现在wifi应用已经很普遍,但目前很多无线设备均依据2.4GHz频段设计,因此在无线信号密集区,会出现2.4GHz公共频段拥堵的现象,降低wifi使用体验。而支持2.4GHz和5GHz双频段的无线设备就能很好地解决频道拥挤的问题，本期《消费电子》为大...现在wifi应用已经很普遍,但目前很多无线设备均依据2.4GHz频段设计,因此在无线信号密集区,会出现2.4GHz公共频段拥堵的现象,降低wifi使用体验。而支持2.4GHz和5GHz双频段的无线设备就能很好地解决频道拥挤的问题，本期《消费电子》为大家带来了韩国销量第一的双频路由器TOTO Link A2004NS。展开更多
A Novel Estimation Technique using K-order Models to Evaluate the Maximum Electric Field of Multiple-antenna Transmitters摘要:为了更精确的计算多天线发射机辐射的最大电场,文章提出了一种新型的基于K阶模型的估算方法。首先...A Novel Estimation Technique using K-order Models to Evaluate the Maximum Electric Field of Multiple-antenna Transmitters摘要:为了更精确的计算多天线发射机辐射的最大电场,文章提出了一种新型的基于K阶模型的估算方法。首先提出并讨论K阶估算方法的基本概念和详细的电场方程,建立多发射天线辐射电场的K阶模型,并利用该模型进行估算,以减小天线数量增加所带来的误差。然后,通过若干实验验证所提的估算方法的性能和有效性。例如,在评估一个普通房间中的双偶极子天线辐射的最大电场时,使用传统估算方法,最大误差高达8.5%。展开更多
The first Chinese microwave ocean environment satellite HY-2A was launched successfully in August, 201 I. This study presents a quality assessment of HY-2A scatterometer （HYSCAT） data based on comparison with ocean ...The first Chinese microwave ocean environment satellite HY-2A was launched successfully in August, 201 I. This study presents a quality assessment of HY-2A scatterometer （HYSCAT） data based on comparison with ocean buoy data, the Advanced Scatterometer （ASCAT） data, and numerical model data from the National Centers for Environmental Prediction （NCEP）. The in-situ observations include those from buoy arrays operated by the National Data Buoy Center （NDBC） and Tropical Atmosphere Ocean （TAO） project. Only buoys located offshore and in deep water were analyzed. The temporal and spatial collocation windows between HYSCAT data and buoy observations were 30 min and 25 km, respectively. The comparisons showed that the wind speeds and directions observed by HYSCAT agree well with the buoy data. The root-mean-squared errors （RMSEs） of wind speed and direction for the HYSCAT standard wind products are 1.90 m/s and 22.80°, respectively. For the HYSCAT-ASCAT comparison, the temporal and spatial differences were limited to 1 h and 25 km, respectively. This comparison yielded RMSEs of 1.68 m/s for wind speed and 19.1° for wind direction. We also compared HYSCAT winds with reanalysis data from NCEP. The results show that the RMSEs of wind speed and direction are 2.6 m/s and 26°, respectively. The global distribution of wind speed residuals （HYSCAT-NCEP） is also presented here for evaluation of the HYSCAT-retrieved wind field globally. Considering the large temporal and spatial differences of the collocated data, it is concluded that the HYSCAT-retrieved wind speed and direction met the mission requirements, which were 2 rn/s and 20° for wind speeds in the range 2-24 m/s. These encouraging assessment results show that the wind data obtained from HYSCAT will be useful for the scientific community.展开更多
Based upon Fermi 1FGL and EGRET 3EG samples, a sample including 79 blazars （53 FSRQs, 26 BL Lacs） is presented. It is investigated that the correlations between the ratio of EGRET to Fermi blazars g-ray flux densiti...Based upon Fermi 1FGL and EGRET 3EG samples, a sample including 79 blazars （53 FSRQs, 26 BL Lacs） is presented. It is investigated that the correlations between the ratio of EGRET to Fermi blazars g-ray flux densities and the spectral index differ for EGRET to Fermi blazars for three subclasses of high-frequency peaked BL Lacertae objects-HBL, low-frequency peaked BL Lacertae objects-LBL, and flat spectrum radio quasars-FSRQs. There is a consistent relationship between the ratio of the two γ-ray flux densities and the spectral index difference for the three subclasses. It suggests that the spectrum changed with the source brightness in the gamma-ray band. Both the spectral index difference and the correlation slopes follow a continuous sequence from FSRQs to LBLs to HBLs, which is consistent with the noted blazar sequence.展开更多
文摘现在wifi应用已经很普遍,但目前很多无线设备均依据2.4GHz频段设计,因此在无线信号密集区,会出现2.4GHz公共频段拥堵的现象,降低wifi使用体验。而支持2.4GHz和5GHz双频段的无线设备就能很好地解决频道拥挤的问题，本期《消费电子》为大家带来了韩国销量第一的双频路由器TOTO Link A2004NS。
