• 천문학회보
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• 제42권2호
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• pp.55.2-55.2
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• 2017

We present a numerical code for the random scattering histories of Lyman alpha photons in the intergalactic medium. The numerical code calculates the radiative transfer under generic three dimensional density, ionization fraction, and peculiar velocity fields based on N-body + radiation transfer simulations of the epoch of reionization. The code is tested with models having analytical solutions, which have idealized geometry and simplified velocity fields. The emergent line profiles can give constraints to the ionization structure around Lyman alpha sources in the early universe.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2270-2280
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• 2005

An experimental study is performed for turbulent swirling flow behind a circular cylinder using 2-D PIV technique. The Reynolds number investigated are 10,000, 15,000, 20,000 and 25,000. The mean velocity vector, time mean axial velocity, turbulence intensity, kinetic energy and Reynolds shear stress behind the cylinder are measured before and behind the round cylinder along the test tube. A comparison is included with non swirl flow behind a circular and square cylinder. The recirculation zones are showed asymmetric profiles.

• 오토저널
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• 제4권3호
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• pp.56-68
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• 1982

This paper presents analytic solutions of defection and their resonance diagrams for a uniform beam of infinite length subjected to an constant axial force and moving transverse load simultaneously. Steady solutions are obtained by a time-independent coordinate moving with the load. The supporting foundation includes damping effects. The influences of the axial force, the damping coefficient and the load velocity on the beam response are studied. The limiting cases of no damping and critical damping are also investigate. The profiles of the deflection of the beam are shown graphically for several values of the load speed, the axial force and damping parameters. Form the results, following conclusions have been reached. 1. The critical velocity .THETA.cr decreases as the axial compressive force increases, but increases as the axial tensile force increase. 2. At the critical velocity .THETA.cr the deflection have a tendency to decrease as the axial tensile force increases and to increase gradually as the axial compressive force increases. 3. In case if relatively small dampings, the deflection increases suddenly as the velocity of the moving load approaches the critical velocity, and it reachs its maximum at the critical velocity, and it decreases and become greatly affected by the axial force as the velocity increases further. 4. in case of relatively large dampings, as the velocity increases the deflection decreases gradually and it is affected little by the axial load.

• 환경위생공학
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• 제10권3호
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• pp.1.1-15
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• 1995

This study was performed to estimate the characteristics of the organic wastewater treatment and bed porosity with the circulation velocity in the anaerobic fluidized bed biofilm reactor. The results were as follows; 1. With Increasing circulation velocity the fluidized bed expanded smooth and with increasing initial particle volume the fluidized bed was increased. 2. With increasing circulation velocity the gasproduction was increased, but at 1.Scnt/sec of circulation velocity AFBBR showed the highest value of methane production rate per removed COD. Therefore, for the purpose of economical operation in AFBBR, 1.5cm/sec of circulation velocity was optimum 3. The microorganisms were colonized in the crevice of the media. 4. On fluidization, COD, VA,55 profiles with the reactor height were not showed. In conclusion, AFBBR suit the organic wastewater treatment's purpose, and at 1.5cm/sec of circulation velocity the system is economical in an energy Point of view.

• 동의생리병리학회지
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• 제25권3호
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• pp.551-557
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• 2011

The purpose of this study is to investigate the relation between brachial-ankle pulse wave velocity and the features of metabolic syndrome, and differences according to sex in patients diagnosed cerebral infarction. The study group comprised 61 patients over age 30 who were diagnosed cerebral infarction, accompanied with metabolic syndrome. The brachial-ankle pulse wave velocity, blood pressure, lipid profiles, fasting blood glucose, body mass index were measured. Also we checked past history of patients. Then we analyzed the association between brachial-ankle pulse wave velocity and the features of metabolic syndrome. Pearson correlation analysis reflected the variables affecting the brachial-ankle pulse wave velocity as follows : Age, SBP(systolic blood pressure), DBP(diastolic blood pressure), FBS(fasting blood glucose) were positively correlated. As a result of regression analysis, in patients with cerebral infarction accompanied with metabolic syndrome, the brachial-ankle pulse wave velocity is affected by age to men, SBP, FBS, DBP to women. The brachial-ankle pulse wave velocity is not affected by the components of metabolic syndrome, except blood pressure, FBS, in patients with ischemic stroke.

