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1.
S. Tiwari D. M. Chate M. K. Srivastava P. D. Safai A. K. Srivastava D. S. Bisht B. Padmanabhamurty 《Natural Hazards》2012,61(2):521-531
Temporal variation of PM10 using 2-year data (January, 2007–December, 2008) of Delhi is presented. PM10 varied from 42 to 200 μg m−3 over January to December, with an average 114.1 ± 81.1 μg m−3. They are comparable with the data collected by Central Pollution Control Board (National Agency which monitors data over
the entire country in India) and are lower than National Ambient Air Quality (NAAQ) standard during monsoon, close to NAAQ
during summer but higher in winter. Among CO, NO2, SO2, rainfall, temperature, and wind speed, PM10 shows good correlation with CO. Also, PM10, PM2.5, and PM1 levels on Deepawali days when fireworks were displayed are presented. In these festive days, PM10, PM2.5, and PM1 levels were 723, 588, and 536 μg m−3 in 2007 and 501, 389, and 346 μg m−3 in 2008. PM10, PM2.5, and PM1 levels in 2008 were 1.5 times lower than those in 2007 probably due to higher mixing height (446 m), temperature (23.8°C),
and winds (0.36 ms−1). 相似文献
2.
Xunming Wang Caixia Zhang Hongtao Wang Guangqiang Qian Wanyin Luo Junfeng Lu Li Wang 《Environmental Earth Sciences》2011,64(4):1039-1050
A series of experiments to determine the direct emission of dust-sized particles from Gobi surfaces by clean wind (wind without
sand), and the potential for aeolian abrasion of Gobi surfaces and beds of gravel and mobile sand to produce fine (<100 μm)
and dust-sized (<10 μm, PM10) particles under sand-laden winds were conducted. Parent material was obtained from Gobi areas of the Ala Shan Plateau, the
region with high dust emissions in arid China. The fine particles produced by aeolian processes were collected using sand
traps and sieved the captured materials to exclude particles >100 μm in diameter and then PM10 by sedimentation was acquired. The Gobi surface provided most of the emitted fine particles during the initial dust emission
processes, but subsequently, release of the clay coatings of particles by abrasion becomes the dominant source of fine materials.
Under sand-laden winds, PM10 production rates produced by aeolian abrasion of Gobi surfaces ranged between 0.002 and 0.244% of blown materials. After
removal of sand, silt, or clay with low resistance to erosion from the Gobi surfaces by the wind, the PM10 production rates caused by aeolian abrasion were similar to those from gravel and sand beds. The results also indicated that
after the dust-sized particles with low resistance to erosion were removed, the production of dust-sized particles was unrelated
to wind velocity. Under aeolian processes, Gobi deserts in this region therefore play a major role in dust emissions from
arid and semiarid China. 相似文献
3.
Agriculture tillage can result in the high concentration of particulate matter with an aerodynamic diameter of 10 μm or less
(PM10) that can cause serious health problems. To understand how different agriculture tillage methods and wind conditions affect
the transmission and distribution of PM10, four model runs were performed using the high resolution Weather Research and Forecasting model coupled with a chemistry
component (WRF-Chem). In these runs, the observed emission rates under the conventional and combined tillage methods and different
wind speeds were inputted into WRF-Chem. The simulated results show that the WRF-Chem model can reasonably capture the meteorological
conditions at 500 m horizontal resolution over an agricultural field in California. The atmospheric concentration of particulate
matter increases significantly with an increase in the emission area. Substantial reduction, 50%, of aerosolized PM10 dust emissions can be achieved by using combined tillage, when considered under the same meteorological conditions when compared
to that caused by the conventional tillage method. Using the same conventional tillage emission rates, the lower velocity
wind produces larger airborne concentrations of pollutants than does a stronger wind. Conversely, a stronger wind distributes
the particulate matter over a larger area though with a diminished concentration when compared to a weaker wind. The atmospheric
concentration of particulate matter was found to have a direct relationship to its emission intensity and area and wind conditions. 相似文献
4.
