检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

不同来流条件下急弯段环流结构演化过程研究

Review on heterogeneous oxidation and adsorption for arsenic removal from drinking water

工程力学 2025年第1期42卷 259-272页

作者：胡呈维余明辉渠庚长江科学院河流研究所武汉430010 长江科学院水利部长江中下游河湖治理与防洪重点实验室武汉430010 武汉大学水资源与水电工程科学国家重点实验室武汉430072

弯道环流是弯道水流运动的典型特征之一，一直以来都是众多学者关注的重点。弯道环流主要分为两类：第一类由水流经过弯道时受到的径向压差力差而引起，流速较大;第二类主要由紊流各向异性引起，尽管流速很小，但其与弯道岸坡冲刷过程... 详细信息

弯道环流是弯道水流运动的典型特征之一，一直以来都是众多学者关注的重点。弯道环流主要分为两类：第一类由水流经过弯道时受到的径向压差力差而引起，流速较大;第二类主要由紊流各向异性引起，尽管流速很小，但其与弯道岸坡冲刷过程密切相关。然而当前成果较少关注第二类弯道环流发展演化过程。因此，该文采用弯道水槽试验与数值模拟方法得到的高精度三维流速数据，研究弯道环流结构的变化规律及其动力特性，特别是第二类弯道环流的发展变化。研究结果表明：对于高雷诺数的急弯水流，由于紊动各向异性特征明显，弯道水流常会出现多个环流;对于纵向流速，当水流流经弯顶断面后，纵向流速沿垂向的分布已经明显偏离对数流速分布;当水流经过弯顶断面后，纵向流速沿着垂线存在着显著的均匀化趋势;当弗劳德数较大时，大尺寸涡体在不断分解中，使得原来的各向异性影响越来越小，凹岸附近的小尺寸环流趋近于各向同性状态，造成凹岸小环流逐渐微弱并最后消失;急弯段中环流与纵向水流互馈作用十分显著，弯道环流将对断面内的动量进行重分配，携带某些高速流体到断面内的其他区域，因此，在出现弯道环流的区域其纵向流速也一般比较小。

关键词：弯曲型河流急弯河段弯道环流水槽试验数值模拟

来源：博看期刊评论

在线全文

博看期刊

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2021年第12期33卷 178-188页

作者： Ruiping Liu Jiuhui qu Key Laboratory of Drinking Water Science and Technology Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China Center for Water and Ecology State Key Joint Laboratory of Environment Simulation and Pollution ControlSchool of EnvironmentTsinghua UniversityBeijing 100084China

The long term exposure of arsenic via drinking water has resulted in wide occurrence of arsenisim globally, and the oxidation of the non-ionic arsenite(As(Ⅲ)) to negatively-charged arsenate(As(Ⅴ)) is of crucial importance for the promising removal of arsenic. The chemical oxidants of ozone, chlorine, chlorine dioxide, and potassium permanganate may achieve this goal;however, their application in developing countries is sometimes restricted by the complicate operation and high cost. This review paper focuses on the heterogeneous oxidation of As(Ⅲ) by solid oxidants such as manganese oxide, and the adsorption of As(Ⅴ)accordingly. Manganese oxide may be prepared by both chemical and biological methods to achieve good oxidation performance towards As(Ⅲ). Additionally, manganese oxide may be combined with other metal oxides, e.g., iron oxide, to improve the adsorption capability towards As(Ⅴ). Furthermore, manganese oxide may be coated onto porous materials of metal organic frameworks to develop novel adsorbents for arsenic removal. To achieve the application in engineering works, the adsorbents granulation may be achieved by drying and calcination, agglomeration, and the active components may also be in situ coated onto the porous materials to maintain the oxidation and adsorption activities as much as possible. The novel adsorbents with heterogeneous oxidation and adsorption capability may be carefully designed for the removal of arsenic in household purifiers, community-level decentralized small systems, and the large-scale drinking water treatment plants(DWTPs).This review provides insight into the fundamental studies on novel adsorbents, the development of innovative technologies, and the demonstration engineering works involved in the heterogeneous oxidation and adsorption, and may be practically valuable for the arsenic pollution control globally.

