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991.
The Changjiang Estuary is characterized by multi-order bifurcations, unsteady submerged sandbars, mid-channel sandbars, creeks and riffles. The following four types of saltwater intrusion are found: (1) direct intrusion from the sea; (2) intrusion during tidal flooding; (3) intrusion from tidal flats overflow; and (4) salt water coming upstream through other waterways. These result in a complicated temporal and spatial salinity distribution. A high chlorinity concentration zone exists from the Liuhekou to the Sidongkou along the South Branch. The salinity during neap tide or ordinary tide is higher than during spring tide. 相似文献
992.
993.
硒试剂光度法测定钢铁及加硒碘盐中的微量硒 总被引:1,自引:0,他引:1
以3,3'-二氨基联苯胺(硒试剂)作显色剂,加足量乙二胺四乙酸二钠(EDTA)掩蔽铁等金属离子,在pH为2-3的甲酸介质中显色,在pH为6-7时,用甲苯萃取硒(Ⅳ)-硒试剂络合物。当溶液中的硒(Ⅳ)含量大于20μg/10mL时,不用萃取硒(Ⅳ)-硒试剂络合物,直接测定。该方法用于钢铁及加硒碘盐中微理硒的测定,结果满意。 相似文献
994.
中庭建筑天井内火灾烟气运动特性的盐水实验模拟 总被引:1,自引:0,他引:1
本文运用盐水实验模拟方法研究了中庭建筑天井内的火灾烟气运动特性,实验模拟了天井内的烟气流态,即烟气羽流和并存的烟气环流,并定性分析了环流产生的机理。通过理论分析和实验结果,推导了天井内的羽流速度和决定环流起始方向的判据。同时,通过研究天井结构和侧室源强对流态的影响,给出了一种估算天井内不出现烟气环流时天井极限高度的方法 相似文献
995.
996.
We present some extensions of the distributions of the maximum of the Brownian bridge in [0,t] when the conditioning event is placed at a future timeu>t or at an intermediate timeu<t. The standard distributions of Brownian motion and Brownian bridge are obtained as limiting cases. These results permit us
to derive also the distribution of the first-passage time of the Brownian bridge. Similar generalizations are carried out
for the Brownian bridge with drift μ; in this case, it is shown that the maximal distribution is independent of μ (whenu≥t). Finally, the case of the two-sided maximal distribution of Brownian motion in [0,t], conditioned onB(u)=η (for bothu>t andu<t), is considered.
Dip. di Statistica, Probabilità e Stat. Applicate, Università di Roma “La Sapienza,” Piazzale Aldo Moros, 00185 Roma, Italy.
Published in Lietuvos Matematikos Rinkinys, Vol. 39, No. 2, pp. 200–213, April–June, 1999. 相似文献
997.
The solutions of various problems in the theories of queuing processes, branching processes, random graphs and others require the determination of the distribution of the sojourn time (occupation time) for the Brownian excursion. However, no standard method is available to solve this problem. In this paper we approximate the Brownian excursion by a suitably chosen random walk process and determine the moments of the sojourn time explicitly. By using a limiting approach, we obtain the corresponding moments for the Brownian excursion. The moments uniquely determine the distribution, enabling us to derive an explicit formula. 相似文献
998.
报道了二苯胺-4-重氮盐(DDS)与十二烷基硫酸钠(SDS)在水溶液中的相互作用.实验结果表明,体系粘度随SDS/DDS物质的量比(ξ)的变化而急增急降.当ξ=0~0.9时,二者形成沉淀,体系的粘度基本不变;当ξ=1.9~2.3时,沉淀溶解并伴随着体系粘度急增,最高粘度达初始值的2520倍;之后,随ξ的增大,体系粘度迅速下降至初始值.对DDS-SDS聚集体的微观结构与体系粘度的关系进行了初步讨论.同时发现体系粘度是光敏性的,紫外光照可使其迅速下降. 相似文献
999.
Parameters that influence ZrO2 (3-mol% Y2O3 stabilized) nanoparticles prepared by heating of alcohol–aqueous salt solutions were investigated. It revealed that the kind of alcohol used significantly affected the particle size and morphology of the as synthesized nano-ZrO2 powders. The ratio of alcohol to water (R/H) was also important to conduct the gelation process. The dispersion and sintering behavior of the powder could be optimized via aging. By carefully controlling the process, weakly agglomerated ZrO2 nanoparticles with an average particle size of 13-nm (TEM) were achieved. The classical DLVO theory was employed to clarify the effect of solvent on powder morphology, an aging mechanism was proposed as well. 相似文献
1000.
F. Alloin J.‐Y. Sanchez 《Journal of polymer science. Part A, Polymer chemistry》2000,38(16):2900-2909
Catalytic hydrogenation of unsaturated polyethers has been investigated. The partial reduction of the alkenyl functions appears a convenient way to prepare terpolymers from dipolymers. The free‐radical crosslinking of the partially hydrogenated polyethers provides amorphous networks at room temperature. Ionic conductivity of the polymer electrolytes based on these networks is markedly increased, as compared to the nonhydrogenated ones. The electrochemical stability window of these electrolytes is retained. In addition, this process seems easy to scale up. The resulting terpolymers provide networks whose mechanical properties are appropriate for lithium polymer batteries. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2900–2909, 2000 相似文献