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Energy principle of ferroelectric ceramics and single domain mechanical model

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Acta Mechanica Sinica 2007年第5期23卷 531-543页

作者： T.c.Wang LNM Institute of MechanicsChinese Academy of SciencesBeijing 100080China

Many physical experiments have shown that the domain switching in a ferroelectric material is a complicated evolution process of the domain wall with the variation of stress and electric field. According to this mechanism, the volume fraction of the domain switching is introduced in the constitutive law of ferroelectric ceramic and used to study the nonlinear constitutive behavior of ferroelectric body in this paper. The principle of stationary total energy is put forward in which the basic unknown quantities are the displacement ui, electric displacement Di and volume fraction pI of the domain switching for the variant I. Mechanical field equation and a new domain switching criterion are obtained from the principle of stationary total energy. The domain switching criterion proposed in this paper is an expansion and development of the energy criterion. On the basis of the domain switching criterion, a set of linear algebraic equations for the volume fraction PI of domain switching is obtained, in which the coefficients of the linear algebraic equations only contain the unknown strain and electric fields. Then a single domain mechanical model is proposed in this paper. The poled ferroelectric specimen is considered as a transversely isotropic single domain. By using the partial experimental results, the hardening relation between the driving force of domain switching and the volume fraction of domain switching can be calibrated. Then the electromechanical response can be calculated on the basis of the calibrated hardening relation. The results involve the electric butterfly shaped curves of axial strain versus axial electric field, the hysteresis loops of electric displacement versus electric filed and the evo- lution process of the domain switching in the ferroelectric specimens under uniaxial coupled stress and electric field loading. The present theoretic prediction agrees reasonably with the experimental results given by Lynch.

关键词： Ferroelectric ceramic Domain switching The volume fraction of domain switching Single domain mechanical model

Numerical Study on the Influence Mechanism of Inlet Distortion on the Stall Margin in a Transonic Axial Rotor

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Journal of Thermal Science 2012年第3期21卷 209-214页

作者： Scott c.Morris Hessert Laboratory Department of Mechanical and Aerospace EngineeringUniversity of Notre Dame

A numerical study is conducted to investigate the influence of inlet flow condition on tip leakage flow (TLF) and stall margin in a transonic axial rotor.A commercial software package FLUENT,is used in the *** rotor investigated in this paper is ND_TAc rotor,which is the rotor of one-stage transonic compressor in the University of Notre *** varied inlet flow conditions are *** inlet boundary condition with hub distortion provides higher axial velocity for the incoming flow near tip region than that for the clean inflow,while the incoming main flow possesses lower axial velocity near the tip region at tip distortion inlet boundary *** the total pressure ratio curves for the three inlet flow conditions,it is found that the hub dis-torted inlet boundary condition improves the stall margin,while the tip distorted inlet boundary condition dete-riorates compressor *** axial location of interface between tip leakage flow (TLF) and incoming main flow (MF) in the tip gap and the axial momentum ratio of TLF to MF are further *** is demonstrated that the axial momentum balance is the mechanism for interface *** hub distorted inflow could de-crease the axial momentum ratio,suppress the movement of the interface between TLF and MF towards blade leading edge plane and thus enhance compressor stability.

关键词： Inlet distortion tip leakage flow stall margin axial momentum balance

Numerical analysis of a magnetohydrodynamic duct flow with flow channel insert under a non-uniform magnetic field

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Journal of Hydrodynamics 2018年第6期30卷 1134-1142页

作者： c.N.Kim Department of Mechanical Engineering College of Engineering Kyung Hee University

This study performs a numerical analysis of three-dimensional liquid metal(LM) magnetohydrodynamic(MHD) flows in a square duct with an FcI in a non-uniform magnetic field. The current study predicts detailed information on flow velocity, Lorentz force, pressure, current and electric potential of MHD duct flows for different Hartmann numbers. Also, the effect of the electric conductivity of FcI on the pressure drop along the main flow direction in a non-uniform magnetic field is examined. The present study investigates the features of LM MHD flows in consideration of the interdependency among the flow variables.

