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Astronomy Reports - Estimates of the physical parameters of the hot spot A of the radio galaxy Cygnus A were obtained from radio astronomical observations. To estimate the physical parameters of... 相似文献
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Eric Robinson 《Geology Today》1999,15(3):110-113
Before the Roman came to Rye or out to Severn strode,
The rolling English drunkard made the rolling English road. 相似文献
The rolling English drunkard made the rolling English road. 相似文献
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通过研究矩阵与其伴随矩阵Ａ＾＊,＾＊Ａ之间的关系,得到了Ａ＾＊,＾＊Ａ较为完整的一系列性质,并给出了Ａ＾＊,＾＊Ａ的一些应用。 相似文献
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《Comptes Rendus Geoscience》2014,346(11-12):275-278
The author contributes to the development of a history of the global understanding of the Earth. He summarizes the main steps in the knowledge of the Earth's interior from antiquity to the present time and draws some lessons from this history. 相似文献
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A series of dynamical models of the Galaxy is constructed assuming that the entire disk is near the gravitational-stability limit. This imposes constraints on the dynamical and kinematic parameters of the main subsystems (the disk, bulge, and halo). The disk surface density in the solar neighborhood should not exceed 58 M⊙/pc2. Further, we find that the observed local decrease in the rotational velocity at 6 kpc ? r ? 10 kpc is not associated with details of the radial distribution of matter in the Galaxy and instead results from dynamical processes or some other factors responsible for noncircular motions. It follows from the presence of a long-lived bar and the observed distribution of the stellar-velocity dispersion that the central maximum in the rotation curve at radius r ? 300 pc cannot be associated with a very concentrated bulge core. The best agreement between the observational data and the parameters of the dynamical models is achieved for a radial disk scale length of L ? 3 kpc. The relative contribution of the disk to the circular rotational velocity at r = 2.2L is 73%. 相似文献
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《Quaternary Science Reviews》2005,24(1-2):1-10
According to a new hypothesis, greenhouse-gas concentrations in the atmosphere should have fallen throughout the last several thousand years and caused a significant cooling of Earth's climate, but early anthropogenic emissions of carbon dioxide and methane kept temperatures relatively warm. A further prediction is that ice should have begun accumulating in northeast Canada several thousand years ago. We carry out a preliminary test of this hypothesis by reducing atmospheric CO2 and CH4 concentrations to their estimated ‘natural’ levels in an experiment with the GENESIS climate model. In the absence of anthropogenic contributions, global climate is almost 2 °C cooler than today and roughly one third of the way toward full-glacial temperatures. The hypothesis of an overdue glaciation is confirmed, but at a small scale: parts of Baffin Island retain snow cover year-round, and snow cover persists on high terrain in Labrador for 11 months of the year. 相似文献
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A re-evaluation of the olivine-spinel geothermometer 总被引：1，自引：0，他引：1
Peter L. Roeder Ian H. Campbell Heather E. Jamieson 《Contributions to Mineralogy and Petrology》1979,68(3):325-334
The Irvine olivine-spinel geothermometer, as formulated by Jackson (1969), appears to yield magmatic temperatures when applied
to plutonic rocks such as the Stillwater Complex but Evans and Wright (1972) have demonstrated that it gives temperatures
in excess of 2,000 ° C when applied to volcanic assemblages. A re-evaluation of the geothermometer has shown that more realistic
temperatures can be obtained for volcanic rocks by using a different free energy value of FeCr2O4 in the formulation. The revised geothermometer gives temperatures in the range 1,100–1,300 ° C for samples from Kilauea and
500–800 ° C for basic plutonic rocks from layered intrusions, indicating that Mg and Fe2+ have re-equilibrated at subsolidus temperatures in these intrusions as suggested by Irvine (1965). This theory was tested
by heating uncrushed natural samples from layered intrusions to magmatic temperatures for periods ranging from two days to
four weeks. The result was a marked increase in the Mg/Fe2+ ratio in the spinels and a decrease in the Mg/Fe2+ ratio in the olivines, confirming that considerable subsolidus re-equilibration had taken place in the unheated samples. 相似文献
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The thermogravimetric measurements on fayalite reported by Nakamura and Schmalzried (1983) have been reassessed using the compound-energy model and computer calculations which eliminate much mathematical manipulation and subjective choice. The calculated phase field for fayalite differs somewhat from the one obtained by Nakamura and Schmalzried (1983) but there is satisfactory agreement in the experimental range. 相似文献
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A Test of the Cyclicity of Earthquakes 总被引：1，自引：0，他引：1
