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1.
To perform a fuzzy risk assessment the simplest way is to calculate the fuzzy expected value and convert fuzzy risk into non-fuzzy
risk, i.e., a crisp value. In doing so, there is a transition from a fuzzy set to a crisp set. Therefore, the first step is
to define an α level value, followed by selecting the elements x with a subordinate degree A( x) ≥ α. The fuzzy expected values, Ea ( x) \underline{E}_{\alpha } (x) and [`( E)] a ( x) \overline{E}_{\alpha } (x) , of a possibility–probability distribution represent the fuzzy risk values being calculated. Therefore, we can obtain a conservative
risk value, a venture risk value and a maximum probability risk value. Under such an α level, three risk values can be calculated. As α adopts all values between the set [0, 1], it is possible to obtain a series of risk values. Therefore, the fuzzy risk may
either be a multi-valued risk or a set-valued risk. Calculation of the fuzzy expected value of a flood risk in the Jinhua
River basin has been performed based on the interior–outer-set model. The selection of an α value is dependent on the confidence in different groups of people, while the selection of a conservative risk value or a
venture risk value is dependent on the risk preference of these people. 相似文献
2.
Single-crystal electron paramagnetic resonance (EPR) spectra of fast-electron-irradiated quartz, after annealing at 120 and
200°C, reveal five new E′ type centers, herein labeled
E 5￠ , E 6￠ , E 7￠ , E 8￠ , \text and E 9￠ E_{ 5}^{\prime } ,\,E_{ 6}^{\prime } ,\,E_{ 7}^{\prime } ,\,E_{ 8}^{\prime } ,\,{\text{and}}\,E_{ 9}^{\prime } . Centers
E 5￠ , E 7￠ , \text and E 9￠ E_{ 5}^{\prime } ,\,E_{ 7}^{\prime } ,\,{\text{and}}\,E_{ 9}^{\prime } are characterized by the orientations of the unique principal g and A( 29Si) axes close to a short Si–O bond direction, hence representing new variants of the well-established E 1￠ E_{ 1}^{\prime } center. Centers E 6￠ E_{ 6}^{\prime } and E 8￠ E_{ 8}^{\prime } have the orientations of the unique principal g and A( 29Si) axes approximately along a long Si–O bond direction, similar to the E 2￠ E_{ 2}^{\prime } centers. Therefore, these new E′ type centers apparently arise from the removal of different oxygen atoms and represent variable local distortions around
the oxygen vacancies. 相似文献
3.
The effect of crystal structure relaxation in oxygen-based Cr3+-containing minerals on the crystal field stabilization energy (CFSE) is considered. It is shown that the dependence of
\textCFSE\textCr 3+ {\text{CFSE}}_{{{\text{Cr}}^{ 3+ } }} , which is found from optical absorption spectra, on the average interatomic distances is described by the power function
with a negative exponent
c \mathord | / |
\vphantom c [`(R)]n [`(R)]n {c \mathord{\left/ {\vphantom {c {\bar{R}^{n} }}} \right. \kern-\nulldelimiterspace} {\bar{R}^{n} }} , where n approaches 5, as predicted theoretically, for pure Cr3+ compounds, but decreases to 1.0–1.5 for Cr3+-containing oxide and silicate solid solutions. The deviation of the experimental dependence for solid solutions from the
theoretical curve is due to structure relaxation, which tends to bring the local structure of Cr3+ ions closer to the structure in the pure Cr compound, thus producing changes in interatomic distances between the nearest
neighbors with respect to those in the average structure determined by X-ray diffraction. As a consequence, the mixing enthalpy
of Cr3+-bearing solid solutions can be represented by the sum of contributions from lattice strain and CFSE. The latter contribution
is most often negative in sign and, therefore, brings the Al–Cr solid solutions close to an ideal solid solution. It is supposed
that the increased Cr content in minerals from deep-seated mantle xenoliths and mineral inclusions in diamonds results from
the effect of
\textCFSE\textCr 3+ {\text{CFSE}}_{{{\text{Cr}}^{ 3+ } }} enhanced by high pressure. 相似文献
4.
