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摘要： Measured streamflow and flood series of 43 gauging stations from 25 west flowing rivers in Kerala, India, were analysed for their descriptive characteristics to study their spatial and temporal variation. The spatial and temporal variations in streamflow are influenced by many factors including climatic and basin characteristics. Streamflow data from each station (length varies from 14 to 43years) is analysed for their internal characteristics such as trend, stationarity, homogeneity, noise and periodicity to incorporate it in hydrological models, so that their predictions would be more accurate. The internal characteristics were studied along with the statistical analysis. For analysing each internal characteristic, more than one method of analysis has been used to have reliable result. The trend characteristic was analysed using Mann-Kendall (MK) test, Sen's slope test, Spearman's rank correlation coefficient and Pearson correlation coefficient methods. Stationarity characteristics have been tested using augmented Dickey-Fuller test (ADF), Phillips-Perron test and Kwiatkowski-Phillips-Schmidt-Shin (KPSS) test. For identifying homogeneous nature, Pettitt test, standard normal homogeneity (SNH) test, Buishand test and von Neumann tests were used. Noise in the streamflow was verified using Box-Peirce, Ljung-Box and McLeod-Li tests. From the study, it is found that the daily series is non-homogeneous, stationary data with white noise, whereas flood series shows mixed characteristics. Based on the variations in the time series, the daily streamflow and flood series are classified into different categories such as high, average, moderate, minor and no variation stations. In most of the river basins, daily flow shows average variation. Flood series shows average variation in 44% of stations and moderate variation in 28% of stations.

关键词： Channels between stages   axially split   entropy production analysis   numerical simulation   centrifugal pump  

摘要： The double-stage axially split centrifugal pump is widely used in water diversion and water pumping stations due to their ability to deliver at high heads and large flow rate for long running hours. Their flow characteristics can be greatly influenced by the geometry of the channels between the stages, which is a prominent place for irreversible loss to occur. Numerical investigations were extensively carried out and a comparison was drawn between two multistage axially split centrifugal pumps, with different channel designs between its stages. The reliability of the numerical model was confirmed after a good agreement existed between numerical results and the experiments. Subsequently, entropy generation terms were used to evaluate turbulence dissipation to characterize the flow losses. The modified channels had a great effect on reducing swirl near the impeller eye, thereby improving pump head by 12.5% and efficiency by 4.98% at the design condition. They however induced flow impact, causing an unusual separation, which generated high turbulence dissipation at the blade surfaces. The channels and second stage impeller were identified as major areas for selective optimization since their turbulence dissipation was dominant. Consequently, entropy production analysis with computational fluid dynamics could be relied upon to reveal the loss locations for selective optimization in centrifugal pumps.

关键词： Chemical structure   Bubbles   Animal feed   Fluxes   Hydrodynamics  

摘要： The hydrodynamic properties of a dual fluidized bed (DFB) with continuous feeding and discharging of solids were investigated on a pilot-scale plant in cold mode and simulated coupled with the structure-based drag model. We present a deep analysis that focuses directly on the problem of predicting the fluid dynamics behavior of this type of system for which empirical data is limited or unavailable. The fluidization of a DFB shows complex hydrodynamic characteristics because of the intricate interactions between different compartments experimentally. We prove that the simulation based on the structure-based drag model involving different fluidized structures is able to give an accurate prediction of pilot-scale DFB fluidization and capture the correct flow behaviors under different conditions. This work is expected to give thorough analysis and further exploration of the overall fluidization dynamics for DFB optimization and scale-up.

