perishable inventory theory a review this paper reviews the relevant literature on the problem of determining suitable ordering policies for both fixed life perishable inventory and inventory subject to continuous exponential decay we consider both deterministic and stochastic demand for single and multiple products both optimal and sub optimal order policies are discussed in addition a brief review of the application of these models to blood bank management is included the review concludes with a discussion of some of the interesting open research questions in the area

optimal lot size model for deteriorating items with demand rate dependent on displayed stock level dsl and partial backordering in this paper we consider the problem of determining the lot size of a single deteriorating item with the demand rate dependent on displayed stock level selling price of an item and frequency of advertisement in the popular electronic and print media also through the sales representatives shortages if any are allowed and partially backlogged with a variable rate which depends on the duration of waiting time upto the arrival of next lot here the transportation cost for replenishing the goods is considered explicitly and the storage capacity of the showroom shop is assumed to be limited finite according to the relative size of the stock level dependency demand parameters and the storage capacity of the showroom shop different scenarios with sub scenarios have been mentioned and solved with the help of grg generalised reduced gradient method and the computational procedure the convexity analysis is done by showing the average profit function in each case as pseudo concave to illustrate the results and its significant features a numerical example is given finally to study the effect of changes of demand parameters deterioration backlogging parameters and mark up rate on the maximum initial stock level shortage level frequency of advertisement per cycle along with the maximum average profit are presented numerically

a deterministic inventory model for deteriorating items with stock dependent demand rate abstract a deterministic inventory model is developed by assuming that the demand rate is stock dependent and the items deteriorate at a constant rate the expression for the average net profit over one production run is derived and its optimization with respect to the decision variables q initial stock and t duration of a production cycle is carried out this leads to two highly nonlinear equations which are solved by using a subroutine neqnf in imsl math library in cyber 180 480a computer system the optimal solution so derived is compared with that for the no deterioration 0 case sensitivity of the optimal solution to changes in parameter values is examined several aspects of the functional form for the demand rate are considered in a separate section finally the salient features of the problem and its solution are discussed in brief

inventory policy with time dependent setup cost abstract assume a time interval t is given moreover assume that the setup cost is not constant but varies with the lapse of time our problem is to determine the inventory policy for the given t how often the order is placed during t and how much is ordered at each ordering time point are our main themes we solve these problems in the following ways if frequency of orders for t is given arbitrarily the ordering policy is to be planned by using the techniques of dp by choosing a proper frequency of orders so that it may minimize the total inventory cost required during t an optimal inventory policy for t is determined moreover by applying dp some mathematical properties of this policy are examined even if exact mathematical expressions for frequency of orders and inventory cost are determined their values are obtained these become the merit of applying dp

ethnicity neighborhoods and human capital externalities the socioeconomic performance of today s workers depends not only on parental skills but also on the average skills of the ethnic group in the parents generation or ethnic capital this paper investigates the link between the ethnic externality and ethnic neighborhoods the evidence indicates that residential segregation and the external effect of ethnicity are linked partly because ethnic capital summarizes the socioeconomic background of the neighborhood where the children were raised ethnicity has an external effect even among persons who grow up in the same neighborhood when children are exposed frequently to persons who share the same ethnic background copyright 1995 by american economic association

a note on eoq models for deteriorating items under stock dependent selling rate abstract in 1995 padmanabhan and vrat presented inventory models for deteriorating items with stock dependent selling rate and derived the profit functions without backlogging and with complete backlogging first this paper develops the necessary and sufficient conditions of the existence and uniqueness of the optimal solutions of the profit per unit time functions without backlogging and with complete backlogging second this paper explains that it is appropriate to use the newton raphson method to find the optimal solutions of the profit functions per unit time in both situations modelled

how do sex ratios affect marriage and labor markets evidence from america s second generation sex ratios i e relative numbers of men and women can affect marriage prospects labor force participation and other social and economic variables but the observed association between sex ratios and social and economic conditions may be confounded by omitted variables and reverse causality this paper uses variation in immigrant flows as a natural experiment to study the effect of sex ratios on the children and grandchildren of immigrants the flow of immigrants affected the second generation marriage market because second generation marriages were mostly endogamous i e to members of the same ethnic group the empirical results suggest that high sex ratios had a large positive effect on the likelihood of female marriage and a large negative effect on female labor force participation perhaps surprisingly the marriage rates of second generation men appear to be a slightly increasing function of immigrant sex ratios higher sex ratios also appear to have raised male earnings and the incomes of parents with young children the empirical results are broadly consistent with theories where higher sex ratios increase female bargaining power in the marriage market

optimal ordering and transfer policy for an inventory with stock dependent demand abstract this paper deals with an ordering transfer inventory model to determine the retailer s optimal order quantity and the number of transfers per order from the warehouse to the display area it is assumed that the amount of display space is limited and the demand rate depends on the display stock level the objective is to maximize the average profit per unit time yielded by the retailer the proposed models and algorithms are developed to find the optimal strategy by retailer numerical examples are presented to illustrate the models developed and the sensitivity analysis is also reported

