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Chen P.,Anhui Normal University | Chen X.,Guangzhou Meteorological Satellite Station | Jin B.,Anhui Normal University | Zhu X.,Anhui Normal University
Procedia Engineering | Year: 2012

Gaussian mixture model is a popular model in background subtraction and efficient equations have been derived to update GMM parameters previously. In order to compute parameters more accurately while maintain constant computing time per frame, we apply online EM algorithm to update the parameters of Gaussian mixture models. To avoid computing the inverse of covariance matrix, we use isotropic matrix and the corresponding incremental EM equations are derived. Experiments demonstrate that online EM algorithm can give more accurate segment result than previous update equations. © 2011 Published by Elsevier Ltd. Source

Qiu J.-X.,Heyuan Polytechnic | Wu X.-Y.,Heyuan Polytechnic | Li J.-Z.,South China University of Technology | Liu G.,South China University of Technology | And 2 more authors.
2010 International Conference on Multimedia Technology, ICMT 2010 | Year: 2010

Based on the results of statistical analysis software SPSS, in this paper, we make a correlation analysis among disturbance of the ionosphere, ground electric variation and thunderstorm activity. We also study the influence from ionosphere and ground electric field on thunderstorm activity of the same day, in one day, two days, three days, five days, seven days and nine days. And From the outcome, we find, considering each factor separately, within 10 days both of the change of nocturnal and diurnal electric field intensities contributes to the variation of thunderstorm current. Comparatively, the activity of ionosphere has a more significant effect on ground electric field with a negative correlation between them. Also, we find an extremely-significant positive correlation between the nocturnal electric field intensity and that of the daytime. And in a multi-factor interplay analysis, there is little evidence suggests the influence from the ionosphere and ground electric field on thunderstorm activity. ©2010 IEEE. Source

Deng B.,South China University of Technology | Huang J.,Guangzhou Meteorological Satellite Station | Liu W.,South China University of Technology | Xu J.,Guangzhou Meteorological Satellite Station | Huang L.,South China University of Technology
Advances in Space Research | Year: 2013

This study presents a statistical analysis of GPS L-band scintillation with data observed from July 2008 to March 2012 at the northern crest of equatorial anomaly stations in Guangzhou and Shenzhen of South China. The variations of the scintillation with local time, season, solar activity and duration of scintillation patches were investigated. The relationship between the scintillation and TEC depletion was also reported. Our results revealed that GPS scintillation occurred from 19:30 LT (pre-midnight) to 03:00 LT (post-midnight). During quiet solar activity years, the scintillation was only observed in pre-midnight hours of equinox months and patches durations were mostly less than 60 min. During high solar activity years, more scintillation occurred in the pre-midnight hours of equinox and winter months; and GPS scintillation started to occur in the post-midnight hours of summer and winter. The duration of scintillation patches extended to 180 min in high solar activity years. Solar activity had a larger effect to strong scintillations (S 4 > 0.6) than to weak scintillations (0.6 ≥ S4 > 0.2). Strong scintillations were accompanied by TEC depletion especially in equinox months. We also discussed the relationship between TEC depletion and plasma bubble. © 2012 COSPAR. Published by Elsevier Ltd. All rights reserved. Source

Deng B.,South China University of Technology | Huang J.,Guangzhou Meteorological Satellite Station | Kong D.,South China University of Technology | Xu J.,Guangzhou Meteorological Satellite Station | And 2 more authors.
Advances in Space Research | Year: 2015

This study investigated the temporal and spatial distributions of TEC depletions with scintillations and ROTI over south China. Data were collected from two GPS receiver stations in south China from 2011 to 2012. Our results revealed that maxima of distribution of TEC depletions were observed in vernal and autumnal equinox months. During pre-midnight hours and in the region of northern crest of equatorial anomaly, deep TEC depletions (approximately 20 TECU) well coincided with the occurrences of intense scintillations (S4 > 0.5) and large ROTI (approximately 2). But around midnight hours or at the outer edge of northern anomaly crest, only shallow TEC depletions (<10 TECU) were recorded with small ROTI (<1) and no scintillation. Our results suggest that the temporal and spatial variability of TEC depletions during equinox months over south China could be considered as a representative of the evolution phase of the plasma bubbles during post-sunset hours. © 2014 COSPAR. Published by Elsevier Ltd. All rights reserved. Source

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