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

the effects of energy prices on agricultural groundwater extraction from the high plains aquifer we examine the effects of energy prices on groundwater extraction using an econometric model of a farmer s irrigation water pumping decision that accounts for both the intensive and extensive margins our results show that energy prices have an effect on both types of margins increasing energy prices would affect crop selection decisions crop acreage allocation decisions and farmers demand for water our estimated total marginal effect which sums the effects on the intensive and extensive margins suggests that a 1 per million btu increase in the energy price would decrease water extraction by an individual farmer by 5 89 acre feet per year a decrease of 3 6 percent of the average annual extraction rate our estimated elasticity of water extraction with respect to energy price is 0 26

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

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

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

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

multi factor performance measure model with an application to fortune 500 companies abstract the paper develops tools for reconciling diverse measures which characterize the financial performance of the fortune 500 companies the technology of data envelopment analysis dea is employed to determine a multi factor financial performance model which inherently recognizes tradeoffs among various financial measures this study offers an alternative perspective and characterization on the performance of the fortune 500 companies it is shown that the top ranked companies by revenue do not necessarily have top ranked performance viewed as being multidimensional only about 3 companies were operating on the best practice frontier substantial technical and scale inefficiencies are found decreasing returns to scale drs are uncovered among the relatively large revenue top ranked companies the study of congestion shows that a reduction in current levels of employees assets and equity may actually increase revenue and profit levels factor specific measures within the framework of multidimensional measure are developed to further study the performance of companies and industries the performance of best practice frontier companies is analyzed by constructing reference share measures which indicate the role each frontier company plays in evaluating non frontier companies finally the reliability of the best practice frontier is examined

replenishment and pricing policy for deteriorating items taking into account the time value of money abstract a deteriorating inventory model taking into account the time value of money is developed for a deterministic inventory system with price dependent demand this study applies the discounted cash flows dcf approach for problem analysis a heuristic approach is presented to derive the near optimal replenishment and pricing policy that tries to maximize the total net present value profit a numerical example is implemented to illustrate the theory

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

price elasticity of groundwater demand attenuation and amplification bias due to incomplete information measurement errors in both human and natural components of agricultural and environmental systems can be as much a source of estimation bias as omitted variables selfselection simultaneity and reverse causality nonetheless partly because of difficulties in obtaining data there is less literature on measurement error problems than on other endogeneity problems this article examines estimation bias in the price elasticity of groundwater consumption for irrigated agriculture on the intensive margin the price at issue is for the energy used in pumping and pressurizing water for delivery lacking the precise unit irrigation cost previous studies imputed irrigation costs we first consider groundwater irrigation costs and identify factors that can cause measurement errors in the process of imputation under incomplete information about the determinants of irrigation costs we follow this by systematically analyzing the potential bias caused by measurement errors using econometric theory along with monte carlo simulations where appropriate we then quantify actual measurement errors making use of a unique dataset in which energy and groundwater consumption data are matched for individual observations finally we compare regression results using exact irrigation costs as opposed to imputed ones we find evidence of substantial measurement errors resulting in attenuation and amplification bias in the price elasticity of irrigation water consumption on the intensive margin our results indicate that measurement errors in irrigation costs can lead to misleading policy implications related to water and energy pricing as a tool to conserve water we also show that estimating the energy price elasticity of groundwater use is not as straightforward as previously thought

some models for estimating technical and scale inefficiencies in data envelopment analysis in management contexts mathematical programming is usually used to evaluate a collection of possible alternative courses of action en route to selecting one which is best in this capacity mathematical programming serves as a planning aid to management data envelopment analysis reverses this role and employs mathematical programming to obtain ex post facto evaluations of the relative efficiency of management accomplishments however they may have been planned or executed mathematical programming is thereby extended for use as a tool for control and evaluation of past accomplishments as well as a tool to aid in planning future activities the ccr ratio form introduced by charnes cooper and rhodes as part of their data envelopment analysis approach comprehends both technical and scale inefficiencies via the optimal value of the ratio form as obtained directly from the data without requiring a priori specification of weights and or explicit delineation of assumed functional forms of relations between inputs and outputs a separation into technical and scale efficiencies is accomplished by the methods developed in this paper without altering the latter conditions for use of dea directly on observational data technical inefficiencies are identified with failures to achieve best possible output levels and or usage of excessive amounts of inputs methods for identifying and correcting the magnitudes of these inefficiencies as supplied in prior work are illustrated in the present paper a new separate variable is introduced which makes it possible to determine whether operations were conducted in regions of increasing constant or decreasing returns to scale in multiple input and multiple output situations the results are discussed and related not only to classical single output economics but also to more modern versions of economics which are identified with contestable market theories