Experiments were conducted to determine the water solubility of alkali basalts from Etna, Stromboli and Vesuvius volcanoes,
Italy. The basaltic melts were equilibrated at 1,200°C with pure water, under oxidized conditions, and at pressures ranging
from 163 to 3,842 bars. Our results show that at pressures above 1 kbar, alkali basalts dissolve more water than typical mid-ocean
ridge basalts (MORB). Combination of our data with those from previous studies allows the following simple empirical model
for the water solubility of basalts of varying alkalinity and fO 2 to be derived:
\text H 2 \text O( \text wt% ) = \text H 2 \text O\textMORB ( \text wt% ) + ( 5.84 ×10 - 5 *\text P - 2.29 ×10 - 2 ) ×( \text Na2 \text O + \text K2 \text O )( \text wt% ) + 4.67 ×10 - 2 ×\Updelta \text NNO - 2.29 ×10 - 1 {\text{H}}_{ 2} {\text{O}}\left( {{\text{wt}}\% } \right) = {\text{ H}}_{ 2} {\text{O}}_{\text{MORB}} \left( {{\text{wt}}\% } \right) + \left( {5.84 \times 10^{ - 5} *{\text{P}} - 2.29 \times 10^{ - 2} } \right) \times \left( {{\text{Na}}_{2} {\text{O}} + {\text{K}}_{2} {\text{O}}} \right)\left( {{\text{wt}}\% } \right) + 4.67 \times 10^{ - 2} \times \Updelta {\text{NNO}} - 2.29 \times 10^{ - 1} where H 2O MORB is the water solubility at the calculated P, using the model of Dixon et al. ( 1995). This equation reproduces the existing database on water solubilities in basaltic melts to within 5%. Interpretation of
the speciation data in the context of the glass transition theory shows that water speciation in basalt melts is severely
modified during quench. At magmatic temperatures, more than 90% of dissolved water forms hydroxyl groups at all water contents,
whilst in natural or synthetic glasses, the amount of molecular water is much larger. A regular solution model with an explicit
temperature dependence reproduces well-observed water species. Derivation of the partial molar volume of molecular water using
standard thermodynamic considerations yields values close to previous findings if room temperature water species are used.
When high temperature species proportions are used, a negative partial molar volume is obtained for molecular water. Calculation
of the partial molar volume of total water using H 2O solubility data on basaltic melts at pressures above 1 kbar yields a value of 19 cm 3/mol in reasonable agreement with estimates obtained from density measurements. 相似文献
5.
We examined feeding success of young-of-the-year winter flounder ( Pseudopleuronectes americanus Walbaum) (20–50 mm TL) around a large, municipal pier in the Hudson River estuary, USA. Replicate, 3-h feeding experiments were conducted using benthic cages (0.64 m 2) deployed under, at the edge, and outside of the pier during late spring and early summer in 1998 and 1999. Significantly more winter flounder caged under piers had empty stomachs ( [`( x)]\bar x =71.9%) than at the edge or in open water ( [`( x)]\bar x =29.2% and 14.4%, respectively). Feeding intensity was significantly higher outside of the pier ( [`( x)]\bar x =0.40%) than the edge or under the pier ( [`( x)]\bar x =0.19% and 0.03%, respectively). Simultaneous with feeding experiments, benthic core samples were collected adjacent to cages. Variability was high, but abundances of prey were consistently higher under the pier ( [`( x)]\bar x =200.14±113.3 SD in 1998; 335±290.2 in 1999) than at the edge ( [`( x)]\bar x =126.6±50.2 in 1998; 70.8±68.5 in 1999) or in open water ( [`( x)]\bar x =53.4±16.1 in 1998; 123.8±193.9 in 1999). No significant differences in prey biomass were determined, suggesting that small, numerous prey were available under the pier and fewer, larger taxa were present at the edge and outside. Data indicate that feeding is suppressed among young-of-the-year winter flounder caged under piers in spite of sufficient prey available. Based on these and other experiments we submit that areas under piers are not suitable long-term habitats for juvenile fish because they interfere with normal feeding activities. 相似文献
6.
