Ordered water monolayer on ionic model substrates studied by molecular dynamics simulations

The molecular behaviors of interfacial water molecules at the solid/liquid interface are of a fundamental significance in a diverse set of technical and scientific contexts,thus have drawn extensive attentions.On certain surfaces,the water monolayer may exhibit an ordered feature,which may result in the novel wetting phenomenon.In this article,based on the molecular dynamics simulations,we make a detailed structure analysis of the ordered water monolayer on ionic model surface with graphene-like hexagonal lattices under various charges and unit cell sizes.We carefully analyze the water density profiles and potential of mean force,which are the origin of the special hexagonal ordered water structures near the solid surface.The number of hydrogen bonds of the ordered water monolayer near the solid surface is carefully investigated.

Enhancement of water self-diffusion at super-hydrophilic surface with ordered water

It has been well acknowledged that molecular water structures at the interface play an important role in the surface properties, such as wetting behavior or surface frictions. Using molecular dynamics simulation, we show that the water self-diffusion on the top of the first ordered water layer can be enhanced near a super-hydrophilic solid surface. This is attributed to the fewer number of hydrogen bonds between the first ordered water layer and water molecules above this layer, where the ordered water structures induce much slower relaxation behavior of water dipole and longer lifetime of hydrogen bonds formed within the first layer.

Ceria modified three-dimensionally ordered macro-porous Pt/TiO_2 catalysts for water-gas shift reaction

Three-dimensionally ordered macro-porous （3DOM） TiO2 and ceria-modified 3DOM TiO2 supported platinum catalysts were prepared with template and impregnation methods, and the resultant samples were characterized by scanning electron microscopy（SEM）, X-ray diffractometer（XRD）, high-resolution transmission electron microscopy（HRTEM） and temperature programmed reducfion（TPR） techniques. The catalytic performances over the platinum-based catalysts were investigated for water-gas shift （WGS） reaction in a wide temperature range （180-360 ℃）. The results showed that 3DOM Pt/TiO2 catalyst exhibited obviously better catalytic performance than the corresponding non macro-porous catalyst, owing to the macro-porous structure favoring mass transfer. Addition of celia into 3DOM Pt/TiO2 led to improvement of catalytic activity. TPR and HRTEM results showed that the interaction existed between ceria and titanium oxide and addition of ceria promoted the reducibility of platinum oxide and TiO2 on the interface of platinum and TiO2 particles, which contributed to high activity of the celia modified catalysts. The results indicated that ceria-modified 3DOM Pt/TiO2 was a promising candidate of fuel cell oriented WGS catalyst.

On the Fifth-Order Stokes Solution for Steady Water Waves

This paper presents a universal fifth-order Stokes solution for steady water waves on the basis of potential theory. It uses a global perturbation parameter, considers a depth uniform current, and thus admits the flexibilities on the definition of the perturbation parameter and on the determination of the wave celerity. The universal solution can be extended to that of Chappelear （1961）, confirming the correctness for the universal theory. Furthermore, a particular fifth-order solution is obtained where the wave steepness is used as the perturbation parameter. The applicable range of this solution in shallow depth is analyzed. Comparisons with the Fourier approximated results and with the experimental measurements show that the solution is fairly suited to waves with the Ursell number not exceeding 46.7.

Three-dimensionally ordered macro-porous Pt/TiO_2 catalyst used for water-gas shift reaction

Three-dimensionally ordered macro-porous （3DOM） Pt/TiO2 catalysts were prepared by template and impregnation methods, and the resultant samples were characterized by using TG-DTA, XRD, SEM, TEM, and TPR techniques. The catalytic performance for water-gas shift （WGS） reaction was tested, and the influences of some conditions, such as reduction temperature of catalysts, the amount of Pt loadings and space velocity on catalytic performance were investigated. It was shown that Pt particles were homogeneously dispersed on 3DOM TiO2. The reduction of TiO2 surface was important for the catalytic performance. The activity test results showed that the 3DOM Pt/TiO2 catalysts exhibited very good catalytic performance for WGS reaction even at high space velocity, which was owing to the better mass transfer of 3DOM porous structure besides the high intrinsic activity of Pt/TiO2.

Statistical Distribution of Depth-Integrated Local Horizontal Momentum for Second-Order Random Ocean Waves in Finite Water Depth

Based on the second order random wave solutions of water wave equations in finite water depth, statistical distributions of the depth integrated local horizontal momentum components are derived by use of the characteristic function expansion method. The parameters involved in the distributions can be all determined by the water depth and the wave number spectrum of ocean waves. As an illustrative example, a fully developed wind generated sea is considered and the parameters are calculated for typical wind speeds and water depths by means of the Donelan and Pierson spectrum. The effects of nonlinearity and water depth on the distributions are also investigated.

