• 한국통신학회논문지
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• 제29권7B호
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• pp.660-666
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• 2004

처리율로 대표되는 전반적인 TCP의 성능은 패킷 손실이 발생했을 때 이를 복구하는 과정의 효율성에 의해 크게 좌우된다. 특히, 무선 링크를 통한 전송 과정에서의 비트 오류로 인해 발생하는 비 혼잡 패킷 손실은 TCP의 손실 복구 성능을 크게 저하시키는 문제점이 있다. 본 논문에서는 무선 채널에 존재하는 다중 경로 페이딩(multipath fading)에 의해서 상호 연관성을 가지고 연속적으로 발생하는 패킷 손실(correlated packet Losses)에 대해 TCP 손실 복구 과정의 성능을 모델링을 통해서 분석한다. Markov 프로세스를 이용한 분석 결과를 바탕으로 전체적인 패킷 손실 확률이 매우 낮더라도 패킷 손실의 연속성이 손실 복구 차원에서의 TCP의 성능을 크게 저하시킬 수 있음을 보인다.

• 한국전기전자재료학회논문지
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• 제14권3호
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• pp.251-256
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• 2001

Bi-2223 tapes have been developed for low-field power applications at liquid nitrogen temperature. When the Bi-2223 tapes are used in an application such as a power transmission cable or a power transformer, they are supplied with an AC transport current simultaneously. AC loss taking into account such real applications is a crucial issue for power applications fo the Bi-2223 tapes to be feasible. In this paper, the transport losses for different AC current levels and arrangements of the neighboring tapes have been measured in a 1./5 m long Bi-2223 tape. The significant increase of the transport losses due to neighboring tape's AC currents is observed. An increase of the transport losses caused by a decrease of the Bi-2223 tape's critical current is a minor effect. The measured trasprot losses could not be explained by a dynamic resistance loss based on DC voltage-current characteristics in combination with the neighboring tape's AC currents.The trasport losses do not depend on the frequency of the neighboring tape's AC currents but is arrangements in the range of small current especially.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.96-100
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• 2001

Bi-2223 tapes have been developed for low-field power applications at liquid nitrogen temperature. When the Bi-2223 tapes are used in an application such as a power transmission cable or a power transformer, they are supplied with an AC transport current and exposed to an external magnetic field generated by neighboring tape's AC currents simultaneously. AC loss taking into account such real applications is a crucial issue for power applications of the Bi-2223 tapes to be feasible. In this paper, the transport losses for different AC current levels and arrangements of the neighboring tapes have been measured in a 1.5 m long Bi-2223 tape. The significant increase of the transport losses due to neighboring tape's AC currents is observed. An increase of the transport losses caused by a decrease of the Bi-2223 tape's critical current is a minor effect. The measured transport losses could not be explained by a dynamic resistance loss based on DC voltage-current characteristics in combination with the neighboring tape's AC currents. The transport losses do not depend on the frequency of the neighboring tape's AC currents but its arrangements in the range of small current especially.

• 대한전자공학회논문지TC
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• 제45권9호
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• pp.30-38
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• 2008

유선망을 가정하여 설계된 기존의 TCP를 무선망이 혼재된 망에서 그대로 사용하면 무선구간의 랜덤 손실도 유선구간의 혼잡 손실과 동일하게 간주하게 된다. 이러한 잘못된 판단과 조치는 대역폭을 낭비하여 전체 네트워크의 처리량(throughput)을 저하하게 된다. 이러한 문제를 하기 위한 노력들이 많이 있었다. 본 논문에서는 유선망 혼잡과 무선구간 손실을 판별할 개선된 방법을 사용하여 망 상황 진단의 정확도를 높이고, 판단된 각 상황에 대해서 망 처리량을 높일 수 있는 개선된 제어 방법을 제안하였다. 또한, 시뮬레이션을 통해 제안한 알고리즘의 성능을 TCP Westwood, TCP Veno와 비교하여 평가하였다.