Satya Prakash Sahu Manish Yadav Dhruti Sundar Pradhan Neha Rani Arka Jyoti Das 《Arabian Journal of Geosciences》2018,11(10):241
The objective of the study is to investigate spatio-temporal variations of PM10, PM2.5, and PM1 concentrations at seven residential sites, located in the vicinity of opencast coal projects, Basundhara Garjanbahal Area (BGA), India. Meteorological parameters such as wind speed, wind direction, relative humidity, and temperature were collected simultaneously with PM concentrations. Mean concentrations of PM10 in the range 215 ± 169–526 ± 412 μg m?3, PM2.5 in the range of 91 ± 79–297 ± 107 μg m?3, PM1 in the range of 68 ± 60–247 ± 84 μg m?3 were obtained. Coarse fractions (PM2.5–10) varied from 27 to 58% whereas fine fractions (PM1–2.5 and PM1) varied in the range of 51–73%. PM2.5 concentration was 41–74% of PM10 concentration, PM1 concentration was 31–62% of PM10 concentration, and PM1 concentration was 73–83% of PM2.5 concentration. Role of meteorology on PM concentrations was assessed using correlation analysis. Linear relationships were established among PM concentrations using least square regression analysis. With the aid of principal component analysis, two components were drawn out of eight variables, which represent more than 75% of variance. The results indicated that major sources of air pollutants (PM10, PM2.5, PM1, CO, CO2) at the residential sites are road dust raised by vehicular movement, spillage of coal generated during transportation, spontaneous combustion of coal, and biomass burning in village area. 相似文献
5.
Inorganic chemistry,granulometry and mineralogical characteristics of the dust fall over phosphate mine adjacent area,central Jordan 总被引:1,自引:0,他引:1
Eight selected heavy metals and phosphorus (Fe, Zn, Pb, Cu, Cr, Cd, Ni and P) were analyzed in the dust fall samples collected
from the surrounding areas adjacent to Al-Hisa phosphate mine central Jordan during summer 2008. The chemical analysis was
done using the ICP-AES, after being digested with (HNO3/HCl/HF) acid mixture, beside the identification of their mineral constituents using the XRD. Moreover, the particulate matter
(PM) size was investigated and divided into four fractions (PM2.5, PM2.5–10, PMC10–100 and PM>100). The PM10–PM100 were found to be the most abundant in the local atmosphere followed by PM2.5–PM10, while the respirable fraction (PM2.5) and giant fraction (PM>100) showed lower levels. The studied samples contain less PM2.5 and PM10 particulates (9.39 and 28.67), respectively, than samples located far from the mine area (blank samples) (17.32 and 51.7)
for PM2.5 and PM10, respectively. The meteorological effects, mainly the prevailing wind direction beside the distance to emission sources affect
the distribution of dust particle sizes. Heavy metal contents in studied samples are similar to some extent to those found
in Isa Town (Bahraian), which related to similar arid and low precipitation climatic conditions. The effect of phosphate mining
activities was obvious as indicated from the presence of apatite as the main mineral phase and the higher P contents. Moreover,
the studied samples contain higher Zn, Ni, Cu and to lesser extent Cr than blank samples. They exhibited a significant positive
correlation with P, as they are usually associated with the phosphate rocks. 相似文献
6.
