Inventory model for convertible item with deterioration

Abstract

In this article, we developed a model for a convertible item (or product) where initial form of the item converts into another product by consuming conversion cost and time both. After duration, it converts again into a new product of a different nature. It is a sequential-type conversion from initial into two other products over states. The demand pattern and deterioration rate differ at each converted state. An inventory model is developed for such a kind of sequential convertible item. Expressions for total cost and other related costs (as per states) are derived and optimal time to convert the product in different states are calculated under model assumptions. A numerical example is incorporated in support of the theoretical findings and it validates the strength of the model.     

Optimal payment time under permissible delay in payment for products with deterioration

A permissible credit period is usually allowed to a retailer to pay back the dues without paying any interest to the supplier. The retailer can pay the supplier either at the end of the credit period or later incurring interest charges on the unpaid balance for the overdue period. The retailer is expected to settle the account at a time before the end of the inventory cycle time because the payable interest rate is generally higher than the earned interest rate. A model for optimal cycle and payment times is developed here for a retailer in a deteriorating-item inventory situation where a supplier allows a specified credit period to the retailer for payment without penalty. Under these conditions, this supplier-and-retailer system is modelled as a cost minimization problem to determine the optimal payment time under various system parameters. An iterative search procedure is applied to solve the problem, and the overall findings indicate that the retailer always has an option to pay after the permissible credit period depending on unit purchase and selling price, the deterioration rate of the products and the interest rate.     

An optimal replenishment model for inventory items with normally distributed deterioration

This paper deals with the inventory replenishment problem for deteriorating items with normally distributed shelf life, continuous time-varying demand, and shortages under the inflationary and time discounting environment. The reasons of choosing normal are twofold: it is one of the most important probability phenomena in the real world due to the classical central limit theorem, and it is also one of the most commonly used lifetime distributions in reliability contexts. The problem is formulated as a dynamic programming model and solved by numerical search techniques. The solutions of the model determine the optimal replenishment schedule over a finite planning horizon so that the present worth of the future costs associated with the system is minimized. In the extensive experiments, we validate the model, demonstrate the optimal replenishment schedule and lot-size, and carry out a comparative study to ascertain its contribution. In addition, sensitivity analysis was provided to help identify the most crucial factors that affect system performance. The experimental result shows that the deteriorating problem solved by an appropriate model (i.e. the proposed normal model) can save the total cost up to 2% approximately. It also identifies that the magnitudes of purchase cost per unit and demand rate are the most significant parameters that affect the replenishment decisions and cost.     

A quick response production strategy to market demand

The reason for considering the quick response production strategy to market demand is due to the rapid technology change, which results in decreasing market price and obsolescence. This study considers a production strategy of locating final production line in response to the changes in market demand and the continuous deterioration in stock. The demand rate is assumed to decrease exponentially with time while the price is assumed to decrease linearly with time. The purpose of this study is to derive the most economical site of final-production line that assembles products with short life cycle. The model considered in this research takes into account the sales revenue, the deteriorating cost, the carrying cost, the variable cost and the fixed cost of production. Although there is a higher labour and material cost when the production site is located near market point, the total profit increases due to quicker responsive time, smaller import tax, lower inventory and lesser deteriorating cost.     

Regulation and supervision of the European banking industry. Does one size fit all?

Post-global financial crisis (GFC) regulatory overhauls – where uniform solutions were adopted for various types of banks – have significantly changed the environment in which banks operate. This is especially visible in the European banking industry, whose profitability has not recovered to pre-GFC levels. Therefore, our goal is to investigate whether the determinants of bank profitability fit these uniform solutions. Accordingly, we explore the profitability of European banks in various settings from 2012 to 2016, which is the period marked by tough reforms. Since a decrease in profit may be treated as a sign of financial difficulties, we model static (i.e., loss) and dynamized (i.e., loss, moderate and severe decreases in profits) indicators of bank situations based on a sample of approximately 6700 bank-year observations. Different patterns of the determinants of profit decreases are found among different types and sizes of banks. Moreover, the determinants of loss events apparently differ from those accounting for profit decreases. These findings underline that a “one-size-fits-all” approach to regulation and supervision is not adequate for market realities.     

The generalized process manufacturing systems package

Process manufacturing systems should not be considered a simple variation to a discrete manufacturing control system. The change is often quite complex and generally it becomes easier to create a new package customized for the process manufacturer rather than try to change an existing M RP-based-discrete package. This article discusses why a discrete-to-process conversion can be an ineffective way to create a production control system. It describes the types of changes that will be necessary for process manufacturing systems.     

Joint pricing and ordering policy for a deteriorating inventory with partial backlogging

In this paper, a deterministic inventory model for deteriorating items with time-dependent backlogging rate is developed. The demand and deterioration rate are known, continuous, and differentiable function of price and time, respectively. Under these general assumptions, we first prove that the optimal replenishment schedule not only exists but is unique, for any given selling price. Next, we show that the total profit is a concave function of price when the replenishment schedule is given. We then provide a simple algorithm to find the optimal selling price and replenishment schedule for the proposed model. Finally, we use a numerical example to illustrate the algorithm.     

Joint Integrated Importance Measure for Multi-State Transition Systems

Joint reliability importance (JRI) evaluates the interaction of two components in contributing to the system reliability in a system. Traditional JRI measures mainly concern the change of the system reliability caused by the interactive change of the reliabilities of the two components and seldom consider the probability distributions, transition rates of the object component states, and system performance. This article extends the JRI concept of two components from multi-state systems to multi-state transition systems and mainly focuses on the joint integrated importance measure (JIIM) which considers the transition rates of component states. Firstly, the concept and physical meaning of JIIM in binary systems are described. Secondly, the JIIM for deterioration process (JIIMDP) and the JIIM for maintenance process (JIIMMP) in multi-state systems are studied respectively. The corresponding characteristics of JIIMDP and JIIMMP for series and parallel systems are also analyzed. Finally, an application to an offshore electrical power generation system is given to demonstrate the proposed JIIM.     

惨遭欲望围困的灵魂——《麦克白》和《琼斯皇》主题评析

采用平行分析的方法,从探讨剧作的文本和创作背景入手,对<麦克白>和<琼斯皇>主题的升华过程,即主人公惨遭欲望围困的心灵蜕变史进行了比较研究和深入剖析,求证两剧主题的同一性:它们都具有对人性警示的积极意义.     

A closed-loop supply chain for deteriorating products under stochastic container return times

This paper studies a two-stage supply chain where returnable transport items (RTIs) are used to ship finished products from the supplier to the buyer. Empty RTIs are collected at the buyer and returned to the supplier. The return time of RTIs is considered to be stochastic in this paper, and further finished products are assumed to deteriorate during potential delivery delays. First, the paper develops an analytical model of this supply chain, and then it discusses the properties of the model. Secondly, it presents the results of a simulation study in which the behaviour of the model is analysed. The results of our analysis indicate that the supply chain can influence both the risk of RTI stockouts at the supplier and the deterioration rate by changing the value of the return lot size of RTIs. Further, the results indicate that realising the optimal value for the RTI return lot size is especially important in case the mean return time of RTIs is short, while in case of a long RTI return lead time, an approximation of the optimal RTI return lot size is also acceptable.