• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.210-213
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• 1999

A battery is the device that transforms the chemical energy into the direct-current electrical energy directly without a mechanical process. Unit cells are connected in series to obtain the necessary voltage, while being connected in parallel to organize capacity for load current and to decrease the internal resistance for corresponding the sudden shift of the load current. The circular-current, however, could be occurred when the system is driven in parallel. As a result, the new batteries are heated by over-change and discharge, and the over charge current makes to increase the rust of the positive grid and consequently the shortened life of the new batteris would be shown. In this paper, the internal resistance of charge and discharge will be balanced, through inserting the resistance into the system by way of calculation of the changed amount of internal resistance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1789-1794
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• 2003

Transient and asymmetric density distributions have been investigated by digital speckle tomography. Multiple CCD images captured movements of speckles in three angles of view simultaneously because the flows were asymmetric and transient. The speckle movements between no flow and downward butane flow from a circular half opening have been calculated by a cross-correlation tracking method so that those distances can be tranferred to deflection angles of laser rays for density gradients. The three-dimensional density fields have been reconstructed from the fringe shift by a real-time multiplicative algebraic reconstruction technique (MART).

• 한국정밀공학회지
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• 제7권1호
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• pp.63-73
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• 1990

Low cost automatic welding machine is developed for the purpose of welding process automation of automobile parts with two dimensional welding joints. Developed gantry type machine is equipped with X, Y and roll axis stepping motors, and dirive units units are designed by two phase on drive scheme using shift registers. Control system is constructed by single board microcomputer of Z80A CPU, and also it is equipped with parallel input output ports and counter-timer chips. Linear and circular interpolation of welding head movement is accomplished by employing software digital differential analyzers. It has been shown that contour error of develped system is withi ${\pm}1.0mm$, meaning that the machine is suitable for CO2 arc welding process of automoble parts and is expected it's application to industry.

• 대한의용생체공학회:의공학회지
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• 제29권5호
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• pp.364-370
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• 2008

Recent development in large area flat-panel x-ray detector technology enables clinical application of digital tomosyntesis. Unlike conventional motion tomography using x-ray films, flat-panel x-ray detectors provide projection images in digital formats so that tomographic images can be synthesized in a more flexible way. For the digital tomosynthesis, precise movements of the x-ray source and the x-ray detector with respect to a fulcrum point are necessary. In this study, we apply the digital tomosynthesis technique to the flat-panel detector based micro-CT in which the flat-panel detector and the x-ray source rotate together on a circular arc. The experimental results suggest that flat-panel detector based 3D CTs can be used for digital tomosynthesis in the clinical environment.

• 한국정밀공학회지
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• 제16권10호
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• pp.87-93
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• 1999

To propose a useful modelling method for an actual muffler, the noise attenuation effects of muffler was investigated according to the flow condition and the hole shape of tubes. In this work, the finite element method was used to calculate the transmission loss of muffler, The noise attenuation characteristics of four different types of muffler in the hole shape of tubes were compared mutually to find a more simple equivalent model. Analytical results showed that the overall value of transmission loss increases and the peaks of transmission loss curve shift to the low frequency with mean flow for the given muffler, Also the noise attenuation characteristics of the equivalent model having the split holes is almost the same as those of the actual muffler having many circular holes.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.14-14
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• 2011

Graphene is known to possess excellent thermal properties, including high thermal conductivity, that make it a prime candidate material for heat management in ultra large scale integrated circuits. For device applications, the key parameters are the thermal expansion coefficient and the thermal conductivity. There has been no reliable experimental determination on the thermal expansion coefficient of graphene whereas the estimates of the thermal conductivity vary widely. In this work, we estimate the thermal expansion coefficient of graphene on silicon dioxide by measuring the temperature dependence of the Raman spectrum. The shift of the Raman peaks due to heating or cooling results from both the intrinsic temperature dependence of the Raman spectrum of graphene and the strain on the graphene film due to the thermal expansion mismatch with silicon dioxide. By carefully comparing the experimental data against theoretical calculations, it is possible to determine the thermal expansion coefficient. The thermal conductivity is measured by estimating the thermal profile of a graphene film suspended over a circular hole of the substrate.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2001년도 추계학술발표논문집 (상)
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• pp.711-714
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• 2001

본 논문에서는 파이프라인 구조를 이용하여 고성능 1 차원 이산 웨이블렛 변환 필터를 설계하였다. 각 레벨에서 입력이 다운샘플링(downsampling, decimation)되므로 각 레벨의 하드웨어를 폴딩(folding) 기법을 이용하여 곱셈기와 덧셈기를 공유함으로써 복잡도를 개선하였다. 즉, 제안한 구조에서는 레벨 2 와 레벨 3 에서 폴딩된 구조의 C.S.R(Circular Shift Register)곱셈기와 덧셈기를 사용함으로써 하드웨어 효율(hardware utilization)을 각 레벨에서 100%로 높일 수 있다. 또한, 홀수와 짝수의 샘플을 병렬로 입력함으로써 단일 입력의 시스템과 비교할 때, 동일 시간에 병렬화 만큼의 이득을 얻을 수 있었고, 필터 계수는 미러 필터(mirror filter)의 특성을 이용하여 쳐대한 고역 필터(high pass filter)와 저역 필터(low pass filter)의 계수들을 공유함으로써 곱셈기와 덧셈기의 수를 반으로 줄였다. 그리고 임계 경로(critical path)를 줄이기 위한 파이프라인 레지스터를 삽입하여 고성능 시스템을 구현하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.450-453
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• 2008

During the drawing of reentrant section like a spline, the unfilled in the corner of dies or the bended product emerges from the large reduction of area, the complex shaped sections and other nonuniform properties in material and lubrication conditions. In this study, the drawing of the spline section with the non-rotary symmetry from a circular aluminum billet has been analyzed by using commercial code DEFORM-3D. A new die construction method preventing the spline from the drawback of bending and the unfilled defect has been suggested and verified through the analysis using centroid shift method and the hybrid construction between converged and diverged profile.

• Bulletin of the Korean Chemical Society
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• 제18권5호
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• pp.510-514
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• 1997

We studied the interaction of 4',6-diamidino-2-phenylindole (DAPI) with single stranded poly(dA) using optical spectroscopic methods, including absorption, circular dichroism (CD), and fluorescence spectroscopy. The temperature-dependent conformation of poly(dA) was also investigated. The conformation of poly(dA) varied with temperature, which is explained by the stacking-destacking process of the adenine bases, resulting from the sugar conformation. The hypochromicity and red-shift in the absorption spectroscopy, the lack of CD change in the drag absorption region, and the fluorescence behavior, especially a great accessibility of the I2 quencher to the poly(dA)-bound DAPI, suggest that DAPI binds to the outside of poly(dA). The Job plot for the DAPI-poly(dA) mixture demonstrated that a stoichiometry of one DAPI molecule binds to the one phosphate of poly(dA).

• Wind and Structures
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• 제17권5호
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• pp.465-477
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• 2013

In this paper, the effects of parapets on the mean and fluctuating wind pressures which are acting on a flat top of a finite cylinder vertically placed on a flat plate have experimentally been investigated. The aspect ratio (AR) of cylinder is 1 and the Reynolds number (Re) based on cylinder diameter and free stream velocity is 150000. The pressure distributions on the flat top and the side wall of the finite cylinder immersed in a simulated atmospheric boundary layer have been obtained for different parapet heights. The large magnitudes of mean and minimum suction pressures occurring near the leading edge were measured for the cases with and without parapet. They shift to the further downstream on the circular top with increasing parapet height. It is seen that the parapets reduce the local high suction on the top up to 24%.