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

pricing and lot sizing polices for perishable goods when the demand depends on selling price displayed stocks and expiration date abstract price is a major factor on the demand based on marketing and economic theory in addition the demand for perishable products also depends on its freshness moreover it is a well known fact that increasing stock display e g fresh fruits vegetables baked goods may encourage consumers to purchase more this paper first proposes an inventory model that stipulates the demand explicitly in a multivariate function of price freshness and displayed stocks it may be profitable to have a closeout sale at a markdown price and always keep on hand displayed stocks fresh and plentiful if the demand is freshness and stock dependent hence the traditional assumption of zero ending inventories is relaxed to a non zero ending inventory as a result the objective is to determine three decision variables i e unit price cycle time and ending inventory level in order to maximize the total profit then it is demonstrated that the total profit is strictly pseudo concave in those three decision variables which reduces the search for solutions to a unique local maximum finally numerical examples to illustrate the theoretical results and to highlight managerial insights are presented

interdependence issue importance and the 2009 russia ukraine gas conflict the primary aim of this paper is to explain the 2009 russia ukraine gas conflict in particular it attempts to identify the causal mechanisms between their interdependence in the gas sphere and the gas conflict the paper first shows that existing theories in the study of international relations have limitations in accounting for that conflict therefore a theoretical framework drawing insights from armstrong s model on dependence political compliance and crescenzi s exit model is proposed to explain it relying on this framework this paper demonstrates that the 2009 russia ukraine gas conflict took place through two critical causal mechanisms in the contexts of the 2008 global financial crisis and ukraine s anti russian policy russia and ukraine both considered issues involved in the gas trade such as debts prices transit tariffs and ukraine s pipeline system to be very important therefore when russia issued demands with economic threats ukraine refused to comply

an econometric decomposition of dairy output growth fixed effects production functions and stochastic production frontiers are estimated and used to decompose dairy farm output growth into technological progress technical efficiency and increased input use or the size effect unbalanced panel data for ninety six vermont dairy farmers for the 1971 84 period are utilized the results show a 2 5 average annual increase in milk output about 56 of this growth is attributed to the size effect and the remaining 44 to productivity growth technological progress contributed about 94 to total productivity growth while improvements in technical efficiency accounted for only 6

age based vs stock level control policies for a perishable inventory system abstract in this study we investigate the impact of modified lotsize reorder control policy for perishables which bases replenishment decisions on both the inventory level and the remaining lifetimes of items in stock we derive the expressions for the key operating characteristics of a lost sales perishable inventory model operating under the proposed age based policy and examine the sensitivity of the optimal policy parameters with respect to various system parameters we compare the performance of the suggested policy to that of the classical q r type policy through a numerical study over a wide range of system parameters our findings indicate that the age based policy is superior to the stock level policy for slow moving perishable inventory systems with high service levels

russia s natural gas policy toward northeast asia rationales objectives and institutions the article examines the institutional dimensions of russia s gas policy toward northeast asia nea1 during the liberal economic reforms of the 1990s development of natural gas deposits in the russian far east was made possible under the scheme of production sharing agreements psa however new psas were banned in russia even before the advent of state capitalism in the early 2000s this was to a large extent the result of strong anti psa lobbying led by the domestic energy business elite consequently russia s gas policy in the east began evolving from being project specific toward being region specific contemporary russian gas policy toward nea relies upon domestic national and regional and external institutions in 2009 following the completion of a liquefied natural gas lng plant in sakhalin russia entered nea gas markets transformations in the international gas markets facilitated the establishment of a two pattern gas export policy in russia in 2013 under this policy russia s eu oriented pipeline gas export remains monopolised by gazprom while asia oriented lng export is partially liberalised russia has not been experiencing institutional discrepancy in nea gas markets however as the markets evolve toward greater coordination a rational option for russia is to genuinely liberalise its gas policy

the effects of strategic and economic interdependence on international conflict across levels of analysis this study develops a social network analytic approach to conceptualize and measure interdependence across levels of analysis this framework contains several innovations first it integrates sensitivity interdependence the effects of changes in one state on other states with vulnerability interdependence the opportunity costs of breaking a relationship second it measures interdependence at different levels of analysis and across multiple relationships third it integrates multiple dimensions of interdependence into a single measure i derive hypotheses from the realist and liberal paradigms regarding the effects of strategic and economic interdependence on monadic dyadic and systemic conflict these hypotheses are tested via data on alliances military capability and trade the findings provide robust support to the expectations of the liberal paradigm regarding the effects of strategic and economic interdependence on conflict on the other hand the expectations of the realist paradigm are not supported i discuss the theoretical and empirical implications of this approach

an s 1 s inventory system with emergency orders in this paper we develop an approximate model of an inventory control system in which there exist two options for resupply with one having a shorter lead time we assume that demand and the fixed ordering costs are small relative to the holding cost so that a one for one ordering policy is appropriate we consider a policy for placing emergency orders that uses information about the age of outstanding orders we derive the steady state behavior of this policy and present some computational results

oil and natural gas in russia s eastern energy strategy dream or reality the article analyses russia s eastern energy strategy in the sectors of oil and natural gas presenting its main aspects and examining it from the security perspective against the backdrop of official russian documents

