Actual Production Levels Research Articles

The Importance of Product Cost Rationalization to achieve a Customer Satisfaction Applied research in the Electric Cables Plant / Ur State Company

The research aims at explaining the reasons for the high cost of production and the application of modern concepts in accounting costs and administrative, which came to remove loss and waste and rationalization of costs and improve operational performance and in response to changing conditions in the business environment. As a result of these variables and circumstances, the research problem was manifested in the high cost of manufacturing the products of Ur Company, which lost competitive precedence with other products in terms of price, quality and other specifications imported from various sources. In order to achieve the objective of the research and solve the problem was developed a basic hypothesis that the use and application of modern concepts lead to rationalize the cost of manufacturing products and improve activities and processes and create a market share in the local environment. divided of research into three topics The first topic reviewed the theoretical aspect of modern concepts and competitive priorities, including rationalization of costs and removal of loss and improve performance and address the negatives in traditional concepts and methods. Either the second topic dealt with how to rationalize the cost of some of the products of the electrification plant, either the third section, he concluded with a number of results, the most important of which was the high proportion of production costs, especially the proportion of direct wage costs to the total cost of manufactured goods (37%)Very high percentage and low competitive precedence prices of local products of the company compared to the prices of imported products, and the obsolete equipment and machines in the factory. This caused a significant increase in the cost of maintenance and backup tools. A significant reduction in actual production levels from the planned annual level of energy. It is also necessary to continuously seek to reduce the production

Estimasi potensi sumberdaya ikan di perairan Kecamatan Teluk Pandan, Sangatta Selatan, Sangatta Utara dan Bengalon Kabupaten Kutai Timur

In order to reduce the exploitation of natural resources in the territorial waters of Teluk Pandan, South Sangatta, North Sangatta and Bengalon, the coastal and marine resources should be wisely exploited. It is necessary to study on the potential of fish resources in each region, so that in addition to provide opportunities to pursue economic activity in the capture sector greater, as well as to look for ways to anticipate the negative impacts of coastal and marine resource use such as avoiding physical and biological degradation. Purpose of this study was to determine the status of utilization of fish resources in the 4 districts and its adjacent waters, in order to evaluate and planning, especially about fishing, fish species and management (zoning). Study approach through field surveys and laboratory analysis (ex situ), and approach literature from civil institutions and research results for secondary data. The waters highest productivity in the waters of Teluk Pandan district with the potential density stocks of 59.169 kgs/km2, crustaceans 4,344 kgs/km2 and molluscs 297 kgs/km2, while the most minimal of fish stocks in the area Bengalon District (22.557 kg/km2). But by category mollusk biota to the highest in-stock in Bengalon District waters of 919 kg/km2, followed by South Sangatta 843 kg/km2. Status of fish resources utilization rates in Teluk Pandan District, South Sangatta, North Sangatta, Bengalon and overfishing is not biologically (Underfishing), the results of stock density estimation (total biomass) and the condition of the actual production levels.

Effects of partial quantity rationing of credit on technical efficiency of Boro rice growers in Bangladesh: Application of the stochastic frontier model

In this study, we analyzed the effects of the partial quantity rationing of credit on the technical efficiency of Boro rice growers in the Pabna district of Bangladesh. Before conducting the field survey, we designed a theoretical framework and identified farm households affected by the partial quantity rationing of credit. Data were collected from 174 Boro rice growers and analyzed in two stages, where the technical efficiency of Boro rice growers was assessed using stochastic frontier analysis, and the inefficiency effects model was then applied to evaluate determinants of the technical efficiency. The mean technical efficiency of Boro rice growers was 78%, which indicates that their technical efficiency was 22% beyond the production frontier curve. The variables comprising the household head’s age, education level, seed quality, formal training, access to the market, farm labor, tillage cost, fertilizer cost, irrigation cost, and price of seedlings significantly affected the technical efficiency of rice growers. The variables of interest comprising the rate and partial quantity rationing of credit had significant negative effects on the technical efficiency of rice growers. The findings obtained in this study will help to enhance the actual production level using the available resources and improve the food security situation in Bangladesh.