Steeve Gréaux Yoshio Kono Norimasa Nishiyama Takehiro Kunimoto Kouhei Wada Tetsuo Irifune 《Physics and Chemistry of Minerals》2011,38(2):85-94
The thermoelastic parameters of synthetic Ca3Al2Si3O12 grossular garnet were examined in situ at high-pressure and high-temperature by energy dispersive X-ray diffraction, using
a Kawai-type multi-anvil press apparatus coupled with synchrotron radiation. Measurements have been conducted at pressures
up to 20 GPa and temperatures up to 1,650 K: this P, T range covered the entire high-P, T stability field of grossular garnet. The analysis of room temperature data yielded V
0,300 = 1,664 ± 2 ?3 and K
0 = 166 ± 3 GPa for K¢0 K^{\prime}_{0} fixed to 4.0. Fitting of our P–V–T data by means of the high-temperature third order Birch–Murnaghan or the Mie–Grüneisen–Debye thermal equations of state,
gives the thermoelastic parameters: (∂K
0,T
/∂T)
P
= −0.019 ± 0.001 GPa K−1 and α
0,T
= 2.62 ± 0.23 × 10−5 K−1, or γ
0 = 1.21 for fixed values q
0 = 1.0 and θ
0 = 823 (Isaak et al. Phys Chem Min19:106–120, 1992). From the comparison of fits from two different approaches, we propose to constrain the bulk modulus of grossular garnet
and its pressure derivative to K
T0 = 166 GPa and K¢T0 K^{\prime}_{T0} = 4.03–4.35. Present results are compared with previously determined thermoelastic properties of grossular-rich garnets. 相似文献
7.
Pascal Schouwink Ronald Miletich Angela Ullrich Ulrich A. Glasmacher Christina Trautmann Reinhard Neumann Barry P. Kohn 《Physics and Chemistry of Minerals》2010,37(6):371-387
Static elasticity measurements at high pressures were carried out on oriented fluorapatite single crystals, some of which
contained oriented amorphous ion tracks (ITs) implanted with relativistic Au ions (2.2 GeV) from the UNILAC linear accelerator
at GSI, Darmstadt. High-pressure experiments on irradiated and non-irradiated crystal sections were carried out in diamond-anvil
high-pressure cells under hydrostatic conditions. In situ single-crystal diffraction was performed to determine the high-precision
lattice parameters, simultaneously monitoring the widths of X-ray diffraction Bragg peaks. High-pressure Raman spectra were
analyzed with respect to the frequency shift and widths of bands, which correspond to the Raman-active vibrational modes of
the phosphate tetrahedra. Swift heavy ion irradiation was found to induce anisotropic lattice expansion and tensile strain
within the host lattice dependent on the ion-track orientation. The relatively low Grüneisen parameter for the ν
1b(A
g) mode, which has been assigned to originate from the volume fraction of the amorphous tracks, and the γ(ν
1a)/γ(ν
1b) ratio reveals compressive strain on the amorphous ITs. The comparative compressibilities for the host lattice reveal approximately
equivalent bulk moduli, but significantly different pressure derivatives (K
T = 88.4 ± 0.7 GPa, ∂K/∂P = 6.3 ± 0.3 for non-irradiated, K
T = 90.0 ± 1.7 GPa, ∂K/∂P = 3.8 ± 0.5 for irradiated samples). The axial compressibility moduli β
−1 reveal significant differences, which correlate with the ion-track orientation [ba - 1 \beta_{a}^{ - 1} = 240 ± 5 GPa, bc - 1 \beta_{c}^{ - 1} = 361 ± 14 GPa, ∂( ba - 1 ) \left( {\beta_{a}^{ - 1} } \right) /∂P = 11.3 ± 1.2, ∂( bc - 1 ) \left( {\beta_{c}^{ - 1} } \right) /∂P = 11.6 ± 3.4 for irradiation ⊥(100); 246 ± 9 GPa, 364 ± 57 GPa, 9.5 ± 2.9, 14.7 ± 14.1 for irradiation ⊥(001), 230.7 ± 3.6 GPa,
373.5 ± 5.1 GPa, 19.2 ± 1.4, 20.1 ± 1.8 for no irradiation]. Line widths of XRD Bragg peaks in irradiated apatites confirm
the strain of the host lattice, which appears to decrease with increasing pressure. By contrast, the bandwidths of Raman modes
increase with pressure, and this is attributed to increasing strain gradients on the length scale of the short-range order.
The investigations reveal considerable deviatoric stress on the [100]-oriented tracks due to the anisotropic elasticity, while
the compression is uniform for the directions perpendicular to the tracks, which are aligned parallel to the c-axis. This difference might be considered to control the diffusion properties related to the annealing kinetics and its observed
anisotropy, and hence to cause potential pressure effects on track-fading rates. 相似文献
8.