The present work aims in discussing a principle that distinguishes between elastic parameters sets, $ \{ \Upphi \} \equiv \{ K_{0} , \, K^{\prime}, \, V_{0} ,\ldots\} The present work aims in discussing a principle that distinguishes between elastic parameters sets,
{ \Upphi } o { K0 , K￠, V0 ,?} \{ \Upphi \} \equiv \{ K_{0} , \, K^{\prime}, \, V_{0} ,\ldots\} , on the basis of an energetic criterion: once a reference set,
{ \UpphiR } \{ \Upphi_{R} \} , is given, another one can be fixed,
{ \Upphi min } \left\{ {\Upphi_{ \min } } \right\} , so that they are as close as possible to each other, but yield non-equivalent deformation energy curves
\Updelta G({ \Upphi } )\textdeform \Updelta G(\{ \Upphi \} )_{\text{deform}} , i.e. they give
\Updelta G({ \UpphiR } )\textdeform \Updelta G(\{ \Upphi_{R} \} )_{\text{deform}} and
\Updelta G({ \Upphi min } )\textdeform \Updelta G(\{ \Upphi_{ \min } \} )_{\text{deform}} such that
| \Updelta G({ \Upphi min } )\textdeform - \Updelta G({ \UpphiR } )\textdeform | 3 1×s[\Updelta G\textdeform ]. \left| {\Updelta G(\{ \Upphi_{ \min } \} )_{\text{deform}} - \Updelta G(\{ \Upphi_{R} \} )_{\text{deform}} } \right| \ge 1\times \sigma [\Updelta G_{\text{deform}} ]. ΔG
deform, calculated using the equation of state (EoS), and its uncertainty σ[ΔG
deform], obtained by a propagation of the errors affecting
{ \Upphi } \{ \Upphi \} are crucial to fix which mineral assemblage forms at P–T conditions and allow one to assess the reliability of such a prediction. We explore some properties related to the principle
introduced, using the average values of the elastic parameters found in literature and related uncertainties for di-octahedral
mica, olivine, garnet and clinopyroxene. Two elementary applications are briefly discussed: the effect of refining V
0 in fitting EoSs to P–V experimental data, in the case of garnet and omphacite, and the phengite 3T–2M
1 relative stability, controlled by pressure. 相似文献
7.
Crystal-plastic olivine deformation to produce subgrain boundaries composed of edge dislocations is an inevitable consequence
of asthenospheric mantle flow. Although crystal-plastic deformation and serpentinization are spatio-temporally decoupled,
we identified compositional readjustments expressed on the micrometric level as a striped Fe-enriched (
[`( X)] \textFe \bar{X}_{\text{Fe}} = 0.24 ± 0.02 (zones); 0.12 ± 0.02 (bulk)) or Fe-depleted (
[`( X)] \textFe \bar{X}_{\text{Fe}} = 0.10 ± 0.01 (zones); 0.13 ± 0.01 (bulk)) zoning in partly serpentinized olivine grains from two upper mantle sections in
Norway. Focused ion beam sample preparation combined with transmission electron microscopy (TEM) and aberration-corrected
scanning TEM, enabling atomic-level resolved electron energy-loss spectroscopic line profiling, reveals that every zone is
immediately associated with a subgrain boundary. We infer that the zonings are a result of the environmental Fe 2+Mg −1 exchange potential during antigorite serpentinization of olivine and the drive toward element exchange equilibrium. This
is facilitated by enhanced solid-state diffusion along subgrain boundaries in a system, which otherwise re-equilibrates via
dissolution-reprecipitation. Fe enrichment or depletion is controlled by the silica activity imposed on the system by the
local olivine/orthopyroxene mass ratio, temperature and the effect of magnetite stability. The Fe-Mg exchange coefficients
K\textD\textAtg/\textOl K_{\text{D}}^{{{\text{Atg}}/{\text{Ol}}}} between both types of zoning and antigorite display coalescence toward exchange equilibrium. With both types of zoning, Mn
is enriched and Ni depleted compared with the unaffected bulk composition. Nanometer-sized, heterogeneously distributed antigorite
precipitates along olivine subgrain boundaries suggest that water was able to ingress along them. Crystallographic orientation
relationships gained via electron backscatter diffraction between olivine grain domains and different serpentine vein generations
support the hypothesis that serpentinization was initiated along olivine subgrain boundaries. 相似文献
8.
