surplus disposal in world markets an application to egyptian cotton in many countries agricultural exports are managed directly by governments a frequent problem encountered by policy makers involves the accumulation of unwanted surpluses caused by domestic price support programs unforeseen declines in world demand or unexpected shifts in the domestic supply demand balance this paper examines the intertemporal use of the world markets as a means to eliminate these surpluses the analytical results follow directly from the theory of storage they are applied to an analysis of the egyptian els cotton market where stock levels in the early 1980s became about six times as large as normal carryout estimation results suggest that optimal disposal plans may frequently involve selling surplus stocks in a single year

trade taxes and debt repayment in sri lanka the purpose of this article is to estimate the cost of taxing the export import or domestic sectors of sri lanka for the purpose of reducing the national debt a simple gnp model is used to estimate the elasticities that characterise the three aggregate sectors and are used to simulate the effects of taxing for debt servicing the results show that a tax on the import sector generates the largest net savings on trade balance and that the savings from not importing can be substantial however for the period 1977 87 a 10 0 per cent tax on the import sector caused a decline in the growth of the economy by 3 0 per cent the burden of the tax falls heavily on the domestic sector in terms of lost production and increased unemployment

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

brand equity and vertical product line extent this paper addresses the question of how the vertical structure of a product line relates to brand equity does the presence of premium or high quality products in a product line enhance brand equity conversely does the presence of economy or low quality products in a product line diminish brand equity economists and marketing researchers refer to variation in quality levels of products within a category as vertical differentiation whereas variation in the function or category of the products is referred to as horizontal differentiation much of the existing research on the relationship between product line structure and brand equity has focused on the horizontal structure of the product lineand has been primarily concerned with brand extensions what happens when the product line of a brand is extended horizontally into new categories researchers have been concerned primarily with how the extension fares but the effect of the extension on the core products is also important there is an analogous question of what happens when the product line of a brand is extended vertically either up market or down market this question of vertical extensions is part of the more general issue of how the vertical structure of a product line relates to brand equity the specific research questions addressed in this paper are 1 do premium or high quality products enhance the brand equity associated with the other products in the line 2 conversely do economy or low quality products diminish the brand equity associated with the other products in the line these research questions are relevant to three managerial issues in product line strategy first what are the costs and benefits of including down market products within a brand second what are the implications of including high end models within a brand third when should high end and low end products be offered under an existing brand umbrella and when should these products be offered under separate brands we address these research questions empirically through an analysis of the models and brands within the u s mountain bicycle industry we use price premium above that which can be explained by the physical characteristics of the bicycle as a metric for brand equity we then test several hypotheses related to the relationship between extension of the product line upward and downward and the price premium commanded by the brand we further support this analysis with a simple laboratory experiment the analysis reveals that price premium in the lower quality segments of the market is significantly positively correlated with the quality of the lowest quality model in the brand s product line and that for the upper quality segments of the market price premium is also significantly positively correlated with the quality of the highest quality model in the brand s product line the results of the analysis are supported by the outcome of an experiment in which 63 percent of the subjects preferred a product offered by a high end brand to the equivalent product offered by a low end competitor these results imply that managers wishing only to maximize the equity of their brands would offer only high quality products and avoid offering low quality products however this result must be moderated by the overall objective of maximizing profits maximizing profits is likely to involve a tradeoff between preserving high brand equity and therefore high margins and pursuing the volume typically located in the lower end of the market one of the most significant implications of this research is that product line managers need to be mindful not just of the incremental cannibalization or stimulation of sales of products that are immediate neighbors of an extension to the product line but also the effect of such an extension on the brand equity in other possibly quite different parts of the product line

optimal product launch times in a duopoly balancing life cycle revenues with product cost we present a model describing the demand dynamics of two new products competing for a limited target market the demand trajectories of the two products are driven by a market saturation effect and an imitation effect reflecting the product experience of previous adopters in this general setting we provide analytical results for the sales trajectories and life cycle sales of the competing products we use these results to study the impact of launch time on overall life cycle sales we consider the perspective of one of the competing products and model the trade off between the lost revenues resulting from a delayed launch and the lower unit production costs we find that the profit maximizing launch time exhibits a counterintuitive behavior in particular we show that a firm facing a launch time delay from a competing product might benefit from accelerating its own product launch as opposed to using the softened competitive situation to further improve its cost position we identify conditions under w

optimal economic ordering policy with deteriorating items under different supplier trade credits for finite horizon case abstract this paper develops and solves a general finite horizon trade credit economic ordering policy for an inventory model with deteriorating items under inflation and time value of money when shortages are not allowed the time horizon is divided into different cycles each of which has its own demand rate and its own trade credit period offered from the supplier to his retailer so that the retailer should pay his supplier before or after the end of the permissible trade credit of that cycle up to the end of the trade credit of a cycle the retailer is free of charge but he is charged on an interest for those items not being sold before this end the retailer can also earn the interest of the money from the generated sales revenue in any cycle by depositing such revenue into an interest bearing account the objective of the retailer is then to minimize his net total relevant costs a closed form of this net total cost is derived and the resulting model is solved then rigorous mathematical methods are used to show that under some seemingly possible conditions there exist a unique vector of the relevant decision variables that solve the underlying inventory system a numerical example which shows the applicability of the theoretical results is given

