共查询到20条相似文献,搜索用时 15 毫秒
1.
The brightness temperatures of the Microwave sensor MSMR (Multichannel Scanning Microwave Radiometer) launched in May 1999
onboard Indian Oceansat-1 IRS-P4 are used to develop a direct retrieval method for latent heat flux by multivariate regression
technique. The MSMR measures the microwave radiances at 8 channels at frequencies of 6.6, 10.7, 18 and 21 GHz at both vertical
and horizontal polarizations. It is found that the surface LHF (Latent Heat Flux) is sensitive to all the channels. The coefficients
were derived using the National Centre for Environmental Prediction (NCEP) reanalysis data of three months: July, September,
November of 1999. The NCEP daily analyzed latent heat fluxes and brightness temperatures observed by MSMR were used to derive
the coefficients. Validity of the derived coefficients was checked within situ observations over the Indian Ocean and with NCEP analyzed LHF for global points. The LHF derived directly from the MSMR brightness
temperature (Tb) yielded an accuracy of 35 watt/m2. LHF was also computed by applying bulk formula using the geophysical parameters extracted from MSMR. In this case the errors
were higher apparently due to the errors involved in derivation of the geophysical parameters. 相似文献
2.
A. K. Varma R. M. Gairola Samir Pokhrel B. S. Gohil A. K. Mathur Vijay K. Agarwal 《Journal of Earth System Science》2002,111(3):257-266
In this paper rain estimation capability of MSMR is explored. MSMR brightness temperature data of six channels corresponding
to three frequencies of 10, 18 and 21 GHz are colocated with the TRMM Microwave Imager (TMI) derived rain rates to find a
new empirical algorithm for rain rate by multiple regression. Multiple correlation analysis involving various combinations
of channels in linear and non-linear forms and rain rate from TMI is carried out, and thus the best possible algorithm for
rain rate measurement was identified which involved V and H polarized brightness temperature measurements at 10 and 18 GHz
channels. This algorithm explained about 82 per cent correlation (r) with rain rate, and 1.61 mm h-1 of error of estimation.
Further, this algorithm is used for generating global average rain rate map for two contrasting months of August (2000) and
January (2001) of northern and southern hemispheric summers, respectively. MSMR derived monthly averaged rain rates are compared
with similar estimates from TRMM Precipitation Radar (PR), and it was found that MSMR derived rain rates match well, quantitatively
and qualitatively, with that from PR. 相似文献
3.
North-east India is seismically very active and has experienced many widelydistributed shallow, large earthquakes. Earthquake
generation model for the region was studied using seismicity data [(1906–1984) prepared by National Geophysical Data Centre
(NGDC), Boulder Colorado, USA]. For establishing statistical relations surface wave magnitudes (M
s≥5·5) have been considered. In the region four seismogenic sources have been identified which show the occurrences of atleast
three earthquakes of magnitude 5·5≤M
s≤7·5 giving two repeat times. It is observed that the time interval between the two consecutive main shock depends on the
preceding main shock magnitude (M
p) and not on the following main shock magnitude (M
f) revealing the validity of time predictable model for the region. Linear relation between logarithm of repeat time (T) and preceding main shock magnitude (M
p) is established in the form of logT=cM
p+a. The values ofc anda are estimated to be 0–36 and 1–23, respectively. The relation may be used for seismic hazard evaluation in the region. 相似文献
4.
