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The refined theory of transversely isotropic piezoelectric rectangular beams

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science{1.(Physics,Mechanics & Astronomy) 2006年第4期49卷 473-486页

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 for symmetrical deformation

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science{1.(Physics,Mechanics & Astronomy) 2009年第6期52卷 919-925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 Aerospace Engineering, Peking university, beijing 100871, china college of {1. China Agricultural University Beijing China State Key Laboratory for Turbulence and Complex Systems and Department of Mechanics and Aerospace Engineering Peking University Beijing China

Based on elasticity theory, various one-dimensional equations for symmetrical deformation have been deduced systematically and directly from the two-dimensional theory of deep rectangular beams by using the Papkovich-Neuber solution and the Lur'e method without ad hoc assumptions, and they construct the refined theory of beams for symmetrical deformation. It is shown that the displacements and stresses of the beam can be represented by the transverse normal strain and displacement of the mid-plane. In the case of homogeneous boundary conditions, the exact solutions for the beam are derived, and the exact equations consist of two governing differential equations: the second-order equation and the transcendental equation. In the case of non-homogeneous boundary conditions, the approximate governing differential equations and solutions for the beam under normal loadings only and shear loadings only are derived directly from the refined beam theory, respectively, and the correctness of the stress assumptions in classic extension or compression problems is revised. Meanwhile, as an example, explicit expressions of analytical solutions are obtained for beams subjected to an exponentially distributed load along the length of beams.

关键词： deep rectangular beams the refined theory symmetrical deformation the Papkovich-Neuber solution the Lur’e method

Boundary conditions for the bending of a piezoelectric beam

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science{1.(Physics,Mechanics & Astronomy) 2008年第7期51卷 847-856页

作者： gao {1., 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 1.4044, china college of {1. 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

Pattern phenomena in an rf discharge dusty plasma system

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science{1.(Physics,Mechanics & Astronomy) 2006年第5期49卷 588-596页

作者： HUANG Feng1.2, YE Maofu2 & wang Long2 1. {1. of science, china agricultural university, beijing 100083, china 2. Institute of Physics, Chinese Academy of sciences, beijing 1.0080, china college of {1. 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

Mixed boundary conditions for piezoelectric plates

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science{1.(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 {1. 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

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 {1. of Resource and Environment science, china agricultural university, beijing 1.0094, china 2{1. of Animal science, Hebei agricultural university, Baoding 071.01. china college of Resource and Environment {1. China Agricultural UniversityBeijing 100094 China college of Animal {1. 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-1. column chromatography, and C-1. 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 OEP31.1. was obtained, with the molecular mass of 51..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{1.(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 31.030,{1. 2 college of Water Conservancy and Civil Engineering, china agricultural university, beijing 100083,{1. 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

Production of porcine cloned transgenic embryos expressing green fluorescent protein by somatic cell nuclear transfer

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science{1.(Life sciences) 2006年第2期49卷 164-171页

作者： ZHANG Yunhai1. PAN Dengke1.2, SUN Xiuzhu1. SUN Guojie1. wang Xiaobo1. LIU Xiaohui1. LI Yan1. DAI Yunping1.& LI Ning1.1. State Key Laboratory for Agrobiotechnology,{1., beijing 1.0094, china 2. college of Animal science and Technology,{1., beijing 1.0094, china State Key Laboratory for Agrobiotechnology China Agricultural University Beijing China college of Animal {1. and Technology China Agricultural University Beijing China

In the present study, nuclear transferred embryos (NTEs) were reconstructed by using pig fetal fibroblasts as donors; in vitro matured oocytes as recipients. The effects of G41. selection on donor cells, duration of IVM of prepubertal gilt oocytes; oxygen tension in IVM of oocytes were investigated. The results were as follows: (i) When G41. selected cells expressing GFP were used as donors, the cleavage rate of NTEs decreased drastically in comparison to NTEs derived from donors without antibiotic selection (47.5% vs. 71.6%, p>0.05). For the blastocyst rate, no significant difference was observed between two groups (1.% vs. 1..4%, p2 h (83.6% vs. 96.7%, p>0.05). However, no statistical difference was observed between NTEs derived from oocytes of 36 h IVM group; NTEs from oocytes of 42 h IVM group in the rates of cleavage (59.3% vs. 73.6%, p1..2%, p2) tension; NTEs derived from oocytes matured under higher oxygen tension (20% O2) in cleavage rate (70.6% vs. 67.1., p1..8% vs. 1..3%, p1. selection does not have a significant effect on cleavage rate of NTEs expressing GFP. (ii) Nuclear maturation is greatly improved by prolonging IVM duration from 36 to 42 h, while no significant differences were observed for developmental potential of transgenic embryos. Thus IVM 42 h is the better choice in order to obtain maximum number of MII oocytes as recipients. (iii) Lower oxygen tension; higher oxygen tension in IVM have no significant effect on development of cloned embryos.

关键词： transgenic cloning, GFP, Pig, early development.

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{1.(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 1.0094, china 2 Vocational and Technologic college, Inner Mongolia Agriculture university, Baotou 01.1.9, china 3 college of Veterinary Medicine, china agricultural university, beijing 1.0094, china college of Animal {1. 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=0.1.82) 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