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231.
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
232.
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
233.
上海洋山建港后港域夏季水文泥沙状况分析 总被引:1,自引:0,他引:1
对2007年9月17-26日在上海洋山港海域固定观测点(平均水深13 m)观测得到的水文泥沙要素,以及悬沙和底质样品分析.分析结果为:1)港域有效波高0.21-1.37 m(风速0.6~14.0 m/s),平均0.61 m(平均风速5.5 m/s).平静天气(平均风速小于5.0 m/s)下,波高随水深变化,两者的相关系数为0.899;而在强风天气下,波高受风况控制.2)最大表层流速超过2.00 m/s.大潮涨潮流占优势,小潮时落潮流占优势;与北岛链汉道封堵前相比,大潮涨、落潮平均流速分别减小15%和30%,小潮涨、落潮平均流速均减小30%~40%.各层余流均为西北方向,与涨潮流方向一致;垂向平均余流速0.11 cm/s,表层达0.25 m/s.3)离底高程1.35 m层和0.35m层最大悬沙浓度均大于3 kg/m3,两层平均悬沙浓度分别为0.89和0.95 kg/m3.无论大潮还是小潮涨潮悬沙浓度均大于落潮,这种现象在大潮时更为显著,潮周期中最大悬沙浓度出现在涨急.与工程前相比悬沙浓度明显降低,大、小潮降低均达20%.4)港区底质平均粒径9.0μm,工程后有变细的趋势. 相似文献
234.
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
235.
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
236.
The size effect of copper wire radius (0.04–0.82 mm) on the diffusion-limited current density of an oxygen reduction reaction in stagnant simulated seawater (naturally aerated 0.5 mol/L NaCl) is investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) and compared with the results obtained in 0.5 mol/L H2SO4. In the oxygen diffusion-limited range, size effect is found to occur independent of electrolytes, which is attributed to non-linear diffusion. Additionally, to sati... 相似文献
237.
Wind plays an important role in hydrodynamic processes such as the expansion of Changjiang (Yangtze) River Diluted Water (CDW), and shelf circulation in the Changjiang estuary. Thus, it is essential to include wind in the numerical simulation of these phenomena. Synthetic aperture radar (SAR) with high resolution and wide spatial coverage is valuable for measuring spatially inhomogeneous ocean surface wind fields. We have collected 87 ERS-2 SAR images with wind-induced streaks that cover the Cbangjiang coastal area, to verify and improve the validity of wind direction retrieval using the 2D fast Fourier transform method. We then used these wind directions as inputs to derive SAR wind speeds using the C-band model. To demonstrate the applicability of the algorithms, we validated the SAR-retrieved wind fields using QuikSCAT measurements and the atmospheric Weather Research Forecasting model. In general, we found good agreement between the datasets, indicating the reliability and applicability of SAR- retrieved algorithms under different atmospheric conditions. We investigated the main error sources of this process, and conducted sensitivity analyses to estimate the wind speed errors caused by the effect of speckle, uncertainties in wind direction, and inaccuracies in the normalized radar cross section. Finally, we used the SAR-retrieved wind fields to simulate the salinity distribution off the Changjiang estuary. The findings of this study will be valuable for wind resource assessment and the development of future numerical ocean models based on SAR images. 相似文献
238.
Sediment-associated processes, such as sediment erosion, deposition, and pore water diffusion/advection affect sorptive contaminant transport. By considering these processes, we developed an equation to simulate contaminant transport. Erosion and deposition processes are considered as erosion and deposition fluxes of sediment, and adsorption-desorption processes of contaminants by sediment are simulated using the Langmuir Equation. Pore water diffusion is calculated based on the contaminant concentration gradient across the sediment-water interface. Pore water advection is estimated using pore water contained in the sediments of erosion flux. The equation is validated to simulate total phosphorus concentrations in Guanhe estuary in the northern Jiangsu, China. The simulated total phosphorus concentrations show better agreement with field observations compared to estimations that do consider sediment-associated processes. 相似文献
239.
240.