Minimum Unit Cost Research Articles

Modelos determinísticos de inventarios para demanda independiente Un estudio en Venezuela

<p>El objetivo de este trabajo es analizar los siguientes modelos determinísticos de inventarios para demanda independiente: un solo lote, lote por lote, cantidad económica de pedido (EOQ), algoritmo Silver-Meal (SM), costo unitario mínimo (CUM), balanceo de periodo fragmentado (BPF) y algoritmo de Wagner-Whitin (WW).</p><p>Estos modelos surgen del supuesto clave de que la demanda conocida con cierto grado de certidumbre de un artículo que se lleva en inventario es independiente de la demanda de cualquier otro artículo que también se lleve en dicho inventario.</p><p>Con la intención de lograr el objetivo planteado, los modelos mencionados son aplicados para el cálculo de los tamaños de lotes óptimos de resmas de papel carta y oficio de acuerdo con los registros de demanda real e independiente suministrados por el departamento de Publicaciones de la Facultad de Ciencias Económicas y Sociales (FACES) en la Universidad de Los Andes (ULA), en Mérida, Venezuela.</p><p>La principal conclusión que se deriva de los resultados obtenidos es que el método de un solo lote, utilizado por la administración de la FACES, comparado con los modelos de lote por lote, EOQ, SM, CUM, BPF y WW, es el más costoso y, en consecuencia, el menos indicado.</p>

Emission and Cost Configurations in Earthmoving Operations

Brief introduction to the problem. The paper examines the influence of varying operation parameters such as equipment heterogeneity, pay load, and travel times, on unit emissions and unit costs in earthmoving and like operations. The need to minimise cost and maximise produc tion of earthmoving and like operations has led to such operations being heavily scrutinised. With environmental issues becoming more impor tant, there is now a need to additionally scrutinise and minimise emis sions. Cycle times and production were measured in a cut-and-fill case study operation; average fuel burn data are converted to idling and nonidling emission fractions; and queuing theory is used for the theoretical evaluation of production for varying operation parameters. It is demon strated that the optimum fleet sizes in terms of minimum unit costs and minimum unit emissions coincide in earthmoving operations. The result is independent of any specific operational parameters. The paper con cludes that the traditional way of undertaking earthmoving operations, namely configuring to give minimum unit costs, will also result in mini

Thermodynamic and economic optimization of a MCFC-based hybrid system for the combined production of electricity and hydrogen

In this paper, a biogas fuelled power generation system is considered. The system is based on a molten carbonate fuel cell (MCFC) stack integrated with a micro gas turbine for electricity generation, coupled with a pressure swing absorption system (PSA) for hydrogen production. The aim of this work is the optimal design of the system plant considering thermodynamic and economic objective functions. Optimization is performed by modifying the design parameters characterizing the operation of the fuel cell, the reformer and the microturbine. The corresponding costs and performances are obtained using a model developed at component level. Pinch analysis technique and a general heat exchanger network are used in order to select the optimal configuration of the heat exchangers. As a result, the Pareto front relating maximum efficiencies and minimum unit cost of electricity is obtained. The design corresponding with minimum cost of electricity, 0.036 €/kWh, is characterized by an electrical efficiency of about 0.46. The design corresponding with maximum efficiency, about 0.62, is characterized by a unit cost of electricity of 0.055 €/kWh. In the last part of the paper the effects produced by single variation of the design variables on unit cost of electricity and electrical efficiency are discussed.

Information system for flight disruption management

Airlines operate in a macro-economic environment characterised by stiff competition and stringent regulatory constraints. Disruption management can play a key role to assist the industry towards a minimum unit cost. This paper investigates communication process business drivers required for flight operations and disruption management. The disruption management in the company under study (Emirates airlines) is studied in order to derive an operational strategy in which input resources and transformation process are reconsidered to deliver effective output services to passengers. Effects of different types of flight disruptions are studied and the role of Network Control Centre (NCC) is identified through subsequent stages. A Management Information System (MIS) approach is proposed to offer solutions to disruption management. The flight disruption at the company are analysed along with their impacts on airport, aircraft and passengers through a case study.