two warehouse partial backlogging inventory models for deteriorating items under inflation abstract in many real life situations the practical experiences reveal that some but not all customers will wait for backlogged items during a shortage period such as for fashionable commodities or high tech products with short product life cycle the longer the waiting time is the smaller the backlogging rate would be according to such phenomenon taking the backlogging rate into account is necessary thus i here extend the models introduced in yang 2004 two warehouse inventory models for deteriorating items with shortages under inflation european journal of operational research 157 2 344 356 to incorporate partial backlogging and then compare the two two warehouse inventory models based on the minimum cost approach the study shows that the optimal solution not only exists but also is unique and model 2 is still less expensive to operate than model 1 if the factors of partial backlogging and inflationary effect are considered finally some numerical examples for illustration are provided and sensitivity analysis on some parameters is made

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

an eoq model for deteriorating items with a linear trend in demand and shortages in all cycles abstract we consider here the inventory replenishment problem over a finite time horizon for a deteriorating item with a linear trend in demand equal replenishment cycles and shortage in every cycle the reorder number the interval between two successive reorders and the shortage intervals are all determined in an optimal manner so as to minimize the average system cost the advantage of allowing shortage in all cycles is illustrated with a numerical example

on a finite horizon production lot size inventory model for deteriorating items an optimal solution abstract a generalized production lot size inventory model for deteriorating items over a finite planning horizon is considered the demand production and deteriorating rates are assumed to be known and continuous functions of time shortages are allowed and completely backlogged the conditions under which the system total cost attains its unique global minimum are derived an example which illustrate the applicability of theoretical results is also introduced

two period production planning and inventory control we study a single product two period production inventory model in which the demands at each period are independent random variables to optimally satisfy these random demands quantities can be produced at the beginning of each period using slow or fast production mode under capacity constraints in addition to the usual decision variables for such models we consider that a certain quantity can be salvaged at the beginning of each period such salvage processes are useful if the initial inventory of a period is considered to be too high the unsatisfied demands for each period are backlogged to be satisfied during the next periods after the end of the second period a last quantity is produced in order to satisfy remaining orders and to avoid lost sales the remaining inventory if any is salvaged we formulate this model using a dynamic programming approach we prove the concavity of the global objective function and we establish the closed form expression of the second period optimal policy then via a numerical solution approach we solve the first period problem and exhibit the structure of the corresponding optimal policy we provide insights via numerical examples that characterize the basic properties of our model and the effect of some significant parameters such as costs demand variabilities or capacity constraints

a note on optimal replenishment policies for non instantaneous deteriorating items with price and stock sensitive demand under permissible delay in payment abstract soni 2013 int j prod econ 146 1 259 268 proposed optimal replenishment policies for non instantaneous deteriorating items i e the product starts deteriorating after a period of no deterioration with price and stock sensitive demand with a stock dependent demand it is desirable to have non zero ending inventory due to potential profit resulting from the increased demand however soni 2013 int j prod econ 146 1 259 268 treated those ending inventory as fresh stocks to go through another period of non deterioration again additionally he assumed for simplicity that the replenishment cycle time t must be longer than the period of non deterioration t d i e t t d in reality one should consider all possible replenishment cycle time to maximize the profit in this note we complement the shortcomings of his model by i selling those ending inventory as salvages and ii considering all possible replenishment cycle time which may be shorter than the period of non deterioration with these modifications the repeatability of the replenishment cycle is ensured and the applicability of soni s model is strengthened the numerical examples indicate that the global optimal solution is indeed possible in the case of t t d

a new product growth for model consumer durables this article originally appeared in management science january 1969 volume 15 number 5 pp 215 227 published by the institute of management sciences a growth model for the timing of initial purchase of new products is developed and tested empirically against data for eleven consumer durables the basic assumption of the model is that the timing of a consumer s initial purchase is related to the number of previous buyers a behavioral rationale for the model is offered in terms of innovative and imitative behavior the model yields good predictions of the sales peak and the timing of the peak when applied to historical data a long range forecast is developed for the sales of color television sets

a simple rule for determining replenishment intervals of an inventory item with linear decreasing demand rate abstract considerable amount of research efforts have not so far been devoted to inventory replenishment problems where the rate of demand decreases with time in comparison to increasing pattern of demand rate this article presents a simple rule for determining the replenishment intervals of an inventory item having a linear decreasing demand rate over a finite planning horizon in heuristic approach the proposed method is applied to the well known silver s heuristic continuous time part period heuristic and continuous least unit cost method and its performance is examined with a numerical example

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

inventory models with ramp type demand rate partial backlogging and weibull deterioration rate in this paper an inventory model with general ramp type demand rate time dependent weibull deterioration rate and partial backlogging of unsatisfied demand is considered the model is studied under the following different replenishment policies a starting with no shortages and b starting with shortages the model is fairly general as the demand rate up to the time point of its stabilization is a general function of time the backlogging rate is any non increasing function of the waiting time up to the next replenishment the optimal replenishment policy for the model is derived for both the above mentioned policies

optimal order policy for deteriorating items with inflation induced demand abstract this paper presents the optimal inventory replenishment policy of deteriorating items under inflationary conditions using a discounted cash flow dcf approach over a finite planning horizon a dcf approach permits a proper recognition of the financial implication of the opportunity cost and out of pocket costs in inventory analysis it also permits an explicit recognition of the exact timing of cash flows associated with an inventory system the demand rate is assumed to be a function of inflation shortages are allowed and completely backlogged optimal solution for the proposed model is derived and the effects of deterioration and inflation on the optimal inventory replenishment policy are studied with the help of numerical example

