T_(63)500hPa高度场的预报统计检验与分析     

《贵州气象》1998,(2)

该文将T63500hPa高度切48小时、96小时预报场与客观分析和欧洲中心500hPa高度场,48小时、96小时预报场进行仔细的统计检验。分析结果认为,T63500hPa高度场对我省具有相当高的预报价值,超过了欧洲中心数值产品.  相似文献   

Populations of Bright X-ray Sources in the Starburst Galaxies NGC 4038/4039     

Xi-Wei Liu Xiang-Dong Li 《中国天文和天体物理学报》2007,7(3):389-396

Assuming a naive star formation history, we construct synthetic X-ray source pop- ulations, using a population synthesis code, for comparison with the observed X-ray lumi- nosity function (XLF) of the interacting galaxies NGC 4038/4039. We have included high- and intermediate-mass X-ray binaries, young rotation-powered pulsars and fallback disk-fed black holes in modeling the bright X-ray sources detected. We find that the majority of the X-ray sources are likely to be intermediate-mass X-ray binaries, but for typical binary evolu- tion parameters, the predicted XLF seems to be steeper than observed. We note that the shape of the XLFs depends critically on the existence of XLF break for young populations, and suggest super-Eddington accretion luminosities or the existence of intermediate-mass black holes to account for the high luminosity end and the slope of the XLF in NGC 4038/4039.  相似文献   

Seven-frequency VLBI Observations of the GHz-Peaked-Spectrum Source OQ 208     

Wen-Feng Luo Jun Yang Lang Cui Xiang Liu Zhi-Qiang Shen 《中国天文和天体物理学报》2007,7(5):611-619

We present quasi-simultaneous VLBI images of the GHz-Peaked-Spectrum radio source OQ 208 obtained with the Very Long Baseline Array at 1.4,1.7,2.3,5.0,8.4,15.4GHz and the European VLBI Network at 6.7 GHz.The low frequency(1.4,1.7 and 2.3GHz)ob- servations reveal a weak and extended steep-spectrum component at about 30mas away at position angle-110°,which may be a remnant emission.The radio structure of OQ 208 con- sists of two mini-lobes at 5.0,6.7,8.4 and 15.4 GHz.Our spectral analysis further confirms that the southwest lobe undergoes free-free absorption and finds that the free-free absorption is stronger in the inner region.By fitting the 8.4 GHz images from 1994 to 2005,we obtain a separation speed of 0.031±0.006 mas yr~(-1)between the two mini-lobes.This indicates a jet proper motion of 0.105±0.020 c and a kinematic age of 219±42 yr for the radio source.  相似文献   

应用灰色系统GM（1，1）模型预测各种类型草场的产草量研究     

《内蒙古气象》1990,(2):27-29

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A New Feature Vector Using Selected Line Spectra for Pulsar Signal Bispectrum Characteristic Analysis and Recognition   总被引：1，自引：0，他引：1  

Zhen-Hua Xie Lu-Ping XU Guang-Ren Ni Yan Wang 《中国天文和天体物理学报》2007,7(4):565-571

Average pulse profiles of pulsar signals are analyzed using the bispectrum tech-nique. The result shows that there are nonlinear phase couplings between the two frequency axes of the bispectrum charts, which indicate nonlinear factors in the generation and prop-agation of pulsar signals. Bispectra can be used as feature vectors of pulsar signals because of their being translation invariant. A one-dimension selected line spectrum algorithm for ex-tracting pulsar signal characteristic is proposed. Compared with selected bispectra, the pro-posed selected line spectra have the maximum interclass separability measurements from the point of view of the whole one-dimension feature vector. Recognition experiments on several pulsar signals received at several frequency bands are carried out. The result shows that the selected line spectrum algorithm is suitable for extracting pulsar signal characteristics and has a good classification performance.  相似文献   

FPGA在时间测量中的应用     

朱威  郭唐永  李祝莲 《大地测量与地球动力学》2007,27(Z1):96-100

利用现场可编程门阵列(FPGA)的内部资源，在FPGA中实现了高精度时间间隔测量系统的设计。  相似文献   

CO Clouds around SNR G21.8-0.6 and G32.8-0.1     

Jian-Jun Zhou Xi-Zheng Zhang Hong-Bo Zhang Jarken Esimbek Ju-Yong Zhang Bing-Gang Ju 《中国天文和天体物理学报》2007,7(5):705-711

We made the first CO(I—0) mapping to SNR G21.8-0.6 and SNR G32.8-0.1, both associated with OH 1720 MHz maser.Based on the morphological correspondence and velocity and position agreement between the radio remnant and the CO clouds,we tentatively identify the clouds that are respectively interacting with the two SNRs.  相似文献   

OFDM基带处理系统的设计与实现     

王浩 《大地测量与地球动力学》2007,27(Z1):140-142

阐述了适合高速无线数据传输的正交频分复用(OFDM)调制方式的基本原理及调制解调的快速傅立叶变换(FFT)实现,并给出OFDM基带处理系统的结构图和硬件模块框图。  相似文献   

多频带-正交频分复用超宽带系统的研究与仿真   总被引：2，自引：0，他引：2  

邹小龙  卢晓春  李孝辉  徐劲松  邹德财 《时间频率学报》2007,30(2):89-96

简要阐述了多频带-正交频分复用(MB-OFDM)超宽带系统的基本原理及信号格式,具体分析了相应的发射机与接收机的基本组成与工作原理。在此基础上,利用SystemView仿真平台对发射机、接收机以及信道进行了仿真设计,并互连成一个MB-OFDM超宽带系统。最后,分别给出了功率谱密度、子频带切换以及发射端与接收端信号比较结果,通过对仿真结果的分析证明了整个系统的正确性与可靠性。  相似文献   

河外天体喷流的观测研究——Ⅰ.3C120核心区域的一次快速增亮     

孙凯  张文元  李治平 《中国天文和天体物理学报》1990,(4)

运用云南天文台1米反光望远镜及其附设CCD装置在1988年1月23日及24日对3C120进行了I和R波段观测。采用Starlink系统中的ASPIC软件系统作资料处理。结果表明:我们观测到了一次3C120核心区域中的快速增亮现象。平均增亮速度快于约-0.7~m/日。在这一快速增亮的早期,围绕3C120的核心区域有短的亮射线出现。从1988年1月24日的3C120Ⅰ波段像上发现,可能有一个从核心区域向南的新的突出物。  相似文献