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Second mode unstable disturbance measurement of hypersonic boundary layer on cone by wavelet transform

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Acta Mechanica Sinica 2011年第4期27卷 488-493页

作者： Jian Han.Nan Jiang.Yan Tian Department of Mathematics,tianjin University,300072 tianjin,china Department of mechanics,tianjin University,300072 tianjin,china tianjin key laboratory of {12. engineering mechanics,300072 tianjin,china State key laboratory of Nonlinear mechanics,Institute of mechanics,Chinese Academy of Sciences,100190 Beijing,china Department of Mathematics Tianjin University Tianjin China Department of mechanics Tianjin University Tianjin China tianjin key {2. of modern engineering mechanics Tianjin China State key laboratory of Nonlinear {2. Institute of Mechanics Chinese Academy of Sciences Beijing China

Experimental investigation of hypersonic boundary layer instability on a cone is performed at Mach number 6 in a hypersonic wind tunnel. Time series signals of instantaneous fluctuating surface-thermal-flux are measured by Pt-thin-film thermocouple temperature sensors mounted at 2. stations on the cone surface in the streamwise direction to investigate the development of the unstable disturbance. Wavelet transform is employed as a mathematical tool to obtain the multi-scale characteristics of fluctuating surfacethermal-flux both in the temporal and spectrum space. The conditional sampling algorithm using wavelet coefficient as an index is put forward to extract the unstable disturbance waveform from the fluctuating surface-thermal-flux *** generic waveform for the second mode unstable disturbance is obtained by a phase-averaging technique. The development of the unstable disturbance in the streamwise direction is assessed both in the temporal and spectrum space. Our study shows that the local unstable disturbance detection method based on wavelet transformation offers an alternative powerful tool in studying the hypersonic unstable mode of laminar-turbulent transition. It is demonstrated that, at hypersonic speeds, the dominant flow instability is the second mode, which governs the course of laminar-turbulent transition of sharp cone boundary layer.

关键词： Hypersonic boundary layer. Sharp cone Insta-bility Wavelet transform

Two-dimensional thermoelasticity solution for functionally graded thick beams

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Science china(Physics,mechanics & Astronomy) 2006年第4期49卷 451-460页

作者： Lü Chaofeng1, CHEN Weiqiu1 & ZHONG Zheng2.1. Department of Civil engineering, Zhejiang University, Hangzhou 31002., china 2. {2. laboratory of Solid mechanics of Ministry of Education, School of Aerospace engineering and Ap- plied mechanics, Tongji University, Shanghai 2.0092. china Department of Civil engineering Zhejiang University Hangzhou 310027 China key laboratory of Solid {2. of Ministry of Education School of Aerospace Engineering Applied mechanics Tongji University Shanghai 200092 China

Two-dimensional thermoelasticity analysis of functionally graded thick beams is presented using the state space method coupled with the technique of differential quadrature. Material properties vary continuously and smoothly through the beam thickness, leading to variable coefficients in the state equation derived from the elasticity equations. Approximate laminate model is employed to translate the state equation into the one with constant coefficients in each layer. To avoid numerical instability, joint coupling matrices are introduced according to the continuity conditions at interfaces in the approximate model. The differential quadrature procedure is applied to discretizing the beam in the axial direction to make easy the treatment of arbitrary end conditions. A simply-supported beam with exponentially varying material properties is considered to validate the present method. Numerical examples are performed to investigate the influences of relative parameters.

关键词： state equation differential quadrature approximate laminate model joint coupling matrices thermal stresses.

Calculation of maximum ground movement and deformation caused by mining

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中国有色金属学会会刊：英文版 2011年第S3期21卷 562-569页

作者： LI Pei-xian1, 2. TAN Zhi-xiang1, 2. DENG Ka-zhong1, 2.1. key laboratory for Land Environment and Disaster Monitoring of State Bureau of Surveying and Mapping, {2. University of Mining and Technology, Xuzhou 2.1116, {2. 2. Jiangsu key laboratory of Resources and Environmental Information engineering, {2. University of Mining and Technology, Xuzhou 2.1116, {2. [a] key laboratory for Land Environment and Disaster Monitoring of State Bureau of Surveying and Mapping China University of Mining and Technology Xuzhou 221116 China [b] Jiangsu key laboratory of Resources and Environmental Information {2. China University of Mining and Technology Xuzhou 221116 China

