High-speed, multicolour optical photometry of the anomalous X-ray pulsar 4U 0142+61 with ULTRACAM   总被引：1，自引：0，他引：1  

V. S. Dhillon  T. R. Marsh  F. Hulleman  M. H. van Kerkwijk  A. Shearer  S. P. Littlefair  F. P. Gavriil  V. M. Kaspi 《Monthly notices of the Royal Astronomical Society》2005,363(2):609-614

  相似文献   

On the maximum amplitude and coherence of the kilohertz quasi-periodic oscillations in low-mass X-ray binaries     

Mariano Méndez 《Monthly notices of the Royal Astronomical Society》2006,371(4):1925-1938

I study the behaviour of the maximum rms fractional amplitude, r _max, and the maximum coherence, Q _max, of the kilohertz quasi-periodic oscillations (kHz QPOs) in a dozen low-mass X-ray binaries. I find that (i) the maximum rms amplitudes of the lower- and upper-kHz QPOs,   r ^ℓ_max  and   r ^u_max  , respectively, decrease more or less exponentially with increasing luminosity of the source; (ii) the maximum coherence of the lower-kHz QPO,   Q ^ℓ_max  , first increases and then decreases exponentially with luminosity, at a faster rate than both   r ^ℓ_max  and   r ^u_max  ; (iii) the maximum coherence of the upper-kHz QPO,   Q ^u_max  , is more or less independent of luminosity; and (iv) r _max and Q _max show the opposite behaviour with hardness of the source, consistent with the fact that there is a general anticorrelation between luminosity and spectral hardness in these sources. Both r _max and Q _max in the sample of sources, and the rms amplitude and coherence of the kHz QPOs in individual sources show a similar behaviour with hardness. This similarity argues against the interpretation that the drop of coherence and rms amplitude of the lower-kHz QPO at high QPO frequencies in individual sources is a signature of the innermost stable circular orbit around a neutron star. I discuss possible interpretations of these results in terms of the modulation mechanisms that may be responsible for the observed variability.  相似文献   

基于OO4O和Visual C++6.0实现Oracle9i Spatial中空间数据的操作     

汪斌  周晓光  蒋捷  朱建军 《地理信息世界》2006,4(4):59-62

从OracleSpatial9i管理空间数据的优良特性出发,利用Oracle的OLE对象OO4O和VisualC 6.0的集成实现了对Oracle数据库中空间对象的读取和存储,以及空间对象拓扑关系和空间对象的查询,因此对深入研究基于OracleSpatial空间数据的管理方法有一定的指导作用。  相似文献   

氨氮在垂向河床渗滤系统中的环境行为   总被引：1，自引：0，他引：1  

黄瑞华  吴耀国  杨炳超  妙颖 《地球科学与环境学报》2006,28(1):92-95

采用自行设计的室内土柱实验装置,以恒定氨氮质量浓度为18.27 mg/L的氯化铵溶液为淋滤液,模拟氨氮在垂向河床中的渗滤过程,来探讨氨氮在垂向河床渗滤系统中的环境行为,借以了解河床渗滤系统对氮污染的净化机理。研究结果表明:氨氮在河床渗滤过程中分别参与吸附及硝化作用,主要发生在距离河床1~3 cm处;由于这两种作用的影响,该河床渗滤系统对氨氮的去除率达87%。同时还发现,该河床渗滤系统对氨氮的硝化能力有限,可以考虑向污水中补充溶解氧及添加石灰等强化措施来提高硝化能力。  相似文献   

Hydrolysis Activities of the Particle of Agarose-Ce^4＋ Complex for Compounds Containing Phosphodiester or Peptide Bonds     

YU Lina WANG Dongfeng SU Lin LUO Yi SUN Liping XUEChanghu 《中国海洋大学学报(英文版)》2005,4(3):272-275

Hydrolysis activities of PACC （particle of agarose-Ce^4＋ complex, newly made through double emulsification） for compounds containing phosphodiester or peptide bonds were studied. The results showed that PACC could hydrolyze organophosphorous pesticides not only in water but also in vegetable juice or tea extract. Hydrolysis rates of methamidophos, omethoateand chlorpyrifos in water are 32.39%, 27.12% and 46.62% respectively, those of chlorpyrifos and methamidophos in mung sprout juice 38.28% and 35.45% respectively, and that of chlorpyrifos in tea extract 59.76%. Hydrolysis rates of BSA （bovine serum albumin） in water and protein in tea extract by PACC increase by 54.30% and 86.46% respectively as compared with the control.  相似文献   

