• 대한산업공학회지
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• 제28권2호
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• pp.187-192
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• 2002

In this paper we consider an M/G/1 queueing system with vacation. The length of vacation period may be controlled by the waiting time of the first customer. The server goes on vacation as soon as the system is empty, and resumes service either when the waiting time of the leading customer reaches a predetermined value, or when the vacation period is expired, whichever comes first. We consider two types of vacation, say, multiple vacation type and N-policy type. We derive the steady-state distributions of the number of customers at arbitrary time and arbitrary customer's waiting time by means of decomposition property. Also, the mean lengths of busy period, idle period and a cycle time are given.

• Management Science and Financial Engineering
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• 제13권1호
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• pp.93-113
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• 2007

In the previous research, we considered a logistics brokerage problem with the objective of minimizing total transportation lead time of freights in a logistics e-marketplace, in which a logistics brokerage agent intermediates empty vehicles and freights registered by car owners and shippers [7]. However, in the logistics e-marketplace, transportation due date tardiness is more important than the transportation lead time, since transportation service level is critically determined by whether the due date is met or not. Therefore, in this paper, we deal with the logistics brokerage problem with the objective of minimizing total tardiness of freights. Hungarian method based matching algorithms, real time matching(RTM), periodic matching(PM), and fixed matching(FM), are used for solving the problem considered in this paper. In order to test performance of the proposed algorithms, we perform computational experiments on a various problem instances. The results show that the waiting-and-matching algorithms, PM and FM, also give better performance than real time matching strategy, RTM, for the total tardiness minimization problem as the algorithms did for the total lead time minimization problem.

• 유기물자원화
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• 제8권3호
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• pp.124-130
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• 2000

본 연구는 가솔린 휘발가스를 퇴비 바이오필터로 처리시 공정조절 인자인 체류시간과 충전깊이의 영향을 살펴보고 공정개선방안을 제시하고자 실시하였다. 체류시간을 4, 10, 그리고 20분으로 변화하여 실시한 결과 TPH의 효율적 제거를 위해서는 10분이상의 EBRT가 요구되었으며 $40g/m^3$(충전물질)/hr 미만의 부하로 운전하는 것이 효과적이었다. BTEX는 체류시간 4분에서는 부하량이 약 $1.5g/m^3$(충전물질)/hr 이상으로 증가하자 더 이상 제거 능력이 증가하지 않았으며, 체류시간 10분에서는 약 $5.3g/m^3$(충전물질)/hr의 부하량에서 $4.5g/m^3$(충전물질)/hr 이상이 제거되었다. 이로써 안정적인 제거를 위해서는 BTEX도 10분 이상의 체류시간이 필요하였다. 충전깊이는 25, 50, 75, 그리고 100cm로 하였다. TPH 제거량을 증가시키기 위해서는 단순히 충전깊이를 증가시키는 것보다 가스체류시간 및 유입부하량 등 다른 공정인자들을 제어하는 것이 더욱 효과적이었다. BTEX의 경우에는 다른 공정인자의 조절도 중요하지만 충전깊이를 1m 정도로 하면 다른 공정인자의 조절에 큰 어려움 없이도 제거효율을 향상시킬 수 있을 것이다.

• 생명과학회지
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• 제10권1호
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• pp.14-21
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• 2000

음요수 중의 유기탄소의 제거수단으로써 biofiltration법의 타당성을 검토하였다.NOM에서의 생분해 가능한 분율을 알아보기위하여 행하여 졌다. UV 조사량을 3가지로 달리하였을 경우에 회분식에서의 생분해능과 비교하였다. 생물여과 반응기 실험의 경우에 생분해 특성을 검토한 결과 EBCT, 순환비 및 유입농도등과 같은 운전피라미터들이 생물여과 반응기의 생분해능에 영향을 미침을 알 수있었다. 생물여과 반응기의 유출수에서의 UV/DOC의 비는 반응기에 공급되는 원료중의 UV/DOC비에 비해 증가하였으며, 이로부터 생분해에 의해 저거된 DOC는 UV에 의해 그다지 흡수되지 않는 물질임을 알 수있었다. 본 여눅를 통해 생분해 가능한 DOC의 부분을 제거하는데 있어서 생물여과공법이 효과적인 방법이라는 것을 알수있었으며 UV처리와 bilfiltration을 연계한 공정은 수처리 시설에서 유출수의 DOC농도는 낮추는데 효과적인 한가지 방안으로 사료되었다.

• 한국실내디자인학회논문집
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• 제25권5호
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• pp.157-166
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• 2016

This study is intended to examine the various kinds of emptiness that are shown in the empty spaces created by Hyo-Sang Seung and Louis I. Kahn. Architecture creates the usefulness of a certain space thanks to its emptiness. The word, 'Emptiness' has the following meanings, 'non-fulfillment', 'non-existence', 'emptiness', 'blankness', 'non-visibility' and 'non-limitation', etc. Such concepts of emptiness can be broadly divided into 'ideological emptiness', 'aesthetic' and 'architectural spatial'. Comparisons regarding such concepts of emptiness as they are expressed in the architectural spaces created by Hyo-sang Seung and Louis I. Kahn shall be identified in this study. Hyo-sang Seung tried to leave numerous open possibilities which can contain everything into a certain space since 'emptiness' is not being used at this moment. Louis I. Kahn tried to contain into a space the essence and silence of that space before something that exists is created. The 'emptiness' created by Hyo-sang Seung and Louis I. Kahn is a specific space which can contain more kinds of non-visible spaces than some visible ones. Thus, such spaces may contain various potentials which are possible because they are empty, because of changes in nature and time, and because of silence and intentions going beyond an artist's original intent.