• 천문학회보
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• 제36권2호
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• pp.106.2-106.2
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• 2011

The two competing theories of star formation are based on turbulence and ambipoar diffusion. I will first briefly explain the two theories. There have been analytical (or semi-analytic) models, which estimate star formation rates in a turbulent cloud. Most of them are based on the log-normal density PDF (probability density function) of the turbulent cloud without self-gravity. I will first show that the core (star) formation rate can be increased significantly once self-gravity of a turbulence cloud is taken into account. I will then present the evolution of molecular line profiles of HCO+ and C18O toward a dense core that is forming inside a magnetized turbulent molecular cloud. Features of the profiles can be affected more significantly by coupled velocity and abundance structures in the outer region than those in the inner dense part of the core. During the evolution of the core, the asymmetry of line profiles easily changes from blue to red, and vice versa. Finally, I will introduce a method for incorporating ambipolar diffusion in the strong coupling approximation into a multidimensional magnetohydrodynamic code.

• 자원환경지질
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• 제31권3호
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• pp.235-247
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• 1998

직접파, 반사파 및 굴절파를 사용해서 3차원 속도 구조를 결정하기 위한 동시역잔 토모그래피 기술을 한반도 중부에 적용하였다. 이곳은 평남 분지, 경기 육괴, 옥천 습곡대, 태백산 습곡대, 영남 육괴, 그리고 경상 분지를 포함한다. 32개 event의 Pg, Sg, PmP, SmS, Pn과 Sn 위상들을 포함한 총 404개 지진파선이 진원 위치와 지각구조 계산을 위해서 역산되었다. 5 (위도 따라 $1^{\circ}$) ${\times}6$ (경도 따라 $0.5^{\circ}$) ${\times}8$ (매 깊이 4km 두께)의 블럭모델이 역산된다. 따라서 표면에서 Moho까지 8개 단면도, 위도 경도를 따라서 8개 측면도, 그리고 Moho갚이 등이 결정된다. 그 결과는 다음과 같다. (1) 퇴적암의 평균속도와 두께는 5.15 km/sec과 3-4 km이다. 기반의 속도는 6.12 km/sec이다. (2) 상부지각에서 속도는 매우 불규칙하나 Conrad 법의 하부지각의 속도 변화는 근본적으로 변화가 없다. (3) Moho의 평균 깊이와 속도는 29.8 km와 7.97 km/sec이다. (4) 퇴적암 깊이와 속도, 기반암 두께와 속도, 상부지각 Moho 깊이의 모양, 평남 분지, 경기 육괴, 옥천대, 영남 육괴, 경상 분지 등의 현저한 속도 변화가 발견된다. (5) 해양과 대륙 지각의 틀린 지각구조가 분명하다. (6) 추가령 지구대의 저속도 심부 대칭모양이 측면도에서 뚜렷하게 발견되었다. (7) 서울 수도권 지역북부와 홍성지역의 상부지각에서 큰 저속도 이방체가 발견되었는데, 이것은 추가령지구대 및 심부 잠복단층과 관계가 있을 수 있는 큰 속도 이방체로 볼 수 있다.

• 한국수자원학회논문집
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• 제38권10호
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• pp.841-849
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• 2005

