• Explosives and Blasting
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• v.29 no.2
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• pp.32-42
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• 2011

For blasting vibration analysis, there are mostly two methods, firstly, far field vibration analysis to estimate limit of building damage, secondly, near field subterranean vibration analysis to estimate rock damage and subterranean structure facilities. The former has been mainly used in our country and aboard, the latter is mostly analysed by using Homberg's model. In this model, basic input data are acquired in far field surface vibration. But in the consideration of the results of being conducted in this area over the past few decade, it is required that Homberg's model is modified. For the purpose of this, measurements of near field vibration were first conducted in our country. But it was only proposed the measurement method and the method of analysis or prediction was not suggested. Accordingly, in this paper, measurements of near field subterranean vibration were conducted and the method of analysis or prediction of near field subterranean vibration would be suggested.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.437-440
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• 2004

HMS(Hull Mounted Sonar) 운용 시 수중음속구조의 영향에 의한 음파가 경계면(해저면, 해수면)의 반사를 통해서 근거리 음영구역(short range shadow zone)을 발생시킨다(그림 1). 따라서 본 논문에서는 다양한 수중음파탐지 무기체계 가운데 특히 단상태 (monostatic) 조건일 때 HMS에 의해 발생하는 근거리 음영구역을 최소화하는 방안을 연구하였다. 즉, 2차원 수중공간 (수심-거리)에서 빔형성기법 (beamforming)을 이용한 HMS Vertical Scanning (HMS Verscan) 기법을 제안하여 수치 실험을 수행하였다. 수치실험을 위해 HMS 운용환경에 근접한 고주파 음선모델(BELLHOP)과 잔향음 모델(HYREV)을 이용하였다. 그 결과 HMS Verscan 기법은 수평방향의 음파방사에 의해 주로 발생하는 근거리 음영구역으로 해저반사를 통하여 음파를 전달시켰고, 근거리 음영 구역에 숨어있는 표적의 탐지가능성을 높였다. 또한 실제 산란환경을 고려한 수치실험 결과에서도 부분적으로 표적이 탐지가 됨으로써 HMS Verscan 기법의 근거리 음영구역의 감소효과를 확인하였다.

• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.54-60
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• 2000

Acoustic source localization using MUSIC etc. utilizes the propagation model in the medium. A plane wave model is a well-known source model for the identification of distant sources in the SONAR and a monopole source model becomes the one for the identification of rather near range sources. This paper introduces a dipole source model and a tripole source model consisting of one monopole and one dipole source. The simplifying procedures provide the simplified factors rather than the superposition of the relating monopole sources. The simulations show that the tripole model is useful in the general case including pure monopole, pure dipole, or pure quadrupole source identification.

• The Journal of the Acoustical Society of Korea
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• v.23 no.2
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• pp.125-133
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• 2004

Most of the way shape estimation method using reference sources assume that the reference sources are in the farfield. That is, the reference sources are assumed to be far from the array. However, in applications of the array with reference sources, the reference sources are not far from the way, so that in practical ocean environments, the conventional method using farfield source model fail to estimate the positions of the hydrophones. In this paper, based on the nearfield source model, a subspace-based array shape estimation method was proposed. In the proposed method, nearfield reference source is modeled using the differential time delay at each hydrophone, and nearfield parameters are derived. Using these parameters, a subspace-based array shape estimation method that generalizes the existing farfield subspace fitting method which can work regardless of the range of the source is proposed. The Cramer-Rao lower bound for the proposed method is investigated. The results of the numerical experiments indicate that the proposed method performs well in estimating the shape of a perturbed way regardless of the ranges of the reference sources.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.125-128
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• 1999

근거리음장 측정으로부터 원거리음장을 예측할 수 있는 이론적 모델 및 실험적 연구가 수행되고 있다. 본 논문에서 채택한 방법은 Helmholtz 적분식의 간단한 모델로써 단일주파수 코히어런트 음원의 근거리측정음장으로부터 원거리음장 예측이 가능한 기술이다. 이러한 단일 주파수, 코히어런트 음원의 원거리 수평방향지향성을 예측하기 위한 모델식 및 무향실에서 수행한 검증실험 결과를 소개한다 제안된 방법은 일반 소음원은 물론 잠수함 등의 수평방향 지향성의 예측에 적용가능하다고 판단된다.

