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51.
52.
This study adopts the Tersoff-Brenner interaction potential function in a series of molecular dynamic (MD) simulations which investigate the mechanical properties under tensile loading of (10,0) zigzag, (8,3) chiral and (6,6) armchair single-walled carbon nanotubes (SWCNTs) of similar radii. The Young's modulus values of the (10,0), (8,3) and (6,6) nanotubes are determined to be approximately 0.92, 0.95, and 1.03 TPa, respectively. Of these nanotubes, the results reveal that the (6,6) nanotube possesses the best tensile strength and toughness properties under tension. Although it is noted that under small tensions, the mechanical properties such as Young's modulus are essentially insensitive to helicity, under larger plastic deformations, they may be influenced by helicity effects. Finally, the simulations demonstrate that the values of the majority of the considered mechanical properties decrease with increasing temperature and increasing vacancy percentage. 相似文献
53.
A new and facile synthesis of unsymmetrical heterocyclic azines is described. Methyl arylalkylidenehydraz-inecarbodithioates, prepared by the condensation of ketones or aldehydes with methyl hydrazinecarbodithioate, were heated under reflux with various diamines in ethanol. Secondary diamines, such as N,N′-dimethyl-ethylenediamine, N,N′-dimethyl-1,3-diaminopropane or N,N′-dimethyl-o-phenylenediamine, reacted smoothly with loss of hydrogen sulfide to give good yields of unsymmetrical azines. However, primary diamines, such as ethylenediamine or o-phenylenediamine, and primary/secondary diamines, such as N-methylethyl-enediamine and N-methyl-1,3-diaminopropane gave, instead, only the corresponding uncyclized thiosemi-carbazones. A cyclodesulfurization mechanism for azine formation is discussed. 相似文献
54.
The microemulsion of the H2O/Tween 80/benzene derivative (C6H6, CH3C6H5, NO2C6H5 and NH2C6H5) was investigated by the technique of Photon correlation spectroscopy. Autocorrelation data were measured at 90 scattering angle and were analyzed by using a quadratic fit and linear fit. The quadratic fit was found to describe all Properties better than the linear fit, and thus the linear fit was limited to the region of very short sampling time. When the amount of benzene derivative added to the sample solution was lower than Vmax, the Z-average mean radius, <r>z, and the polydispersit Y, μ2/Γ2, increased as the amount of benzene derivative was increased. When the amount of benzene derivative was larger than Vmax, the aqueous and organic phases separated and the <r> z, and μ2/Γ2 of all phases remained constant. Emulsification did not occur in the organic phase of the H2O/Tween 80/aniline system. When we adjusted the Tween 80 concentration, it was found that <r>z and μ2/Γ2 decreased as the Tween 80 concentration increased. 相似文献
55.
Chu-Fang Wang Fang-Huang Tu Su-Ling Jeng Ching-Jer Chin 《Journal of Radioanalytical and Nuclear Chemistry》1999,242(1):97-103
This study reports the analysis of Si in airborne particulate matter by laser ablation inductively coupled plasma mass spectrometry
(LA-ICP-MS) as well as X-ray fluorescence (XRF). It was found that Si concentration in airborne particulates collected on
PTFE-membrane filters could be accurately determined with a laser beam operated at 160 mJ free running mode, 6.5 mm defocusing
distance and 0.8 l/min carrier gas flow rate during the LA-ICP-MS measurement. Standard filters prepared by NIST SRM 1648
urban particulates were used for both XRF and LA-ICP-MS not only to establish the calibration curves of Si, but also to examine
the proposed method's effectiveness. The capability of applying both methods for natural sample analysis was also examined.
Particulate loaded filter samples collected from a heavily polluted metropolitan area of Kaoshiung, Taiwan were initially
measured by XRF, then by LA-ICP-MS. An intercomparison between them was thus performed. As a result, both XRF and LA-ICP-MS
proved to be the valid analytical methods for directly determining Si concentrations in airborne particulates on PTFE membrane
filters. 相似文献
56.
