检索结果-南通市图书馆

Fabrication of 6FDA-HFBAPP Polyimide Asymmetric Hollow Fiber Membranes and Their CO2/CH4 Separation Properties

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2019年第8期37卷 815-826页

作者： Cong-Jun gan Xiao-Chen Xu Xue-Wei Jiang Feng gan Jie Dong Xin Zhao Qing-hua Zhang State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and Engineering Donghua University

In this work, poly(amide acid) solution, the precursor of polyimide, was synthesized by the reaction of 4,4′-(hexafluoroisopropylidene)diphthalicanhydride and 2,2-bis[4-(4-aminophenoxy)phenyl]-hexafluoropropanane in the solvent of N-methyl-2-pyrrolidone(NMP) and tetrahydrofuran(THF). Then, hollow fiber membranes for high flux gas separation were prepared by dry-jet wet spinning using the precursor solution of poly(amide acid) as the spinning dope and a subsequent imidization process. Silicone rubber was further coated outside the obtained hollow fiber membranes to repair the defects on the denser layer. The effects of internal, external coagulation bath ratios with air gap, and coating solution concentrations on the morphologies, structures, and separation performance of the membranes were studied. Results showed that the sponge-like support layer was formed when the content of NMP was increased from 50% to 90% in the internal coagulation bath. The outer surface of the membrane became denser when the water content in the external coagulation bath increased from 40% to 100%, and the separation coefficient of CO2/CH4 increased by 2 times. This value could reach up to 1.4 when the air gap was 6 cm. With tuning the mass fraction of silicone rubber as 5%, hollow fiber composite membranes with uniform coating layer and an improved separation coefficient of 5.4 could be obtained.

关键词： Polyimide Gas separation Preparation conditions Membrane structure Permeability

Structural Modal Parameter Recognition and Related Damage Identification Methods under Environmental Excitations: A Review

在线全文

学校读者我要写书评

暂无评论

Structural Durability & Health Monitoring 2025年第1期19卷 25-54页

作者： Chao Zhang Shang-Xi Lai hua-Ping Wang School of Civil Engineering and Mechanics Lanzhou UniversityLanzhou730000China Key Laboratory of Special Functional Materials and Structural Design Ministry of EducationLanzhou UniversityLanzhou730000China

Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the ***,it is particularly signiﬁcant to identify the structural modal parameters according to the monitoring data information in the structural health monitoring(SHM)system,so as to provide a scientiﬁc basis for structural damage identiﬁcation and dynamic model modiﬁ*** view of this,this paper reviews methods for identifying structural modal parameters under environmental excitation and brieﬂy describes how to identify structural damages based on the derived modal *** paper primarily introduces data-driven modal parameter recognition methods(e.g.,time-domain,frequency-domain,and time-frequency-domain methods,etc.),brieﬂy describes damage identiﬁcation methods based on the variations of modal parameters(e.g.,natural frequency,modal shapes,and curvature modal shapes,etc.)and modal validation methods(e.g.,Stability Diagram and Modal Assurance Criterion,etc.).The current status of the application of artiﬁcial intelligence(ai)methods in the direction of modal parameter recognition and damage identiﬁcation is further *** on the pre-vious analysis,the main development trends of structural modal parameter recognition and damage identiﬁcation methods are given to provide scientiﬁc references for the optimized design and functional upgrading of SHM systems.

