Tedarik zinciri optimizasyon çalışmaları: Literatür araştırması ve sınıflama

Supply chain planning is an integrated process in which a group of several organizations, such as suppliers, producers, distributors and retailers, work together. It comprises procurement, production, distribution and demand planning topics. These topics require taking strategical, tactical and operational decisions. This research aims to reveal which supply chain topics, which decision levels, and which optimization methods are mostly studied in supply chain planning. This paper presents a total of 77 reviewed works published between 1993 and 2016 about supply chain planning. The reviewed works are categorized according to following elements: decision levels, supply chain optimization topics, objectives, optimization models.Tedarik Zinciri, tedarikçiler, üreticiler, dağıtıcılar ve toptancılar gibi bir grup organizasyonu birleştiren entegre bir süreçtir. Tedarik, üretim, dağıtım ve talep planlama konularını içerir. Bu konular stratejik, taktik ve operasyonel kararlar almayı gerektirir. Bu araştırma tedarik zinciri planlamasında hangi tedarik zinciri konularının, hangi karar/planlama seviyelerinin ve hangi optimizasyon metotlarının literatürde en çok çalışıldığını göstermektedir. Çalışma 1993 ve 2016 yılları arasındaki tedarik zinciri planlama konusundaki 77 adet çalışmanın incelenmesine ait sonuçları sunmaktadır. İncelenen çalışmalar şu kriterlere gore kategorize edilmiştir: karar seviyesi, tedarik zinciri optimizasyon konuları, amaçlar, optimizasyon modelleri

Supply Chain Optimization Studies: A Literature Review and Classification

Supply chain planning is an integrated process in which a group of several organizations, such as suppliers, producers, distributors and retailers, work together. It comprises procurement, production, distribution and demand planning topics. These topics require taking strategical, tactical and operational decisions. This research aims to reveal which supply chain topics, which decision levels, and which optimization methods are mostly studied in supply chain planning. This paper presents a total of 77 reviewed works published between 1993 and 2016 about supply chain planning. The reviewed works are categorized according to following elements: decision levels, supply chain optimization topics, objectives, optimization models. 

Supply Chain Optimization Studies: A Literature Review and Classification

Supply chain planning is an integrated process in which a group of several organizations, such as suppliers, producers, distributors and retailers, work together. It comprises procurement, production, distribution and demand planning topics. These topics require taking strategical, tactical and operational decisions. This research aims to reveal which supply chain topics, which decision levels, and which optimization methods are mostly studied in supply chain planning. This paper presents a total of 77 reviewed works published between 1993 and 2016 about supply chain planning. The reviewed works are categorized according to following elements: decision levels, supply chain optimization topics, objectives, optimization models. 

Evaluating vendor managed inventory systems: how incentives can benefit supply chain partners

In a vendor managed inventory (VMI) system, the effects of financial incentives on the entire supply chain (SC) and on the individual firms are investigated in this study. To this end, order management, order replenishment and inventory control activities of a two-echelon SC are examined via modeling using discrete event simulation. By determining the appropriate parameters for the incentives with scenario analysis, balanced profit distribution between buyers and a supplier in VMI is established. Simulation outputs of the traditional model, VMI only and VMI with incentives models are compared based on profits with paired comparisons. In VMI with incentives, both buyers, and the supplier experience higher benefits than the traditional system. This study provides a new method which eliminates the unbalanced benefit distribution due to VMI and offers almost equal benefits to the participating firms. With financial incentives, firms are encouraged to share information with each other to work in a coordinated SC

The value of integrated planning for production, inventory, and routing decisions: A systematic review and meta-analysis

