Circulation model for water circulation and purification in a water Cerenkov detector

Owing to its low cost and good transparency, highly purified water is widely used as a medium in large water Cerenkov detector experiments. The water circulation and purification system is usually needed to keep the water in good quality. In this work, a practical circulation model is built to describe the variation of the water resistivity in the circulation process and compared with the data obtained from a prototype experiment. The successful test of the model makes it useful in the future design and optimization of the circulation/purification system.     

Study on dielectric properties of oil/water random composites

Considering the electric double layers between oil and water, a new “complex model” of dielectric constant of oil/water composites was built up. Starting from the Maxwell–Garnett theory and Bruggeman theory, the effective dielectric constant of oil/water random composites is presented. The nonlinearity of the theory is obvious. The model is especially suited to study the dielectric properties of oil/water composites of different nature. The model is also suited to study the dielectric properties of two-phase random composites with an interfacial shell. The theoretical results on dielectric properties of different kinds of oil/water composites are in good agreement with experimental data.     

Electrodialytic desalination of brackish water: effect of process parameters and water characteristics

The aim of this work is to study the desalination of brackish water using a laboratory scale electrodialysis cell. The influence of several parameters, such as flow rates, initial feed concentration, applied voltage and circulation mode on process efficiency were studied. This efficiency is evaluated by the demineralization rate, ionic flux transport and current efficiency. In this study, experiments were carried out on synthetic brackish water solutions prepared from sodium chloride salts. The concentrations of these solutions are varying from 0.5 to 3 g L^?1. The process was applied for the treatment of real brackish water sample with total dissolved salts ～5 g L^?1. The concentrations of different species in the obtained treated water are below the amounts recommended by World Health Organization for drinking water.     

Structure of supercritical water

This review paper gives the more up to date information on the structure of supercritical water, at different thermodynamic states, for densities ranging from 0.2 to 0.7 g.cm⁻³, studied by neutron scattering. The experimental partial pair correlation functions g_OH(r), G_HH(r) and g_OO(r) are compared with the results of molecular dynamics simulations using the (SPCE) model potential for water. The results confirm that hydrogen bonding is still present in dense supercritical water and are in good agreement with data obtained by NMR and Raman spectroscopies.     

基于光谱匹配的内陆水体反演算法

提出了一种新的基于光谱匹配的内陆水体反演算法。该方法首先使用已知的水面实测光谱和水体组分(叶绿素,悬浮物,黄色物质)的吸收系数,计算得到悬浮物的后向散射系数。第二步是通过水体组分浓度的交叉组合,利用生物光学模型计算光谱反射率,建立包含所有水体组分组合情况的查找表(LUT:look-up table),查找表中每条光谱都对应已知的三种水体组分的浓度。第三步利用MODIS的通道响应函数,把查找表光谱数据变换成MODIS波段反射率。检验查找表的适用性,使用验证数据基于最小距离的匹配原则进行查找,最后得到与之对应的三种水质参数。利用春秋两个季节的数据进行以上的研究,其中秋季建立的查找表代表性较好,其中叶绿素的平均相对误差为38.6%,悬浮物的平均相对误差为28%。本方法既结合了生物光学模型物理意义明确的优点,又回避了单位光学量随时空变化的缺点,是一种可行的方法。     

On the role of water vapour in the heat balance of the antarctic lower stratosphere

Summary A general circulation model (GCM) is used to investigate the effect on Antarctic temperatures due to changes in ozone and water vapour concentrations. It is shown that the stratospheric cooling due to the ozone secular trend is largely compensated by the H₂O loss associated with the formation of type 2 polar stratospheric clouds (PSC-2). The partial dehydration of the Antarctic lower stratosphere acts in such a way to significantly reduce the cooling associated to the O₃ depletion.     

Radiative heat transfer analysis in pure water heater used for semiconductor processing

A simplified one-dimensional model is presented to analyze the non-gray radiative transfer in pure water heater used in the rinsing processes within semiconductor production lines, and the ray-tracing method is extended to simulate the radiative heat transfer. To examine the accuracy of the simplified model, the distribution of radiation absorption is determined by the ray-tracing method based the simplified model and compared with the data obtained by three-dimensional non-gray model in combination with Monte Carlo method in reference, and the effects of the water thickness on the radiation absorption are analyzed. The results show that the simplified model has a good accuracy in solving the radiation absorption in the pure water heater. The radiation absorption increases with the water thickness, but when the water thickness is greater than , the radiation absorption increases very slowly with the water thickness.     

