scholarly journals Optimal Maintenance of a Production-inventory System With Continuous Repair Times and Idle Periods

2020 ◽  
Vol Volume 14 ◽  
Keyword(s):  
Preventive Maintenance ◽  
Average Cost ◽  
Inventory System ◽  
Control Limit ◽  
Raw Material ◽  
Production Unit ◽  
Numerical Examples ◽  
Long Run ◽  
Production Inventory ◽  
Production Inventory System

In this paper two similar models for the maintenance of a production-inventory system are considered. In both models, an input generating installation supplies a buffer with a raw material and a production unit pulls the raw material from the buffer. The installation in the first model and the production unit in the second model deteriorate stochastically over time and the problem of their optimal preventive maintenance is considered. In the first model, it is assumed that the installation, after the completion of its maintenance, remains idle until the buffer is evacuated, while in the second model, it is assumed that the production unit, after the completion of its maintenance, remains idle until the buffer is filled up. The preventive and corrective repair times of the installation in the first model and the preventive and corrective repair times of the production unit in the second model are continuous random variables with known probability density functions. Under a suitable cost structure, semi-Markov decision processes are considered for both models in order to find a policy that minimizes the long-run expected average cost per unit time. A great number of numerical examples provide strong evidence that, for each fixed buffer content, the average-cost optimal policy is of control-limit type in both models, i.e. it prescribes a preventive maintenance of the installation in the first model and a preventive maintenance of the production unit in the second model if and only if their degree of deterioration is greater than or equal to a critical level. Using the usual regenerative argument, the average cost of the optimal control-limit policy is computed exactly in both models. Four numerical examples are also presented in which the preventive and corrective repair times follow the Exponential, the Weibull, the Gamma and the Log-Normal distribution, respectively.

scholarly journals Optimal Maintenance of a Production System with Intermediate Buffers

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Constantinos C. Karamatsoukis ◽  
Epaminondas G. Kyriakidis
Keyword(s):  
Optimal Policy ◽  
Production System ◽  
Preventive Maintenance ◽  
Critical Level ◽  
Cost Structure ◽  
Raw Material ◽  
Production Unit ◽  
Production Inventory ◽  
Optimal Maintenance ◽  
Production Inventory System

We consider a production-inventory system that consists of an input-generating installation, a production unit andLintermediate buffers. It is assumed that the installation transfers the raw material to buffer and the production unit pulls the raw material from buffer We consider the problem of the optimal preventive maintenance of the installation if the installation deteriorates stochastically with usage and the production unit is always in operative condition. We also consider the problem of the optimal preventive maintenance of the production unit if the production unit deteriorates stochastically with usage and the installation is always in operative condition. Under a suitable cost structure and for given contents of the buffers, it is proved that the average-cost optimal policy for the first (second) problem initiates a preventive maintenance of the installation (production unit) if and only if the degree of deterioration of the installation (production unit) exceeds some critical level. Numerical results are presented for both problems.

scholarly journals A New Green Efficiency-Based Carbon Taxing Policy and Its Effects on a Production-Inventory System with Random Carbon Emissions and Green Investment

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Tapan Kumar Datta
Keyword(s):  
Carbon Tax ◽  
Profit Maximization ◽  
Inventory System ◽  
Environmental Benefits ◽  
Independent Random Variables ◽  
Model Parameters ◽  
Green Technologies ◽  
Numerical Examples ◽  
Production Inventory ◽  
Production Inventory System

In this study, the author proposes a new carbon taxing policy. This proposed carbon tax has two tax components. The first component is constant, and the second component depends on the green efficiency of production. The green efficiency of production is measured by the average amount of emissions per unit production in an assessment year. The green efficiency-based tax component can be reset every year. Lesser average emission rate indicates better green efficiency. The second component of this proposed carbon tax forces the firm to improve the green efficiency of production, which results in cleaner production. The author incorporates this new carbon tax policy in a production-inventory system with a price-sensitive demand rate. A rule is provided for the implementation of this new tax. Emissions during setup, production, and storage are considered as independent random variables. The firm has the opportunity of investing in green technologies to improve green efficiency. A profit maximization policy is adopted to solve the developed model. A solution algorithm is also provided. The model is illustrated by numerical examples with randomly generated model parameters. The results of numerical examples show the environmental benefits of the proposed carbon tax.

Modeling condition-based maintenance and replacement strategies for an imperfect production-inventory system

2016 ◽  
Vol 232 (10) ◽  
pp. 1858-1871 ◽  
Author(s):  
Guoqing Cheng ◽  
Binghai Zhou ◽  
Faqun Qi ◽  
Ling Li
Keyword(s):  
Product Quality ◽  
Preventive Maintenance ◽  
Inventory System ◽  
Single Type ◽  
Maintenance Cost ◽  
Total Cost ◽  
Penalty Cost ◽  
Imperfect Production ◽  
Production Inventory ◽  
Production Inventory System

In this article, we consider an imperfect production-inventory system which produces a single type of product to meet the constant demand. The system deteriorates stochastically with usage and the deterioration process is modeled by a non-stationary gamma process. The production process is imperfect which means that the system produces some non-conforming items and the product quality depends on the degradation level of the production system. To prevent the system from deteriorating worse and improve the product quality, preventive maintenance is performed when the level of the system degradation reaches a certain threshold. However, the preventive maintenance is imperfect which cannot restore the system as good as new. Hence, the aging system will be replaced by a new one after some production cycles. The preventive maintenance cost, the replacement cost, the production cost, the inventory holding cost and the penalty cost of lost sales are considered in this article. The objective is to minimize the total cost per unit item which depends on two decision variables: the preventive maintenance threshold and the time at which the system is replaced. We derive the explicit expression of the total cost per unit item and the optimal joint policy can be obtained numerically. An illustrative example and sensitivity analysis are given to demonstrate the proposed model.

scholarly journals The Optimization of a Virtual Dual Production-Inventory System under Dynamic Supply Disruption Risk

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Yu Chen ◽  
Liyuan Liu ◽  
Victor Shi ◽  
Yibin Zhang ◽  
Jing Zhu
Keyword(s):  
Raw Materials ◽  
Inventory System ◽  
Raw Material ◽  
Optimal Order ◽  
Inventory Level ◽  
Dual Sourcing ◽  
Production Inventory ◽  
Disruption Risk ◽  
Disruption Risks ◽  
Production Inventory System

Major events such as the COVID-19 pandemic, Olympic Games, and G20 Summit bring about supplier disruption risks and challenges to supply chain management. To help deal with these risks, a virtual dual-sourcing production-inventory system can be deployed. In this paper, we study such a system which consists of a raw material supplier, a manufacturer, and a virtual dual-sourcing contingency supplier. The manufacturer needs to determine the production, procurement, and inventory plan of raw materials. When its supplier is interrupted, the manufacturer may need to adjust the production and inventory plan and work with the contingency supplier. We develop a system dynamics method to simulate the operations in this production-inventory system to identify the approximately optimal order-up-to-level inventory policies. We find that the virtual dual production-inventory strategy can be the optimal contingency policy to deal with supplier dynamic disruption risks. Furthermore, for disruption risk with low frequency and long duration, the manufacturer should increase the safety inventory level before the disruption. Otherwise, it should increase the safety inventory level in every cycle.

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