Simulation model for closed loop repairable parts inventory system with service level performance measures

2016 ◽  
Vol 23 (1) ◽  
pp. 18
Author(s):  
Rohit Kapoor ◽  
Bhavin J. Shah
Keyword(s):  
Simulation Model ◽  
Performance Measures ◽  
Closed Loop ◽  
Service Level ◽  
Inventory System ◽  
Level Performance ◽  
Repairable Parts

scholarly journals OPTIMIZING WORKLOAD ALLOCATION IN A NETWORK OF HETEROGENEOUS COMPUTERS

2011 ◽  
Author(s):  
Rahela Rahim ◽  
Ku Ruhana Ku-Mahamud
Keyword(s):  
Response Time ◽  
Performance Measures ◽  
Queue Length ◽  
Closed Loop ◽  
Optimization Technique ◽  
Allocation Model ◽  
Workload Allocation ◽  
The One ◽  
Level Performance ◽  
Total Workload

The allocation of workload to a network of computers is investigated. A new workload allocation model based on Generalized Exponential (GE) distribution is proposed for user-level performance measures. The criterion used for effective workload allocation is the one that minimizes the expected response time in systems to which jobs are routed. A closed-loop expression for workload arrival to minimize systems means queue length and response time are derived using the optimization technique. Results are presented with numerical examples and sensitivity analysis with respect to changes of total workload. Results are verified using the simulation technique.  

scholarly journals After sales services for repairable parts with service level agreements

2015 ◽  
Author(s):  
◽  
Rana Afzali Baghdadabadi
Keyword(s):  
Objective Function ◽  
Numerical Experiments ◽  
Service Level ◽  
Inventory System ◽  
Service Performance ◽  
Base Stock ◽  
Mixed Integer ◽  
Contract Duration ◽  
Operational Costs ◽  
Repairable Parts

In this study, inventory systems for repairable-parts with service level consideration are studied. The first study develops a multi-parts inventory system and transportation decisions. A failed part might be repairable at the stock location, or at repair facilities, or it might be non repairable, which should be replaced by a new purchased part. The objective is to find the base stock levels and shipping modes that maximizes the total weighted fill rate within a given budget. An optimization model and the properties of the objective function are developed. An approximation method is used to eliminate the highly non-linearity of the objective function, and the optimality of approximated model is discussed under specific conditions. The results of numerical experiments show the benefits of alternative transportation mode. Failure rates are observed to be the most significant factor in determining the assigned base stock level and shipping mode. A two-echelon repairable-parts inventory system is considered in the second study, where emergency purchasing and ordering from the central warehouse are allowed to obtain high service level. A dynamic decision making model is developed that minimizes the system's operational costs, including transportation, stocking and purchasing new parts during the contract period, and provides the required service level over the contract period. The numerical experiments show the benefits of purchasing and ordering options in systems with high penalty costs and long repair times, especially where the allocated inventory to the stock location is not enough to guarantee the target service level. Our model also provides the best base stock levels that minimize the operational costs and initial investments at the stock location. In the previous studies, we assumed that the contractual terms are given to the supplier and are considered as fixed parameters. The main focus in the last study is providing the contractual terms to the supplier that prompts him to provide a better service performance. The decision maker in this system is the customer, and he requires a minimum service level from the supplier. The customer is willing to grant the supplier for a better service performance by providing incentives. The objective is to find the terms of contract, the fixed payment, incentives and contract duration, that maximize the service provided by the supplier during the planning horizon under a constrained budget. We first develop a mixed integer programming model assuming the information on the supplier's cost and service is visible to the customer. Then, we extend our model to a robust model in which the uncertainty of information is included.

Pricing and service decision of dual-channel operations in an O2O closed-loop supply chain

2017 ◽  
Vol 117 (8) ◽  
pp. 1567-1588 ◽  
Author(s):  
Lingcheng Kong ◽  
Zhiyang Liu ◽  
Yafei Pan ◽  
Jiaping Xie ◽  
Guang Yang
Keyword(s):  
Supply Chain ◽  
Closed Loop ◽  
Wholesale Price ◽  
Revenue Sharing ◽  
Service Level ◽  
Return Rate ◽  
Transfer Payment ◽  
Channel Conflict ◽  
Content Type ◽  
Dual Channel

Purpose The online direct selling mode has been widely accepted by enterprises in the O2O era. However, the dual-channel (online/offline, forward/backward) operations of the closed-loop supply chain (CLSC) changed the relationship between manufacturers and retailers, thus resulting in channel conflict. The purpose of this paper is to take a dual-channel operations of CLSC as the research target, where a manufacturer sells a single product through a direct e-channel as well as a conventional retail channel; the retailer are responsible for collecting used products in the reverse supply chain and the manufacturer are responsible for remanufacturing. Design/methodology/approach The authors build a benchmark model of dual-channel price and service competition and take the return rate, which is considered to be related to the service level of the retailer, as the function of the service level to extend the model in the reverse SC. The authors then analyze the optimal pricing and service decision under centralization and decentralization, respectively. Finally, with the revenue-sharing factor, wholesale price and recycling price transfer payment coefficient as contract parameters, the paper also designs a revenue-sharing contract led by the manufacturer and explores in what situation the contract could realize the Pareto optimization of all players. Findings In the baseline model, the results show that optimal price and service level correlate positively in centralization; however, the relation relies on consumers’ price sensitivity in decentralization. In the extension model, the relationship between price and service level also relies on the relative value of increased service cost and remanufacturing saved cost. When the return rate correlates with the service level, a recycling transfer payment can elevate the service level and thus raise the return rate. Through analyzing the parameters in revenue-sharing contract, a point can be reached where lowering the wholesale price and raising the transfer payment coefficient will promote retailers to share revenue. Practical implications Many enterprises establish the dual-channel distribution system both online and offline, which need to understand how to resolve their channel conflict. The conflict is especially strong in CLSC with remanufacturing. The result helps the node enterprises realize the coordination of the dual-channel CLSC. Originality/value It takes into account the fact that there are two complementary relationships, such as online selling and offline delivery; used product recycling and remanufacturing. The authors optimize the strategy of product pricing and service level in order to solve channel conflict and double marginalization in the closed-loop dual-channel distribution network.