Sicheng Wang Xi Liu Yingwei Fei Qiang He Hejing Wang 《Physics and Chemistry of Minerals》2012,39(3):189-198
Using a conventional high-T furnace, the solid solutions between magnesiochromite and manganochromite, (Mg1−x
Mn
x
)Cr2O4 with x = 0.00, 0.19, 0.44, 0.61, 0.77 and 1.00, were synthesized at 1,473 K for 48 h in open air. The ambient powder X-ray diffraction
data suggest that the V–x relationship of the spinels does not show significant deviation from the Vegard’s law. In situ high-T powder X-ray diffraction measurements were taken up to 1,273 K at ambient pressure. For the investigated temperature range,
the unit-cell parameters of the spinels increase smoothly with temperature increment, indicating no sign of cation redistribution
between the tetrahedral and octahedral sites. The V–T data were fitted with a polynomial expression for the volumetric thermal expansion coefficient (aT = a0 + a1 T + a2 T - 2 \alpha_{T} = a_{0} + a_{1} T + a_{2} T^{ - 2} ), which yielded insignificant a
2 values. The effect of the composition on a
0 is adequately described by the equation a
0 = [17.7(8) − 2.4(1) × x] 10−6 K−1, whereas that on a
1 by the equation a
1 = [8.6(9) + 2.1(11) × x] 10−9 K−2. 相似文献
5.
Solid solubility and structural phase transitions in (Ca
x
Sr1-x
)TiOGeO4have been studied by means of in situ high temperature X-ray powder diffraction. The displacive A2/a–P21/a phase transition analogous to titanite has been followed across the solid solution. Strain analysis indicates a transition
temperature of T
c=594 ± 10 K for SrTiOGeO4 and the additional occurrence of an isosymmetric anomaly at T
i
=800 ± 25 K, in analogy to the isomorphous compound CaTiOGeO4. Lattice parameters as a function of temperature and composition have been determined by X-ray powder diffraction between
room temperature and a maximum temperature of 1123 K. The e
11 and e
13 components dominate the strain tensor. All compositions across the solid solution exhibit close to tricritical phase transitions
P21/a–A2/a. The critical temperature remains almost unaffected by substitution of Sr for Ca, but the magnitude of the spontaneous strain
drops significantly with even small amounts of Sr present. 相似文献
6.
Ground-based microwave radiometers are getting great attention in recent years due to their capability to profile the temperature and humidity at high temporal and vertical resolution in the lower troposphere. The process of retrieving these parameters from the measurements of radiometric brightness temperature (T B ) includes the inversion algorithm, which uses the back ground information from a forward model. In the present study, an algorithm development and evaluation of this forward model for a ground-based microwave radiometer, being developed by Society for Applied Microwave Electronics Engineering and Research (SAMEER) of India, is presented. Initially, the analysis of absorption coefficient and weighting function at different frequencies was made to select the channels. Further the range of variation of T B for these selected channels for the year 2011, over the two stations Mumbai and Delhi is discussed. Finally the comparison between forward-model simulated T B s and radiometer measured T B s at Mahabaleshwar (73.66 °E and 17.93°N) is done to evaluate the model. There is good agreement between model simulations and radiometer observations, which suggests that these forward model simulations can be used as background for inversion models for retrieving the temperature and humidity profiles. 相似文献
7.
Norimasa Nishiyama Takehiko Yagi Shigeaki Ono Hirotada Gotou Tatsuhiko Harada Takumi Kikegawa 《Physics and Chemistry of Minerals》2007,34(3):131-143
In situ X-ray diffraction measurements of Fe- and Al-bearing MgSiO3-rich perovskite (FeAl-Pv), which was synthesized from a natural orthopyroxene, were performed at pressures of 19–32 GPa and
temperatures of 300–1,500 K using a combination of a Kawai-type apparatus with eight sintered-diamond anvils and synchrotron
radiation. Two runs were performed using a high-pressure cell with two sample chambers, and both MgSiO3 perovskite (Mg-Pv) and FeAl-Pv were synthesized simultaneously in the same cell. Thus we were able to measure specific volumes
(V/V
0) of Mg-Pv and FeAl-Pv at the same P−T conditions. At all the measurement conditions, values of the specific volume of FeAl-Pv are consistent with those of Mg-Pv
within 2 Standard Deviation, strongly suggesting that effect of incorporation of iron and aluminum on the thermoelastic properties
of magnesium silicate perovskite is undetectable in this composition, pressure, and temperature range. Two additional runs
were performed using a high-pressure cell that has one sample chamber and unit-cell volumes of FeAl-Pv were measured at pressures
and temperatures up to 32 GPa and 1,500 K, respectively. All the unit-cell volume data of FeAl-Pv perovskite were fitted to
the high temperature Birch–Murnaghan equation of state and a complete set of thermoelastic parameters of this perovskite was
determined with an assumption of K′
300,0 = 4. The determined parameters are K
300,0 = 243(3) GPa, (∂K
T,0/∂T)
P
= −0.030(8) GPa/K, a
0 = 2.78(18) × 10−5 K−1, and b
0 = 0.88(28) × 10−8 K−2, where a
0 and b
0 are the coefficients of the following expression describing the zero-pressure thermal expansion: α
T,0 = a
0 + b
0
T. The equation-of-state parameters of FeAl-Pv are in good agreement with those of MgSiO3 perovskite at the conditions corresponding to the uppermost part of the lower mantle. 相似文献
8.
