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221.
According to the linear theory of vibration for spinning disks, the backward traveling waves of some of the modes may have zero natural frequency at what are called the critical speeds. At these speeds, the linear equations of motion cannot properly predict the amplitude response of the spinning disk, and nonlinear equations of motion must be used. In this paper, geometrical nonlinear equations of motion based on Von Karman plate theory are employed to study the dynamics of an elastically constrained disk near its critical speeds. A one-mode approximation is used to examine the effect of elastic constraint on the amplitude response. Presenting the equations in a space-fixed coordinate system, this study aims to find closed-form solutions for some of the equilibrium configurations of an elastically constrained spinning disk. Also, the stability of these configurations is studied using analytical techniques. It is shown that below the critical speed, one neutrally stable equilibrium solution exists, while above it, a bifurcation occurs. In this situation, two more branches of equilibrium configurations emerge, one of which is neutrally stable and the other unstable. Closed-form expressions for the bifurcation points are obtained. Due to the effect of an elastic constraint, a bifurcation occurs and the previously neutrally stable equilibrium configuration turns unstable. Also at this bifurcation point, two more branches of equilibrium solutions emerge. 相似文献
222.
In this paper, we investigate the roles of gold catalysts and thermal evaporation method modifications in the growth process of Zn1−xMgxO nanowires. Zn1−xMgxO nanowires are fabricated on silicon substrates with and without using a gold catalyst. Characterizations reveal that Mg acts in a self-catalyst role during the growth process of Zn1−xMgxO nanowires grown on catalyst-free substrate. The optical properties and crystalline quality of the Zn1−xMgxO nanowires are characterized by room temperature photoluminescence (PL) measurements and Raman spectroscopy, respectively. The Raman and PL studies demonstrate that the Zn1−xMgxO nanowires grown using the catalyst-free method have good crystallinity with excellent optical properties and have a larger band-gap in comparison to those grown with the assistance of gold. 相似文献
223.
Ramin Yousefi Farid Jamali Sheini Muhamad Rasat Muhamad Mahendra A. More 《Solid State Sciences》2010,12(7):1088-1093
In this paper, we investigate the roles of gold catalyst using modified thermal evaporation set-up in the growth process of ZnMgO nanowires. ZnMgO nanowires are fabricated on silicon substrates using different thickness of gold catalyst. A simple horizontal double-tube system along with chemical vapor diffusion of the precursors, based on Fick’s first law, is used to grow the ZnMgO nanowires. Field emission scanning electron microscopy images show that the ZnMgO nanowires are tapered. The optical properties of the ZnMgO nanowires are characterized by room temperature photoluminescence (PL) measurements. The PL studies demonstrate that the ZnMgO nanowires grown using this method have good crystallinity with excellent optical properties and have a larger band-gap in comparison to the pure ZnO nanowires. Field emission characterization shows that the turn-on field for the nanowires grown on the thinner gold film is lower than those grown on the thicker gold film. 相似文献
224.
A simple and efficient synthesis of 2‐amino‐4‐aryl thiazole derivatives was carried out through the reaction of substituted acetophenones and thiourea using three different types of catalytic systems including N,N,N′,N′‐tetrabromobenzene‐1,3‐disulfonamide [TBBDA], poly(N,N′‐dibromo‐N‐ethylbenzene‐1,3‐disulfonamide) [PBBS] and a combination of TBBDA and nano‐magnetic catalyst supported with functionalized 4‐amino‐pyridine silica (MNPs@SiO2‐Pr‐AP). The results showed that the use of TBBDA along with the MNPs@SiO2‐Pr‐AP gains the highest yields of the products in the shortest reaction time. 相似文献
225.
226.
