Comparing conventional and distributed approaches to simulation in complex supply-chain health systems

Decision making in modern supply chains can be extremely daunting due to their complex nature. Discrete-event simulation is a technique that can support decision making by providing what-if analysis and evaluation of quantitative data. However, modelling supply chain systems can result in massively large and complicated models that can take a very long time to run even with today's powerful desktop computers. Distributed simulation has been suggested as a possible solution to this problem, by enabling the use of multiple computers to run models. To investigate this claim, this paper presents experiences in implementing a simulation model with a 'conventional' approach and with a distributed approach. This study takes place in a healthcare setting, the supply chain of blood from donor to recipient. The study compares conventional and distributed model execution times of a supply chain model simulated in the simulation package Simul8. The results show that the execution time of the conventional approach increases almost linearly with the size of the system and also the simulation run period. However, the distributed approach to this problem follows a more linear distribution of the execution time in terms of system size and run time and appears to offer a practical alternative. On the basis of this, the paper concludes that distributed simulation can be successfully applied in certain situations

Penjadwalan Pemesanan Material Pembentuk Komponen Pesawat Terbang Untuk Meminimasi Total Biaya Inventory

PT Goodrich PINDAD Aeronautical Systems Indonesia is one of the manufacturing company, where the company engaged in the assembly and sale of aircraft components. The Company often experience a sudden the purchase of materials, which in turn will lead so huge costs because shipping must be done via airfreight. The results of study can be seen that the product divided in two groups: independent demand and dependent demand. Based on the ABC analysis, the group category A must scheduled because it is a critical product. Number of products of group A are available eight and absorb substantial funds in the amount of 79% of the total goods ordered

Model Persediaan Barang Deteriorasi dengan Exponential Declining Demand, Time-Varying Holding Cost dan Return

Pada artikel ini diusulkan model matematika EOQ (Economic Order Quantity) untuk barang yangmengalami deteriorasi. Model ini dikembangkan dengan mempertimbangkan permintaan yang menurun secaraeksponensial (Exponential Declining Demand), tingkat deterioirasi yang konstan, memungkinkan shortage, danterjadi return. Biaya penyimpanan, biaya deteriorasi, biaya shortage, dan biaya return diperhitungkan dalammanajemen persediaan. Tujuan dari model ini adalah untuk meminimumkan total biaya persediaan denganmenentukan waktu return optimal dan jumlah pesanan optimal. Contoh numerik disajikan untukmenggambarkan model dan analisis sensitivitas dari berbagai parameter dilakukan

Using optimal control to adjust the production rate of a deteriorating inventory system

AbstractThis work represents is another contribution to the application of optimal control theory to production inventory systems. We consider a firm that produces some product at a certain rate and aims at improving this rate. We successfully formulated the model as an optimal control problem and obtained an explicit solution using the maximum principle. An illustrative example is provided and the sensitivity of the model to some of the system parameters was addressed

[[alternative]]Deterministic Production Lot-Size Models with Shortages for Fluctuating Demand and Unit Purchase Cost

計畫編號：NSC90-2416-H032-017研究期間：200108~200207研究經費：431,000[[sponsorship]]行政院國家科學委員

Inventory control for a non-stationary demand perishable product: comparing policies and solution methods

This paper summarizes our findings with respect to order policies for an inventory control problem for a perishable product with a maximum fixed shelf life in a periodic review system, where chance constraints play a role. A Stochastic Programming (SP) problem is presented which models a practical production planning problem over a finite horizon. Perishability, non-stationary demand, fixed ordering cost and a service level (chance) constraint make this problem complex. Inventory control handles this type of models with so-called order policies. We compare three different policies: a) production timing is fixed in advance combined with an order up-to level, b) production timing is fixed in advance and the production quantity takes the age distribution into account and c) the decision of the order quantity depends on the age-distribution of the items in stock. Several theoretical properties for the optimal solutions of the policies are presented. In this paper, four different solution approaches from earlier studies are used to derive parameter values for the order policies. For policy a), we use MILP approximations and alternatively the so-called Smoothed Monte Carlo method with sampled demand to optimize values. For policy b), we outline a sample based approach to determine the order quantities. The flexible policy c) is derived by SDP. All policies are compared on feasibility regarding the α-service level, computation time and ease of implementation to support management in the choice for an order policy.National project TIN2015-66680-C2-2-R, in part financed by the European Regional Development Fund (ERDF)

[[alternative]]An Optimal Ordering Policy for Non-instantaneous Deteriorating Items under Permissible Delay in Payments

計畫編號：NSC94-2213-E032-011研究期間：200508~200607研究經費：668,000[[abstract]]本研究將針對非即時退化的物品，在供應商提供允許延遲付款優惠下，建立一個適 當的存貨模式，並找出使存貨相關總成本為最小的最適補貨策略。我們將發展一些理 論結果，且提出一個簡單容易使用的方法，以方便得到在不同情況下的最適補貨週期。 我們也將舉一些數值範例說明求解過程，並做敏感度分析。[[sponsorship]]行政院國家科學委員

[[alternative]]A Comparison between Two Pricing and Lot-Sizing Models with Partial Backlogging and Deteriorated Items

計畫編號：NSC93-2416-H032-007研究期間：200408~200507研究經費：374,000[[abstract]]最近，Abad（2003）討論了退化性產品在有限生產率、指數退化率、部分欠撥和 銷售損失下的售價和批量問題。他的模式是週期開始時即生產，由於生產率大於需求 率，存貨逐漸累積；當存貨數量達到某一水準時，便停止生產。接著，庫存量隨著市 場的需求及退化逐漸減少並產生缺貨現象；此時，只有部分顧客願意等待欠撥。當欠 撥數量達到某一水準時，便又開始生產，缺貨數量逐漸被補足。本研究，我們首先將 推廣他的模式，在目標函數中加入欠撥成本和商譽損失成本。接著，對相同的售價和 批量問題，我們建立一個類似於Goyal and Giri（2003）的新模式。此模式是週期開始 時不生產，造成缺貨，而只有部分顧客願意等待欠撥，當欠撥數量達到某一水準時， 便開始生產，缺貨數量逐漸被補足，接著產生存貨。當存貨數量累積到某一水準時， 便停止生產，庫存量隨著市場的需求及退化，逐漸降至零為止。我們以分析的方法比 較這兩個模式的總利潤，並且指出在某些條件下，其中一個模式優於另一個模式。最 後，舉一些例子說明上述的結論。[[sponsorship]]行政院國家科學委員