on optimal two stage lot sizing and inventory batching policies abstract a recent paper considered the two stage lot sizing problem with finite production rates at both stages the problem was classified according to whether the production rate at the first stage is greater or less than that at the second stage whether the production batch size at the first stage is greater or less than that at the second stage and whether the transfer from the first stage to the second stage is continuous or in batches the objective of this note is to offer an alternative more direct and intuitive way to derive and present essentially similar results and also to extend the analysis by relaxing one of the assumptions

optimal ordering policy for stock dependent demand under progressive payment scheme abstract in this article a mathematical model is developed to formulate optimal ordering policies for retailer when demand is partially constant and partially dependent on the stock and the supplier offers progressive credit periods to settle the account the notion of progressive credit period is as follows if the retailer settles the outstanding amount by m the supplier does not charge any interest if the retailer pays after m but before second period n offered by the supplier then the supplier charges the retailer on the un paid balance at the rate ic 1 if the retailer settles the account after n then he will have to pay at interest rate ic 2 on the un paid balance ic 2 ic 1 the cost minimization is considered to be an objective function an algorithm is given to find the flow of optimal ordering policy a numerical illustration is given to study the effect of various parameters on ordering policy and total cost of an inventory system

measuring super efficiency in dea in the presence of infeasibility super efficiency data envelopment analysis dea model is obtained when a decision making unit dmu under evaluation is excluded from the reference set because of the possible infeasibility of super efficiency dea model the use of super efficiency dea model has been restricted to the situations where constant returns to scale crs are assumed it is shown that one of the input oriented and output oriented super efficiency dea models must be feasible for a any efficient dmu under evaluation if the variable returns to scale vrs frontier consists of increasing constant and decreasing returns to scale dmus we use both input and output oriented super efficiency models to fully characterize the super efficiency when super efficiency is used as an efficiency stability measure infeasibility means the highest super efficiency stability if super efficiency is interpreted as input saving or output surplus achieved by a specific efficient dmu infeasibility does not necessary mean the highest super efficiency

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

a bi objective weighted model for improving the discrimination power in mcdea lack of discrimination power and poor weight dispersion remain major issues in data envelopment analysis dea since the initial multiple criteria dea mcdea model developed in the late 1990s only goal programming approaches that is the gpdea ccr and gpdea bcc were introduced for solving the said problems in a multi objective framework we found gpdea models to be invalid and demonstrate that our proposed bi objective multiple criteria dea bio mcdea outperforms the gpdea models in the aspects of discrimination power and weight dispersion as well as requiring less computational codes an application of energy dependency among 25 european union member countries is further used to describe the efficacy of our approach

optimal strategy for the integrated vendor buyer inventory model this note is concerned with the integrated vendor buyer inventory model two different strategies have been proposed in the literature for the problem one where the delivery quantity to the buyer at each replenishment is identical and another strategy where at each delivery all the inventory available with the vendor is supplied to the buyer we show that there is no one strategy that obtains the best solution for all possible problem parameters we also present the results of a detailed numerical study that analyses the relative performance of the two strategies for various problem parameters

inflation and the optimal inventory replenishment schedule within a finite planning horizon abstract the subject of this paper is the problem of finding the optimal replenishment schedule for an inventory subject to time dependent demand and deterioration within a finite time planning horizon it is shown that taking inflation into account has a profound effect on the solution of the problem for instance there is a critical number of replenishment periods in excess of which the optimal schedule is characterized by the inclusion of token orders at the end of the planning horizon this and other conclusions obtained via a careful mathematical analysis of the problem rectify those of earlier studies

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

an eoq model for perishable items under stock dependent selling rate and time dependent partial backlogging in the present paper we extend padmanabhan and vrat s model by proposing a time proportional backlogging rate to make the theory more applicable in practice the existence and uniqueness of the solutions of the relevant systems are examined subsequently a numerical example is presented to illustrate the application of developed model