The periodogram analysis of time intervals between successive earthquakes is used for testing the seismic gap hypothesis. Using the available data, it is shown that the existence of a periodic component can be rejected with high confidence. The test provides evidence against quasi-periodicity and regular clustering of the arrival times. 相似文献
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W. T. Chang 《Australian Journal of Earth Sciences》2013,60(1-2):137-150
The sedimentary history and biostratigraphy of China during the Cambrian Period are broadly discussed within the framework of major tectonic divisions of the country. Five platform domains (North China Platform, southwest China Platform, Chiangnan Belt, Tarim Platform, and Tsaidem Platform) and five eugeosynclinal belts (South Tibet‐western Yunnan Belt, Tienshan‐Altai‐Great Khingan Geosyncline, Chilian Geosyncline, Kunlun‐Tibet‐western Yunnan Geosyncline and Southeast China Geosyncline) are recognised and discussed individually. A zonal scheme for Chinese Cambrian biostratigraphy is provided and the problems of the Precambrian to Cambrian, Cambrian to Ordovician and also the series boundaries are discussed. International correlation of the Cambrian of China, especially with Australia, is outlined in some detail. 相似文献
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A subdivision of the Precambrian of China 总被引：1，自引：0，他引：1
Precambrian rocks are widely distributed in China. The Precambrian is divided into two time units, i.e., the Archaean and Proterozoic Eon, each of these is separated into three chronological intervals, also with the status of eras, with the prefixes early, middle or late. The time boundary between the Archaean and Proterozoic Eon is placed at ～ 2500 Ma.According to the present isotopic data, the proposed subdivision for the Archaean of China is two-fold. The age of the Fuping Group is younger than 2800–2900 Ma, and that of the Qianxi Group and the corresponding stratigraphic units of eastern Liaoning are older than 2800 Ma, so that 2800+ Ma is selected as the boundary between the early—middle and late Archaean.Based on the representative stratigraphic units, the Wutai and Huto Groups, and an intervening major unconformity formed by the Wutaiian orogeny at 2200–2300 Ma, the early Proterozoic is further divided into two periods, with a time demarcation at 2200+ Ma. A major episode of orogeny known as the “Luliangian Movement” occurred at the end of the early Proterozoic at ～ 1900 Ma. This disturbance was very extensive and is, in a way, responsible for the difference in geological conditions between the lower and middle—upper Proterozoic in China. The boundary (1900 Ma) that relates to the Luliangian Movement is more important than the boundary corresponding to the age of 1600 Ma, which is recommended as the time boundary between Proterozoic I and II, so we propose to use 1900 Ma as the boundary between the early and middle Proterozoic in China.The time boundary between the middle Proterozoic, including the Changcheng System and the Jixian System, and the late Proterozoic, which is composed of the Qingbaikou and Sinian Systems, is ～ 1000 Ma. The age for the boundary between Cambrian and Precambrian, based upon the recent isochron data, is inferred to be 610 Ma. 相似文献
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The biotite zone assemblage: calcite-quartz-plagioclase (An25)-phengite-paragonite-chlorite-graphite, is developed at the contact between a carbonate and a pelite from British Columbia. Thermochemical data for the equilibrium paragonite+calcite+2 quartz=albite+ anorthite+CO2+H2O yields: $$\log f{\text{H}}_{\text{2}} {\text{O}} + \log f{\text{CO}}_{\text{2}} = 5.76 + 0.117 \times 10^{ - 3} (P - 1)$$ for a temperature of 700°K and a plagioclase composition of An25. By combining this equation with equations describing equilibria between graphite and gas species in the system C-H-O, the following partial pressures: \(P{\text{H}}_2 {\text{O}} = 2572{\text{b, }}P{\text{CO}}_2 = 3162{\text{b, }}P{\text{H}}_2 = 2.5{\text{b, }}P{\text{CH}}_4 = 52.5{\text{b, }}P{\text{CO}} = 11.0{\text{b}}\) are obtained for \(f{\text{O}}_2 = 10^{ - 26}\) . If total pressure equals fluid pressure, then the total pressure during metamorphism was approximately 6 kb. The total fluid pressure calculated is extremely sensitive to the value of \(f{\text{O}}_2\) chosen. 相似文献
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l.IntroductionSinceArgand's(l924)recognitionthattheCenozoictectonicsoftheHighAsiaareprincipallytheresultoftheconvergenceofGondwanancontinentalfragmentswithLaurisic,therehasbeenageneralacceptanceoftheviewthattheHimalayasandQinghai-TibetPlateauhavebeenformedbyacollisionbetweentheIndianandTibetcontinentsalongtheIndus-Zangbosuture(MolnarandTapponnief,l975,Sengor,l979;ChenBingwei,l982;DengWanming,l978,HuangJiqing,l954;LoZhongshu,l982;PanGuitangetal.,l984,WangQianshenetal.,l982,Besseetal.… 相似文献
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基体相在矿物聚合材料结构中起与其他矿物表面键合的作用 ,是材料强度的来源。本实验以富钾岩石提钾后的硅铝质溶胶相加NaOH固体 ,在 6 0℃下制备矿物聚合材料基体相 ,并采用XRD、SEM、IR、NMR等分析手段研究了不同固化时间基体相的结构。研究结果表明 ,在基体相的形成过程中 ,没有新的结晶相产生 ,说明基体相为一种半晶质到非晶质物相 ;随着固化时间的变化 ,其自身 [SiO4]4-四面体发生解聚又重新聚合 ,聚合后基体相形成了致密完整的块体 相似文献