• Current Optics and Photonics
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• 제1권4호
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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.

• 한국통신학회:학술대회논문집
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• 한국통신학회 1986년도 춘계학술발표회 논문집
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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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• 제3권2호
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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.

• 대한전자공학회논문지
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• 제23권3호
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• pp.397-400
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• 1986

In this paper, the orthogonal properties of the eigenmodes of optical resonators which have phase conjugate mirrors at both ends are derived. The modes which propagate in resonators are descdribed by the Huygens integral. Then, the eigeneuqation which is needed in order to prove the orthogonality of the eigenmodes of the resonator is obtained from this representation. When the kernel being a part of the eigenequation is Hermitian as in conventional resonators and in optical resonator with only one phase conjugate mirror, one can show that the eigenmodes have essentially biorthogonal relations, which are satisfied the set of modes propagating in one direcdtion around the resonator and the adjoint set of modes propagating in the reversed direction.

• 천문학회지
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• 제41권3호
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• pp.65-76
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• 2008

We have investigated the optical properties of the global haze on Titan from spectra recorded between 7100 and $9200{\AA}$, where $CH_4$ absorption bands of various intensities occur. The Titan spectra were obtained on Feb. 23, 2005 (UT), near the times of the Cassini T3 flyby and Huygens probe, using an optical echelle spectrograph (BOES) on the 1.8-m telescope at Bohyunsan Observatory in Korea. In order to derive the optical properties of the haze as a function of altitude, we developed an inversion radiative-transfer program using an atmospheric model of Titan and laboratory $CH_4$ absorption coefficients available from the literature. The derived extinction coefficients of the haze increase toward the surface, and the coefficients at shorter wavelengths are greater than those at longer wavelengths for the 30 - 120 km altitude range, indicating that the Titanian haze becomes optically thin toward the longer wavelength range. Total optical depths of the haze are estimated to be 1.4 and 1.2 for the 7270 - $7360{\AA}$ and 8940 - $9150{\AA}$ ranges, respectively. Based on the Huygens/DISR data set, Tomasko et al. (2005) reported total optical depths of 2.5 - 3.5 at $8290{\AA}$, depending on the assumed fractal aggregate particle model. The total optical depths based on our results are smaller than those of Tomasko et al., but they partially overlap with their results if we consider a large uncertainty from possible variations of the $CH_4$ mixing ratio over Titan's disk. We also derived the single scattering albedo of the haze particles as a function of altitude: it is less than 0.5 at altitudes higher than ${\sim}150\;km$, and approaches 1.0 toward the surface. This behavior suggests that, at altitudes above ${\sim}150\;km$, the average particle radius is smaller than the wavelengths, whereas near the surface, it becomes comparable or greater.

• 한국과학교육학회지
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• 제26권3호
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• pp.317-329
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• 2006

이 연구에서는 고등학교 학생들의 물체의 운동에 대한 과학사적 관점을 알아보기 위한 설문지를 개발하였다. 연구 대상으로는 고등학교 1학년 학생 75명과 고등학교 2학년 학생 65명을 선정하였다. 연구 결과, 정지한 물체와 등속 운동하는 물체에 작용하는힘, 낙하 물체의 에너지 보존에 대한 고등학교 1학년 학생들의 사고는 중세의 임페투스 관점과 유사한 비율이 가장 높았으며, 고등학교 2학년 학생들은 중세의 관점과 뉴턴의 관점을 가지는 비율이 가장 높았다. 따라서 학년이 높아지면, 과학사적으로 볼 때 보다 발달한 개념을 형성하게 됨을 알 수 있었다. 외부에 힘이 작용하지 않을 때, 진공에서, 그리고 무중력 상태의 공기 중에서 물체의 운동에 대한 사고는 과학사적으로 발달된 개념 형성 비율이 I, 2 학년 모두 높았으나, 그보다 이전 시대의 사고를 가지는 경우도 상당히 있었다. 또한 물체의 포물선 운동과 원운동, 운동량 보존에 대한 사고는 뉴턴 이전 단계인 갈릴레이나 호이겐스, 데카르트 등의 사고에 머무른 경우의 비율이 고등학교 1, 2학년에서 모두 가장 높았다. 이러한 결과를 토대로, 과학사적으로 발달하기 전 단계의 사고를 하는 학생들에게 물체의 운동에 대한 적절한 인지 갈등을 유발할 수 있는 단계를 제공함으로써 교육의 효율성을 높일 수 있는 방안을 찾을 수 있을 것이다.

• 대한기계학회논문집A
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• 제24권4호
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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.

• Communications for Statistical Applications and Methods
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• 제18권5호
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• pp.559-570
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• 2011

1650년대에 파스칼과 페르마가 주고 받은 편지에서 시작된 확률 연구가 하위헌스, 베르누이, 라플라스 등의 연구로 이어지는 과정에서 당시의 법률적인 사고가 어떤 역할을 하였는지 살펴보았다. 이 연구에서 살펴 본 바에 따르면 초기 확률 연구에서 '기댓값'과 '확률'이라는 새로운 용어와 개념이 생기는 데에는 '공정한 거래', '확실성의 정도'와 같은 법률적인 사고가 큰 역할을 하였던 한편, 19세기 이후 센서스를 비롯한 통계조사가 활발해지면서 거꾸로 통계가 사회적, 법률적 사고방식에 영향을 미치기도 하였다.

• 한국간담췌외과학회지
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• 제28권1호
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• pp.109-113
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• 2024

Cholangiocarcinoma is a heterogeneous group of aggressive tumors that correspond to the second most common primary liver tumor. They can be classified according to their anatomical position concerning the biliary tree, and each subtype demonstrates different behavior and treatment. A 38-year-old male patient presenting solely right lumbar pain was diagnosed with a 7 cm hepatic tumor involving segments I, Iva, and VIII associated with involvement of the hepatic veins. He underwent a bloc resection of hepatic segments I, II, III, IV, partial V, partial VII, and VIII; right, middle, and left hepatic veins; and inferior vena cava segment, with perfusion of the remaining liver in situ with a preservation solution. As the patient had a large accessory inferior right hepatic vein draining the remaining liver, no reimplantation of hepatic veins was necessary. He remained clinically stable in outpatient follow-up, with excellent performance status-current survival of 2 years 6 months after surgical treatment.

• 화약ㆍ발파
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• 제17권2호
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• pp.36-44
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• 1999

도심지 건물 부지조성공사를 위한 발파예측식에 대한 사례연구를 수행하였다. 대상지역은 대구광역시 남구 대명동 산 201-4 일대로써 지질은 상부에 세일 이암이 호온펠스화한 치밀한 암석과 그 하부는 규장암을 기반으로 하고 있으며 지질구조는 주요 주향방향은 NW방향이고 부축방향은 EW이다. 진동 측정은 지상고 6m 높이의 상수용 수조콘크리트 구조물 상부에서 측정되었으며, 이때 구조물에 의한 파의 감쇄현상이 상당히 큼으로서 경제적인 발파설계를 위하여는 환산거리가 큰 직선상의 속도분석에 의한 설계가 유효할 것이며, 경제적인 발파설계를 위하여는 환산가리가 큰 직선상에 의한 설계가 유효할 것이며, 또한 거리계수를 고려하면 삼승근의 경우가 자승근의 경우보다 더 낮다고 생각되며 이때 안전발파를 위나 최대허용속도 0.5cm/s에 대한 50%, 95%, 99%의 유의수준에서의 환산거리는 각각 22.5, 28.0 및 30.6이었다.