• The Journal of Engineering Geology
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• v.31 no.2
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• pp.179-186
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• 2021

Malpasset Dam, located in France, is of great importance in the field of civil and geotechnical engineering as it was the first arch dam that totally collapsed in 1959. A three-dimensional model of the dam was reconstructed using close-range photogrammetry technique. The orientations of foliation developed in the bedrock and the collapse surface were measured. Moreover, both model and measurement results showed high precision. The study result can be used in future studies such as collapse simulation analysis and geotechnical investigations.

• Journal of Radiation Protection and Research
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• v.23 no.1
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• pp.1-6
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• 1998

A diffusion model of radioactive liquid effluents is developed and applied for YGN NPP's site, based on the Gaussian plume type model. Due to the complexity of oceanic diffusion characteristics of YGN site, a simple and reliable statistical model based on Reg. Guide 1.113 is developed. Also, a computer code package to calculate dilution factors as a function of plant operation conditions and pathway of radioactive materials. A liquid effluents diffusion model is developed by dividing the diffusion range into two categories, i. e, a near field mixing region and a far field mixing region. In the near field, the initial mixing is affected by a buoyance force, a high initial turbulence and momentum which is characterized by a plant operation condition and environmental conditions. The far field mixing is similar to gaseous effluents diffusion. So, beyond the near field region, wellknown Gaussian plume model was adopted. A different area averages of Gaussian plume equation was taken for each radioactive exposure pathway. As a result, we can get different dilution factors for different pathways. Results shows that present dilution factors used for YGN ODCM is too much overestimated compared with dilution factors calculated with the developed model.

• Journal of the Korea Computer Industry Society
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• v.3 no.5
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• pp.547-556
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• 2002

This paper was proposed a wave path loss prediction algorithm using multilayer perceptron (MLP) model and wave propagation characteristic parameters for Wireless LAN in indoor radio environments. Receiving power was predicted by calculating indoor path loss in a Wireless LAN that has transmission power of 100mW and frequency of 2.4GHz, and was compared with measured. In the result of measurement shows that there is a difference between predicted and measured receiving power which can be reduced by an accurate analysis of the various path loss factors. In order to fix the access point(AP) positions was used the proposed a wave path loss prediction algorithm, and designed the optimum cell for Wireless LAN.

• The Journal of the Acoustical Society of Korea
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• v.20 no.4
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• pp.71-80
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• 2001

In order to consider the sediment layer's effect to total acoustic field, we composed a 3 layered fluid model of 2 sediment layers by adding an additional layer to the Pekeris model and found solutions by using Green's function, boundary conditions and Sommerfeld radiation condition. The modes were divided into discrete modes and virtual modes, and confirmed that the characteristic equation to find discrete modes was same as that of Tolstoy and Clay for normal modes. Also, we confirmed that under similar conditions the 3 layered model showed same results as that of Pekeris model. We believe this 3 layered model can be used to study the sediment's effect on the virtual mode of near field.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.77-80
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• 2003

본 논문에서는 유비쿼터스 네트워킹을 위한 초고속 근거리 무선 전송기술로서 각광받고 있는 초광대역(Ultra Wideband : UWB) 통신 기술을 분석하고 실내 근거리 다중접속 환경 및 페이딩 환경에서의 시스템 성능을 분석하였다. 다중접속 간섭 환경은 UWB 시스템의 전송율과 간섭 수에 따른 시스템 성능을 분석하고, 페이딩 채널은 기존에 발표되었던 UWB 전파 실험을 통한 데이터를 바탕으로 Nakagami-m분포 모델을 이용하여 페이딩 지수 m에 따른 다양한 채널 환경을 고려하였다.