• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.945-947
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• 2005

변압기, 케이블, 한류기와 같은 고온초전도 선재의 전력기기의 개발과 응용에 있어서 교류손실은 기기의 운용과 효율에 밀접한 관계가 있기 때문에 중요한 연구 분야가 되고 있다. 또한 현재 전력기기에 응용 하고 있는 고온초전도 선재는 전력기기에 필요한 통전용량을 수용 할 수 없기 때문에 이를 해결하기 위한 방법으로 선재를 적층하여 통전용량을 증대시키는 다양한 방법이 연구되고 있다. 본 논문에서는 고온초전도 선재의 적층배열을 달리 하였을 때, 외부자계에 의한 고온초전도 선재의 자화손실 특성에 대해서 연구하였다. 선재의 적층 배열의 형상은 Edge-to-Edge, Face-to-Face형과 Matrix형이며, 적층배열에 사용한 선재의 개수는 2, 4, 8개이다. 연구결과, 동일한 적층 수의 조건하에서 Face-to-Face형의 적층배열이 다른 종류의 배열보다 자화손실이 낮음을 확인하였고, 이는 Face-to-Face 형태로 적층 될 때 인접선재로 인한 자기차폐효과가 다른 배열의 경우보다 우수하기 때문으로 보인다.

• Journal of the Korea Society of Computer and Information
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• v.5 no.4
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• pp.82-89
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• 2000

This study analyzes the cell loss probability of an ATM multiplexer with real time and non-real time bursty traffics. It is assumed that an ATM multiplexer with loss priority control for the analysis. The loss priority control uses the CLP Reld of cell header. For easy analysis and less computation. the multiplexed traffic of the ATM multiplexer was modeled by the MMDP. The ATM multiplexer is simulated by the MMDP/MMDP/l/K queueing system. From the above results, The connection admission of an ATM multiplexer with loss priority control is determined by the cell loss probability with low priority as well as the size of threshold buffer. Therefore, to increase the statistical multiplexing gain it will be good to utilize the loss priority control in order.

• Journal of the Korean Data and Information Science Society
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• v.21 no.6
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• pp.1051-1060
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• 2010

In the plating process of the IC chips for the printed circuit board manufacturing, specification limits for the plating thickness are usually given but its target is not specified in most cases. When the target is not specified, the center point of the specification limits is used instead. When the process capability is large, however, the use of the center point for the target is not the best choice in the context of the total cost. In this paper, the total cost is defined in terms of the production cost and the loss function, and then the optimal choice for target is studied in order to minimize the expected loss. As a consequence, the optimal choice of the target reduces the expected loss significantly, while reducing the process capability slightly.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.6
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• pp.159-166
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• 2005

The pulse amplitude of a search radar signal received by an ES system is not constant pulse by pulse because of the radar's scan characteristics. The variation of the pulse amplitude causes the ES detection loss in the ES system. Therefore, the ES detection range equation should consider the ES detection loss caused by the search radar's scan characteristics. In this paper, we theoretically analyze the ES detection loss for the circular scar and propose the model to evaluate it quantitatively. The experiment results for the real search radar signals demonstrate that the proposed model is suitable for the evaluation model of the ES detection loss related to the circular scan of radars.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.389-392
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• 2020

In order to accurately predict the losses in the power cable, analysis of the eddy current losses in the metal sheath is required. The copper loss is easily calculated by the resistance and current of the conductor, but it is difficult to measure and predict the eddy current generated from the metal sheath. For this purpose, the previous study analyzed the eddy current loss in single phase cable, but there is a limit to apply it because three phase cables are used in real environment. Therefore, in this paper, the eddy current loss occurring in the metal sheath of three phase cable according to the cause was analyzed theoretically. In addition, the eddy current loss occurring in the triangular and horizontal array were predicted through electromagnetic numerical analysis.

• Journal of Korea Water Resources Association
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• v.41 no.3
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• pp.305-314
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• 2008

Urban sewer systems are designed to operate in open-channel flow regime and energy loss at circular manholes are usually not significant. However, the energy loss at manholes, often exceeding the friction loss of pipes under surcharge flow, is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharge flow. Hydraulic experimental apparatus which can be changed the invert type(CASE A, B, C) and step height(CASE I, II, III) was installed for this study. The range of the experimental discharges were from $1.0{\ell}/sec$ to $5.6\;{\ell}/sec$. As the manhole diameter ratio($D_m/D_{in}$) increases, head loss coefficient increases due to strong horizontal swirl motion. Head loss coefficient was maximum because of strong oscillation of water surface when the range of manhole depth ratios($h_m/D_{in}$) were from 1.0 to 1.5. The average head loss coefficients for CASE A, B, and C were 0.45, 0.37, and 0.30, respectively. Accordingly, U-invert is most effective for energy loss reduction at circular manhole. This head loss coefficients could be available to design the urban sewer system with surcharge flow.

