• 한국소음진동공학회논문집
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• 제24권11호
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• pp.907-918
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• 2014

In this study for the prediction of 3D underwater radiated noise pattern, a comparison between the proposed method(DHIE, Discrete Helmholtz Integral Equation) and the 3D underwater radiated noise calculation results using the measurement of near-field acoustic pressure data is performed. The near-field acoustic pressure in water is measured for the calculation of the far-field radiated noise pattern and the far-field acoustic power. Also the vibration field of the underwater structure is measured in simultaneously. Using the total far-field acoustic power and the vibration field on the surface of the structure, the proposed method(DHIE) can predict the underwater radiated noise pattern of the far-field The predicted results show the reasonable agreement within about 5dB comparing with the experiment result.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1305-1306
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• 2013

• Water Engineering Research
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• 제1권2호
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• pp.137-146
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• 2000

A windows-based software package, named DREDGE, is developed for estimating sediment resuspension and contaminant release during dredging operations. DREDGE allows user to enter the necessary dredge information, site characteristics, operational data, and contaminant characteristics, then calculates an array of concentration using the given values. The program mainly consists of the near-field models, which are obtained empirically, for estimating sediment resuspension and the far-field models, which are obtained analytically, for suspended sediment transport. A linear equilibrium partitioning approach is applied to estimate particulate and dissolved contaminant concentrations. This software package which requires only a minimal amount of data consists of three components; user input, tabular output, and graphical output. Combining the near-field and far-field models into a user-friendly windows-based computer program can greatly save dredge operator's, planners', and regulators' efforts for estimating sediment transports and contaminant distribution.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.443-450
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• 2000

In this study a numerical method for soil-pile interaction analysis buried in multi-layered half planes is presented in frequency domain using FE-BE coupling. The total soil-pile interaction system is divided into two parts so called far field and near field beam elements are used for modeling a pile and coupled with plain strain elements for soil modeling. Boundary element formulation using the multi-layered dynamic fundamental solution is adopted to the far field and coupled with near field modeled by finite elements. In order to verify the proposed soil-pile interaction analysis method the dynamic responses of a pile on multi-layered dynamic fundamental solution is adopted to the far field and coupled with near field modeled by finite elements. In order to verify the proposed soil-pile interaction analysis method the dynamic responses of a pile on multi-layered half-planes are performed and compared with experiment results. Through this developed method the dynamic response analysis of a pile buried in multi-layered half planes can be calculated effectively in frequency domain.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 춘계학술대회 논문집
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• pp.136-143
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• 2001

In this study, a numerical analysis for soil-pile interaction systems in multi-layered half planes under a forced vibration is presented. The soil-pile interaction system is divided into two parts, so called near field and far field. The near field soil using finite elements and piles using beam elements are modeled. The far field soil media is implemented using boundary elements those can automatically satisfy the condition of wave radiation. These two fields are numerically coupled by imposing displacement compatibility condition at the interface between the near field and the far field. For the verification, the forced vibration test was simulated and the response under horizontal and vertical harmonic loads at the pile cap in the layered half plane was determined. The results are compared to the theoretical and experimental results of the literatures to verify the proposed soil-pile interaction analysis formulation.

• Earthquakes and Structures
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• 제18권5호
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• pp.625-635
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• 2020

Suspension bridges have the extended in plan configuration which makes them prone to dynamic events like earthquake. The longer span lead to more flexibility and slender of them. So, control systems seem to be essential in order to protect them against ground motion excitation. Tuned mass damper or in brief TMD is a passive control system that its efficiency is practically proven. Moreover, its parameters i.e. mass ratio, tuning frequency and damping ratio can be optimized in a manner providing the best performance. Meta-heuristic optimization algorithm is a powerful tool to gain this aim. In this study, TMD parameters are optimized in different-length suspension bridges in three distinct cases including 3, 4 and 5 TMDs by observer-teacher-learner based algorithm under a complete set of ground motions formed from both near-field and far-field instances. The Vincent Thomas, Tacoma Narrows and Golden Gate suspension bridges are selected for case studies as short, mean and long span ones, respectively. The results indicate that All cases of used TMDs result in response reduction and case 4TMD can be more suitable for bridges in near and far-field conditions.

