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391.
对海洋多糖类药物—“872”样品,采用乙醇沉淀分级法得到的5个不同分子量级份(Ⅰ~Ⅴ)。以粘度法测定5个级份特性粘数[η];用激光小角光散射仪(LALLS仪)测定了各级份的重均分子量M_w和第二维利系数A_2;标定出“872”样品的Mark Houwink公式。测得872样品各级份/特性粘数。 相似文献
392.
The fall-rate of the T-5 expendable bathythermograph (XBT) produced by Tsurumi Seiki (TSK) Co., Ltd and that by Sippican Inc.,
are intercompared by a series of contemporaneous and colocated measurements with conductivity-temperature-depth (CTD) profilers.
It is confirmed that the fall-rates of the two manufacturers' T-5 differ by about 5 percent, despite the fact that they had
been believed to be identical for many years. The cause of the difference is discussed on the basis of a detailed cross-examination
of the two T-5 models. It is found for the first time that the two models are different in several respects. The manufacturer's
fall-rate equation is only applicable to the Sippican T-5, for which Boyd and Linzell's (1993) equation seems to be slightly
more accurate. Kizu et al.'s (2005) equation gives a clearly less biased depth than the manufacturers' equation for the TSK T-5. It is also found that
the fall-rates of both T-5 models are dependent on water temperature, perhaps because of viscosity. The temperature-dependency
of the fall-rate of the TSK T-5 is larger than that of the Sippican T-5. 相似文献
393.
Laboratory data on dry and saturated rocks show that pore fluid has the most important effect on rock attenuation. It is known
that viscous and inertial coupling between the frame of a porous rock and its pore fluid dissipates seismic energy by conversion
to heat and hence cause attenuation. We show that attenuation peaks, in saturated rock have the same property as that of typical
thermally activated relaxations. In the frequency domain, a plot of attenuation versus frequency shows an obvious systematic
shift to higher frequencies with increasing temperatures. Similarly, the attenuation versus temperature curve moves to higher
temperature with increasing frequencies. The attenuation peaks are somewhat broader than that for a Zener relaxation. A Cole-Cole
distribution of relaxation times closely matches the attenuations. This behavior can be explained theoretically by local flow
mechanisms. 相似文献
394.
Maria Tombrou Aggeliki Dandou Costas Helmis Evaggelos Akylas George Angelopoulos Helena Flocas Vasiliki Assimakopoulos Nikolaos Soulakellis 《Boundary-Layer Meteorology》2007,124(1):61-79
In the present study, an attempt is made to assess the atmospheric boundary-layer (ABL) depth over an urban area, as derived
from different ABL schemes employed by the mesoscale model MM5. Furthermore, the relationship of the mixing height, as depicted
by the measurements, to the calculated ABL depth or other features of the ABL structure, is also examined. In particular,
the diurnal evolution of ABL depth is examined over the greater Athens area, employing four different ABL schemes plus a modified
version, whereby urban features are considered. Measurements for two selected days, when convective conditions prevailed and
a strong sea-breeze cell developed, were used for comparison. It was found that the calculated eddy viscosity profile seems
to better indicate the mixing height in both cases, where either a deep convective boundary layer develops, or a more confined
internal boundary layer is formed. For the urban scheme, the incorporation of both anthropogenic and storage heat release
provides promising results for urban applications. 相似文献
395.
396.
