• Journal of Advanced Marine Engineering and Technology
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• 제30권1호
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• pp.73-80
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• 2006

In order to compute the radiated sound from a vibrating structure, the Rayleigh's integral equation has to be derived from the Helmholtz equation using Green's function. Generally, the surface velocity in the Rayleigh's integral equation uses the root mean square(rms) velocity. The calculation value is too large, because it's not considered cancelation. On the other hand. using the complex velocity, the sound pressure is calculated too small, because it considers that sound is perfectly canceled out. Therefore, this thesis proposes a correction factor(CF) which considers vibration modes and the method by which to calculate the radiating sound pressure. The theoretical results are compared with the experimental values, and the proposed method can be verified with confluence.

• 대한전자공학회논문지
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• 제8권6호
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• pp.17-24
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• 1971

본 논문에서는 임의의 형상을 가진 유전체 안테나에 대한 새로운 해석 방법을 기술한다. 이 방법에서는 분극 전류 및 뇌하 밀도의 개념을 종래의 Stratton-Chu 형식에 도입하고 산란 원칙에 따라 유전체 내의 전계강도에 대해 적분 방정식을 세웠다. 이 적분 방정식을 수치 계산법으로 풀기 위해 유전체의 체적을 세분하고 작은 구로서 등가적으로 표시한다. 따라서 이 방법에 의해서는 임의의 형상의 유전체 안테나의 해석이 가능하다. 이와같이 해서 유전체 내의 전계강도를 구하고 그 강도에 입각해서 안테나의 복사특성, 입력 임피이단스 및 유전체 손실들을 산출했다.

• Steel and Composite Structures
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• 제50권3호
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• pp.299-318
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• 2024

The main objective of this paper is to compute the far-field acoustic radiation (sound radiation) of functionally graded plates (FGM) loaded by sinusoidally varying point load subjected to the arbitrary boundary condition is carried out. The governing differential equations for thin functionally graded plates (FGM) are derived using classical plate theory (CPT) and Rayleigh integral using the elemental radiator approach. Four cases, segregated on power-law index k=0,1,5,10, are studied. A novel approach is illustrated to compute sound fields of vibrating FGM plates using the physical neutral surface with an elemental radiator approach. The material properties of the FGM plate for all cases are calculated considering the power law indexes. An in-house MATLAB code is written to compute the natural frequencies, normal surface velocities, and sound radiation fields are analytically calculated using semi-analytical formulation. Ansys is used to validate the computed sound power level. The parametric effects of the power law index, modulus ratios, different constituent of FGM plates, boundary conditions, damping loss factor on the sound power level, and radiation efficiency is illustrated. This work is the benchmark approach that clearly explains how to calculate acoustic fields using a solid layered FGM model in ANSYS ACT. It shows that it is possible to asymptotically stabilize the structure by controlling the intermittent layers' stiffness. It is found that sound fields radiated by the elemental radiators approach in MATLAB, ANSYS and literatures are in good agreement. The main novelty of this research is that the FGM plate is analyzed in the low-frequency range, where the stiffness-controlled region governs the whole analysis. It is concluded that a clamped mono-ceramic FGM plate radiates a lesser sound power level and higher radiation efficiency than a mono-metallic or metal-rich FGM plate due to higher stiffness. It is found that change in damping loss factor does not affect the same constituents of FGM plates but has significant effects on the different constituents of FGM plates.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.236-239
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• 2014

Most naval underwater weapon system can be simplified to a circular cylindrical structure which has vibrating machineries inside. In order to predict efficiently the total acoustic radiation power of cylindrical structure, surface velocity is measured and radiation efficiency of surface element is calculated. Then, they are substituted to the surface pressure in the simplified Helmholtz integral equation which assumes acoustic far-field and plane-wave approximation at the surface. Surface velocity and total acoustic radiation power for a submerged cylinder are measured in water-tank. In this example, it is found that total acoustic power output obtained from the prediction is in good agreement with that of measurement in mid-high frequency range.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1998년도 춘계 학술발표회 논문집
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• pp.235-242
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• 1998

Aiming at one of decisive alternatives for long term aspect of nuclear power concerns, an integral and closed nuclear system, AMBIDEXTER (Advanced Molten-salt Break-even Inherently-safe Dual-mission Experimental and TEst Reactor) concept is under development. The AMBIDEXTER complex essentially comprises two mutually independent loops of the radiation/material transport and the heat/energy conversion, centered at the integrated reactor assembly, which enables one to utilize maximum benefits of nuclear energy under minimum risks of nuclear radiation. And it provides precious radioisotopes and radiation sources from its waste stream. Also the reactor operates at very low level of fission products inventory throughout its lifetime. The nuclear and thermalhydraulic characteristics of the molten TH/$^{233}$ U fuel salt extend the capability of the self-sustaining AMBIDEXTER fuel cycle to enhance resource security and safeguard transparency. The reactor system is consisted of a single component module of the core, heat exchangers and recirculation pumps with neither pipe connections nor active valves in between, which will significantly improve inherent features of nuclear safety. States of the core technologies associated with designing and developing the AMBIDEXTER concept are mostly available in commercialized form and thus demonstration of integral aspects of the concept should be the prime area in future R＆D programs.

