joint pricing and ordering policy for two echelon imperfect production inventory model with two cycles abstract this study deals with an imperfect epq economic production quantity price dependent inventory model over two types of cycles in the first cycle the retailer sells only good product with actual price and in the second he sells the products with a discount price in the production run time the non conforming items are produced at a random rate and they are reworked after the regular production run time and the reworked items are almost perfect as good as original quality items the retailer starts the second cycle when a certain percent of good items are left to him after the completion of regular production the retailer continues simultaneously two cycles up to which both types of the products are available to him now our objective is to find out optimal ordering lot size and optimal price for which the profit of the integrated model is maximum also we check the best strategy of retailer for the time of starting second cycle a numerical example is provided to illustrate the behavior and application of the model

optimal lot sizing for an unreliable production system based on net present value approach abstract the paper considers the net present value npv approach to determine the economic manufacturing quantities for an unreliable production system over an infinite planning horizon the npv of the expected total cost is obtained under general failure time and general repair time distributions and its asymptotic characteristics are examined by perturbation of the instantaneous discount rate the criteria for the existence and uniqueness of the optimal production time lot size are derived under exponential failure and constant zero repair time the performance of the npv model is compared with the traditional long run average cost model in terms of the npv of the expected total cost based on the optimal decisions of the two models from numerical experiments it is observed that the decision based on the average cost can be 10 worse than the decision based on the npv depending upon the machine failure rate

barriers to energy efficiency a comparison across the german commercial and services sector abstract based on a large sample for the german commercial and services sector this paper econometrically assesses the relevance of various types of barriers to energy efficiency at the sectoral level and across fifteen sub sectors the results at the level of entire sectors suggest that the lack of information about energy consumption patterns and about energy efficiency measures lack of staff time priority setting within organizations and in particular the investor user dilemma are all relevant barriers allowing for sector specific differences in the relevance of these individual barriers yields a more heterogeneous picture the numbers and types of relevant barriers vary across sub sectors and the majority of sub sectors are subject to relatively few barriers the statistically most significant barriers are found for the sub sector of public administrations these findings are robust independent of whether the definition of an organization s energy efficiency performance includes only measures that have actually been realized or also those that are being planned for planned projects however organizations appear to underestimate internal priority setting as a barrier to energy efficiency

a multiproduct single machine economic production quantity model for an imperfect production system under warehouse construction cost abstract this paper develops an economic production quantity epq inventory model for a multiproduct single machine lot sizing problem with nonconforming items including scrap and rework where reworks are classified into several groups based on failure severity in this inventory model shortage is allowed and is backordered the aim is to determine the optimal period length the lot size and the allowable shortage of each product so as the total cost including setup production warehouse construction holding shortage reworking and disposal is minimized besides the available total budget is scarce and that there is a lower bound on the service level of each product while the convexity is proved an exact method is proposed to solve the nonlinear programming problem a numerical example is provided at the end to demonstrate the applicability of the proposed solution procedure as well as to perform a sensitivity analysis

note on economic production quantity model for items with imperfect quality a practical approach abstract in this note we present a simple approach for determining the economic production quantity for an item with imperfect quality we compare the results based on the simple approach with the optimal method for determining the lot size and show that almost optimal results are obtained using the simple approach

economic order quantity models for imperfect items with buy and repair options abstract one of the celebrated extensions of the economic order production quantity eoq epq model is one that assumes a received shipment contains a fraction of imperfect non conforming quality items where these items detected by 100 screening are sold as a single batch at a discounted price this paper revisits this model salameh and jaber 2000 int j prod econ 64 1 59 64 and extends it by assuming that a shipment is coming from a distant supplier and therefore it is not feasible to replace the imperfect items with an additional order to the same supplier to address this restriction two models are presented the first assumes that imperfect items are sent to a repair shop who charges a cost plus a markup margin while the second model assumes that imperfect items are replaced by good ones from a local supplier at a higher cost the inventory environment assumed in this paper is relevant in todays globalised supply chains thus practical implications of the problem faced are discussed numerical results are also presented and discussed the results show that there exists a threshold value of the unit purchase cost of an emergency ordered item and a fraction of defectives to which it is decided to either buy or repair

production planning and pricing policy in a make to stock system with uncertain demand subject to machine breakdowns abstract we consider a make to stock system served by an unreliable machine that produces one type of product which is sold to customers at one of two possible prices depending on the inventory level at the time when a customer arrives i e the decision point the system manager must determine the production level and selling price at each decision point we first show that the optimal production and pricing policy is a threshold control which is characterized by three threshold parameters under both the long run discounted profit and long run average profit criteria we then establish the structural relationships among the three threshold parameters that production is off when inventory is above the threshold and that the optimal selling price should be low when inventory is above the threshold under the scenario where the machine is down or up finally we provide some numerical examples to illustrate the analytical results and gain additional insights