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

the single vendor single buyer integrated production inventory model with a generalised policy abstract this note considers a more general type of policy for the single vendor single buyer integrated production inventory model than has hitherto been presented based on successive shipments to the buyer within a single production batch increasing by a fixed factor

appropriative water rights and the efficient allocation of resources this paper investigates the allocative efficiency of the appropriative system of water rights within the context of a simplified model of a water using industry at a long run competitive equilibrium for the industry and with a prohibition on the transfer of water rights among firms it is shown that 1 senior appropriators claim and use more water than junior appropriators 2 senior appropriators bear less risk than junior appropriators 3 the allocation of water and diversion capacitie 6among firms is inefficient being dominated by an equal sharing among firms the equal sharing allocation which is pareto optimal when diversion capacities are supplied by a competitive leasing industry can be achieved under the appropriative system if there are competitive markets in water rights and in leases for the use of diversion capacities an application of the coase theorem

ranking efficient decision making units in data envelopment analysis based on reference frontier share abstract data envelopment analysis dea is a powerful technique for performance evaluation of decision making units dmus ranking efficient dmus based on a rational analysis is an issue that yet needs further research the impact of each efficient dmu in evaluation of inefficient dmus can be considered as additional information to discriminating among efficient dmus the concept of reference frontier share is introduced in which the share of each efficient dmu in construction of the reference frontier for evaluating inefficient dmus is considered for this purpose a model for measuring the reference frontier share of each efficient dmu associated with each inefficient one is proposed and then a total measure is provided based on which the ranking is made the new approach has the capability for ranking extreme and non extreme efficient dmus further it has no problem in dealing with negative data these facts are verified by theorems discussions and numerical examples

optimal time varying lot sizing models under inflationary conditions abstract this paper deals with the inventory replenishment problem over a fixed planning horizon for items with linearly time varying demand and under inflationary conditions we develop models and optimal solution procedures with and without shortages we do not put any restriction on the length of the replenishment cycles making the proposed methods the first optimal solution procedure for this problem using four examples we illustrate the proposed solution procedures and study the effect of changing the inflation and discount rates on the optimal replenishment schedules

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

adaptation to an irrigation water restriction imposed through local governance abstract we estimate how farmers adapted to a water restriction imposed through local governance the restriction imposed a uniform quota on water use with a 5 year allocation and allowed trading of the quota within the restricted area our analysis exploits unique micro level data on irrigated water use irrigated acreage and crops we use a difference in differences econometric strategy that also includes farmer time fixed effects to estimate the response to the restriction where we exploit water rights between 2 and 5 miles of the policy boundary as a control group results indicate that farmers reduced water use by 26 due to the policy with most of the response due to reductions in water use intensity on the same crops rather than through reductions in irrigated acreage or changes in crops the results imply that the short run welfare impact of the policy was smaller than a policy that reduces irrigated acreage

global sensitivity analysis in inventory management abstract this paper deals with the sensitivity analysis sa of inventory management models when uncertainty in the input parameters is given full consideration we make use of sobol function and variance decomposition method for determining the most influential parameters on the model output we first illustrate the method by means of an analytical example we provide the expression of the global importance of demand holding costs order costs of the harris economic order quantity eoq formula we then present the global sa of the inventory management model developed by luciano and peccati 1999 capital structure and inventory management the temporary sale problem international journal of production economics 59 169 178 for the economic order quantity estimation in the context of the temporary sale problem we show that by performing global sa in parallel to the modeling process an analyst derives insights not only on the eoq structure when its expression is not analytically known but also on the relevance of modeling choices as the inclusion of financing policies and special orders

non market valuation in integrated assessment modeling the benefits of water right retirement abstract the impact of resource management on natural capital value depends on processes that affect resource stocks over space and time we develop an integrated assessment modeling framework that links econometric estimates of non market benefits from a resource stock to a spatially explicit model of resource dynamics results from a dichotomous choice contingent valuation survey are used to estimate a marginal willingness to pay function for groundwater which has no market we use the model to measure the economic benefits to agricultural producers of a program that pays for water right retirement under the baseline scenario without water right retirement the benefits from groundwater stocks in the study region decline in value by 3 6 million over 15 years because of groundwater depletion water right retirement leads to groundwater benefits that are 0 55 million higher than in the baseline after 15 years but benefits vary greatly over space comparing this to an explicit program cost of 45 million suggests that other social benefits from groundwater stocks must exist to justify the program from a benefit cost perspective valuing the economic benefits from increasing natural capital stocks can inform policy and provide insight into the value of management in resource and environmental systems