an eoq model with stock dependent demand shortage inflation and time discounting abstract this paper develops a finite time horizon deterministic economic order quantity eoq inventory model with shortages where the demand rate at any instant depends on the on hand inventory stock level at that instant the effects of inflation and the time value of money are taken into account considering two separate inflation rates namely the internal company inflation rate and the external general economy inflation rate the results are discussed with a numerical example and particular case of the model is discussed in brief a sensitivity analysis of the optimal solution with respect to the parameters of the system is carried out

inventory model with stock level dependent demand rate and variable holding cost inventory models in which the demand rate depends on the inventory level are based on the common real life observation that greater product availability tends to stimulate more sales previous models incorporating inventory level dependent demand rate assume that the holding cost is constant for the entire inventory cycle this paper considers the inventory policy for an item with a stock level dependent demand rate and a storage time dependent holding cost the holding cost per unit of the item per unit time is assumed to be an increasing function of the time spent in storage two time dependent holding cost step functions are considered retroactive holding cost increase and incremental holding cost increase procedures are developed for determining the optimal order quantity and the optimal cycle time for both cost structures

an inventory model for deteriorating items with stock dependent consumption rate and shortages under inflation and time discounting this paper derives an inventory model for deteriorating items with stock dependent consumption rate and shortages under inflation and time discounting over a finite planning horizon we show that the total cost function is convex with the convexity a simple solution algorithm is presented to determine the optimal order quantity and the optimal interval of the total cost function the results are discussed with a numerical example and particular cases of the model are discussed in brief a sensitivity analysis of the optimal solution with respect to the parameters of the system is carried out

a hybrid algorithm for simultaneous scheduling of production and distribution in multi echelon structures this paper presents a dynamic programming algorithm for simultaneous determination of production batch sizes in an assembly network and distribution batch sizes in a conjoined distribution arborescent network the objective is to minimize average cost per period over an infinite horizon costs consist of processing costs at each node and linear holding costs for inventory final product demand rates may vary among the retail nodes but at each retail node the demand rate is assumed to be known constant and continuous all demand must be met backorders are not permitted the model can be used for a single product or for several products that are temporarily combined for distribution or for scheduling production in a system where several end products are produced from the same intermediate product as in some biochemical manufacturing processes

more on the inflation tax and the value of equity a cash in advance macro model is presented in which dividends are distributed at the end of each p eriod but where all other money receipts may be spent immediately on output and labor markets if money grows at a constant rate only th e real price of equity will be inversely related to inflation in the steady state if the money supply is allowed to grow at an increasing rate however agent welfare will decline

anticipated inflation and the stock market the relation between fully anticipated inflation and stock prices is analysed in this paper the stock market is modelled within the construct of a choice theoretic intertemporal general equilibrium model where transactions are subject to a cash in advance constraint here a rise of the steady state inflation rate is shown to have a depressing effect on the stock market there are two reasons for this result first the consumption goods value of a given stream of dividends is reduced when inflation rises because the latter acts as a specific tax on dividends and secondly the firm s profits are lowered because the inflation rate distorts the labour leisure choice inflation anticipee et marche boursier l auteur analyse la relation entre l inflation pleinement anticip6e et le prix des actions en bourse a l int6rieur d un modele d 6quilibre g6n6ral de choix inter temporel on insere un march6 boursier dans lequel les transactions doivent etre r6gl6es comptant d avance on voit qu un accroissement du taux d inflation en regime permanent a un effet d6pressif sur le march6 boursier cela tient a deux raisons d abord quand l inflation monte la valeur en termes de biens de consommation d un flux donn6 de dividendes est r6duite parce que l inflation agit comme taxe sp6cifique sur les dividendes ensuite les profits de l entreprise sont r6duits parce que le taux d inflation introduit une distorsion dans la choix entre travail et loisir

inventory models with inventory level dependent demand a comprehensive review and unifying theory marketing researchers and practitioners have long recognized the demand of many retail items is proportional to the amount of inventory displayed recently two distinct types of inventory control models reflecting this relationship have appeared in the literature models in which the demand rate of an item is a function of the initial inventory level and those in which it is dependent on the instantaneous inventory level we present a comprehensive overview of this literature and demonstrate the equivalence of the two types of models through the use of a simple periodic review model an alternative approach to sensitivity analysis for inventory models with inventory level dependent demand is also presented

the economic lot sizing problem with perishable items and consumption order preference abstract we consider the economic lot sizing problem with perishable items els pi where each item has a deterministic expiration date although all items in stock are equivalent regardless of procurement or expiration date we allow for an allocation mechanism that defines an order in which the items are allocated to the consumers in particular we consider the following allocation mechanisms first expiration first out fefo last expiration first out lefo first in first out fifo and last in first out lifo we show that the els pi can be solved in polynomial time under all four allocation mechanisms in case of no procurement capacities this result still holds in case of time invariant procurement capacities under the fifo and lefo allocation mechanisms but the problem becomes np hard under the fefo and lifo allocation mechanisms