optimal control of a single stage production system subject to random process shifts we consider a single stage production system with poisson demand and exponential processing times after producing a good item the production process can shift to an out of control state with a given probability and start producing bad items the state of the process is known only when the next stage or customer receives the item once an out of control process is detected process correction is instantaneous customers arriving to an empty system get backlogged in this framework we examine fifo first in first out and lifo last in first out issuing policies the objective is to minimize the total expected discounted or average costs over an infinite time horizon we characterize the structure of the optimal production policy for fifo and lifo show that lifo is better than fifo and in general better than a large class of issuing policies a numerical example illustrates that savings up to 20 percent can be obtained from using lifo over fifo we also derive conditions under which maintaining z

is there an energy efficiency gap many analysts have argued that energy efficiency investments offer an enormous win win opportunity to both reduce negative externalities and save money this overview paper presents a simple model of investment in energy using capital stock with two types of market failures first uninternalized externalities from energy consumption and second forces such as imperfect information that cause consumers and firms not to exploit privately profitable energy efficiency investments the model clarifies that only if the second type of market failure cannot be addressed directly through mechanisms such as information provision energy efficiency subsidies and standards may be merited this chapter therefore reviews the empirical work on the magnitude of profitable unexploited energy efficiency investments a literature which frequently does not meet modern standards for credibly estimating the net present value of energy cost savings and often leaves other benefits and costs unmeasured these problems notwithstanding recent empirical work in a variety of contexts implies that on average the magnitude of profitable unexploited investment opportunities is much smaller than engineering accounting studies suggest finally there is tremendous opportunity and need for policy relevant research that utilizes randomized controlled trials and quasi experimental techniques to estimate the returns to energy efficiency investments and the welfare effects of energy efficiency programs

energy reform in central and eastern europe this paper describes the current energy situation in central and eastern europe cee energy consumption patterns and energy pricing policies in the region are discussed changes in energy demand in the cee countries during the last three years and the impact on emissions of atmospheric pollutants and sulphur deposition are analysed an overview of two sets of energy projections is presented the official projections are compared with the alternative ones which assume radical changes in energy consumption arising from economic restructuring finally the most important common elements of energy policies formulated by the governments of cee countries are discussed

losers and pareto optimality in optimising commuting patterns when optimising the overall commuting pattern for a city or a region there are often winners and losers among commuters at the subdivision level losers are those who are burdened with longer commutes than before the optimisation knowing who or where losers are is of interest to both researchers and policy makers the information would help them efficiently locate losers and compensate them few however pay attention to such losers by revisiting excess commuting in the economic framework we show that optimising the commuting pattern is comparable to restoring pareto optimality in commuting using beijing as a case study we identify and geo visualise the losers when the city s bus commuting pattern is optimised we examine the severity of the loss among the losers the spatial pattern of the losers and their influencing factors we find that most losers are located around the epicenter the severity of the loss is independent of jobs housing ratio but is associated with the commute distance before the optimisation workers whose commute distance is less than the global average are more likely to become losers places where losers reside have significantly lower employment density in a few industries than where non losers reside a low jobs housing ratio in individual subareas does not necessarily increase the average trip length of commuters therein a low jobs housing ratio of one or several subareas however could influence the average trip length of all the commuters in the area locating diverse jobs and housing opportunities around or along transit corridors could compensate the losers and reduce the overall commuting cost

energy efficiency barriers in commercial and industrial firms in ukraine an empirical analysis abstract improvement in energy efficiency is one of the main options to reduce energy demand and greenhouse gas emissions however large scale deployment of energy efficient technologies is constrained by several factors employing a survey of 509 industrial and commercial firms throughout ukraine and a generalized ordered logit model we quantified the economic behavioral and institutional barriers that may impede the deployment of energy efficient technologies our analysis shows that behavioral barriers resulted from lack of information knowledge and awareness are major impediments to the adoption of energy efficient technologies in ukraine and that financial barriers may further impede investments in these technologies especially for small firms this suggests that carefully targeted information provisions and energy audits will enhance ukrainian firms investments in energy efficient technologies to save energy consumption improve productivity and reduce carbon emissions from the productive sectors

eoq models for a coordinated two level international supply chain considering imperfect items and environmental impact abstract for a two level supply chain models are presented to determine the optimal production shipment policy for items with imperfect quality in three different scenarios a both the vendor and the buyer are in the same country b the vendor and the buyer are in different countries where the stochastic behavior of the exchange rate between the two countries is modeled using a mean reverting process and c environmental impact is incorporated in determining the optimal production shipment policy by taking into account the fixed and variable carbon emission costs the objective is to minimize the total expected cost per unit time for each scenario considering equal shipment size the total expected cost per unit time is derived and the solution procedure is proposed numerical examples are presented and the results are discussed

on the job search behavior the importance of commuting time using search theory we show that job search effort is increasing and under some conditions convex in commuting time we show that the effect of commuting time on job search effort levels may be small in case of uncertainty caused by future job and residential moving behavior thus we provide a microeconomic explanation for the finding that commuters behave as if they are footloose our empirical analysis supports the behavioral implications of the model for the netherlands surprisingly we do not find any evidence that the effect of commuting time on search behavior depends on the commuters socioeconomic characteristics

