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The refined theory of transversely isotropic piezoelectric rectangular beams

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science china(Physics,Mechanics & Astronomy) 2006年第4期49卷 473-486页

作者： gao yang1 & wang minzhong2 1. college of science, china agricultural university, beijing 100083, china 2. State Key Laboratory for Turbulence and Complex Systems and Department of Mechanics and Engi- neering science, Peking university, beijing 100871, china college of science China Agricultural University Beijing China State Key Laboratory for Turbulence and Complex Systems and Department of Mechanics and Engineering science Peking University Beijing China

The problem of deducing one-dimensional theory from two-dimensional theory for a transversely isotropic piezoelectric rectangular beam is investigated. Based on the piezoelasticity theory, the refined theory of piezoelectric beams is derived by using the general solution of transversely isotropic piezoelasticity and Lur'e method without ad hoc assumptions. Based on the refined theory of piezoelectric beams, the exact equations for the beams without transverse surface loadings are derived, which consist of two governing differential equations: the fourth-order equation and the transcendental equation. The approximate equations for the beams under transverse loadings are derived directly from the refined beam theory. As a special case, the governing differential equations for transversely isotropic elastic beams are obtained from the corresponding equations of piezoelectric beams. To illustrate the application of the beam theory developed, a uniformly loaded and simply supported piezoelectric beam is examined.

关键词： rectangular beams, the refined theory, piezoelectric, transversely isotropic.

The refined theory of deep rectangular beams based on general solutions of elasticity

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science china(Physics,Mechanics & Astronomy) 2006年第3期49卷 291-303页

The problem of deducing one-dimensional theory from two-dimensional the- ory for a homogeneous isotropic beam is investigated. Based on elasticity theory, the re- fined theory of rectangular beams is derived by using Papkovich-Neuber solution and Lur’e method without ad hoc assumptions. It is shown that the displacements and stresses of the beam can be represented by the angle of rotation and the deflection of the neutral surface. Based on the refined beam theory, the exact equations for the beam without transverse surface loadings are derived and consist of two governing differential equations: the fourth-order equation and the transcendental equation. The approximate equations for the beam under transverse loadings are derived directly from the refined beam theory and are almost the same as the governing equations of Timoshenko beam theory. In two ex- amples, it is shown that the new theory provides better results than Levinson’s beam the- ory when compared with those obtained from the linear theory of elasticity.

关键词： deep rectangular beams,the refined theory,Papkovich-Neuber solution,Lur'e method,governing equation

Boundary conditions for the bending of a piezoelectric beam

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science china(Physics,Mechanics & Astronomy) 2008年第7期51卷 847-856页

作者： gao yang1, XU SiPeng2 & ZHAO BaoSheng3 1 college of science, china agricultural university, beijing 100083, china 2 college of Engineering, Ocean university of china, Qingdao 266071, china 3 School of Mechanical Engineering, university of science and Technology Liaoning, Anshan 114044, china college of science China Agricultural University Beijing China college of Engineering Ocean University of China Qingdao China School of Mechanical Engineering University of Science and Technology Liaoning Anshan China

For beam bending in transversely isotropic piezoelectric media, the reciprocal theorem and the general solution of piezoelasticity are applied in a novel way to obtain the appropriate stress and mixed boundary conditions accurate to all orders for the beam of general edge geometry and loadings. By generalizing the method developed by Gregory and Wan, a set of necessary conditions on the edge-data for the existence of a rapidly decaying solution is established. The prescribed edge-data of the beam must satisfy these conditions in order that they could generate a decaying state within the beam. When stress and mixed conditions are imposed on the beam edge, these decaying state conditions for the case of bending deformation of piezoelectric beam are derived explicitly. They are then used for the correct formulation of boundary conditions for the beam theory solution (or the interior solution). Besides, an analytical solution of elastic beam is formulated to verify validity of our boundary conditions. For the stress data, our boundary conditions coincide with those obtained in conventional forms of beam theories. More importantly, the appropriate boundary conditions with two sets of mixed edge-data are obtained for the first time.

关键词： boundary conditions beam bending piezoelectric media decaying states regular states

Mixed boundary conditions for piezoelectric plates

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science china(Physics,Mechanics & Astronomy) 2009年第5期52卷 755-761页

作者： gao yang 1 ,XU SiPeng 2 &ZHAO BaoSheng 3 1college of science,china agricultural university,beijing 100083,china 2college of Engineering,Ocean university of china,Qingdao 266071,china 3 School of Mechanical Engineering,university of science and Technology of Liaoning,Anshan 114044,china college of science China Agricultural University Beijing China college of Engineering Ocean University of China Qingdao China School of Mechanical Engineering University of Science and Technology of Liaoning Anshan China

For plate bending and stretching problems in piezoelectric materials,the reciprocal theorem and the general solution of piezoelasticity are applied in a novel way to obtain the appropriate mixed boundary conditions accurate to all order.A decay analysis technique is used to establish necessary conditions that the prescribed data on the edge of the plate must satisfy in order that it should generate a decaying state within the *** the case of axisymmetric bending and stretching of a circular plate,these decaying state conditions are obtained explicitly for the first time when the mixed conditions are imposed on the plate *** are then used for the correct formulation of boundary conditions for the interior solution.