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

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

deconstructing the energy weapon russia s threat to europe as case study abstract as the likelihood increases that russia will dominate the european union s eu energy supply questions have emerged as to whether russia would use the energy weapon to influence eu member policies and extract political concessions countervailing voices argue that russia would be restricted by interdependence and market forces as of yet no one has analyzed the assumptions underlying the energy weapon thesis moreover many scholars examining eu russian energy relations rely on non russian data this article seeks to fill several informational and theoretical gaps by including russian sources and first hand data and by systematically analyzing the conditions that must obtain before an energy supplier can successfully convert its energy resources into political power the resulting model can be utilized to analyze the capacity of a supplier to use the energy weapon whether it be russia iran venezuela or any other energy heavyweight and to assess whether the deployment was successful five purported cases of russian manipulation are analyzed in this article and the findings indicate that more often than not russia failed to achieve political concessions looking to the future the plausibility of russia using the energy weapon to exploit europe s dependence particularly on gas is also examined

inventory problems with perishable items fixed lifetimes and backlogging our model deals with a single product and a single stock location with poisson demand the replenishment leadtime from the external supplier is fixed the lifetime of the product is also fixed and aging is assumed to begin when the order is placed when the age of a unit has reached its lifetime the unit is useless and thus discarded from the system the replenishment policy is assumed to be an order up to s policy demand that cannot be met immediately is backordered we consider three different cases where the service requirements are represented by 1 backorder costs per unit 2 a service level constraint 3 backorder costs per unit and time unit cases 1 and 2 are solved exactly while an approximation is developed for case 3 we show how the results from an earlier paper assuming lost sales can be used to solve the considered problems our results are compared to the results in a related paper considering q r policies c 2009 elsevier b v all rights reserved less

the application of queueing theory to continuous perishable inventory systems this paper develops two distinct models for studying inventory systems with continuous production and perishable items the perishable items have a deterministic usable life after which they must be outdated for each of the models analytical expressions derived from queueing theory are found for the steady state distribution of system inventory knowledge of this steady state behavior may be used for evaluation of system performance and for consideration of alternatives for improving system performance both models assume that inventory is replenished by a continuous production process the first model assuming continuous inventory units has poisson demand requests with the size of each request distributed as an exponential random variable the second model has poisson demand requests with all demands being for a single unit the analysis for both models exploits the similarity of the inventory system with a single server queueing system

technology and efficiency in a panel of italian dairy farms an sgm restricted cost function approach this article employs a short term specification of the symmetric generalised mcfadden sgm cost function capable of accommodating quasi fixed factors and variable returns temporary equilibrium and scale economies are investigated while maintaining the consistency of the estimated model with microeconomic theory and approximation properties it also makes use of a two step procedure to estimate first the technology parameters and then time varying efficiency at farm level no distributional assumptions are required on efficiency as we consider a fixed effect model a balanced panel of italian dairy farms during the years from 1980 to 1992 serves as the case study the results suggest a rigid productive structure during the pre and post quota period moreover italian milk producers are found to exhibit considerable excess capacity and rather low input technical efficiency

opportunities and risks in turkmenistan s quest for diversification of its gas export routes abstract this paper applies two hypotheses regarding weak state foreign policy to analyze the opportunities and risks in turkmenistan s quest to diversify its gas export routes especially since 2006 the first hypothesis related to opportunities is that competition among major powers over the allegiance of weak states strengthens their bargaining power the second hypothesis related to risks is that the diversification policies of weak states in times of decreasing competition among great powers incur the danger of simply replacing an old master with a new one i argue that while the first hypothesis is useful in explaining the opportunities of turkmenistan s diversification policies especially before early 2009 the second hypothesis is helpful in accounting for the risks of these policies after early 2009 in other words competition among four major powers russia china the eu and india over turkmenistan s gas pipeline system before early 2009 strengthened the country s bargaining power in contrast turkmenistan s diversification policies in times of fading competition after early 2009 have left it increasingly exposed to the potential risk of replacing its old master russia with a new one china

