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41.
J.?MajzlanEmail author R.?Stevens J.?Boerio-Goates B. F.?Woodfield A.?Navrotsky P. C.?Burns M. K.?Crawford T. G.?Amos 《Physics and Chemistry of Minerals》2004,31(8):518-531
Crystals of hydronium jarosite were synthesized by hydrothermal treatment of Fe(III)–SO4 solutions. Single-crystal XRD refinement with R1=0.0232 for the unique observed reflections (|Fo| > 4F) and wR2=0.0451 for all data gave a=7.3559(8) Å, c=17.019(3) Å, Vo=160.11(4) cm3, and fractional positions for all atoms except the H in the H3O groups. The chemical composition of this sample is described by the formula (H3O)0.91Fe2.91(SO4)2[(OH)5.64(H2O)0.18]. The enthalpy of formation (Hof) is –3694.5 ± 4.6 kJ mol–1, calculated from acid (5.0 N HCl) solution calorimetry data for hydronium jarosite, -FeOOH, MgO, H2O, and -MgSO4. The entropy at standard temperature and pressure (So) is 438.9±0.7 J mol–1 K–1, calculated from adiabatic and semi-adiabatic calorimetry data. The heat capacity (Cp) data between 273 and 400 K were fitted to a Maier-Kelley polynomial Cp(T in K)=280.6 + 0.6149T–3199700T–2. The Gibbs free energy of formation is –3162.2 ± 4.6 kJ mol–1. Speciation and activity calculations for Fe(III)–SO4 solutions show that these new thermodynamic data reproduce the results of solubility experiments with hydronium jarosite. A spin-glass freezing transition was manifested as a broad anomaly in the Cp data, and as a broad maximum in the zero-field-cooled magnetic susceptibility data at 16.5 K. Another anomaly in Cp, below 0.7 K, has been tentatively attributed to spin cluster tunneling. A set of thermodynamic values for an ideal composition end member (H3O)Fe3(SO4)2(OH)6 was estimated: Gof= –3226.4 ± 4.6 kJ mol–1, Hof=–3770.2 ± 4.6 kJ mol–1, So=448.2 ± 0.7 J mol–1 K–1, Cp (T in K)=287.2 + 0.6281T–3286000T–2 (between 273 and 400 K). 相似文献
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The large Area Detectors (LADs) of the BATSE experiment aboard the Compton Gamma-ray Observatory have been used recently as the first hard X-ray all-sky imager at energies between 20 keV and 300 keV. The Earth occultation process is formulated in terms of a curved Radon transform convoluted by a step transform in a selected field of view (FOV) ranging from 5°×5° to 40°×40°. The Maximum Entropy Method is then used to reconstruct an image in the hard X-ray sky. Multiple images of different regions of the sky can be produced simultaneously. A source location accuracy of 0.1° for strong sources and a sensitivity limit of 100 mCrab have been achieved in an one-day integration period.Invited Paper on Imaging in High Energy Astronomy, Sept., 1994, Capri, Italyalso Universities Space Research Association 相似文献
44.
熵的原理与地震活动研究 总被引:3,自引:2,他引:3
熵是多种学科的一个重要交叉点。熵的原理广泛适用于物理、化学、生物、医学、气象乃至社会经济等科学领域,并已取得了令人注目的成果。本文以熵的基本含意出发,简要地阐述了熵概念的扩展,包括热温熵、信息熵以及条件熵等。将地震孕育过程作为一个复杂的开放系统,基于耗散结构理论的基本思想,为定量描述地震活动时、空、强分布的有序度,引入地震活动熵作为序参量,并将其应用于大地震前后地震活动演变特征的研究。初步结果表明,随着临近大地震的发生,在一定范围内地震活动熵值减小,即地震活动分布状态从无序趋向有序。可以预期,把熵的原理引入地震研究领域必将加深人们对地震发生物理过程本质的认识。同时也将为探索地震预测提供新的思路和新的途径。 相似文献
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Size and Fourier-shape characteristics of quartz sand grains were determined by computerized image analysis in order to distinguish between aeolian and fluvial soil parent materials in the Dallol Bosso in Niger. Factor analysis of grain-size distributions gave four sand end-members that can be related to fluvial transport dynamics operating when the sediments were initially deposited. The medium to fine (and more angular shaped) sand fractions are being reworked by wind. Aeolian deposits were well sorted whereas fluvial deposits were poorly sorted in both size and shape. Although gross-shape characteristics (lower harmonics of Fourier series expansion) indicated a common source rock for all sands, the aeolian sands were well rounded whereas the fluvial sands tended to be more angular (upper harmonics of Fourier series). 相似文献
46.
利用最大熵原理推导了连续型随机变量震级熵的表达式,计算了大同-阳高地震前后M≥2.0地震的震级熵,计算结果表明,从1988年4月开始,震级熵开始出现低值异常,1989年3月震级熵开始回升,在回升途中发生了1989年10月18日的大同-阳高6.1级地震。1990年4月份后震级熵再次出现低值异常,9月份后震级熵再次回升,在回升途中发生了1991年3月26日的5.8级地震。 相似文献
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根据Lyapunov稳定理论和耗散结构理论,分析了在均衡力作用下,地壳的均衡调整运动和地壳的反均衡运动的稳定性;推导了判断均衡地壳垂直运动失稳时的熵产生判据和条件;讨论了非线性运动过程中均衡地壳运动系统的反馈性质。作为均衡地壳非稳定性运动的两个实际例子,对青海门源6.4级地震前的重力水准资料和甘肃礼县5.0级地震前的重力水准资料进行了计算,得出了与理论基本一致的结果。 相似文献
50.
The cyclic arrangement of lithofacies of the Karharbari Formation of the Damuda Group from a part of the Talchir Gondwana
basin has been examined by statistical techniques. The lithologies have been condensed into five facies states viz. coarse-,
medium-, fine-grained sandstones, shale and coal for the convenience of statistical analyses. Markov chain analysis indicates
the arrangement of Karharbari lithofacies in form of fining upward cycles. A complete cycle consists of conglomerate or coarse-grained
sandstone at the base sequentially succeeded by medium-and fine-grained sandstones, shale and coal at the top. The entropy
analysis categorizes the Karharbari cycles into the C-type cyclicity, which is essentially a random sequence of lithologic
states. Regression analysis undertaken in the present study indicates the existence of sympathetic relationship between total
thickness of strata (net subsidence) and number and average thickness of sedimentary cycle and antipathic relationship between
number and average thickness of sedimentary cycle. These observations suggest that cyclic sedimentation of the Karharbari
Formation was controlled by autocyclic process by means of lateral migration of streams activated by intrabasinal differential
subsidence, which operated within the depositional basin and the channels carrying coarse grade clastic sediments, which make
the cycles thicker, tend to be more common in the areas of maximum subsidence. Clastic sediments issued from the laterally
migrating rivers interrupted the cyclic sedimentation of the Karharbari Formation in many instances. 相似文献