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

intermarriage and the economic assimilation of immigrants this article investigates the assimilation role of intermarriage between immigrants and natives intermarried immigrants earn significantly higher incomes than endogamously married immigrants even after we take account of human capital endowments and endogeneity of intermarriage the premium does not appear to be a reward for unobservable individual characteristics natives who intermarry do not receive this premium nor do immigrants who intermarry into another ethnic group the premium is mainly attributable to a faster speed of assimilation rather than any difference in labor market quality between intermarried and nonintermarried immigrants at the point of arrival

a production inventory model in an imperfect production process abstract the paper develops a model to determine the optimal product reliability and production rate that achieves the biggest total integrated profit for an imperfect manufacturing process the basic assumption of the classical economic manufacturing quantity emq model is that all manufacturing items are of perfect quality the assumption is not true in practice most of the production system produces perfect and imperfect quality items in some cases the imperfect quality non conforming items are reworked at a cost to restore its quality to the original one rework cost may be reduced by improvements in product reliability i e decreasing in product reliability parameter lower value of product reliability parameter results in increase development cost of production and also smaller quantity of nonconforming products the unit production cost is a function of product reliability parameter and production rate as a result higher development cost increases unit production cost the problem of optimal planning work and rework processes belongs to the broad field of production inventory model which deals with all kinds of reuse processes in supply chains these processes aim to recover defective product items in such a way that they meet the quality level of good item the benefits from imperfect quality items are regaining the material and value added on defective items and improving the environment protection in this point of view a model is introduced here to guide a firm industry in addressing variable product reliability factor variable unit production cost and dynamic production rate for time varying demand the paper provides an optimal control formulation of the problem and develops necessary and sufficient conditions for optimality of the dynamic variables in this purpose the euler lagrange method is used to obtain optimal solutions for product reliability parameter and dynamic production rate finally numerical examples are given to illustrate the proposed model

an inventory model for deteriorating items with stock dependent demand rate abstract this paper discusses an inventory model with an inventory level dependent demand rate followed by a constant demand rate for items deteriorating at a constant rate where the terminal condition of zero inventory at the end of the scheduling period has been relaxed sensitivity of the decision variables to changes in the parameter values is examined and the effects of these changes on the optimal policy are discussed in brief

integrating deterioration and lifetime constraints in production and supply chain planning a survey abstract items with short lifetimes that are subject to deterioration are important in the business world research has a long tradition in integrating deterioration and value loss effects into mathematical models for inventory planning and control where such effects are understood as a general loss or shrinkage of inventory however there has been little work in the modeling of lifetime restrictions of items to prevent wastage and disposals especially in a dynamic planning context globalization and other trends extend the consideration of single companies to whole supply chains implying increased coordination and information needs this is important as planning decisions impact lead times and thus the quality of items in the whole supply chain products that exceed their useful lifetime can impose high costs due to inventory loss or the need to rework them this implies increased utilization of scarce resources e g machine time metals and or energy thereby increasing co 2 levels we survey the state of the art regarding depreciation effects and the modeling of lifetime constraints as well as a classification of models following business planning functions of the value chain a critical evaluation of approaches and their limitations is provided highlighting directions for future research

an inventory model with both stock dependent demand rate and stock dependent holding cost rate abstract in this paper we develop an inventory model under a stock dependent demand rate and stock dependent holding cost rate with relaxed terminal conditions shortages are allowed and partially backlogged in the model the purpose of this study is to determine the optimal order quantity and the ending inventory level such that the total profit per unit time is maximized for the retailer we first establish a proper model for a mathematical formulation then we develop several theoretical results and provide the decision maker with an algorithm to determine the optimal solution finally numerical examples are provided to illustrate the solution procedure and a sensitivity analysis of the optimal solution with respect to major parameters is carried out

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

joint pricing and inventory control for fresh produce and foods with quality and physical quantity deteriorating simultaneously abstract a great number of models have been proposed to investigate the deterioration inventory however most of models assume that a fixed physical quantity of items deteriorates over time the quality of items does not decay before their expiration dates in practice the quality and physical quantity of many products including fresh produce and foods often deteriorate over time the quality of an item usually plays an important role in influencing the demand for products in this paper we consider the pricing and lot sizing problem for products with quality and physical quantity deteriorating simultaneously the deterioration rate of quality and physical quantity is taken to be time proportional the demand rate is assumed to be deterministic and dependent on the quality of an item the selling price per unit and the on display stock level the theory for finding the optimal solution of problem is discussed and numerical examples are used to illustrate the model and the solution procedure finally sensitivity analysis of the optimal solution with respect to price sensitive parameter and values of different deterioration functions is carried out

the intergenerational mobility of immigrants this article analyzes the intergenerational mobility of immigrants using the 1940 70 censuses the study reveals an important link between the earnings of immigrants and the earnings of their american born children although there is some regression toward the mean the earnings of second generation americans are strongly affected by variables describing economic conditions in the source countries of their parents current immigration policy therefore not only determines how immigrants perform in the labor market but also determines tomorrow s differences in the labor market experiences of american born ethnic groups