The system Ca 2Al 3Si 3O 11(O/OH)-Ca 2Al 2FeSi 3O 11(O/OH), with emphasis on the Al-rich portion, was investigated by synthesis experiments at 0.5 and 2.0 GPa, 500-800 °C, using the technique of producing overgrowths on natural seed crystals. Electron microprobe analyses of overgrowths up to >100 µm wide have located the phase transition from clinozoisite to zoisite as a function of P-T-X ps and a miscibility gap in the clinozoisite solid solution. The experiments confirm a narrow, steep zoisite-clinozoisite two-phase loop in T-X ps section. Maximum and minimum iron contents in coexisting zoisite and clinozoisite are given by X pszo (max) = 1.9*10 - 4 T+ 3.1*10 - 2 P - 5.36*10 - 2{\rm X}_{{\rm ps}}^{{\rm zo}} {\rm (max) = 1}{\rm .9*10}^{ - 4} T{\rm + 3}{\rm .1*10}^{ - 2} P - {\rm 5}{\rm .36*10}^{ - 2} and X psczo (min) = (4.6 * 10 - 4 - 4 * 10 - 5 P) T + 3.82 * 10 - 2 P - 8.76 * 10 - 2{\rm X}_{{\rm ps}}^{{\rm czo}} {\rm (min)} = {\rm (4}{\rm .6} * {\rm 10}^{ - {\rm 4}} - 4 * {\rm 10}^{ - {\rm 5}} P{\rm )}T + {\rm 3}{\rm .82} * {\rm 10}^{ - {\rm 2}} P - {\rm 8}{\rm .76} * {\rm 10}^{ - {\rm 2}} (P in GPa, T in °C). The iron-free end member reaction clinozoisite = zoisite has equilibrium temperatures of 185ᇆ °C at 0.5 GPa and 0ᇆ °C at 2.0 GPa, with ( Hr0=2.8ǃ.3 kJ/mol and ( Sr0=4.5ǃ.4 J/mol2K. At 0.5 GPa, two clinozoisite modifications exist, which have compositions of clinozoisite I ~0.15 to 0.25 X ps and clinozoisite II >0.55 X ps. The upper thermal stability of clinozoisite I at 0.5 GPa lies slightly above 600 °C, whereas Fe-rich clinozoisite II is stable at 650 °C. The schematic phase relations between epidote minerals, grossular-andradite solid solutions and other phases in the system CaO-Al 2O 3-Fe 2O 3-SiO 2-H 2O are shown. 相似文献
9.
Lead chloride formation constants at 25°C were derived from analysis of previous spectrophotometrically generated observations
of lead speciation in a variety of aqueous solutions (HClO 4–HCl and NaCl–NaClO 4 mixtures, and solutions of MgCl 2 and CaCl 2). Specific interaction theory analysis of these formation constants produced coherent estimates of (a) PbCl +,
\text PbCl20 {\text{PbCl}}_{2}^{0} , and PbCl 3− formation constants at zero ionic strength, and (b) well-defined depictions of the dependence of these formation constants
on ionic strength. Accompanying examination of a recent IUPAC critical assessment of lead formation constants, in conjunction
with the spectrophotometrically generated formation constants presented in this study, revealed significant differences among
various subsets of the IUPAC critically selected data. It was found that these differences could be substantially reduced
through reanalysis of the formation constant data of one of the subsets. The resulting revised lead chloride formation constants
are in good agreement with the formation constants derived from the earlier spectrophotometrically generated data. Combining
these data sets provides an improved characterization of lead chloride complexation over a wide range of ionic strengths:
|
log \text Cl b 1 = 1. 4 9 1- 2.0 4 I 1/ 2 ( 1+ 1. 5 I 1/ 2 ) - 1 + 0. 2 3 8 I log \text Cl b 2 = 2.0 6 2- 3.0 6 I 1/ 2 ( 1+ 1. 5 I 1/ 2 ) - 1 + 0. 3 6 9 I log \text Cl b 3 = 1. 8 9 9- 3.0 6 I 1/ 2 ( 1+ 1. 5 I 1/ 2 ) - 1 + 0. 4 3 9 I. \begin{gathered} {\log}\,{}_{\text{ Cl}} \beta_{ 1} = 1. 4 9 1- 2.0 4\,I^{ 1/ 2} \left( { 1+ 1. 5\,I^{ 1/ 2} } \right)^{ - 1} +\,0. 2 3 8\,I \hfill \\ {\log}\,{}_{\text{ Cl}} \beta_{ 2} = 2.0 6 2- 3.0 6\,I^{ 1/ 2} \left( { 1+ 1. 5\,I^{ 1/ 2} } \right)^{ - 1} +\,0. 3 6 9\,I \hfill \\ {\log}\,{}_{\text{ Cl}} \beta_{ 3} = 1. 8 9 9- 3.0 6\,I^{ 1/ 2} \left( { 1+ 1. 5\,I^{ 1/ 2} } \right)^{ - 1} +\,0. 4 3 9\,I. \hfill \\ \end{gathered} 相似文献
10.
