• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(5)
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• pp.135-138
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• 2001

This paper presents micro step driving method using VHDL(Very high speed integrated circuit Hardware Description Language) which can configure CPLD(Complex Programmable Logic Device). Using VHDL which can do abstractive programming is similar to high level language. The whole block divided into five parts with freq. divide part, saw-tooth wave generation part, sine-cosine wave generation part, comparative part, out part. In the result of this study, peripheral circuits are to be simple and using LPM(Library of Parameterized Modules) is more easily to configure circuit. It is easy to verify and implement by using VHDL. To subdivide one natural step, we confirm that using micro step driver is expected that the rotor motion is stepless very smooth.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 Proceedings of 2004 Korea-Japan Joint Seminar on Particle Image Velocimetry
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• pp.111-118
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• 2004

A new micro-resolution PIV (Particle Image. Velocimetry) has been developed. To investigate transient phenomena in a microfluidic device, Dynamic micro-PIV system was realized by combining a high-speed camera and a CW(Continuous Wave) laser. The technique was applied to a micro-counter-current flow, consisting of water and butyl acetate. The velocity fields of water in the micro counter-current flow were visualized for a time resolution of 500 $\{mu}s$ and a spatial resolution of 2.2 x 2.2 $\{mu}m$. Using the Dynamic micro-PIV technique, the vortex-like motions of fluorescent particles at the water-butyl acetate interface were captured clearly

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2002년도 추계학술대회 논문집
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• pp.31-34
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• 2002

Imaging techniques using x-ray beam at high energies (>6KeV) such as contact radiography, projection microscopy, and tomography have been used to nondestructively discern internal structure of objects in material science, biology, and medicine. This paper introduces the x-ray micro-imaging method using 1B2 micro-probe line of PAL (Pohang Accelerator Laboratory). Cross-sectional information on low electron density materials can be obtained by probing a sample with coherent synchrotron x-ray beam in an in-line holography setup. Living organism such as plants, insects are practically transparent to high energy x-rays and create phase shift images of x-ray wave front. X-ray micro-images of micro-bubbles of $20\~120\;{\mu}m$ diameter in an opaque tube were recorded. Clear phase contrast images were obtained at Interfaces between bubbles and surrounding liquid due to different decrements of refractive index.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.309-317
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• 2012

Recent years have witnessed the use of micro shock tube in various engineering applications like micro combustion, micro propulsion, particle delivery systems etc. The flow characteristics occurring in the micro shock tube shows a considerable deviation from that of well established conventional macro shock tube due to very low Reynolds number and high Knudsen number effects. Also the diaphragm rupture process, which is considered to be instantaneous process in many of the conventional shock tubes, will be crucial for micro shock tubes in determining the near diaphragm flow field and shock formation. In the present study, an axi-symmetric CFD method has been applied to simulate the micro shock tube, with Maxwell's slip velocity and temperature jump boundary conditions. The effects of finite diaphragm rupture process on the flow field and the shock formation was investigated, in detail. The results show that the shock strength attenuates rapidly as it propagates through micro shock tubes.

• 대한토목학회논문집
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• 제35권1호
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• pp.141-152
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• 2015

본 연구의 목적은 국내 사력댐에서 상시적으로 얻어지는 미소지진 계측기록을 적극 활용하여 댐 사력재료의 전단파속도를 산정하고 산정방법의 실효성을 확인하는 것이다. 이를 위하여 현재 운영 중인 횡성댐과 소양강댐에서 계측된 미소지진기록 분석으로부터 얻어진 각 댐의 고유주기와 댐 기초부에서 계측된 가속도 시간이력을 입력하중으로 한 반복적인 동적수치해석을 수행하여 계산한 고유주기 사이의 적합조건을 만족시키는 방법으로, 사력존의 심도별 전단파속도를 산정하였다. 이러한 방법으로 산정된 전단파속도는 동일댐에 대하여 다른 지진 기록을 이용하더라도 일관된 결과를 보여줌을 확인하였고, 현장탐사 결과와 기존의 경험적 연구결과와 비교하여 그 실효성도 확인되었다. 실용적인 측면에서, 지진계가 설치된 댐이나 저수지에 대한 직접 조사가 불가하거나 예비해석 차원해서 사력존의 동적물성 확보가 필요한 경우, 본 연구에서 제시된 방법은 충분히 유용하게 활용될 수 있을 것으로 기대된다.