barriers to industrial energy efficiency investments in greece abstract this paper sets out to investigate the main determinants of industrial decision making process with respect to energy efficiency investments based on a survey among greek industries in the empirical analysis probit models are employed the results support that an energy saving campaign should regard industries as subgroups with different needs and different managerial aspects the importance of qualified employees is also established from this survey an energy conservation framework would be more effective if the diffusion of information with regard to industrial energy saving investments is based on investment in human capital

housing choice hindrances and urban spatial structure evidence from matched location and location preference data in chinese cities abstract in a monocentric city with a well functioning residential market pareto efficient spatial equilibrium entails the sorting of residents according to their bid rent gradient in descending order away from city center violation of this sorting condition creates opportunities for pareto improving trading of locations and can be sustained only if the market is hindered we propose a simple ordered location choice model using matched location and location preference data of individual households to examine violations of the pareto efficient spatial sorting condition in so doing we are able to identify population groups facing housing choice hindrances we find in a sample of chinese cities undergoing housing market liberalization that poor marketability of the previously state provided homes inadequate provision of housing finance and spatial mismatch between job market and housing market opportunities contribute to a pareto inefficient spatial structure

the spatial effects of wage or property tax differentials and local government choice between tax instruments abstract this paper considers the spatial effects on wages employment and business capital as functions of location of a localized differential in source based wage tax rates or business property tax rates between for example a central city and the surrounding suburbs a simple model is used in which business production uses only labor and capital inputs consumers have fixed residential locations but may commute to work wage and property tax differentials have effects that are similar in some ways but different in other ways if given a choice a local government would choose to set its business property tax rate equal to zero and use only a wage tax

contract duration and relationship specific investments empirical evidence from coal markets this paper examines the importance of specific relationship investments in determining the duration of coal contracts negotiated between coal suppliers and electric utilities data for 277 coal contracts are used to perform the analysis the results provide strong support for the view that buyers and sellers make longer commitments to the terms of future trade at the contract execution stage and rely less on repeated bargaining when relationship specific investments are more important

commuting and labour supply revisited according to theory road pricing may reduce welfare when labour supply is negatively distorted by an income tax this effect particularly occurs when commuting costs reduce labour supply we examine the hypothesis that commuting costs reduce labour supply in the short run in particular we estimate the effect of commuting time on labour supply in the uk we account for endogeneity of commuting time by employing exogenous changes in commuting time resulting from firm relocations and changes in infrastructure our results cast doubt on the idea that increases in commuting cost reduce labour supply at least in the short run more precisely we find that females labour supply reacts positively to or is unaffected by increases in commuting time whereas males labour supply is unaffected

the assessment energy policy u k energy policy in the 1980s is reviewed in the light of the principal market failures in the energy sector monopoly fuel diversity security of supply and externalities the analysis is largely confined to the non oil sectors it is observed that the presence of excess capacity enabled the primary focus of policy to concentrate on competition and thus on the use of existing assets in the 1990s the u k will move into an external energy deficit and significant decisions on capacity levels and choice will be required in the electricity and coal industries the market failures associated with investment decisions and environmental pollution will therefore again come to the fore it is argued that although these longer run decisions will inevitably remain largely in public hands the policy issues in the 1990s will focus on the development of a framework within which largely privately owned firms will operate copyright 1991 by oxford university press

an economic order quantity model with defective items and shortages abstract the fundamental assumption of an economic order quantity eoq model is that 100 of items in an ordered lot are perfect this assumption is not always pertinent for production processes because of process deterioration or other factors this paper develops an eoq model for that each ordered lot contains some defective items and shortages backordered it is assumed that 100 of each lot are screened to separate good and defective items which are collection of imperfect quality and scrap items the effect of percentage defective on optimal solution is studied while numerical examples are provided for the developed model

extended excess commuting a measure of the jobs housing imbalance in seoul the balance between jobs and housing has received considerable attention in the recent debates over sustainable urban development the excess commuting technique which measures the difference between the average observed commute and the average minimum commute has been suggested as one means to identify the numerical imbalance between workplaces and residential locations this paper extends the conventional approach through the development of an extended excess commuting technique which can measure both the quantitative and qualitative imbalance the empirical results show that commuters in the seoul metropolitan area sma have tried to reduce both qualitative and quantitative imbalance based on time rather than distance over the past 10 years 1990 2000 the results show how the spatial processes of decentralisation have been countered by the economic processes of faster travel and how the net result is a saving in the journey to work travel time

an eoq model with imperfect quality items inspection errors shortage backordering and sales returns abstract in practice the items received in a lot may contain defective items and the screening process to eliminate the defective items may involve both a type i and a type ii error due to the defective items and the inspection errors shortages may sometimes occur in this paper we develop an economic order quantity model with imperfect quality items inspection errors shortage backordering and sales returns a closed form solution is obtained for the optimal order size the maximum shortage level and the optimal order reorder point if shortages are not allowed we adopt the order overlapping scheme proposed by maddah et al 2010 computers and industrial engineering 58 4 691 695 to develop an eoq model to prevent shortages during the screening process numerical examples show the impacts of the defective probability the inspection errors and the holding and backordering costs on the optimal solution

