입구후드가 고속철도 터널입구의 압축파에 미치는 영향

김희동,김태호,김동형,Kim, Heuy-Dong,Kim, Tae-Ho,Kim, Dong-Hyeon 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.1

The entry compression wave, which forms at the entrance of a high-speed railway tunnel, is closely related to the pressure transients in the train/tunnel systems as well as an impulsive noise appearing at the exit of the tunnel. In order to alleviate such undesirable phenomena, some control strategies have been applied to the compression wave propagating inside the tunnel. The objective of the current work is to investigate the effect of tunnel entrance hoods on the entry compression wave at the vicinity of the tunnel entrance. Three types of entrance hoods were tested by the numerical method using the characteristics of method for a wide range of train speeds. The results show that the maximum pressure gradient of compression wave can be considerably reduced by the tunnel entrance hood. Optimum hood shape necessary to reduce the pressure transients and impulsive noise was found to be of an abrupt type hood with its cross-sectional area 2.5 times the tunnel area. It is believed that the current results are highly useful in predicting the effects of entrance hoods and in choosing the shape of proper hood.

400MPa급 건축구조용 열간압연 H형강(SHN400)의 소재 특성

김희동,최병정,김상섭,김철환,오영석,Kim, Hee-Dong,Choi, Byoung-Jeong,Kim, Sang-Sub,Kim, Chul-Hwan,Oh, Young-Suk 한국강구조학회 2011 韓國鋼構造學會 論文集 Vol.23 No.4

본 연구의 목적은 시험적 방법을 통해 SHN400 강재의 소재 특성이 건축구조용 강재로 적합한지를 평가하는 것이다. 이를 위해 국내에서 생산되는 열간 압연 H형강 중 최대 춤 및 최대 플랜지 두께의 H형강과 SHN400 강종의 주요 사용처가 될 보부재로 수요가 많은 H형강 규격을 대상으로 화학성분 평가, 인장강도, 매크로, 미크로 및 샤르피 충격 시험을 실시하였다. 각 시험은 관련 KS 규격에서 요구하는 시험 조건하에서 수행되었으며, 시험 결과 화학성분 및 기계적 특성과 관련된 모든 시험에서 SHN400 강종은 KS 규격(KS D 3866)의 요구 조건과 내진설계시 강재에 요구되는 조건들을 만족하는 것으로 나타났다. 특히 용접성과 관련된 탄소당량(Ceq)과 비탄성 변형능력과 관련된 항복비의 경우 KS 규격을 상회하는 결과를 나타내었다. 따라서 SHN400 강재는 소재 특성 측면에서 건축구조용 강재에 적합한 것으로 판단된다. The purpose of this study was to evaluate the material characteristics of SHN400 steel, which is suitable as a steel material for building structures, using the experimental approach. For this purpose, the chemical composition test, tensile test, macro test, micro test, and charpy notch impact test were conducted with specimens taken from the highest, thickest, and commonly used H-beams for girder or beam members. Each test was conducted under the Korean Standard(KS) test conditions. All the test results satisfied the requirements of KS (KS D 3866) and the steel material for seismic design. The carbon equivalent value (Ceq), which is related to weldability, and the yield ratio, which is related to inelastic behavior, showed especially good results. Thus, SHN400 is definitely suitable as the steel material for building structures.

고속철도 터널입구에서 형성되는 압축파의 특성에 관한 연구

김희동,김태호,이종수,김동현,Kim, Heuy-Dong,Kim, Tae-Ho,Lee, Jong-Su,Kim, Dong-Hyeon 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.2

Flow phenomena such as the pressure transients Inside a high-speed railway tunnel and the Impulsive waves at the exit of the tunnel are closely associated with the characteristics of the entry compression wave, which is generated by a train entering the tunnel. Tunnel entrance hood may be an effective means for alleviating the Impulsive waves and pressure transients. The objective of the current work is to explore the effects of the train nose shape and the entrance hood on the characteristics of the entry compression wave. Numerical calculations using the method of characteristics were applied to one-dimensional, unsteady, compressible flow field with respect to high-speed railway/tunnel systems. Two types of the entrance hoods and various train nose shapes were employed to reveal their influences on the entry compression wave for a wide range of train speeds. The results showed that the entry compression wave length increases as the train nose becomes longer and the train speed becomes lower. The entry compression wave length in the tunnel with hood becomes longer than that of no hood. Maximum pressure gradient in the compression wavefront reduces by the entrance hood. The results of the current work provide useful data for the design of tunnel entrance hood.

발전기 고정자 권선에 사용되는 마이카 / 에폭시 복합재료의 기계적 특성에 관한 연구

김희동,김희곤,김태완,강도열 ( Hee Dong Kim,Hee Gon Kim,Tae Wan Kim,Dou Yol Kang ) 한국전기전자재료학회 1997 전기전자재료학회논문지 Vol.10 No.4

발전기 고정자 권선에서 사용되는 마이카 / 에폭시의 열적 분석

김희동,김태완,김정훈 ( Hee Dong Kim,Tae Wan Kim,Jeong Hoon Kim ) 한국전기전자재료학회 1997 한국전기전자재료학회 춘계학술대회논문집 Vol.1997 No.0

MTF-STI를 이용한 유리창 도청음의 명료도 분석

김희동,김윤호,김석현,Kim, Hee-Dong,Kim, Yoon-Ho,Kim, Seock-Hyun 한국음향학회 2007 韓國音響學會誌 Vol.26 No.1