关键词： Non-uniform magnetic field liquid metal blanket magnetohydrodynamic(MHD) duct flow flow channel insert

Benefits of laparoscopy-assisted ileostomy in colorectal cancer patients with bowel obstruction

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World Journal of clinical cases 2023年第24期11卷 5660-5665页

作者： Yi-Jie Wang Kuan-Hsun Lin Jung-cheng Kang je-Ming Hu chao-Yang chen Ta-Wei Pu Department of Surgery Tri Service General HospitalNational Defense Medical CenterTaipei 114Taiwan Division of Thoracic Surgery Department of SurgeryTri-Service General HospitalNational Defense Medical CenterTaipei 114Taiwan Division of colon and Rectal Surgery Department of SurgeryTaiwan Adventist HospitalTaipei 105Taiwan Division of colon and Rectal Surgery Department of SurgeryTri-Service General HospitalNational Defense Medical CenterTaipei 114Taiwan Division of colon and Rectal Surgery Department of SurgerySongshan branchTri-Service General HospitalNational Defense Medical CenterTaipei 105Taiwan

BAcKGROUND Ileostomies are commonly performed after colon and rectal ***-assisted ileostomy with adhesion lysis may have potential benefits over conventional open *** To compare the outcomes of laparoscopy-assisted and conventional *** Data from 48 consecutive patients who underwent ileostomy at our institution between May 2021 and May 2022 were retrospectively *** groups comprised 26 and 22 patients who underwent laparoscopic ileostomy(laparoscopic group)and conventional ileostomy(conventional group),respectively,performed by a single *** demographics,operative characteristics,postoperative outcomes,and 30-d morbidities and mortality rates were *** The two groups had comparable mean ages,sex distributions,American Society of Anesthesiologists scores,and body mass ***,the laparoscopic group showed similar operative time,better visualization for adhesion lysis,and lower visual analog scale scores than the conventional *** Laparoscopy-assisted ileostomy is a safe and efficient method that produces lower visual analog scale scores,better intraoperative visualization for effective adhesion lysis,and similar operative time compared with conventional ileostomy.

关键词： Laparoscopy Ileostomy colorectal cancer Bowel obstruction Tissue adhesion Retrospective study

A generic procedure for determining atomic LS spectral terms and their LS eigenfunctions

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chinese Physics B 2009年第2期18卷 542-548页

作者：熊庄 Bacalis N c AMS Research center Southeast University Theoretical and Physical chemistry Institute National Hellenic Research Foundation

This paper develops a Fortran code which is capable to construct the simplest LS eigenfunctions for desired symmetry and determine all permitted atomic LS spectral terms under a given orbital occupancy by implementing and extending the Schaefer and Harris method. Examples （in some cases the most complete set to date） of multiple spectroscopic terms of LS coupling of atomic states for both non-equivalent and equivalent electronic configurations are given. It also corrects a few observed errors from the recent literature.

关键词： LS coupling multiples spectroscopic term

How will biomining be applied in future?

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中国有色金属学会会刊：英文版 2008年第6期18卷 1302-1310页

作者： c.L.BRIERLEY Brierley consultancy LLc P.O.Box 630012Highlands Ranch

这篇论文在全世界考察商业 biomining 操作的当前的地位，识别作为一种处理技术驾驶 biomining 的选择的因素，描述挑战到利用这些革新，并且与 biomining 的未来的讨论得出结论。Biomining 商业地用设计垃圾场，堆和搅动的坦克被使用... 详细信息

这篇论文在全世界考察商业 biomining 操作的当前的地位，识别作为一种处理技术驾驶 biomining 的选择的因素，描述挑战到利用这些革新，并且与 biomining 的未来的讨论得出结论。Biomining 商业地用设计垃圾场，堆和搅动的坦克被使用。克服阴沉的费用的技术挑战，处理在矿的低档，低质量、复杂的矿石和利用存在大写的投资要求微生物引起的活动和创新工程的更好的理解。克服 biomining 广告挑战必要改进采矿 company/biomining 改革者合作和知识产权控制。

关键词：生物采矿生物浸取应用技术研究

Numerical Analysis of Deteriorated Sub-sea Pipelines under Environmental Loads

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chinese Journal of Mechanical Engineering 2015年第6期28卷 1163-1170页

作者： GücüYEN Engin Department of civil Engineering Faculty of Engineering Celal Bayar University