the assessment microeconomic policy in the 1980s the 1980s were a period of profound economic change in the uk the consensus politics of the post second world war period disintegrated in the face of mounting disillusionment with the uk s economic record it gave way to a radical style of politics that firmly rejected intervention by the state in managing economic activity and promoted the operation of free markets

measuring optimal population distribution by agglomeration economies and diseconomies a case study of tokyo this paper presents an empirical study on the optimality of population distribution within the tokyo metropolitan area by taking into account the effects of agglomeration economies and diseconomie

eoq with a correlated binomial supply abstract this paper considers a variant of the economic order quantity eoq model under random supply a binomial supply model is adopted where every item received is of imperfect quality with the same probability we study the realistic case where the qualities of items in an order are correlated and draw useful insights the most interesting of which is that correlation decreases the order size several practical correlation patterns are investigated and discussed we also show that several commonly used models in the literature can be represented by an equivalent correlated binomial supply model

disaggregation and consolidation of imperfect quality shipments in an extended epq model abstract we consider a standard economic production quantity epq model due to manufacturing variability a fraction p of the produced inventory will have imperfect quality where p is a random variable with a known distribution we consider a 100 inspection policy and further assume that the inspection rate is larger than that of production thus all imperfect quality items will be detected by the end of the production cycle for such an augmented epq model we first derive the new optimal production quantity assuming that the imperfect quality items are salvaged once at the end of every production cycle then we extend this base model to allow for disaggregating the shipments of imperfect quality items during a single production run finally we consider aggregating or consolidating the shipments of imperfect items over multiple production runs under both scenarios we derive closed form expressions for both the economic production quantity and the batching policy and show that our desegregation consolidation schemes can lead to significant cost savings over the base model

urban agglomeration effects and employment and wage gradients abstract when employment occurs at both central and non central points but firms have a preference to be near the center the rent gradient will decline and a wage gradient is necessary to compensate workers for more centrally located employment wage gradients and rent gradients are jointly determined the relationship between wage offer functions and the equilibrium wage gradient is derived the latter dependent on utility functions and commuting costs this is illustrated with a two sector model incorporating agglomeration economies in the export sector numerical solution reveals how agglomeration economies affect wages employment and city size

energy supply security and geopolitics a european perspective the security of energy supply to the eu is examined in the context of two storylines markets and institutions exemplifies an economically and politically integrated multilateral world with effective institutions and markets regions and empires involves a world broken up in rival political and economic blocks competing for resources and markets via political economic and military power it is shown that these storylines have a significant impact on the development of the energy market on the way in which energy supply may be secured and on the effect and applicability of the several types of instruments available the current eu is geared towards enlargement and a deepening of economic integration based on the tenets of the post 1945 multilateral world system the present world tends towards regions and empires and suggests that the eu may have to reorient its energy security policy energy policy must become an integral part of eu external trade and foreign relations and security policy the eu should develop its own strategy actively investing in dialogues with producer countries in the persian gulf and africa and with russia sustainable prosperity and governance in these regions will support eu energy security

energy consumption and economic growth evidence from the commonwealth of independent states abstract this study examines the relationship between energy consumption and economic growth for eleven countries of the commonwealth of independent states over the period 1991 2005 within a multivariate panel data framework based on pedroni 1999 pedroni 2004 heterogeneous panel cointegration test and corresponding error correction model cointegration is present between real gdp energy consumption real gross fixed capital formation and labor force with the respective coefficients positive and statistically significant the results of the error correction model reveal the presence of unidirectional causality from energy consumption to economic growth in the short run while bidirectional causality between energy consumption and economic growth in the long run thus the results lend support for the feedback hypothesis associated with the relationship between energy consumption and economic growth

commuting distances in a household location choice model with amenities abstract observed commuting distances generally exceed those predicted by standard models of household location choice this paper develops a model with locational amenities and two job centers it is shown that differences in household preferences for amenities can lead to various types of residential location patterns some of which result in higher average commuting distances in the city

wasteful commuting a resolution a debate over the empirical underpinnings of urban economic models is emerging under the unlikely rubric of wasteful commuting hamilton 1982 shows that a commonly used monocentric model in which employment and population densities decline exponentially from a center greatly underpredicts actual commuting distances in typical u s and japanese metropolitan areas he concludes that the monocentric model is fundamentally flawed this conclusion is challenged by white 1988b who examines the cost minimizing assignment of households to residential locations taking density patterns as they are and measuring cost by travel time white finds that for a sample of u s metropolitan areas only 11 percent of actual commuting cost is in excess of the cost minimizing amount rather than the 87 percent found by hamilton hamilton 1989 and cropper and gordon 1991 using variations of white s technique obtain results intermediate between these extremes this abstract was borrowed from another version of this item

