• 분석과학
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• 제18권4호
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• pp.263-270
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• 2005

핵분열트랙은 우라늄, 플루토늄, 토륨 등의 방사성핵종 분석이나, 리튬이나 붕소와 같이 열중성자와 핵반응을 하는 원소분석에 매우 유용하다. 이 방법은 대기 중의 방사성핵종 분석을 통해 핵무기 실험을 검출한다거나, 우주공간의 중이온에 대한 선량측정이나 운석의 우주선 조사과정 추정, 원자력분야의 핵분열률 측정, 암석의 연대 및 역사를 파악하거나, tracer로 사용하는 등 여러 분야에 적용 가능하다. 현재 원자력연구소에서는 알파트랙기입법을 이용한 미량의 보론 분석이나, 핵분열트랙을 이용한 우라늄 등의 핵물질을 포함한 입자분석에 적용하고 있다. 본 총설에서는 트랙형성의 이론적 배경, 에칭된 트랙을 얻는 실제 과정 및 앞으로의 전망 등에 대해 살펴보았다.

• 한국수자원학회논문집
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• 제54권5호
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• pp.335-345
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• 2021

하천에서의 용존물질의 혼합거동을 신속하게 예측하기 해석하기 위하여 1차원 추적모형이 개발되어 왔다. 그 중 저장대모형(Transient Storage Model, TSM)은 자연하천의 복잡하고 불규칙한 수리·지형적인 특성을 단순하게 반영할 수 있다는 장점때문에 가장 많이 사용되는 1차원 추적모형이다. 하지만 TSM의 정확도는 본류대 및 저장대의 면적, 물질교환계수 등 모형의 매개변수에 의존하며 이들은 직접적으로 측정될 수 없다는 단점이 있다. 또한 TSM은 농도곡선의 꼬리에 나타나는 저장대특성의 형태를 지수함수형태로 반영하는데 이는 실제 추적자실험을 통해 관측되는 꼬리는 형태와 다르다는 평가가 제기되고 있다. 이에 따라 본 연구에서는 1차원 확률론적 저장대모형에 대한 수치모형을 개발하여 자연하천에 적용하고 그 결과를 TSM의 모의결과와 비교하였다. 상기의 모형을 검증하기 위하여 낙동강의 1차 지류 중 하나인 감천의 4.85 km의 구간에서 추적자 실험을 실시하였다. 본 추적자 실험을 통해 측정한 농도곡선과 본 연구에서 제시된 확률론적 저장대모형의 모의 곡선의 꼬리부 멱함수 기울기를 비교해본 결과, 오차율은 평균 0.24으로 나타났는데, 이는 1차원 이송-분산 모형과 TSM로부터의 오차율인 14.03과 1.87에 비해 보다 정확한 값이다. 본 연구 결과, 감천에서의 저장대 특성을 나타내는 하상의 체류시간분포는 지수함수분포보다는 멱함수 분포에 가까운 것으로 밝혀졌다.

• Nuclear Engineering and Technology
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• 제4권3호
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• pp.229-240
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• 1972

Radioisotopes and their related techniques have recently been applied for scientific conservation works of cultural property and resulted many excellent findings or conservation data which could never be achieved by means of other techniques. Radiocarbon dating have widely been applied for dating the antique of organic origin, whereas the determination of radioactive contents in metal, ceramics, environmental soil, and classical objects could be able to afford many useful informations on the age, genuiness, and archeological significances as it had been produced. Trace quantity of contents of each antique have successfully been analyzed by means of radioactivation analysis or radio active tracer techniques, which could afford important technical data and results for tile conservation of each object. Radiography have also been applied for detecting the internal defects of metal objects and furthermore $\beta$-and ${\gamma}$-ray radiography were proved to be effective for such thin material as textile, painting, and fibres. In this article the detailed principle and procedures of each technique were presented so that the society could be able to make efforts to familiarize all concerns with these modern trends of the conservation techniques of cultural property.

• Nuclear Engineering and Technology
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• 제32권4호
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• pp.299-308
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• 2000

A safety assessment of reactor vessel lower head integrity under in-vessel vapor explosion loads has been performed. The core melt relocation parameters were chosen within the ranges of physically realizable bounds. The premixing and explosion calculations were performed using TRACER-II code. Using the calculated explosion pressures imposed on the lower head inner wall, strain calculations were peformed using ANSYS code. Then, the calculated strain results and the established failure criteria were used in determining the failure probability of the lower head, In the explosion analyses, it is shown that the explosion impulses are not altered significantly by the uncertain parameters of triggering location and time, fuel and vapor volume fractions in uniform premixture bounding calculations. Strain analyses show that the vapor explosion-induced lower head failure is not possible under the present framework of assessment. The result of static analysis using the conservative explosion-end pressure of 50 MPa also supports the conclusion. It is recommended, however, that an assessment of fracture mechanics for preexisting cracks be also considered to obtain a more concrete conclusion.

