共查询到20条相似文献，搜索用时 46 毫秒
1.
M. K. Abubekerov E. A. Antokhina A. M. Cherepashchuk V. V. Shimanskii 《Astronomy Reports》2006,50(7):544-552
We interpret the observed radial-velocity curve of the optical star in the low-mass X-ray binary 2S 0921-630 using a Roche model, taking into account the X-ray heating of the optical star and screening of X-rays coming from the relativistic object by the accretion disk. Consequences of possible anisotropy of the X-ray radiation are considered. We obtain relations between the masses of the optical and compact (X-ray) components, m v and m x , for orbital inclinations i = 60°, 75°, and 90°. Including X-ray heating enabled us to reduce the compact object’s mass by ～0.5–1 M ⊙, compared to the case with no heating. Based on the K0III spectral type of the optical component (with a probable mass of m v ? 2.9 M ⊙), we concluded that m x ? 2.45?2.55 M ⊙ (for i = 75°?90°). If the K0III star has lost a substantial part of its mass as a result of mass exchange, as in the V404 Cyg and GRS 1905+105 systems, and its mass is m v ? 0.65?0.75 M ⊙, the compact object’s mass is close to the standard mass of a neutron star, m x ? 1.4 M ⊙ (for i = 75°?90°). Thus, it is probable that the X-ray source in the 2S 0921-630 binary is an accreting neutron star. 相似文献
2.
The mass-dependent fractionation laws that describe the partitioning of isotopes are different for kinetic and equilibrium reactions. These laws are characterized by the exponent relating the fractionation factors for two isotope ratios such that α2/1 = α3/1β. The exponent β for equilibrium exchange is (1/m1 − 1/m2)/(1/m1 − 1/m3), where mi are the atomic masses and m1 < m2 < m3. For kinetic fractionation, the masses used to evaluate β depend upon the isotopic species in motion. Reduced masses apply for breaking bonds whereas molecular or atomic masses apply for transport processes. In each case the functional form of the kinetic β is ln(M1/M2)/ln(M1/M3), where Mi are the reduced, molecular, or atomic masses. New high-precision Mg isotope ratio data confirm that the distinct equilibrium and kinetic fractionation laws can be resolved for changes in isotope ratios of only 3‰ per amu. The variability in mass-dependent fractionation laws is sufficient to explain the negative Δ17O of tropospheric O2 relative to rocks and differences in Δ17O between carbonate, hydroxyl, and anhydrous silicate in Martian meteorites. (For simplicity, we use integer amu values for masses when evaluating β throughout this paper.) 相似文献
3.
The kinetic equation for the distribution function of relativistic electrons is solved taking into account quasi-linear interactions with waves and radiative processes. Mean values of the pitch angles ψ are calculated. If the particles of the primary beam with Lorentz factors γb～106 are resonant, then the condition γbψb?1 is satisfied, the particle distribution is described by the function f ‖(γ) ∝ γ?4, and the synchrotron radiation spectrum is characterized by the spectral index α=3/2. On the other hand, if a cyclotron resonance is associated with particles of the high-energy tail of the secondary plasma (γt～105), then γtψt?1, and the distribution function has two parts—f ‖(γ) ∝ γ and f ‖(γ) ∝ γ?2—which correspond to the spectral indices α1=+1 and α2=?0.5. This behavior is similar to that observed for the pulsar B0656+14. The predicted frequency of the maximum νm=7.5×1016 Hz coincides with the peak frequency for this pulsar. The model estimate for the total synchrotron luminosity of a typical radio pulsar with hard radiation L s =3×1033 erg/s is in agreement with observed values. 相似文献
4.
The solubility of ZnS(cr) was measured at 100 °C, 150 bars in sulfide solutions as a function of sulfur concentration (m(Stotal) = 0.02-0.15) and acidity (pHt = 2-11). The experiments were conducted using a Ti flow-through hydrothermal reactor enabling the sampling of large volumes of solutions at experimental conditions, with the subsequent concentration and determination of trace quantities of Zn. Prior to the experiments, a long-term in situ conditioning of the solid phase was performed in order to attain the reproducible Zn concentrations (i.e. solubilities). The ZnS(cr) solubility product was monitored in the course of the experiment. The following species were found to account for Zn speciation in solution: Zn2+ (pHt < 3), (pHt 3-4.5), (pHt 5-8), and ZnS(HS)− (pHt > 8) (pHt predominance regions are given for m(Stotal) = 0.1). Solubility data collected in this study at pHt > 3 were combined with the ZnS(cr) solubility product determined at lower pH to yield the following equilibrium constants (t = 100 °C, P = 150 bars):
5.