intermarriage and the labor market outcomes of asian women the impact of intermarriage with natives on labor market outcomes of immigrants is not homogeneous across ethnic groups wages of asian women are compared with non asians both ordinary least squares and instrumental variables estimates of the effects of intermarriage on the wages of asian women are negative and significant non asian women earn a wage premium that becomes insignificant when controls for selection into marriage are introduced one possible explanation for the intermarriage penalty for asians is an income effect of having a high earning native husband intermarriage penalties rise with husband s education assimilation patterns of intermarried asians indicate that they have lower initial wages market hours and employment but exhibit faster rates of growth over their years of stay the results are robust across asian subgroups and husband s ethnicity jel j16 j12 j31 j61

assimilation across the latino generations there is concern that hispanics have not mimicked the european immigrant experience of great generational advance jeffrey grogger and stephen trejo 2002 reasons for concern vary but a theme is that latino immigrants and their offspring are less committed to assimilation than europeans were discrimination adherence to spanish and frequent trips home due to proximity are said to be reasons i examine two aspects of generational mobility of hispanic and mexican men education and wages a major problem in studying this assimilation is ambiguity in defining generations and ethnicity across census and current population survey cps files generations are defined as follows 1st generation born outside the united states 2nd generation at least one parent born outside the united states 3rd generation or more both parents born in the united states while reference is made for convenience to the 3rd generation it includes all generations beyond the second since no distinction was made between the 2nd and subsequent generations in the 1980 and 1990 censuses or the march cps s until 1994 i use data from four decennial censuses between 1940 and 1970 four special cps supplements on language and immigration 1979 1983 1986 1988 to cover the 1980 s and four successive march cps s starting in 1994 to represent the 1990 s ethnicity is straightforward to define for the 1st and 2nd generation where place or birth or self reported ethnicity can be used to define hispanic ethnicity the problem is the 3rd generation where information available for hispanic descent and specific ethnicity differs across the censuses and cps s details of the rules adopted to define specific hispanic ethnicity are available in smith 2001

impact of trade credit and inflation on retailer s ordering policies for non instantaneous deteriorating items in a two warehouse environment with the advent of better technologies in manufacturing and retail industry consumer beliefs and needs have been altered supermarkets are expected to sell fresh products in good conditions which have a longer shelf life or do not begin to deteriorate immediately termed known as non instantaneous deteriorating items this characteristic is now usually observed in almost all food stuffs fashionable items electronic products among others in order to sustain in the retail sectors the managers are moving forward to store these items in warehouses moreover due to increasing competition in business world supplier offers a permissible delay in payments to retailer in order to increase demand this encourages the retailer to order a large quantity which in turn entitles the organization to rent out an additional storage space considering the importance of such a scenario the present research work develops a two warehouse inventory model for non instantaneous deteriorating items with permissible delay in payments under inflationary conditions shortages are allowed and partially backlogged since customers willingness to wait decreases over time the objective of this paper is to determine the retailer s optimal replenishment policies that maximize the present worth of total optimal profit per unit time finally the proposed inventory model has been validated with the help of numerical example sensitivity analysis of the optimal solution with respect to key parameters of the inventory system has been also presented which provides important managerial implications

the timing of markets and monetary transfers in cash in advance economies in cash in advance models do the timing of markets and the timing of the monetary transfer affect equilibrium money demand the timing of markets generates different individual money demands however under the common assumption that agents are identical these differences do not affect the behavior of equilibrium real balances in contrast the timing of the monetary transfer has important implications for agent s information sets these implications can influence the equilibrium characteristics of real balances

a generalization of sensitivity of the inventory model with partial backorders abstract in this paper we use the elementary techniques of differential calculus to investigate the sensitivity analysis of montgomery et al s montgomery d c bazaraa m s keswani a k 1973 inventory models with a mixture of backorders and lost sales naval research logistics quarterly 20 225 263 inventory model with a mixture of backorders and lost sales and generalize chu and chung s chu p chung k j 2004 the sensitivity of the inventory model with partial backorders european journal of operational research 152 289 295 sensitivity analysis we provide three numerical examples to demonstrate our findings and remark the interpretation of the global minimum of the average annual cost at which the complete backordering occurs

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

joint pricing and inventory control for non instantaneous deteriorating items with partial backlogging and time and price dependent demand abstract in this paper a joint pricing and inventory control for non instantaneous deteriorating items is developed we adopt a price and time dependent demand function shortages is allowed and partially backlogged the major objective is to determine the optimal selling price the optimal replenishment schedule and the optimal order quantity simultaneously such that the total profit is maximized we first show that for any given selling price optimal replenishment schedule exists and unique then we show that the total profit is a concave function of price next we present a simple algorithm to find the optimal solution finally we solve a numerical example to illustrate the solution procedure and the algorithm

an inventory model for deteriorating items with time proportional demand and shortages under inflation and time discounting this paper proposes a generalized dynamic programming model for inventory items with weibull distributed deterioration in this model the demand rate is assumed to be time proportional shortages are allowed and completely backordered and the effects of inflation and time value of money are taken into consideration the solutions of the model determine the optimal replenishment schedule over a finite planning horizon so that the present worth of total cost associated with the inventory system is minimized the proposed model permits variation in both the replenishment intervals and the service levels between order cycles as a result it generates a better solution than other optimization models having fixed order intervals and or fixed service levels the solution procedure is illustrated by two numerical examples and comparison with an existing model is carried out