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

the welfare and transfer effects of cotton price policies in egypt 1965 78 egyptian agriculture has been characterized by government controls for over a century since 1952 production and foreign trade have been heavily regulated on the input side the prices and quantities of fertilizers fuel seed pesticides credit machinery land and water have been controlled internal prices have been kept stable this implies a tax when international prices are low and a subsidy when they are high price and quantity intervention have been important for export crops particularly cotton a major foreign exchange earner this paper estimates the response of egyptian farmers to price changes focusing on production decisions for extra long and long staple lint cotton because cotton is the major input to the domestic textile industry and because egypt plays a major role in the world cotton market the model allows for the joint determination of export prices cotton production and cotton consumption the relevant supply and demand elasticities are estimated from a simultaneous equation system the welfare and transfer effects of the cotton pricing policy are then measured

celebrating a century of the economic order quantity model in honor of ford whitman harris abstract this writing presents a brief introduction to the papers included in the special issue celebrating a century of the economic order quantity model in honor of ford whitman harris published by the international journal of production economics forty one papers covering an extensive scope of inventory management have been incorporated in this volume from contributing authors from 20 countries located in america asia europe and africa this special issue also provides a basis for new directions in inventory management research

research note multinational diffusion models an alternative framework the literature on cross national diffusion models is gaining increased importance today due to the needs of present day managers new product sales growth in a given nation or society is affected by many factors rogers 1995 and of these sociocontagion or word of mouth has been found to be the most important factor that characterizes the diffusion process bass 1969 moore 1995 hence it is interesting and perhaps challenging to analyze what would happen if a new product diffuses in parallel in two neighboring but culturally different countries not only will we expect the diffusion process in the two countries to be different but we will also expect some interaction among them especially if the two societies mingle with each other there are two streams of research in cross national diffusion the first type focuses on exploring the differences between diffusion processes in two countries and finding out whether those differences can be attributed to social and cultural differences between the countries involved examples of this type of research are found in takada and jain 1991 gatignon et al 1989 helsen et al 1993 and kumar et al 1998 these studies did find some relationship between the cultural differences of the countries studied and the differences in the diffusion process the second stream of research focuses on modeling explicitly the interaction between the diffusion processes in two countries the interaction is typically captured through lead lag effect eliashberg and helsen 1996 kalish et al 1995 where the sales process in the lead country i e the country where the product was first introduced is modeled to affect the sales process in the lag country i e the country where the product was introduced a few years later another method to study the interaction among the diffusion processes in two countries was suggested by putsis et al 1997 who used a mixing model to empirically explore the existence of such interactions these studies basically observed that when a new product is introduced early in one country and with a time lag in subsequent countries the consumers in the lag countries learn about the product from the lead country adopters resulting in a faster diffusion rate in the lag countries ganesh and kumar 1996 formulized this effect as the learning effect and subsequently ganesh et al 1997 found this learning effect to be influenced by country specific factors cultural similarity economic similarity and time lag elapsed between the lead and the lag countries and product specific factors continuous vs discontinuous innovation and the presence or absence of a standardized technology a careful analysis of the extant literature on the second stream of research would reveal that neither the learning effect model nor the mixing model can be modified to accommodate the other model our contribution to the literature exactly addresses this point in this paper an alternative framework is proposed that has two unique features first the framework is flexible enough to not only account for the lead country affecting the lag countries and vice versa but also to accommodate the simultaneous interaction among countries in explaining the diffusion processes in the countries concerned using multiple product categories and a variety of new product introduction situations we empirically demonstrate the flexibility and efficiency of our proposed framework we found strong evidence of all types of interactions namely lead lag lag lead and simultaneous which evidence suggests that one cannot afford to omit any of the interactions the second unique feature of our paper is the estimation procedure that we used because statistical estimation of a dynamic process that includes lead lag lag lead and simultaneous types of causality within a single framework is not straightforward we suggest an iterative estimation procedure for the estimation this new procedure not only proved to be flexible in accommodating different types of interaction but also converged rather quickly in all of the cases that we empirically tested noting that the statistical properties of these estimators are not generally available we carried out a simulation exercise that clearly revealed the efficiency of the proposed estimation procedure after analyzing the interaction we went further and showed that the magnitude of the cross national influences is affected by certain country specific and product specific factors the flexibility of the proposed method over the existing methods is demonstrated through obtaining superior forecasts with the proposed method several interesting insights for managers concerned with formulating international marketing strategies are offered

price responsiveness efficiency and the impact of structural adjustment on egyptian crop producers abstract this paper examines the role of prices and the impact of the structural adjustment reforms undertaken by the government of egypt in 1986 on the producers of five major crops the results indicate that the program had a positive net impact on the welfare of individual crop producers evaluated as a gain in production efficiency crop profitability was also found to be highly responsive to input and output prices the results highlight the importance of market based prices in agricultural development

