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1.
Pickering & Hiscott, (1985) have demonstrated amply the presence of reverse-flow units within the thick-bedded calcareous wacke (TCW) beds of the turbiditic Cloridorme Formation (Middle Ordovician, Gaspé Peninsula, Quebec, Canada). These reverse-flow units are underlain and overlain by units which reveal flow in the primary (obverse) direction. In this paper, a model is proposed for this reverse flow, based on the probable nature of the primary turbidity flow. It appears that the initial flow was highly elongated (thickness h? length L), with h～ 500 m, velocity U～ 2 m s-1 and sediment concentration C～ 1·25%o. The rate of momentum loss of the flow is estimated by means of a useful parameter which we call the ‘drag distance’, symbol dD, defined by where h and L are the thickness and length of the flow, respectively; cCd is a combined drag coefficient representing friction on the bottom and at the upper interface; and fCd is a form-drag coefficient related to the shape and size of the head. dD is the distance travelled by a current of constant h and L, flowing over a horizontal bottom and obeying a quadratic friction law, for an e-fold reduction in velocity. Simple considerations, confirmed by our own experiments (described in this paper), show that such an elongated turbidity current cannot be reflected as a whole from an adverse slope: when the nose of the current reaches the slope, it forms a hump, which surges backwards and sooner or later breaks up into a series of internal solitons. The latter, probably numbering 4–7, will cause reverse flow at a given point as they pass by, provided that the residual velocity in the tail is not too great. Flow in the original (obverse) direction will be re-established after the passage of the solitons. Quiescent periods in front of, between and behind the solitons, when soliton-associated currents cancelled out the residual obverse flow, would allow the deposition of thin mud-drapes. Additional flow reversals observed in a few of the TCW beds cannot be explained readily by the re-passage of solitons, since wave breaking at the ends of the basin would cause massive energy loss; internal seiches are the preferred explanation for these later reversals. 相似文献
2.
一种页岩含气性热演化规律研究的模拟实验方法 总被引：2，自引：1，他引：1
目前针对页岩气赋存规律研究的热模拟实验主要是沿袭常规油气热模拟方法,以粉末态样品开展模拟,研究对象为岩石生成并排出的烃类气体,这种模拟方式未明确页岩气的实质为"滞留气",并且模拟后样品无法开展扫描电镜分析,不能确定岩石孔隙结构变化规律。本文通过石英玻璃管封装块状样开展页岩生烃热模拟实验,并结合一套数据处理方法,尝试建立了一种适合页岩气研究的热模拟实验方法,研究泥页岩在不同演化阶段(Ro范围为0.596%~2.143%)不同赋存状态气体的含量以及岩石微观孔隙特征的变化情况。结果表明,泥岩及油页岩样品的排出气及解析气含量在高成熟度阶段(400℃以后)有明显增加的趋势,结合扫描电镜微观结构分析显示这是由于有机质生气量以及无机孔隙均有增加。本方法可以研究页岩热演化过程中不同赋存状态气体含量及微观孔隙结构的变化,为页岩气勘探开发提供了一种可参考的方法。 相似文献
3.
The paper contains the results of extensive single-point hot-wire and resistance-thermometer measurements in a wall jet on a heated concave wall with an external free stream. It is found that the turbulence in the inner (wall) and outer layers is sensitive to the distortion produced by the curved wall, broadly confirming current views of these effects. The effect on the turbulence of streamline curvature is stabilising in the outer layer, destabilising in the inner. Consequently the point of zero shear stress is closer to the point of maximum mean velocity than in flat and convex wall jets with which these new results are compared. The rate of growth is about 80% of that of the equivalent flat wall flow, and about half that of the convex wall flow. Changes in the wall shear stress and heat flux, which are increased relative to the flat wall flow, are significant but less than the changes in the corresponding convex wall flow. The greatest changes occur in the triple products.List of Symbols
c
f
skin friction coefficient, 2
w
/ U
M
2
-
q
2
u
2 +v
2+w
2
-
R
radius of curvature of wall
-
r
radius of curvature
-
St
Stanton number,-q
w
/c
p
U
M
(T
–T
w
)
-
T
mean temperature
-
U
streamwise mean velocity
-
U
J
initial wall-jet velocity
-
U
1
initial free-stream velocity
-
U
0
U
M
–U
PW
-
u, v, w
fluctuating velocity components
-
x, y
distances measured along and normal to the wall
-
y
0.5,y
M
wall-jet thicknesses defined in the text
-
y
S
,y
T
wall-jet thicknesses defined in the text
-
T
T
W
–T
-
shear-layer thickness
-
2
momentum thickness
-
temperature fluctuation
-
M
point of maximum velocity
-
P
potential flow
-
s
point of zero shear stress
- W
wall value
-
free stream value 相似文献
4.