98 effective integer ratio lot sizing for one warehouse multi retailer systems a warehouse supplies n retailers constant external demand occurs at each retailer and shortages are not allowed there are linear holding costs and fixed costs for ordering at the warehouse and at each retailer the goal is to minimize the long run average cost over an infinite time horizon we define a new class of policies for this problem whose simple structure facilitates both computation and implementation the cost of a policy that is optimal within this class is shown to be within 2 of the cost of an optimal policy for the original problem in the worst case such a policy can be computed in on log n time

anticipated monetary policy in a cash in advance economy this paper analyses the effects of perfectly foreseen monetary policy within the framework of a standard cash in advance economy anticipated monetary policy is shown to have real effects by influencing inflationary expectations in a cash in advance economy an increase in the anticipated rate of inflation reduces the return to labour supply and induces a substitution away from time spent in the labour market the paper analyses the implication of this substitution for the time paths of output prices interest rates real and nominal and stock market prices

money and asset prices in a cash in advance economy an asset pricing model with money introduced via a cash in advance constraint is presented the monetary velocity is variable hence money demand does not obey the trivial quantity equation the effects of disturbances in output and money growth on real balances the price level and interest rates are examined monetary policy has effects on real asset prices the fisher relation and the premium on nominal bonds are discussed the precise role of the timing of information and transactions for properties of price levels and interest rates are clarified

an integrated production inventory model for deteriorating items with consideration of optimal production rate and deterioration during delivery abstract most of the literature of single vendor single buyer integrated production inventory models for deteriorating items assumed a fixed production rate little attention has been paid to finding the optimal production rate for minimizing the total system cost this paper investigates how production rate affects the total system cost and develops a solution procedure for finding the optimal production rate for the traditional models based on the findings this paper proposes an integrated single vendor single buyer model of an exponentially deteriorating item in which non stop production is considered and production rate is included as one of the decision variables it has been shown with numerical examples that the proposed model can provide a lower cost solution than the traditional models which assume a fixed production rate the proposed model also considers deterioration during deliveries which is usually neglected in the literature of inventory models of deteriorating items furthermore the proposed model is extended to relax the constant cost parameter assumption which is prevalent even in non constant production rate models and optimize the cost for a system in which some of the cost parameters are production rate dependent

an inventory model with deteriorating items quantity discount pricing and time dependent partial backlogging abstract wee international journal of production economics 59 1999 511 in his interesting paper presented a deterministic inventory model with the following characteristics quantity discount schemes for the unit cost partial backlogging at a fixed rate deterioration of stock in time and demand rate being a linear function of the selling price in this article we generalize the work of wee 1999 more specifically we consider a model where the demand rate is a convex decreasing function of the selling price and the backlogging rate is a time dependent function which ensures that the rate of backlogged demand increases as the waiting time to the following replenishment point decreases

analysis of deteriorating inventory production systems using a linear quadratic regulator we consider an inventory production system where items deteriorate at a constant rate the objective is to develop an optimal production policy that minimizes the cost associated with inventory and production rate the inventory problem is first modeled as a linear optimal control problem then linear quadratic regulator lqr technique is applied to the control problem in order to determine the optimal production policy examples are solved for three different demand functions sensitivity analysis is then conducted to study the effect of changing the cost parameters on the objective function

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

ethnic enclaves and the economic success of immigrants evidence from a natural experiment recent immigrants tend to locate in ethnic enclaves within metropolitan areas the economic consequence of living in such enclaves is still an unresolved issue we use an immigrant policy initiative in sweden when government authorities distributed refugee immigrants across locales in a way that may be considered exogenous this policy initiative provides a unique natural experiment which allows us to estimate the causal effect on labor market outcomes of living in enclaves we find substantive evidence of sorting across locations when sorting is taken into account living in enclaves improves labor market outcomes for instance the earnings gain associated with a standard deviation increase in ethnic concentration is in the order of four to five percent

ethnic capital and intergenerational mobility this paper analyzes the extent to which ethnic skill differentials are transmitted across generations i assume that ethnicity acts as an externality in the human capital accumulation process the skills of the next generation depend on parental inputs and on the quality of the ethnic environment in which parents make their investments or ethnic capital the empirical evidence reveals that the skills of today s generation depend not only on the skills of their parents but also on the average skills of the ethnic group in the parent s generation