• 한국안전학회지
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• 제30권5호
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• pp.92-99
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• 2015

The diameter of a new wheel in EMUs is 860mm and it can be used up to 773mm. To obtain an predefined acceleration despite wheel diameter changes, the tractive efforts of the vehicles must be properly controlled. In the commencement of this study, acceleration tests were performed for empty EMUs when the wheel diameter was changed to 860mm, 820mm and 780mm, respectively. In order to deal with more complicated running conditions, we developed dynamic simulation models of the EMUs using VI-Rail, and simulated the models in empty and full passenger loads, respectively. Using the simulation results, we analyzed the gradient of time-velocity graphs by considering the changes of the total weight vehicles and moment of inertia of the wheelsets as well as tractive effort according to the wheel diameter changes. As the results, it was found that there are significant differences in acceleration performances according to the wheel diameters and the payloads of EMUs. In case of 860mm which is the maximum wheel diameter, the test & simulation results show that the vehicle couldn't reach the predefined acceleration, 3.0km/h/s, due to lack of tractive effort.

• 한국컴퓨터그래픽스학회논문지
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• 제19권2호
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• pp.19-27
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• 2013

본 연구에서는, 결과물의 우수함을 유지하면서도 기존 연구결과의 성능을 4-7배 향상시킨 실시간 GPU 등가면 볼륨 레이케스터를 제시한다. 이러한 성능 향상은 효율적인 빈공간 생략법과 분석적 그레디언트 계산법을 도입함으로써 가능하다. 빈공간 생략법은 스플라인 조각들의 BB-형식으로부터 만등어진 최소/최대값 옥트리에 기반하고 있고, 분석적 그레디언트 계산법은 보다 정확한 렌더링 결과를 제공할 뿐 아니라 더욱 빠른 계산이 가능하도록 한다.

• 디지털산업정보학회논문지
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• 제10권3호
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• pp.273-283
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• 2014

Imported and exported agricultural products are facing a very difficult time due to the rising distribution costs spurred by the increasing labor and oil prices. High empty transfer rates, which take place on a return route after the regular transportation of imported and exported agricultural products, are especially a major cause of the rising distribution costs. In an effort to overcome those limitations, this study set out to examine the transportation stages connecting harbor warehouses, processing plants, and central distribution centers on the circulation route of such imported grains as wheat, barley, corn, and soybean and the transportation route from the warehouses devoted to exported agricultural products to harbors for such exported agricultural products as apple, pear, and persimmon in order to develop a model on the creation of a compound logistics complex for processing plants and transshipment of imported and exported agricultural products. The study also promoted the logistic rationalization of imported and exported agricultural products by creating a compound logistics complex that would combine processing plants for imported agricultural products and transshipment functions for exported agricultural products.

• Structural Engineering and Mechanics
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• 제60권4호
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• pp.655-665
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• 2016

This paper aims to develop models to accurately predict the behavior of fresh concrete exposed to vibration using artificial neural networks (ANNs) model and regression model (RM). For this purpose, behavior of a full scale precast concrete mold was investigated experimentally and numerically. Experiment was performed under vibration with the use of a computer-based data acquisition system. Transducers were used to measure time-dependent lateral displacements at some points on mold while both mold is empty and full of fresh concrete. Modeling of empty and full mold was made using both ANNs and RM. For the modeling of ANNs: Experimental data were divided randomly into two parts. One of them was used for training of the ANNs and the remaining part was used for testing the ANNs. For the modeling of RM: Sinusoidal regression model equation was determined and the predicted data was compared with measured data. Finally, both models were compared with each other. The comparisons of both models show that the measured and testing results are compatible. Regression analysis is a traditional method that can be used for modeling with simple methods. However, this study also showed that ANN modeling can be used as an alternative method for behavior of fresh concrete exposed to vibration in precast concrete structures.

• 한국멀티미디어학회논문지
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• 제16권7호
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• pp.852-861
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• 2013

의료영상을 이용한 볼륨가시화를 수행할 때, 사용자가 관심있는 영역을 확대 관찰하는 일은 빈번하게 발생한다. 확대 영상에서 나뭇결 결함으로 불리는 문제가 발생하기 때문에, 기존 연구는 교란 샘플링을 이용하여 문제를 해결하였다. 그러나 교란 샘플링 방법은 관찰 영역 경계에서 잡음이 발생하는 문제가 있다. 본 연구는 교란 샘플링 시 경계에서 발생하는 잡음의 원인을 설명하고 그 해결 방법을 제시한다. 잡음 없이 나뭇결 결함을 제거하기 위해, 본 연구는 빈공간교란 기법과 샘플링 위치 정렬 기법을 제안한다. 제안 방법을 통해, 추가 시간 없이 고화질 볼륨가시화 영상을 생성할 수 있다.