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991.
The effects of Knudsen-dependent flow velocity on vibrations of a nano-pipe conveying fluid 总被引:1,自引:0,他引:1
Mehran Mirramezani Hamid Reza Mirdamadi 《Archive of Applied Mechanics (Ingenieur Archiv)》2012,82(7):879-890
In this paper, we investigate the effect of nano-flow on vibration of nano-pipe conveying fluid using Knudsen (Kn). We use Euler–Bernoulli plug-flow beam theory. We modify no-slip condition of nano-pipe conveying fluid based on Kn. We define a Kn-dependent flow velocity. We consider effect of slip condition, for a liquid and a gas flow. We reformulate Navier–Stokes equations, with modified versions of Kn-dependent flow velocity. We observe that for passage of gas through nano-pipe with nonzero Kn, the critical flow velocities decreased considerably as opposed to those for zero Kn. This can show that ignoring Kn effect on a gas nano-flow may cause non-conservative design of nano-devices. Furthermore, a more impressive phenomenon happens in the case of clamped-pinned pipe conveying gas fluid. While we do not observe any coupled-mode flutter for a zero Kn, we can see the coupled-mode flutter, accompanying the second-mode divergence, for a nonzero Kn. 相似文献
992.
SONG Yang WANG Jin-cheng XU Hui DU Zhen-wu ZHANG Gui-zhen SELIM Hamid Abdu LI Guang-sheng WANG Qing GAO Zhong-li 《高等学校化学研究》2013,29(2):263-269
As the strongest electronegative element, fluorine can stimulate the production of superoxide radicals in cells. In view of the important roles of kidneys in bone metabolism, the authors analyzed the quantitative pathomorphological characteristics of renal damage and the potential cellular apoptosis and oxidative stress mechanisms in rats treated with excessive fluoride. Wistar rats were exposed to 50 mg F-(110.5 mg NaF)/L, 100 mg F-(221.0 mg NaF)/L and 150 mg F-(331.5 mg NaF)/L in drinking water for 70 and 140 d, respectively. Microscope with image analysis was used to quantitate pathomorphological changes in renal tissues of the rats. Reactive oxygen species(ROS), the cell cycle and apoptosis of renal cells were measured by flow cytometry and TUNEL technique(terminal deoxynucleotidyl transferase dUTP nick end labeling), respectively. The ion concentrations in serum and renal functional parameters were detected by automatic biochemical analyzer. Quantitative analysis results demonstrate the expanded Bowman’s space of glomerulus and obvious dilatation of renal tubule. TUNEL technique revealed that NBT/BCIP (nitro blue tetrazolium/5-bromo-4-chloro-3′-indolylphosphate, p-toluidine salt)-staining positive apoptotic cells selectively located in medullocortical junction areas. The data suggest that renal damage in chronic fluorostic rats is associated with the cellular apoptosis and oxidative stress. 相似文献
993.
Hamid Torabi Mahmoud Shariati Elahehsadat Sedaghat Ali Lashkari Zadeh 《Meccanica》2013,48(8):1959-1974
The buckling behavior of perfect and defective double-walled carbon nanotubes (DWCNTs) under axial compressive, torsional and bending loadings is investigated using a structural mechanics model. The effects of van der Waals (vdW) forces are further modeled using a nonlinear spring element. Critical buckling loads, critical buckling moments and the effects of vacancy defects were studied for armchair nanotubes with various aspect ratios. The results show that vacancy defects greatly reduce the critical buckling load of DWCNTs. The density of defects plays an important role in buckling of DWCNTs. The results of this numerical model are in good agreement with their comparable existing works. 相似文献
994.
Silica‐supported polyphosphoric acid (PPA‐SiO2) catalyzed efficiently the reaction of anthranilamide with aryl aldehydes or ketones under solvent‐free conditions to afford the corresponding 1,2,3,4‐tetrahydro‐4‐quinazolinone derivatives. This work consistently has the advantages of excellent yields, short reaction time, simple experimental and work‐up procedures. The heterogeneous catalyst could be recovered and recycled for several times without any loss of its activity. 相似文献
995.
996.
997.