the laissez faire approach to international labor migration the case of the arab middle east the weaknesses of laissez faire theories and policies on international labor migration are examined by reviewing contemporary labor migration in the middle east estimates of the number of arab migrant workers in the arab region in 1975 are presented and three types of problems that labor migration creates for sending countries are identified 1 uncertainty for both economic and political reasons about the continuation or expansion of the current flows 2 micro effects of remittance spending and labor migration and 3 the selectivity of migration and its impact on certain key sectors it is argued that although individual migrants and employers benefit from laissez faire migration policies the impacts on sending societies as a whole are ambiguous excerpt

integrated product architecture and pricing for managing sequential innovation science and technology advances drive firms to continually enhance their product s performance and launch sequentially improving offerings firms face challenges in marketing such improving products to well informed forward looking consumers who anticipate product improvements and seek to delay their purchase timing product design specifically a modular upgradable architecture in which improving and stable subsystems of a product are separated and selectively upgraded can be a valuable approach for marketers to alleviate consumer concerns about product obsolescence however such an architecture based approach can present new challenges as well and dealing with them requires carefully coordinated cross functional decision making by the firm in this paper we identify and formalize the notion of design inconsistency which refers to the monopolist firm s inability to commit to future product design architectures we find that firms experience design inconsistency even when they are able to commit to future prices and design inconsistency lowers firm profits as well as consumer surplus we then derive a joint product architecture and pricing approach to solve this problem this enables an innovating firm to optimally and in a time consistent manner launch modular upgradable products the modeling and analysis in the paper lends insight into types of markets and products for which modular upgradability is most appropriate and offers guidelines on making pricing and product design decisions jointly for managing sequential innovation this paper was accepted by preyas desai marketing

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

estimating farm level input demand and wheat supply in the indian punjab using a translog profit function application of the translog profit function to farm level data from punjab india allowed a more disaggregated analysis of the farm production structure compared to the case of cobb douglas formulation the flexibility afforded by translog formulation permitted measurement of the different impacts that exogenous variables have within and across input demand and output supply functions policy relevant elasticity estimates with respect to variable inputs and output prices fixed inputs a few soil related state of nature variables measured by soil analysis and education which are usually considered constraints to farm production were obtained and two examples of policy applications were developed

inventory model for an inventory system with time varying demand rate abstract the standard inventory problems of the multi period have been modeled under different situations specifically we have considered the demand subjects of a continuous distribution and a discrete distribution and whether the demand of each period is unchanged or not a method to get an economic order quantity in inventory systems with discrete and unchanged demand was presented in a previous paper and this method has been generalized to an inventory model with varying continuous demand however it was not achieved due to there being many classified cases in the general situations in this article the above method is discussed in the case discrete demand to determine whether it increases or decreases from period to period a theoretical method is presented by using previous results and some examples are given which suggest how the concept can handle on inventory system in order to make the decision an algorithm is also presented under some conditions and examples are shown by using the computer software program mathematica which helps to explain the findings in general cases we view the optimal policy in the inventory problems in only a few periods

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

technological change and elasticities of substitution in korean agriculture abstract in this paper by using the translog cost function two issues are investigated concerning the korean agricultural sector during the prewar 1918 to 1938 and postwar 1949 to 1971 periods first characteristics of the technology used and the process of technical innovation are analyzed second an attempt is made to determine the partial elasticities of substitution for various pairwise combinations of land labor fixed capital and working capital we find that the technological innovations in korean agriculture were land and labor saving fixed capital neutral and working capital using further we find that working capital was a strong substitute for land and labor in the prewar period and a weak substitute in the postwar period fixed capital was a weak substitute for land and labor in the prewar period and a weak complement to land and labor in the postwar period finally working capital and fixed capital were weak substitutes in the prewar period and strong complements in the postwar period

stability and chaos in demand based pricing under social interactions abstract demand based pricing is often used to moderate demand fluctuations so as to level resource utilization and increase profitability however such pricing policies may not be effective when customers purchase decisions are influenced by social interactions this paper investigates the demand dynamics under a demand based pricing policy of a frequently purchased service when social interactions are at work customers are heterogeneous and adaptively forward looking existing customers re purchase decisions are based on adaptively formed price expectations and reservation prices potential customers are attracted through social interactions with existing customers the demand process is characterized by a two dimensional dynamical system it is shown that the equilibrium demand can be unstable for a given reservation price distribution we first analyze the stability of the equilibrium demand under various scenarios of social interactions and customers adaptively forward looking behavior and then characterize their dynamics using the bifurcation plots lyapunov exponents and return maps the results indicate that the demand process can be stable periodic or chaotic the study shows that the intended effect of a demand based pricing policy may be offset by customers adaptively forward looking behavior under the influence of social interactions in fact the interplay of these factors may even lead to chaotic demand dynamics the result highlights the complex dynamics produced by a simple demand price mechanism under social interactions for a demand based pricing strategy to be effective companies must take social interactions into account

optimal policy for an inventory system with power demand backlogged shortages and production rate proportional to demand rate abstract this article analyzes an inventory system for items with time varying demand the way by which demand occurs during the inventory cycle follows a power demand pattern the production of items allows to add stock in the inventory during a replenishment period the production rate is proportional to demand rate shortages are allowed and completely backlogged holding cost shortage cost and order cost are the costs considered in the inventory model the aim consists of the minimization of the total cost per inventory cycle an efficient approach is developed to obtain the optimal scheduling period and the optimal reorder point in addition the economic lot size and the minimum cost of the inventory management is determined some numerical examples are presented for illustrating the proposed inventory model