Diffusion of Li under anhydrous conditions at 1 atm and under fluid-present elevated pressure (1.0–1.2 GPa) conditions has
been measured in natural zircon. The source of diffusant for 1-atm experiments was ground natural spodumene, which was sealed
under vacuum in silica glass capsules with polished slabs of zircon. An experiment using a Dy-bearing source was also conducted
to evaluate possible rate-limiting effects on Li diffusion of slow-diffusing REE +3 that might provide charge balance. Diffusion experiments performed in the presence of H 2O–CO 2 fluid were run in a piston–cylinder apparatus, using a source consisting of a powdered mixture of spodumene, quartz and zircon
with oxalic acid added to produce H 2O–CO 2 fluid. Nuclear reaction analysis (NRA) with the resonant nuclear reaction 7Li(p,γ) 8Be was used to measure diffusion profiles for the experiments. The following Arrhenius parameters were obtained for Li diffusion
normal to the c-axis over the temperature range 703–1.151°C at 1 atm for experiments run with the spodumene source:
|
D\textLi = 7.17 ×10 - 7 exp( - 275 ±11 \textkJmol - 1 /\textRT)\textm2 \texts - 1. D_{\text{Li}} = 7.17 \times 10^{ - 7} { \exp }( - 275 \pm 11\,{\text{kJmol}}^{ - 1} /{\text{RT}}){\text{m}}^{2} {\text{s}}^{ - 1}. 相似文献
11.
Sogdianite, a double-ring silicate of composition
( \text Zr0. 7 6 \text Ti0. 3 84 + \text Fe0. 7 33 + \text Al0.13 ) \Upsigma = 2 ( \square 1. 1 5 \text Na0. 8 5 ) \Upsigma = 2 \text K[\text Li 3 \text Si 1 2 \text O 30 ] ( {\text{Zr}}_{0. 7 6} {\text{Ti}}_{0. 3 8}^{4 + } {\text{Fe}}_{0. 7 3}^{3 + } {\text{Al}}_{0.13} )_{\Upsigma = 2} \left( {\square_{ 1. 1 5} {\text{Na}}_{0. 8 5} } \right)_{\Upsigma = 2} {\text{K}}[{\text{Li}}_{ 3} {\text{Si}}_{ 1 2} {\text{O}}_{ 30} ] from Dara-i-Pioz, Tadjikistan, was studied by the combined application of 57Fe M?ssbauer spectroscopy and electronic structure calculations. The M?ssbauer spectrum confirms published microprobe and
X-ray single-crystal diffraction results that indicate that Fe 3+ is located at the octahedral A-site and that no Fe 2+ is present. Both the measured and calculated quadrupole splitting, Δ E
Q, for Fe 3+ are virtually 0 mm s −1. Such a value is unusually small for a silicate and it is the same as the Δ E
Q value for Fe 3+ in structurally related sugilite. This result is traced back to the nearly regular octahedral coordination geometry corresponding
to a very symmetric electric field gradient around Fe 3+. A crystal chemical interpretation for the regular octahedral geometry and the resulting low Δ E
Q value for Fe 3+ in the M?ssbauer spectrum of sogdianite is that structural strain is largely “taken up” by weak Li–O bonds permitting highly
distorted LiO 4 tetrahedra. Weak Li–O bonding allows the edge-shared more strongly bonded Fe 3+O 6 octahedra to remain regular in geometry. This may be a typical property for all double-ring silicates with tetrahedrally
coordinated Li. 相似文献
12.