关键词： boundary conditions piezoelectric plates mixed data bending problems stretching problems

Pattern phenomena in an rf discharge dusty plasma system

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science china(Physics,Mechanics & Astronomy) 2006年第5期49卷 588-596页

作者： HUANG Feng1,2, YE Maofu2 & wang Long2 1. college of science, china agricultural university, beijing 100083, china 2. Institute of Physics, Chinese Academy of sciences, beijing 100080, china college of science China Agricultural University Beijing China Institute of Physics Chinese Academy of Sciences Beijing China

Various dust patterns are observed in an rf discharge dusty plasma system. According to the dust growth process from small to large in size, the formation of different dust patterns can be divided into two stages: the small-particle stage (or dust cloud stage), and the large-particle stage (or dust crystal stage). The evolution relations between different dust patterns with gas pressure changing are investigated. Dust voids, dust acoustic waves and strong turbulence modes are presented at the small-particle stage. The self-organized dust lattices and dust clusters are investigated at the large-particle stage. The static structure of a dust lattice is characterized by means of the pair correlation function. Dust clusters formed by particles with different numbers and the regular evolution of the clusters with gas pressure are also investigated. The packing sequences of dust clusters are verified through two-dimensional confined molecular dynamics simulations.

关键词： dusty plasma dust patterns

Purification of a Novel Antibacterial Short Peptide in Earthworm Eisenia foetida

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Acta Biochimica et Biophysica Sinica 2004年第4期36卷 297-302页

作者： Yan-Qin LIU1,2, Zhen-Jun SUN1*, Chong wang1, Shi-Jie LI2, and Yu-Zhi LIU2 college of Resource and Environment science, china agricultural university, beijing 100094, china 2college of Animal science, Hebei agricultural university, Baoding 071001, china college of Resource and Environment science China Agricultural UniversityBeijing 100094 China college of Animal science Hebei Agricultural UniversityBaoding 071001 China

A novel antimicrobial short peptide was purified from earthworm (Eisenia foetida) by a five-step protocol including ammonium sulfate precipitation, ultrafiltration, DE-52 ion exchange chromatography, Sephadex G-10 column chromatography, and C-18 reversed-phase HPLC techniques. The purified peptide was applied to the MALDI-TOF MS to determine the molecular mass and was also subjected to TOF MS-MS analysis to determine the amino acid sequence. As a result, a novel antibacterial peptide, named OEP3121, was obtained, with the molecular mass of 510.8 Da and the sequence being “ACSAG”.

关键词： antibacterial peptide earthworm purification

Computational theory of cavitating flows for hydraulic turbomachinery with consideration of influence of water quality

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science china(Technological sciences) 2010年第12期53卷 3341-3348页

作者： wang Lei1,2 & CHANG JinShi2 1 Huadian Electric Power Research Institute, Hangzhou 310030, china 2 college of Water Conservancy and Civil Engineering, china agricultural university, beijing 100083, china Huadian Electric Power Research Institute Hangzhou China college of Water Conservancy and Civil Engineering China Agricultural University Beijing China

Previously it was assumed that the pressure within the cavity or on the cavity surface remained constant and the vapor pressure of clean water at 20°C and 0 m altitude was utilized as the computational boundary for cavitating flows in hydraulic turbomachinery. Cavitation was confused with vaporization, and the effect of water quality on cavitation pressure characteristics was not taken into account. In recent years, lots of experiments of cavitation pressure characteristics of different water qualities including different sand concentrations of sand water and different altitudes of clean water have been performed by the authors, and the important influences of water quality on cavitation pressure characteristic have been validated. Thus the water quality should be involved in the cavitating flows computation. In the present paper, the effect of water quality on the cavitation pressure characteristic is analyzed and the computational method and theory of cavitating flows for hydraulic turbomachinery that considers the influence of water quality are proposed. The theory is suitable for both the potential flow method and the two-phase flow method for cavitating flows simulation. Finally, the validation results for cavitating flows in a hydraulic tur- bine indicate the significant influences of water quality on the cavitating flow performance.

