检索结果-南通市图书馆

A wideband fast multipole boundary element method for half-space/plane-symmetric acoustic wave problems

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2013年第2期29卷 219-232页

作者： Chang-Jun Zheng hai-bo Chen Lei-Lei Chen Department of Modern Mechanics University of Science and Technology of China

This paper presents a novel wideband fast multipole boundary element approach to 3D half-space/planesymmetric acoustic wave *** half-space fundamental solution is employed in the boundary integral equations so that the tree structure required in the fast multipole algorithm is constructed for the boundary elements in the real domain ***,a set of symmetric relations between the multipole expansion coefficients of the real and image domains are derived,and the half-space fundamental solution is modified for the purpose of applying such relations to avoid calculating,translating and saving the multipole/local expansion coefficients of the image *** wideband adaptive multilevel fast multipole algorithm associated with the iterative solver GMRES is employed so that the present method is accurate and efficient for both lowand high-frequency acoustic wave *** for exterior acoustic problems,the Burton-Miller method is adopted to tackle the fictitious eigenfrequency problem involved in the conventional boundary integral equation *** on the implementation of the present method are described,and numerical examples are given to demonstrate its accuracy and efficiency.

关键词： Helmholtz equation·boundary element method·Half-space/plane-symmetric problem·Wideband fast multipole method·Noise barrier

ORGANIC/INORGANIC HYBRID EPOXY NANOCOMPOSITES BASED ON OCTA(AMINOPHENYL)SILSESQUIOXANE

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2013年第1期31卷 148-158页

作者： hai-bo Fan 杨荣杰 Xiang-mei Li School of Materials Science & Engineering Beijing Institute of Technology

Octa（aminophenyl）silsesquioxane （OAPS） was used as the curing agent of diglycidyl ether of bisphenol-A （DGEBA） epoxy resin. A study on comparison of DGEBA/OAPS with DGEBA/4,4＇-diaminodiphenyl sulfone （DDS） epoxy resins was achieved. Differential scanning calorimetry was used to investigate the curing reaction and its kinetics, and the glass transition of DGEBA/OAPS. Thermogravimetric analysis was used to investigate thermal decomposition of the two kinds of epoxy resins. The reactions between amino groups and epoxy groups were investigated using Fourier transform infrared spectroscopy. Scanning electron microscopy was used to observe morphology of the two epoxy resins. The results indicated that OAPS had very good compatibility with DGEBA in molecular level, and could form a transparent DGEBA/OAPS resin. The curing reaction of the DGEBA/OAPS prepolymer could occur under low temperatures compared with DGEBA/DDS. The DGEBA/OAPS resin didn＇t exhibit glass transition, but the DGEBA/DDS did, which meant that the large cage structure of OAPS limited the motion of chains between the cross-linking points. Measurements of the contact angle indicated that the DGEBA/OAPS showed larger angles with water than the DGEBA/DDS resin. Thermogravimetric analysis indicated that the incorporation of OAPS into epoxy system resulted in low mass loss rate and high char yield, but its initial decomposition temperature seemed to be lowered.

关键词： Organic-inorganic hybrid composites Nanostructures Epoxy resin Silsesquioxane Curing kinetics.

Synthesis of Cyclic Carbonates from CO_2 and Epoxides Catalyzed by Hexaalkylguanidinium Halides

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2004年第5期20卷 568-571页

作者： DUANhai-feng LISheng-hai LINYing-jie XIEhai-bo ZHANGSuo-bo WANGZong-mu StateKeyLaboratoryofPolymerPhysicsandChemistry ChangchunInstituteofAppiledChemistryChineseAcademyofSciencesChangchun130022P.R.China DepartmentofOrganicChemistry CollegeofChemistryJilinUnivesityChangchun130023P.R.China

Hexaalkylguanidinium halides exhibit an efficient catalytic activity in the synthesis of cyclic carbonates from epoxides and carbon dioxide. By this method cyclic carbonates can be obtained in a high yield and a high selectivity at a low temperature and atmospheric pressure. This procedure is easy for the product isolation and recycling of the catalyst.