关键词： 特提斯喜马拉雅   多金属成矿带   氢氧同位素   成矿流体   矿床地质  

摘要： 特提斯喜马拉雅成矿带产出数十个规模不等的金矿、锑金矿、锑矿和铅锌多金属矿,近期的矿产勘查在片麻岩穹窿发现了铍稀有多金属矿床.该成矿带内发育两期金锑铅锌矿化,其一为以邦布金矿和马攸木金矿为代表的造山型金矿,形成于59~45 Ma,属于青藏高原造山主碰撞阶段的产物;其二为以姐纳各普金矿、车穷卓布锑矿、扎西康铅锌矿的晚期矿化和吉松铅锌矿等为代表的热液型矿化,集中形成于21~12 Ma的后碰撞造山阶段.大量的流体包裹体研究表明喜马拉雅金锑铅锌成矿带的成矿流体主要为中低温(小于300℃)、中低盐度流体(<10%NaCleqv).本文统计了已发表的和新获得的带内不同类型矿床共169个石英、绢云母、菱锰矿等热液矿物氢氧同位素数据,发现在δ^18OH2O-δDV-SMOW相图中,这些同位素组成构成了3个端元:A端元以车穷卓布锑矿为代表,显示出极低的δ^18OH2O值(低于-13‰)和低的δDV-SMOW值(<-111‰),靠近现代雨水线,完全落入西藏地热水H-O同位素范围;B端元以沙拉岗锑矿为代表,显示出具有最低的δDV-SMOW值(最低至-172‰)和较高的δ^18OH2O值(高达12‰),落入建造水的H-O同位素范围内;端元C以邦布金矿和浪卡子金矿为代表,显示出具有极高的δDV-SMOW值(高达-43‰)和中等的δ^18OH2O值,与造山型金矿氧同位素6‰~13‰的范围相同,包括了原始岩浆水的范围和部分变质水的范围.带内主要金属矿床成矿流体氢氧同位素均介于这3个流体端元之间,显示出绝大部分矿床的流体均非单一流体来源,而具有多源流体混合的特征.

关键词： 势函数特征参数   随机共振   信号检测   动车轴承  

摘要： 双稳随机共振的系统参数调节,会使势函数的势垒高度和势阱间距同时发生变化。为了能直观了解势函数特征的变化对双稳随机共振的影响,通过变量代换法实现势函数特征参数(势垒高度参数和势阱间距参数)的解耦,有利于势函数的调节;并提出了基于势函数特征参数调节的随机共振方法,根据Kramers逃逸速率与目标信号频率匹配原则,实现了目标信号的检测;为了克服随机共振对采样频比的要求,将势函数特征参数调节的随机共振与频域信息交换技术相结合,实现了低采样频比信号的检测。所提方法应用于动车转向架轴承故障的检测结果验证了方法的有效性。

关键词： 基本解方法   球面波势函数   三维弹性波散射   动应力集中  

摘要： 针对弹性波三维散射和动应力集中问题,提出一种基于球面波势函数的基本解方法(SWP-MFS)。方法基于单层位势理论,采用膨胀波和矢量剪切波球面波势函数构造散射波场,根据边界条件建立边界积分方程并配点求解。精度检验表明,该方法具有良好的数值精度及稳定性。以无限空间中三维夹杂体及空洞对平面P、SV波的散射为例,进行方法展示,并揭示了三维夹杂体周围弹性波散射的一些重要规律。结果表明:三维夹杂体随其内部介质刚度降低,位移谱曲线震荡越加强烈。三维球形空洞在P波和SV波水平入射下应力集中规律不同,前者在顶部和底部及附近更明显,后者在纵截面两45°角线附近更明显。与以往的集中力源函数相比,新的波场构造基本解更为简洁易用,为三维弹性波动分析提供了一种新型无网格数值方法。

关键词： 环境保护   油水分离   原油泄漏   浸润性   膜材料   表面张力   纺织材料  

摘要： 工业生产和日常生活中产生的含油废水处理是环境保护面临的一大挑战,海上原油泄漏造成的大规模海洋污染对生态系统造成了长期的破坏。通过测试不同层数和不同目数的原始尼龙网对油水混合物的分离效果,发现单层500目和2层400目的尼龙网均具有稳定的油水分离功能,即单层密集的尼龙网孔或2层稀疏的尼龙网孔均具有稳定的油水分离功能,并进一步利用尼龙网实现了对生活污水中油污的去除和海上浮油的吸收。最后深入分析了尼龙网具有油水分离功能的原理,揭示出尼龙网丝线表面的水膜对油的支承作用和油膜本身的表面张力是油水分离功能的核心原理。首次利用未经加工修饰的尼龙网实现油水分离功能,对油水分离技术的深入研究和油水分离装置的优化设计具有很好的借鉴意义。