4C +39.29 – extended emission around a powerful type 2 quasar     

P. Gandhi  A. C. Fabian  C. S. Crawford 《Monthly notices of the Royal Astronomical Society》2006,369(4):1566-1576

  相似文献   

4D产品的空间数据库结构设计     

黄勇奇  赵追  徐幸福 《地球科学与环境学报》2006,28(3):102-105

主要研究了4D产品(DEM、DOM、DRG、DLG)空间数据库结构设计,将4D产品通过空间数据库引擎ArcSDE存储在大型商业关系数据库管理系统Oracle8i中。在Oracle中可以建立不同的关系表来存储一些4D产品。由于采用关系数据库管理空间数据符合OpenGIS规范,这将增加空间数据的互操作性,并能使GIS融入IT技术的主流。  相似文献   

The Equilibrium Range of Wind Wave Spectra： an Explanation Based on White Noise     

DAI Dejun WANG Wei QIAO Fangli YUAN Yeli 《中国海洋大学学报(英文版)》2007,6(4):345-348

Laboratory experiments and field observations show that the equilibrium range of wind wave spectra presents a – 4 power law when it is scaled properly. This feature has been attributed to energy balance in spectral space by many researchers. In this paper we point out that white noise on an oscillation system can also lead to a similar inverse power law in the corresponding displacement spectrum, implying that the – 4 power law for the equilibrium range of wind wave spectra may probably only reflect the randomicity of the wind waves rather than any other dynamical processes in physical space. This explanation may shed light on the mechanism of other physical processes with spectra also showing an inverse power law, such as isotropic turbulence, internal waves, etc.  相似文献   

Halo ejection in distant radio galaxies: jet feedback in massive galaxy formation     

Michael A. Dopita  Michiel Reuland  Wil van Breugel  Wim de Vries  S. A. Stanford  Huub Röttgering  George Miley  Bram Venemans  Hy Spinrad  Steve Dawson  Arjun Dey  Mark Lacy  Daniel Stern  Andrew Bunker 《Astrophysics and Space Science》2007,311(1-3):305-309

We present results from a Keck optical and near IR spectroscopic study of the giant emission line halos of the z>3 High Redshift Radio Galaxies (HiZRGs) 4C 41.17, 4C 60.07 and B2 0902+34. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s⁻¹ and velocity shears consistent with rotation. The inner regions contain shocked, clumpy cocoons of gas closely associated with the radio lobes with disturbed kinematics and expansion velocities and/or velocity dispersions >1000 km s⁻¹. We also find evidence for the ejection of chemically enriched material in 4C 41.17 up to a distance of ∼60 kpc along the radio-axis. We infer that these HiZRGs are undergoing a final jet-induced phase of star formation with the ejection of most of their interstellar medium before evolving to become “red and dead” Elliptical galaxies.  相似文献   

Pc3-4 geomagnetic pulsations at very low latitude in Brazil     

Ademilson Zanandrea  J.M. Da Costa  S.L.G. Dutra  T. Kitamura  H. Tachihara  O. Saotome 《Planetary and Space Science》2004,52(13):1209-1215

In order to investigate Pc3-4 geomagnetic pulsations at very low and equatorial latitudes, L=1.0 to 1.2, we analyzed simultaneous geomagnetic data from Brazilian stations for 26 days during October-November 1994. The multitaper spectral method based on Fourier transform and singular value decomposition was used to obtain pulsation power spectra, polarization parameters and phase. Eighty-one (81) simultaneous highly polarized Pc3-4 events occurring mainly during daytime were selected for the study. The diurnal events showed enhancement in the polarized power density of about 3.2 times for pulsations observed at stations close to the magnetic equator in comparison to the more distant ones. The phase of pulsation observed at stations near the magnetic equator showed a delay of 48-62° in relation to the most distant one. The peculiarities shown by these Pc3-4 pulsations close to the dip equator are attributed to the increase of the ionospheric conductivity and the intensification of the equatorial electrojet during daytime that regulates the propagation of compressional waves generated in the foreshock region and transmitted to the magnetosphere and ionosphere at low latitudes. The source mechanism of these compressional Pc3-4 modes may be the compressional global mode or the trapped fast mode in the plasmasphere driving forced field line oscillations at very low and equatorial latitudes.  相似文献