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A COMPUTATIONAL METHOD ON PROCESS OPTIMAL CONTROL FOR FINITE DEFORMATION PROBLEMS

1999年

作者： James G. Mann y. A. liu.

来源：畅想之星图书光盘版（南... 评论

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畅想之星图书光盘版（南通市图书馆镜像）

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Acta Mechanica Solida Sinica 1998年第4期11卷 307-317页

作者： liu, y liu, BS SW Jiaotong Univ Res Sch Engn Sci Chengdu 610031 Peoples R China

On the principle of non-incremental algorithm, some basic ideas of process optimal control iterative algorithm, based on the Optimal Control Variational Principle in Mechanics, is proposed in this paper. Then the essential governing equations are presented. This work provides a new method to achieve the numerical solutions of the mechanic of finite deformation.

关键词： finite deformation numerical simulation non-incremental algorithm process optimal control

A perspective on age-related changes in cell environment and risk of neurodegenerative diseases

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Neural Regeneration Research 2024年第4期19卷 719-720页

作者： Alice y.liu Department of Cell Biology and Neuroscience Rutgers State University of New JerseyPiscatawayNJUSA

“Age-related neurodegenerative disease”underscores human age as the primary risk factor for disease development:Alzheimer’s,Parkinson’s,and Huntington’s disease(HD)as *** for the age-dependent delay in disease manifestation,in particular for autosomal dominant forms of the disease,and the underlying cause(s)of specific neuron dysfunction and death to manifest as memory loss,anxiety,depression,and agitation in disease subjects remain *** are interested in understanding age-related changes in cell environment that can modulate the structure,function,aggregation.

关键词： Huntington Alzheimer death

Dislocation ordering and texture strengthening of naturally aged Al-Cu-Mg alloy

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Journal of Materials Science & Technology 2022年第23期118卷 1-14页

作者： F.liu Z.y.liu G.y.He L.N.Ou School of Materials Science and Engineering Central South UniversityChangsha 410083China Key Laboratory of Nonferrous Metal Materials Science and Engineering Ministry of EducationCentral South UniversityChangsha 410083China National Key Laboratory of Science and Technology on High-Strength Structural Materials Central South UniversityChangsha 410083China

Stability of grain structure,dislocation ordering and strengthening mechanisms of the naturally aged AlCu-Mg alloy after solution treatment are investigated by using optical microscope(OM),scanning electron microscope(SEM),electron back-scattered diffraction(EBSD),X-ray diffraction(XRD) and transmission electron microscope(TEM).Results show that {100},{100},{110} and {110}slip systems can be activated after solution treatment,which can promote the formation of {110}Goss *** combination effect of T-Al_(20)Cu_(2) Mn_(3) phase and Goss-oriented grains with large Taylor factor makes the solution-treated alloys display excellent stability of grain *** enhanced yield strength of the alloy is ascribed to grain-refine strengthening,dispersed particles strengthening,dislocation strengthening and texture *** coarsening of the second phase is responsible for softening of the alloy after annealing at 400 ℃+solution treatment at 475 ℃.

关键词： Al-Cu-Mg alloy Dislocation ordering Goss texture Grain structure stability Texture strengthening

Study of Physicochemical Properties and Active Oxygen in Structures ofLayered Mixed La_(4)BaCu_(5-x)MxO_(13+λ)(M=Mn,Co)

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Journal of Rare Earths 1999年第2期17卷 52-56页

作者： liu, y yang, XG Wu, y Chinese Acad Sci Changchun Inst Appl Chem Changchun 130022 Peoples R China

Two series of layered mixed oxides La4BaCu5-xMxO13+(M=Mn, Co, x=05) were prepared and characterized by means of XRD, XPS, O2TPD and chemical analysis. The results show that their structures are 5layered ABO3 perovskite, and the XPS and O2TPD investigation confirms that there exists synergistic effect between Cu ion and M when M ion is doped into the lattice of La4BaCu5O13+, and the synergistic effect between Mn and Cu is stronger than that of CuCo.

关键词： Rare earths Layered mixed oxides Synergistic effect Active oxygen species

Vibration analysis of hard-coated composite beam considering the strain dependent characteristic of coating material

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Acta Mechanica Sinica 2016年第4期32卷 731-742页

作者： W.Sun y.liu School of Mechanical Engineering and Automation Northeastern University State Key Laboratory of Mechanical System and Vibration Institute of Vibration Shock and Noise Shanghai Jiao Tong University

The strain dependent characteristics of hard coatings make the vibration analysis of hard-coated composite structure become a challenging task. In this study, the modeling and the analysis method of a hard-coated composite beam was developed considering the strain dependent characteristics of coating material. Firstly, based on analyzing the properties of hard-coating material, a high order polynomial was adopted to characterize the strain dependent characteristics of coating materials. Then, the analytical model of a hard-coated composite beam was created by the energy method. Next, using the numerical method to solve the vibration response and the resonance frequencies of the composite beam, a specific calculation flow was also proposed. Finally,a cantilever beam coated with Mg O ＋ Al2_O_3 hard coating was chosen as the study case; under different excitation levels, the resonance region responses and the resonance frequencies of the composite beam were calculated using the proposed method. The calculation results were compared with the experiment and the linear calculation, and the correctness of the created model was verified. The study shows that compared with the general linear calculation, the proposed method can still maintain an acceptable precision when the excitation level is larger.

