Pengembangan Model Integrasi Persediaan Pembeli-Pemasok Tunggal Pada Produk Umur Pendek Dengan Permintaan Stokastik

Pada penelitian ini dilakukan pengembangan model inventori yang terintegrasi antara pembeli-pemasok tunggal. Produk yang digunakan sebagai obyek pada penelitian ini merupakan produk umur pendek yang mempunyai masa hidup terbatas. Pola permintaan diasumsikan bersifat stokastik pada retailer sedangkan produsen mengetahui permintaan dengan pasti. Tujuan penelitian ini adalah meminimasi total biaya pembeli dan pemasok dimana biaya yang dipertimbangkan adalah biaya operasional dan biaya yang ditimbulkan karena karakter produk yang memiliki umur terbatas. Pada model ini, pengiriman dapat dilakukan setelah seluruh proses produksi selesai dilakukan dengan tujuan untuk menguji kualitas produk dan proses pelabelan. Pengiriman untuk satu kali produksi dilakukan beberapa kali karena biaya simpan di retailer lebih tinggi dibandingkan dengan biaya simpan di pabrikan. Produk yang berasal dari satu batch produksi memiliki umur produk yang sama. Proses produksi berikutnya harus selesai pada akhir pengiriman dari proses produksi sebelumnya. Pada penelitian ini, diterapkan metode LIFO dimana kecenderungan konsumen akan memilih produk yang sisa umurnya lebih panjang. Jadi, apabila terjadi pengiriman batch produk berikutnya sedangkan batch produk sebelumnya belum habis terjual, maka sisa produk dari batch produk sebelumnya akan langsung dibuang walaupun belum mencapai masa expired date. Produk yang terbuang akan menimbulkan biaya bagi retailer. Oleh karena itu, penentuan waktu siklus produksi dan ukuran lot pengiriman yang tepat sangat penting dilakukan untuk meminimasi total biaya pada manufaktur dan retailer. Berdasarkan hasil perhitungan dengan model yang dikembangkan, waktu siklus produksi optimal terjadi sebelum masa akhir umur hidup produk dan juga menunjukkan bahwa pengambilan keputusan terintegrasi lebih baik dibandingkan dengan keputusan diambil secara parsial. ======================================================================================================================== On this study, a development of an integrated retailer-single producer inventory model of a perishable product has been done. This inventory model is developed for a stochastic demand environment for the retailer, while for the supplier it is assumed that the demand is certain. The objective of this research is to minimize the total cost of retailer and supplier with operational cost and outdate cost (the cost of expired products due to its limited life-span). On this model all products of one production cycle is sent after the whole cycle is finished for the purpose of quality control and labeling.The shipment is conducted several times for one production cycle due to the high inventory cost at the retailer end. Products that are made on the same production cycle have identical life-span. One cycle of production has to be finished before the end of last shipment of the previous production cycle. On this study a LIFO method is applied, thus when a new shipment arrives, the products of the previous shipment will be discarded even if it have not reached its expired date. This discarded products will invoke a cost for the retailer. Hence, the determination of production cycle time and shipment’s lot size is crucial to minimize the total cost for manufacturer and retailer. The result shows that the optimum production cycle time occurs before the product end-of-life time. It also shows that an integrated decision is better than a partial one

Grocery omnichannel perishable inventories: performance measures and influencing factors

Purpose- Perishable inventory management for the grocery sector has become more challenging with extended omnichannel activities and emerging consumer expectations. This paper aims to identify and formalize key performance measures of omnichannel perishable inventory management (OCPI) and explore the influence of operational and market-related factors on these measures. Design/methodology/approach- The inductive approach of this research synthesizes three performance measures (product waste, lost sales and freshness) and four influencing factors (channel effect, demand variability, product perishability and shelf life visibility) for OCPI, through industry investigation, expert interviews and a systematic literature review. Treating OCPI as a complex adaptive system and considering its transaction costs, this paper formalizes the OCPI performance measures and their influencing factors in two statements and four propositions, which are then tested through numerical analysis with simulation. Findings- Product waste, lost sales and freshness are identified as distinctive OCPI performance measures, which are influenced by product perishability, shelf life visibility, demand variability and channel effects. The OCPI sensitivity to those influencing factors is diverse, whereas those factors are found to moderate each other's effects. Practical implications- To manage perishables more effectively, with less waste and lost sales for the business and fresher products for the consumer, omnichannel firms need to consider store and online channel requirements and strive to reduce demand variability, extend product shelf life and facilitate item-level shelf life visibility. While flexible logistics capacity and dynamic pricing can mitigate demand variability, the product shelf life extension needs modifications in product design, production, or storage conditions. OCPI executives can also increase the product shelf life visibility through advanced stock monitoring/tracking technologies (e.g. smart tags or more comprehensive barcodes), particularly for the online channel which demands fresher products. Originality/value- This paper provides a novel theoretical view on perishables in omnichannel systems. It specifies the OCPI performance, beyond typical inventory policies for cost minimization, while discussing its sensitivity to operations and market factors

