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131.
YU Wen-fei 《天文研究与技术》2003,(1):12-15
最近对低质量X射线双星中的千赫兹准周期振动的研究表明 ,是辐射压力 ,而不是盘和磁球的相互作用以及处于盘内边界的广义相对论效应在短时标的盘切断机制上起作用。本文给出了一些研究结果及讨论。 相似文献
132.
We constructed a grid of relativistic models for standard high-relative-luminosity accretion α-disks around supermassive Kerr black holes (BHs) and computed X-ray spectra for their hot, effectively optically thin inner parts by taking into account general-relativity effects. They are known to be heated to high (~106–109 K) temperatures and to cool down through the Comptonization of intrinsic thermal radiation. Their spectra are power laws with an exponential cutoff at high energies; i.e., they have the same shape as those observed in active galactic nuclei (AGNs). Fitting the observed X-ray spectra of AGNs with computed spectra allowed us to estimate the fundamental parameters of BHs (their mass and Kerr parameter) and accretion disks (luminosity and inclination to the line of sight) in 28 AGNs. We show that the Kerr parameter for BHs in AGNs is close to unity and that the disk inclination correlates with the Seyfert type of AGN, in accordance with the unification model of activity. The estimated BH masses Mx are compared with the masses Mrev determined by the reverberation mapping technique. For AGNs with luminosities close to the Eddington limit, these masses agree and the model under consideration may be valid for them. For low-relative-luminosity AGNs, the differences in masses increase with decreasing relative luminosity and their X-ray emission cannot be explained by this model. 相似文献
133.
从高铝粉煤灰中提取非晶态SiO2的实验研究 总被引:5,自引:0,他引:5
为了有效提高高铝粉煤灰的Al/Si比,为提取氧化铝奠定基础,研究了用NaOH从高铝粉煤灰中提取非晶态SiO2的最佳工艺条件,并对提硅反应的机理进行了探讨。首先根据高铝粉煤灰的化学与物相组成特点,确立了利用NaOH提取非晶态SiO2的基本技术路线;然后用正交实验法确定了提硅的最佳条件:NaOH的浓度25%,灰碱质量比1∶0.5,反应温度95℃,反应时间4 h。经最佳条件反应之后,SiO2的提取率达到了41.8%,灰中Al2O3的含量由48.5%增加到了57.38%,Al2O3/SiO2质量比由1.29提高到了2.39。 相似文献
134.
135.
Shigehiko Tateno Kei Hirose Nagayoshi Sata Yasuo Ohishi 《Physics of the Earth and Planetary Interiors》2007,160(3-4):319-325
Phase relations in Mg0.5Fe0.5SiO3 and Mg0.25Fe0.75SiO3 were investigated in a pressure range from 72 to 123 GPa on the basis of synchrotron X-ray diffraction measurements in situ at high-pressure and -temperature in a laser-heated diamond-anvil cell (LHDAC). Results demonstrate that Mg0.5Fe0.5SiO3 perovskite is formed as a single phase at 85–108 GPa and 1800–2330 K, indicating a high solubility of FeO in (Mg,Fe)SiO3 perovskite at high pressures. Post-perovskite appears coexisting with perovskite in Mg0.5Fe0.5SiO3 above 106 GPa at 1410 K, the condition very close to the post-perovskite phase transition boundary in pure MgSiO3. The coexistence of perovskite and post-perovskite was observed to 123 GPa. In addition, post-perovskite was formed coexisting with perovskite also in Mg0.25Fe0.75SiO3 bulk composition at 106–123 GPa. In contrast to earlier experimental and theoretical studies, these results show that incorporation of FeO stabilizes perovskite at higher pressures. This could be due to a larger ionic radius of Fe2+ ion, which is incompatible with a small Mg2+ site in the post-perovskite phase. 相似文献
136.
目的: 分析肺炎性假瘤的CT表现.方法: 对32例经手术病理证实的肺炎性假瘤的CT及临床资料进行回顾性分析.结果: 病灶多位于肺胸膜下,广基地与胸膜相连;多呈圆形或类圆形,边缘光滑,直径2-5cm,密度均匀;边缘可见粗长毛刺,棘状突起或浅分叶;可有淋巴结肿大.结论: 全面综合地分析肺炎性假瘤的CT表现特征,结合肺内感染病史,肺炎性假瘤的正确诊断与鉴别诊断是很有帮助. 相似文献
137.