Variations of water's local-structure induced by solvation of NaCl

The researches on the structure of water and its changes induced by solutes are of enduring interests. The changes of the local structure of liquid water induced by NaCl solute under ambient conditions are studied and presented quantitatively with some order parameters and visualized with 2-body and 3-body correlation functions. The results show that, after the NaCl are solvated, the translational order t of water is decreased for the suppression of the second hydration shells around H20 molecules; the tetrahedral order （q） of water is also decreased and its favorite distribution peak moves from 0.76 to 0.5. In addition, the orientational freedom k and the diffusion coefficient D of water molecules are reduced because of new formed hydrogen-bonding structures between water and solvated ions.

AN ANALYTICAL SOLUTION OF SECOND－ORDER WAVE FORCE ON A VERTICAL CIRCULAR CYLINDER

So far many investigations have been made on nonlinear wave diffraction problemfor a large-diameter vertical circular cylinder. However,there are still some problemsworthy to be further discussed. It includes that the second order radiation condition isnot very clear and the inhomogeneous term of second order free surface boundarycondition makes the calculation of second order wave force either not easier to beperformed accurately due to its slowly decaying with radial distance or toocomplicated for practical application. In this paper, the second order radiationcondition is posed of the circumferential Fourier components of second orderpotential, instead of the second order potential. It is found that the circumferenatialFourier cormponents of second order potential have to satisfy Sommerfeld radiationcondition. By means of the mathematical formulae derived in this paper, theinhomogeneous term of second order free surface boundary condition were simplifiedand then an exact expression of second order wave force was obtained, which issimpler in form and easier to be used in practical calculation. The calculation resultsagree well with some experimental data.

Numerical storm surge model with higher order finite difference method of lines for the coast of Bangladesh

In this study, the method of lines (MOLs) with higher order central difference approximation method coupled with the classical fourth order Runge-Kutta (RK(4,4)) method is used in solving shallow water equations (SWEs) in Cartesian coordinates to foresee water levels associated with a storm accurately along the coast of Bangladesh. In doing so, the partial derivatives of the SWEs with respect to the space variables were discretized with 5-point central difference, as a test case, to obtain a system of ordinary differential equations with time as an independent variable for every spatial grid point, which with initial conditions were solved by the RK(4,4) method. The complex land-sea interface and bottom topographic details were incorporated closely using nested schemes. The coastal and island boundaries were rectangularized through proper stair step representation, and the storing positions of the scalar and momentum variables were specified according to the rules of structured C-grid. A stable tidal regime was made over the model domain considering the effect of the major tidal constituent, M2 along the southern open boundary of the outermost parent scheme. The Meghna River fresh water discharge was taken into account for the inner most child scheme. To take into account the dynamic interaction of tide and surge, the generated tidal regime was introduced as the initial state of the sea, and the surge was then made to come over it through computer simulation. Numerical experiments were performed with the cyclone April 1991 to simulate water levels due to tide, surge, and their interaction at different stations along the coast of Bangladesh. Our computed results were found to compare reasonable well with the limited observed data obtained from Bangladesh Inland Water Transport Authority (BIWTA) and were found to be better in comparison with the results obtained through the regular finite difference method and the 3-point central difference MOLs coupled with the RK(4,4) method with regard to the root mean square error values.

Robust Source Localization in Shallow Water Based on Vector Optimization

Owing to the multipath effect, the source localization in shallow water has been an area of active interest. However, most methods for source localization in shallow water are sensitive to the assumed model of the underwater environment and have poor robustness against the underwater channel uncertainty, which limit their further application in practical engineering. In this paper, a new method of source localization in shallow water, based on vector optimization concept, is described, which is highly robust against environmental factors affecting the localization, such as the channel depth, the bottom reflection coefficients, and so on. Through constructing the uncertainty set of the source vector errors and extracting the multi-path sound rays from the sea surface and bottom, the proposed method can accurately localize one or more sources in shallow water dominated by multipath propagation. It turns out that the natural formulation of our approach involves minimization of two quadratic functions subject to infinitely many nonconvex quadratic constraints. It shows that this problem （originally intractable） can be reformulated in a convex form as the so-called second-order cone program （SOCP） and solved efficiently by using the well-established interior point method, such as the sottware tool, SeDuMi. Computer simulations show better performance of the proposed method as compared with existing algorithms and establish a theoretical foundation for the practical engineering application.