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 net benefits of incentive based regulation a case study of environmental standard setting economists interested in environmental safety and health regulation have long argued that decentralized incentive based or ib policies are more efficient than centralized command and control or cac approaches see charles schultze 1977 for instance these arguments generally have been based on the assumption that ib policies will accomplish the same goals as their cac counterparts but at less cost to society however some of those touting ib policies have overlooked an important point environmental workplace or even productsafety standards typically take the form of maximum permissible concentrations of harmful substances so that compliance only requires that all monitoring points or samples register readings below these critical levels for this reason ib policies typically assign a shadow price of zero to improvements that exceed the standard s while more crude cac policies generally result in overcontrol beyond the standards if there is no value to this overcontrol cac policies will not improve at all on ib approaches and will indeed be more expensive if however reduced concentrations below the level of the standards bring with them further improvements in health or the environment cac approaches will produce greater benefits than ib approaches thus a fair comparison between the two necessitates that any additional benefits associated with cac policies be offset against the cost advantages enjoyed by their ib counterparts although this possibility has been recognized by others scott atkinson and t h tietenberg 1982 for instance it is little appreciated and its empirical significance has never been ascertained that is our purpose here we do so by developing data on the costs and benefits of controlling a common air pollutant total suspended particulates or tsp in baltimore by comparing the tsp levels likely under both ib and cac approaches we are able to estimate the marginal costs and benefits associated with a variety of alternative air quality standards which take the form of maximum permissible concentrations this in turn allows us to determine the net benefits arising from the two kinds of regimes in the next section we present a simple conceptual framework for our analysis section ii describes the estimation of the costs and benefits of our hypothesized air pollution controls in baltimore section iii presents our somewhat surprising findings and section iv discusses those findings and their potential significance for regulation in the real world

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

super efficiency dea in the presence of infeasibility it is well known that super efficiency data envelopment analysis dea approach can be infeasible under the condition of variable returns to scale vrs by extending of the work of chen 2005 the current study develops a two stage process for calculating super efficiency scores regardless whether the standard vrs super efficiency mode is feasible or not the proposed approach examines whether the standard vrs super efficiency dea model is infeasible when the model is feasible our approach yields super efficiency scores that are identical to those arising from the original model for efficient dmus that are infeasible under the super efficiency model our approach yields super efficiency scores that characterize input savings and or output surpluses the current study also shows that infeasibility may imply that an efficient dmu does not exhibit super efficiency in inputs or outputs when infeasibility occurs it can be necessary that i both inputs and outputs be decreased to reach the frontier formed by the remaining dmus under the input orientation and ii both inputs and outputs be increased to reach the frontier formed by the remaining dmus under the output orientation the newly developed approach is illustrated with numerical examples

eoq and inflation uncertainty abstract inflation uncertainty is introduced into a basic eoq model and its potential to make mischief is explored among other things it is shown that even when the expected rate of inflation is less than the marginal cost of capital the appropriate discount rate to use in computing a discounted expected total inventory cost will not necessarily be negative therefore the classic eoq square root formula may drastically underestimate the optimal lot size the results may be generalized to the more complex inventory models

oil field unitization contractual failure in the presence of imperfect information an empirical analysis of the impact of transaction costs on contracting shows that imperfect in formation can seriously limit the effectiveness of private contracting the case under study is the widespread failure of private crude oil producing firms to use us oil fields to reduce rent dissipation rent dissipation follows as multiple firms compete for migratory oil in common oil pools unitization is the obvious private contractual solution to rent dissipation the authors argue that despite large net gains from unitization imperfect information and information asymmetries among the negotiating parties regarding lease values prevents consensus on unit shares as a result contracts are often not completed or only fragmented units are completed 9 references 1 figure 4 tables