关键词： Synthesis Cyclic carbonate Hexaalkylguanidinium

Precision of the Chinese Space Station Telescope(CSST)stellar radial velocities

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第4期21卷 207-215页

作者： Yang Sun Ding-Shan Deng hai-bo Yuan Department of Astronomy Beijing Normal UniversityBeijing 100875China

The Chinese Space Station Telescope(CSST)spectroscopic survey plans to deliver high-quality low-resolution(R>200)slitless spectra for hundreds of millions of targets down to a limiting magnitude of about 21 mag,covering a large survey area(17500 deg^(2))and a wide wavelength range(255-1000 nm by three bands GU,GV,and GI).In this work,we use empirical spectra of the Next Generation Spectral Library to simulate the CSST stellar spectra at R=250,and investigate their capabilities in measuring radial *** find that velocity uncertainties depend strongly on effective temperature,weakly on metallicity for only FGK stars,and hardly on surface *** is possible to deliver stellar radial velocities to a precision of about 3 kms^(-1)for AFGKM stars,and about 10 km s^(-1)for OB stars,at signal-to-noise ratio(SNR)of *** uncertainties using single GU/GV/GI band spectra are also *** the same SNR,the GU band performs best,the GV band the second best,and then the GI *** effects of spectral normalization and the imperfect template on velocity measurements are investigated and found to be very *** uncertainties caused by wavelength calibration are considered and found to be *** the possible precision of radial velocities,the CSST spectroscopic survey can enable interesting science such as searching for hyper-velocity *** of our results are also discussed.

关键词： methods:data analysis methods:statistical stars:fundamental parameters stars:kinematics and dynamics

Chain damage effects of multi-spaced plates by reactive jet impact

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2021年第2期17卷 393-404页

作者： Yuan-feng Zheng Cheng-hai Su Huan-guo Guo Qing-bo Yu hai-fu Wang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China

Chain damage is a new phenomenon that occurs when a reactive jet impacts and penetrates multispaced *** reactive jet produces mechanical perforations on the spaced plates by its kinetic energy(KE),and then results in unusual chain rupturing effects and excessive structural damage on the spaced plates by its deflagration *** the present study,the chain damage behavior is initially demonstrated by *** reactive liners,composed of 26 wt%Al and 74 wt%PTFE,are fabricated through a pressing and sintering *** reactive liner thicknesses of 0.08 CD,0.10 CD and 0.12 CD(charge diameter)are chosen to carry out the chain damage *** results show a chain rupturing phenomenon caused by reactive *** constant reaction delay time and the different penetration velocities of reactive jets from liners with different thicknesses result in the variation of the deflagration position,which consequently determines the number of ruptured plates behind the ***,the finite-element code AUTODYN-3D has been used to simulate the kinetic energy only-induced rupturing effects on plates,based on the mechanism of behind armor debris(BAD).The significant discrepancies between simulations and experiments indicate that one enhanced damage mechanism,the behind armor blast(BAB),has acted on the ruptured ***,a theoretical model is used to consider the BAB-induced enhancement,and the analysis shows that the rupturing area on aluminum plates depends strongly upon the KE only-induced pre-perforations,the mass of reactive materials,and the thickness of plates.

关键词： Reactive materials Reactive jet Chain damage Behind armor blast

Integer Programming Model for Maximum Clique in Graph

在线全文

学校读者我要写书评

暂无评论

Journal of China University of Mining and Technology 2005年第1期15卷 77-80页

作者： YUANXi-bo YANGYou ZENGXin-hai SchoolofInformationandElectricalEngineering ChinaUniversityofMining＆TechnologyXuzhouJiangsu221008China SchoolofScience ChinaUniversityofMining＆TechnologyXuzhouJiangsu221008China

The maximum clique or maximum independent set of graph is a classical problem in graph theory. Com- bined with boolean algebra and integer programming, two integer programming models for maximum clique problem, which improve the old results were designed in this paper. Then, the programming model for maximum independent set is a corollary of the main results. These two models can be easily applied to computer algorithm and software, and suitable for graphs of any scale. Finally the models are presented as Lingo algorithms, verified and compared by sev- eral examples.