D. G. Isaak J. D. Carnes O. L. Anderson H. Cynn E. Hake 《Physics and Chemistry of Minerals》1998,26(1):31-43
The ambient pressure elastic properties of single-crystal TiO2 rutile are reported from room temperature (RT) to 1800 K, extending by more than 1200 oK the maximum temperature for which rutile elasticity data are available. The magnitudes
of the temperature derivatives decrease with increasing temperature for five of the six adiabatic elastic moduli (C
ij
). At RT, we find (units, GPa): C
11=268(1); C
33=484(2); C
44=123.8(2); C
66=190.2(5); C
23=147(1); and C
12=175(1). The temperature derivatives (units, GPa K−1) at RT are: (∂C
11/∂T)
P
=−0.042(5); (∂C
33/∂T)
P
=−0.087(6); (∂C
44/∂T)
P
=−0.0187(2); (∂C
66/∂T)
P
=−0.067(2); (∂C
23/∂T)
P
=−0.025; and (∂C
12/∂T)
P
−0.048(5). The values for K
S
(adiabatic bulk modulus) and μ (isotropic shear modulus) and their temperature derivatives are K
S
=212(1) GPa; μ=113(1) GPa; (∂K
S
/∂T)
P
=−0.040(4) GPa K−1; and (∂μ/∂T)
P
=−0.018(1) GPa K−1. We calculate several dimensionless parameters over a large temperature range using our new data. The unusually high values
for the Anderson-Gròneisen parameters at room temperature decrease with increasing temperature. At high T, however, these parameters are still well above those for most other oxides. We also find that for TiO2, anharmonicity, as evidenced by a non-zero value of [∂ln (K
T
)/∂lnV]
T
, is insignificant at high T, implying that for the TiO2 analogue of stishovite, thermal pressure is independent of volume (or pressure). Systematic relations indicate that ∂2
K
S
/∂T∂P is as high as 7×10−4 K−1 for rutile, whereas ∂2μ/∂T∂P is an order of magnitude less.
Received: 19 September 1997 / Revised, accepted: 27 February 1998 相似文献
9.
Timotej Verbovšek 《Environmental Geology》2008,53(6):1173-1182
Diagenetic effects upon the hydraulic parameters of dolomite aquifers were examined. Results indicate that dolomites affected
only by late (burial) diagenesis are economically more interesting to exploit than those formed first by early and then also
affected by late diagenesis, as the values of most studied hydraulic parameters (transmissivity, specific capacity, linearized
specific capacity and maximum yields) are higher in the former group. Data were collected from the hydrogeological reports
of 298 wells in dolomites from Permian to Cretaceous age in Slovenia, classified in a relational hydrogeological database
and analyzed by statistical methods. The studied parameters are hydraulic conductivity K, transmissivity T, specific capacity q (=Q/s), linearized specific capacity Ql (=q/d) and maximum yields Q
max. Values of the studied parameters are distributed log-normally according to most normality tests and span several orders
of magnitude. Statistical tests show significant differences between the “late” and “early + late” groups for parameters q, Ql and T, and non-significant differences for K and Q
max. 相似文献
10.
