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Impacts of water surface area of watershed on design flood

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Water Science and Engineering 2014年第1期7卷 41-48页

作者： qing-hua zhang Yan-fang DIAO Jie DONG College of Water Conservancy and Civil Engineering Shandong Agricultural University State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University

In order to analyze the impact of the water surface area of a watershed on the design flood, the watershed was classified into a land watershed and a water surface watershed for flood flow calculation at the same time interval. Then, the design flood of the whole watershed was obtained by adding the two flood flows together. Using this method, we calculated design floods with different water surface areas of three reservoirs and analyzed the impact of water surface area on the flood volume and peak flow. The results indicate that larger water surface areas lead to greater impacts on the flood volume and peak flow. For the same watershed area, the impact of water surface area on the flood volume and peak flow is positively proportional to the flood frequency, i.e., the higher the frequency, the greater the impact becomes.

关键词： watershed water surface area design flood, flood frequency flood volume peak Jlow

Experimental study on discharge coefficient of a gear-shaped weir

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Water Science and Engineering 2018年第3期11卷 258-264页

作者： Jing zhang Qian Chang qing-hua zhang Shu-ning Li College of Water Conservancy and Civil Engineering Shandong Agricultural University River Management Bureau Huaihe River Commission of the Ministry of Water Resources

This study focused on hydraulic characteristics around a gear-shaped weir in a straight channel. Systematic experiments were carried out for weirs with two different gear heights and eight groups of geometrical parameters. The impacts of various geometrical parameters of gear-shaped weirs on the discharge capacity were investigated. The following conclusions are drawn from the experimental study:(1) The discharge coefficient(m_c) was influenced by the size of the gear: at a constant discharge, the weir with larger values of a/b(a is the width of the gear, and b is the width between the two neighboring gears) and a/c(c is the height of the gear) had a smaller value of m_c. The discharge capacity of the gear-shaped weir was influenced by the water depth in the weir.(2) For type C1 with a gear height of 0.01 m, when the discharge was less than 60m^3/h and H_1=P 1.0, m_c slowly decreased with the increases of the discharge and H_1=P for a=b 1.0 and a=c 1.0, and slowly increased with the discharge and H_1=P for a=b > 1.0 and a=c > 1.0.(3) A formula of m_cfor gear-shaped weirs was established based on the principle of weir flow, with consideration of the water depth in the weir, the weir height and width, and the height of the gear.

关键词： Experimental study Discharge coefficient Discharge capacity Gear-shaped weir Geometrical parameter

Highly Transparent and Colorless Polyimide Film with Low Dielectric Constant by Introducing Meta-substituted Structure and Trifluoromethyl Groups

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Chinese Journal of Polymer Science 2021年第4期39卷 455-464,I0006页

作者： Hong-Tao Zuo Feng Gan Jie Dong Peng zhang Xin Zhao qing-hua zhang State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghai 201620China Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China

An effective design strategy for preparing highly transparent polyimide film with low dielectric constant is *** key to the strategy is to simultaneously introduce meta-substituted structure and trifluoromethyl in polymer *** using this design strategy,a highly transparent polyimide film with low-k was synthesized from 3,5-diaminobenzotrifluoride(m-TFPDA)and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)through a two-step *** obtained m-TFPDA/6FDA(CPI)film(~30 pm)possesses high optical transparency(λ_(cutoff)=334 nm,T_(450nm)=85.26%,Haze=0.31)and is close to colorless(L^(*)=96.03,a^(*)=-0.34,b^(*)=2.12,yellow index=3.96).The intrinsic k and dielectric loss value of the film are 2.27 and 0.0013 at 10 kHz,*** importantly,such low dielectric performance could remain stable up to 280℃,and the film shows a low moisture rate(~0.51%),which helps to maintain the low-k property stability in different humid ***,the film also shows good thermal stability and mechanical properties,with a glass transition temperature(T_(g))of 296℃and the 5 wt%decomposition temperature(T_(d,s%))of 522℃under N_(2).The tensile strength and tensile modulus of the film are 85.1 MPa and 1.96 GPa,*** addition,the film is soluble in common solvents,which allows simple solution processing and low-cost,continuous roll-to-roll *** design strategy is beneficial to improving the transparency,lightening yellow color,lowering the dielectric constant and meanwhile maintaining the comprehensive properties of polyimide films,which is mainly due to the introduced meta-substituted and trifluoromethyl structures effectively inhibiting the transfer of charge transfer complex(CTC)effects and increasing the free volume of *** design strategy could also be extended to other high-performance polymer systems.

