An extensive 4 x 4 MIMO channel measurement is carried out at 6. 0-6. 4 GHz under a typical classroom environment with channel sounder based on vector network analyzer. Both LOS and NLOS scenarios are considered. The ...An extensive 4 x 4 MIMO channel measurement is carried out at 6. 0-6. 4 GHz under a typical classroom environment with channel sounder based on vector network analyzer. Both LOS and NLOS scenarios are considered. The results on path loss, delay spread and spatial correlation are presented. The measurement shows that, for corridor coverage, 2x2 MIMO is more economical than 4x4 MIMO due to high correlation. In order to identify the unique characteristics at the high frequency band, the measured channel parameters at 6. 0-6.4 GHz are compared with those at 2. 45 GHz. The comparison shows that the shortened wavelength of this higher frequency band results in a great difference of channel characteristics. Therefore, our measurement results provide new gnidance for the design and development of the system working on 6. 0-6.4 GHz band.展开更多
The Ms 6.4 earthquake occurred on May 21,2021 in Yangbi County,Dali Prefecture,Yunnan Province,which was the largest earthquake after the 2014 Jinggu Ms 6.6 earthquake,in western Yunnan.After the earthquake,the rapid ...The Ms 6.4 earthquake occurred on May 21,2021 in Yangbi County,Dali Prefecture,Yunnan Province,which was the largest earthquake after the 2014 Jinggu Ms 6.6 earthquake,in western Yunnan.After the earthquake,the rapid field investigation and earthquake relocation reveal that there was no obvious surface rupture and the earthquake did not occur on pre-existing active fault,but on a buried fault on the west side of Weixi–Qiaohou–Weishan fault zone in the eastern boundary of Baoshan sub-block.Significant foreshocks appeared three days before the earthquake.These phenomena aroused scholars'intensive attention.What the physical process and seismogenic mechanism of the Yangbi Ms 6.4 earthquake are revealed by the foreshocks and aftershocks?These scientific questions need to be solved urgently.展开更多
Using the gravity/GNSS data of 318 stations observed in 2020,this paper optimizes the Bouguer and free-air gravity anomalies around the 2021 Yangbi Ms 6.4 Earthquake,inverses the lithospheric density structure of the ...Using the gravity/GNSS data of 318 stations observed in 2020,this paper optimizes the Bouguer and free-air gravity anomalies around the 2021 Yangbi Ms 6.4 Earthquake,inverses the lithospheric density structure of the focal area,and obtains the distribution of isostatic additional force borne by the lithosphere.The results show that the Bouguer gravity anomaly in western Yunnan varies from-120 to-360 m Gal.As a whole the anomalies are large in the north and small in the south,and the value in the source area of the 2021 Yangbi Ms 6.4 Earthquake is about-260 m Gal.Significant lateral differences indicates that the crust around the great earthquake does not belong to a solid and stable tectonic unit.The lithosphere in the source area is basically in equilibrium,indicating that the occurrence of the great event is not relative to the lithospheric equilibrium,but to the differential movement of the crust in the horizontal direction.In addition,we obtain the teleseismic SKS phases of 51 stations.As a whole,the polarization direction of fast wave in western Yunnan is approximately vertical to the maximum gradient change direction of regional Bouguer gravity anomaly that reflects the change of Moho.展开更多
Four ULF (0.01 Hz - 20 Hz) electromagnetic stations had been gradually established and put into service from 2010 to 2011 in Zhaotong area, Yunnan province. Two stations of Qiaojia and Yongshan have been running with ...Four ULF (0.01 Hz - 20 Hz) electromagnetic stations had been gradually established and put into service from 2010 to 2011 in Zhaotong area, Yunnan province. Two stations of Qiaojia and Yongshan have been running with continuous and high quality recordings and free of influence of solar activities, like magnetic storms. In this investigation, daily recordings from 1 January 2020 to 22 May 2021 have been examined of these both stations. The results show that weak anomalous signals appeared at the beginning of March 2021 with relative low magnitudes of 0.6 nT at Qiaojia station and 0.3 nT at Yongshan station. At the end of this month, the emissions gained an abrupt increase and the amplitudes reached up to 3.8 nT at Qiaojia station and 1.2 nT at Yongsha station. Then, the amplitude decreased to be 0.5 - 1.5 nT and 0.6 - 1.3 nT respectively at both stations but with a high variation frequency in all components. This situation lasted till the Yangbi </span><i><span style="font-family:Verdana;">M</span></i><sub><span style="font-family:Verdana;">S</span></sub><span style="font-family:Verdana;"> 6.4 earthquake happened on May 21, 2021, more than 300 km away from these two ULF observing stations. Totally, the ULF magnetic emissions had been characterized by a synchronous variation in all components at two observing stations.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.61371101)the Shenzhen Biological,Internet,New Energy and New Materials Industry Development Project(Grant No.JC201104210030A)+2 种基金the Science and Technology Basic Research Project of Shenzhen(Grant No.JC200903120174A)the Research Innovation Fund Project of HIT(Grant No.HIT.NSFIR.2010133)the WINDOW-Towards Pervasive Indoor Wireless Networks,and the European Commission under its 7th Framework Program(Grant No.318992)
文摘An extensive 4 x 4 MIMO channel measurement is carried out at 6. 0-6. 4 GHz under a typical classroom environment with channel sounder based on vector network analyzer. Both LOS and NLOS scenarios are considered. The results on path loss, delay spread and spatial correlation are presented. The measurement shows that, for corridor coverage, 2x2 MIMO is more economical than 4x4 MIMO due to high correlation. In order to identify the unique characteristics at the high frequency band, the measured channel parameters at 6. 0-6.4 GHz are compared with those at 2. 45 GHz. The comparison shows that the shortened wavelength of this higher frequency band results in a great difference of channel characteristics. Therefore, our measurement results provide new gnidance for the design and development of the system working on 6. 0-6.4 GHz band.