Behavior of epidote at high pressure and high temperature: a powder diffraction study up to 10 GPa and 1,200 K 总被引:1,自引:0,他引:1
G. Diego Gatta Marco Merlini Yongjae Lee Stefano Poli 《Physics and Chemistry of Minerals》2011,38(6):419-428
The thermo-elastic behavior of a natural epidote [Ca1.925 Fe0.745Al2.265Ti0.004Si3.037O12(OH)] has been investigated up to 1,200 K (at 0.0001 GPa) and 10 GPa (at 298 K) by means of in situ synchrotron powder diffraction.
No phase transition has been observed within the temperature and pressure range investigated. P–V data fitted with a third-order Birch–Murnaghan equation of state (BM-EoS) give V
0 = 458.8(1)Å3, K
T0 = 111(3) GPa, and K′ = 7.6(7). The confidence ellipse from the variance–covariance matrix of K
T0 and K′ from the least-square procedure is strongly elongated with negative slope. The evolution of the “Eulerian finite strain”
vs “normalized stress” yields Fe(0) = 114(1) GPa as intercept values, and the slope of the regression line gives K′ = 7.0(4). The evolution of the lattice parameters with pressure is slightly anisotropic. The elastic parameters calculated
with a linearized BM-EoS are: a
0 = 8.8877(7) Å, K
T0(a) = 117(2) GPa, and K′(a) = 3.7(4) for the a-axis; b
0 = 5.6271(7) Å, K
T0(b) = 126(3) GPa, and K′(b) = 12(1) for the b-axis; and c
0 = 10.1527(7) Å, K
T0(c) = 90(1) GPa, and K’(c) = 8.1(4) for the c-axis [K
T0(a):K
T0(b):K
T0(c) = 1.30:1.40:1]. The β angle decreases with pressure, βP(°) = βP0 −0.0286(9)P +0.00134(9)P
2 (P in GPa). The evolution of axial and volume thermal expansion coefficient, α, with T was described by the polynomial function: α(T) = α0 + α1
T
−1/2. The refined parameters for epidote are: α0 = 5.1(2) × 10−5 K−1 and α1 = −5.1(6) × 10−4 K1/2 for the unit-cell volume, α0(a) = 1.21(7) × 10−5 K−1 and α1(a) = −1.2(2) × 10−4 K1/2 for the a-axis, α0(b) = 1.88(7) × 10−5 K−1 and α1(b) = −1.7(2) × 10−4 K1/2 for the b-axis, and α0(c) = 2.14(9) × 10−5 K−1 and α1(c) = −2.0(2) × 10−4 K1/2 for the c-axis. The thermo-elastic anisotropy can be described, at a first approximation, by α0(a): α0(b): α0(c) = 1 : 1.55 : 1.77. The β angle increases continuously with T, with βT(°) = βT0 + 2.5(1) × 10−4
T + 1.3(7) × 10−8
T
2. A comparison between the thermo-elastic parameters of epidote and clinozoisite is carried out. 相似文献
11.
The synthetic solid solutions between lead fluorapatite and lead fluorvanadate apatite, Pb10[(PO4)6−x
(VO4)
x
]F2 with x equal to 0, 1, 2, 3, 4, 5, and 6, were compressed up to about 9 GPa at ambient temperature by using a diamond-anvil cell
coupled with synchrotron X-ray radiation. A second-order Birch–Murnaghan equation of state was used to fit the data. As the
substitution of the PO4
3− cations by the VO4
3− cations progresses, the isothermal bulk modulus steadily decreases, with a maximum reduction of about 16% (from 68.4(16)
GPa for Pb10(PO4)6F2 to 57.2(28) GPa for Pb10(VO4)6F2). For the entire composition range, the a-axis dimension remains more compressible than the c-axis dimension, with the ratio of the axial bulk moduli (K
T−c
:K
T−a
) larger than 1. The ratio of K
T−c
to K
T−a
increases from about 1.04(4) to 1.23(14) as the composition parameter x increases from 0 to 6, suggesting that the apatite solid solutions Pb10[(PO4)6−x
(VO4)
x
]F2 become more elastically anisotropic. 相似文献
12.
