optimal production lot with imperfect production process under permissible delay in payments and complete backlogging abstract the traditional economic production quantity epq model assumes that the production products are all perfect it is not always true in the real production system due to imperfect production process or other factors imperfect quality items may be produced furthermore it is well known that the total production inventory costs can be reduced by reworking the imperfect quality items produced with a relatively smaller additional reworking and holding costs in addition the permissible delay in payments offered by the supplier is widely adopted in the practical business market in this study we explore the effects of the reworking imperfect quality items and trade credit on the epq model with imperfect production processes and complete backlogging a mathematical model which includes the reworking and shortage costs interest earned and interest charged is presented besides an arithmetic geometric mean inequality approach is employed and an algorithm is developed to find the optimal production policy furthermore some numerical examples and sensitivity analysis are provided to demonstrate the proposed model

the optimal cycle time for epq inventory model under permissible delay in payments abstract goyal journal of the operational research society 36 1985 35 38 discusses the economic order quantity under conditions of permissible delay in payments an implicit assumption of goyal journal of the operational research society 36 1985 35 38 is that the items are obtained from an outside supplier the entire lot size is delivered at the same time if we wish to adopt all results obtained by goyal journal of the operational research society 36 1985 35 38 then we are effectively assuming that the replenishment rate is infinite the main purpose of this paper is to extend goyal journal of the operational research society 36 1985 35 38 to the case that the units are replenished at a finite rate when the replenishment rate approaches to infinite goyal journal of the operational research society 36 1985 35 38 will be a special case of this paper

exact accounting of inventory costs in stochastic periodic review models abstract most stochastic periodic review inventory models calculate inventory costs according to the inventory level at the end of the review cycle however in most cases actual inventory costs accrue at different time points over the course of the cycle suggesting that the outputs of these models might be suboptimal this work proposes a means of overcoming this deficiency by attributing inventory costs to their actual timing formulas are presented for the expected profit and for its corresponding optimality equation in various multi period models that follow complete or partial backlogging with or without spoilage stationary or varying inventory costs within cycle and immediate or postponed revenues we show that the optimality equation of all these model variants is a kind of newsvendor formula with modified demand distribution and cost parameters a simple approximation formula and bounds on the optimal order quantity which are based only on the demand distribution over the entire cycle are presented and combined together into an improved approximation formula numerical examples of a brownian motion demand process demonstrate the benefit of the proposed approximation in comparison to the simple approximation formula

review of inventory systems with deterioration since 2001 abstract this paper presents an up to date review of the advances made in the field of inventory control of perishable items deteriorating inventory the last extensive review on this topic dates back to 2001 goyal s k and giri b c recent trends in modeling of deteriorating inventory european journal of operational research 134 1 16 since then over two hundred articles on this subject have been published in the major journals on inventory control indicating the need for a new review we use the classification of goyal and giri based on shelf life characteristics and demand characteristics contributions are highlighted by discussing main system characteristics including price discounts backordering or lost sales single or multiple items one or two warehouses single or multi echelon average cost or discounted cash flow and payment delay

hyteresis in import prices the beachhead effect this paper shows that temporary real exchange rate fluctuations can have persistent hysteretic effects on trade specifically when market entry costs are sunk sufficiently large exchange rate shocks alter domestic market structure and thereby induce hysteresis this simple result has strong implications for exchange rate theory t rade policy and estimation of trade equations empirical evidence su ggests that the recent dollar overvaluation induced hysteresis in u s import prices namely the aggregate pass through equation of exchange rates to import prices shifted in the 1980s the shift s nature and timing is broadly consistent with the hysteresis hypothesis copyright 1988 by american economic association

an inventory model with deteriorating items under inflation when a delay in payment is permissible abstract this study develops an inventory model for initial stock dependent consumption rate when a delay in payment is permissible in the inventory model shortages are not allowed the effect of the inflation rate deterioration rate initial stock dependent consumption rate and delay in payment are discussed in the study mathematical models are also derived under two different circumstances i e case i the credit period is less than or equal to the cycle time for settling the account and case ii the credit period is greater than the cycle time for settling the account besides expressions for an inventory system s total cost are derived for these two cases moreover a computational procedure and gino lasdon et al acm transactions mathematical software 4 1978 34 50 are proposed to obtain the optimal order size and cycle time the results can help managers determine the optimal total cost finally a numerical example demonstrates the applicability of the proposed model