• Economic and Environmental Geology
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• v.49 no.1
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• pp.63-75
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• 2016

The ratio of fractured reservoir is very high in oil & gas fields around the world. The demand of drilling technology for fractured reservoir is expected to increase continuously if oil and gas prices are economical. The purpose of the review study is to help operator or driller in selecting of proper drilling technology for preventing a lost circulation in the fractured formation. In order to achieve this goal, fractured reservoir(formation) they are classified into partial lost circulation formation and total lost circulation formation. In case of partial lost circulation formation, the drilling problem can be solved by using LCM(lost circulation material) mud additive and squeezing cement. For shallow depth, total lost circulation formation can be drilled safely and economically with casing drilling method. Also, for deeper depth, problems of total lost circulation in formation can be solved by applying mud cap, which is one of the drilling methods. This was confirmed through field application such as Italy's Medusa-1 field and Qatar's North field.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.126-129
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• 2010

본 논문에서는 패킷 오류가 발생하는 IP 망을 통해 비디오 전송 서비스를 제공하기 위한 조건적 ARQ 기반의 오류 제어기법을 제안한다. IP 망에서 패킷 손실이 발생하면 수신 단말은 서버에게 손실된 패킷의 재전송을 요청할 수 있다. 그러나 망 상황과 접속 단말 개수를 고려하지 않고 무조건적인 재전송을 요청 할 경우 손실된 패킷이 복호화에 필요한 시점까지 도착 할 것인지가 보장되지 않을 뿐더러, 오히려 불필요한 재전송 요청에 의해 망에서의 트래픽 량을 가중시킬 수 있다. 따라서 망 상황을 고려하여 손실된 패킷이 재전송에 의해 적절한 시간 내에 도착이 가능한지를 판단하여 조건적으로 ARQ를 요청하는 기술이 요구된다. 본 논문에서는 기존의 RFC 문서에서 권고하는 재전송 관련 메카니즘들을 효과적으로 활용하여 표준기술 기반의 조건적 ARQ 오류제어 기법을 제안한다. 제안된 기법에서는 단말에서 추정된 망 상황을 기반으로 조건적으로 재전송 요청 여부를 결정하고, 더 나아가서 유효한 재전송 요청 시점을 결정하여 보다 효율적인 ARQ 가 적용될 수 있도록 한다. 제안된 조건적 ARQ 기반의 오류 제어 기법의 성능을 검증하기 위하여 패킷 손실 네트워크 환경을 NIST-Net을 활용하여 구축하며 실험 결과를 통해 제안된 기법의 우수한 오류 강인 성능을 확인한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04b
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• pp.883-886
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• 2001

이동 통신 채널과 같이 에러 발생율이 높은 환경에서 부호화된 비디오 스트림을 전송시 발생된 에러는 비디오 화질에 큰 영향을 줄 수 있다. 본 논문에서는 현재 널리 사용되고 있는 H.263의 복호화기에서 전송도중 에러가 발생했을 경우 추가적인 데이터 스트림의 삽입 없이 효율적으로 에러를 은닉할 수 있는 기법에 관하여 연구하였다. 특히 인터프레임 영상에서 손상되거나 손실된 움직임벡터에 대해 시간영역에서 관계가 깊은 이전 프레임에서 손실블록과 같은 위치에 있는 블록의 움직임벡터와 현재 프레임에서 손실블록과 인접한 블록들의 움직임벡터 정보를 이용하여 이 블록들의 움직임 방향을 구하게된다. 이러한 블록의 움직임 방향을 이용하여 동일한 움직임 방향을 갖는 영역을 찾아 손실 블록이 어떤 움직임 영역에 속하는 지를 판단하여 손실된 움직임 벡터를 복원하는 방법을 제안한다. 또한 제안한 알고리즘에 중복블록 움직임 보상(Overlapped Block Motion Compensation)을 적용하여 블록화 현상을 줄였다.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.126-133
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• 2007

An experimental apparatus has been designed and prepared in order to measure a pressure loss coefficient of hydropneumatic components, which is an important parameter in a hydropneumatic system Blow-down system has been adopted for the experimental apparatu to meet the high flow energy requirement as well as the apparatus safety. Especially, pressure loss coefficient measurements of pyrostarter filters have been performed and the pressure loss coefficient, K of CQSF has been experimentally acquired. Then it is shown that the turbine inlet pressure $p_2$, which is predicted from the measured K, is in accord with the results of combustion tests. Moreover, the relation between K and combustion pressure $p_0$ has been presented and it is disclosed that the relation accords well with the results of combustion tests. It is anticipated that K of a filter could play a role in PS size reduction by rising up the combustion pressure resulting in increasing the burning rate of solid propellant.