Characterization of natural resin materials using water adsorption and various advanced techniques

A physicochemical characterization of natural raw resin material was evaluated and reported. The studied material is a natural resin, a natural product from pinus halepensis trees which is collected from the forests of Chalkidiki region of North Greece. The plurality of this product combined with its special property of removing water from commercial liquid fuels commands the detailed physicochemical characterization of this material. In particular, various techniques, such as water adsorption at 22 °C, thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy and X-ray diffraction, were used in order to evaluate the structural and surface properties of the material. The water adsorption isotherm was also measured and fitted using the Guggenheim, Anderson and De Boer model in order to correlate the water activity characteristics. In addition, the kinetics of the adsorption was also fitted with good accuracy using the exponential Chapman model. Furthermore, as the results show, the natural resin presents good thermal characteristics. Finally, the studied material presents efficient water adsorption properties, up to 246.8 mmol/g, and it can be proposed as a promising dehydration material.     

Mathematical modelling study for water uptake of steadily growing plant root

The root system of plant is a vitally important organ for living plant. One of the major functions of the root system is uptaking water and nutrients from the soil. The present paper analyzes the whole process of water uptake from soil by a steadily growing plant with a single slender root. We start from the basic principles of physics and fluid-dynamics, consider the structure characteristics of the water transport channel formed by the tiny xylems tubes inside plant, and establish a simplified coherent mathematical model to describe the water transport in the complete system consisting of soil, individual plant, including root, stem and leaves-atmosphere, on the basis of the plant physiology. Moreover, we resolve the proposed mathematical model for a simple artificial plant model under a variety of conditions, in terms of the numerical approach as well as analytical approach. It is shown that the results obtained by both approaches are in very good agreement; the theoretical predictions are qualitatively consistent with the practical experi-ences very well. The simplified mathematical model established in the present pa-per may provide a basis for the further investigations on the more sophisticated mathematical model.     

Dissipation in the dynamics of a moving contact line: effect of the substrate disorder

We investigate the time-dependent flow of water around a solid triangular profile oscillating horizontally in a narrow rectangular container. The flow is quasi two-dimensional and using particle image velocimetry we measure 20 snapshots of the entire velocity field during a period of oscillation. From the velocity measurements we obtain the circulation of the vortices and study the vortex dynamics. The time-dependence of the flow gives rise to the formation of a jet-like flow structure which enhances the vorticity production compared to the time-independent case. We introduce a simple phenomenological model to describe the important dynamical parameters of the flow, i.e., the vortex circulation and the jet velocity. We solve the model analytically without viscous damping and find good agreement between the model predictions and our measurements. Our work adds to the recent effort to understand more complicated flows past sand-ripples and insect wings.Received: 6 January 2004, Published online: 20 April 2004PACS: 47.32.Cc Vortex dynamics - 47.32.Ff Separated flows     

浅海近程混响的振荡现象*

研究浅海近程混响特性对于评估和提高主动声纳性能具有重要意义。多次浅海混响实验显示,近程混响强度存在稳定的振荡现象,脉宽基本对振荡的幅度和周期没有影响。为解释这一现象,本文基于射线理论和小斜率近似给出了浅海近程混响模型,仿真与实测数据结果基本吻合。数值仿真结果表明：海底反射声场对单站声纳接收到回声信号的贡献远小于海底近垂向大掠射角散射声场的作用;混响强度振荡现象是海底近程散射声场的多途现象造成的,并由此给出了振荡周期与海深及收发深度的关系。     

Monte Carlo studies of liquid water

Computer simulation studies are reported for the Rowlinson and Ben-Naim and Stillinger models of water-water interactions. Particular attention is given to the effects of altering the size of the system and to accounting for some long-range interactions by including the Onsager reaction field. It is shown that both models give a good qualitative account of the structure of liquid water but that neither is able to describe the high dielectric constant. A particularly sensitive property, the dipole-dipole correlation function, demonstrates the problems encountered in truncating the water interactions. Good agreement between the Rowlinson potential and a modified Hartree-Fock calculation suggests that the Rowlinson model is more accurate than the Ben-Naim and Stillinger form.     

