检索结果-南通市图书馆

International Journal of Sediment Research 2013年第4期28卷 496-510页

作者： Yan-yan ZHANG de-yu zhong Bao-sheng WU State Key Laboratory of Hydroscience and Engineering Tsinghua University Pearl River Hydraulic Research Institute Pearl River Water Resources Commission

This paper presents a study on the characteristics of multiple time scales of bankfull discharge and its delayed response to changes of tlow conditions using continuous wavelet analysis for data from selected hydrologieal stations in the Yellow River *** showed that bankfull discharge series had one or two dominant lime *** example,the Huayuankou station in the lower reach of the Yellow River had two dominant time scales of 19 20 years and 5 6 *** dominant time seales of the bankfull discharge series were generally consistent with the dominant time scales of water discharge and sediment concentration series,indicating thai the channel morphology inherits the characteristics of the hydrologieal system in terms of multiple time *** addition,the wavelet coefficients of the bankfull discharge series had a phase difference in relation to those of the sediment concentration series,with a delay time that varied from 3 to 16 years at different *** delay time or relaxation lime is a result of the delayed response of bankfull discharge to How conditions,which was significant for channel adjustments in response lo changes of tlow *** findings of the multiple lime scales and the delayed response are of importance for further study of channel morphology of fluvial systems.

关键词： Multiple time scales wavelet analysis bankfull discharge river morphology fluvial processes Yellow River

A semi-implicit three-dimensional numerical model for non-hydrostatic pressure free-surface flows on an unstructured,sigma grid

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2013年第1期28卷 77-89页

作者： de-chao HU de-yu zhong Guang-qian WANG Yong-hui ZHU Senior Engineer Yangtze River Scientific Research InstituteWuhan 430010China Senior Engineer Yangtze River Scientific Research Institute State Key Laboratory of Hydroscience and Engineering Tsinghua University Associate Professor State Key Laboratory of Hydroscience and EngineeringTsinghua University

A semi-implicit 3-D numerical formulation for solving non-hydrostatic pressure free-surface flows on an unstructured,sigma grid is ***-splitting and 9 semi-implicit methods are inherited and reformed from Casulli’s z-coordinate *** non-orthogonal sigma-coordinate transformation leads to additional terms. The resulting linear system for the non-hydrostatic correction is diagonally dominant but unsymmetric,and it is solved by the BiCGstab *** contrast with z-coordinate non-hydrostatic models,the new model fits vertical boundaries much better,which is important for the long-time simulation of sediment transport and riverbed deformation.A lock-exchange density flow is computed to determine whether the new scheme is able to simulate non-hydrostatic free-surface *** new model is further verified using the field data of a natural river bend of the lower Yangtze *** agreement between simulations and earlier research results,field data is obtained, indicating that the new model is applicable to hydraulic projects in real rivers.

关键词： Three-dimensional Non-hydrostatic pressure Semi-implicit Sigma-coordinate Unstructured grid

A Bed-load function based on kinetic theory

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2012年第4期27卷 460-472页

作者： de-yu zhong Guang-qian WANG Lei ZHANG State key laboratory of Hydroscience and Engineering Tsinghua Univ.

Bed-load transport plays a fundamental role in morphological processes of natural rivers and human-made *** paper presents bed-load function derived on the basis of kinetic theory. The bed-load function is obtained by integrating the pick-up rate of bed sediment with respect to its longitudinal travel distance,following the basic concept on bed-load put forward by *** pick-up rate is expressed as an upwards flux of bed sediment and determined by invoking the particle velocity distribution function derived by solving the Boltzmann equation of kinetic theory. Comparisons of the present formula with six other bed-load formulas and the experimental data are also made in this *** results show that the present bed-load formula agrees well with the experimental *** addition,the influences due to collision between particles on bed-load is discussed which shows that an appreciable damping of the intensities of bed-load is observed only when the shear acting on particles is large enough to increase the concentration and intensity of random motion of bed load particles so that the collisions between sediment particles can occur.

关键词： Bed load Sediment transport Open channel flow Turbulence Two phase flow

Effect of 3-Amino-5-mercapto-1,2,4-triazole on Electroless Nickel deposition

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2008年第1期24卷 101-105页

作者： LIU Hai-ping LINing BI Si-fu LI de-yu ZOU zhong-li department of Applied Chemistry Harbin Institute of Technology Harbin 150001 P. R. China

The effects of organic additive, 3-amino-5-mercapto-1,2,4-triazole （AMTA） on bath stability, deposition rate, reaction activation energy, and Ni-P coating composition in acidic electroless nickel plating were investigated. Polarization curve method and infrared reflection spectroscopy were used to analyze the mechanism of the effect of AMTA on electroless nickel deposition. It was observed that AMTA improved bath stability, decreased the deposition rate, and increased the reaction activation energy. It was also revealed that AMTA decreased the phosphorus content and increased the sulfur content in Ni-P coating. In addition, AMTA inhibited the anodic oxidation of hypophosphite and accelerated the cathodic reduction of Ni^2＋. Infrared reflection spectroscopy result indicates that AMTA was adsorbed on the surface of Ni-P and interacted with Ni^2＋ to form an AMTA-Ni^2＋ compound. On the basis of the results of this study, the mechanism of the effect of AMTA on electroless nickel deposition was deduced.

