检索结果-南通市图书馆

Acta Metallurgica Sinica(English Letters) 1992年第9期5卷 178-182页

作者： QIAO Lijie LIU Rui XIAO Jimei university of Science and Technology beijing,beijing,china

The effects of stress components on nucleation sites and propagation directions of stress cor- rosion cracks in brass were investigated with specimens under mode Ⅱ and mode Ⅲ loadings. The results indicated that under mode Ⅱ loading,stress corrosion cracks nucleated on the site with maximum normal stress component and propagated along the plane perpendieular to the maximum normal stress,under mode Ⅲ loading,the stress corrosion crack was not evident on the 45°plane due to the general corrosion in aqueous solution with high NH_4OH concentra- tion,while stress corroded in aqueous solution with low NH_4OH concentration, numerous cracks with spacings of 10—150μm were found on the 45°plane with maximum normal stress and no stress corrosion cracks was observed on the plane with maximum shear stress.

关键词： stress corrosion cracking stress compoonent brass ammonia solution

General solution to diagonal model matching control of multiple-output-delay systems and its applications in adaptive scheme

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2009年第1期19卷 79-90页

作者： Yingmin Jia The Seventh Research Division,beihang university,beijing 100083.china The Seventh Research Division Beihang University Beijing 100083 China

This paper mainly studies the model matching problem of multiple-output-delay systems in which the reference model is assigned to a diagonal transfer function matrix.A new model matching controller structure is first developed,and then,it is shown that the controller is feasible if and only if the sets of Diophantine equations have common *** obtained controller allows a parametric representation,which shows that an adaptive scheme can be used to tolerate parameter variations in the *** resulting adaptive law can guarantee the global stability of the closed-loop systems and the convergence of the output error.

关键词： Model matching control Decoupling Adaptation Time delays Multivariable systems Diophantine equations

Stabilization control of a bumblebee in hovering and forward flight

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第1期25卷 13-21页

作者： Yan Xiong Mao Sun Institute of Fluid Mechanics, beihang university,beijing 100083, china Institute of Fluid Mechanics Beihang University Beijing China

Our previous study shows that the hovering and forward flight of a bumblebee do not have inherent stability （passive stability）. But the bumblebees are observed to fly stably. Stabilization control must have been applied. In this study, we investigate the longitudinal stabilization control of the bumblebee. The method of computational fluid dynamics is used to compute the control derivatives and the techniques of eigenvalue and eigenvector analysis and modal decomposition are used for solving the equations of motion. Controllability analysis shows that at all flight speeds considered, although inherently unstable, the flight is controllable. By feedbacking the state variables, i.e. vertical and horizontal velocities, pitching rate and pitch angle （which can be measured by the sensory system of the insect）, to produce changes in stroke angle and angle of attack of the wings, the flight can be stabilized, explaining why the bumblebees can fly stably even if they are passively unstable.

关键词： Insect - Hovering and forward flight - Stabilization control Navier-Stokes simulation Modal analysis

Filterless Photosensors with Intrinsic Color Perception and Flexibility

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2024年第5期40卷 894-900页

作者： ZHOU Hongtao XU beihang ZHENG Xinjia GONG Jinchao ZHANG Kaitong HE Yonglin Key Laboratory of Advanced Light Conversion Materials and Biophotonics School of Chemistry and Life ResourcesRenmin University of ChinaBeijing100872P.R.China School of Mathematics Renmin University of ChinaBeijing100872P.R.China

Sensing materials possessing intrinsic color perception are indispensable prerequisites for the development of filterless photosensors,which could eliminate the need for complex device designs and avoid color distortion in *** materials are constrained by complex processing methods and limited ***,a color-photosensitive array based on ionic liquid with selective photothermal conversion(ILSPC)has been developed for intrinsic color *** on the selective absorption,photothermal conversion,and thermosensitivity of ILSPC,a photo-thermo-electric sensing system has been ***,the versatility of the two algorithms has been validated in color reconstruction and electrical signal *** an exploration,the photosensitive array showcases promising color recognition capabilities,potentially propelling the evolution of flexible photosensors.

关键词： Ionic liquid Filterless Intrinsic color perception Selective photothermal conversion Photosensitive array

Enhancement of magnetism of Zn0.95Co0.05O films by p-type Cu+ doping

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2011年第1期21卷 31-35页

作者： Wei-chang HAO~(1,5),Jian-jun LI~2,Huai-zhe XU~3,Jia-ou WANG~4,Tian-min WANG~1 1.Center of Materials physics and Chemistry,beihang university,beijing 100083.china 2.department of Materials Science and Engineering, Anhui university of Science and Technology,Huainan 232001,china 3.department of physics,beihang university,beijing 100083.china 4.beijing Synchrotron Radiation Facility,Institute of High Energy physics, Chinese Academy of Sciences,100049,china 5.Key Laboratory of Micro-nano Measurement,Manipulation and physics, Ministry of Education,beihang university,beijing 100191,china Center of Materials physics and Chemistry Beihang University Beijing 100083 China Key Laboratory of Micro-nano Measurement Manipulation and Physics Ministry of Education Beihang University Beijing 100191 China department of Materials Science and Engineering Anhui University of Science and Technology Huainan 232001 China department of physics Beihang University Beijing 100083 China beijing Synchrotron Radiation Facility Institute of High Energy Physics Chinese Academy of Sciences 100049 China

Zn0.95Co0.05O and Zn0.91Co0.05Cu0.04O thin films were fabricated on Si（111） substrate by the reactive magnetron sputtering method at different O-Ar *** characterizations by X-ray diffractometry（XRD）,X-ray photo-electronic spectrum（XPS）, and electron paramagnetic resonance（EPR） indicate that the doped Cu ions substitute the Zn2+ions in the ZnO *** doped Cu ions are in Cu+and Cu2+mixture valence *** ferromagnetism of the Zn0.91Co0.05Cu0.04O film increases gradually the increasing Cu+ions *** results indicate that the increase of ferromagnetism is not owing to the magnetic contribution of Cu+ions themselves,but owing to the enhancement of magnetic interaction between Co ions,which suggests that p-type doping of Cu+ions plays an important role in mediating the ferromagnetic coupling between Co ions.

