• 동력기계공학회지
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• 제8권4호
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• pp.31-37
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• 2004

The damping capacity and strength of Fe-2Al-26Mn alloys have been studied for the development of new materials with high strength and damping capacity. Particularly, the effect of ${\alpha}'\;and\;{\varepsilon}$ martensite phase, which constitutes the microstructure of cold rolled Fe-Al-Mn alloys, has been investigated in terms of the strength and damping capacity of the alloys. The damping capacity rises with increasing the degree of cold rolling and reveals the maximum value at 25% reduction. The damping capacity is strongly affected by the volume fraction of ${\varepsilon}$ martensite, while the other phases, such as ${\alpha}'$ martensite and austenite phase, actually exhibit little effect on damping capacity. Considering that tensile strength increases and elongation decreases with increasing the volume fraction of ${\alpha}'$ martensite, it is proved that tensile strength is mainly affected by the amount of ${\alpha}'$ martensite.

• Journal of Biosystems Engineering
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• 제28권1호
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• pp.27-34
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• 2003

Present combustion engines have reached almost at the limit of development due to the fundamental structural problems. This study was carried out to propose a new concept internal combustion engine which has great potential advantages to the conventional engines. Proposed new concept engine is a kind of rotary engine. A rotor is rotating concentrically in a cylinder which is divided into two partitioning valves. and it makes four compartments in the cylinder. The volumes of each of four compartments are changing continuously with the rotor movement, and performs the functions of intake, compression. expansion and exhaust simultaneously. The results of this study can be summarized as follows. 1. Expected theoretical thermal efficiency is 44.9 percent at the condition of 1000rpm and compression ratio of 8.0. which is almost the same as that of the conventional engines. i.e., piston and Wankel rotary engine. 2. The new concept engine has 2. working strokes in every revolution. Therefore. the new concept engine can reduce the specific weight and volume than four-stroke piston engine. 3. The torque variation is very small. therefore minimal noise and vibration are expectable. 4. The new concept engine can reduce mechanical energy loss than piston engine because neither crank mechanism nor eccentrical motion exists.

• 항공우주기술
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• 제3권1호
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• pp.109-116
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• 2004

일반적으로 위성에 장착된 GPS 수신기는 GPS 위성으로부터 항법 신호를 받아서 위성의 위치, 시간 및 속도 정보를 제공하는 것을 주요 목적으로 하고 있다. 이러한 정보를 근거로 위성의 현재 위치정보 및 임무 수행을 위한 정보를 유도하게 된다. 2005년 발사예정인 아리랑 위성2호는 GPS 수신기에서 나오는 IPPS 신호를 위성체 각 프로세서의 기준시간으로 사용되며 DPLL, FEP회로 및 운용소프트웨어(FSW)에 의하여 동작된다. 본 논문에서는 아리랑 위성2호(KOMPSAT-2,이하 K2)의 시간동기구조에 대한 구조 및 설계에 대한 뿐 아니라 정밀도 분석 및 시험결과등 전 과정에 대한 내용을 기술하였다.

• 한국컴퓨터정보학회논문지
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• 제4권4호
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• pp.77-85
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• 1999

본 논문은 Kass가 제안한 수식을 수정했다. 첫 번째로, 물체의 내부나 외부에 초기 값을 설정할 수 있도록 하였으며, 물체의 윤곽선을 보다 빨리 쉽게 추출할 수 있고 에지가 강한 곳으로 움츠려드는 것을 개선하였다. 두 번째로 내부에너지 수식을 개선하였고, $3{times}3$ 행렬을 사용하였다. 세 번째로 에너지 항을 부과하여 한 점에 모이는 현상을 처리했고, 임계값을 사용하여 윤곽선을 정확하게 추출하도록 알고리즘을 수정하였다. 알고리즘을 수정한 결과, 초기 값을 쉽게 설정했고 높은 곡률의 물체도 추출했다. 피드백시스템을 사용하여 처리속도를 개선했다.

• Nuclear Engineering and Technology
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• 제43권4호
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• pp.343-354
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• 2011

It is critically important to identify unexpected loose parts in a nuclear reactor pressure vessel, since they may collide with and cause damage to internal structures. Mass estimation can provide key information regarding the kind as well as the location of loose parts. This study proposes a mass estimation method based on an artificial neural network (ANN), which can overcome several unresolved issues involved in other conventional methods. In the ANN model, input parameters are the discrete cosine transform (DCT) coefficients of the auto-power spectrum density (APSD) of the measured impact acceleration signal. The performance of the proposed method is then evaluated through application to a large-sized plate and a 1/8-scaled mockup of a reactor pressure vessel. The results are compared with those obtained using a conventional method, the frequency ratio (FR) method. It is shown that the proposed method is capable of estimating the impact mass with 30% lower relative error than the FR method, thus improving the estimation performance.