Targeting for Multiple Resources

The source composite curve is useful in simultaneously setting targets for the minimum freshwater requirement and minimum effluent treatment. The source composite curve also helps in reducing waste production for a variety of applications. In this paper, a methodology is developed to target multiple resources through the source composite curve in order to minimize the operating cost of the overall process. It is observed that it is not necessary to maximize the usage of the resource with the minimum unit cost. Hence, a prioritized cost for each resource is devised to select appropriate resources that minimize the operating cost subject to the availability of the resources.

Use of continuous simulation for the selection of an appropriate urban rainwater tank

Household rainwater tanks form part of an integrated urban water cycle management system, which is a key aspect of the water sensitive urban design philosophy. They provide scope for harvesting rainwater for domestic uses, as well as mitigating the impacts of urbanisation on catchment runoff. This paper describes the development and application of a computer simulation model for the operation of a household rainwater tank. The model uses daily rainfall and consumption data to simulate the operation of the rainwater tank. The simulation model has been applied to a hypothetical household and rainwater tank system using daily rainfall data for 12 cities throughout Australia. The study indicates that the unit cost of supplying rainwater to a household from a rainwater tank increases as the consumption rate decreases. An economic optimum size rainwater tank, based on the minimum unit cost of rainwater supplied can be determined for any water consumption scenario. The climate characteristics of the site are shown to have a significant influence on the hydrologic effectiveness of the rainwater tank system. The study has shown that the yield of rainwater from the tank is a function of the monthly variation in rainfall, defined by the seasonality index, the median annual rainfall and the tank volume. This may have significant consequences on the suitability of rainwater tanks in terms of potential effects of climate change.

Cold Sizing of Cold- and Hot-Formed Gears

Today's markets require industrial forgers to manufacture complex near net shape or net shape parts at minimum unit costs. One way of meeting this challenge is to combine a cold or hot forming process with a subsequent cold sizing process in order to achieve the desired tolerances. In this context, a closed-die cold sizing process of a straight-toothed planetary gear has been investigated in terms of the occurring elastic die deflection which is a threat to accuracy in this and any other cold forming process. Two strategies have been employed to minimize the elastic die deflection. The first strategy consists in a correction of the die cavity's tooth profile based on the finished part's deviation from its theoretical shape determined through Finite-Element-Analysis (FEA). The key idea underlying the second strategy is an innovative tooling concept which compensates the elastic die deflection by means of a counter pressure generated by an elastomer ring embedded in the lower die. The advantages of this active concept have been confirmed in numerical and experimental investigations.

A preliminary casemix classification system for Home and Community Care Clients in Western Australia

political and policy settlement further institutionalised surveillance as the basis of the MCHS. The restructured Service has remained constrained by the dominance of health surveillance as the primary program goal even after more varied contracting arrangements replaced CCT. Although recent initiatives indicate signs of hange, narrow surveillancebased guidelines for Victorian MCH Services are not consistent, we argue, with recent early years of life policy which calls for approaches derived from socio-ecological models of health.

Selection of opencast mining equipment by a multi-criteria decision-making process