关键词： coated excitation modulus verified challenging characterize created considering acceptable polynomial

Frequency Veering of Rotating Metal Porous Twisted Plate with Cantilever Boundary Using Shell Theory

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Acta Mechanica Solida Sinica 2022年第2期35卷 282-302页

作者： y.y.liu y.X.Hao W.Zhang L.T.liu S.W.yang y.T.Cao College of Mechanical Engineering Beijing Information Science and Technology UniversityBeijing 100192China College of Mechanical Engineering Beijing University of TechnologyBeijing 100124China

The frequency veering of a metal porous rotating cantilever twisted plate with twist angle and stagger angle is *** porous materials may have the characteristics of gradient or uniform distribution along the thickness *** on the classical shell theory,considering the influence of centrifugal force produced by high-speed rotation,the free vibration equations of a rotating cantilever twisted plate are *** the polynomial function and Rayleigh-Ritz method,the natural frequencies and mode shapes of the metal porous cantilever twisted plate in both static and rotating states are *** accuracy of the present theory and calculation results is confirmed by a comparison between them and the results available from the literature and those obtained from *** influences of the thickness ratio,porosity,twist angle,stagger angle and rotational velocity on the frequency veering and mode shape shift of the rotating cantilever twisted plate with porous material under three different distributions are *** should be mentioned that the frequency veering accompanied by mode shape shift occurs in both static and dynamic states.

关键词： Frequency veering Rotating twisted plate Cantilever boundary Metal porous

Tectonic framework of China and its relation with mineral resources——Cognition from geophysical data

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维普期刊数据库

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Chinese Science Bulletin 1997年第2期42卷 89-95页

作者： liu, GD Hao, Ty liu, y Institute of Geophysics Chinese Academy of Sciences Beijing China

TECTONIC and its evolution are theoretical basis of geology and summation in geosciences from investigation of the earth’s structure, composition, motion and history. Therefore, they are of great importance to the industrial activities. Various geological maps have been compiled in different scales after long-time observation of rock outcrops in mountains and torrents. These tectonic maps, which are obtained based upon the cognition and judgment of tectonic movements in different ages, are summarization regarding the regularity of geological phenomenon in terms of theory, and provide service of exploration and references for environmental protection and prevention and control of disaster.

关键词： tectonic geophysics macroscopic framework.

Alloy solidification: Assessment and improvement of an easy-to-apply model

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Journal of Materials Science & Technology 2022年第35期130卷 1-11页

作者： H.liu y.liu S.L.Lu y.Zhang H.Chen y.Chen M.Qian School of Materials Science and Engineering Southwest Jiaotong UniversityChengdu 610031China Centre for Additive Manufacturing School of EngineeringRMIT UniversityMelbourneVIC 3000Australia School of Materials Science and Engineering Sichuan UniversityChengdu 610065China

It has been a central task of solidification research to predict solute microsegregation. Apart from the Lever rule and the Scheil-Gulliver equation, which concern two extreme cases, a long list of microsegregation models has been proposed. However, the use of these models often requires essential experimental input information, e.g., the secondary dendrite arm spacing(λ), cooling rate( ˙T) or actual solidification range(△T). This requirement disables these models for alloy solidification with no measured values for λ,˙T and △T. Furthermore, not all of these required experimental data are easily obtainable. It is therefore highly desirable to have an easy-to-apply predictive model that is independent of experimental input,akin to the Lever rule or Scheil-Gulliver model. Gong, Chen, and co-workers have recently proposed such a model, referred to as the Gong-Chen model, by averaging the solid fractions(f_(s)) of the Lever rule and Scheil-Gulliver model as the actual solid fraction. We provide a systematic assessment of this model versus established solidification microsegregation models and address a latent deficiency of the model, i.e.,it allows the Lever rule solid fraction fsto be greater than one(f_(s)> 1). It is shown that the Gong-Chen model can serve as a generic model for alloy solidification until fsreaches about 0.9, beyond which(f_(s)> 0.9) its applicability is dictated by both the equilibrium solute partition coefcient(k) and the solute diffusion coefcient in the solid(Ds), which has been tabulated in detail.

关键词： Solidification Microsegregation Solute Back diffusion Eutectic formation

Natural vibration of cantilever porous twisted plate with variable thickness in different directions

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Defence Technology（防务技术） 2023年第9期27卷 200-216页

作者： y.X.Hao y.y.liu W.Zhang L.T.liu K.C.Sun S.W.yang College of Mechanical Engineering Beijing Information Science and Technology UniversityBeijing100192PR China College of Mechanical Engineering Beijing University of TechnologyBeijing100124PR China

In this paper,the blade is assumed to be a rotating variable thickness cantilever twisted plate structure,and the natural vibrations of variable thickness cantilever twisted plate made of metal porous material are *** is assumed that the thickness of the plate changes along spanwise direction and chordwise direction,respectively,and it changes in both *** classical thin shell theory,the first and second fundamental forms of surface and von Karman geometric relationship are employed to derive the total potential energy and kinetic energy of the cantilever twisted plate,in which the centrifugal force potential due to high rotational speed is ***,according to the Rayleigh-Ritz procedure and applying the polynomial functions which satisfy the cantilever boundary conditions,the dynamic system expressed by equations of motion is reduced to an eigenvalue *** numerical simulation,the frequency curves and the mode shapes of the twisted plate can be obtained to reveal the internal connection between natural vibration and the parameters.A series of comparison studies are performed to verify the accuracy of the present formulation and calculations,in which compared data come from experimental,finite element method and theoretical calculation,*** influence of pre-twist angle,three different forms of thickness taper ratio and rotational speed on natural vibration,mode exchange and frequency veering phenomenon of the system is discussed in *** addition,the approach proposed here can efficiently extract analytical expressions of mode functions for rotating variable thickness cantilever twisted plate structures.

关键词： Porous cantilever twisted plate Variable thickness Natural vibration Frequency veering Mode exchange