关键词： Arsenic Heterogeneous oxidation Adsorption Manganese oxide Drinking water

Selberg's Normal Density Theorem for Automorphic L-Functions for GL_m

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2007年第10期23卷 1903-1908页

作者： Yan qu Department of Mathematics Shandong University Ji'nan 250100 P. R. China

Let π be an irreducible unitary cuspidal representation of GLm（AQ） with m ≥ 2, and L（s, Tr） the L-function attached to π. Under the Generalized Riemann Hypothesis for L（s,π）, we estimate the normal density of primes in short intervals for the automorphic L-function L（s, π）. Our result generalizes the corresponding theorem of Selberg for the Riemann zeta-function.

关键词： automorphic L-functions generalized Riemann Hypothesis normal density

Advanced flexible electrode materials and structural designs for sodium ion batteries

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2022年第8期31卷 108-128,I0004页

作者： Lina Zhao Zhehao qu Key Laboratory for Green Chemical Technology of Ministry of Education School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China Reactor Engineering Technology Research Institute China Institute of Atomic EnergyBeijing 102413China

With the spectacular rise of wearable and portable electronics,flexible power supplying systems with robust mechanical flexibility and high energy storage performance under various mechanical deformation conditions are imperative to be *** ion batteries(SIBs)with sustainable natural abundance,low cost and superb properties similar to equivalent lithium ion batteries(LIBs),which have shown significant potentials as energy source for flexible electronic *** this review,the recent advances in flexible electrode materials based on different types of conductive substrates are addressed and the strategies underlying rational design for flexible structures are highlighted,as well as their applications in flexible *** remaining key challenges in rational electrodes design are discussed,and perspectives for practical applications of flexible SIBs are proposed as general guidance for future research of high-performance flexible SIBs.

关键词： Flexible electronics Wearable devices Energy storage Sodium ion batteries Flexible electrode

Preparation of Nickel‑Cobalt/Carborundum Carbide Composite Coatings by Supergravity Field‑Enhanced Electrodeposition

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2020年第4期33卷 175-184页

作者： Xiaoyun Hu Ningsong qu Nanjing University of Aeronautics and Astronautics Nanjing 210016China Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology Nanjing 210016China

Nickel-cobalt/silicon carbide(Ni-Co/SiC)composite coatings were fabricated by supergravity field-enhanced *** surface morphology and the distribution of the SiC particles in the coatings were examined by scanning electron microscope and energy dispersive X-ray *** preferred orientations of the coatings were measured by X-ray *** wear resistance and microhardness were measured by a reciprocating tribometer and a microhardness instrument,*** results revealed that the use of the supergravity field enhanced the smoothness of the as-deposited Ni-Co/SiC coatings,and the SiC nanoparticles were uniformly distributed in comparison with that for conventional *** the rotation speed of the cathode,which provided the supergravity field,was 800 r/min,the SiC content in the coating reached a maximum of 8.1 wt%,which was a much higher content than the 2.2 wt%value obtained under conventional *** highest coating microhardness of 680 HV was also observed at this rotation *** addition,the wear resistance of the as-prepared Ni-Co/SiC coatings exhibited improved performance relative to that prepared under normal gravity.A minimum wear weight loss of 1.4 mg together with an average friction coefficient of 0.13 were also realized at a rotation speed of 800 r/min,values which were much lower than those for normal gravity.

关键词： Supergravity field Electrodeposition Microhardness Wear resistance

Improvements to machining surface quality by controlling the flow direction of electrolyte during electrochemical sinking and milling of titanium alloy

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2020年第12期63卷 2698-2708页

作者： LIU Yang qu NingSong National Key Laboratory of Science and Technology on Helicopter Transmission Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Electrochemical milling is eminently suitable for machining aerospace parts(which usually have complex structures) because of its great flexibility. However,titanium alloys are particularly sensitive to changes in the flow field,which often cause severe pitting corrosion of the machined surface. Although electrochemical sinking and milling(ESM) can restrict the flow of electrolyte and reduce pitting corrosion,the quality of the machined surface is not ideal because the latter are susceptible to stray corrosion. To reduce such corrosion and improve the surface quality,the internal flow channel of the tool electrode and the cutting depth were investigated thoroughly. Extensive experiments revealed that stray corrosion could be reduced significantly and surface quality improved by controlling the electrolyte flow direction in the machining area,which was achieved by changing the style of the internal flow channel of the tool electrode. These reductions in corrosion and surface roughness were achieved using a tool electrode with a triangular internal flow channel. In addition,the main components and micro-hardness of the machined surface were close to that of the TB6 titanium alloy substrate,which helped to maintain the inherent high strength of the titanium alloy. The surface of the workpiece changed from being hydrophilic to being hydrophobic,which reduced the flow resistance.