Water is an important volatile component in andesitic eruptions and deep-seated andesitic magma chambers. We report an investigation of H2O speciation and diffusion by dehydrating haploandesitic melts containing ?2.5 wt.% water at 743-873 K and 100 MPa in cold-seal pressure vessels. FTIR microspectroscopy was utilized to measure species [molecular H2O (H2Om) and hydroxyl group (OH)] and total H2O (H2Ot) concentration profiles on the quenched glasses from the dehydration experiments. The equilibrium constant of the H2O speciation reaction H2Om+O?2OH, K = (XOH)2/(XH2OmXO) where X means mole fraction on a single oxygen basis, in this Fe-free andesite varies with temperature as ln K = 1.547-2453/T where T is in K. Comparison with previous speciation data on rhyolitic and dacitic melts indicates that, for a given water concentration, Fe-free andesitic melt contains more hydroxyl groups. Water diffusivity at the experimental conditions increases rapidly with H2O concentration, contrary to previous H2O diffusion data in an andesitic melt at 1608-1848 K. The diffusion profiles are consistent with the model that molecular H2O is the diffusion species. Based on the above speciation model, H2Om and H2Ot diffusivity (in m2/s) in haploandesite at 743-873 K, 100 MPa, and H2Ot ? 2.5 wt.% can be formulated as
6.
H2O diffusion in dacitic melt was investigated at 0.48-0.95 GPa and 786-893 K in a piston-cylinder apparatus. The diffusion couple design was used, in which a nominally dry dacitic glass makes one half and is juxtaposed with a hydrous dacitic glass containing up to ∼8 wt.% total water (H2Ot). H2O concentration profiles were measured on quenched glasses with infrared microspectroscopy. The H2O diffusivity in dacite increases rapidly with water content under experimental conditions, similar to previous measurements at the same temperature but at pressure <0.15 GPa. However, compared with the low-pressure data, H2O diffusion at high pressure is systematically slower. H2O diffusion profiles in dacite can be modeled by assuming molecular H2O (H2Om) is the diffusing species. Total H2O diffusivity DH2Ot within 786-1798 K, 0-1 GPa, and 0-8 wt.% H2Ot can be expressed as: where DH2Ot is in m2/s, T is temperature in K, P is pressure in GPa, K = exp(1.49 − 2634/T) is the equilibrium constant of speciation reaction (H2Om+O?2OH) in the melt, X = C/18.015/[C/18.015 + (100 − C)/33.82], C is wt.% of H2Ot, and 18.015 and 33.82 g/mol correspond to the molar masses of H2O and anhydrous dacite on a single oxygen basis. Compared to H2O diffusion in rhyolite, diffusivity in dacite is lower at intermediate temperatures but higher at superliquidus temperatures. This general H2O diffusivity expression can be applied to a broad range of geological conditions, including both magma chamber processes and volcanic eruption dynamics from conduit to the surface. 相似文献
7.
Dieke Postma 《Geochimica et cosmochimica acta》1985,49(4):1023-1033
Redox reactions between Fe2+ in solution and Mn-oxides are proposed as a mechanism for concentration of Mn in sediments both during weathering and diagenesis in marine sediments, e.g. the formation of Mn-nodules.If such a mechanism is to be effective, then reaction rates between Fe2+ and Mn-oxides should be fast. The kinetics and stoichiometry of the reaction between dissolved Fe2+ and synthetically prepared birnessite (Mn7O13·5H2O) were studied experimentally in the pH range 3–6.Results show a stoichiometry which at pH < 4 conforms to a simple reaction between Fe2+ and birnessite, releasing Mn2+ and Fe3+ to the solution. At pH > 4 FeOOH is precipitated and excess Fe2+ consumption compared to the theoretical stoichiometry is observed. The excess Fe2+ consumption is not due to a formation of a quantitative MnOOH layer but rather to adsorption.Reaction kinetics are very fast at pH < 4 and change at pH 4 to a slower mechanism. At pH > 4 the reaction is fast initially until 17% of the bimessite has dissolved and changes then to a slower stage. The later stage can be described by the equation: where J is the overall rate of Mn2+ release, m0 and m the mass of birnessite at time t = 0 and t > 0, β = 6.76?0.94 pH and γ has values of 0.76 at pH 5 and 0.39 at pH 6. The rate constant k is 7.2·10?7 moles s?1 g?1 (moles/1)?0.31 at pH 5 and 9.6·10?8 moles s?1 g?1 (moles/1)0.06 at pH 6.Diffusion calculations show that the rate is controlled by surface reaction and it is tentatively proposed that the availability of vacancies in octahedral [MnO6]sheets of the birnessite surface could be rate controlling. It is concluded that reactions between Fe(II) and birnessite, and probably other Mn-oxides, are fast enough to be important in natural environments at the earth surface. 相似文献
8.