scholarly journals Validating Virtual Safety Stock Effectiveness through Simulation

10.5772/56859 ◽  
2013 ◽  
Vol 5 ◽  
pp. 41 ◽  
Author(s):  
Maria Elena Nenni ◽  
Massimiliano M. Schiraldi
Keyword(s):  
Service Level ◽  
Inventory System ◽  
Time Interval ◽  
Common Condition ◽  
Simple Method ◽  
Safety Stock ◽  
Safety Stocks ◽  
Base Stock Policy ◽  
Stock Policy ◽  
Business To Business

As a means of avoiding stock-outs, safety stocks play an important role in achieving customer satisfaction and retention. However, traditional safety stock theory is based on the assumption of the immediate delivery of the ordered products, which is not a common condition in business-to-business contexts. Virtual safety stock theory was conceived to raise the service level by exploiting the potential time interval in the order-to-delivery process. Nevertheless, its mathematical complexity prevented this technique from being widely adopted in the industrial world. In this paper, we present a simple method to test virtual safety stock effectiveness through simulation in an inventory system using a base stock policy with periodic reviews and backorders. This approach can be useful for researchers as well as practitioners who want to model the behaviour of an inventory system under uncertain conditions and verify the opportunity for setting up a virtual safety stock on top of, or instead of, the traditional physical safety stock.

scholarly journals AVAILABILITY ASSESSMENT SIMULATIONS FOR ALLOCATING HUMAN RESOURCES IN AIRSPACE CONTROL CENTERS

2013 ◽  
Vol 4 (1) ◽  
pp. 61-76
Author(s):  
Walter Nogueira Pizzo
Keyword(s):  
Human Resources ◽  
Simulation Model ◽  
Control Systems ◽  
Computer Systems ◽  
Service Level ◽  
Point Of View ◽  
Operations And Maintenance ◽  
Human Operators ◽  
Availability Assessment

Airspace control systems introduced automation into functions previously performed by human operators. This situation increased the dependence on the availability of computer systems, in which degraded operation events can reduce the service level at any controlled airspace. This paper presents a relationship between availability and allocation of human resources in these centers, where maintenance and operations personnel are occasionally asked to repair losses caused by automated functions. A simulation model for the Arena tool is presented, to access availability, and then the operational point of view is explored, focusing on the required availability scenarios. The results presented herein can help determine the size of operations and maintenance teams, considering the reliability and maintainability parameters of airspace control systems.

scholarly journals A Transportation Performance Measurement System with a Mississippi Case Study

2010 ◽  
Author(s):  
Haiyuan Wang ◽  
Mingzhou Jin
Keyword(s):  
Performance Measures ◽  
Transportation Systems ◽  
System Level ◽  
Performance Measurement System ◽  
Intermodal Transportation ◽  
Design Alternatives ◽  
Level Performance ◽  
Existing Data ◽  
Highway System

In current literature and practices, there are no systematic and user-oriented intermodal transportation performance measures. After identifying customer needs and transportation goals, this paper proposes a set of system-level performance measures for intermodal transportation that are user-oriented, scalable, systematic, and scientific. The measures can be used to compare intermodal design alternatives or to evaluate existing transportation systems with any size and any mode. The highway system in Mississippi is analyzed as a case study. The case study demonstrates the existing data sources, the methods of calculating the measures, and the means of evaluating transportation systems with the measures.

Exploring incomplete information in maintenance materials inventory optimization

2014 ◽  
Vol 114 (1) ◽  
pp. 144-158 ◽  
Author(s):  
Antti Puurunen ◽  
Jukka Majava ◽  
Pekka Kess
Keyword(s):  
Sensitivity Analysis ◽  
Simulation Model ◽  
Input Data ◽  
Real Life ◽  
Significant Risk ◽  
Service Level ◽  
Content Type ◽  
Imperfect Data ◽  
Inventory Optimization ◽  
Critical Materials

Purpose – Ensuring the sufficient service level is essential for critical materials in industrial maintenance. This study aims to evaluate the use of statistically imperfect data in a stochastic simulation-based inventory optimization where items' failure characteristics are derived from historical consumption data, which represents a real-life situation in the implementation of such an optimization model. Design/methodology/approach – The risks of undesired shortages were evaluated through a service-level sensitivity analysis. The service levels were simulated within the error of margin of the key input variables by using StockOptim optimization software and real data from a Finnish steel mill. A random sample of 100 inventory items was selected. Findings – Service-level sensitivity is item specific, but, for many items, statistical imprecision in the input data causes significant uncertainty in the service level. On the other hand, some items seem to be more resistant to variations in the input data than others. Research limitations/implications – The case approach, with one simulation model, limits the generalization of the results. The possibility that the simulation model is not totally realistic exists, due to the model's normality assumptions. Practical implications – Margin of error in input data estimation causes a significant risk of not achieving the required service level. It is proposed that managers work to improve the preciseness of the data, while the sensitivity analysis against statistical uncertainty, and a correction mechanism if necessary, should be integrated into optimization models. Originality/value – The output limitations in the optimization, i.e. service level, are typically stated precisely, but the capabilities of the input data have not been addressed adequately. This study provides valuable insights into ensuring the availability of critical materials.

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