• 비파괴검사학회지
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• 제26권3호
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• pp.162-168
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• 2006

Speckle interferometry with phase-shifting method has been applied to measurement of micro-scale displacement through optical signal processing. Four-step phase-shifting method by PZT is used to measure out-of-plane displacement in spot-welded cantilever and results of optical experiments are comparable to those of FEM. Phase-shifting method using Fourier transform by PZT is applied to measurement of in-plane displacement on rectangular steel plate with a circular hole. The results of optical experiment agree well with theoretical calculation. New phase-shifting method in speckle interferometry has been implemented with a quarter wave plate. In-plane displacement of specimen is measured by the new phase-shifting method. Results of optical experiment show that the quarter wave plate can be used for phase-shifting method that is cheap and easy to use in speckle interferometry.

• 전기전자학회논문지
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• 제11권3호
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• pp.117-121
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• 2007

20 GHz and 40 GHz micro/millimeter-wave photonic pulse trains have been generated from a fiber ring laser with a semiconductor optical amplifier (SOA) by injecting 2 GHz gain-switched Fabry-Perot laser diode (GS-FPLD) output. To achieve efficient cross-gain modulation in the SOA at 20 GHz and 40 GHz, individual lasing modes of the 2 GHz GS-FPLD output separated to 25 and 50 picoseconds respectively by passing dispersion compensating fibers.

• 지구물리와물리탐사
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• 제14권4호
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• pp.324-334
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• 2011

석모도에서 산출되는 암석시료를 이용하여 파괴강도를 5단계로 나누고 하중을 증가시키면서 손상 진행에 따른 P-, S-파 속도의 변화 특성을 고찰하였다. 재하 전 상태에서부터 일축압축강도의 95%까지 하중을 받은 9개의 수포화 시험편들이 1시간 동안 상온에서 건조되어 가는 동안 탄성파 속도는 암종별로 변화폭이 상이하였으며, P-파의 경우 0.9 ~ 18.3%, S-파 속도는 2.8 ~ 14.8% 로 큰 차이를 보였다. 하중에 의해 건조한 암석에 미세균열이 발생하면 P-파 속도가 일률적으로 감소하는 현상과는 달리, 수포화 암석의 경우는 균열생성에 의한 속도 감소 요인과 수포화에 의한 속도 상승요인의 상호작용에 의해 속도 증감 양상이 매우 복잡하게 나타나지만 대부분의 경우에서 전반적으로 재하 초기단계에서는 속도가 증가하다가 나중에는 감소하는 경향을 보였다. 감소가 시작되는 시점도 암종별로 1 ~ 4단계로 다양하다. 파괴 후에도 형태를 보존한 25h-2와 29-2 시료에 대해서 파괴후의 속도를 측정한 결과는 현저한 공극율의 상승과 함께 탄성파 속도도 현저히 감소하였다. 조암광물별로 보면 석영 함량이 증가하면 탄성계수가 커지며 층상구조형 규산염광물이 증가하면 탄성계수는 작아지는 경향을 보였다.

• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 하계학술발표회 논문집
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• pp.43-44
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• 2006

• 한국정밀공학회지
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• 제16권2호통권95호
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• pp.74-81
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• 1999

The integrated chip of optical micro-encoder was fabricated and the feasibility as displacement measurement device was confirmed. The geometry of micro-encoder was designed to utilize the optical interference effect on the second order of diffracted beams. The hybrid-type micro-encoder consisted with light emitting diode, photodiode, polyimide wave-guide and micro-lens provides stable micro-encoding results for high speed displacements. The measurement shows the resolution of displacement of 1.00 +/- 0.02 ${\mu}m$ for the grating with scale pitch of 2.0${\mu}m$.