Sophisticated, capital-intensive, high-capacity earthmoving machinery is now being used in opencast coal mines to meet demand in the face of increasing pressure from competitors. The selection of equipment for coal extraction and overburden removal is a determining factor in the viability and profitability of an opencast operation, seeing that extraction and haulage account for 50–70% of the total costs.1 Mines can achieve the targeted production at the minimum unit cost and gain a competitive edge through selection of the most appropriate equipment. The selection of equipment for mining applications is not a well-defined process and because it involves the interaction of several subjective factors or criteria, decisions are often complicated and may even embody contradictions. Traditionally, procurement costs become elevated through a system of public tendering to appear as the primary criterion and the major costs of looking after the equipment during its useful life are not taken into account.2,3 The cheapest procurement, however, is not always the best and the most economic approach. Life-cycle cost (LCC) analysis helps mine management to justify equipment selection on the basis of the total costs over its useful life rather than the initial purchase price. Rao and co-workers4 and Sharma5 have presented accounts of the methodology for mining equipment selection through LCC analysis. LCC analysis again considers only the cost parameters of similar equipment and other parameters are either predetermined or not considered. Various types of cost model have been proposed for applicaton to the selection of mining equipment.6–9 Hrebar6 and Sevim and Sharma7 used net present-value analysis for selection of a dragline and surface transportation system. Use of a linear breakeven model has been proposed.8 Models for equipment selection and evaluation described by Celebi9 were aimed at selection of the equipment fleet on the basis of minimizing the unit stripping cost and maximizing production. Linear programming10 and decision-making tools11 may be applied. General guidelines and a survey related to the selection of surface mining equipment were discussed by Martin et al.12 and Srajer et al.13 and Chanda14 reviewed the fundamental concepts of equipment selection. Erdem and coworkers presented an extended bench model by means of which the optimal dragline selection may be made.15 Hall et al.16 illustrated how reliability analysis can provide mine management with quantitative information of value for decision-making about surface mining equipment. Some researchers1,17,18 have advocated the use of knowledge-based expert systems. The application of modelling in the selection of a suitable equipment fleet was discussed by Sturgul and Jacobson19 and simulation in the context of selecting an ore haulage system was reported by Lebedev and Staples.20 Most of these decision-making tools either rely on objective input data, with little or no subjective judgement, or focus on a single parameter. Multi-criteria decision-making (MCDM) techniques, such as the Analytical Hierarchy Process (AHP), can, however, be very useful in encompassing several subjective criteria with conflicting objectives to arrive at an eclectic decision. Whereas AHP is well-established as an operations research technique for decision-making in engineering applications,21–24 there has been a dearth of development and application to mining problems. A method of selecting heavy earthmoving machinery for opencast mining use has now been developed on the basis of AHP and is presented here.

Concurrent Development of Education Policy and Industrialization Strategies in Korea (1945-95): A historical perspective

This article attempts to explore what specific features of Korean education have contributed to economic development in Korea over the period of 1945-95 from a historical perspective. The key point for the successful linking of education to economic development in Korea lies in the choice of educational policy relevant to its stage of industrialization. The policies of sequential educational expansion by the school level which enables basic education to be universalized early and rapidly were very efficient in supplying manpower with unskilled but qualified manual workers in the early and middle stages of labor-intensive industrialization. So too were the financial policies which accommodated the maximum number of students in schools while minimizing the unit cost under the extremely tight financial constraints. However, cheap education carried out by the minimum unit cost would become an obstacle for continuous economic development in the knowledge, information- and technology-intensive economy surrounded by competitive international environment .

An equipment selection and cost analysis system for openpit coal mines

Turkish Coal Enterprises (TKI) is the largest coal producer of Turkey, The majority of coal stripping is done by private contractors and the decision for a contractual agreement is dictated by two relevant problems. The first problem is selection of size, type and number of major equipment that would yield the minimum unit cost for a stripping job. The second problem requires determining whether the given stripping job can be completed by the due date using whatever equipment is available to the contractor. The latter case considers the situation where the contractor's equipment is not the optimum but the job can still be finished with less profit. Two optimization models are developed to overcome these problems. To establish efficient and practical criteria for the selection of excavation method, an extensive study is carried out in the surface coal mines of Turkish Coal Enterprises and the diggability classification developed as a result of this study is the basis of the models. The first model is the equipment selection model that aims to select the equipment fleet minimizing the unit stripping cost. The second model is the equipment evaluation model that aims to maximize the production done with a given equipment fleet. The models assume that the stripping is done by excavator-truck system. Besides the loading-hauling operations, material preparation and the activities required in the dump area are also handled by the models in order to evaluate the overburden removal operation as a whole.

A NONLINEAR MODEL FOR CAPACITY ALLOCATION AND THROUGHPUT DETERMINATION IN CELLULAR MANUFACTURING SYSTEMS

The ability of modern manufacturing systems to be operated profitably at different output levels (volume flexibility) is one of their advantages. With volume flexibility, the decision maker must decide on time capacity allocation among products and the throughput of the manufacturing system for each. When sufficient time capacity to produce at throughputs that minimize unit costs exists, the problem is solved by doing so. The problem is more difficult when time capacity is insufficient to produce at throughputs resulting in minimum unit costs. In this paper, a product mix problem (PMP) for cellular manufacturing systems is formulated. The decision variables of the PMP are: a) the time capacity to allocate to each product, and b) the throughput of the manufacturing cell for each product. A polynomial time algorithm to solve a special case of the PMP is developed and the results are illustrated with numerical examples.