• 한국전자파학회지:전자파기술
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• 제5권2호
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• pp.20-28
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• 1994

컬러게이트 혼 안테나의 이론적 복사패턴을 벡터적분법과 준 광학모드 이론으로써 각각 구하였다. 혼 개구면에 존재하는 하이브리드 모드의 전자계를 등가 전류원으로 대체하고 포텐셜 이론을 적용하는 벡터 적분법으로 안테나의 복사 전계식을 계산 하였다. 또한, 준 광학모드인 Gaussian-Laguerre 모드를 확장하여 복사 관력식을 유도하였다. 85-115GHz에서 동작하는 컬러게이트 혼 안테나에 대한 복사패턴을 벡터적분법 및 준 광학방법으로 계산하고 비교한 결과 중심 주파수인 100GHz에서는 거의 일치하였으나 85 및 115GHz에서는 다소의 오차가 발생하였다.

• Journal of Ship and Ocean Technology
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• 제10권1호
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• pp.10-26
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• 2006

The radiation problem for oscillating bodies on the free surface has been formulated by the over-determined Green integral equation, where the boundary condition on the free surface is satisfied by adopting the Kelvin-type Green function and the irregular frequencies are removed by placing additional control points on the free surface surrounded by the body. The B-Spline based higher order panel method is then applied to solve the problem numerically. Because both the body geometry and the potential on the body surface are represented by the B-Splines, that is in polynomials of space parameters, the unknown potential can be determined accurately to the order desired above the constant value. In addition, the potential expressed in B-Spline can be differentiated analytically to get the velocity on the surface without introducing any numerical error. Sample computations are performed for a semispherical body and a rectangular box floating on the free surface for six-degrees of freedom motions. The added mass and damping coefficients are compared with those by the already-validated constant panel method of the same formulation showing strikingly good agreements.

• 한국음향학회지
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• 제14권4호
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• pp.82-88
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• 1995

배플이 없는 폴리우레탄 유한 윈도우를 장착한 사각형 음향 센서의 수중 음향방사로 인한 자기방사 임피던스 (self-radiation impedance)의 컨덕턴스(conductance)와 서셉턴스(susceptance)를 실험으로 계측 하여 이를 전기적 등가회로를 이용하여 수중방사 임피던스 양을 계산하였다. 또한 무한배플(rigid infinite baffle)의 사각형 피스톤을 모델로 선정한 Levine식을 이용하여 음향방사로 인한 자기방사 임피던스를 적분식으로 표시하고 이것을 방사 저항과 방사 리액턴스로 분리하여 수치해석하였다. 실험의 경계조건과 비유적 유사한 이론해석 결과를 실험치와 비교하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.743-747
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• 2003

In recent years, several studies of the practical application of active sound and vibration control have been developed to plate to plate response with various boundary conditions. This study considers vibration and sound radiation for the clamped rectangular plate. The radiation of a sound from rectangular plate can be calculated that the velocity of a vibrating plate is analyzed. The vibration formulation is based on a variation method for the vibration of the plate, and assumes no damping, no fluid loading of the structure. And the plate is exited by harmonic point force. The radiation of sound from plate is analyzed in the far field, and is calculated from the Rayleigh integral. The prediction results of vibration and sound level have proved with FEM or BEM.

• 한국해양환경ㆍ에너지학회지
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• 제13권2호
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• pp.83-90
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• 2010

해양파 중에서 2개 선체가 가까운 거리에 계류되어있는 경우에 2선체의 운동을 엄밀한 파 중 2 부유체 운동이론에 의하여 계산하였다. 2 선체의 방사 및 산란파 포텐셜은 특이파 수 현상이 없는 주파수영역 Improved Green 적분방 정식으로부터 구하였다. 규칙파 중에서 근접한 2선체가 서로 연결되지 않은 경우와 강체 연결장치로 병렬 계류된 된 경우의 운동 및 강체연결체에 작용하는 6방향 힘과 모오멘트를 해석하는 기법과 수치실험 결과도 보였다.