Hydration of rhyolitic glass during weathering as characterized by IR microspectroscopy 总被引：1，自引：0，他引：1
Tadashi Yokoyama Satoshi Okumura Satoru Nakashima 《Geochimica et cosmochimica acta》2008,72(1):117-125
The mechanism and rate of hydration of rhyolitic glass during weathering were studied. Doubly polished thin sections of two rhyolites with different duration of weathering (Ohsawa lava: 26,000 yr, Awanomikoto lava: 52,000 yr) were prepared. Optical microscope observation showed that altered layers had developed along the glass surfaces. IR spectral line profile analysis was conducted on the glass sections from the surface to the interior for a length of 250 μm and the contents of molecular H2O (H2Om), OH species (OH) and total water (H2Ot) were determined. The diffusion profile of H2Om in Ohsawa lava extends beyond the layer observed by optical microscope. The content of H2Om in the hydrated region is much higher than that of OH species. Thus, the reaction from H2Om to OH appears to be little and H2Om is the dominant water species moving into the glass during weathering. Based on the concentration profiles, the diffusion coefficients of H2Om(DH2Om) and H2Ot(DH2Ot) were determined to be 2.8 × 10−10 and 3.4 × 10−10 μm2 s−1 for Ohsawa lava, and 5.2 × 10−11 and 4.1 × 10−11 μm2 s−1 for Awanomikoto lava, respectively. The obtained DH2Om during weathering are more than 2-3 orders of magnitude larger than the diffusion coefficient at ∼20 °C that is extrapolated from the diffusivity data for >400 °C. This might suggest that the mechanism of water transport is different at weathering conditions and >400 °C. 相似文献
9.
绿洲防护林系统的最优控制模式及其应用研究 总被引：3，自引：0，他引：3
以河西地区绿洲防护林系统为研究对象，分析了防护林资源分布的时空特征及建群种的增长动态，运用生物控制理论，构建了防护林区生物资源管理的最大持续产量模型、生态经济意义下的最优控制模型及多资源种群控制模型。根据有关模型和试验观测结果，确定了防护林建群种的资源保护指标、生态经济意义下的最优种群水平和人工调控措施。该防护林主要建群种二白杨胸径的保护指标为 k/2＝18．22cm，在不同成本与价格比下计算了主要建群种二白杨胸径指标的个最优控制量。估算了防护林系统的生态需水量，其中农田生态需水量为 1 796 m3/hm2，固沙林和阻沙防护林生态需水量为57 100m3/hm2，并提出了相应的持续发展对策。 相似文献
10.
Adil Hassib 《Physics and Chemistry of Minerals》1980,6(1):31-36
Electron spin resonance of allowed (Δm=0) and forbidden (Δm=±1) hyperfine transitions of Mn2+ in sodalite, Na8(Al6Si6O24)Cl2, is reported. No fine structure other than the central M=∣+1/2>?∣?1/2> transition is observed. From intensity ratios of forbidden to allowed transitions and doubling of allowed lines in powder spectra the crystal field parameter |D| was estimated as equal to (8±5) 10?3 cm?1. The g-value for the spectrum was obtained as equal to 2.0033±0.0005. The hyperfine structure constant |A| was 83±1 gauss, equal to (77±1) 10?4 cm?1. 相似文献
11.
