Rotation and dilation deformation mechanisms for auxetic behaviour in the α-cristobalite tetrahedral framework structure     

A. Alderson  K. E. Evans 《Physics and Chemistry of Minerals》2001,28(10):711-718

 Analytical expressions are derived for the Poisson's ratios associated with a three-dimensional network of regular, corner-sharing tetrahedra in which: (1) the tetrahedra are assumed to be rigid and free to rotate relative to each other; (2) the tetrahedra are assumed to maintain shape and orientation but are free to change size (dilate); (3) tetrahedral rotation and dilation are assumed to act concurrently. The structure has a primitive unit cell containing four tetrahedra and is analogous to the molecular structure of α-cristobalite. Strain-dependent variations in Poisson's ratio are also predicted by the models. For deformation due to tetrahedral rotation the network is found to exhibit negative Poisson's ratios in each of the three principal directions, with the magnitude of the Poisson's ratio being dependent on the angle of rotation of the tetrahedra. The behaviour of the Poisson's ratio is isotropic in the transverse plane, but anisotropic elsewhere. In the dilation model negative Poisson's ratios equal to −1 are observed for uniaxial loading in any of the principal directions, with the value being constant irrespective of tetrahedral size. The model for concurrent tetrahedral rotation and dilation allows positive as well as negative Poisson's ratios, with the values determined by the framework geometry and relative strengths of the two mechanisms. The concurrent model also offers a design route to materials and structures having ultrahigh Young's moduli. Received: 15 February 2000 / Accepted: 1 October 2000  相似文献   

Water-soluble organics in atmospheric particles: A critical review of the literature and application of thermodynamics to identify candidate compounds   总被引：15，自引：0，他引：15  

Pradeep Saxena  Lynn M. Hildemann 《Journal of Atmospheric Chemistry》1996,24(1):57-109

Although organic compounds typically constitute a substantial fraction of the fine particulate matter (PM) in the atmosphere, their molecular composition remains poorly characterized. This is largely because atmospheric particles contain a myriad of diverse organic compounds, not all of which extract in a single solvent or elute through a gas chromatograph; therefore, a substantial portion typically remains unanalyzed. Most often the chemical analysis is performed on a fraction that extracts in organic solvents such as benzene, ether or hexane; consequently, information on the molecular composition of the water-soluble fraction is particularly sparse and incomplete.This paper investigates theoretically the characteristics of the water-soluble fraction by splicing together various strands of information from the literature. We identify specific compounds that are likely to contribute to the water-soluble fraction by juxtaposing observations regarding the extraction characteristics and the molecular composition of atmospheric particulate organics with compound-specific solubility and condensibility for a wide variety of organics. The results show that water-soluble organics, which constitute a substantial fraction of the total organic mass, include C2 to C7 multifunctional compounds (e.g., diacids, polyols, amino acids). The importance of diacids is already recognized; our results provide an impetus for new experiments to establish the atmospheric concentrations and sources of polyols, amino acids and other oxygenated multifunctional compounds.  相似文献   

论异常地层压力在构造研究中的意义          下载免费PDF全文

张家骅 《地球科学》1993,2(5)

本文将异常地层压力、压力系数及平衡深度等概念和构造研究联系起来,着重探讨压力系数在构造发育中的重要意义。  相似文献   

Evolution mechanism of the western Pacific subtropical high   总被引：4，自引：0，他引：4  

曹杰  黄荣辉  谢应齐  陶云 《中国科学D辑(英文版)》2003,46(3):257-268

Ever since Charney et al.[1] studied the multiple equilibrium states in atmosphere with highly truncated spectral method in 1979, many Chinese researchers, such as Li Maicun et al. (1983)[2], Liu Chongjian et al. (1983)[3], Miu Jinhai et al. (1985)[4] and…  相似文献   

The complex refractive index of limestone particles: an extension to the FIR range for Mars applications     

V Orofino  A BlancoS Fonti  A.C MarraN Polimeno 《Planetary and Space Science》2002,50(9):839-847

  相似文献   

Convergence of Liapunov Series for Maclaurin Ellipsoids     

Konstantin V. Kholshevnikov  Andrei V. Elkin 《Celestial Mechanics and Dynamical Astronomy》2002,84(1):57-63

According to the classical theory of equilibrium figures surfaces of equal density, potential and pressure concur (let call them isobars). Isobars may be represented by means of Liapunov power series in small parameter q, up to the first approximation coincident with centrifugal to gravitational force ratio on the equator. A. M. Liapunov has proved the existence of the universal convergence radius q : above mentioned series converge for all bodies if q < q . Using Liapunov's algorithm and symbolic calculus tools we have calculated q = 0.000370916. Evidently, convergence radius q ₀ may be much greater in non-pathological situations. We plan to examine several simplest cases. In the present paper, we find q ₀ for homogeneous liquid. The convergence radius turns out to be unexpectedly large coinciding with the upper boundary value q ₀ = 0.337 for Maclaurin ellipsoids.  相似文献   

