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Electromagnetoelastic behaviors of functionally graded piezoelectric solid cylinder and sphere

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Acta Mechanica Sinica 2007年第1期23卷 55-63页

作者： h. L. Dai Y.M. Fu j.h. Yang Department of Engineering Mechanics Hunan University Changsha 410082 China

Analytical studies on electromagnetoelastic behaviors are presented for the functionally graded piezoelectric material （FGPM） solid cylinder and sphere placed in a uniform magnetic field and subjected to the external pressure and electric loading. When the mechanical, electric and magnetic properties of the material obey an identical power law in the radial direction, the exact displacements, stresses, electric potentials and perturbations of magnetic field vector in the FGPM solid cylinder and sphere are obtained by using the infinitesimal theory of electromagnetoelasticity. Numerical examples also show the significant influence of material inhomogeneity. It is interesting to note that selecting a specific value of inhomogeneity parameter β can optimize the electromagnetoelastic responses, which will be of particular importance in modern engineering designs.

关键词： Functionally graded piezoelectric material (FGPM) Electromagnetoelastic Solid cylinder Solid sphere Perturbation of magnetic field vector

Shell biorefinery: A comprehensive introduction

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Green Energy & Environment 2018年第4期3卷 318-327页

作者： Max j.hlsey Department of Chemical and Biomolecular Engineering National University of Singapore

Biomass refinery is considered to be a key technology in the 21 st century due to the importance of the sustainable production of various bioderived fuels and fine chemicals. Besides the synthesis of oxygen-containing chemicals mainly from lignocellulosic biomass, nitrogencontaining chemicals belong to some of the most important commodity and fine chemicals. In this introductory short review, the main similarities and difficulties between petroleum oil-and biorefinery will be discussed and future challenges will be highlighted. As a particular example, recent developments in the shell biorefinery – the utilization of shell waste – will be reviewed. Particular emphasis will be placed on the structure of shell biomass, the current and emerging fractionation methods and the conversion of chitin and chitosan to various heteroatomcontaining chemicals. This review is meant to provide an introduction to beginners in the field of biorefinery as well as a comprehensive discussion of recent proceedings in the field of shell biorefinery. An outlook on the future potential and challenges will be given.

关键词： Shell biorefinery

Possible Origin of Magnetic Fields in Very Dense Stars

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Chinese Physics Letters 2004年第11期21卷 2117-2119页

作者： A.PérezMartínez h.PérezRojas h.j.MosqueraCuesta GrupodeFisicaTeorica ICIMAFCalleENo.309VedadoLaHabanaCuba CentroBrasileirodePesquisasFísicas LaboratóriodeCosmologiaeFísicaExperimentaldeAltasEnergiasRuaDr.XavierSigaud150Cep22290-180.UrcaRiodeJaneiroRJBrazil

We discuss the bosonization of a relativistic very dense Fermi gas in a magnetic field and the consequent Bose-Einstein condensation of the resulting relativistic vector gas of charged particles. The model may be applied to paired spin-up electrons. We show that such systems may maintain self-consistently magnetic fields of order 10(10) - 10(13) G. That pairing could be the origin of large magnetic fields in some white dwarfs and neutron stars. For fields large enough (similar to10(13) for white dwarfs), the system becomes unstable and collapses.

关键词： Quantum gases liquids and solids Gravitation and cosmology Statistical physics and nonlinear systems Astrophysics and astroparticles

Achieving excellent strength-ductility synergy in twinned NiCoCr medium-entropy alloy via Al/Ta co-doping

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journal of Materials Science & Technology 2021年第28期87卷 184-195页

作者： D.D.Zhang h.Wang j.Y.Zhang h.Xue G.Liu j.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an710049PR China Science and Technology on Reactor Fuel and Materials Laboratory Nuclear Power Institute of ChinaChengdu610041PR China