effects of urban growth controls on intercity commuting this paper presents an empirical study of the effects of urban growth controls on the intercity commuting of workers growth controls land use regulations that attempt to restrict population growth and urban sprawl have increased housing prices and diverted population growth to uncontrolled cities it has been suggested that resulting changes in local labour supply might stimulate intercity commuting from uncontrolled to controlled cities to test this hypothesis a gravity model of commuting flows between places in california is estimated using alternative econometric methods ols heckman selection and count data the possibility of spatial dependence in commuting flows is also taken into consideration results suggest larger commuting flows to destination places that restrict residential growth

barriers within firms to energy efficient investments abstract many investments in energy efficiency fail to be made despite their apparent profitability internal hurdle rates are often set at levels higher than the cost of capital to the firm reasons for these practices include bounded rationality principal agent problems and moral hazard the policy implication is that government can simultaneously improve overall energy efficiency and increase private sector productivity by providing informational and organizational services that go beyond the traditional regulatory framework

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

excess commuting in the tokyo metropolitan area measurement and policy simulations in this paper tokyos commuting patterns are examined to determine the extent to which the volume of commuting is an inevitable result of the functioning of such a vast interconnected economic system and the extent to which it is the result of inefficient matching of workers and jobs some comparisons are made to the situation in los angeles several simulations are used to examine the effect of decentralisation of employment on commuting behaviour and it is found that commuting time could be significantly reduced by decentralising jobs or centralising workers excerpt

lot sizing with a markov production process and imperfect items scrapped abstract this paper considers an inventory system within the economic order quantity eoq model framework under random supply the production process can go out of control with a constant probability and start producing imperfect quality items such a system has been studied in the literature under the assumption that defective items are reworked instantaneously and returned to inventory in some situations imperfect quality items are not necessarily defective and are removed from the inventory to be used elsewhere this paper develops two models where imperfect items are removed from inventory the first model finds the expected cost and optimal lot size assuming that imperfect quality items are removed from inventory at no cost the second model assumes that batches of imperfect quality are consolidated and shipped together due to economies of scale in shipping analytical and numerical results are developed for both models revealing several managerial insights

wasteful commuting again in wasteful commuting hamilton 1982 i presented estimates that suggested that almost 90 percent of urban commuting could be eliminated by reassigning workers to different houses or jobs it does not matter which furthermore i argued that this minimum feasible commute is the volume of commuting that would emerge from the optimization process underlying the standard monocentric models even allowing for decentralized employment white 1988 has challenged some of my assumptions as well as my results with respect to assumptions she argues that suburban employment is not diffuse as i assume but is concentrated in subcenters if these subcenters are a significant portion of suburban employment then my estimates of required commuting are biased downward because the commuting pattern that i assumed to be optimal is not feasible white then estimates required and wasteful commuting based on journey to work data from the 1980 census on the basis of these data she concludes that only about 10 percent of commuting could be eliminated by swapping homes and jobs

privatizing british coal an evolving policy problem abstract this paper examines how the announcement of pit closures in 1992 and subsequent developments in the coal industry have changed and narrowed the range of available privatization options the longer term economic forces shaping the industry s prospects and the effects of the 1992 announcement and subsequent events are analysed and the alternative models of privatization both before and after the 1992 announcement are evaluated continued market uncertainties associated at least in part with the development of gas generating capacity cast doubt on the attractiveness of british coal to private investors problems are likely to arise whichever structural option is chosen for the sale of british coal although the most feasible route appears to be to split the industry into two broad regions with scotland and other more isolated pits being disposed of separately

testing the standard urban model of residential choice an implicit markets approach abstract important implications of the standard economic model of urban residential choice have failed dramatically to survive empirical tests in recent studies these results however do not distinguish between failure of the model s behavioral foundations a trade off of access to jobs and housing costs and failure of auxiliary assumptions needed to derive testable hypotheses from the model from an implicit markets model of the housing market we derive a test that better isolates the predictive power of access and housing cost as determinants of residential decisions and find substantial improvement in the model s empirical performance compared with other recent work

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

coordinating employment transport and housing in cities an institutional perspective this paper outlines a reconceptualisation of the relationship between employment housing and transport in cities that draws upon insights drawn from structuration theory and institutional sociology it identifies the need for a new focus one that lies between the structural and the individual the institution as well as the need for the integration of time space into analyses institutions are embedded social action the unique formations of institutional matrices households labour markets housing markets and transport systems are identified as sites for further research and policy development the paper calls for future research to identify who gains and who loses within the current and future configurations of institutions in cities changes in individual behaviour and the policies to enable or to constrain such behaviour should be evaluated in this light