关键词： Ni-P electrode Stabilizer deposition rate Adsorption

Dynamic Regulation of Hydrogen Bonding Networks and Solvation Structures for Synergistic Solar‑Thermal desalination of Seawater and Catalytic degradation of Organic Pollutants

在线全文

学校读者我要写书评

暂无评论

Nano-Micro Letters 2025年第2期17卷 548-565页

作者： Ming‑yuan yu Jing Wu Guang Yin Fan‑Zhen Jiao zhong‑Zhen yu Jin Qu Beijing Key Laboratory of Advanced Functional Polymer Composites Beijing University of Chemical TechnologyBeijing 100029People’s Republic of China State Key Laboratory of Organic‑Inorganic Composites College of Materials Science and EngineeringBeijing University of Chemical TechnologyBeijing 100029People’s Republic of China

Although solar steam generation strategy is efficient in desalinating seawater,it is still challenging to achieve continuous solar-thermal desalination of seawater and catalytic degradation of organic ***,dynamic regulations of hydrogen bonding networks and solvation structures are realized by designing an asymmetric bilayer membrane consisting of a bacterial cellulose/carbon nanotube/Co_(2)(OH)_(2)CO_(3)nanorod top layer and a bacterial cellulose/Co_(2)(OH)_(2)CO_(3)nanorod(BCH)bottom ***,the hydrogen bonding networks inside the membrane can be tuned by the rich surface–OH groups of the bacterial cellulose and Co_(2)(OH)_(2)CO_(3)as well as the ions and radicals in situ generated during the catalysis ***,both SO_(4)^(2−)and HSO_(5)−can regulate the solvation structure of Na^(+)and be adsorbed more preferentially on the evaporation surface than Cl^(−),thus hindering the de-solvation of the solvated Na^(+)and subsequent nucleation/growth of ***,the heat generated by the solar-thermal energy conversion can accelerate the reaction kinetics and enhance the catalytic degradation *** work provides a flow-bed water purification system with an asymmetric solar-thermal and catalytic membrane for synergistic solar thermal desalination of seawater/brine and catalytic degradation of organic pollutants.

关键词： Solar steam generation Seawater desalination Catalytic degradation Bacterial cellulose Cobalt hydroxycarbonate nanorods

Enantioselective reductive conjugate alkenylation of α,β-enones with keto alkenyl acetates by nickel catalysis

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2025年第1期68卷 157-162页

作者： Rong-de He yun-Lei Luo Qiu-Quan Pan Qi-Wei Yao Xing-zhong Shu State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University

Reactions involving alkenyl acetates offer cost-effective and environmentally friendly routes for alkene synthesis, yet their asymmetric variant remains elusive. Concurrently, asymmetric conjugate alkenylation predominantly centered on nucleophilic addition using alkenyl–M. This manuscript presents an asymmetric reductive conjugate alkenylation reaction involving alkenyl acetates. The method facilitates the enantioselective addition of keto alkenyl groups to α,β-enones, resulting in the formation of unsaturated diketones—a class of useful structural motifs that are challenging to access otherwise. The use of electron-rich Pyroxy ligand is essential for achieving both high reaction efficiency and enantioselectivity.

关键词： nickel alkenylation asymmetric cross-coupling alkenes

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

中国森林法总则问题再研究

林业经济问题 2014年第4期34卷 371-375页

作者：于德仲南京森林警察学院警务管理系南京210023

介绍森林法立法目的、效力范围、基本原则等中国森林法总则的主要内容。从5个方面分析森林法总则存在的问题:总则内容指导性较弱、立法目的定位失准、林种划分方法不科学、未充分体现现代林业经营理念、与分则出现内容上的交叉。针对这... 详细信息

介绍森林法立法目的、效力范围、基本原则等中国森林法总则的主要内容。从5个方面分析森林法总则存在的问题:总则内容指导性较弱、立法目的定位失准、林种划分方法不科学、未充分体现现代林业经营理念、与分则出现内容上的交叉。针对这些问题提出重新设计总则内容、调整立法目的、简化林种、树立现代林业经营理念、增强对分则的统领作用等建议。

关键词：森林法总则分则研究

Recent Advances in Artificial Sensory Neurons:Biological Fundamentals,devices,Applications,and Challenges

在线全文

学校读者我要写书评

暂无评论

Nano-Micro Letters 2025年第3期17卷 168-216页

作者： Shuai zhong Lirou Su Mingkun Xu desmond Loke Bin yu Yishu Zhang Rong Zhao Guangdong Institute of Intelligence Science and Technology HengqinZhuhai 519031People’s Republic of China College of Integrated Circuits Zhejiang UniversityHangzhou 3112000People’s Republic of China ZJU-Hangzhou Global Scientific and Technological Innovation Center Hangzhou 310027People’s Republic of China department of Science Mathematics and TechnologySingapore University of Technology and DesignSingapore 487372Singapore department of Precision Instruments Tsinghua UniversityBeijing 100084People’s Republic of China Center for Brain‑Inspired Computing Research Tsinghua UniversityBeijing 100084People’s Republic of China IDG/McGovern Institute for Brain Research Tsinghua UniversityBeijing 100084People’s Republic of China

