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排序方式: 共有129条查询结果,搜索用时 46 毫秒
81.
Leila Hatami Vahid Haddadi‐Asl Leila Ahmadian‐Alam Hossein Roghani‐Mamaqani Mehdi Salami‐Kalajahi 《国际化学动力学杂志》2013,45(4):221-235
Poly(styrene‐co‐butyl acrylate)/clay nanocomposites were synthesized in miniemulsion via activators generated by electron transfer (AGET) for atom transfer radical polymerization (ATRP). Optimum amounts of catalyst and reducing agent were chosen by considering a linear increase in ln([M0]/[M]) versus time, narrow molecular distribution, and low polydispersity index (PDI). Critical micelle concentration and cross‐sectional surface area per surfactant head group were determined by surface tension analysis. Calculations show that droplet nucleation is the dominant mechanism of nucleation in a miniemulsion system, and there is no micelle in the system. Gel permeation chromatography was used to characterize molecular weight, PDI, and molecular weight distribution. After determination of appropriate conditions, poly(styrene‐co‐butyl acrylate)/clay nanocomposite latexes were synthesized. Low PDI, narrow molecular weights, and first‐order kinetics of the nanocomposites justify that polymerization is well controlled. Kinetics of polymerization decreases by clay loading. The apparent propagation rate constant (kapp) of polymerization in the case of poly(styrene‐co‐butyl acrylate) is 4.079 × 10?6, which becomes 0.558 × 10?6 in the case of poly(styrene‐co‐butyl acrylate)/clay nanocomposite with 2% nanoclay. A decrease in the polymerization rate is related to the hindrance effect of nanoclay layers on monomer diffusion toward the loci of growing macroradicals. 相似文献
82.
Friction in contact interfaces of assembled structures is the prime source of nonlinearity and energy dissipation. Determination of the dissipated energy in an assembled structure requires accurate modeling of joint interfaces in stick, micro-slip and macro-slip states. The present paper proposes an analytical model to evaluate frictional energy loss in surface-to-surface contacts. The goal is to develop a continuous contact model capable of predicting the dynamics of friction interface and dissipation energy due to partial slips. To achieve this goal, the governing equations of a frictional contact interface are derived for two distinct contact states of stick and partial slip. A solution procedure to determine stick–slip transition under single-harmonic excitations is derived. The analytical model is verified using experimental vibration test responses performed on a free-frictionally supported beam under lateral loading. The theoretical and experimental responses are compared and the results show good agreements between the two sets of responses. 相似文献
83.
Cobalt manganese oxide nanoparticles as recyclable catalyst for efficient synthesis of 2‐aryl‐1‐arylmethyl‐1H‐1,3‐benzimidazoles under solvent‐free conditions 下载免费PDF全文
Hossein Ahmadian Hojat Veisi Changiz Karami Alireza Sedrpoushan Maryam Nouri Fariba Jamshidi Iman Alavioon 《应用有机金属化学》2015,29(5):266-269
Cobalt manganese oxide nanocatalyst was synthesized and it was found that it is a highly efficient green catalyst for the synthesis of 2‐aryl‐1‐arylmethyl‐1H‐1,3‐benzimidazoles under solvent‐free conditions. The marked advantages of this method are the simple experimental procedures, shorter reaction times, high yields of product, reusable and non‐toxic catalyst and solvent‐free conditions. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
84.
85.
Issa Yavari Majid Ghazanfarpour‐Darjani Yazdan Solgi Salomeh Ahmadian 《Helvetica chimica acta》2011,94(4):639-642
An efficient synthesis of functionalized 2‐(1,3‐oxathiolan‐2‐ylidene)malononitriles containing a push‐pull C?C bond via a simple reaction between malononitrile, CS2, and oxiranes in the presence of Et3N is described (Scheme 1). 相似文献
86.