Dissipative core–mantle coupling is evident in observations of the Earth's nutations, although the source of this coupling is uncertain. Magnetic coupling occurs when conducting materials on either side of the boundary move through a magnetic field. In order to explain the nutation observations with magnetic coupling, we must assume a high (metallic) conductivity on the mantle side of the boundary and a rms radial field of 0.69 mT. Much of this field occurs at short wavelengths, which cannot be observed directly at the surface. High levels of short-wavelength field impose demands on the power needed to regenerate the field through dynamo action in the core. We use a numerical dynamo model from the study of Christensen & Aubert (2006) to assess whether the required short-wavelength field is physically plausible. By scaling the numerical solution to a model with sufficient short-wavelength field, we obtain a total ohmic dissipation of 0.7–1 TW, which is within current uncertainties. Viscous coupling is another possible explanation for the nutation observations, although the effective viscosity required for this is 0.03 m2 s−1 or higher. Such high viscosities are commonly interpreted as an eddy viscosity. However, physical considerations and laboratory experiments limit the eddy viscosity to 10−4 m2 s−1 , which suggests that viscous coupling can only explain a few percent of the dissipative torque between the core and the mantle. 相似文献
397.
For two decades leading to the late 1980s, the prevailing view from studies of glacial isostatic adjustment (GIA) data was that the viscosity of the Earth's mantle increased moderately, if at all, from the base of the lithosphere to the core–mantle boundary. This view was first questioned by Nakada & Lambeck , who argued that differential sea-level (DSL) highstands between pairs of sites in the Australian region preferred an increase of approximately two orders of magnitude from the mean viscosity of the upper to the lower mantle, in accord with independent inferences from observables related to mantle convection. We use non-linear Bayesian inference to provide the first formal resolving power analysis of the Australian DSL data set. We identify three radial regions, two within the upper mantle (110–270 km and 320–570 km depth) and one in the lower mantle (1225–2265 km depth), over which the average of viscosity is well constrained by the data. We conclude that: (1) the DSL data provide a resolution in the inference of upper mantle viscosity that is better than implied by forward analyses based on isoviscous regions above and below the 670 km depth discontinuity and (2) the data do not strongly constrain viscosity at either the base or top of the lower mantle. Finally, our inversions also quantify the significant bias that may be introduced in inversions of the DSL highstands that do not simultaneously estimate the thickness of the elastic lithosphere. 相似文献
398.
Seismic studies of the lowermost mantle suggest that the core-mantle boundary (CMB) region is strongly laterally heterogeneous
over both local and global scales. These heterogeneities are likely to be associated with significant lateral viscosity variations
that may influence the shape of the long-wavelength non-hydrostatic geoid. In the present paper we investigate the effect
of these lateral viscosity variations on the solution of the inverse problem known as the inferences of viscosity from the
geoid. We find that the presence of lateral viscosity variations in the CMB region can significantly improve the percentage
fit of the predicted data with observations (from 42 to 70% in case of free-air gravity) while the basic characterisics of
the mantle viscosity model, namely the viscosity increase with depth and the rate of layering, remain more or less the same
as in the case of the best-fitting radially symmetric viscosity models. Assuming that viscosity is laterally dependent in
the CMB region, and radially dependent elsewhere, we determine the largescale features of the viscosity structure in the lowermost
mantle. The viscosity pattern found for the CMB region shows a high density of hotspots above the regions of higher-than-average
viscosity. This result suggests an important role for petrological heterogeneities in the lowermost mantle, potentially associated
with a post-perovskite phase transition. Another potential interpretation is that the lateral viscosity variations derived
for the CMB region correspond in reality to lateral variations in the mechanical conditions at the CMB boundary or to large-scale
undulations of a chemically distinct layer at the lowermost mantle. 相似文献
399.
结合水对海积软土流变性质的影响 总被引:7,自引:2,他引:7
海积软土的变形和强度性质与时间有明显的相关性,其原因之一是其中含量较多的结合水。土在一定压力下先排出自由水,然后是结合水,结合水膜厚度发生改变。压力改变结合水膜厚度,引起粘滞系数改变。通过剪切增变试验得到了粘滞系数与压力呈线性关系。研究粘滞系数与压力之间关系对修正或建立较为符合实际的本构模型有一定意义。 相似文献
400.
Alwina Enns Thorsten W. Becker Harro Schmeling 《Geophysical Journal International》2005,160(2):761-775