• Korean Chemical Engineering Research
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• 제59권3호
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• pp.467-479
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• 2021

Abstract: A kinetic model was developed for the dehydration of ethanol to ethylene based on two parallel reaction pathways. Kinetic parameters were estimated by fitting experimental data of powder catalysts in a lab-scale test, and the effectiveness factor was determined using data from pellet-type catalysts in bench-scale experiments. The developed model was used to design a multitubular fixed-bed reactor (MTR) and an adiabatic reactor (AR) at a 10 ton per day scale. The two different reactor types resulted in different process configurations: the MTR consumed the ethanol completely and did not produce the reaction intermediate, diethyl ether (DEE), resulting in simple separation trains at the expense of high equipment cost for the reactor, whereas the AR required azeotropic distillation and cryogenic distillation to recycle the unreacted ethanol and to separate the undesired DEE, respectively. Quantitative analysis based on the equipment and annual energy costs showed that, despite high equipment cost of the reactor, the MTR process had the advantages of high productivity and simple separation trains, whereas the use of additional separation trains in the AR process increased both the total equipment cost and the annual energy cost per unit production rate.

• 경영과학
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• 제33권3호
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• pp.89-103
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• 2016

In this paper, we design sampling inspections and service capacities simultaneously for multi-products. Products are supplied in batches after rectifying inspections, that is, rejected lot is subject to total inspection and defective products are reworked to good ones. When supplied, all defective products are uncovered and returned to service. Particularly, we extend Kim [1] by introducing the fixed costs of providing services and show that the cost function of a product is no longer linear or convex in terms of the level of service provision. We develop a framework for a product to deal with this joint design problem and a dynamic programming algorithm for multi-products which allocates the given number of the total service capacities among products with the considerably smaller computations than the total number of possible allocations.

• 한국양식학회지
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• 제16권4호
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• pp.203-209
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• 2003

Nitrification efficiency of fixed film biofilters with sand, loess bead, and styrofoam bead in biofilter columns of 1-m height and 30 cm width was studied. Synthetic wastewater was continuously supplied to the culture tank to maintain total ammonia nitrogen (TAN) concentration in the inflow water at around 8 mg/L. The hydraulic loading rate was set at 200 ㎥/$m^2$/day. TAN conversion was stabilized after about 90 day conditioning for all the selected filter media but with net accumulations of nitrite. On the volumetric basis, conversion rates of TAN and nitrite were the highest in styrofoam bead filter. Mean volumetric TAN conversion rates in the final samples were 682, 269, and 79 g TAN/㎥/day in the styrofoam bead, sand and loess bead filters, respectively. Low gravity and cost of styrofoam bead render the handling easier and more cost-effective.

• 산업공학
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• 제20권2호
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• pp.103-111
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• 2007

A heterogeneous VRP which considers various capacities, fixed and variable costs was suggested in this study. The transportation cost for vehicle is composed of its fixed and variable costs incurred proportionately to the travel distance. The main objective is to minimize the total sum of transportation costs. A mathematical programming model was suggested for this purpose and it gives an optimal solution by using OPL-STUDIO (ILOG CPLEX). A genetic algorithm which considers improvement of an initial solution, new fitness function with weighted cost and distance rates, and flexible mutation rate for escaping local solution was also suggested. The suggested algorithm was compared with the results of a tabu search and sweeping method by Taillard and Lee, respectively. The suggested algorithm gives better solutions rather than existing algorithms.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2002년도 춘계학술대회
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• pp.237-241
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• 2002

This paper deals with the problem of determining the buyer's economic lot sizing policy for exponentially deteriorating products under trade credit. It is also assumed that the ordering cost consists of a fixed set-up cost and a freight cost, where the freight cost has a quantity discount offered due to the economies of scale. We formulate the mathematical model and the solution algorithm is developed based on the properties of an optimal solution.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.179-180
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• 2020

In the budgeting guidelines, there are rules for calculating design fee and direct costs. However, only the design fee is calculated excluding the direct cost, which causes the cost to be insufficient. Therefore, this study is designed to analyze representative cases where direct costs are insufficient, draw out problems, and propose a way to improve design fees.

• 한국경영과학회지
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• 제41권4호
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• pp.113-128
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• 2016

This paper proposes a Bi-level Genetic Algorithm for the Fixed Charge Transportation Problem with Non-linear Unit Cost. The problem has the property of mixed integer program with non-linear objective function and linear constraints. The bi-level procedure consists of the upper-GA and the lower-GA. While the upper-GA optimize the connectivity between each supply and demand pair, the lower-GA optimize the amount of transportation between the pairs set to be connected by the upper-GA. In the upper-GA, the feasibility of the connectivity are verified, and if a connectivity is not feasible, it is modified so as to be feasible. In the lower-GA, a simple method is used to obtain a pivot feasible solution under the restriction of the connectivity determined by the upper-GA. The obtained pivot feasible solution is utilized to generate the initial generation of chromosomes. The computational experiment is performed on the selected problems with several non-linear objective functions. The performance of the proposed procedure is analyzed with the result of experiment.

• 문화기술의 융합
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• 제5권1호
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• pp.353-360
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• 2019

신용거래는 공급자가 고객의 수요를 증대 시킬 목적으로 경쟁 업체와의 가격 차별화 전략의 하나로 활용되어진다. 고객 입장에서 보면 공급자로부터 제품 대금에 대하여 일정 기간 동안 지불 유예가 허용되면, 재고 투자 비용이 절감되는 효과가 발생하고 결국 고객의 재고 정책에 긍정적인 영향을 미치게 된다. 전통적인 재고 모형의 경우 고객의 주문 비용은 주로 고정 비용으로 가정하였다. 그러나 많은 실제 문제의 경우, 고객은 고정 주문 비용과 함께 제품 운송을 위한 운송비용을 부담하고 있으며, 대부분의 운송비용은 구입량(주문량)에 따라 종속적으로 발생하게 된다. 본 연구에서는 공급자가 고객에게 제품 대금에 대하여 일정 기간 동안 신용거래를 허용하는 상황 하에서 고객의 주문 비용이 고정 주문 비용과 함께 주문량에 따라 종속적으로 발생하는 운송 비용을 포함한 재고 모형을 분석하였다. 문제 분석을 위하여 재고는 시간이 경과함에 따라 일정률로 퇴화한다는 가정 하에 고객의 연간 총 재고 비용에 대한 모형을 수립하였고, 총비용을 최소화하는 경제적 주문량 결정을 위한 해법을 개발하였다.

• 한국수자원학회논문집
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• 제44권1호
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• pp.1-8
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• 2011

본 연구는 패널자료(15개 시도의 20년간 자료)를 이용하여 홍수피해 비용과 복구비와의 상관관계에 대한 분석을 시도하였다. 패널 분석은 자료의 성격에 따라 고정효과모형 또는 확률효과모형을 사용하지만 본 분석은 두 모형을 함께 추정하였다. 예상대로 모든 변수들은 복구비와 정의 상관관계를 보였지만 사망자수와 이재민 수는 유의하지 않거나 오히려 음의 상관관계를 보이기도 하였다. 그리고 공공시설의 피해가 가장 중요한 인자였다. 무엇보다 중요한 것은 우리나라의 경우 복구비가 피해액이나 투자액에 비해 항상 높다는 것이다. 우리나라와는 반대로 일본의 경우 복구비가 가장 낮고 투자비가 가장 높다는 점을 미루어 볼 때 결국 적절한 투자가 향후 홍수피해는 물론 복구비도 낮출 수 있다는 점을 확인할 수 있었다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2007년도 추계학술대회 및 정기총회
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• pp.357-357
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• 2007