Elidrisi I Negin S Bhatt PV Govender T Kruger HG Gokel GW Maguire GE 《Organic & biomolecular chemistry》2011,9(12):4498-4506
Five new cavitands were prepared that have four pendant n-undecyl chains and "headgroups" connected by 2-carbon spacers. The headgroups were ~OCH(2)CONH-Ala-OCH(3), 1; ~OCH(2)CONH-Phe-OCH(3), 2; ~OCH(2)CONH-Ala-OH, 3; ~OCH(2)CONH-Phe-OH, 4; and ~OCH(2)CONHCH(2)CH(2)-thyminyl, 5. Pore formation by each cavitand was studied by use of the planar bilayer conductance experiment. All five compounds were found to form pores in asolectin bialyer membranes. Compounds 1-3 behaved in a generally similar fashion and exhibited open-close dynamics. Compounds 4 and 5 formed pores more rapidly, were more dynamic, and led more quickly to membrane rupture. Differences in the ion transport activity are rationalized in terms of structure and aggregate cavitand assemblies. 相似文献
87.
In this paper describing functions inversion is used and the restoring force of a nonlinear element in a MDOF system is characterized.
The describing functions can be obtained using linearized frequency response functions (FRFs). The response of the system
to harmonic excitation forces at distinct frequencies close to the resonant frequency results in linearized FRFs. The nonlinear
system can be approximated at each excitation frequency by an equivalent linear system. This approximation leads to calculation
of the first-order describing functions. By having the experimental describing functions calculated and the system’s responses
corresponding to the nonlinear element (measured or interpolated), nonlinear parameter identification can be performed. Two
numerical and experimental case studies are provided to show the applicability of this method. 相似文献
88.
Chu Yu-Ming Ikram Muhammad Danish Asjad Muhammad Imran Ahmadian Ali Ghaemi Ferial 《Journal of Thermal Analysis and Calorimetry》2021,144(6):2057-2077
Journal of Thermal Analysis and Calorimetry - In this paper, it has been discussed a nonlocal fractional model of viscous nanofluid holding a hybrid nanostructure. Hybridized copper (Cu) and... 相似文献
89.
R. Mahinpour G. H. Riazi M. N. Sarbolouki A. A. Moosavi-Movahedi S. Ahmadian M. A. Shokrgozar S. Z. Moosavi-Nejad 《Journal of the Iranian Chemical Society》2009,6(4):715-721
Prevention of microtubule polymerization is considered as one of the promising approaches towards inhibition of cell proliferation, especially in treatment of malignancies. Arsenic trioxide, As2O3, is being successfully used in the treatment of human lymphoma, while the mechanism of its therapeutic function is still under investigation. Experiments were designed to determine if indeed As2O3 interferes with polymerization of nanotube microtubule. Microtubules were extracted from sheep brain and their interaction with arsenic trioxide was examined by spectrometery. Electrical conductometry of 2 mM MgSO4 solution containing various concentrations of As2O3 was studied in order to determine their possible interaction. Transmission electron microscopy was used to show microtubule structure in the presence of arsenic trioxide. Fluorometric characteristics of tubulin dimer were examined in presence of varying concentrations of arsenic trioxide. It is concluded that arsenic trioxide interacts with Mg2+ ion around GTPase site of β-tubulin, resulting enhancement of depolymerization of the microtubule polymer. 相似文献
90.
Mehdi Ahmadian 《International Journal of Non》1986,21(6):483-488
A technique is presented for determaining the stability of lumped-pararaeter, time-varying, dynamic systems with aperiodic coefficients. An “energy like” function is used to develop stability conditions which are direct in terms of the coefficient matrices. The significance of what is presented here is twofold. First, it gives stability conditions applicable to systems which are not necessarily periodic. Second, is allows for a systematic categorization of the effects of the parameter changes on system response and stability, in order to provide a better understanding of the behavior of this class of dynamic systems as they arise in various areas of engineering. 相似文献