• 수산해양기술연구
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• 제25권4호
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• pp.200-208
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• 1989

200MHz ZnO변환기를 이용하여 초음파 현미경을 제작하여, 도미비늘을 화상화하고 광학현미경에 의한 사진과 비교하였다. 그 결과 광학적 반사에 의한 표면의 화상과 초음파의 기계적 탄성적 표면하 반사에 의한 화상에는 다소 차이가 있음을 확인하였다(Fig. 13 및 14). 초음파 현미경은 고체재료 또는 생물조직 상(10(12)등 여러 가지 생물연구 등의 응용이 계획되고 있으며, 특히 초음파 의학의 분야는 그 활용이 눈부실 것으로 예측된다. 초음파 현미경의 제작 그 자체보다, 이것을 도구로 하여 여러 가지 학술적, 기술적 성과가 기대되기 때문에 이 분야의 기초연구가 더욱 중요하게 생각되며 첨단산업분야에서도 비파괴검사 초음파 micro spectroscopy(U.M.S)등과 같은 물질의 탄성적 성질을 micro scale로 계측할 수 있는 등, 많은 활용이 있을 것이 예상된다. 또 초음파 현미경의 방법도 여러 가지이며, 이것을 계측수단으로 일반화하는 문제도 연구할 필요가 있다. 앞으로 광학이나 전자장치 등과 함께 급속한 발전이 기대된다.

• 한국군사과학기술학회지
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• 제16권6호
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• pp.847-856
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• 2013

In this study, thermal performance of recuperators with plain and offset strip fins is investigated to enhance the thermal efficiency of a micro gas turbine. Thermal cycle analysis is conducted to determine major design parameters of a single-pass counterflow recuperator. In order to evaluate the performance of the recuperator, the effectiveness and the pressure drop in the recuperators are chosen as the objective function and the design constraint, respectively. The optimized geometries for internal structure of the recuperators with plain and offset strip fins are obtained with varying the fin spacing and height. From the result, the recuperator with offset strip fins has better thermal performance when the fin spacing, s, is smaller than 1.45mm and the thermal performance of the recuperator with plain rectangular fins is higher than that with offset strip fins in the region of $s{\geq}1.45mm$. In addition, it is found that the entrance region effect and the longitudinal wall heat conduction effect should be taken into account for accurately predicting the thermal performance of the recuperators with both plain and offset strip fins.

• 대한조선학회논문집
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• 제59권3호
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• pp.183-191
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• 2022

A design method for a propeller type rim-driven axial-flow turbine for a micro-hydropower system is presented. The turbine consists of pre-stator, impeller and post-stator, where the pre-stator plays a role as a guide vane to provide circumferential velocity to the on-coming flow, and the impeller as a rotational power generator by absorbing angular momentum of the flow. BEM(Blade Element Method), which is based on the turbine Euler equation, is employed to design the pre-stator and impeller blades. NACA 66 thickness form and a=0.8 mean camber line, which is widely accepted as a marine propeller blade section, is used for the pre-stator and turbine blade section. A CFD method, derived from the discretization of the RANS equations, is applied for the analysis of the designed turbine system. The design conditions of the turbine is confirmed by the CFD calculation. Turbine characteristic curve is calculated by the CFD method, in order to provide the performance characteristics at off-design operation conditions. The proposed procedures for the design of a propeller type rim-driven axial-flow turbine are established and confirmed by the CFD analysis.

• 설비공학논문집
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• 제1권4호
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• pp.265-275
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• 1989

An experimental study of decaying swirl air flow has been obtained by tangential inlet in a straight tube with Reynolds number range 20,000~40,000. The friction factor, swirl angle, velocity profiles and turbulent intensity are measured by using micro-manometer and hot-wire anemometer. It is found that the swirl flow behaviors depend on the swirl intensity along the test tube.

