• 한국컴퓨터정보학회논문지
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• 제12권3호
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• pp.85-93
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• 2007

본 논문에서는 시간에 따라서 변하는 삼차원 볼륨의 집합인 볼륨 비디오 데이터의 압축 기법을 제안하고 각각의 프레임을 실시간으로 압축 해제하며 가시화하는 방법을 설명하였다. 시변 볼륨 데이터는 한 프레임의 크기 조차도 매우 크기 때문에 그 크기를 줄이는 압축 기법을 수행할 필요가 있다. 그리고 실행 과정에서 일어나는 압축 해제는 시변 볼륨 데이터를 실시간으로 가시화 하는데 있어 병목 현상의 원인이 될 수 있다. 우리는 실행중의 압축 해제 속도와 데이터의 압축률을 높이기 위하여 삼차원 볼륨 데이터를 작은 블록으로 분해하고 충분히 많이 변하는 블록들을 갱신하는 방법을 제안하였다. 이 방법을 구현한 결과 본 논문에서 제안된 압축 및 압축 해제 기법이 압축 해제 속도와 압축에서 복원된 데이터의 정확성, 그리고 압축률의 정도를 조절하여 대용량 시변 볼륨데이터의 대화형 가시화를 가능하게 함을 알 수 있다.

• 한국분무공학회지
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• 제24권1호
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• pp.35-42
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• 2019

Syngas is widely produced by incomplete combustion of coal, water vapor, and air (oxygen) in a high-temperature/high-pressure gasifier through a coal-gasification process for power generation. In this study, a simulation syngas which was mainly composed of $H_2$, CO, $CO_2$, and $N_2$ was fueled with diesel. A modified single cylinder compression ignition (CI) engine is equipped with intake port syngas supply system and mechanical diesel direct injection system for dual fuel combustion. Combustion and emission characteristics of the engine were investigated by applying various syngas composition ratios and compression ratios. Diesel fuel injection timing was optimized to increase indicated thermal efficiency (ITE) at the engine speed 1,800 rpm and part load net indicated mean effective pressure ($IMEP_{net}$) 2 to 5 bar. ITE of the engine increased with the $H_2$ concentration, compression ratio and engine load. With 45% of $H_2$ concentration, compression ratio 17.1 and $IMEP_{net}$ 5 bar, ITE of 41.5% was achieved, which is equivalent to that of only diesel fuel operation.

• 한국자동차공학회논문집
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• 제5권2호
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• pp.50-59
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• 1997

When a front head of train enters a tunnel at a high speed, compression wave is generated at tunnel entrance due to the confinement effect and propagated along the tunnel with sound of speed. The propagated compression wave is reflected at tunnel exit due to abrupt pressure change at passage. The reflected wave is expansion pressure wave. And when the rear head of train goes through the tunnel entrance, another expansion pressure wave is generated and propagated along the tunnel. The pressure drop occurs seriously around train when the two expansion pressure waves come cross on train in the tunnel. In order to reduce the pressure drop, the compression wave front must be controlled because the intensity and magnitude of pressure drop is nearly proportional to that of compression wave at tunnel entrance. This study relates to reduction of the pressure wave gradient with respect to tunnel entrance shape change with various kind of angle and rounding. The results show characteristics of wave propagation in tunnel, usefulness of characteristic curve to estimate proper time domain size in numerical study and measuring time in actual experiment. Also rounding is contributed to improve pressure wave front even if its radius is very small at tunnel entrance. In order to improve of pressure wave front at tunnel entrance, proper angle is prefered to rounding with big radius and an angle of around 14$^{\circ}$ is recommended according to this simulations, And it is expected to reduce additional pressure drop in tunnel when the location and the size of the internal space for attendant equipment are considered in advance.

