• 한국결정성장학회지
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• 제24권3호
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• pp.111-119
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• 2014

A novel pulsed laser ablation process in liquid was investigated to prepare scheelite-type ceramic [calcium tungstate ($CaWO_4$) and calcium molybdate ($CaMoO_4$)] nanocolloidal particles. The crystalline phase, particle morphology, particle size distribution, absorbance and optical band-gap were investigated. Stable colloidal suspensions consisting of well-dispersed $CaWO_4$ and $CaMoO_4$ nanoparticles with narrow size distribution could be obtained without any surfactant. Particle tracking analysis using optical microscope combined with image analysis was applied for a fast determination of particle size distribution in the prepared nanocolloidal suspensions. The mean nanoparticle size of $CaWO_4$ and $CaMoO_4$ colloidal nanoparticles were 16 nm and 30 nm, with the standard deviations of 2.1 and 5.2 nm, respectively. The optical absorption edges showed blue-shifted values about 60~70 nm than those of reported in bulk crystals. And also, the estimated optical energy band-gaps of $CaWO_4$ and $CaMoO_4$ colloidal particles were 5.2 and 4.7 eV. The observed band-gap widening and blue-shift of the optical absorbance could be ascribed to the quantum confinement effect due to the very small size of the $CaWO_4$ and $CaMoO_4$ nanocolloidal particles prepared by pulsed laser ablation in liquid.

• 해운물류연구
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• 제27권1호
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• pp.79-98
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• 2011

반잠수식(B1) 모바일 하버의 임시 저장 공간을 효율적으로 활용하기 위하여 자동 창고 시스템 개념을 모바일 하버에 활용하는 개념을 소개하고, 이 때 발생할 수 있는 문제점들을 도출 하였다. 또한, 새로운 개념인 반잠수식(B1) 모바일 하버의 운영 시에 발생할 수 있는 여러 가지 상황을 고려하여, 반잠수식(B1) 모바일 하버에 적합한 운영 시나리오를 제안하였다. 대상 항만을 선택하여 컨테이너선 별 처리 물량을 조사함으로써 운영 시나리오에 따라 컨테이너의 환적, 수입, 수출 처리 물량을 각각 18.8%, 5%, 16.5%로 예상하였다. 모바일 하버에 도입될 자동 창고의 크기를 예측하기 위하여, 반잠수식(B1) 모바일 하버와 컨테이너선 그리고 피더선을 정적인 상황으로 가정하고, 입고량과 출고량을 선형적으로 고려하여 시뮬레이션을 수행하였다. 결과적으로 반잠수식(B1) 모바일 하버의 재고 예측량은 6800 TEU로 계산되었다.

• 대한교통학회지
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• 제10권2호
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• pp.55-68
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• 1992

Over-weight vehicles give the structure of the road an impact overly and shorten the life of the pavements. But unfortuntely so far there has been no clear regulation to implement over weight vehicles. So I suggest that the fining should be evaluated differently according to the size of axle loads. In addition I adapt our study to Pusan city and propose an adequate regulation against over weigtht vehicles.

• 한국경영과학회지
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• 제4권2호
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• pp.41-43
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• 1979

In transportation problems, various initial solution methods are known and being used. The purpose of this paper is to compare effectiveness of those methods in terms of time required in computing an initial solution. In this paper, Northwest Corner rule, Least Cost rule, Vogel's Approximation rule, Russel's Approximation rule, are compared, These rules are similar in loxio sized problems. But as the size of the problem become bigger, Russet's and Vogel's methods are found much more effective than others.

• 한국경영과학회지
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• 제19권2호
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• pp.177-198
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• 1994

We consider an algorithm for the Crew Scheduling Problem (CSP) based on the Transportation Problem approach. The main flows of the algorithm are arranged in three steps. First we propose a heuristic algorithm of the greedy principle to obtain an initial feasible solution. Secondary we present a method of formulating CSP into a Modified Transportation Problem format. Lastly the procedures of network search to get the optimal solution are presented. This algorithm can be applied to the general GSP and also to most combinatorial problems like the Vehicle Routing Problems. The computational results show that the large size CSP's could be tackled.