• Journal of Ubiquitous Convergence Technology
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• 제2권2호
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• pp.59-66
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• 2008

In this study, Software Defined Radio (SDR) technology-based digital filterbank architecture applicable to a multiple-channel processing system such as a wireless mobile communication system using Code Division Multiple Access (CDMA) technology is proposed. The technique includes a micro-processor to redesign Finite Impulse Response (FIR) filter coefficients according to specific system information and to download the filter coefficients to one digital Band Pass Filter (BPF) to reconfigure another system. The feasibility of the algorithm is verified by computer simulation and by implementing a multiple-channel signal generator that is reconfigurable to other system profiles, including those of a Wideband Code Division Multiple Access (WCDMA) system and a CDMA system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.331-333
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• 2004

In this study, we implement the multiple frequency bioelectrical impedance analysis system for body composition analysis. Overall system consists of : 1) conductivity electrodes to contact with hands and foots, 2) multiple frequency alternating current signal generator for generating 5, 50, 250kHz frequency and 800uA contained alternating current signal, 3) voltage signal detector, 4) phase signal detector, 5) key-pad to input individual information, 6) micro controller for data processing, 7) LCD for processed data to display, 8) system power, We explain the architecture of the system and required theory to implement the system. Finally, experimental results are illustrated to show the performance of the system.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2004년도 학술논문집
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• pp.230-231
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• 2004

경수로형 원자로의 증기 발생기 내부에 방사화 된 침적물을 smear paper로 시료를 채취한여 핵종 분석 및 화학조성을 분석하였다. 상용발전소의 증기 발생기 외부에서 발견된 고 준위 방사성물질의 화학 조성 분석은 극미세 성분분석기(EPMA)를 이용하였다. 본 시험에 사용한 EPMA(Electron Probe Micro Analyzer, SX-50R, CAMECA, Paris, France)는 고 방사능을 띤 조사 핵연료 및 재료 시험을 수행할 수 있도록 기기의 시편 stage 주위를 납과 텅스텐으로 차폐하여 시편의 방사능 세기가 $3.7{\times}10^{10}$ Bq까지 시험 가능한 기기이다.(중략)

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전력기술부문
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• pp.19-21
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• 2008

Renewable energy resources such as wind, wave, solar, micro hydro, tidal and biomass etc. are becoming importance stage by stage because of considering effect of the environment. Solar energy is one of the most successful sources of renewable energy for the production of electrical energy following wind energy. And, the solar/photovoltaic cell generators can not make two-state model as conventional generators, but should be modeled as multi-state model due to solar radiation random variation. The method of obtaining reliability evaluation index of solar cell generators is different from the conventional generators. This paper presents a basic study on reliability evaluation of power system considering solar cell generators with multi-states.

• 한국생산제조학회지
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• 제20권4호
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• pp.395-400
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• 2011

Scanning Probe Lithography is a method to localized oxidation on single crystal silicon wafer surface. This study demonstrates nanometer scale non contact lithography process on (100) silicon (p-type) wafer surface using AFM(Atomic force microscope) apparatuses and pulse controlling methods. AFM-based experimental apparatuses are connected the DC pulse generator that supplies ultra short pulses between conductive tip and single crystal silicon wafer surface maintaining constant humidity during processes. Then ultra short pulse durations are controlled according to various experimental conditions. Non contact lithography of using ultra short pulse induces electrochemical reaction between micro-scale tip and silicon wafer surface. Various growths of oxides can be created by ultra short pulse non contact lithography modification according to various pulse durations and applied constant humidity environment.

• International Journal of Precision Engineering and Manufacturing
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• 제8권4호
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• pp.45-49
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• 2007

When drilling using electrical-discharge machining (EDM), severe electrode wear makes in-process measurements of the depth of the drilled hole and the volume of material removed impossible. To estimate the volume of material removed a reliable real-time discharge pulse counting method is proposed by assuming that the volume removed in EDM is proportional to the number of discharge pulses from an iso-energy pulse generator. The geometry of machined holes, including depths and cross-sectional profiles, is estimated using geometric analysis. A proportional relationship between the volume of material removed and the number of discharge pulses was developed and verified by experiments.