关键词： electrochemical sinking and milling titanium alloys flow direction surface quality and characteristics

Improving performance of macro electrolyte jet machining of TC4 titanium alloy:Experimental and numerical studies

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2022年第8期35卷 280-294页

作者： Minglu WANG Ningsong qu College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Electrolyte jet machining(EJM)is a promising method for shaping titanium alloys due to its lack of tool wear,thermal and residual stress,and cracks and ***,macro-EJM has attracted increasing attention for its high efficiency in machining wide grooves or ***,macro-EJM generates large amounts of electrolytic products,thereby increasing the difficulty of rapid product removal with a standard tool and reducing the surface ***,for enhanced product transport,a novel tool with a back inclined end face was proposed for macroEJM of TC4 titanium *** comparison,also proposed were ones with a standard flat end face,a front inclined end face,and both front and back inclined end *** flow field distributions of all proposed tools were simulated numerically,and experiments were also conducted to validate the simulation *** results show that one with a 5°back inclined end face can decrease the lowvelocity flow zone in the machining area and increase the high-velocity flow zone at the back end of tool,thereby promoting rapid product removal.A relatively smooth bright-white groove surface was *** same tool also resulted in the highest machining depth and material removal rate among the tested *** addition,rapid product removal was beneficial to the subsequent *** of its rapid product removal,the machining depth and material removal rate during deep groove machining using the tool with a 5°back inclined end face were respectively 7%and14%higher than those produced using a standard ***,the lowest bottom height difference of 0.027 mm can be obtained when the step-over value was 8.2 mm,and a plane with a depth of0.285 mm and a bottom height difference of 0.03 mm was fabricated using the tool with a 5°back inclined end face.

关键词： Electrochemical machining Macro electrolyte jet machining Product removal TC4 titanium alloy Tool end structure

A level set based immersed boundary method for simulation of non-isothermal viscoelastic melt filling process

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2021年第4期34卷 119-133页

作者： Qiang Li Fangcao qu School of Mathematics and Information Science Henan Polytechnic UniversityJiaozuo 454003China

In this work,the polymer melt filling process is simulated by using a coupled finite volume and levelset based immersed boundary(LSIB)***,based on a shape level set(LS)function to represent the mold boundary,a LSIB method is developed to model the complex mold *** the nonisothermal melt filling process is simulated based on nonNewtonian viscoelastic equations with different Reynolds numbers in a circular cavity with a solid core,and the effects of Reynolds number on the flow patterns of polymer melt are presented and compared with each *** then for a true polymer melt with a small Reynolds number that varies with melt viscosity,the moving interface,the temperature distributions and the molecular deformation are shown and analyzed in *** last,as a commonly used application case,a socket cavity with seven inserts is *** corresponding physical quantities,such as the melt velocity,molecular deformation,normal stresses,first normal stress difference,temperature distributions and frozen layer are analyzed and *** results could provide some predictions and guidance for the polymer processing industry.

关键词： LS-IB method Non-isothermal filling Non-Newtonian fluids Multiscale Numerical simulation

Flat jet electrochemical milling of TC4 alloy with tailoring backward parallel flow

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第4期37卷 574-592页

作者： Huanghai KONG Ningsong qu College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs on the machined titanium alloy surface because it inevitably suffers from the weak current density. In this study, a method of flat jet electrochemical milling with tailoring the backward parallel flow was proposed to eliminate the negative effects caused by the weak current density. Multiphysics simulations are carried out to comprehend the mechanism of flat jetEC milling with tailoring backward parallel flow and better construct the novel tool *** on flat jet electrochemical milling of TC4 alloy with and without tailoring backward parallel flow are conducted. The results reveal that, compared with flat jet electrochemical milling without tailoring backward parallel flow, the recommended tool reduces the surface roughness by86% to 93%, and improves the material removal rate by 93% to 163% with different feed ***, the recommended tool is more conducive to maintaining the inherent hardness of the material. Finally, a surface with low Sa of 0.37 μm is obtained.

关键词： Flat jet electrochemical milling TC4 alloy Surface roughness Micro-hardness Material removal rate