the optimal inventory policies under permissible delay in payments depending on the ordering quantity abstract this paper deals with the problem of determining the economic order quantity under conditions of permissible delay in payments the delay in payments depends on the quantity ordered when the order quantity is less than the quantity at which the delay in payments is permitted the payment for the item must be made immediately otherwise the fixed trade credit period is permitted the minimization of the total variable cost per unit of time is taken as the objective function an algorithm to determine the economic order quantity is developed the results obtained in this paper generalize some already published results

inventory ordering policies of delayed deteriorating items under permissible delay in payments abstract the existing literature on inventory of deteriorating items considers deterioration to begin as soon as the items are stocked however there are several deteriorating items that do not start deteriorating immediately they are held in stock some farm produce like potatoes yams and even some fruits and vegetables have this property depletion of these items as soon as they are stocked will depend on demand and when deterioration begins it will depend on both demand and deterioration in this paper we develop a mathematical model on the inventory of deteriorating items that do not start deteriorating immediately they are stocked the model also takes into cognizance the fact that in business activities nowadays customers are given some allowed period within which to settle for the goods supplied to them they can use the accrued money from sales of the supplied goods to earn interest within the allowed period they are charged interest only when they fail to settle the amount they owe the supplier at the end of the allowed period

optimal ordering and pricing policy for demand functions that are separable into price and inventory age abstract we formulate and analyze two models for determining the optimal pricing order quantity and replenishment period for items whose demand function is separable into components of price and inventory age the first model assumes a multiplicative demand function we provide conditions which are satisfied by most common price dependent demand functions to reduce the three variable profit maximization problem into a single variable problem which can be solved using an efficient line search method next we show that a genuine additive model cannot exist and instead suggest and analyze a pseudo additive model however this model is more limited than the multiplicative model in its ability to incorporate various combinations of price and inventory age effects and reduction of the maximization problem into a single variable problem is more complicated except in the case of a linear price effect which is further analyzed for both models we show that the optimal solution satisfies the first order condition for equilibrium under a monopoly with a modification that includes inventory holding costs we solve numerical examples to illustrate the solution procedures

a semi parametric panel data analysis on the urbanisation carbon emissions nexus for the mena countries abstract this study seeks to examine the impacts of urbanisation on carbon emissions through the investigation of the existence of an environmental kuznets curve ekc within the stochastic impacts by regression on population affluence and technology stirpat framework this is the first study in the mena region to explore the urbanisation and carbon emissions nexus using panel data together with a semi parametric panel fixed effects regression the data set refers to a panel of 20 countries in the mena region spanning the period 1980 2014 according to the results there is little evidence to support an inverted u shaped relationship between urbanisation and carbon emissions in the region more specifically it was found in the region and with the continuation of the urbanisation process carbon emissions per capita decreased in addition the results suggest that energy use and economic growth are the main sources of carbon emissions in the region the results imply that policies to reduce carbon emissions in the countries with relatively higher carbon emissions should concentrate more on energy use and the pattern of economic growth and not the urbanisation issue

production inventory models for a damageable item with variable demands and inventory costs in an imperfect production process in this paper economic production quantity epq models for breakable or deteriorating item are developed with variable demands being dependent on time or on hand stock here rate of production and holding cost are time dependent unit production cost is a function of both production reliability indicator and production rate set up cost is also partially production rate dependent the production process produces some imperfect quantities which are instantly reworked at a cost to bring back those units to the perfect ones the production process ultimately depends on both time and reliability indicator the models are formulated as optimal control problems and the total profit functions with effect of inflation and time value of money are expressed as finite integrals over the finite planning horizon the problems are solved using euler lagrange function based on variational calculus and newton raphson method to determine the optimal production reliability indicator r and then corresponding production rates and total profits in some cases results of the models for deteriorating item are obtained as particular cases from those of breakable item models similarly results of simple epq models without damageability are deduced as particular cases numerical experiments are performed to illustrate the models both numerically and graphically

international economic co operation books reviewed in this article ralph bryant dale henderson gerald holtham peter hooper steven symansky eds 1988 empirical macroeconomics for interdependent economies marcello de cecco and alberto giovannini eds 1989 a european central bank ralph bryant david currie jacob frenkel paul masson and richard portes eds 1989 macroeconomic policies in an interdependent world richard cooper barry eichengreen gerald holtham robert putnam and randall henning 1989 can nations agree

