• 한국전산유체공학회지
• /
• 제19권4호
• /
• pp.68-74
• /
• 2014

This computational study features the transient compressible and inviscid flow analysis on a metallic plasma discharge from the opposing composite electrodes which is subjected to pulsed electric power. The computations have been performed using the flux corrected transport algorithm on the axisymmetric two-dimensional domain of electrode gap and outer space along with the calculation of plasma compositions and thermophysical properties such as plasma electrical conductivity. The mass ablation from aluminum electrode surfaces are modeled with radiative flux from plasma column experiencing intense Joule heating. The computational results shows the highly ionized and highly under-expanded supersonic plasma discharge with strong shock structure of Mach disk and blast wave propagation, which is very similar to muzzle blast or axial plasma jet flows. Also, the geometrical effects of composite electrodes are investigated to compare the amount of mass ablation and penetration depth of plasma discharge.

• 대한의용생체공학회:의공학회지
• /
• 제28권4호
• /
• pp.471-476
• /
• 2007

Various active microwave imaging techniques have been developed for cancer detection for past several decades. Both the microwave tomography and the UWB radar techniques, constituting functional microwave imaging systems, use the electrical property contrast between normal tissues and malignancies to detect the latter in an early development stage. Even though promising simulation results have been reported, the understanding of the functional microwave imaging diagnostics has been relied heavily on the complicated numerical results. We present a computationally efficient and physically instructive analytical electromagnetic wave channel models developed for functional microwave imaging system in order to detect especially the breast tumors as early as possible. The channel model covers the propagation factors that have been examined in the previous 2-D models, such as the radial spreading, path loss, partial reflection and transmission of the backscattered electromagnetic waves from the tumor cell. The effects of the system noise and the noise from the inhomogeneity of the tissue to the reconstruction algorithm are modeled as well. The characteristics of the reconstructed images of the tumor using the proposed model are compared with those from the confocal microwave imaging.

• 한국지진공학회논문집
• /
• 제1권3호
• /
• pp.45-58
• /
• 1997

지진하중을 받는 현수교의 기하비선형 거동특성을 분석하기 위하여 비선형 지진응답해석 알고리즘을 정립하고 그에 따른 전산프로그램을 개발하였다. 해석이론을 최근 시도되고 있는 자정식 현수교나 mono-duo 형식의 주케이블 형상을 갖는 독특한 현수교에 대해서는 적용가능하도록 유한요소법을 사용하였다. 입력지진은 장지간 교량의 다중지지효과를 고려하기 위하여 한 지점에서 다른쪽 지점으로 형상변화 없이 이동한다고 가정하였다. 하나의 mono-duo 자정식 현수교에 대하여 비선형 지진해석을 수생한 결과 예제의 교량이 비교적 단지간이어서 비선형 거동특성과 다중지지 효과가 두드러지게 나타나지는 않음을 확인할 수 있었다.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2010년 춘계학술대회논문집
• /
• pp.326-334
• /
• 2010

In this study, we provide a comprehensive review of the CIP(Constrained Interpolation Pro file/Cubic Interpolated Propagation) method with a pressure-based algorithm that is known as a general numerical solver for soled liquid, gas and plasmas. And also we introduce a body-fitted grid system(Soroban grid) for computation of strongly nonlinear marine hydrodynamic problems such as slamming water on deck, wave impact by green water. This grid system can keep the third-order accuracy in time and space with the help of the CIP method. The grid system consists of the straight lines and grid points. In the 2-dimensional grid case, each grid points moving in these lines like abacus - Soroban in Japanese. The length of each line can be different and the number of grid points in each line can be different. Mesh generation and searching of upstream departure point are very simple and possible to mesh-free treatment. To optimize computation of free-surface and multi-fluid flows, We adopt the C-CUP method. In most of the earlier computations, the C-CUP method was used with a staggered-grid approach. Here, because of the mesh free nature of the Soroban grid, we use the C-CUP method with a collocated-grid approach.

• 한국음향학회지
• /
• 제24권6호
• /
• pp.334-342
• /
• 2005

본 논문에서는 지난 2004년 동해에서 수행된 MAPLE 04 실험에서 수집된 일련의 전구음원 신호 중 일부를 이용하여 시간 영역에서 지음향 인자 역산을 수행하였다. 이를 위해 수직선배열을 통해 수집된 채널 별 신호 파형과 모의 신호 파형을 직접 비교하는 형태의 목적함수를 구성하였다. 모의 신호는 음선 이론을 사용하여 모델링하였고, 광역최적화 알고리즘인 VFSA (very fast simulated annealing)를 사용하여 목적함수를 최적화하였다 기존의 전달손실비교를 통한 역산 결과(음향학회지 본 호 게재)들과 비교하여 지음향 인자들이 일관성 있게 추정되었음을 확인하였으며, 이 역산 결과를 이용하여 얻은 모의 신호와 계측 신호 간 비교 그림을 제시하였다.