The significant point is the bidirectional interaction technique in FSI analysis while investigating subsea corrosion effect. By this way, pipe environment is accurately modelled and fluid effects are also considered. The effect of external corrosion defects on structural behaviour of a pipeline is studied by creating a nonlinear numerical model based on the finite element method according to ABAQUS analysis program. corrosion losses of sections are obtained from experimental results and applied to the model. Numerical model is formed by a span of sub-sea pipeline that is subjected to environmental loads. Seismic and wind-generated irregular wave loads are considered as environmental loads. Irregular wave is represented with equivalent eight regular waves via FFT. The pipe is modelled according to two different types which are non-corroded（intact） and corroded（deteriorated） to demonstrate corrosion effects on it. The visible type of corrosion in marine environment is named ‘pitting＇ corrosion, in which the material loss is locally interpenetrated over the surface. By considering this situation, the corroded and non-corroded pipes are modelled as 3D solid elements. The main point is revealing how the subsea corrosion affects the structural behaviour of pipelines on the basis of implementation of experimental results to a model structure due to changes of stresses and displacement.

关键词： offshore pipelines environmental loads corrosion numerical analysis

Semi-solid near-net shape rheocasting of heat treatable wrought aluminum alloys

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Transactions of Nonferrous Metals Society of china 2010年第9期20卷 1719-1724页

作者： U.A.c URLE Materials Science and Manufacturing Council for Scientific and Industrial Research

Flexibility of the cSIR-RcS, induction stirring with simultaneous air cooling process, in combination with high pressure die casting is successfully demonstrated by semi-solid rheocasting of plates performed on commercial 2024, 6082 and 7075 wrought aluminum alloys. Tensile properties were measured for the above mentioned rheocast wrought aluminum alloys in the T6 condition. The results showed that tensile properties were close to or even in some cases exceeded the minimum specifications. The yield strength and elongation of rheocast 2024-T6 exceeded the minimum requirements of the wrought alloy in the T6 condition but the ultimate tensile strength achieved only 90% of the specification because the Mg content of the starting alloy was below the commercial alloy specification. The strengths of rheocast 6082-T6 exceeded all of the wrought alloy T6 strength targets but the elongation only managed 36% of the required minimum due to porosity, caused by incipient melting during solution heat treatment, and the presence of fine intermetallie needles in the eutectic. The yield strength of rheocast 7075 exceeded the required one and the ultimate tensile strength also managed 97% of the specification; while the elongation only reached 46% of the minimum requirement also due to incipient melting porosity caused during the solution heat treatment process.

关键词： high pressure die casting (HPDc) aluminum alloys as-cast condition T6 treatment incipient melting

A simple criterion for finite time stability with application to impacted buckling of elastic columns

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Applied Mathematics and Mechanics(English Edition) 2018年第3期39卷 305-316页

作者： c.Q.RU Department of Mechanical Engineering University of Alberta

The existing theories of finite-time stability depend on a prescribed bound on initial disturbances and a prescribed threshold for allowable responses. It remains a challenge to identify the critical value of loading parameter for finite time instability observed in experiments without the need of specifying any prescribed threshold for al- lowable responses. Based on an energy balance analysis of a simple dynamic system, this paper proposes a general criterion for finite time stability which indicates that finite time stability of a linear dynamic system with constant coefficients during a given time interval [0, tf] is guaranteed provided the product of its maximum growth rate （determined by the maximum eigen-root pl 〉0） and the duration tf does not exceed 2, i.e., pltf 〈2. The proposed criterion （pltf=2） is applied to several problems of impacted buckling of elastic columns：（i） an elastic column impacted by a striking mass, （ii） longitudinal impact of an elastic column on a rigid wall, and （iii） an elastic column compressed at a constant speed （＂Hoff problem＂）, in which the time-varying axial force is replaced approximately by its average value over the time duration. comparison of critical parameters predicted by the proposed criterion with available experimental and simulation data shows that the proposed criterion is in robust reasonable agreement with the known data, which suggests that the proposed simple criterion （pltf---2） can be used to estimate critical parameters for finite time stability of dynamic systems governed by linear equations with constant coefficients.

关键词： finite time stability, buckling impact, elastic column, Hoff problem, dy-namic buckling, stability criterion