This paper presents a comparison of sequential and integrated planning for the production routing problem, in which production, inventory, and routing decisions must be made. The aim is to estimate the expected value of treating the problems as a whole, rather than making decisions sequentially. In particular, the following research questions are posed: What is the expected cost reduction when combining production, inventory, and routing in a single modeling framework, compared to solving the problems individually in a sequence? Under which circumstances is it most beneficial to tackle an integrated problem? In other words, the goal is to establish whether the solutions obtained by the integration are clearly better than approximate solutions obtained by a more simplified process, and if so, under which circumstances this difference is the most pronounced. To answer these research questions, a systematic review was performed, resulting in a set of 20 relevant articles that were analyzed in depth. For the first research question, computational results from 15 articles were obtained and analyzed through a meta-analysis. The analysis estimated an expected cost savings provided by integration of 11.08%, with a 95% confidence interval of [6.58%, 15.58%]. For the second research question, individual results obtained via sensitivity analyses in 20 relevant articles were summarized qualitatively, enabling insights into how the potential savings by integration is influenced by parameters such as the degrees of freedom, the cost, and the capacity. © 2022 The AuthorsGrantová Agentura České Republiky, GA ČR; Norges Forskningsråd; Univerzita Tomáše Bati ve Zlíně: GA 20-00091

Minimizing the total cost in an integrated Vendor-Managed Inventory System

3In this paper we consider a complex production-distribution system, where a facility produces (or orders from an external supplier) several items which are distributed to a set of retailers by a fleet of vehicles. We consider Vendor-Managed Inventory (VMI) policies, in which the facility knows the inventory levels of the retailers and takes care of their replenishment policies. The production (or ordering) policy, the retailers replenishment policies and the transportation policy have to be determined so as to minimize the total system cost. The cost includes the fixed and variable production costs at the facility, the inventory costs at the facility and at the retailers and the transportation costs, that is the fixed costs of the vehicles and the traveling costs. We study two different types of VMI policies: The order-up-to level policy, in which the order-up-to level quantity is shipped to each retailer whenever served (i.e. the quantity delivered to each retailer is such that the maximum level of the inventory at the retailer is reached) and the fill-fill-dump policy, in which the order-up-to level quantity is shipped to all but the last retailer on each delivery route, while the quantity delivered to the last retailer is the minimum between the order-up-to level quantity and the residual transportation capacity of the vehicle. We propose two different decompositions of the problem and optimal or heuristic procedures for the solution of the subproblems. We show that, for reasonable initial values of the variables, the order in which the subproblems are solved does not influence the final solution. We will first solve the distribution subproblem and then the production subproblem. The computational results show that the fill-fill-dump policy reduces the average cost with respect to the order-up-to level policy and that one of the decompositions is more effective. Moreover, we compare the VMI policies with the more traditional Retailer-Managed Inventory (RMI) policy and show that the VMI policies significantly reduce the average cost with respect to the RMI policy.reservedmixedBERTAZZI L; PALETTA G; M. SPERANZABertazzi, Luca; Paletta, G; Speranza, Maria Grazi

A fix-and-optimize heuristic for the integrated fleet sizing and replenishment planning problem with predetermined delivery frequencies