Rupa Kamineni S. R. H. Rizvi S. C. Kar U. C. Mohanty R. K. Paliwal 《Journal of Earth System Science》2002,111(3):351-364
Oceansat-1 was successfully launched by India in 1999, with two payloads, namely Multi-frequency Scanning Microwave Radiometer
(MSMR) and Ocean Color Monitor (OCM) to study the biological and physical parameters of the ocean. The MSMR sensor is configured
as an eight-channel radiometer using four frequencies with dual polarization. The MSMR data at 75 km resolution from the Oceansat-I
have been assimilated in the National Centre for Medium Range Weather Forecasting (NCMRWF) data assimilation forecast system.
The operational analysis and forecast system at NCMRWF is based on a T80L18 global spectral model and Spectral Statistical
Interpolation (SSI) scheme for data analysis. The impact of the MSMR data is seen globally, however it is significant over
the oceanic region where conventional data are rare. The dry-nature of the control analyses have been removed by utilizing
the MSMR data. Therefore, the total precipitable water data from MSMR has been identified as a very crucial parameter in this
study. The impact of surface wind speed from MSMR is to increase easterlies over the tropical Indian Ocean. Shifting of the
positions of westerly troughs and ridges in the south Indian Ocean has contributed to reduction of temperature to around 30‡S. 相似文献
13.
Hidetoshi Asanuma Eiji Ohtani Takeshi Sakai Hidenori Terasaki Seiji Kamada Tadashi Kondo Takumi Kikegawa 《Physics and Chemistry of Minerals》2010,37(6):353-359
The melting temperature of Fe–18 wt% Si alloy was determined up to 119 GPa based on a change of laser heating efficiency and
the texture of the recovered samples in the laser-heated diamond anvil cell experiments. We have also investigated the subsolidus
phase relations of Fe–18 wt% Si alloy by the in-situ X-ray diffraction method and confirmed that the bcc phase is stable at
least up to 57 GPa and high temperature. The melting curve of the alloy was fitted by the Simon’s equation, P(GPa)/a = (T
m(K)/T
0)
c
, with parameters, T
0 = 1,473 K, a = 3.5 ± 1.1 GPa, and c = 4.5 ± 0.4. The melting temperature of bcc Fe–18 wt% Si alloy is comparable with that of pure iron in the pressure range
of this work. The melting temperature of Fe–18 wt% Si alloy is estimated to be 3,300–3,500 K at 135 GPa, and 4,000–4,200 K
at around 330 GPa, which may provide the lower bound of the temperatures at the core–mantle boundary and the inner core–outer
core boundary if the light element in the core is silicon. 相似文献
14.
S. A. T. Redfern G. Artioli R. Rinaldi C. M. B. Henderson K. S. Knight B. J. Wood 《Physics and Chemistry of Minerals》2000,27(9):630-637
The partitioning of Fe and Mg between the M1 and M2 octahedral sites of olivine has been investigated by in situ time-of-flight
neutron powder diffraction. The degree of M-cation order was determined from direct measurements of site occupancies in a
synthetic sample of Fo50Fa50 heated to 1250 °C at the Fe-FeO oxygen buffer. Fe shows slight preference for M1 at temperatures
below about 600 °C, progressively disordering on heating to this temperature. Above 630 °C, the temperature at which site
preferences cross over (T
cr), Fe preferentially occupies M2, becoming progressively more ordered into M2 on increasing temperature. The cation-ordering
behaviour is discussed in relation to the temperature dependence of the M1 and M2 site geometries, and it is suggested that
vibrational entropy, crystal field effects and changes in bond characteristics play a part in the cross-over of partitioning
behaviour. The temperature dependence of site ordering is modelled using a Landau expansion of the free energy of ordering
of the type ΔG = −hQ + gTQ + (T − T
c)Q
2 + Q
4, with a/h = 0.00406 K−1, b/h = 2.3, T
c = 572 K and g/h = 0.00106 K−1. These results suggest that the high-temperature ordering behaviour across the forsterite-fayalite join will have a bearing
on the activity-composition relations of this important rock-forming mineral, and indicate that Fe-Mg olivine solid solutions
become less ideal as temperature increases.