• Journal of Biosystems Engineering
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• 제7권1호
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• pp.53-61
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• 1982

As an attempt to reduce the consumption of petroleum resources and to improve the performance of a kerosene engine, a series of experiments was conducted using several kinds of ethanol-kerosene blends under the various compression ratios. The engine used in this study was a single-cylinder, four-cycle kerosene engine having a compression ratio of 4.5. To investigate the feasibility of ethanol-kerosene blends in the original engine, kerosene and blends of 5-percent, 10-percent, and 20-percent-ethanol, by volume, with kerosene were used. And to investigate the feasibility of improving the performance of the kerosene engine, a portion of the cylinder head was cut off to increase the compression ratio up to 5.0 by reducing the combustion chamber volume. Kerosene and blends of 30-percent and 40-percent-ethanol, by volume, with kerosene were used for the modified engine with an increased compression ratio. Variable speed tests at wide-open throttle were also conducted at five speed levels in the range of 1000 to 2200 rpm for each compression ratio and fuel type. Volumetric efficiency, engine torque, and brake specific fuel consumption were determined, and brake thermal efficiency based on the lower heating values of kerosene and ethanol was calculated. The results obtained in the study are summarized as follows: A. Test with the original engine: (1) No abnormal conditions were found when burning ethanol-kerosene blends in the original engine. (2) Volumetric efficiency increased with ethanol concentration in blends. When burning blends of 5-percent, 10-percent, and 20-percent ethanol, by volume, with kerosene, average volumetric efficiency increased 1.6 percent, 2.6 percent, and 4.1 percent respectively, than when burning kerosene. (3) Mean engine torque increased 5.2 percent for 5-percent-ethanol blend, 9.3 percent for 10-percent-ethanol blend, and 11.5 percent for 20-percent-ethanol blend than for kerosene. Increase in engine torque when using ethanol-kerosene blends was due to the improved combustion characteristics of ethanol as well as an increase in volumetric efficiency. (4) Up to ethanol concentration of 20 percent, mean brake specific fuel consumption was nearly constant inspite of the difference in heating value between ethanol and kerosene. (5) Brake thermal efficiency increased 0.3 percent for 5-percent-ethanol blend, 3.8 percent for 10-percent-ethanol blend, and 6.8 percent for 20-percent-ethanol blend than for kerosene. B. Test with the modified engine with an increased compression ratio: (1) When burning kerosene, mean volumetric efficiency, engine torque, and brake thermal efficiency were somewhat lower than for the original engine. (2) Engine torque increased 15.1 percent for 30-percent-ethanol blend and 18.4 percent for 40-percent-ethanol blend than for kerosene. (3) There was no significant difference in brake specific fuel consumption regardless of ethanol concentration in blends. (4) Brake thermal efficiency increased 15.0 percent for 30-percent-ethanol blend and 19. 5 percent for 40-percent-ethanol blend than for kerosene.

• 한국정보통신학회논문지
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• 제7권1호
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• pp.142-148
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• 2003

병원에서 발생하는 대용량 의료영상들을 저장 및 전송 할 경우에 저장 매체 수요의 증가와 네트워크 속도의 저하 등의 문제점들이 야기된다. 이러한 문제점들을 해결하기 위한 방안으로 의료영상의 압축이 필요하게 되었다. 본 논문에서는 개개의 여러 압축방법들로 하나의 통합된 환경에서 다양한 종류의 의료영상들을 압축할 수 있는 통합압축환경시스템을 설계 및 구현하였다. 이 통합압축환경에 구현된 압축방법들 중에는 DICOM 3.0규약을 따르는 RLC, 무손실 JPEG 압축방식, JPEG방식들이 있다. 그리고 JPEG2000에 사용되어진 이산웨이블릿변환을 이용한 압축방식과 병 변에 대한 정확성을 높이고 압축률을 좋게 하기 위해서 하나의 영상에서 무손실 압축과 손실 압축을 동시에 하는 방법을 제안하였다. 그리고 영상 정보를 효율적 관리할 수 있게 데이터베이스와 연동이 가능하도록 하였다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 추계학술대회
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• pp.225-228
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• 1996

ECG data are used for the diagnostic purposes with many clinical situations, especially heart disease. In this paper, an efficient ECG data compression technique by wavelet transform and high-speed vector quantization on PMS-B algorithm is proposed. In general, ECG data compression techniques are divided into two categories: direct and transform methods. The direct data compression techniques are AZTEC, TP, CORTES, FAN and SAPA algorithms, besides the transform methods include K-L, Fourier, Walsh, and wavelet transforms. In this paper, we applied wavelet analysis to the ECG data. In particular, vector quantization on PMS-B algorithm to the wavelet coefficients in the higher frequency regions, but scalar quantized in the lower frequency regions by PCM. Finally, the quantized indices were compressed by LZW lossless entropy encoder. As the result of simulation, it turns out to get sufficient compression ratio while keeping clinically acceptable PRD.

