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.

[ES] Los productos perecederos representan un gran parte de los bienes que se comercializan en el mundo. Éstos productos empiezan a tener un papel más relevante dadas las condiciones de seguridad alimentaria que requiere la humanidad, en el año 2023 la población del planeta superó los 8 mil millones de habitantes, una cifra que presiona aún más el riesgo alimenticio del planeta. La gestión de éste tipo de cadenas de suministros es responsable en parte de la seguridad alimentaria de las personas, actualmente uno (1) de cada tres (3) kilos de comida que se producen en el mundo se pierde o desperdicia. Ésta situación merece un análisis más profundo, y por tanto se requiere dividir el problema en varias partes para saber la conexión del problema. Encontramos que el efecto látigo, un fenómeno que amplifica la demanda aguas arriba de la cadena de suministros, es responsable en cierto modo de ésta pérdida y desperdicio de alimento. Nuestra investigación encontró que existen varias causas que generan el efecto látigo, como la gestión de la demanda, el tiempo de entrega o de reabastecimiento, nivel de deterioro del producto, entre otros. Éstas causas del efecto látigo fueron simuladas en una cadena de 10 retailers, una central de abastos, tres intermediarios rurales y 6 agricultores; con el fin de evidenciar el impacto en el inventario, el desperdicio y el nivel de servicio de una cadena de suministros del banano. Para la simulación diseñamos un modelos de previsión de demanda Prophet, el cual tuvo en cuenta la tendencia y estacionalidad de la demanda del banano, y el tiempo de entrega y de reabastecimiento de los proveedores. Nuestro modelo logró disminuir el efecto látigo en casi una cuarta parte con respecto a un modelo de previsión básico (Naïve), también redujo el inventario en toda la cadena de suministros del banano en casi tres veces con relación al modelo Naïve. Éstos resultados fueron consistentes en todos los escenarios donde se tuvo en cuenta el nivel de desperdicio del banano, cambios en los tiempos de entrega y de reabastecimiento. Nuestro mayor aporte a la investigación fue diseñar un modelo de previsión basado en Prophet, que no se había usado para disminuir el efecto látigo en una cadena de perecederos, evidenciando que el nivel de deterioro del producto afecta en mayor medida el inventario en la cadena de suministros, en comparación con el tiempo de entrega y de reabastecimiento. Los aportes y hallazgos encontrados en la investigación, deben ser ampliados hacia nuevas líneas, que involucren el comportamiento humano como causa del efecto látigo, otro tipo de alimentos que tengan mayor nivel de vida útil, y estructuras de cadenas que tengan variaciones en sus pedidos, tiempos de producción y capacidades organizacionales / [CA] Els productes peribles representen una gran part dels productes venuts al món. Aquests productes comencen a tenir un paper més rellevant donades les condicions de seguretat alimentària que requereix la humanitat. El 2023, la població del planeta va superar els 8.000 milions d'habitants, una xifra que pressiona encara més el risc alimentari del planeta. La gestió d'aquest tipus de cadenes de subministrament és en part responsable de la seguretat alimentària de les persones; actualment es perd o es malgasta un (1) de cada tres (3) quilos d'aliments produïts al món. Aquesta situació mereix una anàlisi més profunda, i per tant cal dividir el problema en diverses parts per conèixer la connexió del problema. Hem trobat que l'efecte fuet, un fenomen que amplifica la demanda aigües amunt de la cadena de subministrament, és una mica responsable d'aquesta pèrdua i malbaratament d'aliments. La nostra investigació va trobar que hi ha diverses causes que generen l'efecte fuet, com ara la gestió de la demanda, el temps de lliurament o reposició, el nivell de deteriorament del producte, entre d'altres. Aquestes causes de l'efecte fuet es van simular en una cadena de 10 minoristes, un centre de subministrament, tres intermediaris rurals i 6 agricultors; per tal de demostrar l'impacte en l'inventari, els residus i el nivell de servei d'una cadena de subministrament de plàtan. Per a la simulació vam dissenyar un model de previsió de la demanda del Profeta, que tenia en compte la tendència i l'estacionalitat de la demanda de plàtan, i el temps de lliurament i reposició dels proveïdors. El nostre model va aconseguir reduir l'efecte fuet en gairebé una quarta part en comparació amb un model bàsic de previsió (Naïve), també va reduir l'inventari a tota la cadena de subministrament de plàtan gairebé tres vegades en comparació amb el model Naïve. Aquests resultats van ser coherents en tots els escenaris on es va tenir en compte el nivell de residus de plàtan, els canvis en els temps de lliurament i reposició. La nostra major contribució a la investigació va ser dissenyar un model de previsió basat en Prophet, que no s'havia utilitzat per reduir l'efecte fuet en una cadena perible, demostrant que el nivell de deteriorament del producte afecta en major mesura l'inventari de la cadena de subministrament. subministraments, en comparació amb el temps de lliurament i reposició. Les contribucions i troballes que es troben a la investigació s'han d'ampliar cap a noves línies, que impliquen el comportament humà com a causa de l'efecte fuet, altres tipus d'aliments que tenen un nivell més alt de vida útil i estructures de cadena que tenen variacions en els seus ordres, temps de producció i capacitats organitzatives / [EN] Perishable products represent a large part of the goods traded in the world. Given the food security conditions required by humanity, these products are beginning to play a more relevant role; in 2023, the world's population exceeded 8 billion inhabitants, putting even more pressure on the planet's food risk. This type of supply chain management is partly responsible for people's food security. One (1) of every three (3) kilos of food produced worldwide needs to be recovered or used. This situation deserves a more profound analysis; therefore, it is necessary to divide the problem into several parts to know the connection of the problem. We found that the bullwhip effect, a phenomenon that amplifies the demand upstream of the supply chain, is responsible in some way for this loss and waste of food. Our research found that several causes generate the bullwhip effect, such as demand management, delivery or replenishment time, and level of product deterioration. These causes of the bullwhip effect were simulated in a chain of 10 retailers, a supply center, three rural intermediaries, and six farmers to demonstrate the impact on a banana supply chain's inventory, waste, and service level. For the simulation, we designed a Prophet demand forecasting model, which considered the trend and seasonality of banana demand and suppliers' delivery and replenishment time. Our model managed to reduce the bullwhip effect by almost a quarter compared to a basic forecasting model (Naïve), and it also reduced inventory in the entire banana supply chain by almost three times compared to the Naïve model. These results were consistent in all scenarios where the level of banana waste, changes in delivery, and replenishment times were considered. Our most significant contribution to the research was to design a forecasting model based on Prophet, which had not been used to reduce the bullwhip effect in a perishable goods chain, showing that the level of product deterioration affects inventory in the supply chain to a greater extent, compared to delivery and replenishment time. The contributions and findings found in the research should be extended to new lines involving human behavior as a cause of the bullwhip effect, other types of foods with a longer shelf life, and chain structures with variations in their orders, production times, and organizational capacities. / Durán Peña, JA. (2024). Diseño de un modelo de previsión de demanda para reducir el efecto látigo en una cadena de suministros de perecederos [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/210911