Shiho Hirotani Masao Ban Mitsuhiro Nakagawa 《Contributions to Mineralogy and Petrology》2009,157(6):709-734
Eruptive products of the Shirataka volcano (0.9–0.7 Ma) in NE Japan are calc-alkaline andesite–dacite, and are divisible into
six petrologic groups (G1–G6). Shirataka rocks possess mafic inclusions—basalt–basaltic andesite, except for G3 and G4. All
rocks show mixing and mingling of the mafic and silicic end-members, with trends defined by hosts and inclusions divided into
high-Cr and low-Cr types; both types coexist in G1, G2, and G5. Estimated mafic end-members are high-Cr (1120–1170°C, 48–51%
SiO2, olv ± cpx ± plg) and low-Cr type magmas (49–52% SiO2, cpx ± plg) except for the Sr isotopic composition. In contrast, the silicic end-members of both types have similar petrologic
features (790–840°C, 64–70% SiO2, hbl ± qtz ± px + plg). High-Cr type mafic and corresponding silicic end-members have lower 87Sr/86Sr ratios than the low-Cr ones in each group. The trace element model calculations suggest that the low-Cr type mafic end-member
magma is produced through ca. 20% fractional crystallization (olv ± cpx ± plg) from the high-Cr type one with assimilation
of granitoids (r = 0.02–0.05). The silicic magmas are producible through <30% partial remelting of previously emplaced basaltic magma with
assimilation of crustal components. The compositional difference between the low-K and medium-K basalts in the Shirataka volcano
is mainly attributed to the different degrees of the effect of subduction derived fluid by dehydration of phlogopite.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
9.
Yu Guo Han Pei Ling Yang Yuan Pei Luo Shu Mei Ren Li Xia Zhang Lei Xu 《Environmental Earth Sciences》2010,61(6):1197-1205
Drought is a great concern in agricultural production, because it restricts normal plant growth, brings about enormous economic
loss and deteriorates ecological environment. Proper use of super absorbent polymers (SAP) is helpful in the agricultural
and horticultural industry in arid and semi-arid areas, because SAP can ease the burden of water shortage. Because porosity
is one of the most important soil physical properties, it is a priority to study SAP to quantitatively express the swelling
of watered SAP-treated soil. This study was aimed to evaluate the bulk density curve of watered SAP-treated soil and to construct
and test the model for porosity change of watered SAP-treated soil. The results showed that the application of SAP can reduce
soil bulk density, improve soil permeability and cause soil swelling. In addition, using three factors, i.e., water content,
change in swelling ratio and SAP application rate, the paper constructed a model for porosity change of watered SAP-treated
soil, which is {ln[(P
m − P)(P
m − P
0)−1]} βP
0
θ = −η
0
cθ − η
0
a. This is a generic model. Two soil samples, namely, loam and sandy loam, were used to calculate the parameters and test the
model. The results of the model were satisfying, thus this model is reliable. 相似文献
10.
Daniel Mikeš 《Mathematical Geosciences》2011,43(5):593-606
Natural flocs in an estuary grow with increasing time, salinity, suspended particulate matter concentration, and with decreasing
turbulence. Although various theoretical and empirical functions for floc growth have been proposed in the literature, they
are all complex. It is argued in this study that there should be a simple and general function of floc size D against time t, salinity S, suspended particulate matter concentration C, microscale η, and biochemical composition M. Theory and experiments seem to corroborate that average floc size responds systematically to its drivers. Moreover, the
response is partly similar to all drivers: a lower plateau followed by a rise, and partly different: an upper plateau for t, S and a fall for C, η. Assuming drivers are independent, each curve is normalized around its rise. The drivers are joined into one variable X that holds each normalized driver with equal weight. The result is a function that gives floc size against this composite
variable X. This composite variable in turn is a function of ambient conditions and the function predicts floc size for any set of ambient
conditions. The case is presented here using linear segments, but eventually the logistic growth function is proposed. 相似文献
11.