Arash Ghorbani-Choghamarani Maryam Hajjami Hamid Goudarziafshar Mohsen Nikoorazm Shadpour Mallakpour Fatemeh Sadeghizadeh Gouhar Azadi 《Monatshefte für Chemie / Chemical Monthly》2009,140(6):607-610
Abstract A simple and efficient catalytic oxidation of urazoles and a bis-urazole to the corresponding triazolinediones by treatment
with Al(NO3)3.9H2O in the presence of a catalytic amount of silica sulfuric acid is described. A good range of urazole derivatives was selectively
oxidized in CH2Cl2 at room temperature in good to excellent yields.
Graphical abstract
相似文献
998.
Javed MR Rashid MH Nadeem H Riaz M Perveen R 《Applied biochemistry and biotechnology》2009,157(3):483-497
Monomeric extracellular endoglucanase (25 kDa) of transgenic koji (Aspergillus oryzae cmc-1) produced under submerged growth condition (7.5 U mg−1 protein) was purified to homogeneity level by ammonium sulfate precipitation and various column chromatography on fast protein
liquid chromatography system. Activation energy for carboxymethylcellulose (CMC) hydrolysis was 3.32 kJ mol−1 at optimum temperature (55 °C), and its temperature quotient (Q
10) was 1.0. The enzyme was stable over a pH range of 4.1–5.3 and gave maximum activity at pH 4.4. V
max for CMC hydrolysis was 854 U mg−1 protein and K
m was 20 mg CMC ml−1. The turnover (k
cat) was 356 s−1. The pK
a1 and pK
a2 of ionisable groups of active site controlling V
max were 3.9 and 6.25, respectively. Thermodynamic parameters for CMC hydrolysis were as follows: ΔH* = 0.59 kJ mol−1, ΔG* = 64.57 kJ mol−1 and ΔS* = −195.05 J mol−1 K−1, respectively. Activation energy for irreversible inactivation ‘E
a(d)’ of the endoglucanase was 378 kJ mol−1, whereas enthalpy (ΔH*), Gibbs free energy (ΔG*) and entropy (ΔS*) of activation at 44 °C were 375.36 kJ mol−1, 111.36 kJ mol−1 and 833.06 J mol−1 K−1, respectively. 相似文献
999.
Hassan Keypour Majid Rezaeivala Laura Valencia Sadegh Salehzadeh Paulo Perez-Lourido Hamid Reza Khavasi 《Polyhedron》2009,28(16):3533-3541
The metal templated Cd(II) cyclocondensation of 2,6-diacetylpiridine or 2,6-pyridinedicarbaldehyde and two different amines containing piperazine moieties have been investigated. The resulting ligands, L1 and L2 are 16- and L3 and L4 17-membered pentaaza macrocycles. The complexes have been characterized by a variety of methods including IR, 1H, 13C NMR, DEPT, COSY(H,H), HMQC(H,C), FAB spectrometry and conductivimetry measurements. The crystal structures of [CdL2Cl](CH3OH)ClO4 (2) and [CdL4(NO3)(H2O)]ClO4 (4) have been also determined, and it was shown that the geometry of the Cd(II) ion in the complexes is slightly distorted pentagonal pyramidal and pentagonal bipyramidal, respectively. The gas-phase structures of ligands, L2 and L4 and their Cd(II) complexes have also theoretically studied. 相似文献
1000.
Hamid Pesaran Behbahani Azlan bin Adnan Mohammadreza Vafaei Ong Peng Pheng Hossein Shad 《Meccanica》2017,52(6):1247-1256
Tuned liquid column damper (TLCD) is a class of auxiliary damping device which is used to dissipate vibrational energy of structures when excited by dynamic loading. Damping control of TLCDs is an important parameter to achieve the maximum benefit of TLCDs when attached to the structure. Herein, a new method of controlling damping is proposed by installing maneuverable flaps into TLCD (TLCD + MF). The damping value of the TLCD is controlled by the closing angle of the flaps. This method is simple in concept, more applicable in construction, and it is an effort to make the TLCD more controllable, (i.e. semi-active). Dynamic characteristics of such TLCD + MF system are investigated in this study. It is observed that by increasing the closing angle, the damping ratio of the TLCD + MF system increases. In addition, it is found that the mistuning of frequency becomes ignorable below the closing angle of 50°. The efficiency of the TLCD + MF in reducing response of structures under harmonic excitation is also studied. It is shown that existence of the flaps improves the performance of combined structure and the TLCD + MF system in terms of damping ratio and structural responses. The TLCD + MF system with the closing angle of 50° reduces the acceleration and displacement responses about 20 % more than conventional TLCDs. 相似文献