optimality of zero inventory policies for unreliable manufacturing systems we show that there are ranges of parameter values describing an unreliable manufacturing system for which zero inventory policies are exactly optimal even when there is uncertainty in manufacturing capacity this result may be initially surprising since it runs counter to the argument that inventories are buffers against uncertainty and therefore one must strive to maintain a strictly positive inventory as long as there is any uncertainty however there is a deeper reason why this argument does not hold and why a zero inventory policy can be optimal even in the presence of uncertainty this provable optimality reinforces the case for zero inventory policies which is currently made on the separate grounds that it enforces a healthy discipline on the entire manufacturing process

revealed preference and location choice abstract the assumption that population and structural densities are defined over parcels of land with zero area is problematic when interpreting the standard residential land use model as approximating a large finite economy this paper extends revealed preference theory to depict a spatial economy with land parcels of finite area the model generalizes the standard utility function approach allowing for many consumer types with different tastes and incomes and labor leisure choice to show that the most important predictions of the standard theory hold in the general finite framework studied here

search theory spatial labor markets and commuting search theory is used to model spatial interactions between residential and employment locations a model for an urbanized region in which employment is concentrated in a number of different centers is developed it is shown that in this model wasteful or excess commuting occurs as a consequence of maximizing behavior of both employers and workers the model is compatible with a spatial equilibrium if informational problems disappear the labor market subdivides into a number of conventional monocentric cities an example concerning an urban area with two employment centers is discussed in detail the model appears to be robust to relaxations of the assumed absence of residential and job mobility

an eoq model with backorders and rejection of defective supply batches abstract we consider a single echelon inventory installation under the classical eoq with backorders paradigm to study the effects of supply quality on cost performance previous research on imperfect supply quality has focused on variants of the proportional deterministic or random yield problem where supply batches are all accepted and then used after screening any defects in this paper we study an alternative setting where entire supply batches may be defective below quality standards and therefore rejected on arrival note that such supply flow disruptions are analogous to those considered within the economic order quantity with disruptions eoqd area of research we first present an exact model for the system expected cost and show its convexity optimal cost and respective values of the decision variables i e planned order quantity and backorders are then obtained in a closed form interestingly under perfect supply quality all expressions reduce to those of classical eoq analytical and computational results reveal the serious impact of inferior supply quality on system cost as well as the sensitivity of the system parameters

optimal control of a two station tandem production inventory system a manufacturing facility consisting of two stations in tandem operates in a make to stock mode after production items are placed in a finished goods inventory that services an exogenous poisson demand demand that cannot be met from inventory is backordered each station is modeled as a queue with controllable production rate and exponential service times the problem is to control these rates to minimize inventory holding and backordering costs optimal controls are computed using dynamic programming and compared with the kanban basestock and buffer control mechanisms that have been proposed for manufacturing facilities conditions are found under which certain simple controls are optimal using stochastic coupling arguments insights are gained into when to hold work in process and finished goods inventory comparable to previous studies of production lines in make to order and unlimited demand environments

optimal lot sizing in an imperfect production system with homogeneous reworkable jobs abstract we consider a lot sizing problem in a single stage imperfect production system where the job processing is failure prone the processing may generate two types of defects 1 reworkable defects which must be sent back for rework 2 nonreworkable defects which are discarded immediately the production process will switch between new jobs and rework jobs both new job processing time and rework time are random we discuss the optimal lot sizing control under a class of operating policies to maximize the average profit over an infinite time horizon we establish the existence of an optimal lot size furthermore we characterize the profit function through the discussion we obtain a very efficient algorithm for determining an optimal lot size

strategic policy and the logistics of crude oil transit in lithuania this paper examines the crude oil transit market in lithuania and the significant economic and political role played by russia beginning with an analysis of the strategic and political role played by crude oil in lithuania there follows a discussion of the policies followed by the lithuanian authorities following independence in 1992 from the former soviet union a content analysis approach is taken to establishing the main policy issues that dominate the sector this technique combines both quantitative and qualitative approaches to a review of published material on oil transit in lithuania and acts as a means of assessing expert opinion on the issues involved the results from this analysis will be used in developing policy initiatives for the sector the paper ends with some suggestions for further applications of the techniques used to oil transit policy issues in the region

economic production quantity model for items with imperfect quality abstract the assumptions necessary to justify the use of economic production quantity epq eoq models are rarely met to provide mathematical models that more closely conform to actual inventories and respond to the factors that contribute to inventory costs the models must be extended or altered this paper hypothesizes a production inventory situation where items received or produced are not of perfect quality items of imperfect quality not necessarily defective could be used in another production inventory situation that is less restrictive process and acceptance control the electronics industry gives good examples of such situations this paper extends the traditional epq eoq model by accounting for imperfect quality items when using the epq eoq formulae this paper also considers the issue that poor quality items are sold as a single batch by the end of the 100 screening process a mathematical model is developed and numerical examples are provided to illustrate the solution procedure

