• 소음진동
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• 제9권3호
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• pp.517-524
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• 1999

Mathematical formulas for multi-dimensional isolation analysis via vibrational power transmission can be derived in a rather simple form when the wave effects of the isolators are completely neglected. With increase of frequency range of interest, however, the wave effects play a very important role and hence cannot be neglected. The formulas get involved accordingly. In this study, a method of equivalent stiffness modeling of the isolators to include the wave effects is proposed in such a way that not only the complexity of the mathematical expressions but also that of experiments of necessity can be reduced. This method is illustratively applied to a two-dimensional vibration isolation system with nonrigid source and base structures.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.457-467
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• 2004

Wave Transmission analysis is one of methods for power transmission and reflection coefficients in coupled infinite structures. This paper focuses the wave transmission analysis of point coupled structures among semi-infinite beams and infinite thin plates considering all kinds of waves. It is supposed that the junction through the beams and plates is an identical spot and no point of contact exist except the spot. The boundary conditions are applied at the spot for continuities of 6 DOF displacements and 6 DOF force equilibriums, and then wave fields are obtained in the coupled structures. Since wave components in plate field are simplified using asymptotic expressions of Henkel functions, the displacements and forces at the plate junction can be simply expressed with magnitudes of the wave components. The wave fields according to incident waves gives the power transmission coefficients in beam/plate point coupled structures. For both coupled structures with a beam vertically and obliquely joined to a plate, power transmission analysis is performed and the analysis results are compared and examined.

• Journal of Advanced Marine Engineering and Technology
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• 제22권5호
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• pp.670-679
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• 1998

The solution of hyperbolic equation with wave nature has sharp discontinuties in the medium at the wave front. Difficulties encounted in the numrtical solution of such problem in clude among oth-ers numerical oscillation and the representation of sharp discontinuities with good resolution at the wave front. In this work inviscid Burgers equation and modified heat conduction equation is intro-duced as hyperboic equation. These equations are caculated by numerical methods(explicit method MacCormack method Total Variation Diminishing(TVD) method) along various Courant numbers and numerical solutions are compared with the exact analytic solution. For inviscid Burgers equa-tion TVD method remains stable and produces high resolution at sharp wave front but for modified heat Conduction equation MacCormack method is recommmanded as numerical technique.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.316-318
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• 2003

양자우물 구조를 사용한 HEMT(High Electron Mobility Transistor)는 고속 스위칭 소자와 초고주파 통신용 소자 및 센서에에 우수한 동작특성을 갖고 있다. 본 논문에서는 AlInAs/InP HEMT의 heterostructure를 파동방정식과 Poisson 방정식을 self-consistent 한 방법으로 해석하였다. 파동방정식으로 junction의 전자농도를 계산하고, Poisson 방정식을 해석하여 potential profile에 의한 전자 농도가 heterostructure에서 self-consistent가 되도록 연산하였다. 끝으로 AlInAs/InP 구조에서 positively ionized donor, valance band에서의 hole, conduction band의 free electron과 구조내의 2DEG를 AlGaAs/GaAs 및 AlGaAs/InGaAs/GaAs와 비교하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.957-959
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• 2014

The wave analysis of cylinders combined rigidly with a finite plate to identify the effect of the plate on the wave propagation. This paper uses the mobility and impedance coupling method to combine a infinite-length cylinder with the plate, and obtains the coupling forces induced by the vibration of the structure. The waveguide finite element method is used to calculate the wave characteristics of the cylinder excited by the forces. From the results, the dispersion diagram can be obtained. It contains the characteristics induced by the vibration and length of the internal plate. It also shows the wave propagation of elastic waves sustained in the cylinder.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1338-1342
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• 2006

This paper presents the theoretical approach to describe the wave propagation in the waveguide with varying cross-section. The waveguides considered in this paper are stepped-rod, tapered-rod, and stepped rod with a tapered section at the middle of wave-transmission. The wave transmission ratio for displacement, stress, and power was calculated for these three rods. The distribution of the stress and displacement along the stepped rod with a tapered section was calculated and compared with the results obtained by FEM analysis.

• 한국소음진동공학회논문집
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• 제24권12호
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• pp.999-1006
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• 2014

Mindlin plate theory includes the shear deformation and rotatory inertia effects which cannot be negligible as exciting frequency increases. The statistical methods such as energy flow analysis(EFA) and statistical energy analysis(SEA) are very useful for estimation of structure-borne sound of various built-up structures. For the reliable vibrational analysis of built-up structures at high frequencies, the energy transfer relationship between out-of-plane waves and in-plane waves exist in Mindlin plates coupled at arbitrary angles must be derived. In this paper, the new wave transmission analysis is successfully performed for various energy analyses of Mindlin plates coupled at arbitrary angles.

• 한국진공학회지
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• 제1권1호
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• pp.60-66
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• 1992

초격자와 다양자우물이 가질 수 있는 모든 구조에 대한 subband와 입자의 envelope 파동함수를 계산할 수 있는 방법을 제시하고 단순조성 초격자와 $\delta$-dopping 초격 자에 적용한 결과를 다른 방법의 계산결과와 비교하여 그 타당성을 검토하였다. 나아가서 기존의 방법에서 요구되었던 일정한 유효질량의 가정없이 graded gap 초격자에 적용하여 입자의 유효질량의 연속변화에 따른 subband 에너지와 파동함수를 계산하였다.

• 한국산업융합학회 논문집
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• 제7권1호
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• pp.5-11
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• 2004

벽면에 충돌하는 액체 분무의 충돌 거동과 액적 비산에 관하여 실험을 통하여 조사하였다. 액체 분무는 홀노즐에 의해 직경 40mm의 충돌판에 분사하게 된다. 액체 분무는 반경방향으로 퍼져나가 5개의 영역으로 분류되어 나타내게 된다. 난류 혹은 층류 분무의 경우, 충돌판에 충돌한 후 두꺼운 액막을 형성하게 되며, 이러한 상태에서 충돌하는 분무의 비산량은 매우 적으며 충돌 거리에 영향을 받지 않는다. 한편, 파동이 있는 분무의 충돌은 수력도약(Hydraulic jump)과 함께 반경방향으로 엷은 액막을 형성하게 되며 비산율도 증가하게 된다. 액체분무의 초속도가 증가하면 비산율도 증가하게 된다. 분열이 일어난 후에 충돌하는 파동 분무의 비산율은 분열이 일어나기 전에 비해 약 2~3배 정도 크게 나타난다. 비산율은 웨버수(Weber number)를 이용하여 요약할 수가 있다.

• 한국분무공학회지
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• 제9권2호
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• pp.41-49
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• 2004

Liquid breakup under the variation of AC frequency has been studied experimentally in the electrohydrodynamic atomization. The effect of parameters such as charging voltage, flow rate, nozzle tip inner diameter and power frequency have been considered. This work was performed to investigate the experimental analysis for the effect of AC frequency on breakup process, the mapping of occurrence of disintegration region, and the relationship between the applied power and the droplet radius. The experimental results show that the increase of applied voltage in a certain frequency band leads to a reduction in the droplet size within the limits from 50Hz to 400Hz. The transition phenomena from dripping mode to spindle mode were observed under the band of sudden fall of droplet radius changing ratio, and the synchronous region were produced within the range of applied voltage from 5kV to 6kV.