文摘The Ms 6.4 earthquake occurred on May 21,2021 in Yangbi County,Dali Prefecture,Yunnan Province,which was the largest earthquake after the 2014 Jinggu Ms 6.6 earthquake,in western Yunnan.After the earthquake,the rapid field investigation and earthquake relocation reveal that there was no obvious surface rupture and the earthquake did not occur on pre-existing active fault,but on a buried fault on the west side of Weixi–Qiaohou–Weishan fault zone in the eastern boundary of Baoshan sub-block.Significant foreshocks appeared three days before the earthquake.These phenomena aroused scholars'intensive attention.What the physical process and seismogenic mechanism of the Yangbi Ms 6.4 earthquake are revealed by the foreshocks and aftershocks?These scientific questions need to be solved urgently.
基金financially supported by the National Natural Science Foundation of China (Nos.42274008,U1839208)the National Key R&D Program of China (No.2018YFC1503704)。
文摘Using the gravity/GNSS data of 318 stations observed in 2020,this paper optimizes the Bouguer and free-air gravity anomalies around the 2021 Yangbi Ms 6.4 Earthquake,inverses the lithospheric density structure of the focal area,and obtains the distribution of isostatic additional force borne by the lithosphere.The results show that the Bouguer gravity anomaly in western Yunnan varies from-120 to-360 m Gal.As a whole the anomalies are large in the north and small in the south,and the value in the source area of the 2021 Yangbi Ms 6.4 Earthquake is about-260 m Gal.Significant lateral differences indicates that the crust around the great earthquake does not belong to a solid and stable tectonic unit.The lithosphere in the source area is basically in equilibrium,indicating that the occurrence of the great event is not relative to the lithospheric equilibrium,but to the differential movement of the crust in the horizontal direction.In addition,we obtain the teleseismic SKS phases of 51 stations.As a whole,the polarization direction of fast wave in western Yunnan is approximately vertical to the maximum gradient change direction of regional Bouguer gravity anomaly that reflects the change of Moho.
文摘Four ULF (0.01 Hz - 20 Hz) electromagnetic stations had been gradually established and put into service from 2010 to 2011 in Zhaotong area, Yunnan province. Two stations of Qiaojia and Yongshan have been running with continuous and high quality recordings and free of influence of solar activities, like magnetic storms. In this investigation, daily recordings from 1 January 2020 to 22 May 2021 have been examined of these both stations. The results show that weak anomalous signals appeared at the beginning of March 2021 with relative low magnitudes of 0.6 nT at Qiaojia station and 0.3 nT at Yongshan station. At the end of this month, the emissions gained an abrupt increase and the amplitudes reached up to 3.8 nT at Qiaojia station and 1.2 nT at Yongsha station. Then, the amplitude decreased to be 0.5 - 1.5 nT and 0.6 - 1.3 nT respectively at both stations but with a high variation frequency in all components. This situation lasted till the Yangbi </span><i><span style="font-family:Verdana;">M</span></i><sub><span style="font-family:Verdana;">S</span></sub><span style="font-family:Verdana;"> 6.4 earthquake happened on May 21, 2021, more than 300 km away from these two ULF observing stations. Totally, the ULF magnetic emissions had been characterized by a synchronous variation in all components at two observing stations.