基于NW型小世界人工神经网络的污水出水水质预测

为了预测污水处理出水水质,针对污水处理过程具有多变量、非线性、时变性、严重滞后的特点,提出了基于NW型小世界人工神经网络的污水处理出水水质预测模型。首先根据污水处理系统确定模型输入输出变量个数,然后建立了多层前向小世界神经网络模型,并对网络模型的隐层结构进行了优化研究。借助污水处理过程的历史数据进行了仿真研究,结果表明：和同规模的多层前向人工神经网络相比,小世界神经网络对污水出水水质预测具有较高精度和收敛速度,为污水出水水质的实时预测提供了一种有效的新方法。     

Dynamic properties of hydrogen-bonded networks in supercritical water

Dynamic properties of supercritical water at temperatures between 573 and 773 K and densities between 0.49 and 0.83 g/cm(3) have been investigated by molecular dynamics simulation and compared to states located on the vapor-liquid coexistence curve. A flexible simple point charge potential has been assumed for interactions in the subcritical states, whereas a reparameterization of that model has been performed to model the supercritical states. The hydrogen bonding structure and the diffusion coefficients in an ensemble of simulated states were previously analyzed and a good agreement with available experimental data was found. Dynamic properties of hydrogen bonding like the bond lifetimes and the influence of hydrogen bonds in the vibrational spectra are discussed along a range of simulation conditions. A nonlinear behavior of the hydrogen-bond lifetime as a function of temperature is observed in subcritical water whereas a linear dependence is found in supercritical water. Special attention is paid to the intermolecular vibrational spectrum (10-400 cm(-1)). It has been observed that the mode centered at 200 cm(-1), attributed to the intermolecular O-O stretching vibration in the ambient state remains active in the supercritical states.     

Density-functional based modeling of the intermediate in the water production reaction on Pt(111)

A model based on density-functional calculations has been developed for the overlayer formed by dissociation of water on an oxygen covered Pt(111) surface. The directional dependent interaction within the overlayer is treated by means of a lattice model of Ising type. Stable large length scale structures are found for two compositions proposed in the literature: a hydroxyl-water and a hydroxyl-hydrogen mixed composition, respectively. The water containing composition produces an overlayer structure in very good agreement with the structures seen in scanning tunneling microscopy experiments.     

HL-2M 装置冷却水系统介绍

介绍了 HL-2M 装置冷却水系统的组成以及各子系统的循环流程、运行原理和运行参数。      

基于水幕的舰船红外干扰策略研究

传统的红外成像反舰导弹的干扰策略如热焰弹和烟雾等已经不能很好地应对新型红外成像反舰导弹的威胁,针对该问题,设计一种在舰船表面不同分区施加水幕来对抗红外成像反舰导弹的策略,采用建模仿真的方式开展了水幕对红外成像导引头干扰效果的研究.建立综合考虑海天背景的舰船红外辐射仿真模型,结合典型图像识别算法,分析制定了不同的水幕施加...     

大气光学湍流估算模式及其相似性函数

地表热通量和水汽通量对全球气候变化和大气环流有着重要而广泛的影响,而Monin-Obukhov(M-O)相似性函数在计算近地层热通量和水汽通量的过程中扮演着重要的角色;同时M-O相似性函数是大气光学湍流估算模式中不可或缺的因子。通过对合肥西郊35 m铁塔上气象数据的分析,利用非线性最小二乘法拟合得到了一套全新的M-O相似性函数。将之与前人提出的相似性函数作对比,展现出了较好的一致性。同时,该函数大气光学湍流的估算模式中,估算值与实测值具有较好的吻合度。分析结果表明:在稳定条件和非常不稳定条件下,可以认为温度相似性函数等于湿度相似性函数,在弱不稳定条件下两者不再满足这种相似性。     

Measurments of attenuation and refractive dispersion due to atmospheric water vapor at 80 and 240 GHz

Field line-of-sight propagation experiments were made at 80 and 240 GHz on a horizontal path of 810 m. The measured attenuations showed quadratic dependences on atmospheric water vapor density, and absorptions in excess of theoretical predictions were observed at both frequencies, while the measured refractive dispersion between these two frequencies showed a linear dependence on water vapor density and was in good agreement with theoretical prediction. Liebe's model for water vapor attenuation including empirical continuum absorption is confirmed to be effective for 80 and 240 GHz.     

某中央空调制冷实验设备中水泵的合理选择

如果中央空调制冷实验设备中水泵选择不当,会使系统运行不正常,或者导致能量消耗加大,这都将造成工程的失败,因此,合理选择循环水泵具有重要的意义。以某中央空调制冷实验设备设计为例,说明水泵的合理选择方法。其对中央空调设计具有一定的参考价值。