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Frequency-Dependent UWB Channel Characteristics in Office Environments
Jinwon Choi,Noh-Gyoung Kang,Yu-Suk Sung,Jun-Sung Kang,Seong-Cheol Kim IEEE 2009 IEEE Transactions on Vehicular Technology VT Vol.58 No.7
<P>This paper reports frequency-dependent ultrawideband (UWB) channel characteristics. Measurements were performed in 103 receiver locations of six different office environments. From the measured data, the effect of frequency on the path-loss properties of a UWB signal is analyzed. After analyzing the path-loss behavior to propagation environments, the path-loss exponent variation models are developed in various environments as a function of frequency. Based on these models, path-loss prediction is performed, and the accuracy of the prediction is compared with those of existing path-loss models. In addition, the frequency-dependent UWB channel correlation characteristics are investigated. For the frequency correlation statistics of the UWB channel, double-slope models representing correlation coefficients are established with and without line-of-sight (LOS) paths. Using these correlation models, a channel gain estimation algorithm is proposed. The performance of the proposed estimation algorithm is evaluated with estimation parameters, and it is confirmed that the proposed estimation algorithm has better performance than the conventional algorithm using a linear interpolation algorithm.</P>
양수검사시 천자침의 태반 관통 여부에 따른 임신 경과 비교
노영수(Young Su Noh),김광준(Gwang Jun Kim),이경훈(Gyoung Hun Lee),임성미(Seong Mi Lim),강철규(Cheol Gyu Kang),김석영(Suk Young Kim),박찬용(Chan Yong Park),최유덕(Yu Duk Choi),황병철(Byoung Cheol Whang) 대한산부인과학회 2001 Obstetrics & Gynecology Science Vol.44 No.6
Objective: To evaluate pregnancy outcomes after placental needle penetration during midtrimester diagnostic amniocentesis. Methods: We collected 726 singleton pregnancy cases from 1054 pregnancies of midtrime-ster diagnostic amniocentesis, and analysed pregnancy outcomes after the procedure based on medical records. To compare the outcomes, we divided 726 cases into two groups; placental penetration group by aspiration needle(170 cases) and non-penetration group(556 cases). Results: There were no statistically significant differences between two groups about maternal age and gestational age at the time of procedure, and the distribution of amniocentesis indication, In comparison of complications between two groups after procedure, a. There was no statistically significant difference in amniotic fluid leakage: in penetration group, 1 case (0.58%) and in non-penetration group, 5 cases(0.89%) were observed. b. There was no statistically significant difference in vaginal bleeding: in penetration group, 2 cases !1.18%) and in non-penetration group, 3 cases(0.54%) were observed. c. There was no statistically significant difference in developing abruptio placentae: in penetration group, o case developed and in non-penetration group, one case(0.18%) was observed. d. As for fetal loss, there was no statistically significant difference: in penetration group, 4 cases i'2.35%) and in non-penetration group, 10 cases(1.80%) were occurred. e. As for birth weight, there was no statistically significant difference: in penetration group, 3.26±0.8 kg and in non-penetration group, 3.21±0.9 kg were measured. Conclusion: Our study shows that placental penetration by aspiration needle during diagnostic mid-trimester amniocentesis does not increase the risk of post-procedure complication.
최진원,강노경,김정욱,김성철,Choi Jin-Won,Kang Noh-Gyoung,Kim Jeong-Wook,Kim Seong-Cheol 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.7a
본 논문에는 초광대역 통신시스템을 위한 주파수 영역의 통계학적 채널 모델을 서술하고 있다. 채널 모렐링은 3개의 사무실 환경, 46개의 송, 수신 위치에서 얻어진 23,000개의 채널응답함수로 부터 얻어졌다. 측정실험을 통해 얻어진 데이터를 바탕으로 주파수 변화에 따른 경로감쇄지수 변화에 대해 서술한 후 전파환경과 가시경로의 존재여부에 따른 수신신호의 확률분포모델을 연구하였다. 마지막으로는 수신된 주파수 톤에 해당하는 수신파워의 표준편차와 같은 통계적 특성들을 고찰하였는데, 가시경로가 존재하는 경우에는 송, 수신기 사이의 거리가 멀어지면서 표준편차 값이 커지고 그에 따라 수신 주파수 톤의 파워가 평균 수신파워에서 일정한 범위 안에 들어올 확률이 떨어지는 것을 알 수 있었다.
최병철 ( Byoung Cheol Choi ),강철규 ( Cheol Gyu Kang ),김석영 ( Sug Young Kim ),이경훈 ( Gyoung Hoon Lee ),노영수 ( Young Su Noh ),송경철 ( Kyoung Cheol Song ),엄기남 ( Ki Nam Eom ),임승욱 ( Seung Ug Im ) 대한산부인과학회 2001 Obstetrics & Gynecology Science Vol.44 No.7
Prenatal Ultrasonographic findings of meconium peritonitis show calcificalion, and abdominal echogenic masses such as pseudocyst. Also, we can find availability of 3 dimensional ultrasonography above these descriptions. We present a case of meconium peritonitis in uterus which was diagnosed by means of prenatal 2D & 3D ultrasonography with brief review of literatures.
Ko, Junghoon,Lee, Kyoungtae,Cho, Yeon-Jea,Oh, Sangmin,Hur, Sooyoung,Kang, Noh-Gyoung,Park, Jeongho,Park, Dong-Jo,Cho, Dong-Ho IET 2016 IET COMMUNICATIONS Vol.10 No.17
<P>This study presents analyses of the feasibility for the 28 GHz band with a comprehensive overview of important channel parameters. A channel measurement system with a time synchronisation scheme is also introduced which is a sliding correlator channel sounder using 250 Mcps (Mega-chips-per-second) pseudo-random noise sequences. The system enables the observation of the behaviour of 28 GHz wave propagation not only to use of forming narrow beams in certain directions (classical narrow beam beamforming) but also omni-likely. This novel synchronised system makes it possible to analyse the wideband channel characteristics. The outdoor channel measurements are conducted considering various features such as foliage effects, signal outage, path loss and outdoor-to-indoor conditions. Furthermore, the spatial channel modelling for omni-like observations with temporal characteristics is firstly interpreted through analysing the essential channel modelling parameters, including the number of clusters, excess delay, root-mean-square (RMS) delay spread, power delay spectrum, and angular spread. In the authors' measurements, the average number of clusters was 2.41 with standard deviation of 1.44. The average RMS delay spread was 36.06 ns with standard deviation of 46.73 ns. Furthermore, the mean values of the RMS azimuth spreads of the angle of departure and arrival were 6.65 degrees and 24.04 degrees, respectively.</P>