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Journal of central South University 2015年第10期22卷 3738-3744页

作者： Mukesh c.Sharma Division of Drug Design & Medicinal chemistry Research Lab School of Pharmacy Devi Ahilya University Takshila Campus

A quantitative structure–activity relationship(QSAR) was performed to analyze antimalarial activities against the D10 strains of Plasmodium falciparum of triazole-linked chalcone and dienone hybrid derivatives using partial least squares regression coupled with stepwise forward–backward variable selection method. QSAR analyses were performed on the available Ic50 D10 strains of Plasmodium falciparum data based on theoretical molecular descriptors. The QSAR model developed gave good predictive correlation coefficient(r2) of 0.8994, significant cross validated correlation coefficient(q2) of 0.7689, r2 for external test set)(2predr of 0.8256, coefficient of correlation of predicted data set)(2sepred,r of 0.3276. The model shows that antimalarial activity is greatly affected by donor and electron-withdrawing substituents. The study implicates that chalcone and dienone rings should have strong donor and electron-withdrawing substituents as they increase the activity of chalcone. Results show that the predictive ability of the model is satisfactory, and it can be used for designing similar group of antimalarial compounds. The findings derived from this analysis along with other molecular modeling studies will be helpful in designing of the new potent antimalarial activity of clinical utility.

关键词： quantitative structure–activity relationship(QSAR) chalcone antimalarial Plasmodium falciparum stepwise forward–backward partial least squares

cold plasma redistribution throughout geospace

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Science china(Technological Sciences) 2016年第9期59卷 1340-1345页

作者： Foster John c. Massachusetts Institute of Technology Haystack Observatory

The redistribution of the electrically charged cold plasma of ionospheric origin involves the equatorial,low,mid,auroral,and polar-latitude regions in a multi-step,system-wide process linking the regions of *** with ground and space-based instruments characterize the geospace plume-regularly occurring channels of enhanced plasma density flowing at both ionospheric and magnetospheric *** in the SAPS channel transports the eroded material to the noontime cusp in the ionosphere and to the dayside magnetopause at high *** the fluxes of cold plume plasma traverse the cusp and enter the polar cap,they form the polar tongue of *** the cusp the plume plasma provides a rich source of heavy ions for the magnetospheric injection and acceleration via the mechanisms operative on those field lines.

关键词： plasmasphere ionosphere geospace GPS TEc ionospheric electric field plume

Efficiency of the motion amplification device with viscous dampers and its application in high-rise buildings

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Earthquake Engineering and Engineering Vibration 2009年第4期8卷 521-536页

作者： Henry c.Huang WSP Asia Ltd.

After nearly a decade of application and investigation, a motion amplification device with viscous dampers for energy dissipation has been recognized as an effective solution to mitigate wind or seismic excitation, especially for stiff structural systems. As a result of compensation of amplified motion, it has been proved that the efficiency of viscous damper largely depends on the motion amplification device configuration, particularly for device stiflhess. In this paper, a ＂scissor-jack＂ type of motion amplification device, called a ＂toggle brace damper＂ system, is studied. It is demonstrated that the efficiency of such a device reflected by its amplification factor is not merely a function of its geometric configuration, but is highly dependent on the support elements＇ stiffness as well, similar to the mechanism of a leverage arm. Accordingly, a mathematical model in terms of complex modulus of the viscous damper with consideration of the support brace＇s stiffness is established. The results indicate that the efficiency of the motion amplification device with viscous dampers significantly depends on the stiffness of the support elements. Other parameters, such as toggle brace configuration and damping values of the viscous damper, are studied and compared. As an application example, numerical analyses are conducted to study the dynamic performance of a 39-story office tower installed with toggle brace dampers constructed on soft soil in a reclaimed area, under a combined effect of the vortex shedding of an adjacent existing 52-story building and earthquakes. The results show that viscous dampers with a motion amplification system using a properly designed toggle brace device proved to be an effective solution to alleviate the external excitations.