Tool Status Recording and Its Use in Probabilistic Optimization

In batch production, recording the status of cutting tools and making decisions based on current tool status are important issues. In flexible manufacturing systems, there are normally many tools installed on machining centers. These tools are often used on different operations due to frequent change over in the system. The tool usage recording and the decision making based on tool status in this environment are crucial. The commonly adopted time measure is not sufficient because tool life is influenced by many factors. A tool status measure (tool wear index) is introduced in this paper. The index is affected by both direct cutting time and the type of cutting involved. Tooling cost recovery and probabilistic models are also developed to identify the cutting speed and replacement time based on tool wear index for minimum unit cost. The objective is to minimize the unit direct machining cost due to tooling, machining time, and in-process tool failure penalty.

Optimal machining conditions with dual criteria and applications to scheduling

A bicriterion machining economics problem is presented, considering the minimization of the unit production cost and the maximization of the production rate. The bicriterion machining time is first defined as a weighted average of the maximum production rate machining time and of the minimum unit cost machining time using a weighted-sums technique and an arbitrary weighting factor. Then using a vector-maximum approach, a bicriterion machining lime is defined through the introduction of an optimal weighting factor. This weighting factor reflects the relative importance of the two criteria and it is a function of the delay time cost, that is, the cost associated with the difference in actual processing times between the two criteria. It is shown that the vector-maximum approach outperforms the weighting-sums technique. Furthermore, the bicriterion machining lime leans towards the maximum production rate machining time as the delay time cost increases. It is also shown that the actual processing time is prop...

Financial selection of rotation age for SRIC plantations

Short rotation intensive culture (SRIC) plantations, established in central Pennsylvania, were analyzed to determine their economic optimum rotation age. The general management design for the plantations used fertilized and non-fertilized strategies, a tree spacing of 0·48 m 2 and a rotation length of 4 years. A stand-level financial model analyzed the unit cost of production for alternate rotation lengths based upon the plantation's investment and operating costs and resulting biomass yields. Analysis of the first two rotations indicated that the minimum unit cost for fertilized and non-fertilized strategies was in the fourth year of the first rotation and the third year of the second rotation. Growth curves for the rotations also showed a maximum volume production at the same points in the rotations. Selection of a 3-year rather than 4-year harvest during the second rotation would reduce unit costs by 14% in the non-fertilized strategy and by 15% in the fertilized strategy.

Optimum Penetration of Friction Piles

How deep and how hard should a friction pile be driven to achieve the minimum unit cost of bearing capacity? The tradeoffs are modeled in terms of optimum depth of penetration limited by: (1) Available order length; and (2) allowable blow count on the last foot of penetration. Usually, it will prove cost effective to drive the longest pile available as deep and as hard as possible no matter how much time is required, as long as the pile is not damaged. There exists a narrow range of conditions where this approach is contraindicated. A suitable formula for finding the optimum depth of penetration within the range is derived. The increase in blow count with increased penetration is developed as gradient r*. As a dimensionless factor, this parameter is a relative measure of the resistance of soil to penetration. Among other uses it is a measure of work. This factor can also be expressed in blows per foot (meter) per foot (meter). In this context, it is used with the formula for finding the optimum depth of p...

The socioeconomic burden of Huntington's chorea in South Wales.

SummaryAn unselected group of 92 patients, suffering from Huntington's chorea in South Wales, has been studied in relation to the effects of the disease on employment, need for hospitalization, and the financial burden to the state. Results are compared with data from a matched control group. The difficulties of costing are discussed: a total figure of £21,500 is estimated to be the minimum unit cost per patient in 1980.

Optimum Size of Equipment

Generally speaking, equipment of greater capacity yields lower unit costs than does equipment of lesser capacity. However, this is not true when the equipment is employed in an operation consisting of at least one activity that is independent of and at least one other activity that is dependent on the size or capacity of the equipment relative to combined output. In this case there exists an optimum size or capacity of the equipment that yields the minimum total unit cost for the combined independent and dependent activities. These relationships are explored herein and the equation for finding the optimum size or capacity of the equipment is derived. An example gives the economical size of the backhoe used both to excavate the trench and lay the pipe for a storm sewer pipe culvert.

