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141.
In this paper, out-of-plane static behavior of circular nanobeams with point loads is investigated. Inclusion of small length scales such as lattice spacing between atoms, surface properties, grain size etc. are considered in the analysis by employing Eringen’s nonlocal elasticity theory in the formulations. The nonlocal equations are arranged in cylindrical coordinates and applied to the beam theory. The effect of shear deformation is considered. The governing differential equations are solved exactly by using the initial value method. The displacements, rotation angle about the normal and tangential axes and the force resultants are established and the analytical expressions are presented. The predicted trends of the size effect at the nano scale agree with those given in the experiments. The results can be used for designing nanoelectromechanical systems (NEMS) where the curved nanobeams are used as a basic component. 相似文献
142.
Synthesis,Antiviral, and Antimicrobial Activity of N‐ and S‐Alkylated Phthalazine Derivatives
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Ahmed H. Moustafa Hassan A. El‐Sayed Rasha A. Abd El‐Hady Abdelfattah Z. Haikal Maher El‐Hashash 《Journal of heterocyclic chemistry》2016,53(3):789-799
A series of N‐alkylphthalazinone were synthesized by the reaction of phthalazin‐1(2H)‐one derivatives 1a , 1b , 1c with alkylating agents namely, propargyl, allyl bromide, epichlorohydrin, 1,3‐dichloro‐2‐propanol, 4‐bromobutylacetate, and 1‐(bromomethoxy)ethyl acetate to give the corresponding N‐alkylphthalazinone 2a , 2b , 2c , 3a , 3b , 3c , 5a , 5b , 5c , 6a , 6b , 6c , 7a , 7b , 7c , and 9a , 9b , 9c . Alkylation of phthalazin‐1(2H)‐thione to give a series from S‐alkylphthalazine 12 , 13 , 14 and thioglycosides 15 and 17 was performed. Deprotection of compounds 7a , 7b , 7c , 9a , 9b , 9c , 15 , and 17 resulted in the formation of the corresponding products 8a , 8b , 8c , 10a , 10b , 10c , 16 , and 18 . The structure of newly synthesized compounds was assigned by IR, 1H, 13C NMR, and elemental analysis. Some of these compounds were screened for antiviral and antimicrobial activity. 相似文献
143.
A.S. Shalabi A.M. El Mahdy M.M. Assem H.O. Taha W.S. Abdel Halim 《Molecular physics》2014,112(1):22-34
Molecular electronic structure calculations, employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methodologies, have been carried out to improve the performance of the synthesised dye YD2-o-C8 which is characterised by 11.9%–12.7% efficiencies. We aimed to narrow the band gap of YD2-o-C8 to extend the light-harvesting region to near-infrared (NIR). This was done by incorporating Cd instead of Zn onto the porphyrin ring and elongating the length of π-conjugation by adding ethynylene link and anthracene unit, so that the performances of the suggested cells could be expected to exceed the 11.9%–12.7% efficiencies with TiO2, ZnO2, and WO3 oxide electrodes. The effects of modifying the central metal and elongating the length of π-conjugation on cell performance are confirmed in terms of frontier molecular orbital (FMO) energy gaps, density of states (DOS), molecular electrostatic potentials (MEPs), non-linear optical (NLO) properties, ultraviolet–visible (UV–vis) electronic absorption, and 1H nuclear magnetic resonance chemical shifts. Increasing the length of π-conjugation of the D–π–A dyes leads to increasing the DOS near Fermi levels, more active NLO performance, strong response to the external electric field, delocalisation of the negative charges near the anchoring groups, deep electron injection, suppressing macrocycle aggregation, active dye regeneration, and inhibited dye recombination. The calculated band gap/eV of the present DMP-Zn is correlated with the experimental (E1/2(oxidation)–E1/2(reduction)/V) potentials of the identical YD2-o-C8. A co-sensitiser is suggested for NIR sensitisation (550–950 nm) to increase the power-to-conversion efficiency beyond 14%. 相似文献
144.
In this study, the controller is used to suppress the vibration due to rotor the helicopter blade flapping motion. The objective of this paper is to investigate the effect of time-delay absorber on the vibrating system when subjected to multi-parametric excitation forces. The equations of motion are described by coupled nonlinear differential equations. The averaging method is applied to obtain the frequency response equations near simultaneous sub-harmonic and internal resonance. The stability of the obtained nonlinear solution is studied and solved numerically. Numerical simulations show the steady state response amplitude versus the detuning parameter and the effects of the parameters system and controller. Effectiveness of the absorber E a is about 2.7×105 of the main system (X). 相似文献
145.
