store traffic. (authors' abstract)

This dissertation builds on earlier works by analyzing the provision of product quality by a monopolist and comparing that to a social planner. This paper extends the analysis of this problem to the discrete quality setting. Earlier works focused on a continuum of qualities and found no quality distortion for the highest qualities, but downward quality distortion for lower qualities. The results in the discrete setting differ in that there can be an upward distortion of qualities provided by the monopolist for the highest qualities. The key to this distortion is that the monopolist focuses on the profit that can be extracted from the group of consumers that value quality the most. When there are neither too many nor only a few of these consumers relative to other market segments, it can lead the monopolist to bias its quality provision to extract more value from the these consumers. This effect distorts quality at the high-end as compared to the social planner. This upward distortion of quality is found in the real world. In Texas, 30.6% of cable service providers offers an upward distorted service for higher taste consumers. Besides the quality issue, I also examine how consumer distributions affect price, profit, and social welfare. Under the various hypothetical consumer distributions, I simulate the above values, and I observe the effect of distribution changes. When I apply this tool to the real data from Texas cable service industry, I can simulate the consumer type distribution in each franchise, and I can construct the demand curve. Finding consumer type distribution is the key for the demand estimation in this structure.

<p> The work in this thesis focuses on the temperature control of a semi-batch polymerization reactor. The system is published by Chylla and Haase (1993) as an Industrial Challenge and is typical of reactors at S.C. Johnson Wax. The challenge is to find a single controller that can adequately regulate reactor temperature despite changing process conditions. The multi-product nature of the system makes it a particularly interesting problem. Several different controllers are implemented and evaluated in this thesis. The controllers are in part chosen to quantify the amount process information (large or small) required in a controller structure in order to achieve satisfactory control. Two of the most promising controllers are a PID with feedforward compensation and a Nonlinear Adaptive algorithm. It is found that in many cases, there may be little incentive to go to a complex model based controller as the simpler feedback algorithm provides adequate control. However, the nonlinear adaptive controller is more easily extended to multi-batch or multi-product situations because of its more general nature. The PID with feedforward compensation requires retuning for each new situation in order to maintain satisfactory control. </p> / Thesis / Master of Engineering (MEngr)