L.G Austin K Shoji V.K Bhatia F.F Aplan 《International Journal of Mineral Processing》1974,1(2):107-123
The Alyavdin equation for batch grinding data is: where P(χ,t) is the weight fraction less than size χ after grinding time t, c (χ) is constant with t and p is a constant close to one. It is shown that this equation is illogical (except for a single size of feed) unless c (χ) varies with P(χ,0), which makes the equation of little utility. A new empirical equation is developed for finite size intervals: which reduces to the Alyavdin equation for a single size of feed, and which gives consistent computations for any feed size distribution. Techniques are given for determining Ki, γ values from sets of batch grinding data. The values are then used to predict size distributions for other times and other feed size distributions. The equation was quite successful in predicting size distributions in batch milling: (a) providing the feed size distribution was not un-natural, that is, not truncated or (b) if a truncated feed was used, the values of Ki and γ are determined from size distributions of grinding of the same type of feed. Thus, Ki, γ are not, unfortunately, completely independent of the starting feed size distribution. 相似文献
12.
Mark J. Harris Ekhard K. H. Salje Bernd K. Guttler Michael A. Carpenter 《Physics and Chemistry of Minerals》1989,16(7):649-658
Natural samples of K-feldspar representing various states of Al, Si order were characterised using X-ray methods, transmission electron microscopy, and Fourier transform infrared spectroscopy. Line profiles of infrared absorption bands were observed to show strong correlation with the degree of Al, Si order present. In particular, the absorption frequencies of the 540 cm?1 and 640 cm?1 bands were seen to vary by ca. 10 cm?1 between sanidine and microcline, with modulated samples respresenting intermediate behaviour. Linewidths of these modes also decrease by ca. 50% in this series. The experimental results are discussed within the framework of Hard Mode Infrared Spectroscopy (HMIS), and it is shown that the absorption frequencies vary with the short range order parameter τ = (4t1-1)2 and the symmetry breaking order parameter describing Al, Si order, Q od=(t1 0?t1 m)/Q od=(t1 0+t1 m), where t1 is the average Al occupancy on the T1 sites and t1 o and t1 m are the individual site occupancies of the T1 o and T1 m sites, respectively. The structural state of orthoclase is characterised by strain-induced modulations with large spatial variations of the modulation wavelength. No such modulations were observed in the degree of local Al, Si order. Sanidine shows mode hardening in excess of the extrapolated effect of symmetry breaking Al, Si order, which is presumably related to nonsymmetry breaking ordering between T1 and T2 sites and/or as yet unobserved short range order of the symmetry breaking ordering scheme. The possibility of an additional phase transition in K-feldspar at temperatures above 1300 K is discussed. 相似文献
13.
We suggest a generalization of the standard Chandrasekhar model for degenerate dwarfs. We apply an equation of state for a degenerate ideal electron gas in the form of a Sommerfeld expansion in the parameter k B T(r)/m 0 c 2. The radial temperature distribution T(r) is modeled taking into account the presence of the isothermal core. The model has four dimensionless parameters, two microscopic (the relativistic parameter at the stellar center x 0 and the chemical-composition parameter ?? e = A/Z) and two macroscopic (the dimensionless temperature T 0 * = k B T c /m 0 c 2 and dimensionless radius ?? 0 = R c /R of the core, where R c and R are the radii of the core and dwarf). We found x 0, ?? e , and T 0 * for about 3000 DA white dwarfs, based on their masses, radii, and effective temperatures from the Sloan Digital Sky Survey Data Release 4; ?? 0 was treated as a free parameter. The influence of temperature effects on the macroscopic characteristics is analyzed, in particular, the minimum mass and maximum radii of the stars. Based on our computed energy-radius dependence, we suggest an interpretation of the observed radius distribution for these dwarfs. 相似文献
14.
Rachel J. Harris Conrad A. Pilditch Barry L. Greenfield Vicki Moon Ingrid Kröncke 《Estuaries and Coasts》2016,39(3):815-828
Fine sediment inputs can alter estuarine ecosystem structure and function. However, natural variations in the processes that regulate sediment transport make it difficult to predict their fate. In this study, sediments were sampled at different times (2011–2012) from 45 points across intertidal sandflat transects in three New Zealand estuaries (Whitford, Whangamata, and Kawhia) encompassing a wide range in mud (≤63 μm) content (0–56 %) and macrofaunal community structure. Using a core-based erosion measurement device (EROMES), we calculated three distinct measures of sediment erosion potential: erosion threshold (? c ; N m?2), erosion rate (ER; g m?2 s?1), and change in erosion rate with increasing bed shear stress (m e ; g N?1 s?1). Collectively, these measures characterized surface (? c and ER) and sub-surface (m e ) erosion. Benthic macrofauna were grouped by functional traits (size and motility) and data pooled across estuaries to determine relationships between abiotic (mud content, mean grain size) and biotic (benthic macrofauna, microbial biomass) variables and erosion measures. Results indicated that small bioturbating macrofauna (predominantly freely motile species <5 mm in size) destabilized surface sediments, explaining 23 % of the variation in ? c (p ≤ 0.01) and 59 % of the variation in ER (p ≤ 0.01). Alternatively, mud content and mean grain size cumulatively explained 61 % of the variation in m e (p ≤ 0.01), where increasing mud and grain size stabilized sub-surface sediments. These results highlight that the importance of biotic and abiotic predictors vary with erosion stage and that functional group classifications are a useful way to determine the impact of benthic macrofauna on sediment erodibility across communities with different species composition. 相似文献
15.