유사 입자가 포함된 흐름이나 공기 방울이 포함된 흐름과 같은 이상류 (two-phase flow) 는 유체의 속도와 입자의 속도와 같은 두 가지 서로 다른 속도 분포가 존재한다. 이러한 이상류의 속도장 분석을 위해서는 두 가지 속도 분포를 별도로 측정할 수 있는 기법을 이용해야 한다. 공기 방울이 포함된 흐름에 대해서는 입자영상 유속계(PIV)나 입자추적유속계(PTV)를 이용하여 비교적 타당한 정도로 유속 분포를 측정하여 왔다. 그러나 자연 모래를 포함한 흐름 영상의 속도 분포 해석에서는 PIV나 PTV가 그다지 성공적이지 못했는데, 그것은 흐름 중에 있는 유사 입자가 영상을 해석하기 어렵게 만들기 때문이다. 유사 흐름의 속도 분석을 위해 다양한 영상 분석 기법을 결합한 방법을 제시하였다. 입자 추출 알고리듬으로 역치값, 경계 추출 알고리듬, 세선화 알고리듬을 조합한 새로운 방법을 제안하였다. 또한 입자의 이동 변위 계산을 위해서 PIV와 PTV를 조합한 새로운 방법을 개발하였다. 이 새로운 알고리듬은 다음과 같은 기능을 가지고 있다. (1) 새알고리듬은 유사 입자, 특히 자연 모래와 같이 불규칙한 형태를 갖는 입자의 경계를 정확히 찾아낼 수 있다. (2) 필요한 정보를 잃어버리지 않고, 반사광이나 난반사에 의한 영상을 효율적으로 제거할 수 있다. (3) 추적 입자가 유사입자 가까이에 있어 유사의 난반사 영역이 들어 있어도 이를 분리해 낼 수 있다.

• Journal of Nuclear Fuel Cycle and Waste Technology
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• 제1권1호
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• pp.49-55
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• 2013

To characterize quantitatively the transport of $^{99}Tc$ and the global fallout ($^{137}Cs$, $^{90}Sr$, and $^{239+240}Pu$) for soils in Korea, the transport parameters of a convective-dispersion model, apparent migration velocity, and apparent dispersion coefficient were estimated from the vertical depth profiles of the radionuclides in soils. The vertical profiles of $^{99}Tc$ were measured from a pot experiment for paddy soil that had been sampled from a rice-field around the Gyeongju radioactive waste repository in Korea, and the vertical depth distributions of the global fallout $^{137}Cs$, $^{90}Sr$, and $^{239+240}Pu$ were measured from the soil samples that were taken from local areas in Korea. The front edge of the $^{99}Tc$ profiles reached a depth of about 12 cm in 138 days, indicating a faster movement than the fallout radionuclides. A weak adsorption of $^{99}Tc$ on the soil particles by the formation of Tc(VII) and a high water infiltration velocity seemed to have controlled the migration of $^{99}Tc$. The apparent migration velocity and dispersion coefficient of $^{99}Tc$ for the disturbed paddy soil were 2.88 cm/y and 6.3 $cm^2/y$, respectively. The majority of the global fallout $^{137}Cs$, $^{90}Sr$, and $^{239+240}Pu$ were found in the top 20 cm of the soils even after a transport of about 30 years. The transport parameters for the global fallout radionuclides were 0.01-0.1cm/y ($^{137}Cs$), 0.09-0.13cm/y ($^{90}Sr$), and 0.09-0.18cm/y ($^{239+240}Pu$) for the apparent migration velocity: 0.21-1.09 $cm^2/y$ ($^{137}Cs$), 0.12-0.7$cm^2/y$ ($^{90}Sr$), and 0.09-0.36$cm^2/y$ ($^{239+240}Pu$) for the apparent dispersion coefficient.

• 대한기계학회논문집B
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• 제22권6호
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• pp.874-887
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• 1998

A 2-frame PTV (particle tracking velocimetry) system using the concept of match probability between two consequent image frames has been developed to obtain instantaneous velocity fields. The overall 2-frame PTV system including image pre-processing, tracking algorithm and post-processing routine was implemented to apply to real flows. The developed 2-frame PTV system has several advantages such as high recovery ratio of velocity vectors, low error ratio and small computational time compared with the conventional 4-frame PTV and the FFT-based cross-correlation PIV technique. The 2-frame PTV system was applied to a turbulent channel flow over a rectangular block to check its reliability and usefulness. Total 96 sequential image frames have been captured and processed to get both mean and fluctuating velocity vector fields over the recirculating region. The mean velocity and turbulent intensity profiles were well agreed with hte LDV measurements in the separated region behind the block. Time-averaged reattachment length is about 6.3 times of the block height.