Alloying is an effective strategy to tailor microstructure and mechanical properties of metallic materials to overcome the strength-ductility trade-off *** this work,we combined a novel alloy design principle,*** pronounced solid solution hardening(SSh)based on the misfit volumes engineering,and simultaneously,architecting the ductile matrix based on the valence electron concentrations(VEC)criterion,to fulfill an excellent strength-ductility synergy for the newly emerging high/medium-entropy alloys(hEAs/MEAs).Based on this strategy,Al/Ta co-doping within NiCoCr MEA leads to an efficient synthetic approach,that is minor Al/Ta co-doping not only renders significantly enhanced strength with notable SSh effect and ultrahigh strain-hardening capability,but also sharply refines grains and induces abnormal twinning behaviors of(NiCoCr)_(92)Al_(6)Ta_(2) *** with the partially twinned NiCoCr MEA,the yield strength(σy)and ultimate tensile strength(σUTS)of fully twinned Al/Ta-containing MEA were increased by~102%to~600 MPa and~35%to~1000 MPa,respectively,along with good ductility beyond 50%.Different from the NiCoCr MEA with deformation twins(DTs)/stacking faults(SFs)dominated plasticity,the extraordinary strain-hardening capability of the solute-hardened(NiCoCr)_(92)Al_(6)Ta_(2) MEA,deactivated deformation twinning,originates from the high density of dislocation walls,microbands and abundance of *** abnormal twinning behaviors,i.e.,prevalence of annealing twins(ATs)but absence of DTs in(NiCoCr)_(92)Al_(6)Ta_(2) MEA,are explained in terms of the relaxation of grain boundaries(for ATs)and the twinning mechanism transition(for DTs),respectively.

关键词： Medium-entropy alloys Mechanical properties Solid solution hardening Twinning behavior Strength-ductility synergy

A novel Mg-Gd-Y-Zn-Cu-Ni alloy with excellent combination of strength and dissolution via peak-aging treatment

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journal of Magnesium and Alloys 2023年第2期11卷 720-734页

作者： Y.h.Liu Z.R.Zhang j.Wang Y.Li h.X.Li L.Y.jia j.h.Wang j.S.Zhang State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China Dekai Intelligent Casting Co. Ltd.Hebei 072750China

Inferior absolute strength and dissolution properties are the main bottlenecks for the widespread application of dissolvable magnesium alloys in complex working environments for unconventional oil and gas ***,a novel functional peak-aged Mg-9.5Gd-2.7Y-0.9Zn-0.8Cu-0.4Ni(wt.%) alloy for fracturing tools is reported,and it possesses an ultimate tensile strength of 457.6 MPa,ultimate compressive strength of 620.7 MPa and dissolution rate of ~43.7 mg·cm^(-2)·h^(-1) in 3 wt.% KCl solutions at 93℃.The excellent strength of the agedalloy is primarily attributed to the combination of grain refinement,long-period stacking ordered(LPSO) strengthening,and precipitation strengthening induced by stacking fault and β’ phase,among which the precipitation strengthening is *** investigations confirm that the corrosion is triggered from the micro-galvanic coupling between the Mg matrix and the cathodic lamellar and block LPSO ***-shaped corrosion pits along with LPSO phases are subsequently formed,significantly accelerating *** β’ precipitates can effectively improve the strength without compromising the dissolution rate because of their nanoscale *** study provides an excellent material selection for dissolvable fracturing tools and presents a strategy by which a synergistic combination of strength and dissolution rate is achieved via peak-aging treatment.

关键词： Dissolvable magnesium alloy Peak-aging treatment Mechanical properties Micro-galvanic corrosion

Structural basis for the cold activation and adaptation of an a-agarase from marine bacterium Catenovulum agarivorans STB13

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FOOD BIOSCIENCE 2023年第3期53卷 1471-1478页

作者： Xie, Wenyan You, Yuxian ban, Xiaofeng Zhang, Anqi Li, Caiming Gu, Zhengbiao Li, Zhaofeng jiangnan Univ State Key Lab Food Sci & Technol Wuxi 214122 Peoples R China jiangnan Univ Sch Food Sci & Technol Wuxi 214122 Peoples R China jiangnan Univ Collaborat Innovat Ctr Food Safety & Qual Control Wuxi 214122 Peoples R China Yixing Inst Food & Biotechnol Co Ltd Yixing 214200 Peoples R China