PENENTUAN TINGKAT EFISIENSI ALOKATIF DAN EFISIENSI TEKNIS PADA USAHATANI JAGUNG MANIS ( Zea mays saccharata L. ) DI KECAMATAN KUPANG TIMUR

Research about the determining of allocative and technical efficiency level of sweet corn farming in East Kupang Sub District aims to find out the effect of the use of production factors toward sweet corn production; to analyze the level of allocative efficiency of its use; and to analyze the level of production technical efficiency of sweet corn. The research location was chosen by purposive sampling with the consideration that Oesao village and Pukdale are villages where produce sweet corn in East Kupang Sub District. The sample of research respondents was taken by simple random sampling with 79 respondents consisting of 35 farmers from Oesao village and 44 farmers from Pukdale village. The collect of data had been carried out as long as February to March 2020. The reseach results showed that the factors of land, seed, and urea production significantly affected the production of sweet corn, while the factors of NPK, pesticides and labor production had no significant effect. The level of efficiency can be reached through allocate production inputs precisely. In this case, by reducing the use of land and urea fertilizer, on the other hand, by adding the use of seeds. Also, the farmer production level technically is not efficient yet with the average of actual production level is 10,408 grains or around 1,487 kg, while the average frontier production level is 28,146.64 grains or around 4,021 kg. There are 39 farmers who their technical efficiency in low level category, than, 28 farmers in moderate level category, and as many as 12 farmers have reached a level of technical efficiency.

Investigation of V–N Micro-alloying Using Nitrogen Bottom Blowing

Herein, a novel method of V–N micro-alloying was developed by adding ferrovanadium and nitrogen bottom blowing. For comparison, melting experiments were carried out by directly adding ferrovanadium nitride. Results indicate that nitrogen content increases rapidly and can reach the actual production level via nitrogen bottom blowing. TEM observations show that carbonitrides precipitate along the dislocation line, on the boundary of cementite and ferrite–cementite, and the ferrite grain boundary. Meanwhile, higher the nitrogen content in the steel, more the precipitates and higher dispersion will form, which indicates that addition of ferrovanadium first is better than blowing nitrogen first. Furthermore, the size, distribution and dispersion of carbonitrides obtained via the method of firstly adding ferrovanadium are comparable with that of directly adding ferrovanadium nitride. The results reveal that it is feasible to realize V–N micro-alloying by adding ferrovanadium and nitrogen bottom blowing.

Yield gap analysis simulated for sugar beet-growing areas in water-limited environments

Abstract Sugar beet is one of the main two field crops cultivated to extract sugar. In order to increase the production of sugar beet, it is necessary to identify limiting and reducing factors by quantifying and analyzing yield gap. For this purpose, a crop simulation model was evaluated and used to simulate the storage organ of the sugar beet as well as yield gaps due to water shortage, inappropriate sowing date, and other biotic and abiotic factors at 10 locations of Khorasan Razavi province in northeastern Iran. Results of long-term simulations indicated that the province has a good potential for sugar beet yield with the highest yield of 103.6 t ha−1. However, there is a huge difference between actual production level and simulated attainable one (65.4 t ha−1); the average actual yield was only 32.7 % of the simulated attainable yield. In spite of the large amount of water applied as irrigation by most farmers, there are still water limitations because of water mismanagement, high vapor pressure deficit, and the temperatures occurring during most sensitive the major sugar beet growth stages at most locations. On average, water limitation had a major influence on yield gap (47.5 % of total yield gap) compared with sowing date (15 %) and other limiting and reducing factors (37.5 %). Under these circumstances, farmers must focus on increasing the water productivity of the sugar beet agroecosystem by replacing the current furrow irrigation systems, sowing earlier crops, and substituting sugar beet with crops that have a shorter growing season and are better adapted to the hot and arid climate during summer.

LiGAPS-Beef, a mechanistic model to explore potential and feed-limited beef production 1: model description and illustration

The expected increase in the global demand for livestock products calls for insight in the scope to increase actual production levels across the world. This insight can be obtained by using theoretical concepts of production ecology. These concepts distinguish three production levels for livestock: potential (i.e. theoretical maximum) production, which is defined by genotype and climate only; feed-limited production, which is limited by feed quantity and quality; and actual production. The difference between the potential or limited production and the actual production is the yield gap. The objective of this paper, the first in a series of three, is to present a mechanistic, dynamic model simulating potential and feed-limited production for beef cattle, which can be used to assess yield gaps. A novelty of this model, named LiGAPS-Beef (Livestock simulator for Generic analysis of Animal Production Systems – Beef cattle), is the identification of the defining factors (genotype and climate) and limiting factors (feed quality and available feed quantity) for cattle growth by integrating sub-models on thermoregulation, feed intake and digestion, and energy and protein utilisation. Growth of beef cattle is simulated at the animal and herd level. The model is designed to be applicable to different beef production systems across the world. Main model inputs are breed-specific parameters, daily weather data, information about housing, and data on feed quality and quantity. Main model outputs are live weight gain, feed intake and feed efficiency (FE) at the animal and herd level. Here, the model is presented, and its use is illustrated for Charolais and Brahman × Shorthorn cattle in France and Australia. Potential and feed-limited production were assessed successfully, and we show that FE of herds is highest for breeds most adapted to the local climate conditions. LiGAPS-Beef also identified the factors that define and limit growth and production of cattle. Hence, we argue the model has scope to be used as a tool for the assessment and analysis of yield gaps in beef production systems.