In order to know the maximum mining ground deformation of arbitrary surface point, directions of the maximum surface tilt, curvature,horizontal displacement and horizontal deformation caused by multi-working faces were deduced based on probability integral method. The distribution forms of surface deformations in all direction φ∈[0, 2.] were obtained and also equations of maximum deformations were given based on calculation of mining ground deformation in direction φ. A mining subsidence analysis system was developed with VB6.0. The system implements the probability integral mining subsidence prediction with direct integration method, and it can avoid errors of arbitrary shaped working face subdivision of traditional method, and accuracy of mining subsidence prediction can be improved with the direct integral method. The system implements the contour chart and profile chart and also data analysis automation by manipulation of the SURFER kernel function and it complements the defect of existing subsidence prediction software. Calculation of maximum deformations caused by multi-working faces mining in a coal mine of Xuzhou, china was shown as application example. engineering application indicates that maximum deformation of mining ground surface can be calculated and analyzed by the system. The research provides a theoretical basis and calculation tool for mining subsidence prediction and analysis.

关键词： mining subsidence probability integral method movement and deformation system development

Influence of moisture content and time on the mechanical behavior of polymer material

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Science china(Technological Sciences) 2004年第5期47卷 595-607页

作者： ZHENG Gaofei1, 2. KANG Yilan1, SHENG Jing3, QIN Qinghua1, WANG Huaiwen1 & FU Donghui1 1. Department of mechanics, tianjin University, tianjin 300072, china 2. Department of mechanics, tianjin Polytechnic University, tianjin 300160, china 3. Department of Material engineering, tianjin University, tianjin 300072, china Correspondence should be addressed to Kang Yilan 1. Department of mechanics Tianjin University 300072 Tianjin China 2. Department of mechanics Tianjin Polytechnic University 300160 Tianjin China 3. Department of Material engineering Tianjin University 300072 Tianjin China

The effects of moisture content and time on mechanical behavior of polymer materials are investigated both theoretically and experimentally in this paper. An equivalence relationship between time intervals and the moisture content for polymer nylon-6 has been established by way of experimental observation and measured results. The relationship shows that there exists equivalence between moisture and service time in affecting mechanical properties. In other words, an increase in moisture can be replaced by prolonging acting time in producing the same effect on material properties. Consequently, a moisture-time superposition principle is presented based on the experimental results and the analogy of temperature-time superposition principle. Numerical results such as stress-strain curves with different moisture contents are presented to verify the applicability and correctness. The proposed method appears very promising in study on the effect of moisture content on mechanical behavior of polymer materials.

关键词： equivalence relationship of moisture-time, moisture content, mechanical properties, shift function.

Potential energy surfaces for low-lying electronic states of SO_2

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Science china Chemistry 2006年第4期49卷 289-295页

作者： LI Anyang1, SUO Bing2. WEN Zhenyi2.& WANG Yubin2.1. Shanxi key laboratory of Physico-inorganic Chemistry, Department of Chemistry, Northwest University, Xi’an 710069, {2. 2. Institute of modern Physics, Northwest University, Xi’an 710069, {2. 1. Shanxi key laboratory of Physico-inorganic Chemistry Department of Chemistry Northwest University Xi’an 710069 China 2. Institute of modern Physics Northwest University Xi’an 710069 China

The potential energy surfaces for the nine low-lying electronic states of SO2.have been constructed by using the multi-reference second order perturbation theory (MRPT2. with the basis set cc-pVTZ. The optimized geometries and the adiabatic excitation energies of these states are in good agreement with experiments and previous calculations. The crossings and avoided crossings dis- played in the potential energy surfaces are expounded.

关键词： cross of PES, MRPT2. SO2 (sulfur dioxide).

The integration of methanogenesis with denitrification and anaerobic ammonium oxidation in an expanded granular sludge bed reactor

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Journal of Environmental Sciences 2003年第3期15卷 423-432页

作者： ZHANG Dai-jun 1,2.(1. Department of Environmental Science, Chongqing University, Campus A, Chongqing 400044, china 2. key {2. for the Southwest china Resources Exploitation and Environmental Disaster Control engineering, Ministry of Education, china.) Department of Environmental Science Chongqing University China

