• 한국가금학회지
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• 제8권1호
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• pp.25-30
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• 1981

This study was conducted to find the method that the least-cost formula can be determined thus allowing a better keeping of raw material supplies under the constraints having to be used some raw materials that are either in limited supply or for other reason in restricted use. In this study, it was considered that three kinds of feed were produced under limited supply of six kinds of raw materials, and data for the analysis were collected from a feed mill in southern part of Korea. According to the result of this study, it was proved better to determine the least-cost formula as the multi-mix problem than as the simple least-cost problem when more than two kinds of feed were produced wilt limited supply of raw materials.

• 한국시뮬레이션학회논문지
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• 제16권1호
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• pp.1-9
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• 2007

고속 네트워크에서 QoS 라우팅은 수많은 사용자의 요구를 만족하기가 매우 어렵다. 네트워크의 경로설정 알고리즘에서 측도로써 단지 링크지연시간만을 고려한다면 그 경로는 최소지연시간 경로가 될 것이며, 링크비용만을 고려한다면 최소비용경로를 찾을 것이다. 지연시간 한계의 최소비용(Delay Constrained Least Cost; DCLC)문제는 NP-hard 문제로 알려져 있으며, 두 개의 인자 경로비용과 지연시간을 혼합한문제로 생각할 수 있다. 경로설정 시 최소지연시간을 생각하면 그 경로는 상대적으로 높은 비용의 경로이며, 반대로 최소비용만을 생각하면 그 경로는 상대적으로 높은 지연시간을 얻는다. 따라서 DCLC문제를 풀기위해서는 단 하나의 인자만을 고려해서는 안 되며 두 개의 인자를 동시에 고려할 수 있는 새로운 인자를 요구하게 되었다. 따라서 본 논문에서는 DCLC 문제를 풀기위해 경로비용과 지연시간을 동시에 확률적으로 고려한 새로운 인자를 소개한다. 시뮬레이션 결과는 새로운 인자가 DCLC 문제에 적절하다는 것을 보여주었다.

• 인터넷정보학회논문지
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• 제8권1호
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• pp.25-31
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• 2007

특정 시간 내에 데이터 전송이 이루어져야 하는 실시간 멀티미디어 응용 서비스의 특성은 네트워크의 QoS(Quolity of Service) 보장을 위한 중요한 요소이다. 종단간(End-to-End) 지연시간 제한 조건을 만족하면서 최소 비용을 갖는 (Delay Constrained Least Cost, DCLC) 경로를 찾는 문제는 이미 NP-hard 문제로 알려져 있다. DCLC 문제의 해법은 경로 지연시간과 비용간의 적절할 선택으로 해결하야 한다. 그러나 최적에 가까운 알고리즘으로 알려진 Salama의 DCUR 알고리즘(1)은 알고리즘의 단순성을 위하여 임의의 노드에서 경로 선정 시 목적 노드까지의 최소 비용 경로나 최소 지연시간 경로상의 다음 노드로만 제한을 하여 라우팅 경로의 비용측면에서 다소 비효율적이다. 일반적으로 최소 지연시간 경로의 비용은 최소 비용 경로의 비용보다 상대적으로 높은 경로 비용을 갖으며, 역으로 최소 비용 경로의 지연시간은 최소 지연시간 경로의 지연 시간보다 상대적으로 높은 지연시간을 갖는다. 본 논문에서는 이러한 점에 착안하여 DCLC문제를 해결하기 위해 확률적 주정 기법을 사용한다. 최근 발표한 독립적 두 변수간의 확률적 조합 알고리즘은 이러한 현상을 극복하기에 충분한 알고리즘이다(2). 따라서 확률적 새로운 변수에 기반한 경로 추정 기법을 사용하였으며, 그에 대한 성능평가를 하였다.

• 한국환경복원기술학회지
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• 제11권3호
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• pp.94-106
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• 2008