关键词： motion amplification device vibration mitigation viscous damper energy dissipation toggle brace damper

Adjustable Mechanism for Walking Robots with Minimum Number of Actuators

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chinese Journal of Mechanical Engineering 2011年第5期24卷 760-766页

作者： GUHA Anirban AMARNATH c Department of Mechanical Enginering Indian Institute of Technology Bombay

Recent literature on walking robots deals predominantly with multi-degrees-of-freedom leg mechanisms and machines capable of adopting several *** paper explores the other end of the spectrum suggesting mechanisms derived from a four bar coupler curve for a one degree of freedom walking *** of the walk indicates that body of the robot is able to move with low variation in *** best strategy for changing the gait to enable the robot to walk over obstacles and the effect of change in length of different links are explored to open up the possibility of a two degree of freedom walking robot with the capability of changing its gait,suitable as a low cost unit for several *** rugged units would permit the use of an Ic engine as the primary source of power and could be of utility in installations where electronics may not be *** simple walking machines the foot of a leg is usually required to trace a D shaped curve with respect to the *** this paper we begin with a Hoecken mechanism capable of tracing such a *** foot is required to move parallel to itself and the same could be achieved using a six or eight link mechanism.A few such devices have been synthesized in this paper and their motion properties *** study also covers the possibility of providing adjustments to vary the step length and height of the foot＇s movement.

关键词： walking robot degree of freedom coupler curve gait

Finite Element Analysis of the contact Mechanics of ceramic-on-ceramic Hip Resurfacing Prostheses

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Journal of Bionic Engineering 2010年第3期7卷 244-253页

作者： Ahmet c.cilingir Department of Mechanical Engineering Sakarya University

ceramics are good alternative to metal as bearing couple materials because of their better wear resistance. A Finite Element(FE) study was performed to investigate the contact mechanics and stress distribution of ceramic-on-ceramic (cOc) hip resurfacingprostheses. It was focused in particular on a parametric study to examine the effects of radial clearance, loading,alumina coating on the implants, bone quality, and fixation of cup-bone interface. It was found that a reduction in the radialclearance had the most significant effect on the predicted contact pressure distribution among all of the parameters considered inthis study. It was determined that there was a significant influence of non-metallic materials, such as the bone underneath thebearing components, on the predicted contact mechanics. Stress shielding within the bone tissue was found to be a major concernwhen regarding the use of ceramic as an alternative to metallic resurfacing prostheses. Therefore, using alumina implantswith a metal backing was found to be the best design for ceramic resurfacing prostheses in this study. The loading, bone quality,and acetabular cup fixation conditions were found to have only minor effects on the predicted contact pressure distribution alongthe bearing surfaces.

关键词： contact mechanics hip resurfacing ceramic finite element analysis

Butt-welding Residual Stress of Heat Treatable Aluminum Alloys

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Journal of Materials Science & Technology 2007年第2期23卷 217-222页

作者： c.M. cheng Department of Industrial Education National Taiwan Normal University Taipei Taiwan China　

This study, taking three types of aluminum alloys 2024-T351, 6061-T6 and 7075-T6 as experimental materials, conducted single V-groove GTAW （gas tungsten arc welding） butt-welding to analyze and compare the magnitude and differences of residual stress in the three aluminum alloys at different single V-groove angles and in restrained or unrestrained conditions. The results show that the larger the grooving angle of butt joint, the higher the residual tensile stress. Too small grooving angle will lead to dramatic differences due to the amount of welding bead filler metal and pre-set joint geometry. Therefore, only an appropriate grooving angle can reduce residual stress. While welding, weldment in restrained condition will lead to a larger residual stress. Also, a residual stress will arise from the restraint position. The ultimate residual stress of weldment is determined by material yield strength at equilibrium temperature. The higher the yield strength at equilibrium temperature, the higher the material residual stress. Because of its larger thermal conductivity, aluminum alloy test specimens have small temperature differential. Therefore, the residual tensile stress of all materials is lower than their yield strength.

关键词： Residual stress Hole-drilling strain-gage method Aluminum alloy Single-V groove

INTERMITTENcY AND ScALING IN TURBULENT cONVEcTION

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Acta Mechanica Sinica 2003年第5期19卷 385-393页

作者： EmilyS.c.cHING DepartmentofPhysics TheChineseUniversityofHongKongHongKongChina

Both the velocity and temperature measurements taken in turbulent Rayleigh-B'enard convection experiments have been analyzed. It is found that both the velocity and temperature fluctuations are intermittent and can be well-described by the She-Leveque hierarchical structure. A positive correlation between the vertical velocity and the temperature differences is found both at the center, near the sidewall and near the bottom of the convection cell, supporting that buoyancy is significant in the Bolgiano regime. Moreover, the intermittent nature of the temperature fluctuations in the Bolgiano regime can be attributted to the variations in the temperature dissipation rate. However, the relations between the velocity and temperature structure functions and their correlations implied by the Bolgiano-Obukhov scaling are not supported by experimental measurements.

关键词： turbulent convection intermittency scaling

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