Measurements are described of the geometry of ripples formed on beds of sand exposed to a steady current at right angles to an oscillatory flow. Four different sands were studied. The oscillation was produced by an oscillating tray set into the bed of a steady-flow flume. It was observed that straight-crested ripples formed by oscillatory flow would usually develop a ‘serpentine’ form when the superimposed steady current exceeded a certain limit. For amplitudes of the tray velocity U∞ less than about 0.38 m s-1 this limit corresponded to U∞/ū*c>31, where ū*c is the shear velocity measured just upstream of the oscillating tray. It is suggested that the serpentine form is caused by the interaction of vortices carried back and forth between adjacent ripples. On this assumption, the wavelength of the serpentine form would be proportional to the product of period of oscillation and near-bed steady current velocity. The present measurements appear to support this hypothesis although there is also evidence that the wavelength is influenced by preferred spacing patterns between vortices. The measurements also show the ratio of the amplitude of the serpentine form to its wavelength to be approximately constant. Empirical relationships are derived relating ripple geometry to flow and sediment properties. It is observed that the influence of Reynolds number and sediment properties on the geometry is very weak. It is suggested that this is typical of ripples formed with relatively low sediment transport rates. It is also found that, under the present experimental conditions, the ripple spacing in the direction of oscillation is almost independent of the magnitude of the steady current and in close agreement with the wavelengths previously measured in an oscillating water tunnel. This suggests that the additional inertia effects associated with oscillating tray rigs were not sufficient to affect bed geometry under the present test conditions. 相似文献
5.
During experiments with digital stations in the period 1985–1987, twenty five earthquakes with magnitudes m
b
in the range 2.9 to 4.8 and epicentres located within the area 36°–42.3° (N) and 4.5°–13.6° (W) were recorded at Montemor (MOE) and Montachique (MTH). The three-component recordings were obtained by Geotech S13 instruments with 1 second period. A preliminary analysis of the recordings consisted in the determination of amplitudes and spectral contents of P and S waves, and led to the following observations: (1) The attenuation of waves is expressed by the equation V = exp(C
2).R
C
1. exp(C
3.M), where V stands for acceleration, velocity or displacement; M-magnitude; R-focal distance; C
1, C
2 and C
3 are constants to be obtained by least square fitting. The application of this equation led to C
1 of the order 1.7 for displacement, 1.8 for velocity and 2.0 for acceleration, with an average mean square error 0.8. (2) The ratios L/T (longitudinal/transversal amplitudes), for velocity and displacement, showed a tendency to reduce with increasing focal distance, being 2 for short distances (<50 km) and 1 for long distances (400 km). (3) The ratios S/P (S-wave/P-wave amplitudes), although with a large dispersion, showed a slight tendency for increasing with focal distance. (4) The predominant frequencies also showed a slight tendency to decrease with increasing focal distance and with magnitude. (5) The dependence of C
1 with frequency (3 to 12 Hz) is well behaved from 0.95 to 1.75 (for the velocity trace). 相似文献
6.