FINANCE AS AN INDUSTRY: A SIMPLE MODEL OF GROWTH*

THE PURPOSE of the dissertation is to integrate financial intermediation into a theoretical model of real economic output and growth. The methodology involves construction of a model in which capital accumulation is based upon an interest-elastic demand for the capital stock. This model is shown to be capable of adjusting to an equilibrium capital intensity and saving share. To this growth model is added a financial intermediary sector to form a two-sector model of an economy. The production sector uses real inputs of capital and labor to produce a homogeneous good which is then allocated to consumption and real capital accumulation. The financial intermediary sector uses real inputs of capital and labor to produce financial intermediary services. Financial intermediary output is described by a production function for the financial intermediary in which real capital and labor inputs are related to the units of real capital placed by the financial intermediary with production sector firms. That is, for each unit of real capital used to produce the homogeneous good, the financial intermediary expends real resources of capital and labor to gather capital from surplus households in order to place this capital with deficit production units. It is assumed that at the firm level the financial production functions exhibit the usual decreasing average product after some point, which leads to increasing average unit costs. At the aggregate sector level the financial production function exhibits constant returns to scale and constant unit costs, as expansion is carried out by the introduction of new and similarly efficient financial intermediaries. The financial intermediary thus employs real capital and labor in profit-maximizing quantities and pays these factors the competitive factor returns. The intermediary pays deposit rates to attract deposit capital which it then lends to production sector units and earns a loan rate equal to the marginal product of capital. The financial intermediary earns unit revenues equal to the difference between the loan rate and deposit rate. This quantity, called the unit cost of finance, is a per period rate per unit of capital. Total revenues of the intermediary are then composed of these per unit charges. When competition prevails in the financial intermediary market for deposit capital the intermediary is forced to pay a high enough deposit rate so that the intermediary merely covers its real factor input costs. The intermediary thus is capable of adjustments in deposit rates and factor inputs; and in a competitive equilibrium situation it produces financial services at minimum average costs. The deposit rate in a competitive equilibrium is then equal to the production sector marginal product of capital (loan rate) less the minimum average unit cost of financial services. The solution for the variables of the system are determined by a simultaneous solution of the sectoral production functions, the capital demand function (saving function), and capital and labor allocation equations (perfect substitutability). The model is solved for the sectoral capital intensities, the distribution of labor and capital between sectors, the real rates in the system (deposit rate and marginal product of capital), as well as aggregate and per capita income, investment and consumption.

A Note on the Elasticity of Derived Demand in the N-Factor Case

Many years ago, Alfred Marshall gave four rules which purported to show how the elasticity of derived demand for a factor of production depended on various parameters [6, p. 385].2 These laws of derived demand were re-stated by Pigou [12, pp. 682-5], and in 1932 Hicks developed a formula which gave the price elasticity of derived demand for a factor of production in terms of the price elasticity of demand for the product, the price elasticity of supply of a competing factor, the first factor's share and the elasticity of substitution between the two factors [3, pp. 241-6], and Hicks used his formula to test the validity of Marshall's four laws. As articles are still being written on the Hicks formula (see Bronfenbrenner [2] and Muth [11]), it may be of some interest to see how the formula stands up when the number of factors is greater than two. Also, since Hicks's derivation of his ingenious formula is somewhat hard to follow, it may be of some interest to use a rather different technique in our derivation. We assume that the production of output y is subject to the constraints implied by an N factor, constant-returns-to-scale production function f(x1,..., XN); that producers take input prices p1,..., PN as fixed and competitively minimize the cost of producing a given output level y; that producers sell output at a price equal to minimum unit cost; and that industry output is determined by the condition that demand and supply of output be equal. Since each producer's technology is represented by the same constantreturns-to-scale production function, it is well known that even though industry output may be perfectly well determined, the output of each individual producer is not. In what follows, we aggregate the individual producers into a single industry producer and develop our formula for the elasticity of derived demand assuming a constant-returns-to-scale industry production function. Let us define the industry unit cost function by c(p1, .. ., PN). This function tells us what the minimum cost of producing one unit of output is when input prices are PI, * . * PN.3