economic order quantity for items with imperfect quality revisited abstract we rectify a flaw in an economic order quantity eoq model with unreliable supply characterized by a random fraction of imperfect quality items and a screening process developed by salameh and jaber 2000 economic production quantity model for items with imperfect quality international journal of production economics 64 1 3 59 64 this leads to simple expressions of the optimal order quantity and expected profit per unit time we then analyze the effect of screening speed and variability of the supply process on the order quantity and show that the order quantity in our model is larger than that of the classical eoq model when the variability of the yield rate is reasonably low in addition we extend the model by allowing for several batches of imperfect quality items to be consolidated and shipped in one lot this is likely to be useful when there are economies of scale in shipping of imperfect quality items finally we present numerical results to illustrate the application of the model and draw insights

economic production quantity model for items with imperfect quality subject to learning effects abstract salameh and jaber 2000 international journal of production economics 64 59 64 developed an inventory situation where items received are not of perfect quality defective and after 100 screening imperfect quality items are withdrawn from inventory and sold at a discounted price this paper extends the work of salameh and jaber by assuming the percentage defective per lot reduces according to a learning curve which was empirically validated by data from the automotive industry mathematical models are developed with numerical examples provided and discussed the developed model was compared with the model of salameh and jaber to emphasize the importance of learning

production and replacement policies for a deteriorating manufacturing system under random demand and quality abstract this work investigates the production planning of an unreliable deteriorating manufacturing system under uncertainties the effect of the deterioration phenomenon on the machine is mainly observed in its availability and the quality of the parts produced with the rates of failure and defectives increasing with the age of the machine the option to replace the machine should be considered to mitigate the effect of deterioration in order to ensure long term satisfaction of demand the objective of this paper is to find the production rate and the replacement policy that minimize the total discounted cost which includes inventory backlog production repair and replacement costs over an infinite planning horizon we formulate the stochastic control problem in the framework of a semi markov decision process to consider the machine s history the integration of random demand and quality behaviour led us to propose a new modeling approach by developing optimality conditions in terms of a second order approximation of hamilton jacobi bellman hjb equations numerical methods are used to obtain the optimal control policies finally a numerical example and a sensitivity analysis are presented in order to illustrate and confirm the structure of the optimal solution obtained

an extension of the monocentric urban spatial equilibrium model to a multicenter setting the case of the two center city abstract firms in a monocentric city conforming in substance to the new urban economics produce an export commodity under agglomeration economies and employ homogeneous labor and capital workers reside about the cbd in decreasing densities with distance a developer establishes a second export production center within the city s residential area conditions for economic viability and growth of the subcenter are examined and its impacts on short run and long run city location patterns are discussed a limiting condition on subcenter employment size is provided

dual measures of monopoly and monopsony power an application to regulated electric utilities the inefficiency from monopoly pricing monopsony pricing and other institutional factors should be simultaneously estimated to avoid misspecification estimation of a behavioral profit function where input and output shadow prices may diverge from their market values allows unbiased simultaneous estimation of inefficiencies if its normalized form is employed in an application to electric utilities consuming western coal the authors cannot reject the hypothesis that utilities act as price takers in output markets and find weak and statistically insignificant evidence of fuel adjustment clause bias strong evidence is found of monopsony behavior in the market for western coal and its transportation copyright 1989 by mit press

optimal control and equilibrium behavior of production inventory systems the relationship between commodity inventory and short term price variations has received considerable attention but the understanding has been limited to single stage cross sectional relation in this paper we aim to deepen our understanding of the inventory price relationship in two dimensions across time and across production stages we first examine an individual firm controlling production and two stages of inventory under uncertain input and output prices and operating costs we next establish and characterize the rational expectations equilibrium for an economy in which competitive production firms link a raw material market and a finished goods market with uncertain and price sensitive supply and demand we characterize the dynamics of inventory market price and gross margin based on theoretical analysis simulation and empirical evidence from the petroleum industry we find that inventory fluctuations lag behind price variations and the length of the lags depend on how far the inventory is from the source of the supply or demand shocks we also find that shocks are both dampened and delayed when propagating through the production stages and that shocks have a prolonged effect on inventories and prices at both stages

endogenous emergence of credit markets contracting in response to a new technology in ghana abstract access to credit is important for the productivity and overall welfare of farmers in developing countries we present a theoretical framework which shows that a change in the mode of shipping from air to sea in the ghanaian pineapple industry made it profitable for pineapple exporters to provide myopic farmers with both in kind loans to improve productivity and cash loans for consumption smoothing despite being unable to monitor farmers or enforce repayment the innovative theoretical result is that providing farmers with additional cash loans can enforce greater input use without compromising repayment we provide evidence in the form of a case study documenting the dramatic rise of informal credit through contract farming after the switch to sea freight between 1996 and 2001 using this anecdote we argue that credit arrangements can arise spontaneously absent non market interventions to meet market needs even in the absence of proper legal protections for creditors