a century of evolution from harris s basic lot size model survey and research agenda abstract determining the economic lot size has always represented one of the most important issues in production planning this problem has long attracted the attention of researchers and several models have been developed to meet requirements at minimum cost in this paper we explore and discuss the evolution of these models during one hundred years of history starting from the basic model developed by harris in 1913 up to today following harris s work a number of researchers have devised extensions that incorporate additional considerations the evolution of eoq theory strongly reflects the development of industrial systems over the past century here we outline all the research areas faced in the past by conducting a holistic analysis of 219 selected journal papers and trying to give a comprehensive view of past work on the eoq problem finally a new research agenda is proposed and discussed

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

differential importance and comparative statics an application to inventory management abstract in this work we deal with the problem of establishing which parameters impact an inventory policy the most a new sensitivity measure is introduced by relating the differential importance d and the comparative statics cs techniques we discuss the properties of the new indicator and show that it shares the additivity property we provide the expression of for optimization models numerical results are offered for the sensitivity analysis of a recently introduced inventory management model

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

a one vendor multi buyer integrated inventory model abstract we consider a one vendor multi buyer integrated inventory model the vendor seeks to minimize his total annual cost subject to the maximum costs which buyers are prepared to incur in order to implement this model the vendor only needs to know buyer s annual demand and previous order frequency which can be inferred from buyer s past ordering behavior we find the optimal solution for the one vendor one buyer case and present a heuristic approach for the one vendor multi buyer case

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

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

dea cross efficiency evaluation based on pareto improvement abstract cross efficiency evaluation as an extension tool of data envelopment analysis dea has been widely applied in evaluating and ranking decision making units dmus unfortunately the cross efficiency scores generated may not be pareto optimal which has reduced the effectiveness of this method to solve this problem we propose a cross efficiency evaluation approach based on pareto improvement which contains two models pareto optimality estimation model and cross efficiency pareto improvement model and an algorithm the pareto optimality estimation model is used to estimate whether the given set of cross efficiency scores are pareto optimal solutions if these cross efficiency scores are not pareto optimal the pareto improvement model is then used to make cross efficiency pareto improvement for all the dmus in contrast to other cross efficiency approaches our approach always obtains a set of pareto optimal cross efficiencies under the predetermined weight selection principles for these dmus in addition if the proposed algorithm terminates at its step 3 the evaluation results generated by our approach unify self evaluation peer evaluation and common weight evaluation in dea cross efficiency evaluation specifically the self evaluated efficiency and the peer evaluated efficiency converge to the same common weight evaluated efficiency when the algorithm stops this will make the evaluation results more likely to be accepted by all the dmus

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

on optimal payment time for a retailer under permitted delay of payment by the wholesaler abstract jamal et al 2000 optimal payment time for a retailer under permitted delay of payment by the wholesaler international journal of production economics 66 59 66 study a wholesaler retailer supply chain where the retailer is given a permissible credit period to pay back the dues without paying any interest to the wholesaler the problem is modeled as a cost minimization problem with two decision variables the payment time p of the retailer and the length of the inventory cycle t while the model represents in general an interesting problem we show in this note that there are a number of nontrivial flaws contained in the development of their model and therefore the solution they derived is not correct we give the correct model and derive the corresponding optimal solution

economic order quantity models for ameliorating deteriorating items under inflation and time discounting the items that incur a gradual loss in quality or quantity over time while in inventory are usually called deteriorating items in reality there are some items whose value or utility or quantity increase with time and those items can be termed as ameliorating items in this paper an effort has been made to incorporate these two opposite physical characteristics of stored items into inventory model we develop models for ameliorating deteriorating items with time varying demand pattern over a finite planning horizon taking into account the effects of inflation and time value of money optimal solutions of the proposed models are derived and the effects of amelioration deterioration on the inventory replenishment policies are studied with the help of numerical examples