文摘A Novel Estimation Technique using K-order Models to Evaluate the Maximum Electric Field of Multiple-antenna Transmitters摘要:为了更精确的计算多天线发射机辐射的最大电场,文章提出了一种新型的基于K阶模型的估算方法。首先提出并讨论K阶估算方法的基本概念和详细的电场方程,建立多发射天线辐射电场的K阶模型,并利用该模型进行估算,以减小天线数量增加所带来的误差。然后,通过若干实验验证所提的估算方法的性能和有效性。例如,在评估一个普通房间中的双偶极子天线辐射的最大电场时,使用传统估算方法,最大误差高达8.5%。
基金Supported by the National High Technology Research and Development Program of China(863 Program)(No.2013AA09A505)the National Natural Science Foundation of China(No.40906091)the Open Project of School of Marine Sciences,Nanjing University of Information Science and Technology(No.KHYS1304)
文摘The first Chinese microwave ocean environment satellite HY-2A was launched successfully in August, 201 I. This study presents a quality assessment of HY-2A scatterometer （HYSCAT） data based on comparison with ocean buoy data, the Advanced Scatterometer （ASCAT） data, and numerical model data from the National Centers for Environmental Prediction （NCEP）. The in-situ observations include those from buoy arrays operated by the National Data Buoy Center （NDBC） and Tropical Atmosphere Ocean （TAO） project. Only buoys located offshore and in deep water were analyzed. The temporal and spatial collocation windows between HYSCAT data and buoy observations were 30 min and 25 km, respectively. The comparisons showed that the wind speeds and directions observed by HYSCAT agree well with the buoy data. The root-mean-squared errors （RMSEs） of wind speed and direction for the HYSCAT standard wind products are 1.90 m/s and 22.80°, respectively. For the HYSCAT-ASCAT comparison, the temporal and spatial differences were limited to 1 h and 25 km, respectively. This comparison yielded RMSEs of 1.68 m/s for wind speed and 19.1° for wind direction. We also compared HYSCAT winds with reanalysis data from NCEP. The results show that the RMSEs of wind speed and direction are 2.6 m/s and 26°, respectively. The global distribution of wind speed residuals （HYSCAT-NCEP） is also presented here for evaluation of the HYSCAT-retrieved wind field globally. Considering the large temporal and spatial differences of the collocated data, it is concluded that the HYSCAT-retrieved wind speed and direction met the mission requirements, which were 2 rn/s and 20° for wind speeds in the range 2-24 m/s. These encouraging assessment results show that the wind data obtained from HYSCAT will be useful for the scientific community.
基金supported by the National Natural Science Foundation of China(Grant Nos.10633010 and 11173009)the National Basic Research Program of China(Grant No.2007CB 815405)+5 种基金the Bureau of Education of Guangzhou Municipality(Grant No.11 Sui-Jiao-Ke[2009])Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme (GDUPS)(2009)Yangcheng Scholar Funded Scheme(Grant No. 10A027S)Hunan Provincial Natural Science Foundation(Grant No. 10JJ3020)Fund of the 11th Five-year Plan for Key Construction Academic Subject(Optics) of Hunan Province,Research Funding from Hunan University of Arts and Science(Grant No.JJZD201101)the Guangzhou Education Bureau and Guangzhou Science and Technology Bureau
文摘Based upon Fermi 1FGL and EGRET 3EG samples, a sample including 79 blazars （53 FSRQs, 26 BL Lacs） is presented. It is investigated that the correlations between the ratio of EGRET to Fermi blazars g-ray flux densities and the spectral index differ for EGRET to Fermi blazars for three subclasses of high-frequency peaked BL Lacertae objects-HBL, low-frequency peaked BL Lacertae objects-LBL, and flat spectrum radio quasars-FSRQs. There is a consistent relationship between the ratio of the two γ-ray flux densities and the spectral index difference for the three subclasses. It suggests that the spectrum changed with the source brightness in the gamma-ray band. Both the spectral index difference and the correlation slopes follow a continuous sequence from FSRQs to LBLs to HBLs, which is consistent with the noted blazar sequence.