forecasting housing prices under different market segmentation assumptions three types of market segmentation strategies are available to estimate hedonic housing price models i e no segmentation segmentation by using statistical clustering methods and segmentation by using a priori information this research tests the hypothesis of tiebout theory that individual residential decision making is determined by equilibrium provision of local public goods in accord with the tastes and preferences of residents thereby sorting their housing locations into optimal sub markets forecasting accuracies of eight sub market segmentation strategies and two forecast combining methods are examined by using housing sales data from knox county tennessee usa the results provide empirical support for tiebout theory of optimal housing sub market location in that boundaries drawn using a priori information from local government jurisdictions school districts and expert opinions are more closely aligned with the equilibrium provision of local public goods than boundaries drawn by statistical cl

urban commuting journeys are not wasteful do urban workers commute too much bruce hamilton 1982 was the first to raise the question whether urban workers commuting journeys are too long or in his terms wasteful he argued that the monocentric urban model predicts that workers commuting journeys will be minimized to test the model he calculated the minimum commuting journey length for the average worker in a group of u s cities and compared the results to the actual average commuting journey length for those workers he assumed that any difference between the two figures was wasteful commuting he found that the average minimum commuting distance was only 1 1 miles but the average distance actually commuted by workers in those cities was 8 7 miles or nearly eight times as great hamilton therefore concluded that the monocentric urban model has little predictive value concerning commuting behavior and that actual commuting behavior could be predicted just as well using an assumption that commuting is random commuting behavior is a central feature of any model that purports to explain urban residential and job location choice hamilton s assertion that the monocentric urban model has little predictive value concerning commuting behavior therefore strikes at the heart of

three echelon supply chain coordination considering duopolistic retailers with perfect quality products abstract this paper explores channel coordination and profit division issues of a manufacturer distributer duopolistic retailers supply chain for a product where the manufacturer supplies lotsize of the product that contains a random portion of imperfect quality item in manufacturer stackelberg vertical game setting the duopolistic retailers three behaviours cournot collusion and stackelberg are discussed besides analyzing the effect of imperfect quality product on optimal decisions the paper depicts the hybrid contract mechanism so that all units quantity discount with franchise fee resolves channel conflict though unable to provide win win outcome for surplus profit division the paper proposes two sequential bargaining processes backward and forward where outcome of a nash bargaining is dependent on the previous it is found that for channel coordinated win win profit the manufacturer prefers collusion stackelberg and cournot while the retailer prefers the reverse and both prefer backward sequential bargaining but the distributers preference depends on the target profit that it sets during the bargaining process the proposed mechanisms are illustrated by a numerical example

economic ordering quantity models for items with imperfect quality abstract in this paper we first look at the issue of non shortages in models with proportional imperfect quality when the proportion of the imperfects is a random variable more specifically we revisit the papers of salameh and jaber int j prod econom 64 2000 59 and chan et al prod plann control 14 2003 588 and we point out that the sufficient conditions given in these papers to ensure that shortages will not occur may not really prevent their occurrence next considering the timing of withdrawing the imperfect quality items from stock we clarify a point not clearly stated in salameh and jaber int j prod econom 64 2000 59 and we extented this model to the case in which withdrawing takes place at the end of the planning horizon finally we establish that the objective of maximizing the mean average profit which was set in salameh and jaber int j prod econom 64 2000 59 is superfluous and the results given there can be obtained by ignoring the revenue issues assumed in the model and minimizing directly the mean average cost

a three input model of the spatial effects of a central city wage tax abstract this paper considers the short run and long run spatial effects on wages employment and business capital as functions of location of a localized increase in wage tax rates the model is most applicable to a central city that has a higher wage tax rate than the surrounding suburbs the inclusion of land as a third input in production significantly reduces the long run effects of a central city wage tax on employment near the central city boundary as compared with a model in which labor and capital are the only two inputs the short run effects are significantly less than the long run effects

analysis of a production inventory system subject to random disruptions in this paper we study an unreliable bottleneck production inventory system with a constant production and demand rate that is subject to random disruptions we assume that the restoration times are constant the time between breakdowns is exponential the production setup cost and or setup time is positive and excess demand is backordered we propose an s s production policy for such systems and develop expressions for the operating characteristics of the system the properties of the policy parameters that minimize the expected total cost rate are investigated and a procedure for finding their optimal values is developed in addition we devise and test a simple heuristic procedure for finding near optimal production policies the results of a numerical experiment suggest that i setup cost reduction is more effective in reducing total operating cost when the production system is more reliable ii setup cost reduction in unreliable production systems results in higher optimal safety stock level and iii proper determination of the safety stock levels is extremely important in just in time systems which are susceptible to disruptions

economic order quantity model for items with imperfect quality with learning in inspection abstract the economic order quantity eoq model is the simplest and earliest inventory model in the literature its simple mathematics is attributed to its assumptions which are rarely met salameh and jaber 2000 economic production quantity model for items with imperfect quality int j prod econ 64 59 64 addressed one of these assumptions that items received or produced are not of perfect quality this paper extends salameh and jaber s work for the case where there is learning in inspection the model is realistic in that it considers situations of lost sales and backorders mathematical models are developed with numerical examples provided and results discussed for the cases of i partial transfer of learning ii total transfer of learning and iii no transfer of learning