• 한국항공우주학회지
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• 제47권8호
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• pp.599-606
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• 2019

펄스건 장치는 연소실 내, 다중 분사기 배열에 따른 연소 유동장으로의 횡단 압력파 전파/감쇠 메커니즘 규명을 목적으로 제작되었다. 제작된 펄스건은 성능시험을 통해 목표 연소압에서의 운용 가능 여부와 압력파 강도 제어 여부를 확인하였다. 기체질소를 사용하여 고압관에 가압을 하였으며 다이아프램에는 $100{\mu}m$ 두께의 OHP 필름을 사용하였다. 압력파의 속도와 강도를 확인하기 위해 압력 트랜스듀서를 이용하여 동압과 정압을 측정하였다. 제작된 펄스건은 공급압력에 따라 압력파의 강도 조절이 가능하며 횡방향성을 가지는 압력파를 생성할 수 있음을 성능시험을 통해 확인하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.364-365
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• 2006

Transverse some wave was generated by T type waveguide for single wafer cleaning application T type megasonic waveguide was analyzed by acoustic pressure measurements and particle removal efficiency. Compared to conventional longitudinal waves, not like longitudinal waves, transverse waves showed changes of direction and phase which increased the cleaning efficiency.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.343-346
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• 2005

전산 해석과 병렬처리를 이용하여 정사각 관 내부를 전파하는 데토네이션파의 삼차원 구조를 살펴보았다. 가변 비열비 공식과 간략화 된 일단계 Arrhenius 반응 모델과 연계된 비점성 유체 방정식을 MUSCL 기반 TVD 해법과 4단계 Runge-Kutta 적분 방법을 이용하여 해석하였다. 삼차원에서의 비정상 해석 결과로부터 그을음 막 기록(smoked-foil record)에서 같은 길이와 다른 폭을 가지는 수평 및 대각 방향 불안정에 의한 상세한 파면 구조를 파악할 수 있었다.

• 한국통신학회논문지
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• 제11권6호
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• pp.371-378
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• 1986

정현적으로 진동하는 유전체 경계면에서 전자파(TM파)의 반사, 투과현상을 진동하는 임의의 순간에 등속운동이라 가정하여 Lorentz 변환을 확대적용하여 이론적으로 해석하였다. 전자파의 입사각, 운동매질의 유전율, 진동속도의 함수로써 반사, 투과특성을 수치계산 검토하였다.

• Geomechanics and Engineering
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• 제18권6호
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• pp.605-614
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• 2019

The present paper seeks to investigate propagation and reflection of waves at free surfaces of homogeneous, anisotropic and rotating micropolar fibre-reinforced medium with voids. It has been observed that, in particular when P-wave is incident on the free surface, there exist four coupled reflected plane waves traveling in the medium; quasi-longitudinal displacement (qLD) wave, quasi-transverse displacement (qTD) wave, quasi-transverse microrotational wave and a wave due to voids. Normal mode Analysis usually called harmonic solution method is adopted in concomitant with Snell's laws and appropriate boundary conditions in determination of solution to the micropolar fibre reinforced modelled problem. Amplitude ratios which correspond to reflected waves in vertical and horizontal components are presented analytically. Also, the Reflection Coefficients are presented using numerical simulated results in graphical form for a particular chosen material by the help of Mathematica software. We observed that the micropolar fibre-reinforced, voids and rotational parameters have various degrees of effects to the modulation, propagation and reflection of waves in the medium. The study would have impact to micropolar fibre-reinforecd rotational-acoustic machination fields and future works about behavior of seismic waves.

• 한국전자파학회논문지
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• 제11권8호
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• pp.1297-1304
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• 2000

본 논문에서는 마이크로 스트립의 불연속의 해석시 full-wave FDTD 해석방법이 가지고 있는 긴 계산시간과 많은 양의 메모리를 수직성분 계산방법으로 해석함으로서 줄일 수 있음을 보였다. 이를 확인하기 위하여 마이크로 스트립구조를 갖는 저역통과 필터, 패치안테나, branch-line coupler에 적용하고, 그 특성을 해석하였으며, 이를 기존의 full-wave 방법과 계산시간, 메모리 양을 비교하였다. 그 결과, 본 논문에서 제안된 방법은 기존의 방법에 비하여 계산시간과 메모리 양이 각각 약 50%, 33%가 감소됨을 확인할 수 있었다. 이 방법을 통하여 기존의 FDTD에 비하여 좀더 빠르면서, 적은 양의 메모리가 사용되는 해석이 가능하다.