Thesis (PhD (Agric))--Stellenbosch University, 2013. / ENGLISH ABSTRACT: It is common practice in computable general equilibrium (CGE) models that the output composition of multi-product industries remains constant despite changes in relative prices of products. The results of any scenario will show that products produced by a single industry will still be produced in the same ratio to each other as reflected by the base data. The objective of the study was to develop a CGE model for South Africa in which this assumption of fixed composition of output can be selectively relaxed. In order to allow industries to adjust their output composition in response to changes in relative prices of products a Constant Elasticity of Transformation (CET) function and the related first order condition were incorporated into an existing CGE model. This alternative specification of an output transformation function in the model enables the modeller to allow selected multi-product industries to increase production of products that show greater price increases relative to other products. The first order condition of the CET function determines the optimal combination of products for each industry. With the inclusion of the CET function there is a trade-off between theoretical rigour of the model and realism of the results, therefore an assumption of input-output separability was introduced as a way of recognising that the inclusion of a CET function violates the assumption that prices in the same row of a social accounting matrix (SAM) are equivalent. The model was calibrated with a SAM for South Africa for 2007 that was developed for purposes of this study. Set controls were included in the model to generalise the model in order that it can be calibrated with data from other countries as well. The SAM for South Africa contains provincial level information in the accounts for agriculture, labour and households. The agricultural industries are defined by geographical area, hence these industries are particularly good examples of multi-product industries that respond to relative price changes when determining production levels of individual products. The adjusted CGE model was used to analyse four scenarios focusing on selected issues mentioned in the National Development Plan for South Africa released by the National Planning Commission in 2011. The scenarios relate to increases in fruit exports as a result of global positioning, technical efficiency improvements for the agricultural sector through continued research and development, factor productivity growth in government and selected services sectors resulting from fighting corruption and curbing strikes, and augmenting the supply of skilled labour through an improvement in the quality of education. The results of the adjusted model show the desired effect: producers produce relatively more of the products for which they can get a relatively higher price and vice versa. This holds true regardless of whether the level of industry output increases or decreases. The impact of the model adjustment and the effects of changes in the levels of elasticities and choice of variables to close the model were analysed as part of the sensitivity analyses. The impact of changes in the functional form, elasticities and model closures on results, are different for each scenario. / AFRIKAANSE OPSOMMING: Dit is erkende praktyk in berekenbare algemene ewewigsmodelle dat die verhoudings waarin produkte tot mekaar geproduseer word deur multi-produk industrieë konstant gehou word, ongeag veranderings in relatiewe pryse van produkte. Die resultate van enige senario sal dus aandui dat die produkte wat deur 'n enkele industrie geproduseer word steeds in dieselfde verhouding tot mekaar geproduseer sal word, soos weerspieël in die basis data. Die doel van die studie was om 'n berekenbare algemene ewewigsmodel vir Suid-Afrika te ontwikkel wat die aanname dat die samestelling van elke industrie se uitset onveranderbaar is, selektief kan verslap. Om toe te laat dat industrieë die samestelling van uitset kan aanpas namate die relatiewe pryse van produkte verander, is 'n Konstante Elastisiteit van Transformasie funksie en die gepaardgaande eerste orde voorwaarde in 'n bestaande berekenbare algemene ewewigsmodel ingesluit. Die eerste orde voorwaarde bepaal die optimale verhoudings waarin produkte geproduseer moet word. Met die insluiting van die Konstante Elastisiteit van Transformasie funksie word teoretiese korrektheid van die model ingeboet in ruil vir meer realistiese resultate, dus is die aanname van inset-uitset onafhanklikheid gemaak en daardeur word ook erken dat as gevolg van die insluiting van die Konstante Elastisiteit van Transformasie funksie word daar nie meer voldoen aan die aanname data alle pryse in dieselfde ry van die sosiale rekeninge matriks (SRM) aan mekaar gelyk is nie. Die model is gekalibreer met 'n SRM vir Suid-Afrika vir 2007 wat vir doeleindes van die studie ontwikkel is. Deur die insluiting van kontroles vir versamelings is die model veralgemeen sodat die model ook met data van ander lande gekalibreer kan word. Die SRM vir Suid-Afrika se rekeninge vir landbou, arbeid en huishoudings bevat inligting op provinsiale vlak. Die landbou industrieë is volgens geografiese gebiede afgebaken en is dus besonder goeie voorbeelde van multi-produk industrieë wat reageer op relatiewe prys veranderings wanneer die produksievlakke van afsonderlike produkte bepaal word. Die aangepaste algemene ewewigsmodel is gebruik om vier senarios te ondersoek wat fokus op geselekteerde onderwerpe vervat in die Nasionale Ontwikkelingsplan wat deur die Nasionale Beplanningskommissie van Suid Afrika in 2011 vrygestel is. Die senarios hou verband met 'n styging in vrugte uitvoere as gevolg van globale posisionering, tegniese produktiwiteitsverhogings vir die landbousektor deur volgehoue navorsing en ontwikkeling, verhoging in die produktiwiteit van produksiefaktore van die regering en geselekteerde dienste sektore deur die aanspreek van korrupsie en vermindering in stakings, en die toename in geskoolde arbeid deur 'n verbetering in die kwaliteit van onderwys. Resultate van die aangepaste model toon die gewenste uitwerking: produsente produseer relatief meer van die produkte waarvoor hulle 'n relatiewe hoër prys kan kry, en omgekeerd. Dit geld ongeag of daar 'n verhoging of 'n verlaging in die vlak van die industrie se uitset is. Die impak van die modelaanpassing, die effek van veranderings in die vlakke van elastisiteite en die keuse van veranderlikes om die model te sluit, is geanaliseer as deel van die sensitiwiteitsanalises. Die impak van veranderings in die funksionele vorm, elastisiteite en modelsluiting op resultate, is verskillend vir elke senario.