Various crown ethers were prepared and applied as phase transfer catalysts for the an ionic copolymerization of bisphenol A and 4,4′‐dichlorodiphenyl sulfone monomers with alkali salts, e.g., NaNH2, NaOH and KOH, as initiators. The catalytic abilities of various crown ethers for the an ionic polymerization of bisphenol A / 4,4′‐dichlorodiphenyl sulfone were found to be in the order: 15‐crown‐5 ? monobenzo‐15‐crown‐5 > 18‐crown‐6 > Dicyclohexano‐18‐crown‐6 > Dibenzo‐18‐crown‐6 > 12‐crown‐4 with sodium amide (NaNH2) as initiator. Sodium amide was shown to be a better initiator than NaOH or KOH with monobenzo‐ 15‐crown‐5 as a catalyst. Effects of solvents and temperature on the crown ether catalytic polymerization were also investigated. Dimethyl sulfoxide (DMSO) exhibited much better for the polymerization than other organic solvents, e.g., toluene, p‐xylene, dimethyl formamide and dioxane. Higher polymerization was found at higher temperatures and about 100% yield of poly(bisphenol A / sulfone) was obtained at 125 °C in 3 hr. The molecular weight of poly(bisphenol A / sulfone) as a function of reaction time was determined with gel permeation chromatography. Concentration effects of crown ether on % yield and molecular weight of poly(bisphenol A / sulfone) were also investigated and discussed. 相似文献
57.
An Iron‐Catalyzed Cascade Approach to Benzo[b]carbazole Synthesis Followed by 1,4‐Sulfonyl Migration 下载免费PDF全文
Siva Senthil Kumar Boominathan Gopal Chandru Senadi Dr. Jaya Kishore Vandavasi Dr. Jeff Yi‐Fu Chen Prof. Dr. Jeh‐Jeng Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(8):3193-3197
A simple and straightforward approach was developed to construct 5H‐benzo[b]carbazole derivatives by iron catalysis in a cascade sequence. The notable features of this work include an atom‐economical cascade sequence, unprecedented 1,4‐sulfonyl migration, tolerance of a variety of functional groups, good yields, and an economical catalytic system. 相似文献
58.
In this paper, for two nonempty subsets X and Y of a linear space E, we define the class KKM(X,Y) and investigate the fixed point problem for T∈KKM(X,X) with X an almost convex subset of a locally convex space. Our fixed point theorem contains Lassonde fixed point theorem for Kakutani factorizable multifunctions as special case. 相似文献
59.
We study efficient two-grid discretization schemes with two-loop continuation algorithms for computing wave functions of two-coupled nonlinear Schrödinger equations defined on the unit square and the unit disk. Both linear and quadratic approximations of the operator equations are exploited to derive the schemes. The centered difference approximations, the six-node triangular elements and the Adini elements are used to discretize the PDEs defined on the unit square. The proposed schemes also can compute stationary solutions of parameter-dependent reaction–diffusion systems. Our numerical results show that it is unnecessary to perform quadratic approximations. 相似文献
60.
Hsiao‐Fan Tseng Ming‐Hsiang Cheng Kai‐Sheng Jeng Jia‐Wei Li Jiun‐Tai Chen 《Macromolecular rapid communications》2016,37(22):1825-1831
Anisotropic polymer particles such as Janus particles have attracted significant attention in recent years because of their unique properties and unusual self‐assembly behavior. Most anisotropic polymer particles synthesized so far, however, only have different chemical regions compartmentalized on the particles. It remains a great challenge to fabricate anisotropic polymer particles with different shapes within a single particle. A novel approach is developed to prepare anisotropic polymer particles that contain two hemispheres with different curvatures by annealing polystyrene microspheres on poly(vinyl alcohol) films. During the annealing process, the polymer microspheres gradually sink into the polymer films and transform to asymmetric polymer particles, driven by the surface and interfacial tensions of the polymers. Selective removal techniques are also used to confirm the morphologies of the asymmetric particles.