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

mixing behavior in cross country diffusion diffusion models represent one of the key successes in marketing science we understand a great deal about what influences and shapes within country diffusion patterns however we understand far less about what influences and shapes cross country or inter country diffusion patterns clearly for firms operating in a truly global environment understanding to what extent prior adoption in one country affects current and consequently future adoption in another country can be an important consideration further understanding how the pattern of interaction across countries impacts the diffusion process can have profound implications for product launch strategies for new durable products in this paper we address the extent to which prior adoption of a new product in one country affects adoption in other countries in particular we investigate the importance of the pattern of interaction what we call mixing across countries in the context of a new product diffusion model more specifically mixing refers to the pattern of communication within and across countries for example do italians communicate only with other italians or do they influence consumers in other countries understanding and empirically estimating how these mixing patterns across countries influence the subsequent diffusion process is the central research objective of this paper while previous research in marketing addressing cross country diffusion has assumed very specific forms of cross country interaction the present study develops and estimates a flexible form of mixing that allows for the simultaneous estimation of mixing patterns across multiple countries in particular we examine the effect of mixing behavior across populations on new product adoption viewing mixing as occurring across a continuum with segregation no mixing at one end and random mixing at the other intermediate forms of mixing lie along this continuum and are called bernoulli mixing in order to produce generalizable results we obtained sales data on four product categories in the european community ec nations vcrs from 1977 1990 microwave ovens 1975 1990 compact disc players 1984 1993 and home computers 1981 1991 for each product data were collected for 10 ec nations great britain germany france italy spain belgium denmark netherlands sweden and austria a diffusion model that incorporates cross country prior adoption cross country mixing patterns and individual country covariates was estimated simultaneously across the 10 countries for each of the four products on the basis of the empirical results we conclude that mixing behavior across segments is an important consideration in new product diffusion specifically the observed pattern of mixing and the strength of cross segment influences are important considerations in allocating the marketing mix during product introduction stages the practical implication of mixing behavior is that if one wishes to understand diffusion in belgium for example it is important to not only know the diffusion parameters in belgium but also those in other ec nations accordingly these results should be of interest to managers responsible for coordinating new product launches across countries and to researchers interested in investigating cross country diffusion issues as an example of the strategic implications of the results we note that under bernoulli mixing future country launches will benefit not only from prior adoption in countries with high overall contact rates but in particular from countries with high rates of contact with other countries although there is some variance across products in general germany france italy and spain are the most gregarious as measured by the rate of contact the results suggest that a strategy of first focusing on germany france italy and spain will maximize adoption in subsequent countries each of these countries tends to have a higher percentage of its contacts with individuals internal to its borders as well as with other countries this suggests that these countries would have relatively quick adoption internally while having a strong influence externally further for countries such as denmark netherlands austria and sweden a higher percentage of their contacts are derived from outside their borders thus seeding the diffusion process by introducing first in germany france italy and spain would benefit later adoption in countries such as denmark netherlands austria and sweden although the strength of the individual country influence varies from product to product this result is generally consistent across the four products

how many parts to make at once reprinted from factory the magazine of management volume 10 number 2 february 1913 pp 135 136 152 interest on capital tied up in wages material and overhead sets a maximum limit to the quantity of parts which can be profitably manufactured at one time set up costs on the job fix the minimum experience has shown one manager a way to determine the economical size of lots

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

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

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

food price changes and household welfare what do we learn from two different approaches the use of a marginal approach can significantly distort the predicted effects of large price variations on monetary welfare over the medium to longer term this paper aims at shedding some light

economic reform and aggregate cropping patterns for egypt abstract beginning in the early 1980s the government of egypt embarked on an aggressive initiative to progressively change its centrally planned economy to a system more dependent on domestic and international markets the agriculture and food sectors have taken the lead in the economic reforms this paper investigates changes in egyptian cropping patterns as an indicator of the success of the transition toward a more market oriented economy first trends in cultivated area and gross margins during the economic reforms are described responses of cropping patterns to changes in gross margins are then evaluated a random effect distributed lag model with pooled cross sectional time series methods is used to examine the relationship for individual crops canonical correlation analysis provides a more general assessment of responsiveness of the overall cropping pattern