• Journal of Electrical Engineering and Technology
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• 제5권4호
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• pp.511-521
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• 2010

This paper presents a new algorithm to determine accurate bus-wise transmission loss allocation utilizing path-integrals dictated by the transaction strategy. For any transaction strategy, the total sum of the allocated transmission losses of all buses is equal to the actual loss given by the AC power-flow calculation considering the distributed slack. In this paper, the bus-wise allocation of the transmission loss is calculated by integrating the differential loss along a path determined by the transaction strategy. The proposed algorithm is also compared with Galiana's method, which is the well-known transmission loss allocation algorithm based on integration. The performance of the proposed algorithm is evaluated by case studies carried out on the WSCC 9-bus, IEEE 14-bus, New England 39-bus, and IEEE 118-bus systems. The simulation results show that the proposed algorithm is fast and accurate with a large step size.

• Structural Engineering and Mechanics
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• 제71권3호
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• pp.305-315
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• 2019

Extremely long-span transmission tower-line system is an indispensable portion of an electricity transmission system, and its failures or collapse can impact on the entire electricity grid, affect the modern life, and cause great economic losses. It is therefore imperative to investigate the failure and safety of the transmission tower subjected to ground motions. In the present study, a detailed finite element (FE) model of a representative extremely long-span transmission tower-line system is established. A segmental damage indicator (SDI) is proposed to quantitatively assess the damage level of each segment of the transmission tower under earthquakes. Additionally, parametric studies are conducted to investigate the influence of different ground motions and incident angles on the ultimate capacity and weakest segment of the transmission tower. Finally, the collapse fragility curve in terms of the maximum SDI value and PGA is plotted for the exampled transmission tower. The results show that the proposed SDI can quantitatively assess the damage level of the segments, and thus determine the ultimate capacity and weakest segment of the transmission tower. Moreover, the different ground motions and incident angles have a significant influence on the SDI values of the transmission tower, and the collapse fragility curve is utilized to evaluate the collapse resistant capacity of the transmission tower subjected to ground motions.

• 설비공학논문집
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• 제14권1호
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• pp.63-72
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• 2002

The main objective of this study is to propose a practical two-microphone impedance tube method to measure the sound transmission loss for flexible sound isolation sheets without the use of the time-consuming and expensive reverberation room. This method was based on the sound decomposition theory developed by Seybert using the spectral density functions of the incident and reflected sound waves. In order to verify the validity of the experimental results, the measured sound transmission losses from the proposed method were compared with the measured data from the reverberation room method and the calculated data from the theory satisfying the mass law of sound isolation material. The resulted trends of the sound transmission losses versus frequencies for several different sound isolation sheets were almost same for each other and agreed quite well in both methods except at some low frequency region. From the experimental results, it was found that the accuracy of sound isolation capability obtained by two-microphone impedance tube method depends upon the microphone spacing, the distance from the first microphone to the test sample surface and the test sample location.

• Journal of the Korean Wood Science and Technology
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• 제46권4호
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• pp.338-345
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• 2018

The sound insulation capacity of a barrier is indicated by its transmission loss. In this study, the sound transmission loss of a sound barrier filled with rice-straw particles was measured by the transfer function method and a laboratory measurement method. The results of the two measurements were compared. The transmission losses measured by the two methods were similar above a frequency of 500 Hz. The loss increased greatly upon the introduction of a plywood to the sound barrier. The results of this study are expected to be used to design sound barriers for roads.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.309-314
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• 2007

Optimal layer sequencing of a multi-layered acoustical foam is solved to maximize its sound transmission loss. A foam consisting of air and poroelastic layers can be optimized when a limited amount of a poroelastic material is allowed. By formulating the sound transmission loss maximization problem as a one dimensional topology optimization problem, optimal layer sequencing and thickness were systematically found for several frequencies. For optimization, the transmission losses of air and poroelastic layers were calculated by the transfer matrix derived from Biot's theory. By interpolating five intrinsic parameters among several poroelastic material parameters, dear air-poroelastic layer distributions were obtained; no filtering or post-processing was necessary. The optimized foam layouts by the proposed method were shown to differ depending on the frequency of interest.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.101-103
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• 1998

New transmission lines are gradually constructed with high voltage and power for increase of electric power demands. And electric losses that are produced in line are increased. we made the algorithm for low loss wire and developed the computer program that makes loss of electric wire to be decreased for efficient power transmission. Electric wire is designed not to be decreased electrical and mechanical properties than that of existing electric wire.