음향 공동-유리창 연성계를 대상으로 도청음의 음성 명료도를 검토한다. MLS신호를 음원으로 유리창의 가속도와 속도 응답을 가속도계와 레이저 도플러 진동계를 사용하여 측정한다. 변조전송함수 (MTF)를 사용하여 공동-유리창 진동계의 음성전달특성을 규명한다. 변조전송함수에 근거하여 음성전송지수 (STI)를 구하고, 유리창 진동음의 음성명료도를 평가한다. 가속도음과 속도음의 음성명료도를 비교하고, 최종적으로 대화음의 명료도를 주관적 평가로 확인한다. Speech intelligibility of the eavesdropping sound is investigated on a acoustic cavity - glass window coupled system. Using MLS (Maximum Length Sequency) signal as a sound source, acceleration and velocity responses of the glass window are measured by accelerometer and laser doppler vibrometer. MTF (Modulation Transfer Function) is used to identify tile speech transmission characteristics of the cavity and window system. STI (Speech Transmission Index) based upon MTF is calculated and speech intelligibility of the vibration sound of the glass window is estimated. Speech intelligibilities by the acceleration signal and the velocity signal are compared. Finally, intelligibility of the conversation sound is confirmed by the subjective test.

기술초대석 - SHN의 내진 특성 및 KBC2009에 따른 설계적용

김희동,이재석,안희진,Kim, Hui-Dong,Lee, Jae-Seok,An, Hui-Jin 한국건축구조기술사회 2010 건축구조 Vol.17 No.2

자동응답시스템에서 DTMF신호음 검출 개선에 관한 연구

김희동,김제우,홍영진,Kim, Hee-Dong,Kim, Je-Woo,Hong, Young-Jin 한국음향학회 1996 韓國音響學會誌 Vol.15 No.6

본 논문에서는 자동음성응답장치(ARS)에서의 복합주파수(DTMF)톤 수신의 정확도를 높이기 위한 방법을 제안한다. ARS시스템의 음성안내를 송출하는 동안 이용자가 DTMF신호를 발생할 경우, ARS시스템의 망접속부에 위치한 하이브리드에 의해 수신측으로 궤환된 음성신호가 이용자가 송신한 DTMF신호와 중첩이 되어, ARS시스템에서 DTMF신호음을 제대로 검출하지 못하는 경우가 발생한다. 제안하는 방법은 ARS의 음성안내신호에서 DTMF 신호의 주파수 대역 부분을 노치필터(notch filter)로 제거함으로써 여파된 음성안내신호가 하이브리드를 통해 수신측으로 궤환되어도 DTMF신호에 해당하는 주파수 성분이 없게 된다. DTMF수신기의 전단에는 노치필터에서 사용된 필터의 역필터특성을 갖는 대역통과필터를 설치하면, 하이브리드를 통해 수신측으로 궤환되는 신호는 DTMF수신기에 입력되지 않게 되며, 이용자가 송신하는 DTMF신호를 효과적으로 검출할 수 있다. 또한, 노치필터링된 음성신호의 음질저하는 무시할만하여 음성 안내어를 사용하는데 문제가 없다. In this paper a novel method improving the accuracy of DTMF tone reception in ARS system is proposed. ARS system should allow users to generate DTMF signals while it is sending voice guidance. It is not unocmmon, in this case, that a portion of transmitting voice signals cross-talks to the receiving channel and it often results in interfering with the receiving DTMF signals. Serious degradations including DTMF tone missing, false alarm and so forth have been introduced for the above reason. To overcome this phenomena, we have proposed a way eliminating the frequency spectra representing DTMF signals bands from the transmitting voice signal by using notch filters. This method also employs bandpass filters of which the frequency responses are reciprocal to those of the notch filters incorporated with the DTMF receiver. It is shown that a drastic improvement has been achieved with respect to the DTMF tone detection with little deterioration of voice guidance quality.

두 연속 터널을 전파하는 압축파의 실험적 연구

김희동,허남건,Kim, Hui-Dong,Heo, Nam-Geon,Setoguchi, Toshiaki 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.10

For the purpose of investigating the impulsive noise at the exit of high-speed railway tunnel and the pressure transients inside the tunnel, experiments were carried out using a shock tube with an open end. A great deal of experimental data were obtained and explored to analyze the peak pressures and maximum pressure gradients in the pressure waves. The effects of the distance and cross-sectional area ratio between two-continuous tunnels on the characteristics of the pressure waves were investigated. The peak pressure inside the second tunnel decreases for the distance and cross-sectional area ratio between two tunnels to increase. Also the peak pressure and maximum pressure gradient of the pressure wave inside the second tunnel increase as the maximum pressure gradient of initial compression wave increases.

초음속 노즐에서 발생하는 응축충격파의 피동제어

김희동,권순범,Kim, Hui-Dong,Gwon, Sun-Beom,Setoguchi, Toshiaki 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.12

When a moist air is rapidly expanded in a supersonic nozzle, nonequilibrium condensation occurs at a supersaturation state. Condensation shock wave appears in the nozzle flow if the releasing latent heat due to condensation goes beyond a critical value. It has been known that self-excited oscillations of the condensation shock wave generate in an air or a steam nozzle flow with a large humidity. In the present study, the passive control technique using porous wall with a cavity underneath was applied to the condensation shock wave. The effects of the passive control on the steady and self-excited condensation shock waves were experimentally investigated by Schlieren visualization and static pressure measurements. The result shows that the present passive control is a useful technique to suppress the self-excited oscillations of condensation shock wave.