• 한국소음진동공학회논문집
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• 제14권8호
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• pp.718-725
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• 2004

If a wall separates the bounded and unbounded spaces, then the wall’s role in transporting the acoustic characteristics of the two spaces is not well defined. In this paper, we attempted to see how the acoustic characteristics of two spaces are really affected by the spatial characteristics of the wall. In order to understand coupling mechanism, we choose a finite space and a semi-infinite space separated by the flexible or rigid wall and an opening. A volume interaction can be occurred in structure boundary and a pressure Interaction can be happened in the opening boundary. For its simplicity, without loosing generality, we use rather simplified rectangle model instead of generally shaped model. The source impedance is presented to the various types of boundaries. The distributions of pressure and active intensity are also presented at the cavity- and structure-dominated modes. The resulting modification, shifts of modal frequencies and changing of standing wave patterns to satisfy both coupled boundary conditions and governing equations, are presented.

• Coupled systems mechanics
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• 제9권2호
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• pp.125-145
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• 2020

In this paper, we present a 3D thermo-hydro-mechanical coupled discrete beam lattice model of structure built of the nonisothermal saturated poro-plastic medium subjected to mechanical loads and nonstationary heat transfer conditions. The proposed model is based on Voronoi cell representation of the domain with cohesive links represented as inelastic Timoshenko beam finite elements enhanced with additional kinematics in terms of embedded strong discontinuities in axial and both transverse directions. The enhanced Timoshenko beam finite element is capable of modeling crack formation in mode I, mode II and mode III. Mode I relates to crack opening, mode II relates to in-plane crack sliding, and mode III relates to the out-of-plane shear sliding. The pore fluid flow and heat flow in the proposed model are governed by Darcy's law and Fourier's law for heat conduction, respectively. The pore pressure field and temperature field are approximated with linear tetrahedral finite elements. By exploiting nodal point quadrature rule for numerical integration on tetrahedral finite elements and duality property between Voronoi diagram and Delaunay tetrahedralization, the numerical implementation of the coupling results with additional pore pressure and temperature degrees of freedom placed at each node of a Timoshenko beam finite element. The results of several numerical simulations are presented and discussed.

• 전기학회논문지
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• 제56권8호
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• pp.1430-1435
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• 2007

We developed a 440MHz surface acoustic wave (SAW) microsensor integrated with pressure-temperature sensors and ID tag. Two piezoelectric substrates were bonded, in which ${\sim}150\;{\mu}m$ cavity was structured. Four sides were completely sealed by JSR photoresist (PR). Pressure sensor was placed on the top substrate, whereas ill tag and temperature sensor were placed on the bottom substrate. Using network analyzer, the developed microsensor was wirelessly tested. Sharp reflection peaks with high S/N ratio, small signal attenuation, and small spurious peaks were observed. All the reflection peaks were well matched with the coupling of mode (COM) simulation results. With a 10mW RF power from the network analyzer, a ${\sim}1$ meter readout distance was observed. Eight sharp ON reflection peaks were observed for ID tag. Temperature sensor was characterized from $20^{\circ}C$ to $200^{\circ}C$. A large phase shift per unit temperature change was observed. The evaluated sensitivity was ${\sim}10^{\circ}/^{\circ}C$.

• Structural Engineering and Mechanics
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• 제85권2호
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• pp.247-263
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• 2023

The paper deals with the study of the mechanical time-harmonic forced vibration of the hydro-piezoelectric system consisting of the piezoelectric plate and compressible viscous fluid with finite depth. The exact equations of motion of the theory of linear electro-elasticity for piezoelectric materials are employed for describing the plate motion, however, the fluid flow is described by employing the linearized Navier-Stokes equations for a compressible (barotropic) viscous fluid. The plane-strain state in the plate and the plane flow of the fluid are considered and the corresponding mathematical problems are solved by employing the Fourier transform with respect to the space coordinate which is on the coordinate axis directed along the platelying direction. The expressions of the corresponding Fourier transform are determined analytically, however, the inverse transforms are found numerically. Numerical results on the interface pressure and the electrical potential are obtained for various PZT materials and these results are discussed. According to these results, in particular, it is established that the electromechanical coupling effect can significantly decrease the interface pressure.

• 공업화학
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• 제3권2호
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• pp.256-265
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• 1992

NaCl(30wt%)/ZnO(60wt%)/${\alpha}-Al_2O_3$ 촉매상에서 메탄의 oxidative coupling 반응의 속도식을 연구하여 활성 산소종에 관하여 고찰하였다. 반응온도 $650^{\circ}C$에서 $750^{\circ}C$까지 메탄의 전화율 10%미만의 범위에서 메탄과 산소의 분압을 변화시켜 가면서 메탄의 전환속도를 측정하여 속도식을 검증하였다. 제안된 메틸라디칼의 생성반응은 Langmuir-Hinshelwood형 반응기구를 따른다. 촉매표면의 서로 다른 활성점에 흡착된 메탄분자와 산소분자가 반응하여 메틸라디칼이 생성되는 반응이 속도결정단계이며, 이때 활성화 에너지는 약 39kcal/mol이었다. 메탄의 C-H 결합의 해리에 관여하는 산소종은 표면상의 이원자 산소인 $O{_2}{^{2-}}$나 $O_2{^-}$로 제시할 수 있었다.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2471-2478
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• 2020

