排序方式: 共有156条查询结果,搜索用时 187 毫秒
71.
Mir Masoud Seyyed Fakhrabadi Mostafa Samadzadeh Abbas Rastgoo Mohammadreza Haeri Yazdi Mahmoud Mousavi Mashhadi 《Physica E: Low-dimensional Systems and Nanostructures》2011,44(3):565-578
This paper presents the molecular mechanics based finite element modeling of carbon nanotubes (CNTs) and their applications as mass sensors. The beam element with elastic behavior is considered as the bond between the carbon atoms and its properties are obtained using equating continuum and molecular characteristics. The first five natural frequencies of CNTs in cantilever and doubly clamped boundary conditions (BCs) and their corresponding mode shapes are studied in detail. Furthermore, a multilayer perceptron neural network is used to predict the fundamental vibration frequencies of the CNTs with different diameters and lengths. In addition, variations of the natural frequencies of the CNTs with distorted cross sections are investigated. Moreover, the effects of some attached masses with various values on the first three natural frequencies of a considered CNT are studied here. 相似文献
72.
An efficient diastereoselective synthesis of 7-ethyl 5,6-dialkyl 7H-[1,3]thiazolo[2,3-b][1,3]oxazin-5,6, 7-tricarboxylates and 2-ethyl 3,4-dialkyl 2H-[1,3]oxazino [2,3-b][1,3]benzothiazole-2,3,4-tricarboxylates via reaction of thiazole and benzothiazole with dialkyl acetylenedicarboxylates
in the presence of ethyl pyruvate is described. 相似文献
73.
Prof. Dr. Seyed A. Hosseini‐Yazdi Ali A. Khandar Mir Kh. Tabatabai Leila Noohinejad 《无机化学与普通化学杂志》2010,636(15):2650-2657
Dizinc(II) complexes of two acyclic Schiff‐base ligands L1 – and L2 – were synthesized by Schiff base condensation of 2‐[3‐(2‐formylphenoxy)‐2‐hydroxypropoxy]benzaldehyde ( PL ) with 1,2‐diaminopropane and 1,2‐diaminoethane, respectively, in the presence of zinc(II) salts. The isolation of a selection of 2:1 (metal:ligand) complexes of zinc(II) was carried out and conductance measurements, IR, UV/Vis absorption, and fluorescence emission spectroscopy, as well as X‐ray diffraction were employed to probe the nature of the respective complexes in both solid and solution states. The molecular structure of [Zn2 L1 (NO3)3] ( 1 ) complex consists of two six‐coordinate atoms, which are bridged by the deprotonated hydroxy group and one 1,3‐bridging nitrate anion. The structure of [Zn2 L2 (NO3)(H2O)2](NO3)2 · CH3OH ( 3 ) consists of a dizinc cation and two nitrate anions as counterions. In compound 3 , each zinc atom is bound to water instead of a terminal nitrate anion in a distorted octahedral arrangement. The intermetallic separation distance of Zn ··· Zn in 3 (3.376 Å) is slightly smaller than 1 (3.403 Å) and is similar to that found in zinc phosphotriesterase (3.5 Å). The π–π interactions between the benzene rings of adjacent molecules in 3 are stronger than in 1 . 相似文献
74.
Russian Journal of Electrochemistry - —Electrospinning and spin-coating techniques were used for the fabrication of polyacrylonitrile/polyaniline/WO3 (PAN/PANI/WO3) nanocomposite nanofibers... 相似文献
75.
Structural Chemistry - Although fullerene C60 is a strong scavenger for alkyl radicals, it is insusceptible toward peroxyl radicals. Substitution of carbon atoms in the fullerene cage by... 相似文献
76.
Sr(Zr0.84Y0.16)0.91O3 ? δ (SZY) and Ba(Zr0.84Y0.16)0.96O3 ? δ (BZY) protonic conductor coatings were co-sputter deposited from metallic targets in argon–oxygen reactive gas mixtures. The chemical and structural features were investigated by energy dispersive X-ray spectroscopy and X-ray diffraction, and their morphology was assessed by scanning electron microscopy of the surface and of brittle fracture cross sections. The electrical properties of the coating were determined by complex impedance spectroscopy as a function of temperature in air. Relationships are established between the electrical properties and the morphology of the coatings. The SZY as deposited coatings is amorphous and crystallises under the convenient perovskite structure after annealing treatment at 873 K under air. The BZY as deposited coatings is crystallised at 523 K in situ under perovskite structure and a further annealing treatment increases the grain size. Conductivities and activation energies of crystallised coatings were 3.1 · 10? 5 S cm? 1/2 · 10? 5 S cm? 1 and 0.65 eV/0.71 eV after stabilization at 773 K for strontium and barium zirconate, respectively. 相似文献
77.
