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61.
Michael Wallin Ahmed K. Aboubakr Paramsothy Jayakumar Michael D. Letherwood David J. Gorsich Ashraf Hamed Ahmed A. Shabana 《Nonlinear dynamics》2013,74(3):783-800
This paper is focused on the dynamic formulation of mechanical joints using different approaches that lead to different models with different numbers of degrees of freedom. Some of these formulations allow for capturing the joint deformations using a discrete elastic model while the others are continuum-based and capture joint deformation modes that cannot be captured using the discrete elastic joint models. Specifically, three types of joint formulations are considered in this investigation; the ideal, compliant discrete element, and compliant continuum-based joint models. The ideal joint formulation, which does not allow for deformation degrees of freedom in the case of rigid body or small deformation analysis, requires introducing a set of algebraic constraint equations that can be handled in computational multibody system (MBS) algorithms using two fundamentally different approaches: constrained dynamics approach and penalty method. When the constrained dynamics approach is used, the constraint equations must be satisfied at the position, velocity, and acceleration levels. The penalty method, on the other hand, ensures that the algebraic equations are satisfied at the position level only. In the compliant discrete element joint formulation, no constraint conditions are used; instead the connectivity conditions between bodies are enforced using forces that can be defined in their most general form in MBS algorithms using bushing elements that allow for the definition of general nonlinear forces and moments. The new compliant continuum-based joint formulation, which is based on the finite element (FE) absolute nodal coordinate formulation (ANCF), has several advantages: (1) It captures modes of joint deformations that cannot be captured using the compliant discrete joint models; (2) It leads to linear connectivity conditions, thereby allowing for the elimination of the dependent variables at a preprocessing stage; (3) It leads to a constant inertia matrix in the case of chain like structure; and (4) It automatically captures the deformation of the bodies using distributed inertia and elasticity. The formulations of these three different joint models are compared in order to shed light on the fundamental differences between them. Numerical results of a detailed tracked vehicle model are presented in order to demonstrate the implementation of some of the formulations discussed in this investigation. 相似文献
62.
We demonstrate laser induced semiconductor–metal transition through an abrupt change in diamagnetic susceptibility of a donor at critical concentration in a GaAs/AlxGa1−xAs Quantum Well for finite barrier model in the effective mass approximation using variational principle. We have considered Anderson‘s localization due to the random distribution of impurities in our calculation. The nonparabolicity of the conduction band is also considered. Our results without laser field agree with the earlier theoretical results and also with the recent experimental results. 相似文献
63.
The hole-hole interaction $(E_{hh})$ has been considered in a ${\rm{CdTe /Cd}}_{1-x}{\rm {Mn}}x{\rm {Te}}$ Semimagnetic Quantum Well Wire (SQWW). The influence of the shape of the confining potential like square well and parabolic well type on the binding energy of an acceptor impurity with two holes and their Coulomb interaction between them has been studied for various impurity locations. Magnetic field has been used as a probe to understand the carrier-carrier correlation in such Quasi 1-Dimensional QWW since it alters the strength of the confining potential tremendously. In order to show the significance of the correlation between the two holes, the calculations have been done with and without including the correlation effect in the ground state wavefunction of the hyderogenic acceptor impurity and the results have been compared. The expectation value of the Hamiltonian, ${H}$, is minimized variationaly in the effective mass approximation through which $(E_{hh})$ has been obtained. 相似文献
64.
Hideaki Nagahama Nitar New Rangasamy Jayakumar Tetsuya Furuike Hiroshi Tamura 《Macromolecular Symposia》2008,264(1):8-12
Chitin, a natural abundant polysaccharide, have been investigated as prospected biochemical material due to its several biological advantages. It is insoluble in the most of the organic solvents due to its rigid crystalline structure. However, chitin regenerated hydrogel (RG) has been prepared by using the saturated calcium solvent system under mild conditions. And also, swelling hydrogel (SG) was prepared by using water. In this study, we prepared the suspension of chitinous hydrogel, and applied to fabricated the chitinous compound/gelatin composite sheets. Additionally, N-acetyl D-(+)-glucosamine was added into some composite sheets. We investigated the mechanical properties and growth of NIH/3T3 fibroblast cell for the prepared composite sheet. 相似文献
65.
A polymer colloidal solution having dispersed nanoparticles of Cu and Au metals have been developed using a novel chemical method. Average size of the nanoparticles could be varied in the 4-10 nm range by conducting the reaction at an elevated temperature of 50-70 degrees C. Colloidal solutions of representative concentrations of 0.1-2.0 wt% Cu/Au contents in the primary solutions are used to study the modified ultrasonic attenuation and ultrasonic velocity in PVA polymer molecules on incorporating the Cu/Au particles. A characteristic behaviour of the ultrasonic velocity and the attenuation are observed at the particular temperature/particle concentration. The results demonstrate that the primary reaction during the nanoparticles-PVA colloidal formation occurs in divided groups in small micelles. The results are analyzed predicting the enhanced thermal conductivity of the samples. 相似文献
66.