• 한국광학회지
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• 제6권4호
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• pp.365-372
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• 1995

취상변조기나 3*3 광결합기와 같은 특수 광부품을 사용하지 않고도 간섭형 센서의 고감도를 유지할 수 있고, 주변환경의 변화에도 영향을 받지 않는 간섭형 광섬유 센서를 위한 신호처리 기술을 소개하였다. 이 기법은 간섭형 센서의 넓은 다이나믹 레인지와 고감도를 유지한 신호처리를 위해 레이저 다이오드의 주파수 처핑을 이용하며 주변환경의 변화에 의한 측정에러를 보상하기 위해 별도의 간섭계를 기준 간섭계로 사용하였다. 새로운 신호처리 기법을 거울 내장형 Fabry-Perot(FT) 간섭계 온도센서에 적용한 결과 1cm 광섬유 FP 간섭계 센서소자로 부터 $4\times10^{-3\circ}C$(광위상 4.5mrad)의 분해능을 얻었으며 광위상 변화량의 크기가 $\pi$ 이내로 제한되지 않으므로 다이나믹 레인지가 넓은 온도센서의 구현이 가능하였다.

• Archives of Pharmacal Research
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• 제19권5호
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• pp.396-399
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• 1996

High-performance liquid chromatographic method with UV detecction was developed for the determination of theophylline and its metabolites in human urine using ${beta}$-hydroxyethyl theophylline$({beta} -HET)$ as an internal standard. For extraction of urine sample, quality control sample and xanthine-free blank urine were mixed with decylamine (ion-paring reagent) and ${beta}$-HET. After saturation with ammonium sulfate, the mixture was then extracted with organic solvent at pH values of 4.0-4.5. All separations were performed with ion-pair chromatography using decylamine as an ion-pairing reagent and 3mM sodium acetate buffered mobile phase (pH 4.0) containing 1% (v/v) acetonitrile and 0.75 mM decylamine. The detection limits of theophylline, 1, 3-DMU, 1-MU, 3-MX and 1-MX in human urine were 0.17, 0.17, 0.39, 0.19 and 0.19 ${\mu}g$/ml, based on a signal-to-noise ratios of 3.0. The mean intraday coefficients of variation (C.V.s) of each compound on nine replicates were lower than 2.0%, while mean interday C.V.s on three days were lower than 1.6%. All separations were finished within 40miutes.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권4호
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• pp.528-533
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• 2016

A low voltage high PSRR CMOS Bandgap circuit capable of generating a stable voltage of less than 1 V (0.8 V and 0.5 V) robust to Process, Voltage and Temperature (PVT) variations is proposed. The high PSRR of the circuit is guaranteed by a low-voltage current mode regulator at the central aspect of the bandgap circuitry, which isolates the bandgap voltage from power supply variations and noise. The isolating current mirrors create an internal regulated voltage $V_{reg}$ for the BG core and Op-Amp rather than the VDD. These current mirrors reduce the impact of supply voltage variations. The proposed circuit is implemented in a $0.35{\mu}m$ CMOS technology. The BGR circuit occupies $0.024mm^2$ of the die area and consumes $200{\mu}W$ from a 5 V supply voltage at room temperature. Experimental results demonstrate that the PSRR of the voltage reference achieved -118 dB at frequencies up to 1 kHz and -55 dB at 1 MHz without additional circuits for the curvature compensation. A temperature coefficient of $60 ppm/^{\circ}C$ is obtained in the range of -40 to $120^{\circ}C$.

• 한국정보처리학회논문지
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• 제4권3호
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• pp.871-879
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• 1997

지리 정보 시스템의 구축을 위한 기존의 수치 지도화 방법은 많은 비용과 시간이 소요되는 작업이므로 자동입력을 위한 도구의 필요성이 절실하다 지도의 특징을 살펴 보면, 몇 가지 특징적인 색을 이용하여 정보를 계층화시켜 작성되어 있으므로, 영상에서 색 정보를 분리하면, 여러 가지 정보를 효율적으로 추출할 수 있다. 본 논문에서는 칼라 지도 영상에서 도로 정보를 추출하는 알고리즘을 제안하였다. 스캐너로 입력된 칼라 지도영상을 색 계층별로 분리하고, 도로를 포함하고 있는 영상에서 모폴로지 연산의 하나인 조건적 볼림 연산을 병렬적으로 적용하는 알고리즘을 제안하였다. 제안된 복원 알고리즘을 이용하여 정보의 중첩으로 인한 도로의 훼손된 부분을 효율적으로 복원하였으며, 세선화와 벡터화를 통하여 도로의 정보를 표현하였다.

• Structural Engineering and Mechanics
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• 제41권1호
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• pp.25-41
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• 2012

Kriging surrogate model provides explicit functions to represent the relationships between the inputs and outputs of a linear or nonlinear system, which is a desirable advantage for response estimation and parameter identification in structural design and model updating problem. However, little research has been carried out in applying Kriging model to crack identification. In this work, a scheme for crack identification based on a Kriging surrogate model is proposed. A modified rectangular grid (MRG) is introduced to move some sample points lying on the boundary into the internal design region, which will provide more useful information for the construction of Kriging model. The initial Kriging model is then constructed by samples of varying crack parameters (locations and sizes) and their corresponding modal frequencies. For identifying crack parameters, a robust stochastic particle swarm optimization (SPSO) algorithm is used to find the global optimal solution beyond the constructed Kriging model. To improve the accuracy of surrogate model, the finite element (FE) analysis soft ANSYS is employed to deal with the re-meshing problem during surrogate model updating. Specially, a simple method for crack number identification is proposed by finding the maximum probability factor. Finally, numerical simulations and experimental research are performed to assess the effectiveness and noise immunity of this proposed scheme.