Growth of grains having different initial sizes (10?3 cm?≤?r 0?≤?1 cm) has been investigated by coagulation processes inside gas giant protoplanets, formed by disk instability, in the mass range 0.3 to 10 Jovian masses. In doing so, we have determined distribution of thermodynamic variables inside the protoplanets and using the results we have determined growth of the grains having assumed initial sizes. Regarding the transference of heat inside the protoplanets, we have considered the possible two cases of interest, namely convection and conduction-radiation. The results of our calculation show that growth of the grains depends on protoplanetary masses and on initial states of the protoplanets and eventually all the grains having assumed different initial sizes acquire almost the same distribution in the central regions of respective protoplanets in the respective cases. 相似文献
16.
A. D. Kuz’min B. Ya. Losovskii S. V. Logvinenko I. I. Litvinov 《Astronomy Reports》2008,52(11):910-916
Our measurements of the arrival-time delays of radio pulses from the Crab pulsar, PSR B0531+21, at low frequencies 111, 63, and 44 MHz revealed additional delays compared to the usual quadratic frequency relation, Δt(v) ∝ v ?2. These additional delays are 65 ms between 63 MHz and 111 MHz—i.e., a factor of two longer than the pulsar’s period, i.e., a factor of five longer than the pulsar period—and cannot be explained by the “twisting” of the magnetic-field lines by the rotation of the pulsar. We suggest the model in which a previously unknown high-density plasma layer with a high electron concentration is present along the line of sight in the Crab nebula, causing an additional frequency-dependent delay of the observed radio pulses at low frequencies due to the contribution of the n e 2 v ?4 term in the dispersion-delay formula. The parameters of this inferred layer have been derived: emission measure EM ? 4 × 106 pc/cm6, electron density n e ? 106 cm?3, depth along the line of sight d ? 4 × 10?6 pc, and electron temperature T e ≥ 2 × 106 K. 相似文献
17.
Zhu Zhenhua 《中国地球化学学报》1988,7(4):336-347
Given ri =f i(F) andK i = gi(F), wherer i is the mineral mass fraction in an instantaneous solid phase,K i the partition coefficient, andf i(F) andg i(F) respectively the continuous, sectionally smooth functions of solidification degreeF, we have: $$C^1 = \frac{{C_0 }}{{1 - F}} \cdot \exp \left( { - \int_0^F {\frac{{\Sigma fi(F) \cdot g_i (F)}}{{1 - F}} \cdot dF} } \right)and \bar C^s = \frac{{C_o }}{F}\left[ {1 - (1 - F) \cdot \frac{{C^1 }}{{C^0 }}} \right]$$ Also presented in this paper are other equations describing the compositional changes of solid and liquid phases in magmatic processes (partial melting). The following understanding is attained based on the application of these equations to the Hushan pluton of Mt. Taishan in the west of Shandong Province. 1) For granitoids changes in rock-forming minerals may not be taken into consideration in theoretical modelling of REE distribution, but accessory minerals rich in REE, especially those highly rich in some REE must be taken into account. 2) In the case of well differentiated granitoids, it can be assumed thatFε [0,1] may exert only little influence on the calculations. 3) In practice the (La / Sm)-La diagram should be applied with care. 相似文献
18.