Does partial quantity rationing of credit affect the technical efficiency of dairy farmers in Punjab, Pakistan?

PurposeThe purpose of this paper is to empirically investigate the effect of partial quantity rationing of credit on the technical efficiency of dairy farmers in the Punjab province of Pakistan.Design/methodology/approachPrior to the field survey, the authors constructed a theoretical model for clear identification of partial quantity rationed dairy farmers. Data from 154 dairy farmers were collected that represented three districts of the province. The collected data were analyzed in two stages: first, the efficiency level of dairy farmers was estimated using a stochastic frontier approach; second, the authors employed an inefficiency-effects model to estimate the effect of partial quantity rationing of credit on technical efficiency.FindingsThe results revealed that education level of the household head, cross-breed and imported cattle, and electric chaff cutter, all had significant positive impacts on technical efficiency, followed by diversified sources of income. Conversely, the analysis of our key variables, interest rate on principal amount and partial quantity rationing of credit had significant negative effects on the technical efficiency of dairy farmers in selected districts of the Punjab province in Pakistan.Originality/valueThe study will be an important contribution to the existing credit constraints and technical efficiency literature and will particularly help the rural financial institutions in terms of approving the loan amount according to the actual requirements of the borrowers. The study’s findings and subsequent recommendations will be useful for policy makers in achieving the actual production level, bringing down the poverty levels and ensuring food security in the country.

Farmers land tenure arrangements and technical efficiency of growing crops in some selected upazilas of Bangladesh

There are different land tenure arrangements in crop cultivation in Bangladesh. It is needed to detect how farmers could maximize the benefits from proper utilization of their resources and technologies in these prevailing different land tenure arrangements in crop cultivation. The main quest of this study is to analyze the actual production level and how much is deviated from maximum attainable production level in terms of technical efficiencybased on average gross revenue of output ha-1 in the cultivated various types of crops among different categories of farmers and identifies the impact of the factors associated with technical efficiency.In search of this research question a case study was conducted in two Upazilas (Sub districts) in Bangladesh based on cross section data. This data were collected from January to March, 2013. Age of the household head, education, farm size, off-farm income and other concerned issues were assessed. Maximum likelihood estimation and ordinary least square regression techniques were used to estimate the parameters of the stochastic production frontier.Ordinary least square regression was used to identify the factors associated with technical efficiency. The study reveals that the technical efficiency varied among different categories of farmers. But land rent (0.0575) and weed management (0.0838) had significant positive impact on technical efficiency. This detects the potentiality to improve the technical efficiency by taking proper measures in land tenure arrangements in consideration of land rent andprovide required weed management support for the farmers.Bangladesh J. Agril. Res. 40(3): 347-361, September 2015

Yield gap analysis in major wheat growing areas of Khorasan province, Iran, through crop modelling

To increase wheat productivity from current levels, the yield gap, the difference between actual and potential yield, should be analyzed. A crop model was calibrated for three winter wheat cultivars and validated for a major wheat growing area to evaluate yield gaps in Khorasan province in northeastern Iran. The validated model was used to simulate long-term yield for 14 locations under three management conditions (potential, water-limited, nitrogen-limited). The results showed that the average simulated potential yield of 7.8Mgha−1 has not yet been realized by farmers and there is a large gap between the actual and potential production levels (about 5.2Mgha−1). The simulation showed considerable difference between cultivars for yield gap. When averaged over locations and seasons, the total yield gap obtained for Chamran wheat was 4.4Mgha−1, for Sionz was 6Mgha−1, and for Gascozhen was 6.1Mgha−1. Across locations, the proportion of yield gap from water-limitation was 1.7% to 19.5% and for nitrogen- limitation was 40% to 47%. The gap caused by other limiting and reducing factors was 33–57%. The highest yield gap was observed in Ghaen for Gascozhen (7.6Mgha−1) and the lowest was observed in Sarakhs for Chamran (3.1Mgha−1). The results of the study suggest that the average farm yield of about 2.6Mgha−1 in irrigated fields in Khorasan province is not limited by low genetic yield potential. This indicates that farmers should emphasize more on management factors such as water availability, timing of nitrogen application, and selection of cultivars adapted for each environment to reduce yield gap.

