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331.
Field measurements of vertical profiles of velocity and salinity along with turbulence measurements have been used to examine the effect of density gradients on the flow structure in the Great Ouse estuary. During the flood tide shear and longitudinal density gradients cause well mixed conditions in the lower part of the water column. In the upper part of the water column secondary flow effects induced by transverse density gradients, and acceleration effects can contribute to the formation of stable vertical density gradients. On the ebb tide the vertical density gradient appears to be the dominant factor which determines the structure of the flow. The velocity and shear stress data show the evidence of large scale motions which are consistent with the postulated flood and ebb flow structures. 相似文献
332.
本文用Meissner公式、Bromley公式、Chen公式、Pitier公式及经作者改进的平均球近似(MSA)方法对锂盐水溶液(最大浓度达20mol/kg)的离子平均活度系数进行了计算和比较,结果表明改进后的MSA方法的计算精度最高。另外,本文还应用改进的MSA法,使用由单一电解质水溶液离子平均活度系数得到的参数,不用任何混合参数,预测了298.15k时LiCl+Li2SO4和LiCl+KCl水溶液的等温溶解度图.其结果与文献实验值基本一致。 相似文献
333.
334.
Evolution of the Earth's principal axes and moments of inertia: the canonical form of solution 总被引:4,自引:0,他引:4
Harmonic coefficients of the 2nd degree are separated into the invariant quantitative (the 2nd-degree variance) and the qualitative
(the standardized harmonic coefficients) characteristics of the behavior of the potential V
2(t). On this basis the evolution of the Earth's dynamical figure is described as a solution of the time-dependent eigenvalues–eigenvectors
problem in the canonical form. Such a canonical quadratic form is defined only by temporal variations of the harmonic coefficients
and always remains finite, even within an infinite time interval. An additional condition for the correction or the determination
of temporal variations of the 2nd degree is obtained. Temporal variations of the fully normalized sectorial harmonic coefficients
are estimated in addition to ˙Cˉ
20, ˙Cˉ
21, and ˙Sˉ
21 of the EGM96 gravity model. In addition, a non-linear hyperbolic model for Cˉ
2m
(t), Sˉ
2m
(t) is constructed. The trigonometric form of the hyperbolic model leads to the consideration of the potential V
2(ψ) instead of V
2(t) within the closed interval −π/2≤ψ≤+π/2. Thus, it is possible to evaluate the global trend of V
2(t), the Earth's principal axes and the differences of the moments of inertia within the whole infinite time interval.
Received: 25 September 1998 / Accepted: 28 June 2000 相似文献
335.
Derivation of design soil coefficients (S) and response spectral shapes for Eurocode 8 using the European Strong-Motion Database 总被引:1,自引:0,他引:1
A revision is presently under way to upgrade the status of the `Designrecommendations for earthquake resistance of structures', commonlyreferred to as Eurocode 8 (or EC8). In order to improve the definition ofthe design elastic response spectra (ERS) as defined in the Eurocode 8 –Part 1 (Draft May 2001), the values of the soil amplification factors havebeen calculated for sites on sedimentary soils, both stiff (category B) andsoft (category C), with respect to rock sites (category A), such ascontemplated in EC8. The work was performed by a systematic study ofresponse spectra as a function of magnitude and site conditions, usingrecords from the European Strong-Motion Database.The results confirm the occurrence of systematic spectral amplification onsedimentary soils with respect to reference rock in a large set of Europeanstrong motion data. Such amplification has been quantified through ameasure derived from the Housner Spectrum Intensity definition.The values of the soil coefficients recommended in the current version ofEC 8 are shown to be realistic for category C, in the case of a moderateseismicity context. However the values for subsoil class B need to besignificantly increased both for the moderate and high seismicity context. 相似文献
336.
用蒙特卡洛模拟法计算正交最小二乘法拟合参数的标准偏差 总被引:1,自引:1,他引:1
介绍了一种计算正交最小二乘法拟合参数标准偏差的新方法-蒙特卡洛模拟法,并以电子探针微区分析技术分析环境样品的数据为例,对用于计算经典最小二乘法回归系数标准偏差的公式法和蒙特卡洛模拟法进行了比较。计算结果表明,两者完全相符,蒙特卡洛模拟法的计算结果正确、可靠。考察了模拟次数对计算结果的影响。模拟次数大于500时,计算结果趋于稳定,计算所需时间在1min以内。拟合方差与回归系数标准偏差存在明显的相关关系。线性模型能解释的方差越大,回归系数标准偏差越小。蒙特卡洛模拟法特别适合于非线性模型拟合参数标准偏差的计算。 相似文献
337.
阳离子交换系数及其在地下水Pb污染研究中的应用 总被引:2,自引:0,他引:2
本文首先计算了地下水中常见阳离子与被吸附Pb^2+的交换系数,在此基础上利用实际地下水水质资料计算了天津市浅层地下水含水介质吸附最离子的当量分数,并利用吸附Pb^2 的当量分数估算了含水介质吸附Pb^2+的量及地下咸水中Pb^2 的浓度的增大量。 相似文献
338.
339.
The absorption cross-sections of HCFC-123 (CF3–CHCl2), HCFC-141b (CH3–CFCl2) and HCFC-142b (CH3–CF2Cl) are measured between 170 and 250 nm for temperatures ranging from 295 to 210 K with uncertainties between 2 and 4%. They are compared with other available determinations. Temperature effects are discussed and parametrical formulae are proposed to compute the absorption cross-section for wavelengths and temperatures useful in atmospheric modelling calculations. Photodissociation coefficients are presented and their temperature-dependence is discussed. 相似文献
340.
A general solution is deduced of the differential equations describing the propagation of elastic waves in a dissipative liquid-filled viscoelastic porous solid. The velocities of three existing waves have been expressed in convenient form using the moduli of the solid phase and by introducing the frequency-dependent equivalent mass densities. The solution is then used to examine some of the phenomena which arise when each of the three-body waves, in turn, are incident on a traction-free plane boundary. Analytic expressions for the reflection coefficients are obtained. Numerical calculations have been made, for a particular model, in case of incidentP
I wave. Effect of viscoelasticity and viscosity on the reflection coefficients has also been exhibited. 相似文献