productivity growth and inter sector spill over in dutch horticulture 1976 1995 this article calculates nonparametric measures of total factor productivity growth on dutch horticultural firms in the period 1976 1995 individual components of total factor productivity growth i e efficiency change and technical change are regressed on socioeconomic factors reflecting the effects of the world oil crises household and demographic characteristics location and investment in physical capital also the article investigates the presence of inter sector spill overs between groups of firms with different specializations in dutch horticulture

an approximation to the continuous review inventory model with perishable items and lead times a continuous review perishable inventory model based on approximations to the expected outdating the expected shortage quantity and the expected inventory level is developed to determine a best q r ordering policy under a positive order leadtime when the total expected average cost per unit time is minimized the approximation method is simple and verified by a comparison with the weiss model the results reveal that the mean absolute deviation from the optimal total expected average cost per unit time is only 0 58 this paper also compares the proposed model to the conventional model with no perishability a value is given to the item lifetime indicating when an approximate answer approaches closely to the conventional ordering policy finally a simulation model written in simscript ii 5 is used to validate the approximate results

investing in the peace economic interdependence and international conflict research appears to substantiate the liberal conviction that trade fosters global peace still existing understanding of linkages between cone ict and international economics is limited in at least two ways first cross border economic relationships are far broader than just trade global capital markets dwarf the exchange of goods and services and states engage in varying degrees of monetary policy coordination second the manner in which economics is said to inhibit cone ict behavior is implausible in light of new analytical insights about the causes of war we discuss and then demonstrate formally how interdependence can ine uence states recourse to military violence the risk of disrupting economic linkages particularly access to capital may occasionally deter minor contests between interdependent states but such opportunity costs will typically fail to preclude militarized disputes instead interdependence offers nonmilitarized avenues for communicating resolve through costly signaling our quantitative results show that capital interdependence contributes to peace independent of the effects of trade democracy interest and other variables students of world politics have long argued that peace is a positive externality of global commerce theorists like montesquieu and kant and practitioners like woodrow wilson asserted that economic relations between states pacify political interaction mounting evidence in recent years appears to substantiate these claims multiple studies many identie ed with the democratic peace link interstate trade with reductions in militarized disputes or wars 1 while we concur with the evolving

dairy farm efficiency measurement using stochastic frontiers and neoclassical duality this paper presents a stochastic efficiency decomposition model based on kopp and diewert s deterministic methodology the stochastic model is used to analyze technical economic and allocative efficiency for a sample of new england dairy farms the results suggest that mean economic efficiency for the farmers in the sample is about 70 and that on average there is little difference between technical 83 0 and allocative 84 6 efficiency analyses of the relationship between efficiency and four socioeconomic variables farm size education extension and experience reveal that despite some statistically significant associations efficiency levels are not markedly affected by these variables

efficiency technological change and output growth in greek olive growing farms a box cox approach this paper captures the relative contributions of input growth technological change and technical efficiency to olive oil production growth for a panel data set of 125 greek olive growing farms for the period 1987 to 1993 a flexible generalized quadratic box cox functional form is proposed to represent the underlying production technology this functional specification copes with the problem of zero inputs and nests all widely used production frontiers empirical results show that the observed production growth is mainly due to increased input use since it was not accompanied by rapid introduction of technological innovations and improvements in efficiency levels

technical efficiency and farm size a conditional analysis the relationship between technical efficiency and size might be affected by farm heterogeneity we analyse this relationship conditional on a set of control variables these control variables are chosen using a production model where technical efficiency is introduced as a parameter as a result technical efficiency affects both the input demand and the output supply of a profit maximising producer the empirical application explores these issues using panel data of dairy farms in spain

operating characteristics of the s 1 s inventory system with partial backorders and constant resupply times in this paper we consider an s 1 s inventory system with poisson demand and constant resupply times an arriving customer facing stockout will either backorder or withdraw its order expressions describing steady state operating characteristics of the system and the expected total cost rate are developed furthermore the behavior of the expected total cost rate as the function of the relevant parameters is explored

effects of technological change and institutional reform on production growth in chinese agriculture recent rapid agricultural production growth in chinese agriculture could be attributed to an increase in inputs technological change and institutional reform an accounting approach was used to separate the relative contribution of these three factors institutional change like the introduction of the household production responsibility system has contributed to past growth in production however technological change is crucial to furthering production growth because of the limited potential for significant increase in the use of conventional inputs in particular land continued institutional change must accompany corresponding technological changes

parametric decomposition of output growth using a stochastic input distance function midmore peter karagiannis g tzouvelekas v parametric decomposition of output growth using a stochastic input distance function american journal of agricultural economics 2004 86 4 pp 1044 1057