海水淡化厂与区域水-能耦合系统的协同调度

海水淡化厂具有能量密集、运行灵活的特点,是理想的电力需求响应资源。然而,现有关于淡化厂与电网协同运行的研究大多关注电网和淡化厂的一体化调度、无法适应双方自主决策的工程场景,对淡化厂运行约束的刻画也比较粗糙。该文研究反渗透淡化厂与区域水-能耦合系统(waterenergy nexus,WEN)的协同运行方法。首先,考虑淡化厂的生产流程、调节特性和运行约束,分别建立传统及新能源淡化厂的水-能管理模型;其次,在保障两类淡化厂和区域WEN自主决策和信息隐私的条件下,提出以双方调度计划互动为载体的“激励型”和“价格型”两种协同运行机制及调度模型,并提出基于二阶锥松弛和McCormick包络的求解方法。用算例验证所提协同运行机制、调度模型及求解方法的有效性。

An Efficient Model for Transient Surface Waves in Both Finite and Infinite Water Depths

A numerical model is developed to simulate fully nonlinear extreme waves in finite and infinite water-depth wave tanks. A semi-mixed Enlerian-Lagrangian formulation is adopted and a higher-order boundary element method in conjunction with an image Green function is used for the fluid domain. The botmdary values on the free surface are updated at each time step by a fourth-order Runga-Kutta time-marching scheme at each time step. Input wave characteristics are specified at the upstream boundary by an appropriate wave theory. At the downstream boundary, an artificial damping zone is used to prevent wave reflection back into the computational domain. Using the image Green function in the whole fluid domain, the integrations on the two lateral walls and bottom are excluded. The simulation results on extreme wave elevations in finite and infinite water-depths are compared with experimental results and second-order analytical solutions respectively. The wave kinematics is also discussed in the present study.

基于产权视角的政府投资农村水利设施可持续供给研究

随着乡村振兴的不断推进,农村水利设施的重要性愈发凸显。为探究如何提高设施的可持续供给水平、实现政府投资农村水利设施持续性高质量供给,基于案例分析,梳理总结出产权明晰度、运行秩序合理性和农民管护积极性是政府投资农村水利设施供给可持续性的主要影响因素,并结合产权理论、交易费用理论、集体行动理论、制度分析与发展框架等理论,构建了产权明晰度、运行秩序合理性、农民管护积极性对政府投资农村水利设施供给可持续性影响机理的理论模型。基于对华东地区多个省份农民的问卷调查,运用SPSS 26.0和Amos 24.0软件进行分析,结果表明:(1)产权明晰度、运行秩序合理性、农民管护积极性分别与政府投资农村水利设施供给可持续性正相关;(2)运行秩序合理性、农民管护积极性在产权明晰度与政府投资农村水利设施供给可持续性之间存在中介作用,农民管护积极性在运行秩序合理性与供给可持续性之间存在中介作用。

Long Term Soil and Water Assessment Tool (SWAT) Calibration from an Ecohydrology Perspective

The performance on prediction by mathematical models which represent the conceived image of a system such as hydrology is oftentimes represented through calibration and verification processes. Oftentimes a best fit between observed and predicted flows is obtained through correlation coefficient (R2) and the Nash Sutcliffe model efficiency (NSE) by minimizing the average Root Mean Square Error (RMSE) of the observed versus simulated flows. However, these days, a new paradigm is emerging wherein accounting for the flow variability for the protection of freshwater biodiversity and maintenance of goods and services that rivers provide is paramount. Therefore, from an ecohydrology perspective, it is not clear if the existing method of model calibration meets the needs of the riverine ecosystem at its best. Thus, this study investigates and proposes a methodology using entropy theory to gage the calibration of Soil and Water Assessment Tool (SWAT) from an ecohydrology perspective characterized by the natural flow-regime paradigm: Indicators of Hydrologic Alteration.

WATER SURFACE WAVE RADIATION GENERATED BY MULTIPLE CYLINDERS OSCILLATING WITH IDENTICAL FREQUENCY

The water surface wave radiation problem caused by multiple cylinders oscillating with identical frequency was solved in frequency domain by the boundary element method using simple Green's function in the inner water region combined with the eigenfunction expansions in the outer water region. The numerical method is suitable to the situation of constant depth of outer regions and complicated boundary conditions of inner region, while the oscillating modes, motion amplitudes and phases of the cylinders may be different from one another. The second order potential and hydrodynamic forces acting on each cylinder were evaluated completely by perturbation method. Compared with the case of single oscillating cylinder, hydrodynamic interference phenomena, such as wave resonance and negative added mass, of the radiation problem due to the oscillatory motions of multiple cylinders are identified which is of engineering importance to the design of moorings and other facilities involving multiple structures.