We study simulation optimization methods for the stochastic economic lot scheduling problem. In contrast to prior research, we focus on methods that treat this problem as a black box. Based on a large-scale numerical study, we compare approximate dynamic programming with a global search for parameters of simple control policies. We propose two value function approximation schemes based on linear combinations of piecewise- constant functions as well as control policies that can be described by a small set of parameters. While approximate value iteration worked well for small problems with three products, it was clearly outperformed by the global policy search as soon as problem size increased. The most reliable choice in our study was a globally optimized fixed-cycle policy. An additional analysis of the response surface of model parameters on optimal average cost revealed that the cost effect of product diversity was negligible. (authors' abstract)

We consider the stochastic economic lot scheduling problem (SELSP) with lost sales and random demand, where switching between products is subject to sequence-dependent setup times. We propose a solution based on simulation optimization using an iterative two-step procedure which combines global policy search with local search heuristics for the traveling salesman sequencing subproblem. To optimize the production cycle, we compare two criteria: minimizing total setup times and evenly distributing setups to obtain a more regular production cycle. Based on a numerical study, we find that a policy with a balanced production cycle leads to lower cost than other policies with unbalanced cycles. (authors' abstract)

The blood supply chain, starting from the donor until the blood is used to meet transfusion demands of patients, is a multi-echelon and complex system. The perishable and lifesaving characteristics of blood products, such as red blood cells and platelets, as well as uncertainties in both supply and demand make it difficult to maintain a balance between shortage and wastage due to expiry. An effective blood supply chain should be able to meet the demand while at the same time reducing wastage and total operational cost. In order to be cost effective, the related organizations have to decide how much blood should be collected from donors, how much blood products should be produced at the blood center, and how much blood products should be distributed to hospitals or transshipped between hospitals. The objective of this dissertation is to provide these tactical and operational decisions to guide those who work in healthcare supply chain management and explore new opportunities on performance improvement for an integrated blood supply chain by optimization with aim of minimizing total cost, consideration of transshipment between hospitals, and application of a coordinated multi-product model. This dissertation presents three multi-stage stochastic models for an integrated blood supply chain to minimize total cost incurred in the collection, production, inventory, and distribution echelons under centralized control. The scope of this study focuses on modeling a supply chain of blood products in one regional blood center, several hospitals and blood collection facilities. First, we develop an integrated model for the platelet supply chain that accounts for demand uncertainty and blood age information, then we develop this model further by investigating the impact of transshipment between hospitals on cost savings, and then we propose a multi-product model that accounts for red blood cells and platelets at the same time and compare it with an uncoordinated model where the red blood cell and platelet supply chains are considered separately.

Au cours de la dernière décennie, le système de contrôle de production (PCS) Constant Work InProgress (CONWIP) a été étudié par un nombre croissant de publications. Compte tenu des défis industrielsactuels, tels que la nécessité de s’adapter, la personnalisation croissante des produits, la réduction des délaiset l’importance grandissante du service rendu aux clients, le ConWip semble être un PCS efficace et agilepour les industriels. Cette thèse débute par une revue systématique des travaux sur le ConWip remontant à2003 basée sur une méthode de classification originale. Cette méthode permet de catégoriser les papiers quise concentrent sur le dimensionnement, la performance, le contexte d’implémentation et la comparaison avecd'autres PCS. En plus de proposer une clé de lecture pour interpréter les approches de recherche, les critèresconsidérés répondent à des questions sur la façon de mettre en oeuvre, la façon d’optimiser et les raisonspour lesquelles utiliser le ConWip. Une étude sur les pistes de recherche proposées ou applicables au ConWipa ensuite permis de mettre en évidence les plus prometteuses et d’en extraire les principales tendances.L'objectif consiste ici à mettre à jour les lacunes de la recherche existante sur le ConWip. L'une d'entre ellesamène à des questions clés liées à la mise en oeuvre du ConWip dans un environnement caractérisé par unmix produit élevé et/ou par un mix gamme opératoire élevé. Dans ce contexte, quatre algorithmes qui génèrentdifférentes gammes génériques sont ensuite présentés. Ces gammes, appelées « gammes enveloppes » sontimplémentées dans Wipsim, un outil d'ingénierie utilisé dans les projets de conception et d'amélioration deslignes d'assemblage ConWip, qui permet de calculer les paramètres ConWip optimisés pour chacune desgammes. Un échantillon de données, dérivé d'un cas industriel, est utilisé pour tester les quatre algorithmes.Nous les comparons à travers leur sensibilité au mix produit et selon l'impact induit par l'introduction dedifférents produits atypiques dans le mix. Nos expériences montrent que nos algorithmes génèrent desgammes enveloppes pertinentes et aident les praticiens à choisir le plus adapté à leur contexte spécifique. / In the past decade, a growing body of literature has investigated the CONstant Work InProgress (ConWip) production control system (PCS). In view of the current industrial challengesentailing adaptability, product customisation, decreas- ing leadtimes and customer satisfaction, ConWipseems to be an effective and adaptive PCS for manufacturers. A ConWip systematic review datingback to 2003 and provides a guide for understanding through an original classification method. Thismethod enables the differentiation of papers that concentrate on Con- Wip sizing, performance andcontext as well as a comparison with other PCSs. In addition to providing a key to interpreting theresearch approaches, the criteria considered answers questions on how to implement, how to optimiseand why and when to use ConWip. The survey of research avenues proposed or applicable to CONWIPclassify them, highlight the most promising and extract the main trends. The final aim is to provide somegaps. One of the them deals with key questions related to the implementation of ConWip in a highproduct mix and/or high routing mix environment. Four algorithms that generate different genericroutings are presented. These routings are implemented into Wipsim, an engineering tool used inprojects to design and improve ConWip assembly lines, which allows the optimized ConWip parametersfor each routing to be calculated. A sample of data, derived from an industrial case, is used to test thefour models. We compare them via their sensitivity to the mix product and through the impact of theintroduction of different, atypical products. Our experiments show that our algorithms generatedworthwhile generic routings and help practitioners choose among them, depending on a specificcontext.