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

an eoq model for perishable product with special sale and shortage abstract in this paper for the first time an inventory control model to determine the optimal order and shortage quantities of a perishable item when the supplier offers a special sale is developed four possible cases based on decision that the purchaser might make about the first replenishment policy using regular economic order quantity model at reduced price or regular price if he did not take the special order and coincidence of special period length with positive or negative inventory level of the last regular period length during the special period are investigated moreover several useful theorems are suggested through which one can find closed form solution directly when there are integer operators involved in an objective function at the end in order to illustrate the proposed theorems and the solution method some numerical examples are solved and a sensitivity analysis is reported too

rice technology farmer rationality and agricultural policy in egypt estimates of a homothetic translog cost function show that egyptian rice farmers are economically rational and responsive to input price changes own price and cross price elasticities of input demand based on the cost function estimates provide insight into policies currently being pursued or considered by the egyptian government the analysis indicates a reduction in fertilizer trade restrictions could substantially reduce fertilizer prices and increase fertilizer use labor and mechanical power are not strong substitutes indicating that subsidization of machinery is not an appropriate policy to reduce agricultural labor shortages

the decision to double crop an application of expected utility theory using stein s theorem a nonlinear single equation acreage allocation model derived from expected utility theory using stein s theorem for covariance decomposition is developed this decomposition allows the covariance of utility parameters and revenues to be expressed in terms of measurable variables the model is applied to state level data to estimate the relative importance of various economic factors in determining the pattern of double cropping wheat and soybeans in the southeastern united states the hypothesis that the riskiness of returns is important in the aggregate is rejected for some of the states although the constrained expected utility model without the effect of risk performs better than a standard wheat acreage response model

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

planning for shortages net present value analysis for a deteriorating item with partial backlogging abstract this paper develops inventory models to help answer strategic questions concerning whether planning for shortages offers financial benefits a production inventory system producing a deteriorating product in batches at a finite production rate with partial backordering is considered customers pay a deposit when placing a backorder backordered items receive a discount on the sales price as lost sales may lead to customers not returning the demand rate may depend on the fraction of lost sales we develop a cash flow based profit maximising net present value npv model without the inventory cost parameters commonly used in this context unit holding cost unit backorder cost unit deterioration cost and unit lost sales cost the model finds the optimal inventory policy just like npv models that discount the traditional parameters but has the advantage of not needing to estimate the value of the traditional parameters it is shown that in models based on discounting the traditional parameters the parameters are not exogenously determinable but are non trivial functions of non financial endogenous system parameters such as the production rate annual demand rate and backorder rate extensive numerical experiments illustrate how cash flow npv models provide insights into the value of planning for shortages and strategic choices about the design of the production inventory system it also provides insight into the classical problem of how to interpret unit backorder cost and unit lost sales cost the study indicates that these insights cannot be reliably obtained from npv models based on discounting unit backorder costs and unit lost sales costs

a dual approach to measuring the nearness of near monies increasing returns to scale rts is frequently po stulated as affecting productivity in surface coal mining however it is not cl ear whether increased capital intensity or increased output is the relevant phen omenon a ray homothetic production function that incorporates the capital labor mix and fixed site geology into the scale elasticity is presented and estimated with a micro mine level dataset the results indicate that higher capital int ensity contributes to higher rts for some types of capital equipment but not al l on the average increasing rts was found with few mines approaching optimal scale copyright 1987 by mit press

egypt s multiproduct agricultural technology and agricultural policy based on the hypothesis that egyptian farmers maximise economic profits the multiproduct translog profit function is used to estimate input demand and output supply functions for corn rice and cotton crops grown in egypt s nile delta elasticity estimates indicate a generally high degree of price responsiveness the estimates are used to evaluate egyptian agricultural policies concerning labour mechanisation and output prices the results show that egypt s agricultural policies of taxing output and subsidising certain inputs have hada substantial negative impact on agricultural productivity

pesticides productivity and farmer health a philippine case study health is recognized as one of the most important components of the human capital of rural people in developing countries there is a growing body of literature showing the productivity effects of health associated with nutrition e g bliss and stern 1978 strauss 1986 deolalikar 1988 pitt rosenzweig and hassan 1990 in this literature the productivity effects of health are inferred either by correlating health indicators with wages or by including health indicators in an agricultural production function the human capital literature also has demonstrated that farmer education plays an important role in the allocative and technical efficiency of farmers welch 1970 schultz 1975

when to adopt a service innovation nash equilibria in a competitive diffusion framework abstract we study the optimal timing of adoption of a service innovation that a new entrant firm brings to a market populated by two incumbent firms our analysis is based on a model of competitive diffusion dynamics that extends the monopolistic bass model to include customer churn processes as well as a potential market expansion driven by the innovation we obtain expressions for the time trajectories of the customer bases i e the numbers of customers that use old and new service processes for the competing firms as well as sharper closed form characterizations for the setting with a stable market and homogeneous imitation process in modeling competitive dynamics we consider settings where incumbents anticipate a potential failure of the innovation we use the trajectories for the customer bases to model an optimal adoption response problem faced by one of the incumbent firms when the adoption time for the other incumbent can be anticipated or is pre announced and analyze this problem in the absence of market expansion or intra generational customer churn using the optimal response results we provide the nash equilibrium analysis of the adoption decisions by competing incumbent firms and derive sufficient conditions for the now now now never and never never adoption equilibria we use the trading volume data from the foreign exchange markets to estimate the parameters of the competitive diffusion dynamics for our model and to conduct a numerical investigation of the impact of the uncertainty associated with the success of the innovation on the incumbents nash equilibrium adoption times