Received: 12 August 1999 / Accepted: 25 April 2000 相似文献
15.
Analysis of an oasis microclimate in China’s hyperarid zone 总被引:2,自引:0,他引:2
The microclimate of a desert oasis in China’s hyperarid zone was monitored, analysed and compared to that of nearby forested
lands. Factors associated with differences in photosynthetically active radiation (PAR) between clear, cloudy and dust storm
days are discussed. Desert oases were shown to fulfill ecological functions such as altering solar radiation, adjusting near-ground
and land surface temperatures, reducing temperature differences, lowering wind velocity, and increasing soil and atmospheric
humidity. Total solar radiation within the oasis was roughly half that above the forest canopy. During the growing season,
air temperatures in Populus euphratica Olivier and Tamarix ramosissima Ledeb. woodlands were, on average, 1.62 and 0.83°C lower, respectively, than that in surrounding woodlands. The greater the
forest cover, the greater was the difference in temperature. Air temperature was higher at the upper storey than that at the
lower storey of the community, i.e., air temperature increased with increasing height above the soil surface. During the growing
season, relative humidity was higher in woodlands than in surrounding areas: relative humidity in P. euphratica and T. ramosissima woodlands were, on average, 8.5 and 4.2% higher, respectively, than that in the surrounding area. Mean wind velocity in the
P. euphratica forest land was 0.33 m/s, 2.31 m/s lower than that in the surrounding area. On dust storm days PAR and total radiation, Q, were significantly lower than that on cloudy or clear days. Their ratio, η
Q
= PAR/Q, was larger and much more variable on dust storm days than that on clear or cloudy days. 相似文献
16.
Detlef W. Fasshauer Niranjan D. Chatterjee Ladislav Cemic 《Contributions to Mineralogy and Petrology》1998,133(1-2):186-198
Heat capacity, thermal expansion, and compressibility data have been obtained for a number of selected phases of the system
NaAlSiO4-LiAlSiO4-Al2O3-SiO2-H2O. All C
p
measurements have been executed by DSC in the temperature range 133–823 K. The data for T ≥ 223 K have been fitted to the function C
p
(T) = a + cT
−2 + dT
−0.5 + fT
−3, the fit parameters being The thermal expansion data (up to 525 °C) have been fitted to the function V
0(T) = V
0(T) [1 + v
1 (T−T
0) + v
2 (T−T
0)2], with T
0 = 298.15 K. The room-temperature compressibility data (up to 6 GPa) have been smoothed by the Murnaghan equation of state.
The resulting parameters are These data, along with other phase property and reaction reversal data from the literature, have
been simultaneously processed by the Bayes method to derive an internally consistent thermodynamic dataset (see Tables 6 and
7) for the NaAlSiO4-LiAlSiO4-Al2O3-SiO2-H2O quinary. Phase diagrams generated from this dataset are compatible with cookeite-, ephesite-, and paragonite-bearing assemblages
observed in metabauxites and common metasediments. Phase diagrams obtained from the same database are also in agreement with
the cookeite-free, petalite-, spodumene-, eucryptite-, and bikitaite-bearing assemblages known to develop in the subsolidus
phase of recrystallization of␣lithium-bearing pegmatites. It is gratifying to note that the cookeite phase relations predicted
earlier by Vidal and Goffé (1991) in the context of the system Li2O-Al2O3-SiO2-H2O agree with our results in a general way.