关键词： Polyimide film Transparent Colorless Low dielectric constant

Rice Homeobox Transcription Factor HOX1a Positively Regulates Gibberellin Responses by Directly Suppressing EL1

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Journal of Integrative Plant Biology 2011年第11期53卷 869-878页

作者： Bi-qing Wen Mei-qing Xing hua zhang Cheng Dai Hong-Wei Xue National Key Laboratory of Plant-Molecular Genetics Institute of Plant Physiology and Ecology Shanghai Institute for Biological Sciences the Chinese Academy of Sciences Shanghai 200032 China

Homeobox transcription factors are involved in various aspects of plant development, including maintenance of the biosynthesis and signaling pathways of different hormones. However, few direct targets of homeobox proteins have been identified. We here show that overexpression of rice homeobox gene HOXla resulted in enhanced gibberellin （GA） response, indicating a positive effect of HOXla in GA signaling. HOXla is induced by GA and encodes a homeobox transcription factor with transcription repression activity. In addition, HOXla suppresses the transcription of early flowering1 （EL1）, a negative regulator of GA signaling, and further electrophoretic mobility shift assay and chromatin immunoprecipitation analysis revealed that HOXla directly bound to the promoter region of EL1 to suppress its expression and stimulate GA signaling. These results demonstrate that HOXla functions as a positive regulator of GA signaling by suppressing EL1, providing informative hints on the study of GA signaling.

关键词： EL1 giberellin giberellin signaling HOXla homeobox.

Scanning transmission electron microscopy: A review of high angle annular dark field and annular bright field imaging and applications in lithium-ion batteries

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Chinese Physics B 2018年第6期27卷 23-34页

作者： Yu-Xin Tong qing-hua zhang Lin Gu Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Belting 100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing 100190 China

Scanning transmission electron microscopy（STEM） has been shown as powerful tools for material characterization,especially after the appearance of aberration-corrector which greatly enhances the resolution of STEM. High angle annular dark field（HAADF） and annular bright field（ABF） imaging of the aberration-corrected STEM are widely used due to their high-resolution capabilities and easily interpretable image contrasts. However, HAADF mode of the STEM is still limited in detecting light elements due to the weak electron-scattering power. ABF mode of the STEM could detect light and heavy elements simultaneously, providing unprecedented opportunities for probing unknown structures of materials. Atomiclevel structure investigation of materials has been achieved by means of these imaging modes, which is invaluable in many fields for either improving properties of materials or developing new materials. This paper aims to provide a introduction of HAADF and ABF imaging techniques and reviews their applications in characterization of cathode materials, study of electrochemical reaction mechanisms, and exploring the effective design of lithium-ion batteries（LIBs）. The future prospects of the STEM are also discussed.

关键词： scanning transmission electron microscopy high angle annular dark field annular bright field lithium-ion batteries

Scalable Reaction-spinning of Rigid-rod Upilex-S^(■) Type Polyimide Fiber with an Ultrahigh T_(g)

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Chinese Journal of Polymer Science 2021年第5期39卷 592-600,I0007页

作者： Sen-Sen Zheng Han Dong Shi-hua Wang Jie Dong Tao Guo Xin Zhao qing-hua zhang Shanghai Collaborative Innovation Center for High Performance Fiber Composites Engineering Research Center of Technical TextilesMinistry of EducationDonghua UniversityShanghai201620China Jiangsu Aoshen Hi-Tech Materials Co. Ltd.Lianyungang 222000China

In the family of polyimide(PI)materials,Upilex-S^(■) film has been a shining star through the research PI materials due to its appealing ***,the wholly rigid-rod backbone and easily formed skin-core micromorphology and microvoids of Upilex-S~type PI lead to the high difficulty in melt-and wet-spinning ***,we propose a facile and scalable method,reaction-spinning,to fabricate the Upilex-S^(■) type PI fiber,in which the rapid solidification of spinning dope and partial imidization take place ***,the stability and mechanical strength of as-spun fibers can be improved,and the microvoids in fibers can be greatly reduced in relative to the wet-spun *** resultant Upilex-S^(■) type PI fiber shows higher tensile strength and modulus than most commercial thermal-oxidative polymeric fibers with an ultrahigh glass transition temperature T_(g) of 478℃.Moreover,the WAXS and SAXS results indicate that orthorhombic crystals are formed for Upilex-S^(■) type PI fiber in the post hot-drawing *** the hot-drawing temperature results in a continuous crystallization and high orientation of PI chains in amorphous phase and perfects the existing lamellar structure,which make a great contribution to the improved mechanical property.