SrZr1−x
Y
x
O3 coatings were co-sputtered from metallic Zr–Y (84–16 at.%) and Sr targets in the presence of a reactive argon–oxygen gas
mixture. The structural and chemical features of the film have been assessed by X-ray diffraction and scanning electron microscopy.
The electrical properties have been investigated for different substrates by Complex Impedance Spectroscopy as a function
of crystalline state, temperature and atmosphere. The as-deposited coatings are amorphous and crystallise after annealing
at 673 K for 2 h under air. The stabilisation of the perovskite structure is a function of the nominal composition. The films
are dense and present a good adhesion on different substrates. Crystallisation and mechanical stresses are detected by alternating
current (AC) impedance spectroscopy. Significant ionic conductivity in the 473–823 K temperature range is evidenced in air.
Two different conduction regimes in the presence of steam are attributed to a modification of the charge carrier nature. In
spite of low conductivity values (σ ~10−6 S.cm−1 at 881 K), the activation energies are in agreement with that of Y-doped strontium zirconate ceramics (~0.7 eV in air). 相似文献
78.
Dr. Joseph Benford-Ward Dr. Sanaz Ahmadipour Dr. Aliya Sembayeva Dr. Louise Male Dr. Richard S. Grainger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(71):e202202429
The dolabellane-type diterpene dictyoxetane represents a significant challenge to synthetic organic chemistry. Methodology directed towards the total synthesis of naturally occurring (+)-dictyoxetane is reported. Catalytic asymmetric synthesis of the trans-hydrindane ring system is achieved through chemoselective deoxygenation of the Hajos-Parrish ketone. An alternative to the Garst-Spencer furan annulation is developed for the synthesis of a 2,5-dimethyl, tetrasubstituted furan, employing a tandem 5-exo-dig alcohol to alkyne cyclisation/aromatisation reaction as a key step. The (4+3) cycloaddition reaction of an oxyallyl cation with a tetrasubstituted furan is established on a cyclohexanone-derived model system, and a range of related (4+3) cycloadditions investigated on a homochiral, trans-hydrindane-fused furan, where regio- and diastereoselectivity is required for the natural product synthesis. In an alternative (4+2) Diels-Alder approach, a C2-symmetric vinyl sulfoxide-based chiral ketene equivalent is used to prepare oxanorbornenes with the same oxygen bridge stereochemistry found in the 2,7-dioxatricyclo[4.2.1.03,8]nonane ring system of the natural product. 相似文献
79.
Maryam Yazdi & Saeed Hashemi Sababe 《计算数学(英文版)》2023,41(1):153-172
In this paper, we introduce a new iterative method based on the hybrid viscosity approximation method for finding a common element of the set of solutions of a general system of variational inequalities, an equilibrium problem, and the set of common fixed points of a countable family of nonexpansive mappings in a Hilbert space. We prove a strong convergence theorem of the proposed iterative scheme under some suitable conditions on the parameters. Furthermore, we apply our main result for W-mappings. Finally, we give two numerical results to show the consistency and accuracy of the scheme. 相似文献
80.
Farideh Abbasi Shahram Mehdipour‐Ataei Zahra Tabatabaei‐Yazdi Samal Babanzadeh Ebrahim Abouzari‐Lotf 《先进技术聚合物》2017,28(3):404-410
A new poly(sulfone ether imide) was prepared, and related nanocomposites were produced through introduction of sepiolite nanoparticles into the matrix of polymer. Inherent viscosity, thermal and mechanical features of pristine poly(sulfone ether imide), and nanocomposite samples were evaluated and compared. The crystallinity was also investigated. Dispersion and distribution behaviors of nanocomposite samples and cross‐sectional morphology of nanocomposite films were also studied. Also, the optimized amounts of sepiolite nanoparticles in the matrix of polymer were determined by microscopic techniques (scanning electron microscope and transmission electron microscope). By introduction of 3 wt% of sepiolite, superior thermal and mechanical properties were observed. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献