As populations inhabiting in natural ecosystem are fragmented by artificial barriers and habitats are destructed by development, extinction possibility of species is getting higher. It is necessary to design and to manage conservation areas and corridors considering animals' movement and migration for sustainable species diversity in present circumstances. 'Least-cost modeling' is one commonly employed approach in which dispersal costs are assigned to distinct habitat types and the last-costly dispersal paths among habitat patches are calculated using a geographical information system (GIS). This study aims to design ecological corridor using least-cost path method and to apply it to a regional ecological network considering movability of medium-large size mammals. This study was carried out over the metropolitan area, which has been deforested by rapid urbanization. Nevertheless there is connected with Gangwon province, Baekdudaegan mountain range and DMZ, considered where many forest species can migrate to this region. This study employs such an approach to develop least-cost path models for medium-large size mammals, have inhabited for this entire region. Considering those species, two forest areas as a source of species supply and forest areas more than 1,000ha are selected as focal forest areas. Movement and migration paths from species supply sources to focal forest areas are calculated by applying landscape permeability theory using land cover map, road density map and land slope map. Results showed least-cost paths from species supply sources to focal forest areas on two species. Wildcat and roe deer are different in some least-cost paths caused by their landscape permeability but paths show generally same specifics. The result of considering regional distribution of expected movement and migration paths to regional ecological network, low altitude mountains of western metropolitan area are evaluated important area for species connectivity. In national or regional levels ecological connectivity is essential to promote species diversity and to preserve integrated ecosystem. This study concludes that developing least-cost models from similar empirical data could significantly improve the utility of these tools.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 A
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• pp.106-109
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• 1992

This paper Introduces the concept of the generation cost of generating utilities and its calculation methods. Also, the economic evaluation method using generation cost which is called as a screening curve method will be presented along with the benefits and disadvantages of this concept. Next, the least-cost electric utility planning techniques which is used very widely in many countries will be Introduced In comparison with screening curve method. In this aspects, the optimal dynamic mix can be determined as a result. By comparing these two concepts, we will get the concrete concept why the economic evaluation method using generation cost can not be used for the future generation expansion planning.

• 환경영향평가
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• 제17권2호
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• pp.133-141
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• 2008

The loss, alteration, and fragmentation of habitat have led to a reduction of biodiversity. The growing awareness of the negative effects of habitat fragmentation on natural systems has resulted in conservation strategy that is concerned with not only population and habitat level but also ecosystem and landscape level. Especially, ecological network to link core areas or major habitat patches is one of the most important issues. Recently, landscape connectivity is increasingly used in decision making for fragmented landscape management in order to conserve the biodiversity in the regional scale. The objective of this study was to find potential forest as a ecological corridor in Go-yang city, Gyung-gi province using cost-distance modelling method that can measure connectivity based on animal movement. 'Least cost-distance' modelling based on functional connectivity can be useful to establish ecological network and biodiversity conservation plan. This method calculates the distance modified with the cost to move between habitat patches based on detailed geographical information on the landscape as well as behavioural aspects of the animal movement. The least cost-distance models are based on two biologically assumptions: (1) dispersers have complete knowledge of their surroundings, and (2) they do select the least cost route from this information. As a result of this study, we can find wildlife moving route for biodiversity conservation. The result is very useful for long-term aspect of biodiversity conservation plan in regional scale, because this is reflection of geographical information and behavioural aspects of the animal movement.

• Computers and Concrete
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• 제23권6호
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• pp.433-444
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• 2019

As rice husk ash (RHA) is not produced in controlled manufacturing process like cement, its properties vary significantly even within the same lot. In fact, properties of Rice Husk Ash Based Concrete (RHABC) are largely dictated by uncertainty leading to huge deviations from their expected values. This paper proposes a Robust Cost Optimization (RCO) procedure for RHABC, which minimizes such unwanted deviation due to uncertainty and provides guarantee of achieving desired strength and workability with least possible cost. The RCO simultaneously minimizes cost of RHABC production and its deviation considering feasibility of attaining desired strength and workability in presence of uncertainty. RHA related properties have been modeled as uncertain-but-bounded type as associated probability density function is not available. Metamodeling technique is adopted in this work for generating explicit expressions of constraint functions required for formulation of RCO. In doing so, the Moving Least Squares Method is explored in place of conventional Least Square Method (LSM) to ensure accuracy of the RCO. The efficiency by the proposed MLSM based RCO is validated by experimental studies. The error by the LSM and accuracy by the MLSM predictions are clearly envisaged from the test results. The experimental results show good agreement with the proposed MLSM based RCO predicted mix properties. The present RCO procedure yields RHABC mixes which is almost insensitive to uncertainty (i.e., robust solution) with nominal deviation from experimental mean values. At the same time, desired reliability of satisfying the constraints is achieved with marginal increment in cost.