关键词： Structural health monitoring data information modal parameters damage identiﬁcation ai method

Liquid film dryout model for predicting critical heat flux in annular two-phase flow

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

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第3期10卷 398-417页

作者： Bo JIAO Li-min QIU Jun-liang LU Zhi-hua gan Institute of Refrigeration and Cryogenic Engineering Zhejiang University Hangzhou 310027 China

Gas-liquid two-phase flow and heat transfer can be encountered in numerous fields, such as chemical engineering, refrigeration, nuclear power reactor, metallurgical industry, spaceflight. Its critical heat flux (CHF) is one of the most important factors for the system security of engineering applications. Since annular flow is the most common flow pattern in gas-liquid two-phase flow, predicting CHF of annular two-phase flow is more significant. Many studies have shown that the liquid film dryout model is successful for that prediction, and determining the following parameters will exert predominant effects on the accuracy of this model: onset of annular flow, inception criterion for droplets entrainment, entrainment fraction, droplets deposition and entrainment rates. The main theoretical results achieved on the above five parameters are reviewed; also, limitations in the existing studies and problems for further research are discussed.

关键词： Annular two-phase flow Critical heat flux (CHF) Liquid film dryout Deposition rate Entrainment rate

Enhanced electrochemical oxidation of phenol by introducing ferric ions and UV radiation

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2008年第11期20卷 1386-1391页

作者： MAO, Xuhui WEI, Lin HONG, Song ZHU, hua LIN, An gan, Fuxing School of Resource and Environmental Science Environmental Engineering Department Wuhan University Wuhan 430079 China

The mineralization of phenol in aerated electrochemical oxidation has been *** results show that a cathodic Fenton process can occur when the Ti-0.3Mo-0.8Ni alloy material is used as cathode in solution containing ferric or ferrous ions; moreover,the reinforcement of cathodic Fenton process on the total organic carbon (TOC) removal rate of phenol is quite *** the metallic ions investigated,the ferric ion is the best catalyst for the electrochemical mineralization of phenol at initial...

关键词： mineralization phenol electrochemical oxidation cathodic Fenton process UV radiation

Diagnostics of Magnetic Field Strength in Gyrosynchrotron Radiation Regions for the Case of Transverse Propagation

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2000年第12期17卷 927-928页

作者： ZHOU ai-hua WANG Xin-Dong Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008 National Astronomical Observatories Chinese Academy of SciencesBeijing 100012

A set of diagnostic formulas is,for the first time,proposed to deal with the magnetic field strength B in gy-rosynchrotron radiation regions for the transverse propagation *** diagnostic formulas of B are applied to analyze a solar limb *** differences of diagnostic results of B are compared for the different propagation cases and it is found that the differences are rather *** in the analysis of limb burst we should use the diagnostic formulas for the transverse propagation.

关键词： strength transverse propagation

Synthesis of Silica Hollow Spheres with Diameter Around 50 nm by Anionic Surfactant

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

Chemical Research in Chinese Universities 2012年第3期28卷 361-363页

作者： RAN hua HAN Lu CHE Shun-ai State Key Laboratory of Composite Materials Thin Film and Microfabrication Technology of Ministry of EducationSchool of Chemistry and Chemical TechnologyShanghai Jiaotong UniversityShanghai 200240P.R.China

Silica hollow spheres（SHSs） have attracted great attention because of their low toxicity, low density, large surface area, high chemical and thermal stability, and surface permeability. They can be widely applied in storage^[l], catalysis^[2], drug deli- very^[3,4], low-dielectric-constant materials^[5], low-refractive materials^[6-8], and so on. Up to now, there have been various methods to produce SHSs. Inorganic^[9] or organic particles^[10], such as polystyrene or calcium carbonate, were used as hard templates to create hollow cavities, However, the multistep synthetic process and the lack of structural robustness of the shells upon template removal process weaken their applica- tion. Soft templates, including oil-in-water emulsions^[11,12], vesicles^[13], micelle^[14,15] and gas bubbles^[16], are applied widely.