exchange rate pass through when market share matters the authors investigate the pass through from exchange rates to import prices when firms future demands depend on their current market shares they show that profit maximizing foreign firms may either raise or lower their dollar export prices when the dollar appreciates temporarily i e the pass through may be perverse and that current import prices may be more sensitive to expected future exchange rates than to current exchange rates they present evidence that suggests the behavior of expected future exchange rates may provide a clue to the puzzling recent behavior of u s import prices copyright 1989 by american economic association

optimal replenishment policies for non instantaneous deteriorating items with price and stock sensitive demand under permissible delay in payment abstract this study is motivated by the paper of chang et al international journal of production economics 123 2010 62 68 we extend their inventory model from two aspects 1 the demand rate as multivariate function of price and level of inventory 2 delay in payment is permissible under these assumptions we first formulated a mathematical model and then some useful theoretical results have been derived to characterize the optimal solutions for non zero and zero ending inventory system numerical examples are presented to illustrate the theoretical results the sensitivity analysis of a suitable example is performed and some managerial insights are proposed our analysis revels that it is more beneficial to keep higher inventory level hoping to stimulate more demand even if it results in non zero ending inventory

effects of discounting and demand rate variability on the eoq the economic order quantity eoq formula is probably the most well known formula in inventory theory it determines the optimal value of the ordering quantity by minimizing the average cost in an ordering cycle it is based on the assumptions that there is a fixed lead time and a constant demand rate these assumptions are usually not fulfilled in practice especially when dealing with slow moving items demand seems to fluctuate furthermore since the time between two successive orderings is often large for slow moving items discounted costs instead of average costs should be minimized in this paper we determine the optimal ordering quantity if demand is modelled by a poisson process and the expected discounted costs are minimized we also analyze the case where demand is uniform and or the average cost criterion is used we give graphical presentations of the optimal ordering quantities besides easily determining the optimal values these allow us to show what the effects of changing the objective function and of changing the demand distribution are we derive a simple discounted cost ordering quantity formula denoted by eoq d for slow moving items we show that for items with a small demand rate and high fixed ordering costs the eoq d is much closer to the optimal discounted cost ordering quantity than the traditional eoq formula c 1998 elsevier science b v all rights reserved

joint price and lot size determination under conditions of permissible delay in payments and quantity discounts for freight cost abstract this paper deals with the problem of determining the retailer s optimal price and lot size simultaneously under conditions of permissible delay in payments it is assumed that the ordering cost consists of a fixed set up cost and a freight cost where the freight cost has a quantity discount offered due to the economies of scale the constant price elasticity demand function is adopted which is a decreasing function of retail price investigation of the properties of an optimal solution allows us to develop an algorithm whose validity is illustrated through an example problem

optimal inventory policy for a perishable item with demand function sensitive to price and time abstract we formulate a model for determining the optimal pricing order quantity and replenishment period for perishable items with price dependent and time dependent demand the items have a fixed shelf life and the demand rate decreases linearly in the selling price and polynomially over the time after replenishment until it vanishes either at the reservation price or at expiration time we prove that the three variable profit maximization problem can be reduced into a single variable problem in which the variable is the duration of the replenishment period we show that the profit function is strictly pseudo concave and provide means of obtaining the optimal policy three numerical examples are presented to demonstrate the model accompanied by a sensitivity analysis

continuous review inventory model with delay in payments abstract in this paper we examine the continuous review inventory model under permissible delays in payments that is a retailer has the option of either paying for the goods immediately upon the receipt of the order or delay the payment till the next replenishment order where interest will be charged over the delay period expected demand will be assumed constant over time and the order lead time is considered random the objective is to find the optimal ordering quantity and reorder level that will maximize the vendor s total expected profit per unit time when payments are delayed

an inventory model for deteriorating items with shortages and time varying demand abstract a deterministic inventory system for items with a constant deterioration rate is studied demand varies in time and it is assumed that it follows a power pattern shortages are allowed and backlogged the ordering cost the holding cost the backlogging cost the deteriorating cost and the purchasing cost are considered in the inventory management an approach is proposed to minimize the total cost per inventory cycle this cost depends on two decision variables the time at which the inventory level falls to zero and the length of the scheduling period numerical examples illustrate the theoretical results