In this dissertation, we study inventory and revenue management problems for perishable products with customer choice considerations. This dissertation is composed of six chapters. In Chapter 1, we provide an overview and the motivation of problems. Subsequently, in Chapter 2, we propose a joint inventory and pricing problem for a perishable product with two freshness levels. After a stochastic time, a fresh item turns into a non-fresh item, which will expire after another random duration. Under an (r, Q) ordering policy and a markdown pricing strategy for non-fresh items, we formulate a model that maximizes the long-run average profit rate. We then reduce the model to a mixed-integer bilinear program (MIBLP), which can be solved efficiently by state-of-the-art commercial solvers. We also investigate the value of using a markdown strategy by establishing bounds on it under limiting regimes of some parameters such as large market demand. Further, we consider an Economic Order Quantity (EOQ)-type heuristic and bound the optimality gap asymptotically. Our results reveal that although the clearance strategy is always beneficial for the retailer, it may hurt customers who are willing to buy fresh products. In Chapter 3, we extend this model to the dynamic setting with multiple freshness levels of perishable products. Due to the complexity of the problem, we study the structural properties of value function and characterize the structure of the optimal policies by using the concept of anti-multimodularity. The structural analysis enables us to devise three novel and efficient heuristic policies. We further extend the model by considering donation policy and replenishment system. Our results imply that freshness-dependent pricing and dynamic pricing are two substitute strategies, while freshness-dependent pricing and donation strategy are two complement strategies for matching supply with demand. Also, high variability in product quality under dynamic pricing benefits the firm, but it may result in significant losses with a static pricing strategy. In Chapter 4, we study a joint inventory-pricing model for perishable items with fixed shelf lives to examine the effectiveness of different markdown policies, including single-stage, multiple-stage, and dynamic markdown policies both theoretically and numerically. We show that the value of multiple-stage markdown policies over single-stage ones asymptotically vanishes as the shelf life, market demand, or customers’ maximum willingness-to-pay increase. In chapter 5, with a focus on blood products, we optimize blood supply chain structure along with the operations optimization. Specifically, we study collection, production, replenishment, issuing, inventory, wastage, and substitution decisions under three different blood supply chain channel structures, i.e., the decentralized, centralized, and coordinated. We propose a bi-level optimization program to model the decentralized system and use the Karush–Kuhn–Tucker (KKT) optimality conditions to solve that. Although centralized systems result in a higher performance than decentralized systems, it is challenging to implement them. Thus, we design a novel coordination mechanism to motivate hospitals to operate in a centralized system. We also extend the model to the case with demand uncertainty and compare different issuing and replenishment policies. Analysis of a realistic case-study indicates that integration can significantly improve the performance of the system. Finally, Chapter 6 concludes this dissertation and proposes future research directions. / Dissertation / Doctor of Philosophy (PhD)

This paper studies the problem of multi-period pricing for perishable products in a competitive (oligopolistic) market. We study non cooperative Nash equilibrium policies for sellers. At the beginning of the time horizon, the total inventories are given and additional production is not an available option. The analysis for periodic production-review models, where production decisions can be made at the end of each period at some production cost after incurring holding or backorder costs, does not extend to this model. Using results from game theory and variational inequalities we study the existence and uniqueness of equilibrium policies. We also study convergence results for an algorithm that computes the equilibrium policies. The model in this paper can be used in a number of application areas including the airline, service and retail industries. We illustrate our results through some numerical examples. / Singapore-MIT Alliance (SMA)

The focuses of this dissertation are problems of batch production scheduling problems for perishable products with setup times, with the main applications in answering production planning problems faced by manufacturers of perishable products, such as beers, vaccines and yoghurts. The benefits of effective production plans can help companies reduce their total costs substantially to gain the competitive advantages without reduction of the service level in a globalize economy. We develop concepts and methodologies that are applied in two fundamental problems: (i) the batch production scheduling problem for perishable products with sequence-independent setup times (BPP-SI) and (ii) the batch production scheduling problem for perishable products with sequence-dependent setup times (BPP-SD). The problem is that given a set of forecast demand for perishables products to be produced by a set of parallel machines in the single stage of batch production, with each product having fixed shelf-life times and each machine requiring setup times before producing a batch of product, find the master production schedule which minimizes total cost over a specified time horizon. We present the new models for both problems by formulating them as a Mixed Integer Program (MIP) on the discrete time. Computational studies in BPP-SI and BPP-SD for industrial problems are presented. In order to efficiently solve the large BPP-SI problems in practice, we develop the five efficient heuristics. The extensive computational results show that the developed heuristics can obtain the good solution for the very large problem size and require very short amount of computational time.