Finite-horizon operations planning for a lean supply chain system

This dissertation studies an operational policy for a lean supply chain system consisting of a manufacturer, multiple suppliers and multiple buyers. The manufacturer procures raw materials from the suppliers and converts them into finished products, which are then shipped in batches to the buyers at certain intervals of times. Three distinct but inseparable problems are addressed: single supplier and single buyer with fixed delivery size (FD), multiple suppliers and multiple buyers with individual delivery schedule (MD), and time dependent delivery quantity with trend demand (TD). The mathematical formulations of these supply systems are categorized as mixed-integer, nonlinear programming problems (MINLAP) with discrete, non-convex objective functions and constraints. The operations policy determines the number of orders of raw material, beginning and ending times of cycles, production batch size, production start time, and beginning and ending inventories. The goal is to minimize the cost of the two-stage, just-in-time inventory system that integrates raw materials ordering and finished goods production system. The policy is designed for a finite planning horizon with various phases of life cycle demands such as inception (increasing), maturity (level) and phasing out (declining). Analytical results that characterize the exact, optimal policy for the problems described above are devised to develop efficient and optimal computational procedures. A closed-form heuristic that provides a near-optimal solution and tight lower bound is proposed for the problem FD. A network model to represent the problems is proposed and network-based algorithms are implemented to solve the problems FD, MD and TD optimally. The computational complexities of the algorithms are Θ(N2) or O(N3) where N is the total number of shipments in the planning horizon. Numerical tests to assess the robustness and quality of the methods show that the present research provides superior results. Production and supply chain management play an important role in ensuring that the necessary amounts of materials and parts arrive at the appropriate time and place. A manager, using the models obtained in this research, can quickly respond to consumers\u27 demand by effectively determining the right policies to order raw materials, to deliver finished goods, and to efficiently manage their production schedule

Modelos de Inventarios con Productos Perecederos: Revisión de la Literatura

This paper presents a review of the main characteristics of the mathematical modelsdeveloped by the scientific community in order to determine an optimal inventory policyfor deteriorating items. Thus, a classified bibliography of 390 articles published from2001 to 2014 in high-impact journals is submitted while considering the type of demandand deterioration, the integration of inventory and pricing decisions, the inclusionof shortage and/or the time value of money, the consideration of multiple items and/ormulti-echelon systems, and the incorporation of uncertain parameters other than demand.Finally, research questions not yet addressed by the research community in the field ofinventory control for deteriorating items are pointed out.En el presente artículo se lleva a cabo una revisión de las principales características estudiadas por la comunidad científica en el desarrollo de modelos matemáticos que buscan definir una política de inventario óptima para productos que se deterioran. De este modo, se referencian 390 artículos publicados a partir del año 2001 en revistas de gran impacto, teniendo en cuenta: el tipo de demanda y deterioro representado en los modelos matemáticos, el estudio de una política de precio óptima, la inclusión de faltantes y/o valor del dinero en el tiempo, el estudio de múltiples productos y/o dos o más eslabones de la cadena de suministro, y la utilización de parámetros o variables difusas. Finalmente, se identifican oportunidades de investigación que a la fecha no han sido abordadas por la comunidad científica en este campo del conocimiento

Üretimde parti büyüklüğü belirleme yöntemleri : bir gıda işletmesi örneği

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Günümüzün rekabetçi ve mücadeleci iş ortamında işletmeler için önemi oldukça artan ve hatta birinci sıraya yerleşen en düşük maliyetle ve en kısa sürede üretim anlayışı sonucu işletmeler üretim standart zamanların ve hazırlık sürelerinin minimizasyonu konularına ağırlık vermişlerdir. Bu husus, müşteri tatmininin müşterinin istediği ürünü müşterinin istediği anda, şekilde ve kalitede sunmak zorunluluğunun bir sonucudur. İşletme içinde bir ürünün üretim aşamalarından geçip son ürün haline gelene kadar ki tüm aşamalarında bekleme sürelerinin kısaltılması, işlem zamanlarının minimuma indirilmesi ve ürünün planlanan zaman dışına taşmaması için işletmelerin çizelgeleme ve sıralama tekniklerini uygulamaları zorunludur.Bütün bu sayılan hususların hepsi firmaların ortak amacı olan müşteri memnuniyetini sağlamaya yöneliktir.In todays? competitive business environment, as a result of the production perception at the lowest cost and shortest time, the enterprises are giving much more importance to the issues of reducing the setup times and standard production times just because the issues gaining much more value than before. This is a consequence of introducing the product that the customer demands at the time the customer demands in its? perfect shape and quality. For reducing the waiting times and delays of the product, minimizing the processing times and preventing all the lateness and tardiness at all the manufacturing stages from the beginning till the finished product, companies should feel themselves to be in the need of utilizing the sequencing and scheduling techniques.All of these situations and issues are standing for common objective of the companies? satisfying the customer satisfaction

An investigation of production and transportation policies for multi-item and multi-stage production systems