The accuracies of three different evolutionary artificial neural network (ANN) approaches, ANN with genetic algorithm (ANN-GA), ANN with particle swarm optimization (ANN-PSO) and ANN with imperialist competitive algorithm (ANN-ICA), were compared in estimating groundwater levels (GWL) based on precipitation, evaporation and previous GWL data. The input combinations determined using auto-, partial auto- and cross-correlation analyses and tried for each model are: (i) GWL t?1 and GWL t?2; (ii) GWL t?1, GWL t?2 and P t ; (iii) GWL t?1, GWL t?2 and E t ; (iv) GWL t?1, GWL t?2, P t and E t ; (v) GWL t?1, GWL t?2 and P t?1 where GWL t , P t and E t indicate the GWL, precipitation and evaporation at time t, individually. The optimal ANN-GA, ANN-PSO and ANN-ICA models were obtained by trying various control parameters. The best accuracies of the ANN-GA, ANN-PSO and ANN-ICA models were obtained from input combination (i). The mean square error accuracies of the ANN-GA and ANN-ICA models were increased by 165 and 124% using ANN-PSO model. The results indicated that the ANN-PSO model performed better than the other models in modeling monthly groundwater levels. 相似文献
19.
Frank J. Millero Benjamin DiTrolio Gabriele Lando 《Geochimica et cosmochimica acta》2009,73(11):3109-96
Spectrophotometric measurements of the pH in natural waters such as seawater have been shown to yield precise results. In this paper, the sulfonephthalein indicator m-cresol purple (mCP, H2I) has been used to determine the pH of NaCl brines. The indicator has been calibrated in NaCl solutions from 5 to 45 °C and ionic strengths from 0.03 to 5.5 m. The calibrations were made using TRIS buffers (0.03 m, TRIS/TRIS-HCl) with known dissociation constants pKTRIS in NaCl solutions [Foti C., Rigano C. and Sammartano S. (1999) Analysis of thermodynamic data for complex formation: protonation of THAM and fluoride ion at different temperatures and ionic strength. Ann. Chim. 89, 1-12]. The values of pH were determined from
pH=pKmCP+log{(R-e1)/(e2-Re3)} 相似文献
20.
G. Diego Gatta Paolo Lotti Fabrizio Nestola Marco Merlini Daria Pasqual Andrea Lausi 《Physics and Chemistry of Minerals》2013,40(5):401-409
The thermo-elastic behaviour of Be2BO3(OH)0.96F0.04 (i.e. natural hambergite, Z = 8, a = 9.7564(1), b = 12.1980(2), c = 4.4300(1) Å, V = 527.21(1) Å3, space group Pbca) has been investigated up to 7 GPa (at 298 K) and up to 1,100 K (at 0.0001 GPa) by means of in situ single-crystal X-ray diffraction and synchrotron powder diffraction, respectively. No phase transition or anomalous elastic behaviour has been observed within the pressure range investigated. P?V data fitted to a third-order Birch–Murnaghan equation of state give: V 0 = 528.89(4) Å3, K T0 = 67.0(4) GPa and K′ = 5.4(1). The evolution of the lattice parameters with pressure is significantly anisotropic, being: K T0(a):K T0(b):K T0(c) = 1:1.13:3.67. The high-temperature experiment shows evidence of structure breakdown at T > 973 K, with a significant increase in the full-width-at-half-maximum of all the Bragg peaks and an anomalous increase in the background of the diffraction pattern. The diffraction pattern was indexable up to 1,098 K. No new crystalline phase was observed up to 1,270 K. The diffraction data collected at room-T after the high-temperature experiment showed that the crystallinity was irreversibly compromised. The evolution of axial and volume thermal expansion coefficient, α, with T was described by the polynomial function: α(T) = α 0 + α 1 T ?1/2. The refined parameters for Be2BO3(OH)0.96F0.04 are: α 0 = 7.1(1) × 10?5 K?1 and α 1 = ?8.9(2) × 10?4 K ?1/2 for the unit-cell volume, α 0(a) = 1.52(9) × 10?5 K?1 and α 1(a) = ?1.4(2) × 10?4 K ?1/2 for the a-axis, α 0(b) = 4.4(1) × 10?5 K?1 and α 1(b) = ?5.9(3) × 10?4 K ?1/2 for the b-axis, α 0(c) = 1.07(8) × 10?5 K?1 and α 1(c) = ?1.5(2) × 10?4 K ?1/2 for the c-axis. The thermo-elastic anisotropy can be described, at a first approximation, by α 0(a):α 0(b):α 0(c) = 1.42:4.11:1. The main deformation mechanisms in response to the applied temperature, based on Rietveld structure refinement, are discussed. 相似文献