Spike-based neural networks,which use spikes or action potentialsto represent information,have gained a lot of attention because of their high energyefficiency and low power *** fully leverage its advantages,convertingthe external analog signals to spikes is an essential *** including analog-to-digital converters or ring oscillators,and sensorssuffer from high power and area *** efforts are devoted to constructingartificial sensory neurons based on emerging devices inspired by the biologicalsensory *** can simultaneously perform sensing and spike conversion,overcoming the deficiencies of traditional sensory *** review summarizesand benchmarks the recent progress of artificial sensory *** starts with thepresentation of various mechanisms of biological signal transduction,followed bythe systematic introduction of the emerging devices employed for artificial ***,the implementations with different perceptual capabilitiesare briefly outlined and the key metrics and potential applications are also ***,we highlight the challenges and perspectives for the future development of artificial sensory neurons.

关键词： Artificial intelligence Emerging devices Artificial sensory neurons Spiking neural networks Neuromorphic sensing

Multicomponent polymerization of elemental sulfur,difluoromethylene phosphobetaine and aryl silyl ethers toward aromatic poly(O,O′-monothiocarbonate)s

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2025年

作者： Yongjiang yu Rongrong Hu Ben zhong Tang State Key Laboratory of Luminescent Materials and devices Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates South China University of Technology School of Science and Engineering Shenzhen Institute of Aggregate Science and Technology The Chinese University of Hong Kong AIE Institute

Polythiocarbonates with similar structures to polycarbonates, have emerged as a group of promising sulfur-containing polymers with a range of practical applications, taking advantages of their excellent optical properties, good thermal stability and filmforming ability, and so on. However, the synthesis of polythiocarbonates generally suffered from mixed isomeric structures of repeating units, and hazardous sulfur-containing reagents. In this work, an efficient multicomponent reaction of elemental sulfur,difluoromethylene phosphobetaine（PDFA）, and aryl silyl ethers was designed with the assistance of organic base 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene（MTBD） to produce 12 kinds of O,O′-monothiocarbonate compounds in up to 93% yields,taking advantages of the unique chemical property of difluorocarbene, and the deprotection of silyl group by F-generated from PDFA. Most importantly, the MTBD-assisted multicomponent polymerization of bis（aryl silyl ether）s, elemental sulfur, and PDFA was developed, affording 12 kinds of poly（O,O′-monothiocarbonate）s with well-defined structures, high Mws of up to16900 g/mol and high yields（up to 99%）. These poly（O,O′-monothiocarbonate）s possessed good film-forming properties and thermal stability, high light refractive indices and transmittance. The facile synthesis of these polymonothiocarbonates might pave the way for the development of promising sulfur-containing polymer materials.

关键词：

Metal-organic frameworks with dinuclear metal centers for synergistically boosting CO2 photoreduction

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China Chemistry 2025年第1期68卷 201-208页

作者： Hui-Feng Wang Wen-Jie Shi yu-Xin Yang Bao-Xia Dong Tong-Bu Lu Di-Chang zhong School of Chemistry and Chemical Engineering Yangzhou University Institute for New Energy Materials and Low Carbon Technologies School of Materials Science and Engineering Tianjin University of Technology

Dinuclear metal synergistic catalysis （DMSC） has been proved powerful in boosting CO2reduction,while this has not been achieved in heterogeneous catalysts with long-range order *** this study,we,by introduction of metal catalytic centers into an indium-based metal-organic framework （MOF）,obtained a series of isostructural In-MOFs,including three MOFs with mononuclear metal catalytic center （M-In）,three MOFs with dinuclear homometallic catalytic centers （MM-In）,and three MOFs with dinuclear heterometallic catalytic centers (MM’-In,M/M’=Co（II）,Ni（II）,Zn（II）).It was found that all these MOFs can serve as catalysts for photochemical CO2reduction to *** with M-In,the catalytic activities of MM-In were obviously enhanced,and that of MM’-In was further significantly *** example,the CO yield of Co Zn-In reaches a record value of 12,700μmol g-1h-1,which is 4.0,8.1,9.4,and 18.6-fold higher than that of Co Co-In,Zn Zn-In,Co-In,and Zn-In,***,the catalytic activities of Co Ni-In and Ni Zn-In also show different fold increase than those of corresponding dinuclear homometallic and mononuclear metallic *** results of control experiments and theoretical calculation reveal that the higher catalytic activities of MM-In over M-In can be ascribed to the DMSC effect,and the higher catalytic activity of MM’-In over MM-In can be ascribed to the strengthened DMSC *** work reveals the relationship between DMSC effect and bimetal centers in CO2reduction,which provides new insights into the DMSC and paves a new way to design highly active catalysts for photochemical CO2reduction.

关键词： metal-organic frameworks dinuclear metal centers synergistic catalysis CO2 reduction photocatalysis