This paper deals with the stability analysis of internally damped rotating composite shafts. An Euler–Bernoulli shaft finite element formulation based on Equivalent Single Layer Theory (ESLT), including the hysteretic internal damping of composite material and transverse shear effects, is introduced and then used to evaluate the influence of various parameters: stacking sequences, fiber orientations and bearing properties on natural frequencies, critical speeds, and instability thresholds. The obtained results are compared with those available in the literature using different theories. The agreement in the obtained results show that the developed Euler–Bernoulli finite element based on ESLT including hysteretic internal damping and shear transverse effects can be effectively used for the stability analysis of internally damped rotating composite shafts. Furthermore, the results revealed that rotor stability is sensitive to the laminate parameters and to the properties of the bearings. 相似文献
In this paper, we present the methodology and the results obtained by the gravimetric and the FTIR methods to study the sorption of amyl acetate in polypropylene packaging. The influence of the concentration of amyl acetate and the temperature of aging on the sorption is discussed. A non-Fickian model is used to determine the diffusion coefficient and the surface mass transfer coefficient and their evolution with the amyl acetate concentration and the temperature of aging. The effect of the diffusion of amyl acetate on the polypropylene is studied by means of thermal properties. 相似文献
We report the optical properties of a fluorochlorozirconate (FCZ) glass with the composition 53% ZrF4, 20% NaF, 3.5% AlF3, 3% LaF3, 0.5% InF3, (20 ? x)% BaCl2, x% BaF2 with x varying from 0% to 2%, and doped with various amounts of trivalent erbium by the addition of ErCl3. Annealing of the as-prepared glass in inert (N2) or reducing (5%H2 + 95%Ar) atmospheres at temperatures that ensure the conversion of the glass into a glass-ceramic by the nucleation of BaCl2 nanocrystals, does not significantly change any of Er3+ related absorption and photoluminescence (PL) characteristics. We have carried out a Judd–Ofelt analysis of the absorption spectra and obtained Ω2 = (1.92 ± 0.3) × 10? 20 cm2, Ω4 = (0.88 ± 0.16) × 10? 20 cm2 and Ω6 = (0.59 ± 0.08) × 10? 20 cm2, and also the radiative lifetimes of the 4I13/2→4I15/2, 4I11/2→4I15/2 and 4S3/2→4I15/2 bands. The radiative lifetime from the Judd–Ofelt analysis for the 4I13/2→4I15/2 band is in good agreement with the experimentally measured PL decay time. The examination of the optical properties of powdered samples with different average particle size does not show any photon trapping effects. We have determined the spectral absorption and emission cross-sections and then estimated the possible spectral optical gain for varying degrees of relative populations of the 4I13/2 and 4I15/2 manifolds. 相似文献
A system of partial differential equations describing the thermal behavior of aluminium cell coupled with magnetohydrodynamic effects is numerically solved. The thermal model is considered as a two-phases Stefan problem which consists of a non-linear convection–diffusion heat equation with Joule effect as a source. The magnetohydrodynamic fields are governed by Navier–Stokes and by static Maxwell equations. A pseudo-evolutionary scheme (Chernoff) is used to obtain the stationary solution giving the temperature and the frozen layer profile for the simulation of the ledges in the cell. A numerical approximation using a finite element method is formulated to obtain the fluid velocity, electrical potential, magnetic induction and temperature. An iterative algorithm and 3-D numerical results are presented. 相似文献
Journal of Thermal Analysis and Calorimetry - In the present study, double-diffusive mixed convection related to the heat and mass transfer of the solid particles dissolution in a shear flow was... 相似文献