Received: 19 May 1998 / Accepted: 25 June 1998 相似文献
17.
G. Diego Gatta Marco Merlini Hanns-Peter Liermann André Rothkirch Mauro Gemmi Alessandro Pavese 《Physics and Chemistry of Minerals》2012,39(5):385-397
The thermoelastic behavior of a natural clintonite-1M [with composition: Ca1.01(Mg2.29Al0.59Fe0.12)Σ3.00(Si1.20Al2.80)Σ4.00O10(OH)2] has been investigated up to 10 GPa (at room temperature) and up to 960°C (at room pressure) by means of in situ synchrotron
single-crystal and powder diffraction, respectively. No evidence of phase transition has been observed within the pressure
and temperature range investigated. P–V data fitted with an isothermal third-order Birch–Murnaghan equation of state (BM-EoS) give V
0 = 457.1(2) ?3, K
T0 = 76(3)GPa, and K′ = 10.6(15). The evolution of the “Eulerian finite strain” versus “normalized stress” shows a linear positive trend. The
linear regression yields Fe(0) = 76(3) GPa as intercept value, and the slope of the regression line leads to a K′ value of 10.6(8). The evolution of the lattice parameters with pressure is significantly anisotropic [β(a) = 1/3K
T0(a) = 0.0023(1) GPa−1; β(b) = 1/3K
T0(b) = 0.0018(1) GPa−1; β(c) = 1/K
T0(c) = 0.0072(3) GPa−1]. The β-angle increases in response to the applied P, with: βP = β0 + 0.033(4)P (P in GPa). The structure refinements of clintonite up to 10.1 GPa show that, under hydrostatic pressure, the structure rearranges
by compressing mainly isotropically the inter-layer Ca-polyhedron. The bulk modulus of the Ca-polyhedron, described using
a second-order BM-EoS, is K
T0(Ca-polyhedron) = 41(2) GPa. The compression of the bond distances between calcium and the basal oxygens of the tetrahedral
sheet leads, in turn, to an increase in the ditrigonal distortion of the tetrahedral ring, with ∂α/∂P ≈ 0.1°/GPa within the P-range investigated. The Mg-rich octahedra appear to compress in response to the applied pressure, whereas the tetrahedron
appears to behave as a rigid unit. The evolution of axial and volume thermal expansion coefficient α with temperature was
described by the polynomial α(T) = α0 + α1
T
−1/2. The refined parameters for clintonite are as follows: α0 = 2.78(4) 10−5°C−1 and α1 = −4.4(6) 10−5°C1/2 for the unit-cell volume; α0(a) = 1.01(2) 10−5°C−1 and α1(a) = −1.8(3) 10−5°C1/2 for the a-axis; α0(b) = 1.07(1) 10−5°C−1 and α1(b) = −2.3(2) 10−5°C1/2 for the b-axis; and α0(c) = 0.64(2) 10−5°C−1 and α1(c) = −7.3(30) 10−6°C1/2for the c-axis. The β-angle appears to be almost constant within the given T-range. No structure collapsing in response to the T-induced dehydroxylation was found up to 960°C. The HP- and HT-data of this study show that in clintonite, the most and the less expandable directions do not correspond to the most and
the less compressible directions, respectively. A comparison between the thermoelastic parameters of clintonite and those
of true micas was carried out. 相似文献
18.
As a part of the MONTBLEX-90 observational programme, Kytoon and Doppler sodar observations were taken at Kharagpur. These
data are analysed to study the turbulent characteristics of the atmospheric boundary layer in terms of stability, temperature
structure function (C
T
2
) and velocity structure function (C
v
2
).C
T
2
follows aZ
−4/3 law on most of the days, whereas the variation ofC
V
2
is not systematic.C
V
2
andC
T
2
values are found to vary between 10−5−10−1 m4/3s−2 and 10−5−10−2°C2 m−2/3 respectively. 相似文献
19.