关键词： integer programming graph theory clique lingo

Causes and detection of coalfield fires, control techniques, and heat energy recovery: A review

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2020年第3期27卷 275-291页

作者： He-tao Su Fu-bao Zhou bo-bo Shi hai-ning Qi Jin-chang Deng School of Engineering and Technology China University of Geosciences(Beijing)Beijing 100083China Key Laboratory of Gas and Fire Control for Coal Mines(China University of Mining and Technology) Ministry of EducationXuzhou 221116China Key Laboratory of Deep GeoDrilling Technology Ministry of Natural ResourcesChina University of Geosciences(Beijing)Beijing 100083China

Coalfield fires are considered a global crisis that contributes significantly to environmental destruction and loss of coal resources and poses a serious threat to human safety and health. In this paper, research related to the initiation, development, and evolution of coalfield fires is reviewed. The existing detection and control techniques of coalfield fires are also reviewed. Traditional firefighting is associated with waste of resources, potential risks of recrudescence, potential safety hazards, extensive and expensive engineering works, and power shortages. Recently,coalfield fires have been recognized as having significant potential for energy conservation and heat energy recovery. Thermoelectric power generation is regarded as a suitable technology for the utilization of heat from coalfield fires. The extraction of heat from coalfield fires can also control coalfield fires and prevent reignition leading to combustion. Technologies for absorbing heat from burning coal and overlying rocks are also analyzed. In addition, the control mode of "three-region linkage" is proposed to improve firefighting efficiency. Integrating heat energy recovery with firefighting is an innovative method to control coalfield fires.

关键词： spontaneous coal combustion oxygen supply firefighting thermoelectric thermosyphon three-region linkage

Porous carbon/Fe composites from waste fabric for high-efficiency electromagnetic wave absorption

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2022年第31期126卷 266-274页

作者： Jin-bo Cheng hai-bo Zhao Ai-Ning Zhang Yan-Qin Wang Yu-Zhong Wang Collaborative Innovation Center for Eco-Friendly and Fire-Safety Polymeric Materials(MoE) State Key Laboratory of Polymer Materials EngineeringNational Engineering Laboratory for Eco-Friendly Polymer Materials(Sichuan)College of ChemistrySichuan UniversityChengdu 610064China

Nowadays,a large amount of waste fabrics has brought huge environmental and resource problems,while the traditional recycling routes are downcycling with low efficiency and complex separation ***,we demonstrate a green and facile route to up-recycle waste fabrics(cotton-polyester blending or cotton fabrics)into a high-performance microwave *** this design,an assistant coating was deposited onto the fiber surface of the waste fabric through the assembly of tannic acid-Fe^(2+)(TA-Fe^(2+)),which effectively catalyzed the polymer fiber into highly graphitized porous carbon fiber at high ***,the Fe nanoparticles from the reduction of Fe^(2+)ions were evenly embedded on the surface of porous carbon ***,the resultant porous carbon/Fe composites with hierarchi-cal microstructures displayed excellent microwave absorption ***,the microwave ab-sorber from waste polyester-cotton blended fabric could reach a minimum reflection loss(RL)of-50.5 dB at a thin coating thickness of 1.7 mm,and the minimum RL from waste cotton fabric absorber reached-47.1 dB at a thickness of 2.5 *** work provides a new idea to convert waste fabrics into high value-added microwave absorbing materials in a simple and environmentally friendly way,which will help reuse resources and protect the environment.

关键词： Up recycling Microwave absorption Waste fabrics Thin thickness

Microstructure and mechanical properties of AZ31 magnesium alloy reinforced by I-phase

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2019年第8期38卷 733-738页

作者： hai-Rong Wu Wen-bo Du Shu-bo Li Ke Liu Zhao-Hui Wang School of Materials Science and Engineering Beijing University of Technology

The particles of Mg-Zn-Gd icosahedral quasicrystal master alloy were added into the AZ31 alloy by the repeated plastic working(RPW)process in order to improve the mechanical properties of the AZ31 alloy at room *** microstructure and tensile properties of composites were investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and tensile testing machine at room *** results suggest that the RPW process can effectively refine the matrix and make the I-phase particles distribute *** ultimate tensile strength and the yield strength of the composites reach their maximum values of 362.3 and 330.5 MPa,respectively,when the amount of I-phase particles added is10 %.Meanwhile,the elongation of the composites decreases sharply.

关键词： I-phase Reinforced composite Repeated plastic working Mechanical property