• 한국자동차공학회논문집
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• 제9권4호
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• pp.131-138
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• 2001

In this paper, performance of a dry CVT vehicle with torque cam is investigated. Based on belt transmission mechanism and torque cam actuator characteristics, an algorithm which is able to calculate the speed ratio from given thrust and load torque is suggested and a 3-D map is constructed for the speed ratio-thrust-torque. Using the 3-D map, a steady state characteristic of torque cam and a transient response of a dry CVT vehicle are investigated by simulation. It is found that initial spring compression plays a key role in determining the sliding criteria and the speed ratio velocity.

• 한국인쇄학회지
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• 제20권1호
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• pp.28-44
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• 2002

Wavelet transformation in image compression is to offer higher image compressibility and high-quality by quantization and entropy encoding. More image quality is good that reconstructed image by wavelet calculation than acquire cosine transform. Therefore, wavelet itself is function if it is wavelet's feature, in this function, do processing applying difference scale and resolution. That is, this is not that fixed resolution has been decided like existent compression way, when it regulated scale, damage goes in pixel and picture looks like break without giving damage entirely in reflex even if magnify or curtail Decoding. Therefore, this paper is in Image that using new wavelet application compression way research that see applies comparing In each image noted this time compressing step by step with circle image compression efficiency recognize. Also, estimated quality pass through by printing of compressed image, investigated compression ratio of most suitable that get print of high quality and elevation of transmission speed.

• 한국컴퓨터정보학회논문지
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• 제24권11호
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• pp.179-185
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• 2019

이 연구는 심폐소생술 중 거울을 활용한 시각적 효과를 이용했을 때 가슴압박의 질을 비교함으로써, 좀 더 나은 물리적 요소를 제공하여 효과적인 심폐소생술을 할 수 있도록 하는데 기초자료를 제공하고자 시행 되었다. 무작위 교차방법(Randomized Crossover Design)에 의한 실험 연구로 BLS Health Care-Provider 자격을 이수한 28명을 대상으로 가슴압박 시행 시 깊이, 속도, 압박 대이완의 비율, 팔의 각도, 용이성 등을 측정하였다. 수집된 자료는 SPSS Ver. 23.0 for Win 통계프로그램을 이용하여 분석하였다. 본 연구의 결과를 종합해 보면 심폐소생술에서 가슴압박 시행 시 거울을 활용한 가슴압박 방법을 이용한다면 효율적인 가슴압박을 할 수 있었고, 가슴압박의 평균 깊이, 압박 대 이완 비율, 팔의 각도, 구조자의 자세가 나아져 가슴압박의 질적 지표가 향상되었음을 알 수 있었다. 하지만 거울을 활용한 가슴압박 방법에 대해 다양한 환경요소 및 직군에 대하여 추가적인 연구를 통해 임상적 활용의 가능성을 확인하는 것이 필요 할 것이다.

• 대한교통학회지
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• 제34권3호
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• pp.248-262
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• 2016

이 연구는 수학교육자의 시각에서 도로 노면에 표시된 기호와 문자에 대해 분석한 결과이다. 연구의 목적은 운전자의 시각에서 가독성이 높은 도로 노면표시 방법을 제안하는데 있다. 이를 위해 이 연구에서는 사영기하학과 함수의 관점에서 도로 노면표시가 실제로 인식되는 모양을 분석하고, 압축비의 개념을 도입하여 바람직한 도로 표시의 대안을 제시하였다. 연구결과는 다음과 같다. 첫째, 압축비를 구하는 공식을 수립하였다. 노면표시에 대한 두 관찰각을 x, y라 하면 압축비 S는 ${\sin}y/{\cos}\(\frac{x-y}{2}\)$이 된다. 둘째, 압축비 및 실제로 운전자가 지각하는 노면표시에 대한 정보로부터 수학적 분석을 통해 노면표시에 대한 대안을 두 가지로 제시하였다. 하나는 압축비의 관점에서 노면표시를 개선하는 방법이고, 다른 하나는 가로 방향의 폭을 고정한 상태에서 세로 방향의 폭의 조절을 통해 개선하는 방법이다. 본 연구를 바탕으로 점선에 따른 속도 감각 인식에 대한 수학적 분석 연구가 진행될 수 있다.