天然气水合物体系的相平衡及甲烷溶解度计算          下载免费PDF全文

苏正  陈多福  冯东  刘芊 《地球物理学进展》2007,22(1):239-246

海洋环境中天然气水合物的形成除了合适的温压条件外，还必须有充分的甲烷供给.本文介绍了甲烷-水体系的甲烷饱和溶解度、水合物体系中甲烷水合物溶解度计算方法.在气-液二相平衡甲烷饱和溶解度计算中，关键在于状态方程的选择和合适的混合规则的运用，Duan的计算模型在温度、压力和盐度变化上都具有很大的适用性，且易于应用.在含水合物的相平衡体系中，在已知组分和假定可能存在相的前提下，可利用模拟退火算法优化总吉布斯自由能，确定是二相还是三相体系，并求解甲烷水合物溶解度.在海水环境下盐的存在使平衡发生移动，利用德拜—休克尔理论或Pitzer电解质溶液理论校正盐度对于海水活度的影响，求解海水环境中甲烷水合物溶解度.基于气-液二相平衡理论的K-K方程，在临近水合物生成条件下实验或计算确定亨利常数等参数后，可计算三相平衡甲烷水合物溶解度，且简单易用.  相似文献   

伊利石结晶度Kübler，Weaver和Weber指数关系式常数的确定与应用   总被引：1，自引：0，他引：1  

王河锦  陶晓风Rahn Meinert 《高校地质学报》2007,13(3):561-565

根据衍射峰具有的不同分布特点推导出了14个伊利石结晶度Kübler指数，Weaver指数和Weber指数关系式中常数项C1-C14的数值，提出了PearsonⅦ分布中形态参数μ与C5，C6，C11，C12的4个定量方程。由此，14个伊利石结晶度指数关系式可直接用于实际计算。根据阿尔卑斯复理石伊利石形态特征Sc=0.731，由这些关系式进行近变质带上下界线的转换得出与Kübler指数0.42～0.25。△2θ界线对应的Weaver指数和Weber指数的界线值分别为5.8～17.6和300～179。讨论了在自然干燥状态下直接进行伊蒙混层鉴定的基本原理。  相似文献   

基于TOUGHREACT的成矿过程化学反应数值模拟——以虎头崖铅锌多金属矿床为例          下载免费PDF全文

张婉秋  邹艳红 《地质找矿论丛》2020,35(3):354-362

虎头崖铅锌多金属矿床是青海省祁漫塔格成矿带中典型的矽卡岩型矿床。本文基于前人对该矿区地质特征、矿物学和地球化学特征等方面的研究成果，利用TOUGHREACT数值模拟软件，针对石英-晚期硫化物成矿阶段进行成矿过程化学反应数值模拟研究。通过建立地质概念模型和网格化物化参数的设置，在设置的时间步长内对多相流体流动和热对流传导、溶质运移以及地球化学反应过程进行模拟计算，研究了矿区内不同温压条件下成矿元素化学平衡浓度变化的总体趋势以及对方铅矿和闪锌矿矿物溶解沉淀情况的影响。结果表明：当温度从250℃降至155℃时，Pb²⁺的化学平衡浓度出现骤减；当温度从300℃降至100℃时，Zn²⁺的化学平衡浓度出现骤减；由于矿物的沉淀需要消耗大量相关的成矿元素，方铅矿和闪锌矿最佳成矿温度范围分别为155℃~250℃和100℃~300℃；不同温度和压力对成矿元素化学平衡浓度影响不同，温度是控制方铅矿和闪锌矿沉淀化学反应的核心因素，压力的影响较小。模拟结果与传统地质解译结果相对符合，证明了模拟的有效性。  相似文献   

橄榄岩中尖晶石的氧同位素继承性与晶体结构转变     

李一良  王峥嵘 《地球化学》1998,27(5):442-451

根据激光探针分析含尖晶石橄榄石中矿物的氧同位素组成,反应增量法计算矿物对氧同位素分馏曲线,得到正尖晶石－矿物对氧同位素温度高于含尖晶石橄榄岩的相平衡温度,而用反尖晶石－矿物的对计算的氧同位素温度则很接近含尖晶石橄榄岩的相平衡温度,较为合理,因此地幔橄榄岩中镁铝尖晶石的氧同位素组成继承了其母体反尖晶石特征,即与橄榄石,单斜辉石和斜方辉石平衡的是反结构尖晶石,在其发生相变作用变成正结构尖晶石时未发生氧  相似文献