• Journal of Aerospace System Engineering
• /
• v.11 no.6
• /
• pp.34-41
• /
• 2017

As an alternative of the existing honeycomb shock absorbing device, the new approach on shock absorbing design using the extrusion of hyper-viscoelastic material such as silicon rubber is studied in this paper. The strain energy and stress-strain characteristic of viscoelastic material at extrusion process through the metered orifice has a similarity with the honeycomb core for maximizing shock absorbing capability. And in order to evaluate the design feasibility of this device and to understand the shock absorbing mechanism of energy transformation, finite element analysis and quasi-static compression test of the multi-stage extrusion shock absorber are examined in this paper.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.10B
• /
• pp.1210-1215
• /
• 2011

In this paper, a supervised adaptive equalization algorithm based on probability density function (PDF) matching method is introduced and its decision-feedback version is proposed for underwater communication channels with strong impulsive noise and severe multipath characteristics. The conventional least mean square (LMS) algorithm based on mean squared error (MSE) criterion has shown to be incapable of coping with impulsive noise and multipath effects commonly shown in underwater communications. The linear PDF matching algorithm, which shows immunity to impulsive noise, however, has revealed to yield unsatisfying performance under severe multipath environments with impulsive noise. On the other hand, the proposed nonlinear PDF matching algorithm with decision feedback proves in the simulation to possess superior robustness against impulsive noise and multipath characteristics of underwater communication channels.

• Journal of Internet Computing and Services
• /
• v.12 no.4
• /
• pp.27-33
• /
• 2011

For compensation of channel distortion from multipath fading and impulsive noise, a decision feedback equalizer (DFE) algorithm based on minimization of Error entropy (MEE) is proposed. The MEE criterion has not been studied for DFE structures and impulsive noise environments either. By minimizing the error entropy with respect to equalizer weight based on decision feedback structures, the proposed decision feedback algorithm has shown to have superior capability of residual intersymbol interference cancellation in simulation environments with severe multipath and impulsive noise.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.1924-1928
• /
• 2009

다중패커시스템은 격리된 어느 특정 구간의 지하수를 채수할 수 있으며 그 구간의 온도, 압력 등의 자료를 연속적으로 관측할 수 있어 이를 통해 각 구간별 수리전도도를 구할 수 있다. 심도별 수직적 지하수두는 지상에서 연결 롯드를 통해 압력 측정 센서를 해당 심도까지 내려 롯드에서 설치된 압력 측정용 장비에서 관측할 수 있으며, 다중패커시스템을 이용한 수리시험으로는 양수시험, 순간충격시험, 간섭시험 등이 있는데, 본 논문에서는 순간충격시험을 이용한 결과를 제시하였다. 도출된 구간별 수리전도도를 다중패커시스템을 설치하기 전 나공에서 이중 패커를 이용한 정압주입시험의 결과와 비교하여 보았다. 다중패커시스템을 통해 획득된 심도별 지하수두는 정수두 (hydro-static)상태의 일정한 경향성이 없이, 각 심도에 존재하는 투수성 구조에 영향을 보이고 있음을 알 수 있었으며, 이는 다수의 관측공을 통해 수평 방향의 수리경사를 산출함에 있어 관측공의 심도에 대한 충분한 고려가 있어야 한다고 판단된다. 또한, 다중패커시스템을 이용한 수리시험 결과를 나공 상태에서 이중 패커를 이용한 정압주입시험 결과에 대해 심도별 도출되는 수리전도도가 국지적으로 분포하는 투수성 구조에 영향으로 인해 투수량계수 (transmissivity)로 환산한 유효 투수계수로 비교하여 결정질 암반의 수리 특성으로 제안하는 것이 타당한 것으로 분석되었다.

• Journal of Aerospace System Engineering
• /
• v.12 no.6
• /
• pp.32-40
• /
• 2018

An impact localization for a carbon fiber reinforced plastic (CFRP) composite plate was performed using the multiplexed fiber bragg grating (FBG) sensors and the error-outlier based impact localization algorithm. We found that the optimal impact localization with the maximum error of 31.82 mm and the averaged error of 6.31 mm are obtained when the error threshold (ET) and constant level (CL) are 0.3 nm and 110, respectively. Moreover, the detailed process of impact localization under certain optimal parameters and the relevant results were thoroughly investigated. We conclude that the multiplexed FBG sensors and the error-outlier based impact localization algorithm are suitable for an impact localization on composite structures, and expect that they can be utilized for various structural health monitoring (SHM) in the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1995.04a
• /
• pp.129-136
• /
• 1995