有限水深波浪作用下弱惯性塑料块体漂移规律

塑料漂浮垃圾对海洋环境影响巨大,在近岸的传播过程主要受波浪作用。针对塑料漂浮垃圾在近岸的运动特征,以往研究尚不深入。本文采用物理模型实验,对塑料漂浮物在有限水深波浪作用下的漂移规律开展研究,探讨了弱惯性塑料块体水平漂移速度与漂浮物性状以及波陡之间的关系。实验结果表明,塑料块体的漂移量受斯托克斯漂移与欧拉回流的共同影响,与二阶拉格朗日漂移理论吻合良好。在漂浮物尺寸远小于波长的情况下,漂浮物尺寸以及密度的改变对漂移没有显著的影响;漂浮物的漂移量与波陡的平方成正比,根据本文的实验及以往公开发表的实验数据,修正了经验公式,为塑料漂浮物在近岸的传播与预测提供了有益借鉴。

衢州市开化县水政执法的措施与成效

遏制水事违法案件的发生,保护水域功能的正常发挥,推动水政执法高质量发展。通过积极宣传法律法规,全方位开展行政检查,常态化进行河道巡查等方式,加强与公安、环保、自然资源等部门合作,采取多种形式的联合执法,共同打击水事违法分子。2022年,分发资料1000+份,行政检查68次,河道巡查45次,巡河长度4050 km,制止乱建、乱占、乱堆、乱采行为70次,取得了较好的整治效果。通过强化治水理念,实施铁腕治水,水事秩序明显好转,确保了一江清水流下游。

不规则波作用下岸基式振荡水柱波能装置的水动力性能研究

为了研究真实海域中振荡水柱(OWC)波能转换装置的水动力性能,本文基于势流理论和高阶边界元方法,建立了不规则波与岸基式OWC波能装置相互作用的二维非线性数值模型,不规则波基于JONSWAP谱生成。为了考虑由于水体黏性引起的能量耗散,在气室内水面边界条件中引入人工黏性阻尼。并在大连理工大学波流水槽中开展了物理模型试验,对数值模型的有效性进行了验证。研究发现,在不规则波作用下,OWC波能装置的水动力效率相较于规则波作用下有所降低,特别是在低频波区域效率差值最大。与规则波相比,不规则波浪作用下装置峰值效率对应的频率变大。气室内的相对水面高程随着有效波高的增加而降低,而气室内相对气压则随有效波高的增加而增大。OWC波能装置的水动力效率受有效波高的影响较小,其峰值效率对应的频率不受波浪非线性的影响。本文可以为OWC波能装置的设计提供参考。

高水分含量下淀粉的回生行为和分子机制

从凝胶化淀粉短程有序性的角度研究了高水分含量下淀粉在储藏过程中的回生行为。结果表明,在高水分含量下,短时间(1天)回生并未检测到晶体结构的形成,但是非晶态凝胶化淀粉的短程有序性结构有所增加。延长回生时间至7天,淀粉形成了明显的晶体结构;进一步延长回生时间,淀粉的回生程度继续增加。低场核磁共振(LF-NMR)和磁共振成像(MRI)分析发现,在回生过程中,游离水会从高水分含量的淀粉凝胶中分离出来。综上,得出结论:高水分含量下,凝胶化淀粉在短期储藏期间并不能形成晶体结构,但是其短程有序性程度会增加,随着回生时间的延长,会形成明显的晶体结构。

义昌江流域水质水量演变规律分析

研究义昌江流域降水量、径流量和水质指标演变规律,可为流域水资源开发利用、水环境保护和水生态改善提供数据支撑。运用线性趋势回归检验法研究其变化趋势,采用有序聚类分析法对其进行突变分析;分析水质指标时空变化,并进行水质评价;基于Pearson相关分析和双累积曲线法,研究义昌江流域水质变化的原因。结果表明:降水量、径流量、溶解氧、高锰酸盐指数、氨氮、粪大肠菌群变化趋势不明显。一般情况下,下游大冲口断面水质比上游断面好;从季节变化来看,冬季水质大部分合格、水质较好;从年变化来看,水质变化波动;径流对溶解氧、氨氮的影响比降水和水温更大,水温对高锰酸盐指数、粪大肠菌群的影响比降水和径流更大;水质指标变化受自然因素和人类活动共同影响。