Near-liquidus phase relationships of a spinel lherzolite-bearing olivine melilitite from Tasmania were investigated over a P, T range with varying
,
, and
. At 30 kb under MH-buffered conditions, systematic changes of liquidus phases occur with increasing
(
= CO 2/CO 2 +H 2O+olivine melilitite). Olivine is the liquidus phase in the presence of H 2O alone and is joined by clinopyroxene at low
. Increasing
eliminates olivine and clinopyroxene becomes the only liquidus phase. Further addition of CO 2 brings garnet+orthopyroxene onto the liquidus together with clinopyroxene, which disappears with even higher CO 2. The same systematic changes appear to hold at higher and lower pressures also, only that the phase boundaries are shifted to different
. The field with olivine- +clinopyroxene becomes stable to higher
with lower pressure and approaches most closely the field with garnet+orthopyroxene+clinopyroxene at about 27 kb, 1160 °C,
0.08 and
0.2 (i.e., 6–7% CO 2+ 7–8% H 2O). Olivine does not coexist with garnet+orthopyroxene+clinopyroxene under these MH-buffered conditions. Lower oxygen fugacities do not increase the stability of olivine to higher
and do not change the phase relationships and liquidus temperatures drastically. Thus, it is inferred that olivine melilitite 2927 originates as a 5% melt (inferred from K 2
O and P 2O 5 content) from a pyrolite source at about 27kb, 1160 dg with about 6–7% CO 2 and 7–8% H 2O dissolved in the melt. The highly undersaturated character of the melt and the inability to find olivine together with garnet and orthopyroxene on the liquidus (in spite of the close approach of the respective liquidus fields) can be explained by reaction relationships of olivine and clinopyroxene with orthopyroxene, garnet and melt in the presence of CO 2. 相似文献
13.
We present a theoretical model for diffusive daughter isotope loss in radiochronological systems with increasing temperature.
It complements previous thermochronological models, which focused on cooling, and allows for testing opening and resetting
of radiochronometers during heating. The opening and resetting temperatures are, respectively, where R is the gas constant, E and D
0 are the activation energy and the pre-exponential factor of the Arrhenius law for diffusion of the daughter isotope, a the half-size of the system (radius for sphere and cylinder and half-thickness for plane sheet) and τ the heating time constant, related to the heating rate by
For opening and resetting thresholds corresponding to 1 and 99% loss of daughter isotope, respectively, the retention parameters
for sphere, cylinder and plane sheet geometries are A
op = 1.14 × 10 5, 5.07 × 10 4 and 1.27 × 10 4 and A
rs = 2.40, 1.37 and 0.561. According to this model, the opening and resetting temperatures are significantly different for most
radiochronometers and are, respectively, lower and higher than the closure temperature.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
14.
This paper presents a design approach for strip footings upon glacier ice. Safety against ultimate limit state is proved by
the geotechnical slip-line field solution by Prandtl. Glacier ice at 0°C can be modelled as purely cohesive material. Statistical
evaluation of uniaxial compression tests with high strain rate revealed a mean value of the cohesion of 600 kPa and a characteristic
value c
k
= 355 kPa (5% fractile). With a coefficient of variation V
c
= 0.3, the partial safety factor turns out to be γ
c
= 1.9. An approximate solution for estimating the creep settlement rate is presented to check the serviceability limit state: with the width b of the strip foundation, p the foundation pressure and for ice at 0°C. Experiences on Stubai glacier with grate shaped footings showed that creep settlements occurring per year
due to maximum foundation pressures 250 kPa did not influence the operation and the maintenance of the cable cars. 相似文献
15.
Quartz and rutile were synthesized from silica-saturated aqueous fluids between 5 and 20 kbar and from 700 to 940°C in a piston-cylinder
apparatus to explore the potential pressure effect on Ti solubility in quartz. A systematic decrease in Ti-in-quartz solubility
occurs between 5 and 20 kbar. Titanium K-edge X-ray absorption near-edge structure (XANES) measurements demonstrate that Ti 4+ substitutes for Si 4+ on fourfold tetrahedral sites in quartz at all conditions studied. Molecular dynamic simulations support XANES measurements
and demonstrate that Ti incorporation onto fourfold sites is favored over interstitial solubility mechanisms. To account for
the P– T dependence of Ti-in-quartz solubility, a least-squares method was used to fit Ti concentrations in quartz from all experiments
to the simple expression
|
RTlnX\textTiO 2 \textquartz = - 60952 + 1.520 ·T(K) - 1741 ·P(kbar) + RTlna\textTiO 2 RT\ln X_{{{\text{TiO}}_{ 2} }}^{\text{quartz}} = - 60952 + 1.520 \cdot T(K) - 1741 \cdot P(kbar) + RT\ln a_{{{\text{TiO}}_{ 2} }} 相似文献
16.