A thorough investigation on the antimicrobial activity of RF air plasma and azadirachtin (neem leaf extract) treated cotton fabric has been dealt with in this paper. The cotton fabric was given a RF air plasma treatment to improve its hydrophilicity. The process parameters such as electrode gap, time of exposure and RF power have been varied to study their effect in improving the hydrophilicity of the cotton fabric and they were optimized based on the static immersion test results. The neem leaf extract (azadirachtin) was applied on fabric samples to impart antimicrobial activity. The antimicrobial efficacy of the samples have been analysed and compared with the efficacy of the cotton fabric treated with the antimicrobial finish alone. The investigation reveals that the RF air plasma has modified the surface of the fabric, which in turn increased the antimicrobial activity of the fabric when treated with azadirachtin. The surface modification due to RF air plasma treatment has been analysed by comparing the FTIR spectra of the untreated and plasma treated samples. The molecular interaction between the fabric, azadirachtin and citric acid which was used as a cross linking agent to increase the durability of the antimicrobial finish has also been analysed using FTIR spectra. 相似文献
67.
Jose P. Abraham D. Sajan Joseph Mathew I. Hubert Joe V. George V. S. Jayakumar 《Journal of Raman spectroscopy : JRS》2008,39(12):1821-1831
The oroxylin, 5,7‐dihydroxy 6‐methoxy flavone is a potent natural product extracted from ‘Vitex peduncularis’. Density functional theory (DFT) at B3LYP/6‐311G(d,p) level has been used to compute energies of different conformers of oroxylin to find out their stability, the optimized geometry of the most stable conformer and its vibrational spectrum. The conformer ORLN‐1 with torsion angles 0, 180, 180 and 0 degrees, respectively, for H13 O12 C6 C5, H14 O10 C4 C5, H13 O12 C6 C5 and H14 O10 C4 C5 is found to be most stable. The optimized geometry reveals that the dihedral angle φ between phenyl ring B and the chrome part of the molecule in − 19.21° is due to the repulsive force due to steric interaction between the ortho‐hydrogen atom H29 of the B ring and H18 of the ring C (H29·H18 = 2.198 Å). A vibrational analysis based on the near‐infrared Fourier transform(NIR‐FT) Raman, Fourier transform‐infrared (FT‐IR) and the computed spectrum reveals that the methoxy group is influenced by the oxygen lone pair‐aryl pz orbital by back donation. Hence the stretching and bending vibrational modes of the methoxy group possess the lowest wavenumber from the normal values of methyl group. The carbonyl stretching vibrations have been lowered due to conjugation and hydrogen bonding in the molecules. The intramolecular H‐bonding and nonbonded intramolecular interactions shift the band position of O10 H14 and O12 H13 stretching modes, which is justified by DFT results. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
68.
The molecular structure and conformational stability of CH2CHCH2X (X=F, Cl and Br) molecules were studied using ab initio and density functional theory (DFT) methods. The molecular geometries of 3-fluoropropene were optimized employing BLYP and B3LYP levels of theory of DFT method implementing 6-311+G(d,p) basis set. The MP2/6-31G*, BLYP and B3LYP levels of theory of ab initio and DFT methods were used to optimize the 3-chloropropene and 3-bromopropene molecules. The structural and physical parameters of the molecules are discussed with the available experimental values. The rotational potential energy surface of the above molecules were obtained at MP2/6-31G* and B3LYP/6-311+G(d,p) levels of theory. The Fourier decomposition of the rotational potentials were analyzed. The HF/6-31G* and MP2/6-31G* levels of theory have predicted the cis conformer as the minimum energy structure for 3-fluoropropene, which is in agreement with the experimental values, whereas the BLYP/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels of theory reverses the order of conformation. The ΔE values calculated for 3-chloropropene at MP2/6-31G*, BLYP/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels of theory show that the gauche form is more stable than the cis form, which is in agreement with the experimental value. The same levels of theory have also predicted that the gauche form is stable than cis for 3-bromopropene molecule. The maximum hardness principle has been able to predict the stable conformer of 3-fluoropropene at HF/6-31G* level of theory, but the same level of theory reverses the conformational stability of 3-chloropropene and 3-bromopropene molecules and MP2/6-31G* level of theory predicted the stable conformer correctly. 相似文献
69.
The liquid–metal magneto-hydrodynamic (LMMHD) facility at the Bhabha Atomic Research Centre (Mumbai) has a two-phase mercury–nitrogen
flow system which is currently used for various studies related to void-fraction, flow, pressure, slip-ratio, of the flow
system. Non-invasive measurements of steady-state void-fraction profiles has been carried out by a 60 mCi Cesium-137 gamma-ray
source and a NaI(Tl) detector mounted on a trolley. The reconstructed cross-sectional void-fraction profiles were in the riser
section of the LMMHD loop, and in this process radial tomographic methods were used, e.g. least-squares and chord-segment-inversion
(CSI). The present work investigates the possible uncertainties in the profiles thus measured. A simple statistical model
has been developed for the CSI algorithm due to the inherent “square nature” of the data matrix. The inherent Poisson error
has been also investigated in this exercise.
Received: 1 December 1997/Accepted: 30 May 1998 相似文献
70.
Krzysztof Ejsmont Jacek Zaleski Isaac H. Joe Victor S. Jayakumar 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(10):o553-o555
The structure of the title compound, 2C4H9N2O3+·C2O42−, which has been determined by X‐ray diffraction, contains discrete glycylglycine (HGly–Gly)+ cations in general positions and oxalate anions which lie across centres of inversion. Although the geometry of the (HGly–Gly)+ cation is not significantly different compared with other structures containing this residue, a few changes in conformation are observed which indicate the presence of molecular interactions. The molecular network in the crystal consists of one nearly linear O—H⋯O, five N—H⋯O and two weak C—H⋯O hydrogen bonds. 相似文献