• The Journal of the Acoustical Society of Korea
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• 제23권2E호
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• pp.44-50
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• 2004

A theoretical formula that is based on the geometrical theory of diffraction (GTD) is proposed for computing sound diffraction by multiple wedges, barriers, and polygonal-like shapes. The formula can treat both convex and concave edges, where edges mayor may not be inter-connected. Comparisons of theoretical predictions with other results done by the BEM or experiments for scaled model confirm the accuracy of the present formula. Numerical examples such as double wedges and doubly inclined barrier show that when there exist several diffraction paths for given source and receiver positions, the insertion loss is dominated by the diffraction associated with the shortest propagation path.

• Journal of the Optical Society of Korea
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• 제14권4호
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• pp.333-336
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• 2010

The generation of coherent x-ray beams by using a multi-slit diffraction phenomenon is presented. The mode-confinement conditions in the x-ray waveguide (XWG) needed to obtain single-mode beams are determined. The XWGs are stacked to form an XWG array. The core of the XWG array is used as a slit in an opaque screen, similar to those used for visible light. Diffraction patterns that interfered constructively in the XWG array are investigated based on multi-slit diffraction theory. The irradiance distributions are studied at on observation screen. The FWHM of diffracted x-ray spectra were between $1.67{\times}10^{-4}$ to $3.30{\times}10^{-5}$ radians which lead to a spot-size of a few tens of micrometers on the screen at distance of 1 m. The intensities decrease with increase in the period of the XWG array, i.e. a thicker cladding, due to growth of the higher-order diffraction peaks.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1704-1709
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• 2000

This paper proposes a spherical probe allowing acoustic intensity measurements in three dimensions to be made, which creates a diffracted field that is well-defined, thanks to analytic solution of diffraction phenomena. Six microphones are distributed on the surface of the sphere along three rectangular axes. Its measurement technique is not based on finite difference approximation, as is the case for the ID probe but on the analytic solution of diffraction phenomena. In fact, the success of sound source identification depends on the inverse models used to estimate inverse diffraction phenomena, which has non-linear properties. In this paper, we introduce the concept of nonlinear inverse diffraction modeling using a neural network and the idea of 3 dimensional sound source identification with several tests.

• 비파괴검사학회지
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• 제36권2호
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• pp.112-120
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• 2016

The nonlinearity parameter is frequently measured as a sensitive indicator in damaged material characterization or tissue harmonic imaging. Several previous studies have employed the plane wave solution, and ignored the effects of beam diffraction when measuring the non-linearity parameter ${\beta}$. This paper presents a multi-Gaussian beam approach to explicitly derive diffraction corrections for fundamental and second harmonics under quasilinear and paraxial approximation. Their effects on the nonlinearity parameter estimation demonstrate complicated dependence of ${\beta}$ on the transmitter-receiver geometries, frequency, and propagation distance. The diffraction effects on the non-linearity parameter estimation are important even in the nearfield region. Experiments are performed to show that improved ${\beta}$ values can be obtained by considering the diffraction effects.

• 물과 미래
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• 제9권1호
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• pp.70-80
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• 1976

The efficient breakwater design requires a knowledge of the behaviour of the waves passing the breakwater. Wave Diffraction is an important factor and phenomeon in this behaviour. The diffraction ocean waves entering a gap in a breakwater normal to the incident wave direction in water of uniform depth has been investigated, applying a solution previously given in the author's paper, based on the theory of light diffraction by Sommerfeld. The wave profiles and heights on both the leeward side of the breakwater and the gap side have been studied and summarized in the form of diagrams with diffraction coefficients in range of x/L, y/L 0∼100, b/L=0.5∼12, with some extension of the diagrams made previously. The results of the theoretical approaches have not been experimentally verified. The theory ad computation methods with computer program in Fortran IV developed in this study make an efficient use for estimating the diffraction about a breakwater gap.

• Applied Microscopy
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• 제32권3호
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• pp.185-193
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• 2002

Texture electron diffraction pattern을 이용한 결정구조 해석 이론은 러시아어로 씌여졌거나, 영문판 저서의 일부에 간단히 소개 되어있어 이해에 어려움이 있다. 이들의 이론은 벡터의 이론과 관련된 여러 관계식을 이용해서 설명될 수 있으며, 이로서 몇 개의 식에 포함된 오류를 수정하였다.

• 대한전자공학회논문지
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• 제21권5호
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• pp.27-32
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• 1984

SAW필터에서 변환기의 구경 (aperture)의 크기를 작게 하면 화질의 영향이 크게 나타나게 되어 트랩(trap)부근에서 주파수 특성이 크게 손상된다. 회절의 영향을 해석할 수 있는 컴퓨터 시뮬레이션 프로그램이 작성되었으며 회절의 영향이 큰 SAW필터에 적용될 수 있는 회절보상방법이 제안되었다. 이를 TV중간주파 필터에 적용하여 실험적으로 유용성을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1428-1429
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• 2006

We investigated the diffraction efficiency, erasing property and rewriting property of diffraction grating with each wavelength of recording beam. A (P:P) polarized light was exposed on AsGeSeS and Ag/AsGeSeS thin film to form a diffraction grating by HeNe(635nm) laser and DPSS(532nm) laser. At the maximum efficiency condition, unpolarized HeNe laser beam was irradiated to erase 1ha generated diffraction grating. The HeNe laser showed more higher diffraction efficiency and the DPSS laser showed more faster diffraction grating time. At erasing and rewriting process, AsGeSeS(61%-85%)thin film showed better property than Ag doped Ag/AsGeSeS(53%-63%) double layer structured thin film.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.456-459
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• 2003

In this thesis, We observed the characteristic of the diffraction efficiency according to the wave length of the chalcogenide thin films. The used an $Ag(200{\AA})/As_{40}Ge_{10}Se_{15}S_{35}$ thin film. We made grating formation by each wave length 325nm, 442nm, 632.8nm. After measure diffraction efficiency of the time. We expressed the maxium saturation value at fast time as were the short wavelength and stable characteristic. On the other hand we appeard to the by a maxium diffraction efficiency the 1.7% in 325nm, 0.8% in 442nm, 0.27% in 632.8nm. The maximum diffraction efficiency expressed high value as were the long wavelength.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.44-49
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• 2000

Recently, PM-high speed steel(PM-HSS) has reportedly been a good alternative material for rolling mill because of its superior peformance to conventional HSS. This paper has been aimed to investigate the possibility for application to rolling contact element for PM-HSS by X-ray diffraction technique. The X-ray elastic constant for PM-HSS has been found by X-ray diffraction during the four-point bending test. Residual stress and half-value breadth on the contact surface during rolling contact fatigue process by X-ray diffraction have also been measured. The result of this study shows that the application of X-ray diffraction technique to PM-HSS could be as possible alternative material as conventional HSS. Half-value breadth on rolling contact surface by X-ray diffraction is not changed during rolling contact fatigue process. On the other hand, the residual stress is changed. This suggests that dislocation reaction has been hardly occurred in rolling contact, depending on supersaturated carbon in PM-HSS.