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      • Study on DC-Offset Cancellation in a Direct Conversion Receiver

        박홍원,Park, Hong-Won 한국천문학회 2012 天文學會報 Vol.37 No.2

        Direct-conversion receivers often suffer from a DC-offset that is a by-product of the direct conversion process to baseband. In general, a basic approach to reduce the DC-offset is to do simple average of the baseband signal and remove the DC by subtracting the average. However, this gives rise to a residual DC offset which degrades the performance when the receiver adopts the coding schemes with high coding rates such as 8-PSK. Therefore, more advanced methods should be additionally required for better performance. While the training sequences are basically designed to have good auto-correlation properties to facilitate the channel estimation, they may be not good for the simultaneous estimation of the channel response and the DC-offset. Also the DC offset compensation under a bad condition does not give good results due to the estimation error. Correspondingly, the proposed scheme employs the two important points. First, the training sequence codes are divided into two groups by MSE(Mean Squared Errors) for estimating the channel taps and then SNR calculated from each group is compared to predefined threshold to do fine DC-offset estimation. Next, ON/OFF module is applied for preventing performance degradation by large estimation error under severe channel conditions. The simulation results of the proposed scheme shows good performances compared to the existing algorithm. As a result, this scheme is surely applicable to the receiver design in many communications systems.

      • KCI등재
      • 소년 소녀의 운동능력과 사지장과의 상관론적 연구

        박홍원,김동창 중앙대학교 의과대학 의과학연구소 1981 中央醫大誌 Vol.6 No.3

        The biometrial measurement and athletic record examination were performed to 7,666 Korean boys :and girls (consisting of 3,918 boys and 3,748 girls, ranging from 13 to 15 years of age) with the intention of studying the probable correlation between the length of the lower and upper extremities ,and athletic abilities, The athletic record examination in this study includes Running, Standing-Broad-jump, Ball-Throwing and Am-Flexing (Chin-Up in boys, Dangling with flexed arm in girls). The results obtained are as follows: 1. Running ability of 100 meter course showed negative correlation with the length of the lower extremitie sin both sexes. This result indicates that the longer legs they have, the faster they run. The correlation coefficient reveals high negative value in the case of boys(-0.400 in 13, -0.469 in 14 and -0.406 in 15 years of age), but low negative value(-0.133 in 13, -0.190 in 14 and -0.040 in 15 years of age) in the case of girls. In boys, the negative correlation coefficient decreases greatly in 15 years of age(-0.469 in 14, -0.406 in 15 years of age). The result of boys suggests that the correlation coefficient is affected by the muscular development of the lower extremities. Average running records of 100 meter course were 15.48 sec. in boys of 15, and 17.54 sec. in ,girls of 15 years of age. (15 years of age correspond to the standard age of the candidates for an entrance examination of high school). In the case of boys, the running record belongs to middle class on the relative evaluation table of physical examination which was made by the Ministry of Education in 1980, but in the case of girls, their running record belongs to lower class on the table. The most important facts are that the running speed generally becomes faster by 1 sec. for each 8cm increase in the length of lower extremites, and even in the case of the same length of lower extremities, the running speed becomes faster by 1 sec. for each one year increase in age, ranging from 13 to 15 years of age(Table 2 and 3). 2. Standing-Broad-jump ability showed high positive correlation coefficient with the length of the lower extremities in boys(0.427 in 13, 0.474 in 14, 0.373 in 15 years of age). In boys, the positive correlation coefficient decreases greatly in 15 years of age. Thus, the result of boys suggests that as the muscular development becomes active with age, so does the muscular power affect the correlation coefficient. Even in the case of the same length of lower extremities, the Standing-Broad-jumping records are becoming higher with age, Thus, the result suggests that the muscular development becomes active with age. The positive values of correlation coefficients of boys are higher, compared with that of girls of the same age. Average Standing-Broad-jumping records were 223,66cm in boys, and 182.89cm in girls of 13 years of age. These records belong to middle level on the relative evaluation table of physical examination made by the Ministry of Education in 1980. 3. The length of the upper extremities showed positive correlation coefficient (0.391 in 13, 0.483 in. 14 and 0.625 in 15 years of age in boys, and 0.228 in 13, 0.251 in 14 and 0.208 in 15 years of age in girls) with Ball-Throwing distance of boys and girls, In this case a hard ball weighing 162.25 gram was used in the Ball-Throwing record examination. The significantly higher positive values of the correlation coefficient in boys, as compared with girls show that muscular development greatly affects the Ball-Throwing records in boys. Average Ball-Throwing records were 41.97 meters in boys of 15 and 19.42 meters in girls of 15 years of age, which is standard age of candidates for high school entrance examination. The record in boys belongs to middle class on the relative evaluation made by the Ministry of Education in 1980, But the record in girls belongs to low class of the table. 4. In three items of the athletic record examination mentioned above, boys showed 1.1-1.2 times higher record in running, but more than 2 times higher record in Ball-Throwing than girls. These results may suggest that muscular development of the upper extemities in boys is very active, but the development in girls is feeble, 5. The length of the upper extremities showed very low grade of positive correlation coefficient in. boys but the interesting fact is that the average Chin-Up record (8.26 times) in 15 years of age, increases almost 2 times compared with the record (4.49 times) of 14 years of age, Thus, the result suggests that muscular development of upper extremities is very significant in 15 years of age. 6. The length of the upper extremities showed very low grade correlation coefficient with dangling hour in girls. But average dangling record (12.45 sec.) of girls increases suddenly in 15 years of age compared with the record (8.34 sec.) of 14 years of age. (Table 9) This fact also suggests that the muscular development of upper extremities becomes significant in 15 years of age even in the case of girls. The average Arm-Flexing ability (Chin-Up in boys, and dangling on Arm-Flexing power in girls) belongs to middle class of the relative evaluation table (Table 8 and 9) of physical examination made by the Ministry of Education in 1980 in the case of boys, and belongs to lower class of the table in the case of girls. 7. Summarizing the athletic records mentioned above: The correlation between the running ability and the length of the lower extremities was negative value in boys and girls. The correlation coefficient of Standing-Broad-jump was greatly positive. The correlation between the length of upper extremities and Arm-Flexing ability (Chin-Up in boys, and Dangling in girls) showed very low positive correlation coefficient. I would like to advise to moderate the physical evaluation table made by the Ministry of Education in 1980 by lowering the record standard, since the athletic records obtained by the author in five items above-mentioned generally belong to low class, or very low class in girls, especially on the table made by the Ministry of Education.