Enzymes have high activity at low temperatures are defined as cold-adapted enzymes, but few enzymes show an activation effect after low-temperature incubation. In this study, we cloned an agarase from the marine bacte-rium Catenovulum agarivorans STB13 (Ca-AGA) and expressed the protein in Bacillus subtilis. The enzyme exhibited a peculiar cold activation, which was enhanced by 5-fold after incubation at-20 degrees C or 4 degrees C for 6 h. Fluorescence and CD spectra studies confirmed the secondary and tertiary structural changes in Ca-AGA at low temperature, which formed compact protein structures after low-temperature treatment. The enzyme also showed outstanding cold adaptation, retaining approximately 60% of its maximum activity at 10 degrees C. Based on a bioinformatics analysis, the carbohydrate-binding modules (CBMs) and long linker region were presumed to play a crucial role in cold adaptation due to a relatively high percentage of acidic residues and a negative charge density compared to the catalytic domain. A mutation that truncated the linker-CBM region resulted in a 59.97% reduction of the activity at 10 degrees C. This study describes an a-agarase of cold activation and adaptation in detail, which may have great potential for producing functional agaro-oligosaccharides in food and pharmaceutical industrial applications at ambient temperature.

关键词： alpha-agarase Cold activation Cold adaptation Carbohydrate-binding module Linker Agaro-oligosaccharides

Structural Damage Detection Using a Modified Artificial Bee Colony Algorithm

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Computer Modeling in Engineering & Sciences 2016年第4期111卷 335-355页

作者： h.j.Xu Z.h.Ding Z.R.Lu j.K.Liu Department of Mechanics Sun Yat-sen UniversityGuangzhou 510006China

An optimization approach based on Artificial Bee Colony(ABC)algorithm is proposed for structural local damage detection in this *** objective function for the damage identification problem is established by structural parameters and modal assurance criteria(MAC).The ABC algorithm is presented to solve the certain objective *** the Tournament Selection Strategy and chaotic search mechanism is adopted to enhance global search ability of the certain algorithm.A coupled double-beam system is studied as numerical example to illustrate the correctness and efficiency of the propose *** simulation results show that the modified ABC algorithm can identify the local damage of the structural system efficiently even under measurement noise,which demonstrates the proposed algorithm has a higher damage diagnosis precision.

关键词： structural damage detection Artificial Bee Colony algorithm Modal Assurance Criteria coupled double-beam system Tournament Selection Strategy

MAKING DUCTILE CAST IRON WITh ESR PROCESS

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Acta Metallurgica Sinica(English Letters) 1998年第3期11卷 169-174页

作者： S.j.Chu h.h.Lou Q.Niu Univ of Science and Technology Beijing Beijing China

Making ductile cast iron with ESR process under D.C. condition without adding spheroidizing inoculant alloys has been studied in laboratory. The key operation of ESR for cast iron is increasing the silicon content in unrefined consumable electrodes of flake graphite cast iron and using CaF2-based slags containing rare-earth or basic oxides and magnesium fluoride. The samples excel ductile cast iron produced by general technological process in fatigue strength and sealing performance.

关键词： ductile cast iron electroslag remelting nodulizing element

ON ThE DYNAMIC ChARACTERISTICS OF MOULD-FILLING UNDER COUNTERGRAVITY

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Acta Metallurgica Sinica(English Letters) 1997年第5期10卷 409-414页

作者： Zeng, j.M. Gu, h. Zhou, Y.h. Guangxi Univ Nanning China

In this paper, the mathematical models for mould-filling under countergravity are derived on the basis of the principle of momentum. Dynamic processes of mould-filling are observed on a perspex model by means of high speed photography. The results indicate that the mould-filling under countergravity can be described by the second order nonlinear differential equations characterized by damping oscillations. The velocity oscillations amplify as the pressuring speed increases if the pressure differential functions are of the same type. On the other hand, if the functions are of different type, then the velocity oscillations depend upon whether the functions progressively increase or decrease. Velocity oscillations can be diminished dramatically by increasing the local damping within the gating system.

关键词： casting mould-filling dynamics