• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1995년도 춘계학술대회
• /
• pp.235-238
• /
• 1995

In this paper, we propose an effective coding method of the angiography by using the scalable structure in the frequency domain for MPACS(Medical Picture Archiving and Communication System). We employed the subband decomposition method and MPEG-2 system which is the international standard coding method of the general moving picture. After the subband decomposition is applied to split an input image into 4 bands in the spatial frequency domain, the motion compensated DPCM coding method of MPEG-2 is carried out for each subband. As a result, an easily controllable coding Structure is accomplished by composing the compound hit stream for each subband group. Follows are the simulation results of the proposed sheme for the angiography. A scalable structure which can be easily controlled for a loss of transmission or the band limit can be accomplisbed in the MPEG-2 stucture by the subband decomposition minimizing the side information. And by reducing the search area of the motion vector between -4 and 3, the processing speed of a codec is enhanced by more than two times without a loss of the picture quality compare with the conventional DCT coefficients decompositon method. And the processing speed is considerably improved in the case of the parallel construction of each subband in the hardware.

• 한국보건간호학회지
• /
• 제13권1호
• /
• pp.63-76
• /
• 1999

The purpose of this study was to provide the basic data for developing a program for effective health education about AIDS (Acquired Immunodeficiency Syndrome) by investigating the knowledge and attitudes of middle and high school students about AIDS. The subjects were 476 middle school students and 658 high school students from Seoul and Kang Won province. The data were collected from November 19 to December 18. 1996. using a 56-item questionnaire. and analyzed by SAS program for t-test. x2-test. and pearson correlation coefficients. The results were as follows : 1. High school students had more knowledge than middle school students about AIDS. 2. Male. students from Seoul. and students who had drinking experience and smoking experience among middle school students. and male. students from Seoul. and students of non-coeducation among high school students were more knowledgeable about AIDS. 3. Misconceptions about the transmission of AIDS through non-intimate contact were especially common among middle school students. And a high proportion of middle and high school students knew very little about the symptoms of AIDS. 4. High school students had more positive attitudes toward AIDS than middle school students. 5. Students from Seoul and students who had smoking experience among middle school students. and students from Seoul and non-coeducation and students who had substance use experience among high school students were more positive attitudes about AIDS. 6. Most of the middle and high school students agreed that there is a need for AIDS education. 7. Middle and high school students reported that had learned about AIDS mostly from TV. Since students in the middle-school age group are especially at risk for developing AIDS­related behaviors. this study findings suggest that it is crucial to develop school-based AIDS education programs that help students acquire the knowledge and attitudes to adopt and maintain behaviors that reduce the risk of HIV (Human Immunodeficiency Virus) infection and other related health problems.

• 한국환경보건학회지
• /
• 제45권6호
• /
• pp.622-629
• /
• 2019

Objectives: The occurrence of norovirus food poisoning in South Korea has been reported since 2003. This study was performed to investigate the characteristics of norovirus food poisoning outbreaks in Korea from 2006 to 2015 and to analyze the relationship between these outbreaks and climate factors. Methods: Data on norovirus food poisoning outbreaks were obtained from the Korea Ministry of Food and Drug Safety. Data on climate factors were obtained from the Korea Meteorological Administration. Frequency analysis and Pearson's correlation analysis were adopted for this study. Results: During the study period, norovirus was the greatest contributing factor of food poisoning outbreaks. Approximately half of the outbreaks of norovirus food poisoning occurred in winter. Average temperature, highest and lowest temperatures, precipitation, number of days with rainfall, and humidity all had a significant negative correlation with monthly number of outbreaks of norovirus food poisoning (p<0.05). Among these, the lowest and average temperature showed higher correlation coefficients. However, the sum of the outbreaks in spring and autumn was similar to that of winter, and more than one-third occurred in group meal-service settings, including school lunches. This was strongly assumed as the use of norovirus-contaminated groundwater for preparation of meals in some settings. Conclusion: The cold and dry of the winter season in Korea may assist the transmission of norovirus. Also, the use of groundwater in group meal service is suspected of inducing a larger scale of norovirus food poisoning. Both health authorities and community-based prevention and control measures are required to respond to these complex etiological outbreaks.