The occurrence of critical assemblages among antigorite, diopside, tremolite, forsterite, talc, calcite, dolomite and magnesite in progressively metamorphosed ophicarbonate rocks, together with experimental data, permits the construction of phase diagrams in terms of the variables P, T, and composition of a binary CO 2-H 2O fluid. Equilibrium constants are given for the 30 equilibria that describe all relations among the above phases. Ophicalcite, ophidolomite, and ophimagnesite assemblages occupy partially overlapping fields in the
diagram. The upper temperature limit of ophicalcite rocks lies below that of ophidolomite and ophimagnesite. The fluid phase in ophicarbonate rocks has
0.8$$
" align="middle" border="0">
, and there are indications that
during their progressive metamorphism is approximately equal to P
total. 相似文献
17.
The equilibrium $${\text{(1}} - y{\text{)Fe}}_{(s)} + \tfrac{{\text{1}}}{{\text{2}}}{\text{O}}_{{\text{2(g)}}} \rightleftarrows {\text{Fe}}_{{\text{1}} - y} {\text{O}}_{{\text{(}}s,{\text{ in MW)}}} $$ was studied by measuring oxygen potentials for a range of different magnesiowüstite compositions relative to those of the iron-wüstite system in an oxygen concentration cell involving yttria stabilized zirconia as the solid electrolyte. The temperature range covered was 1050 to 1400 K. Separate measurements of the mole fraction of trivalent iron in magnesiowüstite ( x(Fe 3+)) were made and the composition dependence of x(Fe 3+) was taken into account in calculations of the activity-composition relations of FeO, Fe 2/3O and MgO. 相似文献
18.
Ephesite, Na(LiAl 2) [Al 2Si 2O 10] (OH) 2, has been synthesized for the first time by hydrothermal treatment of a gel of requisite composition at 300≦ T(° C)≦700 and \(P_{H_2 O}\) upto 35 kbar. At \(P_{H_2 O}\) between 7 and 35 kbar and above 500° C, only the 2M 1 polytype is obtained. At lower temperatures and pressures, the 1M polytype crystallizes first, which then inverts to the 2M 1 polytype with increasing run duration. The X-ray diffraction patterns of the 1M and 2M 1 poly types can be indexed unambiguously on the basis of the space groups C2 and Cc, respectively. At its upper thermal stability limit, 2M 1 ephesite decomposes according to the reaction (1) $$\begin{gathered} {\text{Na(LiAl}}_{\text{2}} {\text{) [Al}}_{\text{2}} {\text{Si}}_{\text{2}} {\text{O}}_{{\text{10}}} {\text{] (OH)}}_{\text{2}} \hfill \\ {\text{ephesite}} \hfill \\ {\text{ = Na[AlSiO}}_{\text{4}} {\text{] + LiAl[SiO}}_{\text{4}} {\text{] + }}\alpha {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}} {\text{ + H}}_{\text{2}} {\text{O}} \hfill \\ {\text{nepheline }}\alpha {\text{ - eucryptite corundum}} \hfill \\ \end{gathered}$$ Five reversal brackets for (1) have been established experimentally in the temperature range 590–750° C, at \(P_{H_2 O}\) between 400 and 2500 bars. The equilibrium constant, K, for this reaction may be expressed as (2) $$log K{\text{ = }}log f_{{\text{H}}_{\text{2}} O}^* = 7.5217 - 4388/T + 0.0234 (P - 1)T$$ where \(f_{H_2 O}^* = f_{H_2 O} (P,T)/f_{H_2 O}^0\) (1, T), with T given in degrees K, and P in bars. Combining these experimental data with known thermodynamic properties of the decomposition products in (1), the following standard state (1 bar, 298.15 K) thermodynamic data for ephesite were calculated: H f,298.15 0 =-6237372 J/mol, S 298.15 0 =300.455 J/K·mol, G 298.15 0 =-5851994 J/mol, and V 298.15 0 =13.1468 J/bar·mol. 相似文献
19.
By applying the Griffith stress criterion of brittle failure, one can find that the uniaxial compressive strength (σ c) of rocks is eight times the value of the uniaxial tensile strength (σ t). The Griffith strength ratio is smaller than what is normally measured for rocks, even with the consideration of crack closure.