Malcolm O. Green 《Sedimentology》1999,46(3):427-441
Sediment initial-motion theories predict the flow conditions that coincide with onset of sediment motion, but usually the most that can be determined from burst-sampled field data is whether or not sediment was in motion. Furthermore, initial-motion theories are usually based on regular-wave laboratory data, with little or no guidance given on how such theories are to be transferred to the real world of irregular waves. A field dataset obtained from the zone of wave shoaling beyond the surfzone is used to compare the performance of three initial-motion theories in a way that takes explicit account of wave irregularity and the limitations of burst sampling. The dataset comprises video images of the seabed and measurements of waves, currents and suspended sediment. The initial-motion theories tested were Komar & Miller's (1975 , J. Sedim. Petrol ., 45, 362–367) 'wave-orbital-speed' theory, a 'wave-stress' theory, and a 'wave-plus-current-stress' theory. Fourteen transitions from no sediment motion to sediment motion were observed, but not all of those represented a challenging test of theory. Using the criterion that the best theory is the one that minimizes errors in classifying bursts as 'no sediment motion' or 'sediment in motion', Komar & Miller's (1975 ) theory was found to perform the best when waves were characterized by significant wave height and mean spectral period, both of which can be estimated directly from pressure data alone. Komar and Miller's theory was better at predicting the onset of extended transport events, which occurred during confused seas, rather than the transition back to moribund seabed under clean swell at the end of such events. The conclusion regarding best theory is dependent on the choice of scales used to characterize wave motion. The way forward therefore is to standardize and define terms precisely. 相似文献
7.
海啸波作用下泥沙运动——Ⅰ.岸滩剖面变化分析 总被引：1，自引：0，他引：1
在波浪水槽实验的基础上,对海啸波作用下的岸滩剖面演变规律开展研究。实验采用1/10~1/20的组合坡度,考虑3种不同的水深,选取N波作为入射波,同时采用规则波和非规则波进行对比研究。实验对波高、波浪的上爬、回落和水跃过程、每个波作用后的地形进行了测量和记录。研究结果表明,水动力特性的不同造成了N波与规则波和不规则波作用下不同的岸滩剖面演变特点。N波作用下发生了明显的岸滩冲刷和淤积,水流回落时滩肩发生冲刷,高速薄层回流和出渗水流作用是滩肩冲刷的主要原因,离岸区水跃发生水流挟沙力降低,泥沙淤积呈沙坝剖面。 相似文献
8.
PETER J. TALLING DOUGLAS G. MASSON ESTHER J. SUMNER GIUSEPPE MALGESINI 《Sedimentology》2012,59(7):1937-2003
Submarine sediment density flows are one of the most important processes for moving sediment across our planet, yet they are extremely difficult to monitor directly. The speed of long run‐out submarine density flows has been measured directly in just five locations worldwide and their sediment concentration has never been measured directly. The only record of most density flows is their sediment deposit. This article summarizes the processes by which density flows deposit sediment and proposes a new single classification for the resulting types of deposit. Colloidal properties of fine cohesive mud ensure that mud deposition is complex, and large volumes of mud can sometimes pond or drain‐back for long distances into basinal lows. Deposition of ungraded mud (TE‐3) most probably finally results from en masse consolidation in relatively thin and dense flows, although initial size sorting of mud indicates earlier stages of dilute and expanded flow. Graded mud (TE‐2) and finely laminated mud (TE‐1) most probably result from floc settling at lower mud concentrations. Grain‐size breaks beneath mud intervals are commonplace, and record bypass of intermediate grain sizes due to colloidal mud behaviour. Planar‐laminated (TD) and ripple cross‐laminated (TC) non‐cohesive silt or fine sand is deposited by dilute flow, and the external deposit shape is consistent with previous models of spatial decelerating (dissipative) dilute flow. A grain‐size break beneath the ripple cross‐laminated (TC) interval is common, and records a period of sediment reworking (sometimes into dunes) or bypass. Finely planar‐laminated sand can be deposited by low‐amplitude bed waves in dilute flow (TB‐1), but it is most likely to be deposited mainly by high‐concentration near‐bed layers beneath high‐density flows (TB‐2). More widely spaced planar lamination (TB‐3) occurs beneath massive clean sand (TA), and is also formed by high‐density turbidity currents. High‐density turbidite deposits (TA, TB‐2 and TB‐3) have a tabular shape consistent with hindered settling, and are typically overlain by a more extensive drape of low‐density turbidite (TD and TC,). This core and drape shape