• 한국전자파학회논문지
• /
• 제24권9호
• /
• pp.892-899
• /
• 2013

본 논문에서는 (서브)밀리미터파 대역에서 산란 계수 정밀 측정이 어려운 요인 및 보다 정확한 측정을 하기 위한 방안을 기술하였으며, G-band(140~220 GHz)에서의 측정 사례를 제시하였다. 우선 마이크로파 대역과 (서브)밀리미터파 대역에서 사용되는 산란 계수 측정시스템(벡터회로망 분석기)의 동작 원리에 대한 차이점을 파악하고, (서브)밀리미터파 대역 산란 계수 측정시스템을 보다 잘 운영하기 위한 방안을 기술하였다. 그리고 더 좋은 도파관 전송 특성 및 연결 반복도를 얻기 위한 방안과 반사 계수 크기가 작은 피측정기를 정밀 측정하기 위한 방안을 기술하였다.

• 디지털융복합연구
• /
• 제12권3호
• /
• pp.249-254
• /
• 2014

무선 랜 시스템은 고속의 데이터를 전송하기 위하여 끊임없이 진화 중이며 통신성능을 향상시키기 위해서는 더욱 정밀한 채널추정이 필수적으로 요구된다. 본 논문에서는 IEEE 802.11 기반 무선 모뎀의 PLCP 구조에서 기존의 긴 훈련심볼만을 이용하여 채널을 추정하는 LS 알고리즘의 성능을 개선하고자 하였다. 48개의 부반송파 중에서 12개의 위치에 짧은 훈련 심볼을 전송하고 있다는 사실을 이용하여 2개의 긴 훈련심볼 뿐만 아니라 하나의 짧은심볼도 함께 사용하여 채널을 추정하는 새로운 LS 추정 알고리즘을 제안하였다. 두 개의 긴 훈련심볼 뿐만 아니라 짧은 훈련 심볼을 이용함으로써 보다 향상된 채널 추정을 제공할 수 있음을 보였으며 제안된 채널 추정알고리즘은 IEEE 802.11p WAVE 차량통신 시스템에도 적용이 가능하리라 생각된다. 또한 학부 및 대학원의 OFDM 관련 채널 추정 교육 시 본 논문의 내용이 유용하게 사용될 수 있을 것이다.

• 한국통신학회논문지
• /
• 제31권3A호
• /
• pp.240-248
• /
• 2006

본 연구에서는 OFDM을 사용하는 IEEE 802.11p WAVE 기본 spec를 목표로 기존 전송 포맷을 유지하면서 장거리 coverage에서의 feasibility에 대한 연구 및 이를 지원하기 위한 수신 알고리즘에 대한 연구를 수행한다. 특히, 넓은 coverage의 지원을 목적으로 할 때 큰 RMS 지연 확산에 의해 발생할 수 있는 ISI/ICI의 효과를 고려하여 채널 단축 시간영역 등화기(channel shortening TEQ)를 사용하는 수신 시스템을 구성하였고 기존 무선랜 규격에서 정의하는 프리앰블을 등화기 계수의 추정에 사용할 경우에 대해 시스템의 성능을 평가하였다. 이는 WAVE 환경에서 목표로 하는 확장된 coverage의 경계에서 RMS 지연 확산이 클 때 16QAM을 통한 서비스가 가능한가에 대한 부분적인 대답을 제공하기 위한 것으로 (1) 목표 채별 환경에서 어느 정도의 성능을 내기 위해 요구되는 TEQ 파라미터 분석, (2) 지수함수의 Power-delay profile을 갖는 채널에서의 PER 성능의 평가 등을 포함한다.