关键词： Anionic surfactant Co-Structure directing agent(CSDA) Vesicle

Effect of backward-facing step heights in vegetation-step model on reducing the velocity of a tsunami inundation and increasing the energy dissipation efficiency

在线全文

学校读者我要写书评

暂无评论

JOURNAL OF HYDRODYNAMICS 2024年第5期36卷 803-816页

作者： huai, Wen-xin Zhang, Xiao-hua Li, Dan Yang, Zhong-hua ai, Yi-dan Wuhan Univ State Key Lab Water Resources Engn & Management Wuhan 430072 Peoples R China

A coastal forest combined with a backward-facing step is an efficient facility to reduce tsunami damage to residential areas behind sea embankments. This study establishes a generalized model, and experimentally explores the water level changes upstream of the vegetation-step mitigation model as well as its energy dissipation effect under different initial Froude numbers, step heights, and vegetation conditions. The results show that the relative backwater rise increases with the growth of vegetation density, patch length and initial Froude number, representing a slowing down of the tsunami inundation. As for energy dissipation, it is mainly caused by the additional resistance of the vegetation and the hydraulic jump. And the vegetation condition not only affects the energy dissipation due to stem-scale turbulence within the patch, but also changes the hydraulic jump process of water falling from the step in cooperation with the step height. As a result, the energy dissipation efficiency always increases with the growth of vegetation density, vegetation patch length and step height. With the criterion that the energy dissipation efficiency and its growth rate can hardly change with vegetation parameters, this study innovatively defines the threshold slope and gives the principle of judging the most cost-effective vegetation conditions at different step heights. These results are expected to provide an important reference for the design of composite tsunami mitigation facilities.

关键词： Vegetation-step model step height backwater rise energy dissipation

Differential Polymorphic Transformation Behavior of Polybutene-1 with Multiple Isotactic Sequences

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 Polymer Science 2020年第2期38卷 164-173,I0007页

作者： Ya-Ping Ma Wei-Ping Zheng Chen-Guang Liu hua-Feng Shao hua-Rong Nie ai-hua He Shandong Provincial Key Laboratory of Olefin Catalysis and Polymerization Key Laboratory of Rubber-Plastics (Ministry of Education) Qingdao University of Science and Technology

For the solid-solid transformation from form Ⅱ to form Ⅰ of isotactic polybutene-1(iPB),the temperature dependence of form Ⅰ nucleation and growth was deemed to control the transformation ***,the relationship between formⅠ formation and form Ⅱ disappearance in the transformation process is not *** this work,the spontaneous crystal transformation from form Ⅱ to Ⅰ of iPB with 81 mol%mmmm sequence concentration is studied firstly by tracking the two processes,the decay of form Ⅱ and the yielding of form Ⅰ in a wide range of temperature spanning from 0℃ to 50℃ and in a long transformation time ranging from 5 min to 65 days with in situ FTIR and *** the literature reports,the decay rate of form Ⅱ is firstly found to be lower than the yielding rate of form Ⅰ at all studied temperatures,especially at low transition *** is attributed to the amorphous chains which locate near crystal lamella participating into the nucleation of form Ⅱ.The regular chain folding and growth of i PB form Ⅰ from amorphous chains containing short isotactic sequences also lead to an increase in crystallinity of form Ⅰ compared with that of initial form Ⅱ crystallized at 60℃.An increase in the annealing temperature results in decrease in crystallinity and increase in lamellae thickness of i PB formⅠ.

关键词： Polybutene-1 Polymorphic transformation Isotactic sequence Crystallinity Lamellae thickness

The Noncommutative Residue about Witten Deformation

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2019年第4期35卷 550-568页

作者： Kai hua BAO ai Hui SUN Chao DENG School of Mathematics Ineer Mongolia University for Nationnalities College of Mathematics Jilin Normal University School of Mathematics and Statistics Northeast Normal University

In this paper, we compute lower dimensional volumes Vol_4^((1,1)) and Vol_6^((2,2)) about Witten deformation for 4, 6-dimensional spin manifolds with boundary respectively, and get assosiated Kastler–Kalau–Walze type theorems. We also give theoritic explaination of the gravitational action for 4, 6 dimensional manifolds with boundary by these noncommutative residues.

关键词： Lower-dimensional volumes noncommutative residue gravitational action Witten deformation