suggests that events sometimes comprise two distinct flow components. Massive clean sand is less commonly deposited en masse by liquefied debris flow (DCS), in which case the clean sand is ungraded or has a patchy grain‐size texture. Clean‐sand debrites can extend for several tens of kilometres before pinching out abruptly. Up‐current transitions suggest that clean‐sand debris flows sometimes form via transformation from high‐density turbidity currents. Cohesive debris flows can deposit three types of ungraded muddy sand that may contain clasts. Thick cohesive debrites tend to occur in more proximal settings and extend from an initial slope failure. Thinner and highly mobile low‐strength cohesive debris flows produce extensive deposits restricted to distal areas. These low‐strength debris flows may contain clasts and travel long distances (DM‐2), or result from more local flow transformation due to turbulence damping by cohesive mud (DM‐1). Mapping of individual flow deposits (beds) emphasizes how a single event can contain several flow types, with transformations between flow types. Flow transformation may be from dilute to dense flow, as well as from dense to dilute flow. Flow state, deposit type and flow transformation are strongly dependent on the volume fraction of cohesive fine mud within a flow. Recent field observations show significant deviations from previous widely cited models, and many hypotheses linking flow type to deposit type are poorly tested. There is much still to learn about these remarkable flows. 相似文献
9.
The crystal structure of akermanite, Ca2Mg-Si2O7, consists of mixed tetrahedral sheets formed by [MgO4] tetrahedra and [Si2O7] groups interleaved along the c axis with Ca2+ ions in eight-fold coordination. Above 358 K, the structure is tetragonal
, and below it is incommensurate with modulations parallel to [110] and
. The elastic stiffness moduli, C
ij of the incommensurate phase at room temperature were measured from wave velocities in the 20–75 MHz carrier frequency range by the ultrasonic phase comparison method using optically clear synthetic single crystal plates (3×3×2 mm) oriented parallel to (100), (001), (110) and (101) planes. The C
ij values (GPa) are: C
11 159.40, C
33 149.43, C
44 30.26, C
66 58.10, C
12 76.58 and C
13 57.80. In (010) and (001) planes, the compressional modulus, V
2(L) from the longitudinal wave, L is considerably larger than the shear moduli, V
2(T1, T
2) both from the in-plane and perpendicular-to-plane shear waves, T
1 and T
2. The relatively small values of the shear moduli indicate the ease of tetrahedral rotations in response to in-plane and perpendicular-to-plane shears and may provide preconditions for structural changes involving shear-type atomic movements. 相似文献
10.
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
11.
Corinne Sonzogni Edouard Bard Frauke Rostek Denis Dollfus Antoni Rosell-Melé Geoffrey Eglinton 《Quaternary Research》1997,47(3):344-355
We compare alkenone unsaturation ratios measured on recent sediments from the Indian Ocean (20°N–45°S) with modern sea oceanographic parameters. For each of the core sites we estimated average seasonal cycles of sea surface temperature (SST) and salinity, which we then weighted with the seasonal productivity cycle derived from chlorophyll satellite imagery. The unsaturation index (U37K′) ranges from 0.2 to 1 and correlates with water temperature but not with salinity. TheU37K′versus SST relationship for Indian Ocean sediments (U37K′= 0.033 SST + 0.05) is similar to what has been observed for core tops from the Pacific and Atlantic oceans and the Black Sea. A global compilation for core tops givesU37K′= 0.031 T + 0.084 (R= 0.98), which is close to a previously reported calibration based on particulate organic matter from the water column. For temperatures between 24° and 29°C, however, the slope seems to decrease to about 0.02U37K′unit/°C. For Indian Ocean core tops, the ratios of total C37alkenones/total C38alkenones and the slope of theU37K′-SST relationship are similar to those previously observed for cultures ofEmiliania huxleyibut different from those previously published forGephyrocapsa oceanica.EitherE. huxleyiis a major producer of alkenones in the Indian Ocean or strains ofG. oceanicaliving in the northern Indian Ocean behave differently from the one cultured. In contrast with coccolithophorid assemblages, the ratios of C37alkenones to total C38alkenones lack clear geographic pattern in the Indian Ocean. 相似文献
12.