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

deterministic models of perishable inventory with stock dependent demand rate and nonlinear holding cost this paper deals with an extended eoq type inventory model for a perishable product where the demand rate is a function of the on hand inventory the traditional parameters of unit item cost and ordering cost are kept constant but the holding cost is treated as i a nonlinear function of the length of time for which the item is held in stock and ii a functional form of the amount of the on hand inventory the approximate optimal solution in both the cases are derived computational results are presented indicating the effects of nonlinearity in holding costs

a returns policy for distribution channel coordination of perishable items abstract this paper deals with a retailer s operating policies for a perishable product when he agrees with his supplier not to return the unsold product to his supplier provided that the supplier gives some discount on the wholesale price mathematical formulations are developed based on a periodic review inventory model under lifo and fifo issuing policies the demand rate is assumed to be a function of the retail price and instantaneous inventory level decision variables are the amount of supplier s price discount that the retailer can accept in return for adopting the no returns condition the retail price and order size also numerical examples are solved with tabu search algorithm for sensitivity analysis

an optimal replenishment policy for non instantaneous deteriorating items with stock dependent demand and partial backlogging abstract in this study we consider a problem of determining the optimal replenishment policy for non instantaneous deteriorating items with stock dependent demand in the model shortages are allowed and the backlogging rate is variable and dependent on the waiting time for the next replenishment the necessary and sufficient conditions of the existence and uniqueness of the optimal solution are shown as the special cases the results for the models with instantaneous or non instantaneous deterioration rate and with or without shortages are derived further we analytically identify the best circumstance among these special cases based on the minimum total relevant cost per unit time sensitivity analysis of the optimal solution with respect to major parameters is carried out finally four numerical examples are presented to demonstrate the developed model and the solution procedure

operations research in inventory management a review and critique the objectives of inventory management including the relevant related costs are examined in this paper a brief review of standard problems that have been effectively solved is presented however we point out that a serious gap exists between theory and practice in many organizations suggestions are made for bridging this gap finally a list is provided of a number of research problems whose implementable solution would have a major beneficial impact on the practice of inventory management

anticipated inflation and the capital stock in a cash in advance economy abstract an economy is constructed in which the steady state capital stock is inversely related to the rate of inflation as a result that is directly opposite the usual conclusion

tracking intergenerational progress for immigrant groups the problem of ethnic attrition in tracking the later generation descendants of immigrants measurement biases can arise from ethnic attrition e g us born individuals who do not self identify as mexican despite having ancestors who immigrated from mexico we present evidence that such ethnic attrition is sizeable and selective for the third generation populations of key hispanic and asian immigrant groups in addition our results suggest that ethnic attrition generates biases that vary across national origin groups in direction as well as magnitude and that correcting for these biases will raise the socioeconomic standing of the us born descendants of most hispanic immigrants relative to their asian counterparts

optimal production and shipment models for a single vendor single buyer integrated system abstract this paper develops a more general production inventory model for a single vendor single buyer integrated system unlike the hitherto existing production inventory models for the vendor buyer system the present model neither requires the buyer s unit holding cost greater than the vendor s nor assumes the structure of shipment policy secondly the model is extended to the situation with shortages permitted based on shortages being allowed to occur only for the buyer thirdly the paper also presents a corresponding production inventory model for a deteriorating item for the integrated system the solution procedures are provided for finding the optimal production and shipment policies and illustrated with numerical examples three significant insights are shown 1 no matter whether the buyer s unit holding cost is greater than the vendor s or not the present model always performs best in reducing the average total cost as compared to the hitherto existing models 2 if the buyer s unit holding cost is less than the vendor s the optimal shipment policy for the integrated system will only comprise shipments with successive shipment sizes increasing by a fixed factor it is different from that obtained by hill hill r m 1999 the optimal production and shipment policy for the single vendor single buyer integrated production inventory problem international journal of production research 37 2463 2475 for the opposite case 3 when designing a single vendor single buyer integrated system making the buyer s unit holding cost lower than the vendor s is more beneficial to the system if shortages are not permitted to occur otherwise it just reverses

an integrated production inventory model with imperfect production processes and weibull distribution deterioration under inflation abstract this study develops an integrated production and inventory model from the perspectives of both the manufacturer and the retailer the model assumes a varying rate of deterioration partial backordering inflation imperfect production processes and multiple deliveries the elapsed time until the production process shift is assumed to be arbitrarily distributed the discounted cash flow and classical optimization technique are used to derive the optimal solution a numerical example including the sensitivity analysis is given to validate the results of the production inventory model the integrated decision results in lower optimal joint cost compared with an independent decision by the manufacturer and the retailer

perishable inventory management subject to stochastic leadtime abstract this paper discusses the model for a perishable product with the stochastic procurement leadtime zero or 1 unit leadtime is considered and its optimal ordering policy is derived this is a generalization of the one period horizon model of nahmias 4 further the chance constraint as for shortage is added and under this additional constraint again optimal ordering policy is obtained

an optimal production inventory model for deteriorating items with multiple market demand the global markets of today offer more selling opportunities to the deteriorating items manufacturers but also pose new challenges in production and inventory planning from a production management standpoint opportunities to exploit the difference in the timing of the selling season between geographically dispersed markets for deteriorating items are important to improving a firm s profitability in this paper we examined the above issue with an insightful production inventory model of a deteriorating items manufacturer selling goods to multiple markets with different selling seasons we also provided a solution procedure to find the optimal replenishment schedule for raw materials and the optimal production plan for finished products a numerical example was then used to illustrate the model and the solution procedure finally sensitivity analysis of the optimal solution with respect to major parameters was carried out