Pumps are essential machinery in the various industries. With the development of high-speed and large-scale pumps, especially high energy density, high requirements have been imposed on the vibration and noise performance of pumps, and cavitation is an important source of vibration and noise excitation in pumps, so it is necessary to improve pumps cavitation performance. The modern pump optimization design method mainly adopts parameterization and artificial intelligence coupling optimization, which requires direct correlation between geometric parameters and pump performance. The existing cavitation performance calculation method is difficult to be integrated into multi-objective automatic coupling optimization. Therefore, a fast prediction method for pump cavitation performance is urgently needed. This paper proposes a novel cavitation prediction method based on impeller pressure isosurface at single-phase media. When the cavitation occurs, the area of pressure isosurface S_iso increases linearly with the NPSH_a decrease. This demonstrates that with the development of cavitation, the variation law of the head with the NPSH_a and the variation law of the head with the area of pressure isosurface are consistent. Therefore, the area of pressure isosurface S_iso can be used to predict cavitation performance. For a certain impeller blade, since the area ratio R_s is proportional to the area of pressure isosurface S_iso, the cavitation performance can be predicted by the R_s. In this paper, a new cavitation performance prediction method is proposed, and the feasibility of this method is demonstrated in combination with experiments, which will greatly accelerate the pump hydraulic optimization design.

• 화약ㆍ발파
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• 제36권4호
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• pp.35-47
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• 2018

본 연구에서는 콘크리트 블록발파 실험과 AUTODYN 수치해석을 통해 몇 가지 전색제 및 충전재가 폭발결과에 미치는 효과를 분석하였다. 전색제와 충전재는 공기, 모래, 폴리머 겔을 이용하였다. 이들 재료들의 전색효과 및 충전효과는 밀장전 조건의 경우와 비교하였다. 매립된 콘크리트 블록을 사용하여 현장 누두공 시험을 실시하였다. 콘크리트 블록 실험 및 수치해석 결과 폴리머 겔을 사용한 경우가 모래 및 디커플링의 경우에 비해 누두공의 크기와 발파공 주위의 최대압력이 더 크게 나타나는 것을 확인하였다. 또한, 수치해석 결과는 현장시험 결과와 잘 일치하는 경향을 보여주었다. 주변암반 중에서 계산된 최대압력은 폴리머 겔, 모래, 무전색 및 디커플링 조건일 때 각각 37, 30, 16 MPa로 나타났다. 수치해석 모델 내 밀장전 시 최대 압력은 52 MPa로 가장 높게 나타났다. 그러나 손상영역의 크기는 폴리머 겔을 사용한 경우보다 작게 나타났다. 또한, 밀장전은 기준 실험으로 사용되었다.

• Journal of Mechanical Science and Technology
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• 제15권5호
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• pp.555-561
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• 2001

A new approach to analyze the multi-domain acoustic system divided and enclosed by flexible structures is presented in this paper. The boundary element formulation of the Helmholtz integral equation is used for the internal fields and the finite element formulation for the structures surrounding the fields. We developed a numerical analysis program for the structural-acoustic coupling problems of the multi-domain system, in which boundary conditions such as the continuity of normal particle velocity and sound pressure in the structural interfaces between Field 1 and Field 2 are not needed. The validity of the numerical analysis program is verified by comparing the numerical results with the experimental ones. Example problems are included to investigate the characteristics of the coupled multi-domain system.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.21-31
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• 1998

In this paper, a thermo-mechanical model for viscous coupling(VC) was suggested and torque equation in viscous mode was derived considering the effects of geometry of the plates, thermo-mechanical dynamics, silicon oil characteristics and dissolved air characteristics in the silicon oil. Theoretical results were in good accordance with experimental results demonstrating that VC thermo-mechanical model and the theoretical equations, response of the torque transmitted, pressure, temperature and time to the hump were investigated. Simulation results showed that filling rate of the silicon oil plays an integral role not only in the steady state torque characteristics but also in determining the time to hump.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.797-801
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• 2003

The Statistical Energy Analysis is based on the power flow and the energy conservation between sub-systems, which enable the prediction of acoustic and structural vibration behavior in mid-high frequency ranges. This paper discusses the identification of SEA coupling loss factor parameters from experimental measurements of small reverberation chamber sound pressure levels and structural accelerations. As structural subsystems, steel plates with and without damping treatment are considered. Calculated CLFs were verified by both transmission loss values for air-borne CLF case and running SEA commercial software As a result, CLFs have shown a good agreement with those computed by software. Acoustical behavior of air-borne noise and structure-borne noise has been examined. which shows reasonable results, too.