The heat capacity at constant pressure, C
p, of chlorapatite [Ca5(PO4)3Cl – ClAp], and fluorapatite [Ca5(PO4)3F – FAp], as well as of 12 compositions along the chlorapatite–fluorapatite join have been measured using relaxation calorimetry
[heat capacity option of the physical properties measurement system (PPMS)] and differential scanning calorimetry (DSC) in
the temperature range 5–764 K. The chlor-fluorapatites were synthesized at 1,375–1,220°C from Ca3(PO4)2 using the CaF2–CaCl2 flux method. Most of the chlor-fluorapatite compositions could be measured directly as single crystals using the PPMS such
that they were attached to the sample platform of the calorimeter by a crystal face. However, the crystals were too small
for the crystal face to be polished. In such cases, where the sample coupling was not optimal, an empirical procedure was
developed to smoothly connect the PPMS to the DSC heat capacities around ambient T. The heat capacity of the end-members above 298 K can be represented by the polynomials: C
pClAp = 613.21 − 2,313.90T
−0.5 − 1.87964 × 107
T
−2 + 2.79925 × 109
T
−3 and C
pFAp = 681.24 − 4,621.73 × T
−0.5 − 6.38134 × 106
T
−2 + 7.38088 × 108
T
−3 (units, J mol−1 K−1). Their standard third-law entropy, derived from the low-temperature heat capacity measurements, is S° = 400.6 ± 1.6 J mol−1 K−1 for chlorapatite and S° = 383.2 ± 1.5 J mol−1 K−1 for fluorapatite. Positive excess heat capacities of mixing, ΔC
pex, occur in the chlorapatite–fluorapatite solid solution around 80 K (and to a lesser degree at 200 K) and are asymmetrically
distributed over the join reaching a maximum of 1.3 ± 0.3 J mol−1 K−1 for F-rich compositions. They are significant at these conditions exceeding the 2σ-uncertainty of the data. The excess entropy of mixing, ΔS
ex, at 298 K reaches positive values of 3–4 J mol−1 K−1 in the F-rich portion of the binary, is, however, not significantly different from zero across the join within its 2σ-uncertainty. 相似文献
12.
Feras Youssef Gunay Erpul Pieter Bogman Wim M. Cornelis Donald Gabriels 《Environmental Geology》2008,55(4):741-750
The trap efficiency of a catcher in wind erosion measurements plays a significant role, and in many cases suspension trap
efficiencies at high wind velocities are still unknown. The sediment trap efficiency generally changes with particles size
and with wind speed. In this study, the efficiency of Vaseline Slide (VS) and Modified Wilson and Cooke (MWAC) catchers were
determined with different sand particle sizes (<50, <75, 50–75, 200–400, and 400–500 μm) at a fixed wind speed (13.3 ms−1) and with different soil textures at different wind velocities (10.3, 12.3, and 14.3 ms−1) in the wind tunnel of the International Center for Eremology (ICE), Ghent University, Belgium. The traps were placed at
different heights (4, 6.5, 13, 20, 120, and 192 cm for VS and 1.5, 3, 5, 8, 11, and 30 cm for MWAC) to catch saltating and
suspended sediments in a 12-m long, 1.2-m wide and 3.2-m high working section of the wind tunnel. In the sand particle experiments,
the efficiency of the VS catcher was 92% for particles smaller than 50 μm and decreased with increasing particles size, falling
to 2.2% for 400–500 μm particle size at 13.4 ms−1. However, the MWAC’s efficiency was 0% for particles smaller than 50 μm and increased with increasing particle size to 69.5%
at 400–500 μm. In the experiments with different soil textures, the efficiency of each catcher significantly changed with
soil and with wind speed. It also considerably varied with the catchers: for instance, for sand (S), the MWAC efficiency was
very high (67.4, 113.4, and 90.5% at 10.3, 12.3, and 14.4 ms−1, respectively) while the efficiency of VS was relatively very low (5.2, 4.4, and 1.9% at 10.3, 12.3, and 14.4 ms−1, respectively). Results indicated that the efficiency depends critically on the particle size, type of catcher, and wind
speed, and these could be helpful to increase the robustness of wind erosion measurements. 相似文献
13.