[pt] Esta dissertação analisa o problema da gestão de estoque de sanduíches de uma empresa prestadora de serviços de alimentação, a Tok Take Alimentação Ltda. Para tanto, foi feito um levantamento bibliográfico na área de gestão de estoques e de previsão de demanda. Para o estudo de caso, dados históricos do consumo diário de sanduíches em um determinado cliente foram coletados e submetidos à análise por meio de dois métodos de previsão de demanda: o método de médias móveis dupla e o método de amortecimento direto para dados sazonais. Desta forma, foram determinados dois modelos que possibilitam a previsão de demanda diária deste produto. / [en] This report analyzes the issue of managing the inventory of sandwiches of a food vending enterprise, Tok Take Alimentação Ltda. For that purpose, a bibliographic survey was made on inventory management and demand forecasting. In the case studied it was found that no gain could be obtained by expanding the replenishment period. Hence the analysis turned its focus to demand forcasting. For the case study, historical data of sandwich consumption at a specific client site were colected and submited to analysis by means of two forecasting methods namely: double moving average and direct smoothing for seasonal data. After that, a model that enables daily forecasting of that product`s demand was determined.

No description available.

Ce travail porte sur la modélisation et la résolution de problèmes d’optimisation robuste et multi-objectifs du transport multimodal. Après une synthèse des travaux de la littérature et des concepts de base de l’optimisation robuste et l’optimisation multi-objectif, nous proposons un nouveau modèle d’optimisation multi-objectif du transport multimodal des produits agricoles marocains vers des clients européens. L’objectif est de déterminer la meilleure stratégie d’exportation qui minimise simultanément le coût total de transport multimodal et l’overtime maximal en prenant en considération des contraintes réalistes. Nous proposons également des nouvelles approches de résolution avec une application sur un réseau de transport multimodal réel.Nous avons étudié une autre problématique du transport multimodal avec localisation de terminaux intermodaux. Outre la version déterministe, une optimisation robuste qui tient compte des incertitudes sur les capacités, les coûts d’utilisation et les coûts de transport. Deux approches hybrides ont été proposées pour la résolution du problème.Dans ces contributions, des modèles et des méthodes sont présentés, des remarques et des interprétations sont tirées à propos de l’impact de la périssabilité des produits et de la robustesse sur les flux, le choix des ports, des trajets et des modes de transport. / Because of the importance of multimodal transport for goods importation and exportation from Morocco to international customers, our goals are modeling and solving multimodal freight transportation problems by more focusing on some issues confronted by our country. After presenting the required mathematical background on robust and multiobjective optimization and surveying the literature works on multimodal transport problems, its variants and solution approaches; and instead of testing them only on traditional benchmarks; we dealt with new variants and methods. A multi-objective mathematical model is proposed to optimize the multimodal transport of agricultural products from Morocco to Europe. To solve this model adapted to a real network, two multiobjective version algorithms are presented in order to optimize simultaneously the total transportation cost and the over-time.Given the complexity of the global logistics chain by various operations and several stakeholders, the data of the problem may sometimes be ignored or uncompleted. That’s why we have developed a mathematical model for multimodal terminal location problem by integrating uncertainties of the transportation costs, the capacities and the using costs of terminals. A population based simulated annealing and a hybrid method combining an exact and a metaheuristic approaches are proposed to effectively solving the problem. The test is then performed on a real intermodal network. These contributions are concluded by remarks and highlights about the impact of perishability and robustness on flows, location strategies of ports, the choice of paths and transportation modes.

Pour accompagner le développement des fermes urbaines professionnelles et des circuits courts et de proximité dans les grandes métropoles, nous proposons des outils à base de programmes mathématiques d'aide à la conception de fermes maraîchères diversifiées ciblant les demandes de différents types de clients en fruits et légumes frais locaux. Les solutions techniques de culture en ville se développent rapidement, mais compte-tenu des contraintes fortes de la production agricole urbaine (foncier limité, coûts opérationnels élevés), la définition de modèles économiques viables pour des fermes pérennes est un vrai défi pour les maraîchers urbains. Trois modèles en programmation linéaire mixte sont présentés et confrontés aux résultats du terrain : un modèle de dimensionnement stratégique annuel, un modèle de sélection de la meilleure combinaison de clients et un modèle de dimensionnement stratégique pluri-annuel des fermes maraîchères. Des résultats numériques et les performances des modèles sont présentés à partir de cas concrets multi-produits, multi-techniques et multi-périodes. Nos contributions résident dans la prise en compte de la périssabilité des produits frais dans le dimensionnement stratégique des systèmes de production, incluant le dimensionnement de la main d’œuvre agricole. / To support the urban farm emergence trend in large metropolises, we propose decision support tools based on mathematical programs to design market gardening farms targetting the demands of different categories of clients in local fresh fruits and vegetables. Technical solutions develop rapdily, but the strong constraints linked to urban farming, such as limited surface and high operating costs, make difficult to define viable and sustainable business models for urban market gardeners. Three mixed integer linear programming models are presented: An annual strategic sizing model, a client combination selection model and a plurennial strategic sizing model for diversified fruit and vegetable farms. Numerical results and model performances are presented, based on multi-products, multi-techniques and multi-periods real cases. Our main contributions are the consideration of the perishable nature of fruits and vegetables in strategic production systems sizing models, including notably the investments and workforce sizing.