关键词： cavitating flows cavitation pressure water quality hydraulic turbomachinery

Phototoxic effect of UVR on wild type, ebony and yellow mutants of Drosophila melanogaster: Life Span, fertility, courtship and biochemical aspects

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science china(Life sciences) 2008年第10期51卷 885-893页

作者： wang ZhePeng1,2, LIU RuiFang2, wang AnRu3, DU LiLi1 & DENG XueMei1 1 college of Animal science and Technology, china agricultural university, beijing 100094, china 2 Vocational and Technologic college, Inner Mongolia Agriculture university, Baotou 014109, china 3 college of Veterinary Medicine, china agricultural university, beijing 100094, china college of Animal science and Technology China Agricultural University Beijing China Vocational and Technologic college Inner Mongolia Agriculture University Baotou China college of Veterinary Medicine China Agricultural University Beijing China

Melanin plays an important role in protecting organisms from ultraviolet radiation (UVR). Therefore, it is possible that differently colored strains can show different sensitivities to UVR. In the present work, life span, fertility and courtship behavior of wild type (w), ebony (e) and yellow (y) strains of Drosophila melanogaster were studied to evaluate their sensitivity to ultraviolet (UV). Because a range of photo- toxic effects of UVR are mediated through generation of free radicals, levels of free radicals, lipid per- oxide (malondialdehyde, MDA) and superoxide dismutase (SOD) activity of three strains were examined to indicate their antioxidant defending ability and oxidative status. It was shown that w always had the highest lifespan and fertility not only in the control but also in UV-exposed groups. Moreover, lifespan and fertility of e were significantly higher (P1) than those of y in the UV-exposed groups, but not for the control. On the other hand, UV exposure had an adverse effect on courtship of flies. Stronger electron paramagnetic resonance (EPR) signals could be detected in w, e and y exposed to 5 min UV. And there were more significant changes of EPR signals in y than in w and e. UVR had no significant (P=0.1782) effect on the SOD activities. After pooling data from the control and UV-exposed groups, we found that w had a significantly (P0.05). MDA levels were increased in the UV dose-dependent manner (P=0.0495). In con- clusion, our results suggested that UVR can decrease life span and fertility of flies and do harm to courtship, which may be due to oxidative damage to flies tissues (e.g. central nervous system) induced by free radicals. w had the highest tolerance to UVR, which may be ascribed to its advantage of survival under the natural condition and at high level of SOD activity. Then differences of pigment between e and y in absorbing UV, shielding agai

关键词： ultraviolet radiation Drosophila melanogaste free radicals pigment

2D Ca/Nb-based perovskite oxide with Ta doping as highly efficient H_(2)O_(2)synthesis catalyst

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Nano Research 2024年第6期17卷 4934-4942页

作者： Xingchen yang yang gao Xiaohui Xu Wenqiang Xu Denghui wang Bin Luo Dong Liu Tao Liang Bin wang CAS Key Laboratory of Nanosystem and Hierarchical Fabrication National Center for Nanoscience and TechnologyBeijing 100190China university of Chinese Academy of sciences Beijing 100049China Nanomaterials Centre School of Chemical Engineering and Australian Institute for Bioengineering and Nanotechnologythe University of QueenslandSt LuciaQLD 4072Australia State Key Laboratory of Organic–Inorganic Composites College of Chemical EngineeringCollege of Materials Science and EngineeringBeijing University of Chemical TechnologyBeijing 100029China Hangzhou Institute for Advanced Study University of Chinese Academy of SciencesHangzhou 310024China State Key Lab of Silicon Materials Zhejiang UniversityHangzhou 310027China

Perovskite oxides(POs)are emerging as a class of highly efficient catalysts for reducing oxygen to H_(2)*** a rich variety of POs-based catalysts have been developed by tuning the complex composition,a highly efficient PO catalyst that is able to alter the reaction pathway from a 4e−process to a 2e−process for H_(2)O_(2)production has rarely been *** modified the structure and composition of a Ca-and Nb-based PO material by realizing a uniform two-dimensional(2D)morphology and varied Ta doping,resulting in the 2D Ca_(2)Nb_(3−x)Ta_(x)O_(10)−(x=0,0.5,1,and 1.5)monolayer *** obtained catalysts exhibit a dominant 2e−pathway and show exceptional H_(2)O_(2)production *** typical Ca_(2)Nb_(2.5)Ta_(0.5)O_(10)−nanoflakes showed an onset potential of 0.735 V *** hydrogen electrode(RHE),a remarkably high selectivity over 95%across a wide range of 0.3-0.7 V,an impressively high Faradaic efficiency of 94%,and a notable H_(2)O_(2)productivity of 1571 mmol·gcat^(−1)·h^(−1).These findings highlight the great potential of 2D perovskite oxide nanoflakes as advanced electrocatalysts for 2e−oxygen reduction reaction.

关键词： perovskite oxide H_(2)O_(2) two-electron oxygen reduction reaction catalyst Ca_(2)Nb_(3-x)Ta_(x)O_(10)-nanoflakes