The horizontal pullout capacity of a group of two vertical strip anchor plates placed along the same vertical plane in sand,
has been determined by using the lower bound finite element limit analysis. The effect of vertical spacing (S) between the
anchor plates on the magnitude of the total group horizontal failure load (PuT) has been determined for different combinations of H/B, δ/ϕ and ϕ. The magnitude of PuT has been obtained in terms of a group efficiency factor, ηγ, with respect to the failure load for a single vertical plate with the same H/B. The magnitude of ηγ becomes maximum corresponding to a certain critical S/B, which has been found to lie between 0.5 and 0.8. The value of ηγ for a given S/B has been found to become larger for greater values of H/B, ϕ, and δ. 相似文献
14.
Part I of this contribution (Gardés et al. in Contrib Mineral Petrol, 2010) reported time- and temperature-dependent experimental growth of polycrystalline forsterite-enstatite double layers between
single crystals of periclase and quartz, and enstatite single layers between forsterite and quartz. Both double and single
layers displayed growth rates decreasing with time and pronounced grain coarsening. Here, a model is presented for the growth
of the layers that couples grain boundary diffusion and grain coarsening to interpret the drop of the growth rates. It results
that the growth of the layers is such that (Δx)2 ∝ t
1−1/n
, where Δx is the layer thickness and n the grain coarsening exponent, as experimentally observed. It is shown that component transport occurs mainly by grain boundary
diffusion and that the contribution of volume diffusion is negligible. Assuming a value of 1 nm for the effective grain boundary
width, the following Arrhenius laws for MgO grain boundary diffusion are derived: log D
gb,0Fo (m2/s) = −2.71 ± 1.03 and E
gbFo = 329 ± 30 kJ/mol in forsterite and log D
gb,0En (m2/s) = 0.13 ± 1.31 and E
gbEn = 417 ± 38 kJ/mol in enstatite. The different activation energies are responsible for the changes in the enstatite/forsterite
thickness ratio with varying temperature. We show that significant biases are introduced if grain boundary diffusion-controlled
rim growth is modelled assuming constant bulk diffusivities so that differences in activation energies of more than 100 kJ/mol
may arise. It is thus important to consider grain coarsening when modelling layered reaction zones because they are usually
polycrystalline and controlled by grain boundary transport. 相似文献
15.
Impact of internal waves on the acoustic field at a coastal station off Paradeep,east coast of India
Internal Wave (IW) characteristics and the impact of IW on acoustic field have been studied utilizing the hourly time series
of temperature and salinity data collected at a coastal site off Paradeep (north Bay of Bengal) during 24–25 October 2008.
The IW characteristics, viz. period (t
per
), velocity (C
vel
), wavelength (L), and wave numbers (k), are found to be 2.133–34.72 h, 0.135 km h−1, 0.37–6.2 km and 2.70–0.16 cycles km−1, respectively. The semi-diurnal tidal forces are predominant than diurnal as well as at other frequencies and its contribution
is about 64% towards the total potential energy (E
0 = 3.34 J m−2). Sound velocity perturbations with space and time in the presence of IW field are examined from Garrettt-Munk (GM) model.
Transmission loss anomaly for optimized source-receiver configuration at the depth of 53 m and range of 9 km has been computed
from acoustic modelling. The loss in the acoustic transmission is found to be 38.4 dB in the presence of low-frequency IW
field. 相似文献
16.
