• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.4 no.4
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• pp.43-51
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• 1990

레이저 비임이 대기중을 전파할 때 고류(turbulence)의 영향을 고려해야 한다. 고류의 영향에 의한 프린지 시도는 extended Huygens-Fresnel principle을 도입하여 타원체로 간주할 수 있는 프린지 체적에서 장의 전 분포를 시하고 이 전 분포로부터 평균 강도분포를 얻었으며, 평균 강도분포를 구하기 위해 Fourier-Bessel적분을 행하였다. 평균 강도분포에서 최대 평균 강도분포max 및 최소 평균 강도분포 min을 얻었으며, 이 식들을 프린지 시도의 정의 식 V=(Imax-Imax)/(Imax+Imin)에 적용하였다. 본 논문에서는 광원으로 파장 =4880[]인 아르곤 레이저를 사용하였고 광원의 모우드는 TEM..모우드로 하였다. 또한 비임의 교각 =5˚, 광원으로부터 프린지 체적 까지의 거리 L=10[m], en 광원간의 거리 B=(2tan /2)L, 특성 비임 반경 =2 /[ ( /2)]을 이용하여 프린지 시도에 관한 결과를 얻었으며, 이 결과에 의하면 L'( / ·L)에 대한 변수 r의 비 r/L'= 에서 V=1이고, r/L=0.1에서 프린지 시도가 감소한다. 또 강 고 류인 경우와 약 고 류인 경우에 대해 프린지 시도를 비교하였을 때 강 고류에서 감소폭이 크다는 사실을 알 수 있었다.

• Current Optics and Photonics
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• v.1 no.4
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• pp.271-277
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• 2017

Based on the extended Huygens-Fresnel principle, the analytical propagation formulae for spectrally partially coherent Gaussian Schell-model pulsed (SPGSMP) beams propagating in turbulent atmosphere have been derived. The influences of the parameters for turbulent atmosphere and SPGSMP beams on the on-axis and off-axis spectral shift and degree of coherence for SPGSMP beams propagating in turbulent atmosphere have been analyzed, using numerical calculations. The obtained results have potential applications for SPGSMP beams in free-space optical communication and laser lidar.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1986.04a
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• pp.184-188
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• 1986

The gain variations of paraboloid reflector antenna with an axially and perpendicularly defocused feed are investigated using the Huygens-Fresnel Principle. The theoretical calculations and the experimental for the reflector antenna with an axially defocused feed are compared. Although there were about 3dB difference between two results in a range from focal point to 2.0 wave-length, we could know that it was property approached to theoretical results. However, when the magnitude of defocusing is increased, the differences are also increased because of the influence by a weak received signal and interference of external noises. In addition, it can be shown that gain variations are acutely decreased more in perpendicular defocusing than in axial defocusing in the paraboloid reflector antenna.

• Current Optics and Photonics
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• v.3 no.2
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• pp.97-104
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• 2019

Based on the extended Huygens-Fresnel principle, the analytical equation for a Lorentz-Gauss vortex beam propagating through oceanic turbulence has been derived. The spreading properties of a Lorentz-Gauss vortex beam propagating through oceanic turbulence are analyzed in detail using numerical examples. The results show that a Lorentz-Gauss vortex beam propagating through stronger oceanic turbulence will spread more rapidly, and the Lorentz-Gauss vortex beam with higher topological charge M will lose its initial dark center more slowly.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.972-981
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• 2000

The phased array transducer has two distinct advantages. One is rapid scanning comparing with the conventional mechanical or manual scanning system. Therefore, output image is represented in real-time. The other is the dynamic focusing and the dynamic steering of ultrasonic beam. Only the delay times that are controlled electrically are used to focus and to steer beam without any lenses or wedges. In this study, the profile of the ultrasonic beam for the phased array transducer has been simulated in the Huygens principle with varying the inter-element spacing of the linear phased array transducer. From the result of this study, it was found that the ultrasonic beam spread wider as the inter-element spacing was decreased. However, the focusing effect was improved, even when the number of the element was not big. In addition, there was grating lobes that are constructed when the inter-element spacing is more than half wavelength. However, this grating lobe has lower amplitude than the main lobe.

• Explosives and Blasting
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• v.17 no.2
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• pp.36-44
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• 1999

A study was made on the design of the prediction model concerning blasting vibration in a constraction site, Namgu, Daegu City. The geology in this area consists of hornfels of shale and mud underlain by quartize, of which the main strike of the geological structure is NW direction. Measurements were carried out on the top of the wall concrete water storage tank, which is burried in the ground earth. The attenuation due to the vertical wall of the concrete structure may be experted because of spherical divergency at the bottom corner of the wall by the Huygens principle. For design of blasting prediction model, thus among scaled distance(SD) may be preferable to use in the regression model, since they represents most likely the average ground condition. Judging from the regression results, the cube root method may be more suitable for this area. The SD values for the maximum allowable vibration velocity of 0.5 cm/s, in this area are 22.5, 28.0 and 30.6 for the significance level of 50%, 95% and 99%, respectively.