Thesis (MPA (School of Public Management and Planning))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Public sector reform has been around since the 1980s and was a result of criticism against traditional public administration for being too slow and inefficient to address public needs. Although Public sector reform is common in developed countries, evidence of public sector reform has rarely been seen in developing countries. The purpose of this investigation is to determine whether there is any evidence of public sector reform in a developing country such as South Africa. The author divides public sector reform into three categories, namely: new governance, regulatory governance and new public management (NPM). Based on the theoretical information analysed, a list of qualifying criteria for public sector reform is compiled. The author then focuses on the Perishable Products Export Control Board (PPECB), a statutory organisation acting as a service provider for the perishable products export industry and a regulator on behalf of the South African government. The author analyses the model on which South African perishable exports are based and studies the organisation‟s history, strategies, operational structure and its relationship with government. The information gathered is then compared to the list of qualifying criteria compiled for public sector reform. It was found that the model, and specifically service delivery strategies by the PPECB, provides conclusive evidence of new governance, regulatory governance and NPM. It was also found the model is a hybrid between traditional public administration and public sector reform, as it contains characteristics of both. The study takes the form of a literature review. Research was conducted through studying various literatures pertaining to new governance, regulatory governance and new public management. In addition, the author gathered relevant information from within the PPECB, the South African Department of Agriculture, Forestry and Fisheries (DAFF) and the export industry. Further information was also collected by means of unstructured interviews with senior individuals employed by the PPECB. / AFRIKAANSE OPSOMMING: Openbare hervorming bestaan sedert die jare tagtig en het basies ontstaan as gevolg van kritiek omdat tradisionele openbare administrasie te traag en onbevoeg was om openbare behoeftes aan te spreek. Hoewel openbare hervorming in ontwikkelde lande stewig gevestig is, is daar ook bewys daarvan in ontwikkelende lande. Die doel van hierdie ondersoek was om vas te stel of daar enige bewys van openbare hervorming in ‟n ontwikkelende land soos Suid-Afrika bestaan. Die outeur het openbare hervorming in drie kategorieë verdeel, te wete nuwe regeringsbestuur, regulatoriese regeringsbestuur en nuwe openbare bestuur. Op grond van ‟n analise van die teoretiese inligting, is ‟n lys van kwalifiserende kriteria – gerig op openbare hervorming – saamgestel. Die outeur het vervolgens op die Bederfbare Produkte Uitvoerbeheerraad (PPECB) gefokus – dit is ‟n statutêre liggaam wat as diensverskaffer vir die bederfbare produkte uitvoernywerheid en as ‟n reguleerder namens die Suid-Afrikaanse regering optree. Die outeur het ‟n analise gedoen van die model waarop Suid-Afrikaanse bederfbare uitvoere gebaseer is en voorts die organisasie se geskiedenis, strategie, operasionele struktuur en sy verhouding met die regering bestudeer. Die inligting wat ingewin is, is vervolgens met die lys van kwalifiserende kriteria – gerig op openbare hervorming – vergelyk. Daar is bevind dat die model – en spesifiek diensleweringstrategie by die PPECB – voldoende bewys lewer van nuwe regeringsbestuur, regulatoriese regeringsbestuur en nuwe openbare bestuur. Daar is ook bevind dat die model ‟n hibridisering is tussen tradisionele openbare administrasie en openbare hervorming aangesien dit karaktereienskappe van albei bevat. Die studie is in die vorm van ‟n literêre oorsig gedoen. Navorsing is uitgevoer deur die bestudering van verskeie geskrifte oor nuwe regeringsbestuur, regulatoriese regeringsbestuur en nuwe openbare bestuur. Daarbenewens het die outeur relevante inligting binne die PPECB, die Suid-Afrikaanse Departement van Landbou, Bosbou en Visserye en die uitvoernywerheid, ingesamel. Nog inligting is ook bekom deur ongestruktureerde onderhoude met senior werknemers van die PPECB te voer.