H. Morishima E. Ohtani T. Kato T. Kubo A. Suzuki T. Kikegawa O. Shimomura 《Physics and Chemistry of Minerals》1999,27(1):3-10
The high-pressure and temperature equation of state of majorite solid solution, Mj0.8Py0.2, was determined up to 23 GPa and 773 K with energy-dispersive synchrotron X-ray diffraction at high pressure and high temperature
using the single- and double-stage configurations of the multianvil apparatuses, MAX80 and 90. The X-ray diffraction data
of the majorite sample were analyzed using the WPPD (whole-powder-pattern decomposition) method to obtain the lattice parameters. A least-squares fitting using the third-order Birch-Murnaghan equation
of state yields the isothermal bulk modulus, K
T0
= 156 GPa, its pressure derivative, K′ = 4.4(±0.3), and temperature derivative (∂K
T
/∂T)
P
= −1.9(±0.3)× 10−2 GPa/K, assuming that the thermal expansion coefficient is similar to that of pyrope-almandine solid solution.
Received: 5 October 1998 / Revised, accepted: 24 June 1999 相似文献
17.
The in situ electrical conductivity of hydrous garnet samples (Py20Alm76Grs4–Py73Alm14Grs13) was determined at pressures of 1.0–4.0 GPa and temperatures of 873–1273 K in the YJ-3000t apparatus using a Solartron-1260
impedance/gain-phase analyzer for various chemical compositions and oxygen fugacities. The oxygen fugacity was controlled
by five solid-state oxygen buffers (Fe2O3 + Fe3O4, Ni + NiO, Fe + Fe3O4, Fe + FeO, and Mo + MoO2). Experimental results indicate that within a frequency range from 10−2 to 106 Hz, electrical conductivity is strongly dependent on signal frequency. Electrical conductivity shows an Arrhenius increase
with temperature. At 2.0 GPa, the electrical conductivity of anhydrous garnet single crystals with various chemical compositions
(Py20Alm76Grs4, Py30Alm67Grs3, Py56Alm43Grs1, and Py73Alm14Grs13) decreases with increasing pyrope component (Py). With increasing oxygen fugacity, the electrical conductivity of dry Py73Alm14Grs13 garnet single crystal shows an increase, whereas that of a hydrous sample with 465 ppm water shows a decrease, both following
a power law (exponents of 0.061 and −0.071, respectively). With increasing pressure, the electrical conductivity of this hydrous
garnet increases, along with the pre-exponential factors, and the activation energy and activation volume of hydrous samples
are 0.7731 ± 0.0041 eV and −1.4 ± 0.15 cm3/mol, respectively. The results show that small hopping polarons
( \textFe\textMg · ) \left( {{\text{Fe}}_{\text{Mg}}^{ \cdot } } \right) and protons (
\textH · {\text{H}}^{ \cdot } ) are the dominant conduction mechanisms for dry and wet garnet single crystals, respectively. Based on these results and
the effective medium theory, we established the electrical conductivity of an eclogite model with different mineral contents
at high temperatures and high pressures, thereby providing constraints on the inversion of field magnetotelluric sounding
results in future studies. 相似文献
18.
Sensitivity of high-resolution tropical cyclone intensity forecasts to surface flux parameterization
Chi-Sann Liou 《Natural Hazards》2007,41(3):387-399
Surface flux parameterization schemes used in current dynamic models are primarily based upon measurements at low and moderate
wind speeds. Recent studies show that these parameterization schemes may be incorrect at high wind speeds (e.g., tropical
cyclone forecasts). Five high-resolution numerical model experiments are designed to assess the sensitivity of tropical cyclone
intensity forecasts to changes in the surface flux parameterization. The sensitivity experiments are conducted by running
48 h forecasts of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) for six selected tropical cyclones with
individual modifications to surface flux calculation that include: (1) limiting the surface stress for wind speeds greater
than 33 m s−1, or 64 knots (kt); (2) computing the stress at the top of the model bottom grid layer (MBGL) by averaging results from surface
layer similarity and turbulence mixing parameterization for wind speeds greater than 33 m s−1; (3) increasing the roughness lengths for heat and moisture transfer by a factor of ten; (4) setting the roughness lengths
for heat and moisture transfer to 1/10 of the momentum roughness length; and (5) cooling the sea surface temperature (SST)
by a prescribed rate at high winds. Averaged responses for the six storms to these sensitivity tests show that: (i) the limit
on surface stress at high winds significantly increases the cyclone intensity in 48 h forecasts; (ii) the averaged surface
layer stress at high winds increases the cyclone intensity but to a much lesser degree than limiting the surface stress; (iii)
large increases in the roughness lengths for heat and moisture transfer are needed to significantly impact the intensity forecast;
(iv) the different roughness length formula for surface transfer coefficients notably increases C
h/C
d ratio from 0.59 to 0.79 for 25 m s−1 and 0.41 to 0.75 for 50 m s−1 that significantly increases the predicted cyclone intensity; and (v) cooling of the SST by −5.8°C in 48 h reduces the maximum
surface wind speed by −32 kt, or 16.5 m s−1, at 48 h forecast. These results suggest that a surface flux parameterization scheme suitable for tropical cyclone intensity
forecast must correctly model the leveling-off character of surface stress and C
h/C
d ratio at high winds. All modifications to surface flux calculation have little influence on 48 h track forecasts, even though
they may significantly impact the intensity forecasts.