Bu tez çalışmasında satıcı yönetimli stok politikası uygulayan sistemler için filo büyüklüğü ve ikmal planlamasının entegre şekilde belirlenmesi ele alınmıştır. Önceden belirlenmiş frekans setine göre ikmal edilen müşteri seti mevcuttur. Araç filosu birden fazla farklı araçtan oluşmaktadır ve bu araçlar sabit kilometre başı maliyetler, taşıma kapasitesi ve edinme maliyetleri açısından farklılık arz etmekteler. Müşteri talepleri deterministik değerler olarak alınmıştır. Bu problemde verilen asıl karar araç- frekans – müşteri üçlüsünün atamasıdır. Bu atama kararları sonucunda, araç edinme maliyeti, rotalama maliyeti, envanter tutma maliyeti ve sabit ikmal yapma maliyetinden oluşan toplam maliyet elde edilmektedir. Bu modeldeki en önemli basitleştirme, rotalama maliyetinin bir tur içerisinde ziyaret edilen müşterilerin sayısına bağlı olarak yaklaşık bir değer şeklinde kullanılmasıdır. Bu tez çalışmasında geliştirilen model literatürde yeni bir modeldir ve filo büyüklüğü belirleme ve ikmal planlaması kararlarını entegre şekilde vermektedir. Bizim problem kutulama probleminin özel haline dönüşebilmesi nedeni ile NP-Zor bir problemdir. Uzun çözüm sürelerini ortadan kaldırmak amacıyla sabitle ve optimize et sezgiseli çözüm yöntemi olarak önerilip uygulanmıştır. Sabitle ve optimize et yöntemi ana problemi bazı değişkenleri ikili ve diğer değişkenleri doğrusal olarak gevşetilmiş küçük problemlere ayırmaktadır, ve doğrusal karar değişkenleri her iterasyonda sabitlenmektedir. Aynı zamanda, önerilen sezgisel yönteminin etkenliği rassal olarak üretilmiş büyük problem setlerine uygulanarak gösterilmiştir.We tackled an integrated fleet sizing and replenishment planning problem in a vendor managed inventory system. There is a set of customers which must be replenished based on a given set of predetermined frequencies. The vehicle fleet consists of multiple types of heterogeneous vehicles which differ in carrying capacity, cost per kilometer, and ownership costs. Customer demands are taken as deterministic values. The main decision we make in this problem is the triple assignment of vehicle-frequency-customer. As a result of these assignment decisions, we obtain an annual costs consisting of vehicle ownership cost, routing cost, inventory holding and fixed replenishment costs. A key simplification in the model is the use of linear approximation for the routing cost based on the number of customers visited in a tour. The developed model, which is new in the literature, integrates fleet sizing and replenishment planning decisions. Our problem is NP-hard since it can be shown that a special case of our problem is a bin packing problem. In order to solve large problems efficiently, we suggested and applied a fix and optimize heuristic as a solution procedure. This fix and optimize heuristic divides the problem into smaller problems in which some variables are binaries and the others are linearly relaxed, and it fixes the linear decision variable iteratively. We also showed the effectiveness of the suggested heuristic solution procedure on a large set of randomly generated problems

Evolutionary multi-objective optimization for the vendor-managed inventory routing problem

Orientador: Fernando José Von ZubenDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A classe de problemas de estoque e roteamento está presente em várias áreas, incluindo indústria automobilística e gerência de numerário no reabastecimento de caixas eletrônicos. Supondo que o fornecedor é responsável pela estocagem e distribuição dos produtos, sujeito a um conjunto de restrições, o desafio que se apresenta é a determinação de uma política ótima, mais especificamente quais clientes atender, qual quantidade a ser fornecida a cada cliente e qual rota empregar visando a minimização dos custos. Este trabalho apresenta uma proposta de solução para uma das mais comuns formulações do problema: um produto é distribuído a partir de um fornecedor para vários clientes em um horizonte de tempo definido. O transporte é realizado por um veículo de capacidade limitada. Para produzir a otimização simultânea de ambos os objetivos, minimização dos custos de transporte e estoque, a proposta segue uma abordagem multiobjetivo e se baseia no uso do algoritmo SPEA2 (do inglês, Strength Pareto Evolutionary Algorithm 2), incluindo inovações na representação de soluções-candidatas, nos operadores genéticos e de busca local. A fronteira de Pareto estimada é então composta de múltiplas soluções não-dominadas, representando compromissos distintos entre custos de transporte e estoque. Como casos de estudo, são tomadas instâncias de médio porte extraídas da literatura e são geradas instâncias de grande porte. Para as instâncias de médio porte, as fronteiras de Pareto estimadas em cada caso são comparadas com as respectivas soluções ótimas da versão mono-objetivo de cada problema, pois já existe um algoritmo exato de solução para a formulação mono-objetivo de instâncias de médio porteAbstract: The class of inventory routing problems (IRP) is present in several areas, including automotive industry and cash management for ATM networks. Given that the supplier is responsible for managing the product inventory and replenishment, subject to a set of restrictions, the challenge here is to determine an optimal policy, more specifically which retailers to serve, the quantity to deliver to each retailer and which routes to employ in order to minimize the cost. This work presents a proposal to solve one version of the IRP usually found in the scientific literature: a product is distributed from a supplier to several retailers in a defined time horizon. Shipment is performed by a vehicle with limited capacity. To perform the simultaneous optimization of both objectives, minimization of transportation and inventory costs, the proposal follows a multi-objective approach based on SPEA2 (Strength Pareto Evolutionary Algorithm 2), including innovative aspects mainly associated with the representation of candidate solutions, genetic operators and local search. The Pareto front is then composed of multiple non-dominated solutions with distinct trade-offs between transportation and inventory costs. As case studies, medium size instances extracted from the literature are considered and large size instances are generated. For the medium size instances, the estimated Pareto fronts are compared, in each case, with the corresponding optimal solutions associated with the single-objective version of each problem, given that there is already an exact algorithm to solve such medium size single-objective instancesMestradoEngenharia de ComputaçãoMestre em Engenharia Elétric