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

is russia building too many pipelines explaining russia s oil and gas export strategy abstract the article examines russia s entire oil and gas export network and reveals that there is a considerable surplus pipeline capacity which is likely to endure in the future it brings to attention surplus capacity as a concept that could enrich discussions on what drivers russia s energy policy abroad and how moscow enhances its energy security the article provides three explanations on russia s surplus capacity for oil and gas exports first russia s institutional setting has been conducive for a surge in new pipelines as economic considerations have played a less significant role second russia s energy pivot to asia has already contributed to a widening surplus capacity in westbound oil pipelines and it is likely to have a similar impact on gas once it starts flowing to china third russia s energy security concerns namely about minimising transit risks have played a key role in its active pipeline diplomacy and new pipeline ventures the implications of russia s surplus capacity can be significant for oil the room for manoeuvring is wide enough to allow russia abandon an entire route of its choice for gas moscow is likely to enhance its bargaining position with ukraine while gazprom acquires more flexibility to deliver gas abroad

energy productivity growth in the dutch greenhouse industry profitability of dutch greenhouse firms is largely dependent on energy costs and policy makers focus on reducing the use of energy by these firms this article uses russell measures of te to develop indicators of energy productivity growth results show that energy productivity grew by 2 8 annually in the period 1976 95 with technical progress being the key factor driving the process of productivity growth from this we conclude that policies aiming at enhancing the adoption of technological innovations are more effective if due attention is paid to measures for improving te

approximations for the relative outdating of perishable products by combining stochastic modeling simulation and regression modeling abstract in this paper we derive approximations for the expected amount of outdating waste in an inventory system with perishable products periodic review positive lead time fixed case pack sizes and a first in first out withdrawal policy demand is discrete and stochastic demand which is not met from inventory on hand will be lost the approximations can be used to evaluate how the amount of outdating can be reduced by changing the safety stock and or the product and demand characteristics we first derive approximations in an analytical way and then use regression to improve these approximations the final approximation is very fast and performs very well the mean and standard deviation of the approximation error are equal to 0 01 and 0 78 moreover the approximation is applicable in situations with parameter settings which are frequently encountered in practice and for which no other approximations have been derived in the literature before

economic structure and international security the limits of the liberal case the theory that a liberal international economic structure is associated positively and a mercantilist structure negatively with international security is widespread but the case in favor of liberalism and the case against mercantilism are both one sided and the whole attempt to link economic structure to international security anyway overestimates the influence that economic structure has on the use of force political and military factors provide explanations more convincing than economic ones for the propensity of states to resort to or refrain from the use of force liberal and mercantilist structures each have both positive and negative impacts on the use of force but these impacts become important only when they are complemented by noneconomic factors governing the use of force hence security grounds cannot be used convincingly either as a reason for maintaining the current liberal system or as a reason for opposing a shift toward a more mercantilist structure of international economic relations

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

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

emergency lateral transshipments in a two location inventory system with positive transshipment leadtimes abstract we consider a single echelon continuous review inventory system for spare parts with two parallel locations each location faces independent poisson demand and backorders are allowed in this paper we consider the possibility of lateral transshipments between the locations the transshipment leadtime is positive and deterministic and there is an additional cost for making a transshipment we suggest a transshipment policy which is based on the timing of all outstanding orders and develop and solve a heuristic model by using theory and concepts from doubly stochastic poisson processes and also partial differential equations a simulation study indicates that our heuristic works very well and that the relative cost increase of disregarding the transshipment leadtime may be quite high our results also indicate that it is in general worth the effort of reducing the transshipment leadtime even if it is already relatively short

a coordinated multi item inventory system for perishables with random lifetime abstract this paper considers the continuous review can order s c s policy for coordinating the replenishment of multiple perishable items with random lifetimes for zero lead time we model this inventory system as a markov process an iterative procedure is proposed to solve the joint replenishment problem for perishable items under positive lead time we investigate the impact of perishability and cost parameters on the performance of the can order policy and compare it to the optimal periodic review s s policy

between russia as producer and ukraine as a transit country eu dilemma of interdependence and energy security abstract between 2014 and 2015 the eu started a new energy policy in order to address among other issues the problematic character of energy interdependence with russia and thus improve its energy security the aim of this article is to determine how this policy considered interdependence with russia in the light of diversification alternatives energy security is seen through short term and long term dimensions which can be equated to the concepts of vulnerability and sensitivity interdependence as the article shows the alternative of lng is limited by production and consumption patterns in both europe and other world markets it also shows that maintaining interdependence with russia and reducing the role of transit countries such as ukraine would yield benefits both in vulnerability and sensitivity interdependence however while the eu has strongly based its rhetoric on the promise of lng it has ignored alternatives that would maintain interdependence with russia eventually the eu s energy strategy has acknowledged the limitations of lng even though it has not changed its stance towards russia in that respect it seems fair to conclude the eu has not rigorously analysed the transit dimension in its interdependence with russia and the implications for its energy security