关键词： Zn0.95Co0.05O films Zn0.91Co0.05Cu0.04O films magnetic semiconductors magnetic coupling co-doping

Vertex solution theorem for the upper and lower bounds on the dynamic response of structures with uncertain-but-bounded parameters

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第3期25卷 367-379页

作者： Zhiping Qiu Xiaojun Wang Institute of Solid Mechanics, beihang university, 100083 beijing, china Institute of Solid Mechanics Beihang University Beijing China

The aim of this paper is to evaluate the effects of uncertain-but-bounded parameters on the dynamic response of structures. By combining the interval mathematics and the finite element analysis, the mass matrix, damping matrix, stiffness matrix and the external loads are represented as interval matrices and vector. With the help of the optimization theory, we present the vertex solution theorem for determining both the exact upper bounds or maximum values and the exact lower bounds or minimum values of the dynamic response of structures, in which these parameters reach their extreme values on the boundary of the interval mass, damping, stiffness matrices and the interval extemal loads vector. Three examples are used to illustrate the computational aspects of the presented vertex solution theorem.

关键词： Dynamic response Vertex solution theorem ,Uncertain-but-bounded parameters

Laser-field-induced magnon amplification in a magnetic semiconductor quantum well under an external magnetic field

在线全文

学校读者我要写书评

暂无评论

Journal of university of Science and Technology beijing 2003年第5期10卷 69-72页

作者： Peng Fengphysics department, university of Science and Technology beijing, beijing 100083, china Phys. Dept. Univ. of Sci. and Technol. Beijing Beijing 100083 China

The laser-field induced magnon amplification in a magnetic semiconductorquantum well under an external magnetic field was discussed, it is shown that when the laserfrequency is near to the electron cyclotron frequency, no matter how weaker the laser field is, themagnon amplification always occurs. In case of fixed laser frequency, the optical absorption ofmagnons obeys the definite selection rule to the laser field strength. The rate of change of magnonoccupation is calculated, and the amplification condition is given.

关键词： magnon amplification magnetic semiconductor quantum well laser field

MEAM Potential with Angular Dependence for TiAl

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2001年第1期20卷 13-17页

作者： Xiaodong Ni, Xitao Wang, Guoliang Chen (physics department, university of Science and Technology beijing, beijing 100083, china State Key Laboratory for Advanced Metals and Materials, university of Science and Technology beijing, beijing 100083, china) 北京科技大学新金属材料国家重点实验室北京 100083 北京科技大学北京 100083

The modified embedded atom method (MEAM) is an empirical extension of the embedded atom method (EAM) that includes angular forces. By fitted to the lattice constants, the cohesive energy, the APE (anti-phase boundary) energy, and the vacancy formation energy of TiAl, an accurate MEAM potential is obtained for the TiAl system with L10 structure. The calculation results of the properties of TiAl are in good agreement with experiments and the results of first principle (F.P.) calculations.

关键词： embedded atom method TiAl alloy angular dependence potential intermetallics

An eigenelement method and two homogenization conditions

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2009年第3期25卷 345-351页

作者： Yufeng Xing Xingming Wang The Solid Mechanics Research Center, beihang university, 100083 beijing, china The Solid Mechanics Research Center Beihang University Beijing China

Under inspiration from the structure-preserving property of symplectic difference schemes for Hamiltonian systems, two homogenization conditions for a representative unit cell of the periodical composites are proposed, one condition is the equivalence of strain energy, and the other is the deformation similarity. Based on these two homogenization conditions, an eigenelement method is presented, which is characteristic of structure-preserving property. It follows from the frequency comparisons that the eigenelement method is more accurate than the stiffness average method and the compliance average method.

关键词： Composites Homogenization ,The equivalence of strain energy Deformation similarityEigenelement method

Relationship among Parameters Evaluating Stress Corrosion Cracking

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2000年第5期16卷 504-508页

作者： Wuyang CHU+, Lijie QIAO and Yanbin WANG (department of Materials physics, university of Science and Technology beijing, beijing 100083, china) department of Materials physics University of Science and Technology Beijing Beijing 100083 China

The threshold stress, σc, for sulfide stress corrosion cracking (SCC) of seven pipeline steels and five other steels, the critical stress, Sc, for seven pipeline steels and two drill rod steels with various strengths and the susceptibility to SCC, IRA or σf(SCC)/σf, for four pipeline steels, two drill rod steels and five other steels were measured. The results showed that there are no definite relationships among σc, Sc and IRA or σf(SCC)/σ*** threshold stress for hydrogen induced cracking (HlC) during charging with loading in the H2S04 solution, σc(H), decreased linearly with logarithm of the concentration of diffusible hydrogen c0, i.e., σc(H)=A-B Inco for four pipeline steels. σc(H) obtained with a special cathodic current ic, which was corresponding to the diffusible hydrogen concentration during immersing in the H2S solution, were consistent with /c for sulfide SCC for four pipeline steels. Therefore, σc for sulfide SCC can be measured using dynamically charging in the H2SO4 solution with the special cathodic current ic.

关键词： SCC Relationship among Parameters Evaluating Stress Corrosion Cracking HIC