• Journal of the Optical Society of Korea
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• 제3권1호
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• pp.15-19
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• 1999

The formation of spontaneous transverse optical patterns was investigated in a single feedback mirror system using nematic liquid crystals as nonlinear optical media. By varying the size of an input beam and the feedback distance, we obtained various interesting transverse optical patterns as well as the hexagonal pattern which are predicted theoretically assuming plane wave input. We can explain theoretically these characteristics of various pattern by introducing a ratio of the beam half width and spatial wavelength of the patterns. We have observed that as this ratio increased, the number of spot constituting the patterns also increased. Finally the patte군 evolved into the sucessive hexagon in the transverse plane.

• The Journal of the Acoustical Society of Korea
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• 제25권2E호
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• pp.60-68
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• 2006

High-frequency bistatic scattering measurements from a corrugated surface were made in an acoustic water tank. First the azimuthal scattering pattern was measured from an artificially corrugated surface which has varying impedance. The corrugated surface was installed both transverse to the direction of incident wave and longitudinal to the direction of incident wave. The angle between the corrugated surface and the direction of the incident wave was about $45^{\circ}$. Second, the scattering strengths were measured from the flat sediment and the corrugated sediment. A critical angle of about $37^{\circ}$ was calculated in the acoustic water tank. The measurements were made at three fixed grazing angles: $33^{\circ}$ (lower than critical angle), $37^{\circ}$ (critical angle), and $41^{\circ}$ (higher than critical angle). The scattering angle and the grazing angle are equal in each measurement. Frequencies were from 50 kHz to 100 kHz with an increment of 1 kHz. The corrugated sediment was made transverse to the direction of the incident wave. The first measurement indicates that the scattering patterns depend on the relations between the corrugated surface and the direction of the incident wave. In the second measurement, the data measured from the flat sediment were compared to the APL-UW model and to the NRL model. The NRL model's output shows more favorable comparisons than the APL-UW model. In case of the corrugated sediment, the model and the measured data are different because the models used an isotropic wave spectrum of sediment roughness in the scattering calculations. The isotropic wave spectrum consists of $w_2$ and ${\gamma}_2$. These constants derived from sediment names or bulk size. The model which used the constants didn't consider the effect of a corrugated surface. In order to consider a corrugated surface, the constants were varied in the APL-UW model.

• Steel and Composite Structures
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• 제32권2호
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• pp.213-223
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• 2019

For the first time, longitudinal and transverse wave propagation of triclinic nanobeam is investigated via a size-dependent shear deformation theory including stretching effect. Furthermore, the influence of initial stress is studied. To consider the size-dependent effects, the nonlocal strain gradient theory is used in which two small scale parameters predict the behavior of wave propagation more accurately. The Hamiltonian principle is adopted to obtain the governing equations of wave motion, then an analytic technique is applied to solve the problem. It is demonstrated that the wave characteristics of the nanobeam rely on the wave number, nonlocal parameter, strain gradient parameter, initial stress, and elastic foundation. From this paper, it is concluded that the results of wave dispersion in isotropic and anisotropic nanobeams are almost the same in the presented case study. So, in this case, triclinic nanobeam can be approximated with isotropic model.

• Korean Journal of Hydrosciences
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• 제4권
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• pp.81-92
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• 1993

This paper presents a model on the migration characteristics which is developed by using the equations for conservation of mass, momentum, and for lateral stability of the streambed. This model enables prediction of the magnitude the location of near-bank bed scour as well as rates and direction of meander migration in the sine-wave type revers (SWR) of small sinuosity. It is evident from this study that the transverse bed slope factor B' and transverse mass flux factor play significant roles in predicting migration characteristics, and their values of B'=4.0 and $\alpha$= 0.4 seem reasonable. This model will produce a useful quidelines in planning, design, construction, and development of SWR basin projects.