• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전기설비전문위원
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• pp.261-262
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• 2008

Damaged glass insulator that is utilized the high-speed railroad in domestic try to find the cause. This paper is investigated on the characteristics of alumina cement as the binder of class insulator. The components of glass insulator ore stub(tin), rod(tin), shed(tempered glass), and alumina cement. If composition of alumina cement is not unified, crack of alumina cement generated. As these results, cracked marks of cement is appeared and composition of alumina cement is not unified. Therefore, it is estimated that main element of long-term degradation is a alumina cement.

• 한국군사과학기술학회지
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• 제11권3호
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• pp.129-137
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• 2008

Hull-Mounted Sonar(HMS) has been the main equipment to detect and track underwater threats like torpedoes and enemy submarines. The HMS has short warming-up time and is employable independently with sea-state and weather condition. But these bad environmental condition and ship maneuvering make ship's roll and pitch. Ship's roll and pitch make unstability of sensor position, then cause degradation of the HMS performance. In this paper, we will show how the unstability influences the HMS performance, propose the 'Beam Stabilization Beamforming Technique' to overcome these phenomenon. And present the effectiveness of proposed technique by comparing with conventional beamforming result.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1180-1185
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• 2003

One of the main degradation of steam generator tubes is stress corrosion cracking induced by residual stress. The resulting damages can cause tube bursting or leakage of the primary water which contained radioactivity. Primary water stress corrosion crack occurs at the location of tube/tubesheet hard rolled transition zone. In order to investigate the effect of shot peening on stress corrosion cracking, stress intensity factors are calculated for the crack which is located in the induced residual stress field.

• 대한전기학회논문지
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• 제44권2호
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• pp.222-227
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• 1995

A new IGBT structure, which may suppress latch-up phenomena considerably, is proposed and verified by MEDICI simulation. The proposed structure employing the segmented $n^{+}$ buffer layer increases latch-up current capability due to suppression of the current flowing through the resistance of $p^{-}$ well, $R_{p}$, which is the main cause of latch-up phenomena without degradation of forward characteristics. The length of the $n^{+}$ buffer layer is investigated by considering the trade-off between the latch-up current capability and the forward voltage drop. The segmented $N^{+}$ buffer layer results in better latch-up immunity in comparison with the uniform buffer layer.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 춘계 학술논문 발표대회
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• pp.260-261
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• 2019

Corrosion of rebar embedded reinforced concrete is the main cause of collapse and degradation of reinforced concrete structure that many researches are recently focused on these works. Methods of evaluating rebar corrosion are divided into physical and electrochemical methods. However, the result of Conventional methods are less reliable due to effect of internal and external environments. In this study, rebar corrosion detection sensor for embedded rebar of RC structures is evaluated through immersion test in NaCl solustion for 160hours. From the results, Rebar corrosion was ongoing and corrosion products are produced on rebar surface. The voltage is decreased as amount of corrosion production increased.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 춘계 학술논문 발표대회
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• pp.115-116
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• 2015

Recently, most of the construction companies is being degraded due to the overall construction recession profitability. Among them, order quantity of the architectural and engineering firms are trend to decrease except for large companies over a certain size. In particular, small companies are facing more difficulties. This study was conducted expert interview method to extract the main cause of profitability degradation of a small-sized design engineering companies. And, we are proposes a critical influence factors through survey about extracted factors. The results of this study are expect to help the competitiveness of architectural design firm.

• 한국통신학회논문지
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• 제30권6C호
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• pp.450-456
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• 2005

In this paper, we propose a high-speed turbo decoding algorithm and present results of its implementation. The latency caused by (de)interleaving and iterative decoding in conventional MAP turbo decoder can be dramatically reduced with the proposed scheme. The main cause of the time reduction is to use radix-4, center to top, and parallel decoding algorithm. The reduced latency makes it possible to use turbo decoder as a FEC scheme in the real-time wireless communication services. However the proposed scheme costs slight degradation in BER performance because the effective interleaver size in radix-4 is reduced to an half of that in conventional method. To ensure the time reduction, we implemented the proposed scheme on a FPGA chip and compared with conventional one in terms of decoding speed. The decoding speed of the proposed scheme is faster than conventional one at least by 5 times for a single iteration of turbo decoding.

• 대한전기학회논문지:전력기술부문A
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• 제48권3호
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• pp.197-202
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• 1999

Electric arc furnaces (EAFs) use bulk electrical energy to create heat in metal refining industries. The electric arc process is a main cause of the degradation of the electric power quality such as voltage flicker due to the interaction of the high demand currents of the load with the supply system impedance. The stochastic models have described the aperiodic physical phenomena of EAFs. An alternative approach is to include deterministic chaos in the characterization of the arc currents. In this parer, a chaotic approach to such modeling is described and justified. At the same time, a DLL(Dynamic Link Library) module, which is a FORTRAN interface with TACS (Transient Analysis of Control Systems), is developed to implement the chaotic load model in the Electromagnetic Transients Program (EMTP). The details of the module and the results of tests performed on the module to verify the model and to illustrate its capabilities are presented in this paper.

• 한국통신학회논문지
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• 제41권1호
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• pp.107-109
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• 2016

본 논문은 모바일 환경의 무선랜 사용자들이 주기적인 채널 탐색을 통해 새로운 AP를 찾고자 할 경우 TCP 처리율 측면에서 발생할 수 있는 문제점을 살펴보고 그 원인에 대하여 분석한다. 실험을 통하여 채널 탐색 주기에 따른 TCP 처리율을 측정하였으며, 짧은 주기에 큰 성능저하가 발생하였다. 이것은 모바일 노드의 채널 전환에도 불구하고 AP로부터 전송에 의해 패킷 손실이 발생하기 때문이다.

• Journal of Power Electronics
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• 제10권2호
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• pp.194-202
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• 2010

The main cause of degradation in an unbalanced stand-alone doubly-fed induction generator (DFIG) system is negative sequence components that exist in the generated stator voltages. To eliminate these components, a hybrid current controller composed of a proportional-integral controller and a resonant regulator is developed in this paper. The proposed controller is applied to the rotor-side converter of a DFIG system for the purpose of compensating the negative stator voltage sequences. The proposed current controller is implemented in a single positive rotating reference frame and therefore the controller can directly regulate both the positive and negative sequence components without the need for sequential decomposition of the measured rotor currents. In terms of compensation capability and accuracy, simulations and experimental results demonstrated the excellent performance of the proposed control method when compared to conventional vector control schemes.