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211.
It is necessary to pay more attention to the durability of concrete undergoing freeze-thaw cycles and seawater attack simultaneously.Investigated are the effects of water-binder ratio,fly ash (FA) contents and air-entraining agent on resistance to frost and chloride diffusion of marine concrete blended with FA in natural seawater.The results show that fly ash does not improve the frost resistance of concrete but can improve its resistance to chloride diffusion by addition of less than 30%.The resistance to frost and chloride diffusion of FA concrete can be improved with the decrease of water-binder ratio,and FA may improve both of them simultaneously only being mixed with air-entraining agent.A ratio (named as R) of the frost-resisting durability factor to chloride diffusion coefficient can be used to evaluate the durability of marine concrete.Scanning electron microscope (SEM) analyses are consistent with the evaluations by the value of R. 相似文献
212.
Reevaluation of historical ocean heat content variations with time-varying XBT and MBT depth bias corrections 总被引:6,自引:0,他引:6
As reported in former studies, temperature observations obtained by expendable bathythermographs (XBTs) and mechanical bathythermographs
(MBTs) appear to have positive biases as much as they affect major climate signals. These biases have not been fully taken
into account in previous ocean temperature analyses, which have been widely used to detect global warming signals in the oceans.
This report proposes a methodology for directly eliminating the biases from the XBT and MBT observations. In the case of XBT
observation, assuming that the positive temperature biases mainly originate from greater depths given by conventional XBT
fall-rate equations than the truth, a depth bias equation is constructed by fitting depth differences between XBT data and
more accurate oceanographic observations to a linear equation of elapsed time. Such depth bias equations are introduced separately
for each year and for each probe type. Uncertainty in the gradient of the linear equation is evaluated using a non-parametric
test. The typical depth bias is +10 m at 700 m depth on average, which is probably caused by various indeterminable sources
of error in the XBT observations as well as a lack of representativeness in the fall-rate equations adopted so far. Depth
biases in MBT are fitted to quadratic equations of depth in a similar manner to the XBT method. Correcting the historical
XBT and MBT depth biases by these equations allows a historical ocean temperature analysis to be conducted. In comparison
with the previous temperature analysis, large differences are found in the present analysis as follows: the duration of large
ocean heat content in the 1970s shortens dramatically, and recent ocean cooling becomes insignificant. The result is also
in better agreement with tide gauge observations.
On leave from the Meteorological Research Institute of the Japan Meteorological Agency. 相似文献
213.
石晓辛 《成都信息工程学院学报》2009,24(2):201-203
研究Liemrd方程零解的渐近稳定性.在Liapunov函数Ⅴ满足dV/dt≤0的情况下,给出了进一步判断其渐近稳定的一个条件. 相似文献
214.
王水球 《成都信息工程学院学报》2009,24(3)
运用泛函分析性质以及Fourier变换的方法研究带有周期边界条件的非线性k-s方程在有限时间区间上的精确控制.首先研究线性化k-s方程的精确控制,证明对于任意给定的函数u0∈Hs,uT∈Hs,总能找到一个控制函数h使得线性化k-s方程有解u且满足u(x,0)=u0,u(x,T)=uT;然后结合线性化k-s方程的精确控制,通过定义Fredholm算子并应用Fredholm算子的一些理论找到非线性化k-s方程的控制函数,使其可精确控制. 相似文献
215.
Rossby waves with linear topography in barotropic fluids 总被引:1,自引:0,他引:1
Rossby waves are the most important waves in the atmosphere and ocean, and are parts of a large-scale system in fluid. The theory and observation show that, they satisfy quasi-geostrophic and quasi-static equilibrium approximations. In this paper, solitary Rossby waves induced by linear topography in barotropic fluids with a shear flow are studied. In order to simplify the problem, the topography is taken as a linear function of latitude variable y, then employing a weakly nonlinear method and a perturbation method, a KdV (Korteweg-de Vries) equation describing evolution of the amplitude of solitary Rossby waves induced by linear topography is derived. The results show that the variation of linear topography can induce the solitary Rossby waves in barotropic fluids with a shear flow, and extend the classical geophysical theory of fluid dynamics. 相似文献
216.
Based on the field data acquired in the program of fast ice observation off Zhongshan Station, Prydz Bay, East Antarctica during the austral summer 2005/ 2006, physical properties evolution of fast ice during the ice ablation season is analyzed in detail. Results show that the annual maximum ice thickness in 2005 occurred in later November, and then ice started to reek, and the ablation duration was 62 days; sea water under the ice became warmer synchronously; corresponding to the warming sea ice temperature, a "relative cold mid-layer" appeared in sea ice; the fast ice marginal line recoiled back to the shore observably, and the recoil distance was 20.9 km from 18 December 2005 through 14 January 2006. In addition, based on the data of sea ice thickness survey along the investigation course of MV Xuelong on December 18 of 2005, the ice thickness distribution paten in the marginal ice zone have been described : sea ice thickness increased, but the diversity of floe ice thick-ness decreased from open water to fast ice zone distinctly. 相似文献
217.
218.
完全非线性波浪破碎模型沿岸流数值模拟 总被引:1,自引:1,他引:0
探讨一种基于完全非线性Boussinesq方程的波浪破碎模型在沿岸流计算中的应用问题。针对控制方程中的完全非线性项对沿岸流成长过程的影响进行了深入讨论。数学模型计算结果表明,完全非线性项有使平均流局部化的作用;通过数模实验还发现,垂向高阶涡度项可以有效抑制破波区外回流;运用Visser的实验室沿岸流实测资料从沿岸流速度、波高和平均水位几方面对所提模型进行了验证,并给出了紊动参数的计算结果。 相似文献
219.
220.