• 대한교통학회지
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• 제6권1호
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• pp.5-16
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• 1988

Development is given to an optimal network design method using continuous design variables. Modified Hooke-and-Jeeves algorithm is implemented in order to solve nonlinear programming problem which is approximately equivalent to the real network design problem with system efficiency crieteria and improvement cost as objective function. the method was tested for various forms of initial solution, and dimensions of initial step size of link improvements. At each searching point of evaluating the objective function, a link flow problem was solved with user equilibrium principles using the Frank-Wolfe algorithm. The results obtained are quite promising interms fo numbers of evaluation, and the speed of convergence. Suggestions are given to selections of efficient initial solution, initial step size and convergence criteria. An approximate method is also suggested for reducing computation time.

• 한국제4기학회지
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• 제21권2호
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• pp.77-79
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• 2007

The source regions of Asian Dusts (Yellow Sands) in the western part of China are investigated, and the soil samples are collected samples for approximately 15 days during the spring of 2005. Particle sizes of sediments are analyzed and compared with each other. These grain-size analyses from the source areas can be compared Particle sizes between loess deposits and desert sands in western part of China and desert areas show distinctive differences. Loess deposits are predominantly composed of fine sands and silts. The distinction between the final characteristics of Asian Dust particles arrived in Korea and characteristics during transportation can be recognized comparison with the Asian Dust particles collected where the dust particles settled down. The characteristics of Asian Dust particle sizes can provide the basic information regarding the transportation history from the source region.

• 제어로봇시스템학회논문지
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• 제20권7호
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• pp.750-755
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• 2014

Product shortage which causes backordering and/or lost sales cost is very popular in chemical industries, especially in commodity polymer business. This study deals with backordering cost in the supply chain optimization model under the framework of process-inventory network. Classical economic order quantity model with backordering cost suggested optimal time delay and lot size of the final product delivery. Backordering can be compensated by advancing production/transportation of it or purchasing substitute product from third party as well as product delivery delay in supply chain network. Optimal solutions considering all means to recover shortage are more complicated than the classical one. We found three different solutions depending on parametric range and variable bounds. Optimal capacity of production/transportation processes associated with the product in backordering can be different from that when the product is not in backordering. The product shipping cycle time computed in this study was smaller than that optimized by the classical EOQ model.

• 한국농공학회논문집
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• 제50권4호
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• pp.51-58
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• 2008

Unit costs for energy production in bioenergy facilities are dependent upon both fixed cost for facility construction and operational costs including biomass feedstock supply. With the increase of capacity, unit fixed cost could be decreased while supply cost tends to increase due to the longer transportation distance. It is desirable to take into account biomass availability in planning bioenergy facilities. A cumulative curve relationship was proposed to relate biomass availability and cumulative products of biomass amount and transportation distance. Optimum size of gasification facilities was affected by collection cost, biomass cumulative relationship. Based on biomass availability of Icheon-City, optimum sizes were about $400kW_{th}$ for gas production, and about $200kW_{el}$ for power generation. Unit cost of bioenergy production could be substantially reduced by reducing collection cost through supplying biomass from diverse sources including land development areas where significant amount of waste wood is generated. When planning bioenergy facilities, however, biomass availability and spatial distribution are key factors in determining the size of capacity.

• 한국시뮬레이션학회논문지
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• 제14권3호
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• pp.67-77
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• 2005

Logistics network of the enterprise is defined to determine the optimal node and link considering the production, inventory and transportation based on the demand forecasting. This study consider the optimal logistics network of A painter company which maintain the existing transportation network and plan to relocate its plants and build new distribution centers. For this, we design possible alternative scenarios and install the simulation models for analysis of each scenario. The result of simulation will help the proper logistic network and determining the size of distribution center further.