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- 저자 : 김성환 ( Seong Hwan Kim ) (검색결과 527 건)
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김성환,임정현,박나형,문창종,박수현,강성수,배춘식,김성호,신동호,김종춘,Kim, Sung-Hwan,Lim, Jeong-Hyeon,Park, Na-Hyeong,Moon, Changjong,Park, Soo-Hyun,Kang, Seong-Soo,Bae, Chun-Sik,Kim, Sung-Ho,Shin, Dong-Ho,Kim, Jong-Choon 대한수의학회 2010 대한수의학회지 Vol.50 No.2
This study investigated the potential effects of amitraz on the pre- and postnatal development, behavior, and reproductive performance of offspring of parent rats given amitraz during pre-mating, gestation, and lactation. The test chemical was administered via the drinking water containing 0, 40, 120, and 360 ppm to male rats from 2 weeks before mating to the end of 14-day mating period and to females from 2 weeks before mating, throughout mating, gestation and lactation up to weaning. Based on fluid consumption, the male rats received an average of $0,\;5.7{\pm}1.33,\;13.2{\pm}2.08,$ and $35.8{\pm}3.42$ mg/kg/day amitraz, and the female rats received an average of $0,8.7{\pm}4.42,\;20.1{\pm}9.60,\;and\;47.6{\pm}22.38$ mg/kg/day amitraz, respectively. At 360 ppm, an increase in the incidence of abnormal clinical signs, a suppression in the body weight gain, a decrease in the food consumption and litter size, an increase in the post-implantation loss, and a decrease in the seminal vesicle weight were observed in the parent animals. In addition, a suppression in the body weight gain, a decrease in the grip strength, a delay in the negative geotaxis, an increase in the pre- and post-implantation loss, and a decrease in the number of live embryos were observed in the offspring. At 120 ppm, suppressed body weight gain and reduced food consumption were observed in the parent rats. Suppressed body weight gain and decreased grip strength were also observed in the offspring. There were no signs of either reproductive or developmental toxicity at 40 ppm. Under these experimental conditions, the no-observed-adverse-effect level of amitraz for parent rats and their offspring was estimated to be 40 ppm in rats.
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김성환,반태원,이웅섭,류종열,Kim, Seong Hwan,Ban, Tae-Won,Lee, Wongsup,Ryu, Jong Yeol 한국정보통신학회 2017 한국정보통신학회논문지 Vol.21 No.4
We propose a pilot hopping scheme that improves the limited system capacity due to pilot contamination in multi-cell environment with large-scale antenna arrays at a base station, assuming the infinite number of antennas. In the conventional fixed pilot scheme, each user obtains the same signal-to-interference ratio (SIR) over a long period of time. Therefore, a user with strong interference has continuously low SIR which degrades its service quality. In the proposed pilot hopping scheme, different pilot signals are used for each time slot, and different amounts of interference are received every time. When such a pilot hopping technique is applied, the SIR fluctuates at every time slot. When the Hybrid Automatic Repeat & reQuest (HARQ) technique is applied in such a channel, the outage probability and transmission rate are improved. We show that there is the performance gain of the proposed scheme over the conventional scheme through computer simulations.
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다수 사용자를 지원하는 상향링크 밀리미터 파 시스템을 위한 아날로그-디지털 빔포밍의 성능 평가
김성환,Kim, Seong Hwan 한국정보통신학회 2017 한국정보통신학회논문지 Vol.21 No.1
This paper considers hybrid beamforming for millimeter wave system in uplink transmission where multiple users send their data streams simultaneously. Hybrid beamforming has low-cost and low power consumption features compared to conventional digital beamforming schemes. We assume that each user uses one transmit antenna and sends one data stream, while the base station has multiple receive antennas and multiple radio frequency chains. Therefore, hybrid beamforming is performed only at the base station. We also assume that each user does not know instantaneous channel side information (CSI), while the base station is able to estimate the CSI from all users accurately. Under this channel assumption, the outage probability is not zero. We evaluate the outage probability of the considered hybrid beamforming as a performance metric through computer simulations. We show that the outage probability of hybrid beamforming approaches that of digital beamforming in some cases.
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