In vitro curcumin delivery and antibacterial activity of RuS2 and RuO2 nanoparticles loaded chitosan biopolymer
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Shadi Kheirandish Mehrorang Ghaedi Kheibar Dashtian Faezeh Pourebrahim Ramin Jannesar Vahid Pezeshkpour 《应用有机金属化学》2018,32(2)
In this work, RuS2 and RuO2 nanoparticles loaded chitosan (Chitosan was extracted from Lobsters shells of Persian Gulf, IR. Iran) was prepared and characterized via FE‐SEM, EDS and FT‐IR analysis. FESEM showed the formation of spherical nanoparticles in size ranging of 20 to 100 mm. Subsequently, the role of these new materials as curcumin drug carrier and in vitro release of curcumin in simulated body fluid (SBF) solution (pH 7.4) were studied. RuS2‐NPs‐CS than to RuO2‐NPs‐CS showed higher drug loading efficiency (>91%) and rapid (<90 min) curcumin drug release in SBF solution. Also, antibacterial activity of RuS2‐NPs‐CS and RuO2‐NPs‐CS in presens and absence of Rosemary extracts against the gram negative bacteria Pseudomonas aeruginosa (PAO 1) was evaluated by detection of minimal inhibition concentration (MIC) and minimal bactericidal concentration (MBC). MIC of RuS2‐NPs‐CS, RuO2‐NPs‐CS and Rosemary extracts on Pseudomonas aeruginosa strains were found to be 50 mg/ml, 50 mg/ml and 1250 mg/ml, respectively. The synergistic effect of these materials for inhibition of PAO 1 growth showed that mixture of RuS2‐NPs‐CS and Rosemary extracts has a better efficiency than to other mixture materials. 相似文献
227.
Ramin Ghorbani-Vaghei Yaser Maghbooli Azadeh Shahriari Jafar Mahmoodi 《Molecular diversity》2016,20(4):907-917
228.
Ghorbani-Vaghei Ramin Malaekehpoor Seyedeh Mina Hasanein Parisa Karamyan Roya Asadbegy Mostafa 《Research on Chemical Intermediates》2016,42(5):4715-4731
Research on Chemical Intermediates - N,N,N′,N′-Tetrachlorobenzene-1,3-disulfonamide and poly(N,N′-dichloro-N-ethyl-benzene-1,3-disulfonamide) are new catalysts promoted by... 相似文献
229.
Roshanak Rafiei Nazari Ardavan Koohi Ramin KhosraviFarshad Ebrahimi Mojtaba Yaghobi 《Physica B: Condensed Matter》2011,406(13):2626-2631
We have developed a method to study the theory of charge pumping through a continuous quantum wire using the invariant imbedding approach. Using this method, the general properties of quantum charge pumping, with and without inclusion of many-body interactions are investigated. Using the invariant imbedding approach allows us to address directly the complex reflection (R) and transmission (T) matrices across the wire instead of considering the spectrum of the Schrodinger equation. Using the Kohn-Sham version of density functional theory (DFT), the many-body interactions in the quantum wire is investigated. We calculated the pumped current in those two cases. In the case of ignoring the many-body effects, the pumped current depends on the width of the driven potential barriers and in the case of nonequality of the width of barriers, our study predicts a nonzero charge pumping at the phase difference φ=0 even when the driving potentials are equal. In the second case, although the pumped current had sinusoidal dependence on φ but its value significantly decreased and we also observed nonzero pumping at φ=0 even when the driving potentials and their widths are equal, which is consistent with the recent experimental result. 相似文献
230.
Khosrow Jadidi Ramin Ghahremanzadeh Peiman Mirzaei Ayoob Bazgir 《Journal of heterocyclic chemistry》2011,48(5):1014-1018
A one‐pot, three‐component method for the efficient and simple synthesis of novel 2′‐amino‐8′,9′‐dihydro‐3′H‐spiro[indoline‐3,5′‐pyrimido[4,5‐b]quinoline]‐2,4′,6′(7′H,10′H)‐trione derivatives in aqueous media is reported. J. Heterocyclic Chem., (2011). 相似文献