firm and product specific technical efficiencies in a multiproduct cycle system measures of technical efficiency were estimated using stochastic translog production frontiers for a sample of farmers operating in a rainfed area in india these estimates were farm specific as opposed to being based on deviation from an average sample efficiency in contrast to other studies farm specific efficiency estimates were obtained for farmers growing multiple outputs in which the production levels were interrelated and each product was competing for the farm s inputs the results of the study show that on average sample participants can increase their farm output by about 30 per cent 35 per cent 28 per cent and 32 per cent respectively in the production of rice corn and rice by efficient use of existing inputs rather than by incurring any additional expenditures on inputs the empirical results imply that the potential for increasing farm outputs varies widely across farms

two warehouse partial backlogging inventory models with three parameter weibull distribution deterioration under inflation abstract in many inventory systems the effects of deterioration of physical goods have drawn much attention of various researchers in recent years the more the deterioration is the more the order quantity would be according to such consideration taking the deterioration rate into account is necessary thus in this paper i develop the two warehouse partial backlogging inventory model introduced in yang 2006 to incorporate three parameter weibull deterioration distribution the objective is to derive the optimal replenishment policy that minimizes the net present value of total relevant cost per unit time two alternative models are compared based on the minimum cost approach the study shows that the optimal solution not only exists but also is unique model 2 is still less expensive to operate than model 1 in the proposed model finally some numerical examples and sensitivity analysis on parameters are made to validate the results of the proposed inventory system

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

biased technological change and factor demand in postwar japanese agriculture 1958 84 abstract the objective of this study is to gain a better understanding of factor substitutions in postwar japanese agriculture by shedding special light on biased technological change such biased technological change is first measured then associated with the movements of factor prices and then tested for the hicksian induced innovation hypothesis in addition a decomposition analysis is carried out in order to quantitatively examine the importance of the biased effects for determining changes in factor cost shares and factor proportions during the 1958 84 period a slightly modified stevenson greene model of the translog cost function is employed this model has at least two important advantages over ordinary translog cost functions first it incorporates time into the model such that all coefficients of the ordinary translog cost function may change over time this is more realistic than the ordinary translog cost function which assumes that all coefficients are constant over the period of estimation another attractive feature is that it enables us to test the induced innovation hypothesis directly the model is applied to the 1958 84 period by making use of farm level data the results show that technological change was biased towards saving labor and other inputs and using machinery intermediate inputs and land this biased technological change is found to be in principle consistent with the induced innovation hypothesis furthermore it is shown through decomposition analyses that the biased technological change had significant impacts on changes in factor cost shares and factor proportions during these years the empirical results of this study imply that technological change in japanese agriculture has in general proceeded in a manner consistent with factor endowments conditions since the late 1950s an implication of this study for agriculture in less developed countries is that agricultural policies seeking development through technological progress should be carried out so as to take advantage of peculiar factor endowments conditions in the individual countries

capacity investment timing by start ups and established firms in new markets we analyze the competitive capacity investment timing decisions of both established firms and start ups entering new markets which have a high degree of demand uncertainty firms may invest in capacity early when uncertainty is high or late when uncertainty has been resolved possibly at different costs established firms choose an investment timing and capacity level to maximize expected profits whereas start ups make those choices to maximize the probability of survival when a start up competes against an established firm we find that when demand uncertainty is high and costs do not decline too severely over time the start up takes a leadership role and invests first in capacity whereas the established firm follows by contrast when two established firms compete in an otherwise identical game both firms invest late we conclude that the threat of firm failure significantly impacts the dynamics of competition involving start ups this paper was accepted by yossi aviv operations 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

modeling intercategory and generational dynamics for a growing information technology industry previous studies dealing with product growth have dealt only with substitution effects among successive generations of one product category and not with complementarity and competition provided by related product categories based on a broadened concept of the competitive information technology it market we develop a dynamic market growth model that is able to incorporate both interproduct category and technological substitution effects simultaneously the market potential for each category or generation is treated as a variable rather than a constant parameter which is typical of recently growing it sectors such as wireless telecommunications the model is calibrated its plausibility discussed and its face and predictive validity assessed using data on wireless telecommunications services from two asian markets results show that the market potential and sales growth of one category or generation is significantly affected by others and by the overall structure of a geographic market the model is shown to make relatively good predictions even when the data from recently introduced categories generations are limited

optimal entry timing in markets with social influence firms routinely face the challenging decision of whether to enter a new market where a firm s strong presence in an existing market has a positive influence the leverage effect on product adoption in the new market but the reciprocal social influence on the existing market is negative the backlash effect in this paper we show that a firm s optimal entry strategy in this situation cannot be characterized by the familiar now or never or now or at maturity strategies proposed in the literature we show that a strong leverage effect does not necessarily provide the justification for a firm to enter a new market and neither should a strong backlash effect necessarily deter a firm from embracing a new market the optimal strategy is predicated on a judicious trade off between the three factors of leverage backlash and patience thus an astute manager can always find the opportune time to enter the new market if she takes into account the dynamic and recursive nature of cross market interaction effects where leverage enhances the backlash but backlash weakens the leverage in a nonlinear dynamic fashion we illustrate that firms stand to benefit from explicit considerations of these effects in deciding whether and when to enter a new market furthermore we explore how the optimal time of entry into the new market relates to the time of peak sales for the existing market demonstrating that depending on the interactive effects of leverage and backlash entry could be optimal either before or after peak sales in the existing market