• 한국지구물리탐사학회:학술대회논문집
• /
• 한국지구물리탐사학회 2006년도 공동학술대회 논문집
• /
• pp.265-270
• /
• 2006

지중 레이다 탐사에서 고주파수 전자파의 전파 현상은 복잡하다. 전자파 전파에 현상을 지배하는 물리적인 과정에 대한 이해를 향상시키기 위해서, 본 논문에서는 원통좌표계 맥스웰 방정식의 시간영역 유한차분법을 소개한다. 이 접근법은 시추공 지중 레이다탐사와 관련된 전자 파동장의 전파형을 모델화할 수 있다. 이 알고리듬은 완전정합층(PML)을 통한 흡수경계, 주파수 의존성 매질, 그리고 유한 길이 송신 안테나에서 쉽게 이행될 수 있다.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제49권8호
• /
• pp.442-450
• /
• 2000

Active noise control is an approach to noise reduction in which a secondary noise source that destructively interferes with the unwanted noise. In general, active noise control systems rely on multiple sensors to measure the unwanted noise field and the effect of the cancellation. This paper develops an approach that utilizes a single sensor. The noise field is modeled as a stochastic process, and a time-adaptive algorithm is used to adaptively estimate the parameters of the process. Based on these parameter estimates, a canceling signal is generated. Opppenheim model assumed that transfer function characteristics from the canceling source to the error sensor is only propagation delay. But this paper proposes a modified Oppenheim model by considering transfer characteristics of acoustic device and noise path. This transfer characteristics is adaptively cancelled by adaptive model. This is proved by computer simulation with artifically generated random noise and sine wave noise. The details of the proposed architecture, and theoretical simulation and experimental results of the noise cancellation system for three dimension enclosure are presented in the paper.

• Smart Structures and Systems
• /
• 제5권4호
• /
• pp.457-468
• /
• 2009

A novel approach for integrating active sensing data interrogation algorithms for structural health monitoring (SHM) applications is presented. These algorithms cover Lamb wave propagation, impedance methods, and sensor diagnostics. Contrary to most active-sensing SHM techniques, which utilize only a single signal processing method for damage identification, a suite of signal processing algorithms are employed and grouped into one package to improve the damage detection capability. A MATLAB-based user interface, referred to as HOPS, was created, which allows the analyst to configure the data acquisition system and display the results from each damage identification algorithm for side-by-side comparison. By grouping a suite of algorithms into one package, this study contributes to and enhances the visibility and interpretation of the active-sensing methods related to damage identification. This paper will discuss the detailed descriptions of the damage identification techniques employed in this software and outline future issues to realize the full potential of this software.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2003년도 춘계학술대회 논문집
• /
• pp.341-344
• /
• 2003

There communicates using tire supersonic waves in tire underwater, that is different from tire ground that use tire propagation. Because using Law frequency to come under tire waves, bandwidth that is able to communicate is very smaller that tire mobile communication of tire ground. Also, The channel environment changes rapidly in tire shallow underwater than tire ground. Due to such a reason, data transmission technic that is able to tire maximum application to restricted bandwidth and tire signal processing technics that is able to conquer tire rapid changes of tire channel environment are being used. Algorithm is used at tire application of these technic has a lot of tire calculating quantity. So this research reveals small bulk and equal performance using one DSP chip and then implements QPSK transmitter, that uses SHARC DSP of Analog Device company, for tire underwater supersonic waves communication rapidly decrease tire calculating quantity.

• Geomechanics and Engineering
• /
• 제13권3호
• /
• pp.411-429
• /
• 2017

A Spectral Element Method for 3D seismic wave propagation simulation is derived based on the three-dimensional fluctuating elastic dynamic equation. Considering the 3D real terrain and the attenuation characteristics of the medium, the topographic effect of Wenchuan earthquake is simulated by using the Spectral Element Method (SEM) algorithm and the ASTER DEM model. Results show that the high PGA (peak ground acceleration) region was distributed along the peak and the slope side away from the epicenter in the epicenter area. The overall distribution direction of high PGA and high PGV (peak ground velocity) region is parallel to the direction of the seismogenic fault. In the epicenter of the earthquake, the ground motion is to some extent amplified under the influence of the terrain. The amplification effect of the terrain on PGA is complicated. It does not exactly lead to amplification of PGA at the ridge and the summit or attenuation of PGA in the valley.