A framework for quantitative analysis of livestock systems using theoretical concepts of production ecology

In crop science, widely used theoretical concepts of production ecology comprise a hierarchy in growth defining, limiting, and reducing factors, which determine corresponding potential, limited, and actual production levels. These concepts give insight in theoretically achievable production, yield gaps, and yield gap mitigation. Concepts of production ecology have been demonstrated to be applicable to livestock science, but so far they have not been used quantitatively for livestock production. This paper aims to define theoretical concepts of production ecology for livestock systems in more detail, to express livestock production in suitable units, and to provide a framework to analyse production levels for livestock systems and combined crop–livestock systems.Growth defining (genotype and climate), growth limiting (feed quality and quantity), and growth reducing factors (diseases and stress) in livestock production are described analogous to the growth factors in crop production. Management practices, such as housing, feeding, culling, and slaughter are specified. From the perspective of a livestock system, production is expressed per animal, per unit of animal body mass, and per unit of feed intake, whereas from the perspective of a combined crop–livestock system, production is recommended to be expressed in kg livestock product ha−1year−1.The quantitative framework is illustrated for Charolais cattle (Bos taurus subsp.) in two beef production systems in France, differing in feeding strategies. System A produces heavier calves than system B, whereas cattle in system B are fed a higher fraction of concentrates in the diet compared with system A. Potential beef production was similar for systems A and B, and estimated to be 152kgbeefanimal−1year−1 and 251gbeefkg−1liveweight year−1, while there was a minor difference when expressed per unit of feed intake (54.5 vs 54.8gbeefkg−1 DM). Actual production was lower for system A than for system B (24.9 vs 31.2gbeefkg−1 DM). Potential production for combined crop–livestock systems was again similar for systems A and B (631 vs 634kgbeefha−1year−1), while actual production was much lower for system A than for system B (133 vs 180kgbeefha−1year−1). The yield gap for crop–livestock systems was 79% of potential production for system A and 72% for system B. We conclude that the framework is effective to reveal the scope to increase production and resource use efficiency in livestock production.

China’s Grain Production: A Decade of Consecutive Growth or Stagnation?

China's official statistics showed that the country's grain production declined from 512 to 431 million tons between 1998 and 2003. However, according to the Chinese government, since 2004 it has achieved "ten years of consecutive growth" in grain production. According to the official statistics, China's grain production reached 602 million tons in 2013, nearly 40 percent above the 2003 level.… While the official statistics claim grain production has grown rapidly, China's surging imports of cereals and soybean suggest that its grain production has struggled to catch up with demand.… This article argues that China's actual grain production levels may be substantially lower than the officially reported levels; in fact, grain production has stagnated since the late 1990s.This article can also be found at the Monthly Review website, where most recent articles are published in full.Click here to purchase a PDF version of this article at the Monthly Review website.

Appropriate Separator Sizing: A Modified Stewart and Arnold Method

Oil and gas separators were one of the first pieces of production equipment to be used in the petroleum industry. The different stages of separation are completed using the following three principles: gravity, centrifugal force, and impingement. The sizes of the oil droplets, in the production water, are based mainly on the choke valve pressure drop. The choke valve pressure drop creates a shearing effect; this reduces the ability of the droplets to combine. One of the goals of oil separation is to reduce the shearing effect of the choke. Separators are conventionally designed based on initial flow rates; as a result, the separator is no longer able to accommodate totality of produced fluids. Changing fluid flow rates as well as emulsion viscosity effect separator design. The reduction in vessel performance results in recorded measurements that do not match actual production levels inducing doubt into any history matching process and distorting reservoir management programs. In this paper, the new model takes into account flow rates and emulsion viscosity. The generated vessel length, vessel diameter, and slenderness ratio monographs are used to select appropriate separator size based on required retention time. Model results are compared to API 12J standards.