본 연구에서는 핵연료봉의 여러가지 모양형태에 대한 충격실험과 해석을 통해 비선형해석 code의 해석모델에 대한 검증을 수행하였다. 이 두 결과의 비교를 통해 개발된 모델은 다중 span을 갖는 보나 봉의 비선형충격해석에 충분히 사용될 수 있음을 확인하였다. 이러한 모델을 통한 비선형충격해석시 주의해야 할 점은 자유진동해석시의 고유진동수를 찾기 위한 경계조건을 정확히 하는 것이 중요하며, 또한 충격해석시의 정확한 충격등가스프링비를 결정하는 것이 중요하다.

• Tunnel and Underground Space
• /
• v.31 no.1
• /
• pp.52-65
• /
• 2021

In this study, authors analyzed the vapor cloud explosion induced by propane leak at the PEMIX Terminal, which is the propane storage facility outside of Mexico City. TNT equivalence mass for the leaked 4750 kg propane was estimated to be 9398 kg. Blast parameters such as peak overpressure, positive phase duration, and impact at 40-400 (m) away from the center of the explosion were calculated by applying TNT Equivalency Method and Multi-Energy Method. The probability of damage due to lung damage, eardrum rupture, head impact, and whole-body displacement impact by applying the probit function obtained using blast parameters was evaluated. The peak overpressure obtained using Multi-Energy Method was found to be greater than the peak overpressure obtained by applying the TNT Equivalency Method at all distances considered, but it was evaluated that there was no significant difference from the points above 200 m. The peak overpressure obtained by Multi-Energy Method was computed to assess the extent of damage to the structure, and it was shown that structures within 100 m of the explosion center would collapse completely, and that the glasses of the structures 400 m away would be almost broken. The probability of death due to lung damage was shown to vary depending on a human body's position located in the propagating direction of shock wave, and if there is a reflecting surface in the immediate surroundings of a human body, the probability of death was estimated to be the greatest. The impact of shock wave on lung damage, eardrum rupture, head impact, and whole-body displacement impact was evaluated and found to affect whole-body impact < lung damage < eardrum rupture

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.6
• /
• pp.571-579
• /
• 2009

For the flow analysis of reactive compressible media involving energetic materials and metallic confinements, a Hydro-SCCM (Shock Compression of Condensed Matter) tool is developed for handling multi-physics shock analysis of energetics and inerts. The highly energetic flows give rise to the strong non-linear shock waves and the high strain rate deformation of compressible boundaries at high pressure and temperature. For handling the large gradients associated with these complex flows in the condensed phase as well as in the reactive gaseous phase, a new Eulerian multi-fluid method is formulated. Mathematical formulation of explosive dynamics involving condensed matter is explained with an emphasis on validating and application of hydro-SCCM to a series of problems of high speed multimaterial dynamics in nature.

• Proceedings of the Acoustical Society of Korea Conference
• /
• 1998.06c
• /
• pp.495-498
• /
• 1998

수중폭발성음원인 SUS(signal underwater sound)는 수중에서의 폭발과 동시에 충격파와 기포파들이 연속적으로 발생한다. 이러한 신호는 광범위한 주파수대역을 가지고 전파거리가 길어지면서 굴절과 반사등의 다중경로 전파효과에 의한 신호의 변형까지 생긴다. (1,2,3). 본 연구에서는 deconvolution 방법을 이용하여 수신신호중에서 기포파효과를 최소화시켜 충격파의 수신기 도달시간을 파악하고, 각 충격파들의 전파경로를 추정하여 이 중 직접경로와 해저면 반사경로의 신호를 이용하여 해저면 반사계수를 계산하였다.

• Proceedings of the Korea Contents Association Conference
• /
• 2011.05a
• /
• pp.211-212
• /
• 2011

이 연구는 업무수행 시 발생하는 사건충격이 민간경비원의 스트레스 및 소진에 미치는 영향을 규명하는데 있다. 이 연구에서는 2011년 현재 경기도 소재 재직하고 있는 민간경비원을 대상으로 설정하였으며 169명을 표집하였다. 타당도 및 신뢰도는 요인분석과 신뢰도 분석을 통해 검증하였으며, 통계처리 방법은 다중회귀분석이 활용되었다. 결론은 다음과 같다. 첫째, 민간경비원의 사건충격은 직무스트레스에 영향을 미친다. 둘째, 민간경비원의 직무스트레스는 소진에 영향을 미친다.