关键词： Polyimide fiber Reaction-spinning Ultrahigh T_(g) Crystal structure

Baeyer-Villiger oxidation of ketones with hydrogen peroxide catalyzed by Sn-aniline complex

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Chinese Chemical Letters 2007年第1期18卷 4-6页

作者： qing hua zhang Shou Feng Wang Zi Qiang Lei Key Laboratory of Polymer Materials of Gansu Province College of Chemistry and Chemical Engineering Northwest Normal University Lanzhou 730070 China

Sn-aniline complex was prepared by a simple procedure. Cyclic and acyclic ketones were oxidized into lactones or esters with very high selectivity and yield with 30% hydrogen peroxide in the presence of Sn-aniline com... 详细信息

关键词： Baeyer-Villiger oxidation Sn-aniline complex Ketone oxidation Hydrogen peroxide

Preparation of Low-dielectric Permittivity Polyimide Resins with High Surface Activity from Chemically Bonded Hyperbranched Polysiloxane

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Chinese Journal of Polymer Science 2021年第9期39卷 1200-1210页

作者： Xiu-Ting Li Xiao-Meng Zhu Jie Dong Xin Zhao qing-hua zhang State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghai 201620China

Thermosetting resin matrix is the key component of advaneed wave-tra nsparent composites,where low dielectric constant,excellent processability,high thermal stability,as well as good bonding ability are required for ***,we prepared a series of phenylethynyl terminated polyimide(PI)resins by grafting amine-functi onalized hyperbra nched polysiloxane(HBPSi)to PI chains during the in situ *** effects of HBPSi on the processability of oligomers,molecular packing,thermal stability,dielectric property and bonding ability to reinforce Kevlar fibers of the cured PI/HBPSi composite resins have been examined in *** dielectric constants of the cured composite resins were greatly reduced from 3.29 to 2.19 without compromising its processability and thermal ***,the 10 wt%HBPSi-containing PI resin demonstrated better bonding ability to reinforce fibers with the in terfacial shear strength(IFSS)of 37.64 MPa,compared with that of neat PI-6 matrix(27.34 MPa),and better adhesion to metal with the lap shear strength of 10.48 MPa,50%higher than that of neat resin PI-6(6.98 MPa).These resultant PI/HBPSi composite resins exhibit excellent comprehensive properties,indicating their great potential as low-dielectric constant resin matrix in radar radome.

关键词： Hyperbranched polysiloxane Polyimide resin Low dielectric constant Processability Bonding ability

Construction of Safety and Non-flammable Polyimide Separator Containing Carboxyl Groups for Advanced Fast Charing Lithium-ion Batteries

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Chinese Journal of Polymer Science 2022年第4期40卷 345-354页

作者： Ji-Ping Gu Kai-Yuan zhang Xiu-Ting Li Jie Dong qing-hua zhang Xin Zhao State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghai 201620China

With the wide applications of lithium-ion batteries(LIBs)in electronic devices and electric vehicles,it is of great importance to improve their safety and electrochemical ***,soluble polyimides(PI)containing carboxyl groups(―COOH)were synthesized by a simple one-step method and PI separators with sponge-like,interpenetrating porous structures were prepared via non-solvent induced phase separation(NIPS).The obtained PI separators exhibited excellent thermal stability and fire-resistance properties,with the electrolyte uptake of 344%and good dimensional integrity in air at 200℃.The results showed that the lithium-ion transference number of the obtained PI separator could reach 0.48,which was much higher than that of the Celgard-2400 separator(0.38).The Li/LiFePO_(4) half-cell with the PI separator showed excellent cycle capability and high-rate performance with a high capacity of 121.80 mA·h·g^(-1) at 5 C,which was better than that of the cell with the Celgard-2400 separator(54.3 mA·h·g^(-1)),demonstrating the promising applications of this PI separators in LIBs.

关键词： Polyimide Separator Carboxyl groups Non-solvent induced phase separation Li transference number