an eoq model with state dependent demand rate we present an eoq type model in which the demand rate is a function of the inventory level the demand functions and holding cost functions considered are quite general in particular we focus on two types of demand rate functions a piecewise constant function and a family of exponential functions the paper includes analysis of the problem optimization and sensitivity analysis we also extend the model by adding randomness to the order sizes

eoq models for perishable items under stock dependent selling rate this paper presents inventory models for perishable items with stock dependent selling rate the selling rate is assumed to be a function of current inventory level and rate of deterioration is taken to be constant under instantaneous replenishment with zero lead time the model incorporates aspects such as complete partial and no backlogging eoq is determined for maximizing the total profit in each of the situations the models developed are illustrated through numerical examples and sensitivity analysis is reported

inventory models with the demand rate dependent on stock and shortage levels this paper investigates an inventory system in which the demand rate during stockout periods differs from that during the in stock period by a given amount the previous analysis conducted in this area formulated the model as a cost minimization model this type of formulation will intentionally try to decrease demand by increasing the stockout period in order to decrease costs this paper appropriately considers the model as a profit maximization model and develops a closed form solution the model is then further generalized to incorporate the effect of stock level dependent demand rates and considers initial stock dependent demand as well as instantaneous stock dependent demand rates

marriage markets and assortative mating with household public goods theoretical results and empirical implications this paper analyzes marriage market equilibria when the gains from marriage result from joint consumption of household public goods assuming transferable utility within marriage the paper proves that marriage markets will be characterized by positive assortative mating on wealth when spouses differ only in endowments and the gains to marriage result only from public goods when spouses differ in wages and household public goods are produced at home the results imply offsetting effects with public good economies creating an incentive for positive assortative mating on wages and gains from specialization creating an incentive for negative assortative mating on wages the results help explain the persistent lack of empirical support for becker s prediction of negative assortative mating on wages and have implications for empirical analysis of all joint living arrangement decisions

demand promotion by upgradation under stock dependent demand situation a model the idea of demand promotion by upgrading the existing system of the selling centre has been modelled in this article the consumption rate is assumed to be dependent on the stock level the problem has been reduced to a maximizing problem the algorithmic approach for solving this maximizing problem is also provided objective is to maximize the net profit over a prescribed time an increasing convex upgradation cost is considered exponential upgradation cost has been considered for the numerical examples

an optimal procurement policy for items with an inventory level dependent demand rate and fixed lifetime abstract this paper investigates an optimal procurement policy for items with an inventory level dependent demand rate and fixed lifetime the demand rate is assumed to be a function of current inventory level and each unit has its fixed expiry date so any units which remain unused by their expiry date are considered outdated and must be disposed of for the system presented a mathematical model and solution methodology were developed sensitivity of the decision variables to changes in the parameter values is examined and future research needs are discussed in brief

a two echelon inventory distribution system with power demand pattern and backorders abstract this paper addresses the implications of considering power demand pattern and backorders in the one warehouse n retailer problem specifically we assume that items at the retailers are withdrawn from the inventory following a power pattern the objective function consists of the sum of ordering holding and backordering costs at all installations this objective function depends on the class of inventory policies that we choose for the formulation of the problem in general obtaining the cost function is an arduous task since the average inventory at the warehouse could be difficult to determine however if we apply single cycle policies the computation of the total average cost becomes possible under these assumptions we show that the one warehouse n retailer system with power demand pattern and backorders can be formulated as a mixed non linear programming problem

human capital and interethnic marriage decisions common explanations for the generally negative relationship between education and ethnic endogamy include 1 education makes immigrants and their children better able to adapt to native culture thereby eliminating the need for a same ethnicity spouse and 2 education raises the likelihood of leaving ethnic enclaves thereby decreasing the probability of meeting potential same ethnicity spouses this paper considers a third option the role of assortative matching on education if education distributions differ by ethnicity then spouse searchers may trade similarities in ethnicity for similarities in education when choosing spouses u s census data on second generation immigrants provide strong support for the assortative matching mechanism

stack them high let em fly lot sizing policies when inventories stimulate demand in some retail contexts stocking large quantities of inventory may not only improve service levels but can also stimulate demand for products having demand rates that increase with inventory levels we analyze the effect of stocking decisions on firm profitability to develop managerial insights regarding the structure of the optimal inventory policy and to understand how this policy differs from traditional approaches when inventories stimulate demand iteratively applying the standard economic order quantity eoq model by setting the demand rate parameter equal to the observed average demand rate in prior cycles yields an equilibrium order quantity that is robust to demand parameter misestimation but is suboptimal the profit maximizing policy orders larger quantities and can replenish inventory even before on hand stock fully depletes using an extension of a standard inventory dependent demand model from the literature we first provide a convenient characterization of products that require early replenishment we demonstrate that the optimal cycle time is largely governed by the conventional trade off between ordering and holding costs whereas the reorder point relates to a promotions oriented cost benefit perspective we show that the optimal policy yields significantly higher profits than cost based inventory policies underscoring the importance of profit driven inventory management