The integration of methanogenesis with denitrification and anaerobic ammonium oxidation(ANAMMOX) was studied in an expanded granular sludge bed(EGSB) reactor in this work. Experimental results from the continuous treatment of wastewater with nitrite and ammonium, which lasted for 107 days, demonstrated that wastewater with high nitrite and ammonium could be anaerobically treated in an expanded granular sludge bed reactor. More than 91% to 97% of COD were removed at up to about 3.9 g COD/(L·d) of COD volumetric loading rate. More than 97% to 100% of nitrite was denitrified at up to about 0.8 g NO -_2.N/(L·d), which is 16 times higher than that in a conventional activated sludge system with nitrification/denitrification(0.05 gN/(L·d)). No dissimilatory reduction of nitrite to ammonium occurred in the process. However, maximum of about 40% ammonium was found to be lost. Batch tests of 15 days with sludge from the reactor showed that 100% of nitrite was denitrified completely, and about 3% of ammonium was removed when only ammonium (34.3 mg/L) and nitrite(34.3 mg/L) were added into the sludge suspension medium. Furthermore, about 15% of ammonium amounts were lost with organic COD addition. It suggested that the methanogenesis in the system could enhance ANAMMOX because of intermediate hydrogen produced during methanogenesis.

关键词： methanogenesis denitrification ANAMMOX EGSB reactor

Progress of synthesizing methods and properties of fluorinated carbon nanotubes

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Science china(Technological Sciences) 2010年第5期53卷 1225-1233页

作者： LI Yu1,2.CHEN YanFang1,2.FENG YiYu1,2.ZHAO ShengLing1,2.Lü Peng1,2.YUAN XiaoYan1,2.& FENG Wei1,2.1School of Materials Science and engineering,tianjin University,{2. 2.1} key laboratory of Composite and Functional Materials,tianjin 30072.china 1. School of Materials Science and engineering Tianjin University Tianjin 300072 China2. Tianjin Key Laboratory of Composite and Functional Materials Tianjin 30072 China

In this paper,the recent development of fluorinated carbon nanotubes(F-CNTs) was *** synthesizing methods of F-CNTs,including direct fluorination and plasma treatment,were discussed in detail,and the effects of factors,such as the temperature and pressure in fluorination as well as the kind of fluorine source and carbon nanotubes,on the structures and properties of F-CNTs were also *** the mean time,the special physical and chemical properties of F-CNTs and the relevant applied fields were described briefly,the exisiting problems of F-CNTs were summed up,and the direction of future development was also discussed in the end.

关键词： carbon nanotubes fluorination plasma treatment fluorinated carbon nanotubes substitution reaction

Alkylation mechanism of benzene with 1-dodecene catalyzed by Et_3NHCl-AlCl_3

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Science china Chemistry 2010年第5期53卷 1101-1106页

作者： QI GuoPeng 1,JIANG Feng 1,SUN XueWen 2.& ZHAO SuoQi 2.1School of Chemical engineering,tianjin University,{2. 2.tate key laboratory of Heavy Oil Processing,Petroleum University of china,Beijing 102.49,china 1. School of Chemical engineering Tianjin University Tianjin 300072 China2. State key Laboratory of Heavy Oil Processing Petroleum University of China Beijing 102249 China

The isotope exchange method was employed to investigate the catalytic mechanism of ionic liquid in alkylation of benzenes with *** is proposed that alkylation was induced by the Lewis acid AlCl3 which attracted π electrons of 1-dodecene to shift toward 1-carbon,thus forming a carbonium *** carbonium ion further reacted with benzenes to form a *** to unstabilit of the complex,a deuterated ring proton was transferred into an electronegative 1-carbon of the side chain to substitute for the AlCl3,accordingly 2.phenyldodecane was generated.

关键词： ionic liquid alkylation mechanism deuteriobenzene isotope exchange method

Piezoelectric Actuator/Sensor Wave Propagation Based Nondestructive Active Monitoring Method of Concrete Structures

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Journal of Wuhan University of Technology(Materials Science) 2011年第3期26卷 541-547页

作者：朱劲松 School of Civil engineering Tianjin University key laboratory of Coast Civil Structure Safety({2. University) Ministry of Education

In order to monitor the basic mechanical properties and interior damage of concrete structures,the piezoelectric actuator/sensor based wave propagation method was investigated experimentally in the laboratory using a specifically designed test *** energy attenuation of stress waves was measured by the relative index between the output voltage of sensors and the excitation voltage at the *** on the experimental results of concrete cube and cylinder specimens,the effect of excitation frequencies,excitation amplitude,wave propagation paths and the curing age on the output signals of sensors are *** results show that the relative voltage attenuation coefficient RVAC is an effective indicator for measuring the attenuation of stress waves through the interior of concrete.

关键词： piezoceramics actuator/sensor wave propagation method non-destructive evaluation (NDE) active monitoring concrete