• Journal of Biosystems Engineering
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• 제7권1호
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• pp.42-52
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• 1982

This study was intended to develop a cost function for the natural air in-bin drying: system which could lead to an optimization of the drying system cost. Based on the cost function developed, a series of simulated drying tests were conducted with 10-year weather data (1970~1979) for 7 different regions by applying an appropriate levels of system factors. System performance factors treated in this study were initial moisture content, airflow rate, bin diameter and grain depth. An optimization procedure to find the least cost system was developed as follows: First, the worst year of the past decade was determined in consideration of the dryiang time and maximum dry matter loss. Second, the minimum airflow rate for a fixed bin diameter and grain depth was determined. Third, the optimum grain depth was found for the minimum airflow rate with different initial moisture contents and bin diameters. The results obtained in this study are summarized as follows: 1. The optimization procedure developed in this study was able to reduce the time and efforts significantly. 2. Optimum values of drying parameters including airflow rate, grain depth, and fan size were determined for different initial moisture contents and bin diameters in each region. The results are shown in Tables 3 to 9. 3. Optimum grain depths decreased as the initial moisture content and airflow rate increased. 4. Drying time for the least cost system should be reduced with higher initial moisture content and lower drying potential to prevent grain spoilage. 5. The fixed cost was 65 to 75 percent of the total system cost and the variable cost was 25 to 35 percent. To reduce the fixed cost it is desirable to use a drying bin 2 or 3 times a year.

• 농업과학연구
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• 제37권2호
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• pp.245-248
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• 2010

This study was conducted to investigate effect of changes in target fat and protein contents in milk on feed cost using a simulation modeling approach based on the 2001 dairy NRC. Two simulations were done; simulation I had a limitation (up to 20%), but simulation II had no limitation for the use of cottonseed hull in a diet. Using commonly used feed ingredients in Korea, we formulated least cost diets that meet nutrient requirement of a lactating dairy cow producing 36 kg of milk with combinations of 0.1% decrease or 0.1% increase in target milk fat or protein, respectively, from the national average milk fat (4.0%) and milk protein (3.1%). The contents of alfalfa and corn in a least-cost diet were decreased and those of tall fescue, whole cottonseed and rapeseed meal were increased with decreasing fat and/or increasing protein in milk. Scenarios that decreased target milk fat percentage from 4.0% to 3.9% reduced feed cost by 2 won per kg. Due to decrease in feed intake, daily feed cost was even more reduced (136 won per head) by decreasing target milk fat percentage. Increase in target milk protein percentage from 3.1% to 3.2% reduced feed cost by 6 won per kg. Among scenarios simulated, the least feed cost was obtained in scenario aimed for 3.9% fat and 3.2% of protein in milk. We conclude that a feeding practice for increasing milk protein percentage does not directly increase feed cost. In addition, feeding practices that increase protein content in milk is expected to improve economic life-span and reproductive performance of dairy cows.

• 보건행정학회지
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• 제9권3호
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• pp.70-94
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• 1999

This paper was performed for a cost-effectiveness analysis of pharmacologic treatment of hypercholesterolemia. Agents modeled were cholestyramine, gemfibrozil. bezafibrate, lovastatin, pravastatin, simvastatin. Pharmacologic effectiveness was estimated by regression from reported clinical trials. Pharmacologic effects were expressed as the percent change of blood cholesterol level. Cost estimates included patients' travel expenses and time loss as well as resource consumption in the health care sector. Bezafibrate was the most efficient agent for reducing total cholesterol levels, having an cost over 1 year of ￦31.400 per percent reduction in total cholesterol. Simvastatin (10mg/d) was also efficient(￦33,100 per percent reduction). Chole styramine(8g/d) was least efficient at ￦90,200. For low-density lipoprotein cholesterol. simvastatin(10mg/d) was most efficient, at ￦23,200 per percent reduction, followed by lovastatin(20mg/d) at ￦28,000. Gemfibrozil was least efficient at ￦77,800 per percent reduction. For high-density lipoprotein cholesterol. bezafibrate(400mg/d) was most efficient at ￦39,300 per percent increase of high-density lipoprotein cholesterol. Cholestyramine was least efficient at ￦514,700. Analyses combining low-density lipoprotein cholesterol and high-density cholesterol effects suggest that bezafibrate(600mg/d) and simvastatin (10mg/d) were most efficient for reducing cardiovascular risk. The cost-effectiveness analysis results show that both simvastatin and bezafibrate could be efficient treatment. Simvastatin provide more effective treatment at higher cost, whereas bezafibrate is more cost-effective, as it may be less effective, at lower cost. Therefore, clinicians should choose reasonable treatment according to the patient's needs This pharmacoeconimc analysis will provide a guideline for efficient pharmacologic treatment and also be reference data for pricing new drugs.