Evaluation of the manufacturing of desk and stringer boards for wood pallets production by discrete event simulation

Deck and stringer boards’ manufacturing for wood pallet production requires complex management due to the variability of the logs used as raw material. An analysis was carried out on a representative sawmill in north-eastern Italy; the manufacturing line was composed of a band-saw, a cut-saw and a multi circular saw machine connected by rollers and belts conveyors provided with buffers. A discrete event simulation model was built in order to investigate the possible influence of the variability of log diameter and of the productive layout on the actual production level. The simulations showed that the major advantage could come from an improvement in the layout, identifying the cut-saw machine as the main bottleneck of the manufacturing line. By adopting a different cut-saw machine, the productivity of the manufacturing line could increase up to + 56% in the daily production of deck and stringer boards showing an increased daily productive time of + 13%. The effects of this change are evident especially for log diameters lower than 65 cm.

DO UNIONS IMPACT EFFICIENCY?: EVIDENCE FROM THE U.S. MANUFACTURING SECTOR

I. INTRODUCTION The relationship between labor unions and firm performance has garnered a vast amount of attention from scholars, unions, and businesses, as well as from policymakers as extensive studies have explored both the theoretical foundations and the empirical evidence regarding the impact of labor unions on productivity, as well as on other aspects of business, such as sales, profitability, investment, and employment growth (Doucouliagos and Laroche 2003). Perhaps one of the most relevant public policy questions is how unions affect productivity. Although studies have empirically investigated union productivity effects for a variety of industries and public sectors, particularly in the U.S. and European countries, empirical evidence on this question, however, is mixed. Brown and Medoff (1978) and Freeman and Medoff (1984), in their early and influential work, argued that labor unions can raise productivity by inducing managers to adopt more efficient production methods and policies, and by providing better communication channels between workers and management. Supporting this impression, Dworkin and Ahlburg (1985) argued that opening communication channels between management and workers can result in integrative, rather than distributive, bargaining. Allen (1984) used the example of the construction industry, and cited union hiring halls, apprenticeship programs, and managerial shock effects as the reasons for union productivity improvements. In recent years, many employers have adopted new ways of organizing work that emphasize employee involvement. Empirical evidence suggests that various human resources management practices have a positive impact on firms' productivity. Black and Lynch (2001) found that unionized plants with these new approaches to organizing work had higher productivity than other similar non-union plants. Recent studies indicate that improved productivity of firms with labor unions may reflect better human resources management practices (Bloom and Van Reenen 2007; Doucouliagos and Laroche 2006; Ichniowski and Shaw 2003; Machin and Wood 2005). However, Lewis (1963) pointed out that one of the most well-established impacts of labor unions on firms is the ability to raise wages above competitive levels. Such a monopoly power may exert adverse impacts on firm productivity by distorting the labor market. Other unfavorable effects of unions are on RD Hirsch and Link 1987; Link and Siegel 2002; Lommerud, Meland, and Straume 2006; Menezes-Filho and Van Reenen 2003). These effects can have a detrimental impact on the dynamic productivity of firms. Thus, unions can both enhance and detract from firms' productivity performance. Because of the ambiguity over the net effect of unions, an assessment of the union's effects on economic performance hinges on empirical evidence (Doucouliagos and Laroche 2003). (1) Although most literature focuses on the performance or productivity impacts of unions, a strand of literature also looks at the channels through which unions affect measured performance/productivity. Measured productivity can be decomposed into two important components: the adopted production technologies and the of utilizing the technology. The former represents a shift in the production function and the latter shows the distance between actual production level and frontier production level for given inputs. An increase in the measured productivity may result if a firm adopts a better production technology or improves technical efficiency by moving production toward the frontier level of a given technology. The arguments for or against unions regarding productivity can trace their causes to the impacts on one or both of the productivity components. For instance, the communication effect of Brown and Medoff (1978) and Freeman and Medoff (1984) results in improved in using installed technology, whereas the outcome of changing production methods, also mentioned by the same authors, amounts to choosing new production technologies. …

Growing More Potatoes with Less Water

Demand for potato is steadily rising in developing countries, where actual per-hectare production levels reach mere fractions of the yields achieved in Europe or North America. Improving abiotic stress tolerance, e.g., against drought, could increase these low potato yields and thus help to satisfy the growing demand for this crop. Hypotheses about genes and traits that could mitigate yield decreases caused by drought have been driven by information obtained from model plants and have recently been complemented with data of high throughput gene expression profiling and metabolite studies on potato genotypes under water stress. Principal tolerance traits that could diminish the vulnerability of potato yields to drought stress include improved detoxification of reactive oxygen species produced during stress, optimized stomatal control under drought to reduce water loss but at the same time allow for continuous CO2 access for photosynthesis, and mechanisms to protect proteins and membranes from damage by water stress. Candidate genes underlying these traits as well as genotypes that express them are available and, after appropriate validation, could be used for breeding.