• Journal of Advanced Marine Engineering and Technology
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• 제27권3호
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• pp.395-404
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• 2003

Quantitative data of the temperature and velocity were obtained simultaneously by using liquid crystal tracer. PIV(Particle Image Velocimety) based on a grey-level cross-correlation method was used for visualizing and analysis of the flow field. The temperature gradient was obtained by applying the color-image processing to a visualized image, and a neural-network a1gorithm was applied to the color-to-temperature calibration. This simultaneous measurement was applied to the Rayleigh-Bernard convection. This paper describes the method, and presents the quantitative visualization of Rayleigh-Bernard convection and the effect of aspect ratio and viscosity. Also the experimental results were compared with the numerical results.

• Journal of Advanced Marine Engineering and Technology
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• 제33권5호
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• pp.679-685
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• 2009

In order to simulate a smoke or poisonous gas emergency in a rectangular tunnel and to investigate a better way to exhaust the smoke, the characteristics of smoke flow have been analyzed using flow field data acquired by Particle Image Velocimetry(PIV). Olive oil has been used as tracer particles with the kinematic viscosity of air, $1.51{\times}10^{-5}\;m^2/s$. The investigation has done in the range of Reynolds number of 1600 to 5333 due to the inlet velocities of 0.3 m/s to 1 m/s respectively. The average velocity vector and instantaneous kinematic energy fields with respect to the three different Reynolds numbers are comparatively discussed by the Flow Manager. In general, the smoke flow becomes more disorderly and turbulent with the increase of Reynolds number. Kinematic energy in the measured region increases with the increase of Reynolds number while decreasing at the leeward direction about the outlet region.

• 한국통신학회논문지
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• 제8권1호
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• pp.38-42
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• 1983

1개의 터널 다이오우드(TD)의 稱特性을 커어브 트레서로부터 2개의 指數項을 합으로 나타내어 電子計算機에 의해 TC對特性을 플롯한 결과 理論値의 2%이내의 오차로 近似시킬 수 있었다. 이와 같이 구한 對特性을 이용하여 MV(멀티바이브레이터)트리거作動을 形式的으로 잘 說明할 수 있었으며 安定特性을 區間直線法에 의해서 解析한 結果는 實驗値와 잘 일치함을 알았다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.893-900
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• 1994

In this study, workspace analysis has been performed for a Clemens Coupling type parallel robotic wrist with four degrees of freedom such as three angular degrees of freedom and 1 plunge motion. Because of plunge motion, this mechanism has no singular point that the general roll-pitch-roll mechanisms have. Also, proposed mechanism performs larger load, faster motion, with less weight and has better structural characteristics such as higher stiffness and strength to weight ratio compared with serial type mechanisms. As a basic step for position control, the closed form solution of forward and inverse kinematics are proposed and workspace is analyzed and plotted by applying triangle tracer method for workspace boundary tracing.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 Proceedings of 2004 Korea-Japan Joint Seminar on Particle Image Velocimetry
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• pp.91-110
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• 2004

A comprehensive three-dimensional nano-particle tracking technique in micro- and nano-scale spatial resolution using the Total Internal Reflection Fluorescence Microscope (TIRFM) is discussed. Evanescent waves from the total internal reflection of a 488nm argon-ion laser are used to measure the hindered Brownian diffusion within few hundred nanometers of a glass-water interface. 200-nm fluorescence-coated polystyrene spheres are used as tracers to achieve three-dimensional tracking within the near-wall penetration depth. A novel ratiometric imaging technique coupled with a neural network model is used to tag and track the tracer particles. This technique allows for the determination of the relative depth wise locations of the particles. This analysis, to our knowledge is the first such three-dimensional ratiometric nano-particle tracking velocimetry technique to be applied for measuring Brownian diffusion close to the wall.

• 대한기계학회논문집B
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• 제33권1호
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• pp.1-8
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• 2009

Recently microscale biofluid flows have been receiving large attention in various research areas. However, most conventional imaging techniques are unsatisfactory due to difficulties encountered in the visualization of microscale biological flows. Recent advances in optics and digital image processing techniques have made it possible to develop several advanced micro-PIV/PTV techniques. They can be used to get quantitative velocity field information of various biofluid flows from visualized images of tracer particles. In this paper, as new advanced micro-PIV techniques suitable for biofluid flow analysis, the basic principle and typical applications of the time-resolved micro-PIV and X-ray micro-PIV methods are explained. As a 3D velocity field measurement technique for measuring microscale flows, holographic micro-PTV method is introduced. These advanced PIV/PTV techniques can be used to reveal the basic physics of various microscale biological flows and will play an important role in visualizing veiled biofluid flow phenomena, for which conventional methods have many difficulties to analyze.