This study aims at exploring and developing an approach for user-centred product planning for product managers in multi-product tech companies. Applying the Design Thinking methodology in this research project allows for product managers to be involved in the design process as a whole. From research and interviews with product managers it can be seen that there is a global understanding of the importance of a shift in focus towards user experience rather than product features while planning, but that there are no clear means yet to facilitate this. Through co-design with product managers as well as individual prototyping, a lo-fi prototype of a planning tool is developed and tested. The results show that the prototype successfully facilitated multi-product planning and shifted the focus from features to experiences. The methodology used can be reproduced in analogous companies and the results can be used as a starting point to continue adapting and developing the approach. / Denna studie syftar till att utforska och utveckla ett tillvägagångssätt för användarcentrerad produktplanering för produktchefer inom tekniska produktutvecklingsbolag som utvecklar flera olika samverkande produkter. Metoden Design Thinking har använts i detta forskningsprojekt, vilket möjliggjort att produktchefer kunnat att vara involverade i designprocessen som helhet. Från initiala intervjuer med produktchefer framkom det att de förstod vikten av att ha fokus på användarupplevelse snarare än produktegenskaper under planering av flerproduktslösningar, men att de i dagsläget inte finns några tydliga verktyg för att underlätta detta. Genom samdesign med produktchefer formades ett antal prototyper av ett planeringsverktyg. En Lo-Fi-prototyp utvecklades och utvärderades av produktägare. Testerna visade att multiproduktplanering framgångsrikt underlättades och flyttade fokus från funktioner till användarupplevelser. Den metodik som använts här kan reproduceras i liknande företag och resultaten kan användas som utgångspunkt för att fortsätta anpassa och utveckla arbetssättet.

Despite recent advances in computer power and the development of better algorithms, theoretical scheduling methodologies developed for batch-chemical production are seldom applied in industry (Musier & Evans 1989 and Grossmann et al. 1992). Scheduling decisions may have significant impact on overall company profitability by defining how capital is utilized, the operating costs required, and the ability to meet due dates. The purpose of this research is to compare different production scheduling methods by applying them to a real-world multi-stage, multi-product, batch-chemical production line. This research addresses the problem that the theoretical algorithms are seldom applied in industry and allows for performance analysis of several theoretical algorithms. The research presented in this thesis focuses on the development and comparison of several scheduling algorithms. The two objectives of this research are to: 1. modify different heuristic production scheduling algorithms to minimize tardiness for a multi-product batch plant involving multiple processing stages with several out-of-phase parallel machines in each stage; and 2. compare the robustness and performance of these production schedules using a stochastic discrete event simulation of a real-world production line. The following three scheduling algorithms are compared: 1. a modified Musier and Evans scheduling algorithm (1989); 2. a modified Ku and Karimi Sequence Building Algorithm (1991); and 3. a greedy heuristic based on an earliest-due-date (EDD) policy. Musier and Evans' heuristic improvement method (1989) is applied to the three algorithms. The computation times to determine the total tardiness of each schedule are compared. Finally, all the schedules are tested for robustness and performance in a stochastic setting with the use of a discrete event simulation (DES) model. Mignon, Honkomp, and Reklaitis' evaluation techniques (1995) and Multiple Comparison of the Best are used to help determine the best algorithm. / Master of Science