• 한국인터넷방송통신학회논문지
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• 제22권2호
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• pp.43-50
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• 2022

본 논문에서는 밀리미터파 W대역에서 동작하는 안테나 성능 측정을 위한 원-전계 측정 시스템을 설계하고 검증하였다. 안테나 성능 시험은 안테나의 종류, 측정 항목, 측정 환경 및 기간 등에 따라 측정 시스템을 선택해야 한다. 근접 전계 측정은 안테나가 다중 채널을 가지거나 다양한 빔을 가지고 있을 경우, 측정 항목이 증가하기 때문에 많은 시간이 소요된다. 이러한 안테나는 원-전계 측정을 통해 측정 시간을 단축 할 수 있고 필요한 측정 항목만 측정이 가능하다. 따라서 본 연구는 원-전계 측정 시스템을 고출력 레이저를 이용하여 정밀한 정렬을 확보하고 이중 증폭기 시스템을 적용하여 측정 정확도를 향상하였다. 설계된 시스템은 무반향 챔버 내 구축하였으며 검증된 근접 전계 측정 시스템과 비교하여 검증하였다.

• Structural Engineering and Mechanics
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• 제15권6호
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• pp.717-733
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• 2003

A time domain method is presented for soil-structure interaction analysis under seismic excitations. It is based on the finite element formulation incorporating infinite elements for the far field soil region. Equivalent earthquake input forces are calculated based on the free field responses along the interface between the near and far field soil regions utilizing the fixed exterior boundary method in the frequency domain. Then, the input forces are transformed into the time domain by using inverse Fourier transform. The dynamic stiffness matrices of the far field soil region formulated using the analytical frequency-dependent infinite elements in the frequency domain can be easily transformed into the corresponding matrices in the time domain. Hence, the response can be analytically computed in the time domain. A recursive procedure is proposed to compute the interaction forces along the interface and the responses of the soil-structure system in the time domain. Earthquake response analyses have been carried out on a multi-layered half-space and a tunnel embedded in a layered half-space with the assumption of the linearity of the near and far field soil region, and results are compared with those obtained by the conventional method in the frequency domain.

• Structural Engineering and Mechanics
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• 제72권3호
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• pp.395-408
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• 2019

Engineered structures built in seismic-prone areas are affected by aftershocks in addition to mainshocks. Although aftershocks generally are lower in magnitude than that of the mainshocks, some aftershocks may have higher intensities; thus, structures should be able to withstand the effect of strong aftershocks as well. This seismic scenario arises for far-field mainshock along with near-field aftershocks. In this study, four 2D reinforced concrete (RC) frames with different numbers of stories were designed in accordance with the current Iranian seismic design code. As a way to evaluate the seismic response of the case-study RC frames, the inter-story drift ratio (IDR) demand, the residual inter-story drift ratio (RIDR) demand, the Park-Ang damage index, and the period elongation ratio can be useful engineering demand parameters for evaluating their seismic performance under mainshock-aftershock sequences. The frame models were analyzed under a set of far-field mainshock, near-fault aftershocks seismic sequences using nonlinear dynamic time-history analysis to investigate the relationship among IDR, RIDR, Park-Ang damage index and period ratio experienced by the frames. The results indicate that the growth of IDR, RIDR, Park-Ang damage index, and period ratio in high-rise and short structures under near-fault aftershocks were significant. It is evident that engineers should consider the effects of near-fault aftershocks on damaged frames that experience far-field mainshocks as well.

• 한국정보전자통신기술학회논문지
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• 제2권1호
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• pp.65-72
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• 2009

기지국 배열안테나의 근역장 프로빙을 통해 원역장 성능을 평가하기 위해 반사판을 갖는 다이폴 배열 안테나와 프로브 사이 높이에 따른 상호 간의 영향을 분석하였다. 기본 개념은 기지국 배열 안테나의 입력단들과 프로브의 입력 port P 에 대한 근역장에서의 상호 높이를 변화시키며 S 파라미터 측정값을 분석하여 상호결합 효과가 가장 적으면서 프로빙 효율이 높은 위치를 결정하는 것이다. 그리고 여기서 얻어진 높이는 기지국 배열안테나의 정밀한 원역장 성능을 구하기 위한 근역장 프로빙 시스템 설계에 적용 가능할 것이다.