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
13.
David A. Jay Philip M. Orton Thomas Chisholm Douglas J. Wilson Annika M. V. Fain 《Estuaries and Coasts》2007,30(6):1106-1125
Estuarine turbidity maxima (ETM) retain suspended particulate matter (SPM) through advection, settling, aggregation, and nonlinearities
in bed processes, but the relative importance of these processes varies strongly between systems. Observations from two strongly
advective systems (the Columbia and Fraser Rivers) are used to investigate seasonal cycles of SPM retention and the effects
of very high flows. Results for the Fraser and Columbia plus literature values for 13 other estuaries illustrate the applicability
of scaling parameters and the response of ETM phenomena to a range of river flow (U
r
) levels and tidal forcing. The most efficient trapping (represented by Trapping EfficiencyE, the ratio of maximum ETM concentration to the source SPM concentration) occurs for low ratios of river flow to tidal current
amplitude (UT), represented by low values of the Supply number Sr.E in the Columbia is found to be maximal in a null zone where advection or tidal asymmetry (represented by Advection numberA) is weak(A ∼ 0). The ratio of aggregation to disaggregation (the Floc number Θ) is maximal on neap tides, while the ratio of erosion to
deposition (the Erosion number P) is maximal on spring tides. The ratio of settling velocity to vertical mixing (Rouse numberP) is relatively constant in the Columbia ETM(P ∼ 0.7), because particle settling velocity and turbulence levels adjust together. Assuming that this result applies broadly,
scaling variables and data are combined to express ETM properties in terms of the friction velocity (U*),U
r
, andU
T
, allowing a considerable simplification of the parameters used to describe ETM. 相似文献
14.
The α − β transition of quartz was successfully observed with using a single sample by means of the rectangular parallelepiped
resonance (RPR) method. An oriented rectangular parallelepiped of α-quartz single crystal was prepared and the resonant frequencies
of 30–11 vibrational modes were measured from room temperature to 700°C. The softening of quartz crystal was observed as the
significant reduction of resonant frequencies near the α–β transition. The present study is the first application of the RPR
method to the study of phase transition. The complete set of elastic constants of α- and β-quartz were determined as a function
of temperature by the least-squares inversion of the measured frequency data obtained by a single run. This is a merit yielded
by the RPR method. It is shown near the α − β transition in both α- and β-quartz that the elastic parameters decrease proportionally
to |T−T
0|−n
, where T is temperature and T
0 is the transition temperature, 573.0°C for α-quartz and 574.3°C for β-quartz. It was also seen that linear incompressibilities
K
1 = (C
11
+C
12
+C
13)/3 and K
3 = (C
33
+2C
13)/3 decrease rapidly toward the transition, whereas, shear moduli C
44, C
S1 = (C
11
+C
33
-2C
13)/4 and C
S3 = (C
11
-C
12)/2 = C
66 decrease only slightly. The shear modulus C
S3 = C
66 increased slightly in α-quartz. The elastic properties of isotropic aggregate of quartz were calculated, and it is shown
that the longitudinal wave velocity significantly decreases at the α − β transition, whereas, the shear wave velocity decreases
only slightly. 相似文献
15.