Teleb SM 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(13):3093-3100
Four complexes are obtained during the reactions of 6-amino-1-methyl-5-nitrosouracil and its 6-methylamine derivative with Co(II) and Cu(II) ions. Theses complexes were characterized through their elemental, thermal analysis, infrared and 1H NMR spectroscopes. The obtained results indicate that, the exocyclic oxygen and nitrogen atoms are the most probable binding sites rather than ring nitrogen atoms. For cobalt complexes, the two pyrimidine bases act as bidentate ligands in the anionic form with the dissociation of iminic or N3 proton depending upon the nature of substituents on the pyrimidine ring. For copper complexes, the pyrimidine bases interact in the neutral form as monodentate ligands. Octahedral geometries are proposed for all of these complexes. 相似文献
146.
In our consideration, a comparison between four different types of controllers for suppression the vibrations of the cantilever beam excited by an external force is carried out. Those four types are the linear velocity feedback control, the cubic velocity feedback control, the non-linear saturation controller (NSC) and the positive position feedback (PPF) controller. The suitable type is the PPF controller for suppression the vibrations of the cantilever beam. The approximate solution obtained up to the first approximation by using the multiple scale method. The PPF controller effectiveness is studied on the system. We used frequency-response equations to investigate the stability of a cantilever beam. We notified that, there is a good agreement between the analytical solution and the numerical solution. 相似文献
147.
We study the symmetry breaking of acoustic resonances measured by Ellegaard et al. (1996) [1] in quartz blocks. The observed resonance spectra show a gradual transition from a superposition of two uncoupled components, one for each symmetry realization, to a single component that is well represented by a Gaussian orthogonal ensemble (GOE) of random matrices. We discuss the applicability of superstatistical random-matrix theory to the final stages of the symmetry-breaking transition. A comparison is made between the formula from superstatistics and that from a previous work by Abd El-Hady et al. (2002) [7], which describes the same data by introducing a third GOE component. Our results suggest that the inverse chi-squared superstatistics could be used for studying the whole symmetry-breaking process. 相似文献
148.
H.M. Zaki 《Physica B: Condensed Matter》2012,407(12):2025-2031
Cu2+ ions substituted Ni-ferrite having the general formula Ni1-xCuxFe2O4 (where x=0.0, 0.2, 0.4 and 0.6) were prepared by the sintering ceramic method. X-ray diffraction, infrared spectra and magnetization of the above ferrite were carried out to investigate structural and magnetic characterization of this ferrite. Crystallite size, lattice parameters, positional oxygen parameter and ionic radii for both tetrahedral and octahedral sites were calculated. The experimental lattice parameter was found to vary between 8.3856 and 8.3865 Å. The infrared spectra were measured in the frequency range 650–150 cm−1. Two prominent bands were observed, high frequency band ν1 and low frequency band ν2 were assigned to tetrahedral and octahedral sites. Bond length and force constant were also calculated for both tetrahedral and octahedral sites. The effect of Cu concentration on, saturation magnetization, coercivity ratio and magnetic moment were investigated using vibrating sample magnetometer (VSM). It was found that both saturation magnetization (MS) and coercivity (Hc) decreases with increasing in Cu content. 相似文献
149.
An integrated model for optimum weight design of symmetrically laminated composite plates subjected to dynamic excitation is presented in this work. Optimum design procedure based on flexibility and strength criteria is presented. The objective is to determine the optimum thicknesses of the laminate layers and its optimum orientations without exhibiting any failure according to Tsai-Wu failure criterion. The finite element method, based on Mindlin plate theory, is used in conjunction with an optimization method in order to determine the optimum design. Newmark algorithm, as an implicit time integration scheme, is used to discretize the time domain and calculate the transient response of the laminated composite plate. Exterior penalty method is exploited for the constrained minimization procedure. Fletcher-Powell algorithm is used for the unconstrained minimization process. To verify the capability and efficiency of the proposed model, three examples are solved. The examples deal with flexibility and stress constraints for different boundary conditions under various dynamic excitations. 相似文献
150.
A rotor-active magnetic bearing (AMB) system subjected to a periodically time-varying stiffness with quadratic and cubic nonlinearities
under multi-parametric excitations is studied and solved. The method of multiple scales is applied to analyze the response
of two modes of a rotor-AMB system with multi-parametric excitations and time-varying stiffness near the simultaneous primary
and internal resonance. The stability of the steady state solution for that resonance is determined and studied using Runge-Kutta
method of fourth order. It is shown that the system exhibits many typical non-linear behaviors including multiple-valued solutions,
jump phenomenon, hardening and softening non-linearities and chaos in the second mode of the system. The effects of the different
parameters on the steady state solutions are investigated and discussed also. A comparison to published work is reported. 相似文献