• 항공우주기술
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• 제6권2호
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• pp.197-204
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• 2007

터번로터 팁 형상의 변화에 따른 터보펌프 터빈의 성능변화에 대하여 실험적 연구를 수행하였다. 한국항공우주연구원에서 개발중인 30톤급 터보펌프용에 장착된 초음속 충동형 터빈을 기본 모델로 하여 터번로터 슈라우드 유무 및 팁간극 크기에 따른 터빈성능변화를 측정 비교하였으며, 이와 더불어 노즐-로터 오버랩에 따른 터빈성능 변화 연구도 함께 이루어졌다. 시험 수행 결과, 로터 슈라우드 유무에 따라 터빈성능의 절대량은 크게 변화하나 팁간극의 변화에 따른 터빈효율의 민감도는 초음속 충동형 터빈의 경우 고효율 아음속터빈에 비해 크게 작은 것으로 나타났다. 아울러, 최적 효율을 나타내는 노즐-로터 오버랩 값이 존재하는 것을 실험을 통해 확인하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.144-147
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• 2000

In this paper, we propose two receiver structures of the impulse radio (IR) system to improve its performance in multipath environments. Recently, the impulse radio system has drawn much attention for future high-speed wire-less communication services. The conventional IR receiver directly correlates received signals with the ideal reference waveform, which results in performance degradation in multipath environments. The Key idea of the proposed receiver structures is to reflect the multipath Characteristics into the IR receiver. One is to deconvolve the received waveform with estimates of the multipath gains to obtain the transmitted waveform while the other is to modify the reference waveform of the correlator according to the estimates of the multipath gains. We examine the performance of the proposed schemes for the statistical indoor wireless communication channel model using computer simulation.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2004년도 춘계학술대회 논문집
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• pp.451-455
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• 2004

Although DC ground resistance is a good index of performance for a grounding system, it does not reflect the grounding performance during the transient states. Besides, impulse ground impedance, which is defined by a ratio of the peak value of transient ground potential rise to the peak value of impulse current, cannot be an absolute performance index due to its dependence on impulse current shape. In this paper, a grounding performance of needle-typed ground rod has been compared with simple ground rod.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.1002-1008
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• 2014

This paper describes insulation design and its reliability evaluation of ${\pm}80kV$ HVDC XLPE cable. Recently, the construction of HVDC transmission system, which is combined overhead line with underground cable, has been completed. This system is installed with existing 154 kV AC transmission line on the same tower. In this paper, the lightning transient analysis is firstly reviewed for selection of basic impulse insulation level and nominal insulation thickness. Then the electrical performance tests including load cycle test and superimposed impulse test based on CIGRE TB 496 are performed to evaluate the reliability of newly designed HVDC cable. There is no breakdown for ${\pm}80kV$ HVDC XLPE cable during electrical performance test. Finally, this system is installed in Jeju island based on successful electrical performance test (Type test). After installation tests are also successfully completed.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.39-42
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• 2003

We studied the vertical launch performance of the Laser-driven In-Tube Accelerator (LITA). This device is primarily characterized by accelerating a projectile in a tube. Owing to the confinement effect, the thrust performance is enhanced. The driver gas can be specified and its pressure be turned so that the impulse performance is optimized. In the experiments, a 3.0-gram projectile was vertically launched. The effects of the projectile exit condition, the laser beam incident direction and the driver gas species were experimentally studied.

• 한국안전학회지
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• 제27권5호
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• pp.30-34
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• 2012

A safety helmet is a personal protective equipment to protect the head from falling and flying objects. A safety helmet has the maximum delivered impact force as shock absorption performance, the lower delivered impact force the better performance, which was not a controlled variety during manufacturing safety helmet. Accordingly there were some difficulties in establishing the standard for improved performance as there was not a clear controllable impact force for improved performance. In this study the shock absorption performance was intended to be found as coefficient of restitution related to impulse. As a research method, a coefficient of restitution during the absorption of shock was calculated using the impulse transferred to pharynx utilizing the safety helmet shock absorption performance testing device based on the theory of momentum and impulse. The estimated impulsive force curve was derived assuming that shock was not absorbed using the measured data. The sample was selected as tested goods of ABS material for safety certification available mainly in the market. As a result of study, the maximum delivered impact force of safety helmet made by a domestic safety certified a company was 735 N, and its coefficient of restitution proved to be 0.64. The smaller coefficient of restitution is, the lower maximum delivered impact force and the higher shock absorption performance. The coefficient of restitution can be used as a performance index of safety helmet.

• 한국정보통신학회논문지
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• 제14권11호
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• pp.2457-2462
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• 2010

본 논문에서는 Impulse Radio UWB 시스템에서 다중 접속시 발생하는 간섭을 개선하기 위해 CCI canceller를 적용하여 동일 채널 상의 다중 접속 간섭을 제거 하였다. 또한, 전송 품질을 향상시키기 위하여 Truncated Type-II Hyabrid ARQ 기법을 적용하여 다중간섭 채널 환경에서의 시스템 성능을 평가하였다.

• International Journal of Aerospace System Engineering
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• 제6권2호
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• pp.11-16
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• 2019

A system analysis program has been developed for a gas generator cycle liquid rocket engine of 30 ton class. Numerical models have been proposed for a combustor, a turbopump, a gas generator and pressure drop through a regenerative cooling system. Numerical algorithm has been validated by comparing with the published data of MC-1. The major source of error is not the numerical algorithm but the imperfect performance models of subsystems. So the precision of the program can be improved by revising the performance models using experimental data. The sea level specific impulse and vacuum specific impulse have been demonstrated for a 30 ton class gas generator engine. The optimal condition of combustor pressure and mixture ratio for specific impulse which is a typical characteristic of a gas generator cycle engine has been illustrated.

• 한국항행학회논문지
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• 제9권1호
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• pp.1-8
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• 2005

본 논문에서는 차세대 근거리 실내 무선 환경 기술로 채택 가능성이 높은 UWB(Ultra Wideband)기술용 Impulse Generator를 SRD(Step Recovery Diode)를 이용하여 설계하였다. 설계 목표는 단순한 설계 구조와 함께 저가, 소형, 고성능의 Impulse Generator 개발에 있다. 미국의 FCC(Federal Communications Commission)의 기준인 주파수 범위 3.1~10.6 GHz, 출력 제한 레벨 -41.25 dBm을 만족하는 Impulse Generator를 회로 시뮬레이터인 Agilent Technologies사의 ADS를 이용하여 설계, 제작, 측정하였다. 설계된 회로의 출력 신호는 단일밴드용과 멀티밴드용으로 구분하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.168-173
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• 2003

This experimental study describes the propagation characteristics of the impulse noise emitted from the exit of a perforated pipe attached to the open end of a simple shock tube. The pressure amplitudes and directivities of the impulse wave propagating from the exit of perforated pipe with several different configurations are measured and analyzed fur the range of the incident shock wave Mach number between 1.02 and 1.2. In the experiments, the impulse waves are visualized by a Schlieren optical system for the purpose of investigating their propagation pattern. The results obtained show that for the near sound field the impulse noise strongly propagates toward to the pipe axis, but for the far sound field the impulse noise uniformly propagates toward to the all directions, indicating that the directivity pattern is almost same regardless of the pipe type. Moreover, it is shown that for the far sound field the perforated pipe has little performance to suppress the impulse noise.