Die vorliegende kumulative Dissertation besteht aus fünf Artikeln, einem Arbeitspapier und vier Artikeln, die in wissenschaftlichen Zeitschriften veröffentlicht wurden. Alle fünf Artikel beschäftigen sich mit der Losgrößenplanung, jedoch mit unterschiedlichen Schwerpunkten. Artikel 1 bis 4 untersuchen das Economic Lot Scheduling Problem (ELSP), während sich der fünfte Artikel mit einer Variante des Joint Economic Lot Size (JELS) Problems beschäftigt. Die Struktur dieser Dissertation trägt diesen beiden Forschungsrichtungen Rechnung und ordnet die ersten vier Artikel dem Teil A und den fünften Artikel dem Teil B zu

Combining lasers with emerging technologies for minimal processing

Conservative estimates place the economic cost of food poisoning at hundreds of millions of pounds per annum. Recent market expansion of minimally processed fresh fruit and vegetables has resulted from the consumer's desire of convenience foods that have been peeled, cut, shredded or even washed. These produce, however, are likely to be contaminated. Such produce has a natural high microbiological burden. Minimally processing the food results in surface damage that is likely to favour bacterial adhesion. The cutting process leads to cellular damage, which coupled with increased adhesion and leakage of intracellular material, can lead to increased growth rate of spoilage organisms or pathogens. Minimally processed fruit and vegetables are often washed in water or water containing chemicals. The wash water can help distribute bacteria into the damaged sites on the processed fruit or vegetables. The use of chlorine has been associated with the production of carcinogenic and mutagenic substances and consequently there are fears over its use and potential accumulation within the body. Many government policies are encouraging people to eat more fresh fruit and vegetables. It is important therefore, that processors use the best practice available to supply fruit and vegetables with the minimum risk to consumers through digestion of pathogens and with a long a shelf life as possible to aid distribution channels, minimise waste and increase profits for processors. This research was seeking to identify novel ways to reduce the levels of contamination on carrots and potatoes and extend their shelf-life. Technology was developed to exploit different parts of the electromagnetic spectrum to kill bacteria. The systems included a CO2 laser, conventional UV lamps, and microwave irradiation. As an adjunct to these processes, H2O2 treatments and combination treatments were used. These systems were combined to kill bacteria on different substrates, fruit and vegetables. Comparison of shelf life tests and optimum treatment processes were also done. On carrots and potatoes the investigation of vitamin A and C levels, respectively, also indicated that their nutritious quality had not been degraded with any of the treatments. Using ozone as a bactericide and bioluminescence as a measurement of viability or metabolic activity, a real time monitoring system was developed to measure surface decontamination. The Escherichia coli strain DH5alpha PT7-3 with its plasmid encoded with ampicillin resistance contained the lux ABCDE genes from Xenorhadus luminescence, were used as the reference organism. Results showed that the bioluminescence responded instantaneously to treatment. Bioluminescence measurements were recorded in decibel, after 15 min of ozone treatment the bioluminescence was reduced by 4 dB and E. coli (lux) were inactivated. To investigate the response of various Gram-positive and Gram-negative organisms to ozone treatment, Campylobacter jejuni, Bacillus cereus, Escherichia coli, Listeria monocytogenes, Salmonella typhimurium and Staphylococcus aureus were inoculated on plates and treated with ozone. The treatment achieved about 2 - 2.5 D-value reduction on plates. The same treatment was less effective when the experiments were repeated on contaminated chicken and salmon samples. A log reduction range between 0.37 - 1.5 was achieved

Modelling and Determining Inventory Decisions for Improved Sustainability in Perishable Food Supply Chains

Since the introduction of sustainable development, industries have witnessed significant sustainability challenges. Literature shows that the food industry is concerned about its need for efficient and effective management practices in dealing with perishability and the requirements for conditioned storage and transport of food products that effect the environment. Hence, the environmental part of sustainability demonstrates its significance in this industrial sector. Despite this, there has been little research into environmentally sustainable inventory management of deteriorating items. This thesis presents mathematical modelling based research for production inventory systems in perishable food supply chains. In this study, multi-objective mixed-integer linear programming models are developed to determine economically and environmentally optimal production and inventory decisions for a two-echelon supply chain. The supply chain consists of single sourcing suppliers for raw materials and a producer who operates under a make-to-stock or make-to-order strategy. The demand facing the producer is non-stationary stochastic in nature and has requirements in terms of service level and the remaining shelf life of the marketed products. Using data from the literature, numerical examples are given in order to test and analyse these models. The computational experiments show that operational adjustments in cases where emission and cost parameters were not strongly correlated with supply chain collaboration (where suppliers and a producer operate under centralised control), emissions are effectively reduced without a significant increase in cost. The findings show that assigning a high disposal cost, limit or high weight of importance to perished goods leads to appropriate reduction of expected waste in the supply chain with no major cost increase. The research has made contributions to the literature on sustainable production and inventory management; providing formal models that can be used as an aid to understanding and as a tool for planning and improving sustainable production and inventory control in supply chains involving deteriorating items, in particular with perishable food supply chains.the Ministry of Science and Technology, the Royal Thai Government