While the transport of sediment by unidirectional currents or by oscillatory (wave-induced) currents has been investigated, very little attention has been paid to the problem of the threshold of transport under the two mechanisms combined. Studies were carried out using cohesionless sand-sized (mean diameters: 142, 363, 771 and 1134 μm) quartz grains in a unidirectional flume, within which an oscillatory carriage had been installed. The experiments were carried out under unidirectional velocities ranging between 0 and 27 cm s-1, combined with simulated wave-induced currents (at periods of 5 and 15 s) ranging from 0 to 35 cm s-1. The threshold of transport was assessed, by visual observation, using the Yalin Criterion for unidirectional flow. This criterion permitted critical conditions to be estimated subjectively by observation of incipient transport from the flat beds. The results indicated the dependence of the critical threshold velocity combination on grain size and wave period. Thresholds tend to increase with increasing grain size or decreasing period. The grain-size dependence is predictable from existing empirical relationships for the separate mechanisms; statistical fluctuations in near-bed stress (bursting) however, are invoked to explain the wave period dependence. The latter effect acts in a reverse manner for wave and current combinations than for waves alone. Graphs are presented, relating grain size to critical threshold velocity combinations, to aid in the sedimentological interpretation of field data. 相似文献
16.
Hong Lu Tengshui Chen Kliti Grice Paul Greenwood Ping’an Peng Guoying Sheng 《Organic Geochemistry》2009,40(8):902-911
An unusual series of C22–C27 monounsaturated sterenes and C24–C30 tetracyclic terpanes (17,21-secohopanes) were detected in relatively high concentrations in an immature evaporitic marl sediment of the Jinxian Sag, Bohai Bay Basin, North China. The site of unsaturation in these novel sterenes is assigned tentatively to the D ring on the basis of mass spectral interpretation, which also distinguishes them from reported unsaturated sterenes. Other hydrocarbon biomarker or stable isotope characteristics are indicative of microbial (e.g. methyl hopanes), phytoplankton or higher plant (depleted δ13C values of isoprenoids and hopanes) inputs and an anoxic carbonate depositional environment (hexacyclic hopanes; tetracyclic terpanes). The hydrocarbon composition showed no obvious biodegradation and the relatively high concentration of unsaturated terpenoids (e.g. gammacerene) and low values of other established maturity parameters (Ts/Tm = 0.23; Ro = 0.44%; Tmax = 417 °C), are consistent with sediments of low maturity. The novel, low molecular weight sterenes and the tetracyclic terpanes may be early diagenetic products of microbial sources in a carbonate environment. 相似文献
17.
Crystals of hydronium jarosite were synthesized by hydrothermal treatment of Fe(III)–SO4 solutions. Single-crystal XRD refinement with R1=0.0232 for the unique observed reflections (|Fo| > 4F) and wR2=0.0451 for all data gave a=7.3559(8) Å, c=17.019(3) Å, Vo=160.11(4) cm3, and fractional positions for all atoms except the H in the H3O groups. The chemical composition of this sample is described by the formula (H3O)0.91Fe2.91(SO4)2[(OH)5.64(H2O)0.18]. The enthalpy of formation (Hof) is –3694.5 ± 4.6 kJ mol–1, calculated from acid (5.0 N HCl) solution calorimetry data for hydronium jarosite, -FeOOH, MgO, H2O, and -MgSO4. The entropy at standard temperature and pressure (So) is 438.9±0.7 J mol–1 K–1, calculated from adiabatic and semi-adiabatic calorimetry data. The heat capacity (Cp) data between 273 and 400 K were fitted to a Maier-Kelley polynomial Cp(T in K)=280.6 + 0.6149T–3199700T–2. The Gibbs free energy of formation is –3162.2 ± 4.6 kJ mol–1. Speciation and activity calculations for Fe(III)–SO4 solutions show that these new thermodynamic data reproduce the results of solubility experiments with hydronium jarosite. A spin-glass freezing transition was manifested as a broad anomaly in the Cp data, and as a broad maximum in the zero-field-cooled magnetic susceptibility data at 16.5 K. Another anomaly in Cp, below 0.7 K, has been tentatively attributed to spin cluster tunneling. A set of thermodynamic values for an ideal composition end member (H3O)Fe3(SO4)2(OH)6 was estimated: Gof= –3226.4 ± 4.6 kJ mol–1, Hof=–3770.2 ± 4.6 kJ mol–1, So=448.2 ± 0.7 J mol–1 K–1, Cp (T in K)=287.2 + 0.6281T–3286000T–2 (between 273 and 400 K). 相似文献
18.