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

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

economic analysis of dynamic inventory models with non stationary costs and demand abstract with today s high rate of inflation observed in most world economies the accuracy of standard lot sizing models and their applicability to real inventory situations under inflationary conditions become questionable in this paper we have studied the effects of inflation and time value of money on the replenishment policies of items with time continuous non stationary demand over a finite planning horizon we have developed dynamic programming models for three commonly used replenishment policies in the inventory lot sizing literature with time varying demand and shortages in the case of linear time dependent demand we have performed a sensitivity analysis to investigate the impact of changing the system parameters on the present worth of the total cost of each of the three replenishment policies the results showed that the initial cycle length is virtually insensitive to the type of replenishment policy we have also extended the developed models to more practical inventory situations with exponentially deteriorating items and perishable products having fixed life time

effects of inflation and time value of money on an inventory model with linear time dependent demand rate and shortages abstract in the present paper an attempt has been made to investigate the effects of inflation and time value of money on an inventory model with linear time dependent demand rate shortages are allowed in this model the model developed in this article is a finite horizon t si policy inventory model to the best of the authors knowledge such type of inventory model has not been considered earlier a numerical example has also been given to illustrate the developed model

effects of inflation and time value of money on an inventory model with time dependent demand rate and shortages abstract in a recent paper datta and pal investigated the effects of inflation and time value of money on an inventory model with linearly increasing demand and finite shortage cost however their models are formulated under the assumption of equal inventory carrying time during each replenishment cycle in this paper we redevelop the models of datta and pal by relaxing this assumption and modifying their mathematical formulations our models can be applicable to both growing and declining markets with general continuous time dependent demand rates numerical examples are provided to illustrate the developed models

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

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

an eoq model with deteriorating items under inflation when supplier credits linked to order quantity abstract this study proposes an inventory model under a situation in which the supplier provides the purchaser a permissible delay of payments if the purchaser orders a large quantity shortages are not allowed and the effect of the inflation rate deterioration rate and delay in payment are discussed as well as a result in this paper we establish an eoq model for deteriorating items under inflation when the supplier offers a permissible delay to the purchaser if the order quantity is greater than or equal to a predetermined quantity we then characterize the optimal solution and provide an easy to use algorithm to find the optimal order quantity and replenishment time finally some numerical examples are given to illustrate the theoretical results and made the sensitivity analysis of parameters on the optimal solutions

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

multicrop production decisions in western irrigated agriculture the role of water price applying a model of the multioutput firm econometric results are reported for irrigated production in four multistate regions of the american west cross sectional microdata from the farm and ranch irrigation survey and limited dependent variable methods are used to estimate crop choice supply land allocation and water demand functions for field crops farm level water demand is decomposed into the sum of crop level water demands and crop level demands are further separated into an extensive margin land allocations and intensive margin short run water use response to water price measured as groundwater pumping cost occurs primarily at the extensive margin

retail replenishment models with display space elastic demand we study a single store multi product inventory problem in which product sales are a composite function of shelf space since sales tend to deplete the amount of product on display the effective shelf space assigned to the product diminishes with time unless replenishment occurs we consider the problem of optimal replenishment times under these conditions we assume a linear dependence of sales rate to effective shelf space in all our analysis we present exact and approximate solutions for the single product and multi product cases for the single product case we study the effect of space elasticity cross elasticity and empty space elasticity on the optimal replenishment period for the multi product case we present a computationally attractive method using matrix exponentials and develop error bounds for this method

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

institutional path dependence in climate adaptation coman s some unsettled problems of irrigation districts that emerged in the american west in the late nineteenth and early twentieth centuries in response to aridity to facilitate agricultural water delivery use and trade raise the transaction costs today of water markets these markets are vital for smooth reallocation of water to higher valued uses elsewhere in the economy and for flexible response to greater hydrological uncertainty this institutional path dependence illustrates how past arrangements to meet conditions of the time constrain contemporary economic opportunities they cannot be easily significantly modified or replaced ex post

effects of inflation and the time value of money on order quantity and allowable shortage abstract this paper investigates the effects of inflation and time value of money on the optimal ordering quantities and the maximum allowable shortage in a finite replenishment inventory system the present value of total cost incurred in this inventory system is developed first then an optimal order quantity and maximum allowable shortage are obtained by using a search procedure the effect of inflation and time value of money was investigated under given sets of values of inflation and discount rates this study shows that the optimal order quantity and maximum allowable shortage vary with the change in difference between inflation and time discount computational results indicate that this effect on the system becomes more significant with the increase of the difference between inflation rate and time discount rate