The reason is that Griffith’s theories address only the initiation of failure. Under tensile conditions, the crack propagation
is unstable so that the tensile crack propagation stress (σ cd) t and the peak tensile strength σ t are almost identical to the tensile crack initiation stress (σ ci) t. On the other hand, the crack growth after crack initiation is stable under a predominantly compressive condition. Additional
loading is required in compression to bring the stress from the crack initiation stress σ ci to the peak strength σ c. It is proposed to estimate the tensile strength of strong brittle rocks from the strength ratio of
R = \fracs \textc | s \textt | = 8\fracs \textc s \textci . R = {\frac{{\sigma_{\text{c}} }}{{\left| {\sigma_{\text{t}} } \right|}}} = 8{\frac{{\sigma_{\text{c}} }}{{\sigma_{\text{ci}} }}}. The term
\fracs \textc s \textci {\frac{{\sigma_{\text{c}} }}{{\sigma_{\text{ci}} }}} accounts for the difference of crack growth or propagation in tension and compression in uniaxial compression tests.
\fracs c s ci {\frac{{\sigma_{c} }}{{\sigma_{ci} }}} depends on rock heterogeneity and is larger for coarse grained rocks than for fine grained rocks. σ ci can be obtained from volumetric strain measurement or acoustic emission (AE) monitoring. With the strength ratio R determined, the tensile strength can be indirectly obtained from
| s \textt | = \fracs \textc R = \fracs \textci 8. \left| {\sigma_{\text{t}} } \right| = {\frac{{\sigma_{\text{c}} }}{R}} = {\frac{{\sigma_{\text{ci}} }}{8}}. It is found that the predicted tensile strengths using this method are in good agreement with test data. Finally, a practical
estimate of the Hoek–Brown strength parameter m
i is presented and a bi-segmental or multi-segmental representation of the Hoek–Brown strength envelope is suggested for some
brittle rocks. In this fashion, the rock strength parameters like σ t and m
i, which require specialty tests such as direct tensile (or Brazilian) and triaxial compression tests for their determination,
can be reasonably estimated from uniaxial compression tests. 相似文献
20.
The models recognize that ZrSiO 4, ZrTiO 4, and TiSiO 4, but not ZrO 2 or TiO 2, are independently variable phase components in zircon. Accordingly, the equilibrium controlling the Zr content of rutile
coexisting with zircon is ZrSiO 4 = ZrO 2 (in rutile) + SiO 2. The equilibrium controlling the Ti content of zircon is either ZrSiO 4 + TiO 2 = ZrTiO 4 + SiO 2 or TiO 2 + SiO 2 = TiSiO 4, depending whether Ti substitutes for Si or Zr. The Zr content of rutile thus depends on the activity of SiO 2
as well as T, and the Ti content of zircon depends on and as well as T. New and published experimental data confirm the predicted increase in the Zr content of rutile with decreasing and unequivocally demonstrate that the Ti content of zircon increases with decreasing . The substitution of Ti in zircon therefore is primarily for Si. Assuming a constant effect of P, unit and that and are proportional to ppm Zr in rutile and ppm Ti in zircon, [log(ppm Zr-in-rutile) + log] = A 1 + B 1/ T(K) and [log(ppm Ti-in-zircon) + log − log] = A 2 + B 2/ T, where the A and B are constants. The constants were derived from published and new data from experiments with buffered by either quartz or zircon + zirconia, from experiments with defined by the Zr content of rutile, and from well-characterized natural samples. Results are A 1 = 7.420 ± 0.105; B 1 = −4,530 ± 111; A 2 = 5.711 ± 0.072; B 2 = −4,800 ± 86 with activity referenced to α-quartz and rutile at P and T of interest. The zircon thermometer may now be applied to rocks without quartz and/or rutile, and the rutile thermometer
applied to rocks without quartz, provided that and are estimated. Maximum uncertainties introduced to zircon and rutile thermometry by unconstrained and can be quantitatively assessed and are ≈60 to 70°C at 750°C. A preliminary assessment of the dependence of the two thermometers
on P predicts that an uncertainty of ±1 GPa introduces an additional uncertainty at 750°C of ≈50°C for the Ti-in-zircon thermometer
and of ≈70 to 80°C for the Zr-in-rutile thermometer. 相似文献
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