The Early Cretaceous coal deposits of the Khasyn coalfield are intruded by Palaeogene diabase dikes. The coal has vitrinite reflectance values of 2.0–2.5% Ro, and characteristics of normal anthracite at some distance from the dikes, but at direct contact with the dike two morphological coal varieties occur: coal inclusions in the diabase dike and dispersed carbonaceous matter within the dike rock. Both types of coaly matter have properties typical of anthracites: strong anisotropy, altered internal structure and high vitrinite reflectance values ranging from 3.8 to 5.5% Ro. The X-ray diffraction measurements of the interplanar spacing d(002) and the crystallite sizes Lc and La show rather similar values for coal inclusions in the dike and dispersed carbonaceous matter. The additional reflection at 3.37 Å, corresponding to semi-graphite admixture, occurs in the coal and carbonaceous matter inside the dike and is absent in the natural coal outside the dike. 相似文献
138.
Simulating coseismic deformation of quartz in the middle crust and fabric evolution during postseismic stress relaxation — An experimental study 总被引:3,自引:0,他引:3
Claudia A. Trepmann Bernhard Stckhert Dorothe Dorner Rasoul Hamidzadeh Moghadam Martina Küster Klaus Rller 《Tectonophysics》2007,442(1-4):83-104
Non-steady state deformation and annealing experiments on vein quartz are designed to simulate earthquake-driven episodic deformation in the middle crust. Three types of experiments were carried out using a modified Griggs-type solid medium deformation apparatus. All three start with high stress deformation at a temperature of 400 °C and a constant strain rate of 10− 4 s− 1 (type A), some are followed by annealing in the stability field of α-quartz for 14–15 h at zero nominal differential stress and temperatures of 800–1000 °C (type A + B), or by annealing for 15 h at 900 °C and at a residual stress (type A + C).The quartz samples reveal a very high strength > 2 GPa at a few percent of permanent strain. The microstructures after short-term high stress deformation (type A) record localized brittle and plastic deformation. Statisc annealing (type A + B) results in recrystallisation restricted to the highly damaged zones. The new grains aligned in strings and without crystallographic preferred orientation, indicate nucleation and growth. Annealing at non-hydrostatic conditions (type A + C) results in shear zones that also develop from deformation bands or cracks that formed during the preceding high stress deformation. In this case, however, the recrystallised zone is several grain diameters wide, the grains are elongate, and a marked crystallographic preferred orientation indicates flow by dislocation creep with dynamic recrystallisation. Quartz microstructures identical to those produced in type A + B experiments are observed in cores recovered from Long Valley Exploratory Well in the Quaternary Long Valley Caldera, California, with considerable seismic activity.The experiments demonstrate the behaviour of quartz at coseismic loading (type A) and subsequent static annealing (type A + B) or creep at decaying stress (type A + C) in the middle crust. The experimentally produced microfabrics allow to identify similar processes and conditions in exhumed rocks. 相似文献
139.
Victoria M. Kaspi 《Astrophysics and Space Science》2007,308(1-4):1-11
I review recent observational progress on Anomalous X-ray Pulsars, with an emphasis on timing, variability, and spectra. Highlighted
results include the recent timing and flux stabilization of the notoriously unstable AXP 1E 1048.1–5937, the remarkable glitches
seen in two AXPs, and the newly recognized variety of AXP variability types, including outbursts, bursts, flares, and pulse
profile changes. I also discuss recent discoveries regarding AXP spectra, including their surprising hard X-ray and far-infrared
emission, as well as the pulsed radio emission seen in one source. Much has been learned about these enigmatic objects over
the past few years, with the pace of discoveries remaining steady. However additional work on both observational and theoretical
fronts is needed before we have a comprehensive understanding of AXPs and their place in the zoo of manifestations of young
neutron stars.
相似文献
140.
M. C. Weisskopf M. Karovska G. G. Pavlov V. E. Zavlin T. Clarke 《Astrophysics and Space Science》2007,308(1-4):151-160
We present an overview of Chandra X-ray Observatory observations of neutron stars. The outstanding spatial and spectral resolution of this great observatory
have allowed for observations of unprecedented clarity and accuracy. Many of these observations have provided new insights
into neutron star physics. We present an admittedly biased and overly brief review of these observations, highlighting some
new discoveries made possible by the Observatory’s unique capabilities. This includes our analysis of recent multiwavelength
observations of the putative pulsar and its pulsar-wind nebula in the IC443 SNR.
相似文献