• 비파괴검사학회지
• /
• 제32권5호
• /
• pp.509-517
• /
• 2012

본 연구에서는 상용화된 monomer-cast nylon (MC nylon)계 고분자 재료로 만든 6종류의 시편에 대하여 감쇠계수 및 위상속도와 같은 초음파 특성의 온도 및 주파수 의존성을 조사하였다. 시편의 초음파 특성은 수중에서 2 MHz부터 8 MHz까지의 광대역 주파수 범위에 대하여 펄스투과법을 이용하여 측정하였다. 수온은 $10^{\circ}C$부터 $60^{\circ}C$까지 $10^{\circ}C$ 간격으로 변화시켰다. 측정에 사용된 모든 시편에서 감쇠계수는 주파수가 증가함에 따라 증가하였으며, 주파수의 지수 의존성 n이 선형 (n=1)에서 약간 벗어난 1.16부터 1.44이내의 값을 가졌다. 위상속도는 $60^{\circ}C$에서 ivory 시편을 제외한 모든 경우에 대하여 주파수가 증가함에 따라 감소하는 음의 분산 특성을 나타냈다. 주파수에 의존하는 위상속도는 모든 시편에서 온도가 증가함에 따라 감소하는 특성을 나타내었다.

• 전자공학회논문지
• /
• 제53권3호
• /
• pp.21-28
• /
• 2016

시간 상관 채널에 대한 차분 코드북의 적응형 기법을 제안한다. 제안하는 코드북의 코드워드 인자들은 M의 값이 8, 16 또는 32인 M-PSK 성운의 여러 집합 중에서 선택된다. 본 논문에서는 먼저 코드북의 최적의 구면 캡 반경을 어떻게 추적하는지 수학적으로 분석하고 적응형 기법의 구현 방법에 대해 설명한다. 본 논문의 차분 코드북들은 무선 채널 시간 상관 계수에 의해 적응적으로 선택되므로 항상 채널 상태에 따르는 최적의 코드북을 이용하여 송수신을 한다. Monte-Carlo 시뮬레이션은 제안하는 코드북의 성능이 같은 양의 피드백 정보를 가진 M-PSK 성운을 이용하는 비적응형 코드북보다 항상 우수함을 보인다.

• Journal of the Optical Society of Korea
• /
• 제18권3호
• /
• pp.244-250
• /
• 2014

Due to the difficulty in measuring very low out-of-band cutoff depths of solar blind UV filters, we propose a cutoff depth adjustable measurement system (CDAM) to test deep cutoff filters with a large dynamic range. The CDAM utilizing the substitution method is elaborately composed of several parts, including narrow-band LED light sources, standard reflective neutral attenuators with known attenuation coefficients, and a photomultiplier (PMT). This paper also presents an attenuator combination method ensuring that the PMT works within its linear response range. In addition, numerical simulation testifies to the method, and experiment shows that the CDAM system can achieve an extension of dynamic range from 0-6 OD to 0-10 OD, which is sufficient for the measurement of out-of-band cutoff depths of solar blind UV filters. Above all, the CDAM system, being easily implemented, of wide dynamic range, and highly precise, could be widely used in the measurement of filter cutoff depth.

• 한국해양공학회지
• /
• 제33권1호
• /
• pp.68-75
• /
• 2019

A low-crested structure (LCS) is an excellent feature not only because it provides shore protection but also because it is fully submerged. However, in order to properly control waves, it is necessary to maintain a certain range of crest height and width in consideration of the wave dimensions at the installation area. According to previous studies, an LCS has some wave breaking effect when the crest width is more than a fourth of the incident wavelength and the crest depth is less than a third of the incident wave height. In other words, if the crest width of the LCS is small or the crest depth is large, it cannot control the wave. Therefore, when an LCS is installed in a large sea area with a great tidal range in consideration of the landscape, waves cannot be blocked at high tide. In this study, the hydraulic performances of a typical trapezoidal LCS with a constant crest height and a low-crested structure with an adjustable crest height, which was called a tide-adapting low-crested structure (TA-LCS) in this study, were compared and evaluated under various wave conditions through hydraulic experiments. It was found that the wave transmission coefficients of the TA-LCS at high tide were lower than the values for the typical LCS based on empirical formulas. In addition, the hydraulic performances of the TA-LCS for wave reflection control were 12.9?30.4% lower than that of the typical LCS. Therefore, the TA-LCS is expected to be highly effective in controlling the energy of incoming waves during high tide even in a macro-tidal area.