Methylglycine, also known sarcosine, is dramatically used in drug molecules and its metal complexes can interact to DNA and also do cleavage. Hence, to study the influence of methylglycine ligand on biological behavior of metal complexes, two water-soluble platinum (II) complexes with the formula cis-[Pt(NH3)2(CH3-gly)]NO3 and cis-[Pt(NH2-CH3)2(CH3-gly)]NO3 (where CH3-gly is methylglycine) have been synthesized and characterized by spectroscopic methods, molar conductivity measurements, and elemental analyzes. The anticancer activity of synthesized complexes was tested against human breast adenocarcinoma cell line of MCF7 using MTT assay and results showed excellent anticancer activity with Cc50 values of 126 and 292 μM after 24 h incubation time, for both complexes of cis-[Pt(NH3)2(CH3gly)]NO3 and cis-[Pt(NH2-CH3)2(CH3gly)]NO3, respectively. Also, the interaction between Pt(II) complexes with calf thymus DNA was extensively studied by means of absorption spectroscopy, fluorescence titration spectra displacement with ethidium bromide (EtBr), and circular dichroism studied in Tris-buffer. The obtained spectroscopic results revealed that two complexes can bind to highly polymerized calf thymus DNA cooperatively and denature at micromolar concentrations. The fluorescence data indicate that quenching effect for cis-[Pt(NH3)2(CH3gly)]NO3 (Ksv?=?9.48 mM?1) was higher than that of cis-[Pt(NH2-CH3)2(CH3gly)]NO3 (Ksv?= 1.98 mM?1). These results were also confirmed by circular dichrosim spectra. Consequently, docking data showed that cis-[Pt(NH3)2(CH3gly)]NO3 with more interaction energy binds on DNA via groove binding which is more compatible with experimental results.
Graphical Abstract ? Two anticancer Pt(II) complexes, cis-[Pt(NH3)2(CH3gly)]NO3 and cis-[Pt(NH2?CH3)2(CH3gly)]NO3, have been synthesized and interacted with calf thymus DNA. Improving solubility of these compounds reduce side effects and increase anticancer activity against human breast cell line. Modes of binding have been studied by electronic absorption, fluorescence, and CD measurements. Results show that both Pt(II) complexes can interact to DNA via groove binding.
Solid Phase Micro Extraction (SPME) involves exposing a fused silica fiber coated with stationary phase to a contaminated water sample. The organic analytes become partitioned between the stationary phase and the water and when equilibrium is reached the fiber is removed from the solution and the analytes are thermally desorbed in the injector of a gas chromatograph. The fiber is contained in a syringe to facilitate handling. Factors which affect linear range, limit of detection, and total analysis time are discussed with regard to the development of a method for analysis of volatile compounds in environmental water samples. The sensitivity of the method was determined by the thickness of the film of stationary phase; the equilibration time, however, increased with the film thickness, although it can be minimized by use of a cross-shaped stirrer bar. Increasing the thickness of stationary phase in the analytical column enables the cryofocusing temperature to be increased from ?40 to ?15°C. With an ion trap mass spectrometer, detection limits required by the US Environmental Protection Agency are met for all compounds except chloromethane and chloroethane. The method has been applied to environmental water samples. 相似文献
In this work, using density functional theory, the kinetic effects of the substitution of a t‐butyl group and\or the incorporation of an oxygen atom, and both, at the aziridine ring moiety were investigated for N‐inversion in N‐phenylaziridine. Then, for N‐inversion in 3‐t‐butyl‐N‐phenyloxaziridine, the kinetic Hammett substituent effects were studied using the different para‐substituted groups on the N‐phenyl ring moiety. The natural bond orbital (NBO) study was the last case in this work. The calculations were performed in the gas phase and solution (in carbon tetrachloride and dichloromethane). The incorporation of an oxygen atom in the aziridine ring strongly weakens the N‐inversion process. In addition, while both t‐butyl substituent and solvent slightly reinforce the N‐inversion of N‐phenyloxaziridine, in N‐phenylaziridine, they decrease the N‐inversion rate to some extent. In both phases, more pronounced in solution and especially in dichloromethane, and in agreement with the NBO results, the electron‐withdrawing groups on para position of the N‐phenyl ring strongly increase the rate of N‐inversion of 3‐t‐butyl‐N‐phenyloxaziridine molecule. 相似文献