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

an epq model of ramp type demand with weibull deterioration under inflation and finite horizon in crisp and fuzzy environment abstract this paper deals with an economic production model for deteriorating items with ramp type demand rate a single item is produced and the finite rate of production is proportional to the demand rate the deterioration rate of the item is taken as two parameter weibull s distribution we also have considered the effect of inflation when there is no shortage in the stock and the model is under finite time horizon the inventory model is solved under crisp and fuzzy environment to evaluate the optimum solution of the model in different cases we illustrate the model with an example by taking various number of replenishment we present sensitivity analysis to illustrate the example under crisp and fuzziness thus the objective of the paper is to find the optimal solution of production time so as to minimize the present value of total cost of the whole replenishment cycle and to check which environment crisp or fuzzy is desirable

a deterministic eoq model with delays in payments and price discount offers abstract it is the purpose of this paper to model the retailer s profit maximizing strategy when confronted with supplier s trade offer of credit and price discount on the purchase of merchandise generally retailers have to face many types of demands for different kinds of goods in real situation retailers have to correlate between the selling price and supplier s trade offer keeping in mind profit maximization strategy in the proposed model all increasing deterministic demands are discussed analytically numerically and graphically in the environment of permissible delay in payment and discount offer to the retailer

networks in the modern economy mexican migrants in the u s labor market this paper attempts to identify job networks among mexican migrants in the u s labor market the empirical analysis uses data on migration patterns and labor market outcomes based on a sample of individuals belonging to multiple origin communities in mexico over a long period of time each community s network is measured by the proportion of the sampled individuals who are located at the destination the united states in any year we verify that the same individual is more likely to be employed and to hold a higher paying nonagricultural job when his network is exogenously larger by including individual fixed effects in the employment and occupation regressions and by using rainfall in the origin community as an instrument for the size of the network at the destination

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

s 1 s policies for perishable inventory we consider s 1 s policies for a single item whose lifetime is fixed and known with certainty demands are generated by a stationary poisson process and there is a positive leadtime for replenishment we believe this study gives the only analysis for perishables with a positive order leadtime the analysis involves the derivation of the stationary distribution of the s dimensional stochastic process corresponding to the time elapsed since the last s orders were placed this distribution is then used to obtain an expression for the expected cost rate of operating the system in steady state as a function of s a computer program has been developed to compute optimal s values and expected annual costs we report a computation for a variety of system parameters which show some of the unusual features of the problem finally we show how this model can be used in the context of a problem of optimizing availability of operating equipment subject to scheduled maintenance as well as random failure

a production inventory model for a deteriorating item with trended demand and shortages abstract a production inventory model is developed for a deteriorating item over a finite planning horizon with a linear time varying demand finite production rate and shortages the resulting nonlinear constrained minimization problem is numerically solved by using the box complex algorithm the optimal number of production cycles that minimizes the average system cost is determined sensitivity analysis of the optimal solution is carried out

a survey of deterministic models for the eoq and epq with partial backordering models for the basic deterministic eoq or epq problem with partial backordering or backlogging make all the assumptions of the classic eoq or epq model with full backordering except that only a fraction of the demand during the stockout period is backordered in this survey we review deterministic models that have been developed over the past 40 years that address the basic models and extensions that add other considerations such as pricing perishable or deteriorating inventory time varying or stock dependent demand quantity discounts or multiple warehouses

is immigration enforcement shaping immigrant marriage patterns abstract this paper identifies intermarriage between non citizens and citizens as an important response mechanism to intensified immigration enforcement particularly among mexican non citizens exploiting the temporal and geographic variation in the implementation of interior immigration enforcement from 2005 to 2017 we find that a one standard deviation increase in enforcement raises mexican non citizens likelihood of marrying a u s citizen by 3 to 7 both police based and employment based enforcement contribute to this impact the analysis adds to a growing literature examining how immigrants respond to tightened enforcement and importantly sheds light on the recent growth of intermarriage among mexican immigrants

optimal replenishment policies for non instantaneous deteriorating items with stock dependent demand abstract wu et al 2006 an optimal replenishment policy for non instantaneous deteriorating items with stock dependent demand and partial backlogging international journal of production economics 101 369 384 established an inventory model for non instantaneous deteriorating items with stock dependent demand and obtained the optimal replenishment policy in this paper we first amend wu et al s model by changing the objective to maximizing the total profit secondly we set a maximum inventory level in the model to reflect the facts that most retail outlets have limited shelf space thirdly we relax the restriction of zero ending inventory when shortages are not desirable we then establish the theoretical results and provide an algorithm to find the optimal solution finally we present some numerical examples to illustrate the results

optimal dynamic pricing and replenishment cycle for non instantaneous deterioration items with inventory level dependent demand abstract this paper considers a problem of determining the optimal dynamic pricing strategy and replenishment cycle for non instantaneous deteriorating items where the consumer demand depends on the sales price and the quantity of the items displayed in the store for the given replenishment cycle we derive the optimal dynamic pricing strategy by applying pontryagin s maximum principle and then design an effective algorithm to obtain the optimal dynamic pricing strategy and replenishment cycle simultaneously numerical examples are provided to illustrate the effectiveness of the proposed methods and solution procedure furthermore sensitivity analysis of the key system parameters is carried out and some interesting managerial insights are presented