public research resource allocation in chinese agriculture a test of induced technological innovation hypotheses technological change is one of the most important factors underlying agricultural growth in modern societies new agricultural technology is mainly developed as a product of active search by scientists in either public or private research institutions research itself requires costly resources and produces valuable information or material demanded by other parts of the economy research is thus an economic activity and can be subjected to economic analysis it has been proposed that in a market economy the efficient allocation of research resources requires the resources to be allocated to develop new technology that saves the increasingly scarce factors of production or to technology that can be applied to commodities that have larger market demand further it has been postulated that a decentralized public research system will be able to allocate research resources efficiently in accordance with the above two hypotheses of induced technological innovation 2 there have been many studies to verify these three propositions separately in market economies 3 in this article i attempt to test the above two hypotheses of induced technological innovation simultaneously and examine the effectiveness of a decentralized research system with empirical data collected from china s public agricultural research institutes

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

new product diffusion with influentials and imitators we model the diffusion of innovations in markets with two segments influentials who are more in touch with new developments and who affect another segment of imitators whose own adoptions do not affect the influentials this two segment structure with asymmetric influence is consistent with several theories in sociology and diffusion research as well as many viral or network marketing strategies we have four main results 1 diffusion in a mixture of influentials and imitators can exhibit a dip or chasm between the early and later parts of the diffusion curve 2 the proportion of adoptions stemming from influentials need not decrease monotonically but may first decrease and then increase 3 erroneously specifying a mixed influence model to a mixture process where influentials act independently from each other can generate systematic changes in the parameter values reported in earlier research 4 empirical analysis of 33 different data series indicates that the two segment model fits better than the standard mixed influence the gamma shifted gompertz and the weibull gamma models especially in cases where a two segment structure is likely to exist also the two segment model fits about as well as the karmeshu goswami mixed influence model in which the coefficients of innovation and imitation vary across potential adopters in a continuous fashion

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

stackelberg solution in a vendor buyer supply chain model with permissible delay in payments abstract in practice vendors or sellers often offer their buyers a fixed credit period to settle the account the benefits of trade credit are not only to attract new buyers but also to avoid lasting price competition on the other hand the policy of granting a permissible delay adds not only an additional cost but also an additional dimension of default risk to vendors in this paper we will incorporate the fact that granting a permissible delay has a positive impact on demand but negative impacts on both costs and default risks to establish vendor buyer supply chain models then we will derive the necessary and sufficient conditions to obtain the optimal solution for both the vendor and the buyer under non cooperative stackelberg equilibrium finally we will use two numerical examples to show that 1 granting a permissible delay may significantly improve profits for both the vendor and the buyer 2 the sensitivity analysis on the optimal solution with respect to each parameter and 3 the comparisons between nash and stackelberg solutions

a diffusion theory model of adoption and substitution for successive generations of high technology products this study deals with the dynamic sales behavior of successive generations of high technology products new technologies diffuse through a population of potential buyers over time therefore diffusion theory models are related to this demand growth furthermore successive generations of a technology compete with earlier ones and that behavior is the subject of models of technological substitution building upon the bass bass f m 1969 a new product growth model for consumer durables management sci 15january 215 227 diffusion model we develop a model which encompasses both diffusion and substitution we demonstrate the forecasting properties of the model by estimating parameters over part of the data and projecting shipments for later periods

dynamic version of the economic lot size model this article originally appeared in management science october 1958 volume 5 number 1 pp 89 96 published by the institute of management sciences a forward algorithm for a solution to the following dynamic version of the economic lot size model is given allowing the possibility of demands for a single item inventory holding charges and setup costs to vary over n periods we desire a minimum total cost inventory management scheme which satisfies known demand in every period disjoint planning horizons are shown to be possible which eliminate the necessity of having data for the full n periods

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

a dynamic model of entry and exit in a growing industry the potential demand in a new industry evolves over time demand is initially low but advertising by the industry s early entrants can speed up demand growth however there is intrinsic uncertainty of the demand level in each period and uncertainty of the demand evolution path which can be affected by the underlying economic environment we construct a dynamic model that features the stochastically and endogenously expanding demand of a new industry and we investigate the optimal entry and exit behavior of firms as the industry evolves we find that firms incentive to enter early depends critically on the cost that early entrants have to pay in developing the market when the cost is high and the benefit spills over to potential entrants firms have an incentive to wait and the probability of entry can increase with the number of incumbents under certain circumstances firms entry strategy is also influenced by the transition of economic states firms are more likely to enter under a state that shows the prospect of demand taking off soon we also find that in the early stage of an industry higher demand uncertainty can induce faster entry

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

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

is small beautiful farm size productivity and poverty in asian agriculture the debate on the relationship between farm size and productivity has gone through a complete circle in the 1960s it was perceived that small farms were efficient because they can fully use their resources particularly family labor and they can monitor their production activities closely but in the 1970s and 1980s as many asian countries rapidly moved towards industrialization and urbanization small farms were considered a major obstacle in this process