Performance Improvement Through Benchmarking for Small and Medium Manufacturers (SMM)

Die wichtigsten Kostenfaktoren innerhalb einer Lieferkette lassen sich drei Kategorien zuordnen: Produktions-, Transport-und Lagerkosten. Die Strukturen dieser operativen Kosten im Hinblick auf die Gesamtkosten variieren stark je nach Industriesektor. Produktionskosten stellen dennoch die höchste Kostenart in fast allen Branchen dar, weniger bedeutend folgen danach jeweils die Transport- und Lagerkosten. Die Optimierung einer dieser Kategorien ohne Rücksicht auf die anderen kann zur Erhöhung der Gesamtkosten sowie der allgemeinen Leistungsfähigkeit führen. Diese Dissertation befasst sich mit dem „production distribution problem“ wobei synchronisierte Strategien entwickelt werden können, um die Leistung der Supply Chain zu verbessern und gleichzeitig die Gesamtkosten zu minimieren. Dazu wurde eine Fallstudie aus der Realität untersucht, nämlich das Praxisbeispiel eines Herstellers von Waschmitteln. Zwei Hauptszenarien werden bewertet. Das erste Szenario ist der konventionelle Plan, wobei die Hersteller dominieren. Dies bedeutet, dass der Hersteller findet seinen eigenen optimalen Job-Scheduling-Plan, während die Distribution versucht mit Hilfe dessen ihren optimalen Plan zu finden. Dadurch erhöhen sich die Distributionskosten. Das zweite Szenario betrifft die Synchronisation der Produktions-, Lagerhaltungs- und Transportzeitpläne. Ein zu diesem Zweck entwickeltes Java-Programm und die Job-Scheduling-Software Simal wurden für die Modellierung der konventionellen und integrierten Szenarien verwendet. Beide Szenarien wurden verglichen und validiert. Die Fallstudie betrachtet mehrere Produkte sowie ein schwer zu planendes flowshop- System. Die Ergebnisse zeigen, dass die Gesamtkosten, einschließlich der Einrichtungs-, Lager- und Transportkosten, minimiert werden können, wenn das synchronisierte System angewendet wird.The main cost factors within a supply chain can be put into the categories of production, transportation, and inventory costs. The composition of these operational costs relative to total costs varies largely by industry. However, production cost is the largest of all in almost all the industries, followed by transportation and inventory costs. Optimizing one of these categories without consideration of the others may increase the total cost and reduce the overall performance. This dissertation deals with the production distribution problem of developing synchronized strategies to improve the supply chain performance and to minimize the total cost. A real case study is investigated. This real-life case study is a powder detergent plant located in Libya. There are two main scenarios evaluated. The first scenario is the conventional plan, where the manufacturer dominates. This means the manufacturer finds his own optimum job-scheduling plan, and the distributor tries to find the optimum plan according to it. This will increase the distribution cost. The second scenario involves synchronizing the production, inventory and transportation schedules. A Java program and SimAl (job-schedulingsoftware) were constructed for modelling conventional and integrated scenarios. The two scenarios were compared and validated. The case study considered multiple products and a flowshop system which is difficult to schedule. The results show that the total costs, including setup, inventory and transportation, can be minimized when the synchronized system is applied