G. Diego Gatta Romano Rinaldi K. S. Knight G. Molin G. Artioli 《Physics and Chemistry of Minerals》2007,34(3):185-200
The temperature induced structural evolution and thermoelastic behaviour of a natural (Pbca) orthopyroxene (Opx), with chemical formula M2(Mg0.856Ca0.025Fe2+
0.119) M1(Mg0.957Fe2+
0.011Fe3+
0.016Cr0.011Al0.005)Al0.032Si1.968O6, from a suite of high pressure ultramafic nodules of mantle origin, have been investigated by in-situ neutron powder diffraction
at several temperatures starting from 1,200°C down to 150°C. Unit-cell parameter variations as a function of T show no phase transition within this temperature range. The volume thermal expansion coefficient, α = V
−1(∂V/∂T) P0, varies linearly with T. The axial thermal expansion coefficients, αj = l
j−1(∂l
j/∂T)P0, increase non-linearly with T. The principal Lagrangian unit-strain coefficients (ɛ//a, ɛ//b, ɛ//c), increase continuously with T. However, the orientation of the unit-strain ellipsoid appears to change with T. With decreasing T, the values of the unit-strain coefficients along the b and c axes tend to converge. The orientation at ΔT = 1,080°C is maintained down to the lowest temperature (150°C). The two non-equivalent tetrahedral chains, TA
n
OA3n
and TB
n
OB3n
, are kinked differently. At room-T, the TB
n
OB3n
chain is more strongly kinked by about 23° than the TA
n
OA3n
chain. With increasing T, the difference decreases by 3° for the TB
n
OB3n
chain. The intersite cation exchange reaction between M1 and M2 (Mg2+ and Fe2+) shows a slight residual order at 1,200°C followed by reordering with decreasing temperature although seemingly not with
a definite progressive trend. At the lowest temperature reached (150°C), reordering has occurred with the same value of partitioning
coefficient K
D as that before heating. The absence of the expected phase transition is most likely due to the presence of minor amounts
of Fe3+, Al, Ca and Cr which must play a crucial role on the thermoelastic behaviour and phase stability fields in natural Opx, with
consequent important petrologic and geological implications. 相似文献
20.
M. V. Charykova V. G. Krivovichev O. S. Yakovenko W. Depmeier 《Geology of Ore Deposits》2011,53(7):501-513
The behavior of arsenic at the Earth’s surface and nearby at low temperatures and pressures depends mainly on the redox potential
and the acidity-alkalinity of the crystallization media. These parameters determine the migration of arsenic compounds and
their precipitation as various solid phases. Understanding the mechanism of arsenic’s behavior under surface conditions, which
is important for solving environmental problems, is an urgent task of contemporary mineralogy and geochemistry. The activities
of the components in natural waters beyond the zones of natural (oxidation zones) and man-made contamination with arsenic
(a
ΣAs = 3 × 10−8, a
ΣFe = 10−5, a
ΣCu = 10−7, a
ΣZn = 5 × 10−7, a
ΣCo = 10−8, a
ΣNi = 6 × 10−8, a
ΣPb = 10−8) and in waters formed in the oxidation zone (a
ΣSe = 10−3, a
ΣFe = 10−2, a
ΣCu = 10−2, a
ΣZn = 5 × 10−2, a
ΣCo = 10−3, a
ΣNi = 10−2, a
ΣPb = 10−4) have been estimated. Eh-pH diagrams were calculated and plotted using the Geochemist’s Workbench (GMB 7.0) software package.
The database comprises the thermodynamic parameters of 46 elements, 47 main particles, 48 redox pairs, 551 particles in solution,
624 solid phases, and 10 gases. The Eh-pH diagrams of the Me-As-H2O systems (Me = Co, Ni, Fe, Cu, Zn, Pb) were plotted for the average contents of these elements in the underground water and
for their higher contents in the oxidation zones of sulfide deposits. The formation of Co, Ni, Fe, Cu, Zn, and Pb arsenates
at the surface is discussed. 相似文献