Cyclic Just-In-Time Sequences Are Optimal

Consider the Product Rate Variation problem. Given n products 1,…,i,…,n, and n positive integer demands d1,…, di,…,dn. Find a sequence α=α1,…,αT, T=\sumi=1ndi, of the products, where product i occurs exactly di times that always keeps the actual production level, equal the number of product i occurrences in the prefix α1,…, αt, t=1,…,T, and the desired production level, equal rit, where ri=di/T, of each product i as close to each other as possible. The problem is one of the most fundamental problems in sequencing flexible just-in-time production systems. We show that if β is an optimal sequence for d1,…,di,…,dn, then concatenation βm of m copies of β is an optimal sequence for md1,…, mdi,…,mdn.

An examination of energy utilization in lactating dairy cows receiving a total mixed ration based on maize silage

AbstractSix multiparous Holstein-Friesian cows were offered a total mixed ration based on maize silage in a repeated measure design to evaluate the partition of gross energy (GE) during early to mid lactation. Four measurements were made at 6-week intervals with energy and nitrogen balances carried out in open-circuit respiration chambers over 6 days during lactation weeks 6, 12, 18 and 24. The intakes of total diet dry matter (DM) corrected for volatile losses (VCDM), organic matter (OM) and GE declined significantly (P< 0•01) as lactation progressed, although apparent digestibility of these fractions was not altered, resulting in a significant (P< 0•01) decline in digestible nutrient intake at each stage of lactation. Methane and urine energy losses were not significantly affected, resulting in significantly (P< 0·001) higher amounts of digestible energy (DE) partitioned to methane and urine as lactation progressed with associated significant reductions in metabolizable energy (ME) intake (MEI) (P< 0·01) and ME as a proportion of DE (P< 0·001) and GE (q) (P< 0·05). With advancing lactation there was a significant (P< 0·001) increase in the amount of ME partitioned to heat (HP/MEI), but no significant change in the amount partitioned to milk and tissue. Individual values for diet metabolizability (ME/GE) at actual (production) levels (qa) (mean 0·625 MJ/MJ) were corrected to an equivalent value at maintenance (qmc) (mean 0·666 MJ/MJ). The overall ME intakes (MJ/day) were: ad libitum, 246, corrected for level of feeding effect, 263, with a predicted ME requirement according to AFRC (1993) (MER93) of 242. Substitution of the calculated qmc into the predictive equations (AFRC, 1993) resulted in a mean maintenance requirement of 57·6 MJ/day (0·464 MJ/kg M0·75/day) whilst the mean value derived from the linear model describing the experimental data was 82·5 MJ/day (0·664 MJ/kg M0·75/day). The mean efficiencies of utilization of ME for milk production derived from AFRC (1993) and the linear regression model were 0·653 MJ/MJ and 0·625 MJ/MJ respectively.

Production smoothing and buffer stock reduction for two-stage production and inventory systems

This paper deals with the problem of developing an effective push-type ordering system which can decrease the variations of production ordering and inventory levels, while taking into account forecasted error, the difference between forecasted values and the backlog quantity, in which the shortage of safety stock of component parts causes a discrepancy between production ordering and actual production levels. The ordering system is developed on the basis of an idea which combines safety stock and the weight of the feedback quantity of actual and forecasted term-end inventory levels. Some results of numerical analysis show the effects of safety stock of the component parts and the feedback control parameter of each production stage, the autocorrelation coefficient of product demand upon the amplifications of production ordering and inventory levels.

A demand-to-manufacturing-requirement model based on predefined configurations

This paper examines the production planning of a job-shop manufacturing system capable of producing various part types. The demand for the various product types is known at the end of each elementary period. The objective function is the sum of inventory and backlog costs accumulated during a finite period of time known as the horizon of the problem. This horizon is a multiple of the length of an elementary period. We define the new concept of configuration as a set of maximal quantities of each type of parts which can be manufactured during an elementary period of time. This set is chosen either in order to balance the resource loading or to optimize the use of the tools available in the job-shop. We assume that there exists a finite set of configurations. The changeover of the system from one configuration to another is only allowed at the end of an elementary period and introduces a set-up time during which no machine can produce. The control of such a system consists in choosing the sequence of configurations and the actual production levels on each elementary period so as to minimize the objective function. We propose an efficient optimal algorithm for computing the actual production levels on each elementary period when the sequence of configurations (i.e. the sequence of constraints) is given. A heuristic algorithm is also proposed to find a good sequence of configurations.