相似文献
Chi-Sann LiouEmail: |
19.
Matteo Alvaro Fernando Cámara M. Chiara Domeneghetti Fabrizio Nestola Vittorio Tazzoli 《Contributions to Mineralogy and Petrology》2011,162(3):599-613
A natural Ca-poor pigeonite (Wo6En76Fs18) from the ureilite meteorite sample PCA82506-3, free of exsolved augite, was studied by in situ high-temperature single-crystal
X-ray diffraction. The sample, monoclinic P21/c, was annealed up to 1,093°C to induce a phase transition from P21/c to C2/c symmetry. The variation with increasing temperature of the lattice parameters and of the intensity of the b-type reflections (h + k = 2n + 1, present only in the P21/c phase) showed a displacive phase transition P21/c to C2/c at a transition temperature T
Tr = 944°C, first order in character. The Fe–Mg exchange kinetics was studied by ex situ single-crystal X-ray diffraction in
a range of temperatures between the closure temperature of the Fe–Mg exchange reaction and the transition temperature. Isothermal
disordering annealing experiments, using the IW buffer, were performed on three crystals at 790, 840 and 865°C. Linear regression
of ln k
D versus 1/T yielded the following equation:
ln k\textD = - 3717( ±416)/T(K) + 1.290( ±0.378); (R2 = 0.988) \ln \,k_{\text{D}} = - 3717( \pm 416)/T(K) + 1.290( \pm 0.378);\quad (R^{2} = 0.988) . The closure temperature (T
c) calculated using this equation was ∼740(±30)°C. Analysis of the kinetic data carried out taking into account the e.s.d.'s
of the atomic fractions used to define the Fe–Mg degree of order, performed according to Mueller’s model, allowed us to retrieve
the disordering rate constants C
0
K
dis+ for all three temperatures yielding the following Arrhenius relation:
ln( C0 K\textdis + ) = ln K0 - Q/(RT) = 20.99( ±3.74) - 26406( ±4165)/T(K); (R2 = 0.988) \ln \left( {C_{0} K_{\text{dis}}^{ + } } \right) = \ln \,K_{0} - Q/(RT) = 20.99( \pm 3.74) - 26406( \pm 4165)/T(K);\quad (R^{2} = 0.988) . An activation energy of 52.5(±4) kcal/mol for the Fe–Mg exchange process was obtained. The above relation was used to calculate
the following Arrhenius relation modified as a function of X
Fe (in the range of X
Fe = 0.20–0.50):
ln( C0 K\textdis + ) = (21.185 - 1.47X\textFe ) - \frac(27267 - 4170X\textFe )T(K) \ln \left( {C_{0} K_{\text{dis}}^{ + } } \right) = (21.185 - 1.47X_{\text{Fe}} ) - {\frac{{(27267 - 4170X_{\text{Fe}} )}}{T(K)}} . The cooling time constant, η = 6 × 10−1 K−1 year−1 calculated on the PCA82506-3 sample, provided a cooling rate of the order of 1°C/min consistent with the extremely fast late
cooling history of the ureilite parent body after impact excavation. 相似文献
20.
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