      • KCI우수등재

        복합중공사막 브레이드 지지체의 열처리에 따른 형태 변화

        박홍원,김종훈,우종형,이호영,성빈 한국섬유공학회 2023 한국섬유공학회지 Vol.60 No.3

        The composite hollow fiber membrane is a ultra filtration made by coating apolymer mixture on the surface of the braid, which is a substrate. Compared to a singlemembrane, it has excellent strength, durability and life time. In this study, we tried todevelop a heat treatment method to flatten the surface of the braid used as a fiber supportfor the composite hollow fiber membrane and improve the circularity of the cross section. A heat treatment device capable of controlling temperature and take-up speed wasdevised, and braids were heat treated with various conditions. As a result of comparing surfaceand cross-section images, it was observed that the surface of the specimen treated at220 oC or higher was flattened by heat treatment and the cross-section became closer to acircular shape. And it was found that the lower take-up speed, the larger the diameterchange due to heat shrinkage.

      • KCI등재

        비판적 커뮤니케이션 연구의 기본 접근들 : 이론적 소고

        박홍원 한국지역언론학회 2011 언론과학연구 Vol.11 No.2

        Despite a widespread agreement within the circle of critical communication research upon the basic idea that the capitalist media, as an ideological agent, contribute to the reproduction of the capitalist relations of domination, there have existed radical differences in the ways to explain the ideological roles of the media among different approaches within the circle. Setting the basic approaches in the critical media studies as political economy of the media, structuralist approach, and culturalist approach, this paper examined the distinctive theoretical features of each approach and tensions among those approaches. Even though there began to arose a converging trend among different approaches within critical media studies, a short theoretical review of these three approaches will be of great help for understanding the original theoretical and practical concerns of critical communication research, offering an insight for analyzing the signifying practices of the media and audiences these days. Drawing on the ways in which these three approaches define the ideological role of the media in capitalist societies, we can expand our knowledge on the role of the media in capitalist domination in the current digital era. 비판적 커뮤니케이션 연구 진영 내에서는 미디어가 이데올로기적 기구로서 자본주의적 지배관계를 재생산하는 데 기여한다는 기본적인 생각은 공유해왔지만, 미디어가 수행하는 이데올로기적 역할에 대한 설명은 동일하지 않다. 이 글에서는 비판적 미디어 연구 전통 내부의 다양한 이론적 입장을 미디어 정치경제학, 구조주의적 접근, 문화주의적 접근으로 설정하고 각 접근의 특징과 이들 사이의 이론적 긴장을 살펴보고 그 의미를 논의했다. 근래에 들어 이들 사이에 이론적 접목과 수렴이 이루어지고 있는 것이 사실이지만 기본접근들을 이렇게 세 가지로 구분해서 살펴보는 것은 비판적 커뮤니케이션 연구가 추구해온 원초적인 이론적 지향점들을 이해하는 데 많은 도움을 줄 수 있다. 초기 비판적 미디어 연구에서 중요한 이론적 방향을 제시했던 이들 세 접근이 자본주의 사회에서 미디어가 수행하는 이데올로기적 역할을 어떻게 규정했는지를 알아보는 것은 미디어 지형에서 상당한 변화를 겪은 오늘날에도 여전히 많은 함의를 갖기 때문이다.

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