In the early stages of wave growth it is seen that wave heights are underestimated by presently available models especially in a low wind regime. Parametric wind-sea relationships of significant wave height (H2) and zero-crossing period (T 2) for slight to moderate sea-states were proposed earlier on an analysis of wind and wave data. This model is based on the concept of time delay between the wind speed (U) and wave evolution process. It is simple and requires less computational effort compared to the spectral method. The present paper attempts to test and evaluate the performance of the proposed model with additional field data of wind and waves measured off the Indian coast. MeasuredU,H 2, andT 2 ranged between 1 and 15 m/s, 0·5 and 2·7 m and 4 and 10 s respectively. By and large, the comparison between model output and field observations are encouraging. A hindcast study was carried out earlier using a spectral wave prediction model (TOHOKU) for Indian Seas using field measurements which include the data sets utilized in this study. Comparison between these two models reveals a good agreement. 相似文献
19.
基于波浪边界层理论及单向流泥沙起动Shields曲线,推证出波浪泥沙起动Shields曲线;基于波流边界层理论,提出表述波流边界层动力特征的波流比因子X及非线性作用因子Y,并建立了Y与X的相关关系;在此基础之上,结合单向流及波浪泥沙起动Shields曲线,推证出波流共同作用下泥沙起动Shields曲线。结果表明:波浪泥沙起动Shields曲线在层流区与单向流光滑紊流区曲线保持一致,粗糙紊流区与单向流粗糙紊流区曲线保持一致,过渡区线型为折线,由层流区及粗糙紊流区曲线延长交汇获得;X及Y能够合理地表征波流边界层动力对比特征及非线性作用特征;波流泥沙起动Shields曲线介于波浪及单向流泥沙起动Shields曲线之间,随着波流比因子X的不同,依据非线性作用因子Y,自动在波浪及单向流泥沙起动Shields曲线之间非线性过渡。建立的波流泥沙起动Shields曲线与试验结果吻合较好,且能够概括单向流、波浪及波流等不同动力及细沙、粗沙等不同粒径的泥沙起动条件。 相似文献
20.
Thermogravimetric Fourier transform infrared spectroscopy (TG-FTIR) analyses were carried out on two sets of isolated kerogens covering a wide maturity range from low mature (0.46% Ro) through the end of oil and gas generation (maximum Ro = 5.32%). Data onweight percent and Tmax for evolution of methane, volatile tars, ethylene, SO2, NH3, CO2, and CO are reported. The Tmax of methane shows the most consistent response to increasing maturation in both sets of samples. Results are comparable to those of whole rocks from an Alaskan North Slope well analyzed previously. The collective data for both whole rocks and isolated kerogens shows a generally linear correlation between %Ro and Tmax of methane, with the exception of Ro of about 2.0% where a dip in the curve occurs. The slope of the correlation line was steeper for the predominantly terrigenous Wilcox kerogen than for more marine Colorado kerogen or for the Alaskan North Slope whole rock samples, probably reflecting differences in the chemical nature of various kerogen sets, which is also reflected by differences in the shapes of the pyrolysis curves of SO2, CO2, CO, H2O, and ethylene. These preliminary data indicate that Tmax of methane is a good maturation indicator for whole rocks and isolated kerogens up to an Ro of about 4%, which includes all of the wet gas and a considerable portion of the dry gas generation zones. This correlation was also observed for samples containing migrated bitumen, where it was not possible to obtain a reliable Tmax for the volatile tar (S2) peak. The more terrigenous Wilcox kerogens also showed a good correlation of the Tmax of ethylene with %Ro. Tmax of ammonia evolution did not correlate with maturity and occurred 100–200°C lower than previously found for whole rocks, consistent with a whole-rock source of pyrolytic ammonia for Alaskan whole rock samples. HI and OI indices were calculated in several ways and plotted to reflect kerogen type as well as both the residual oil and gas generation potential. The ratio of pyrolyzable to combustible sulfur (evolved as SO2) was independent of maturity and showed a clear difference between the more terrigenous Wilcox kerogens and the more marine Colorado kerogens. 相似文献