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61.
Efficient and continuous monoacylation of symmetrical diamines performed in microreactors yielded superior selectivity to that predicted by statistical considerations. It is highly valuable that the kinetically controlled product in high yields was achieved without any special catalyst at ambient temperature. 相似文献
62.
Thi Bang Tam Dao Kim Ngoc Pham Yi-Lung Cheng Sang Sub Kim Bach Thang Phan 《Current Applied Physics》2014,14(12):1707-1712
The as-deposited WO3 thin films were post-annealed at different temperatures (300 °C and 600 °C) in air to investigate a correlation between crystallinity and switching behavior of WO3 thin films. Associating the results of XRD, FTIR, XPS and FESEM measurements, the annealing-caused crystallinity change contributes to the variation of the switching behaviors of the WO3 thin films. The as-deposited WO3 films with low crystalline structure are preferred for random Ag conducting path, resulting in large switching ratio but fluctuating I–V hysteresis, whereas the annealed WO3 films with crystallized compact structure limits Ag conducting path, favoring the stable I–V hysteresis but small switching ratio. It is therefore concluded that electrochemical redox reaction-controlled resistance switching depends not only on electrode materials (inert and reactive electrodes) but also on crystallinity of host oxide. 相似文献
63.
Santhanamoorthi Nachimuthu Yi-Hui Kuo Dang Hoai Khanh Zhan-Jun Zhu Jyh-Chiang Jiang 《中国化学会会志》2023,70(3):349-358
The ability of the polymer-based graphitic carbon nitride (g-C3N4) as a gas sensor toward NO, NO2, CO, CO2, SO2, SO3, and O2 gasses is assessed using density functional theory (DFT) calculations in terms of energetic and electronic transport characteristics. In particular, this study is aimed to explore the role of zigzag and armchair edges of the g-C3N4 sheet on sensing performances. The electronic properties of adsorption systems, such as Bader charge analysis, band gaps, work function, and density of states (DOS), are used to understand the interaction between the adsorbed gas molecules and the g-C3N4 sheet. Our calculated results indicate that SOx (SO3 and SO2) gasses have higher adsorption energies on the g-C3N4 sheet than other gasses. Furthermore, the transport properties, such as current–voltage (I-V) and resistance-voltage (R-V) curves along the zigzag and armchair directions are calculated using the non-equilibrium Green's function (NEGF) method to understand the performance of the g-C3N4 sheet as a prominent conductive/resistive sensor. The I-V/R-V results indicate that the zigzag g-C3N4 sheet has excellent sensing ability toward SOx gasses at low applied voltages. However, the presence of H2O degrades the sensing performance of the armchair g-C3N4 sheet. Theoretical recovery time has also been calculated to evaluate the reusability of g-C3N4 sheet-based gas sensors. Our results reveal that the zigzag g-C3N4 sheet-based sensing device has a remarkably high sensitivity (>300%) and selectivity toward SOx gasses and has the potential to work in a complex environment. 相似文献
64.
We present an all-fiber bidirectional passively mode-locked soliton laser with what we believe is a novel cavity configuration. Using a four-port circulator, we incorporate two different semiconductor saturable absorber mirrors (SESAMs) into the laser cavity, which enables bidirectional mode locking. The laser allows the generation of two independent countercirculating mode-locked pulse trains, each with an individual fundamental repetition rate that can be adjusted by varying the SESAM pigtail length. Two countercirculating pulse trains with repetition rates of 21.3 and 15.2 MHz are obtained simultaneously. By controlling the intracavity loss imposed on these two pulse trains, either one of the two pulse trains can be switched on or off. The bidirectional operation with other repetition rates is also demonstrated. 相似文献
65.
66.
Hang T. T. Phan Kaizheng Zhu Anna-Lena Kjøniksen Bo Nyström 《Colloid and polymer science》2011,289(9):993-1003
Temperature-induced interchain association and contraction of species in aqueous solutions of charged (MHEC(−)-g-PNIPAAM) and uncharged (MHEC-g-PNIPAAM) modified hydroxyethylcellulose-graft-poly(N-isopropylacrylamide) copolymer have been studied with the aid of turbidimetry and dynamic light scattering (DLS). It was
shown that by attaching PNIPAAM chains to the backbone of a hydrophilic cellulose derivative, a strongly temperature-responsive
copolymer could be prepared. The results show an intriguing interplay between interchain association and contraction of the
multichain species. The transition zone for compression is narrow, and the compaction effect is promoted by a low polymer
concentration and charges on the polymer moieties. The findings from DLS revealed two populations of species, namely molecularly
dispersed molecules or small clusters and interchain complexes, which exhibit temperature-induced collapse. The magnitude
of the cluster contraction can be modulated by changing the polymer concentration and charge density of the copolymer. 相似文献
67.
We use the first and second order approximations of mappings to establish both necessary and sufficient optimality conditions for unconstrained and constrained nonsmooth vector optimization problems. Ideal solutions, efficient solutions, and weakly efficient solutions are considered. The data of the problems need not even be continuous. Some often imposed compactness assumptions are also relaxed. Examples are provided to compare our results and some known recent results.This work was partially supported by the National Basic Research Program in Natural Sciences of Vietnam. 相似文献
68.
Summary A variant of the boundary element method, called the boundary contour method, offers a further reduction in dimensionality.
Consequently, boundary contour analysis of 2-D problems does not require any numerical integration at all. In a boundary contour
analysis, boundary stresses can be accurately computed using the approach proposed in Ref. [1]. However, due to singularity,
this approach can be used only to calculate boundary stresses at points that do not lie at an end of a boundary element. Herein,
it is shown that a technique based on the displacement/velocity shape functions can overcome this drawback. Further, the approach
is much simpler to apply, requires less computational effort, and provides competitive accuracy. Numerical solutions and convergence
study for some well-known problems in linear elasticity and Stokes flow are presented to show the effectiveness of the proposed
approach.
This research was supported in part by the 2004 Ralph E. Powe Junior Faculty Enhancement Award from Oak Ridge Associated Universities
and by the University of South Alabama Research Council. 相似文献
69.
Numerical simulations of a spherical particle sedimenting in circular, triangular and square conduits containing a viscous, inertialess, Newtonian fluid were investigated using the Boundary Element Method (BEM). Settling velocities and pressure drops for spheres falling along the centre-lines of the conduits were computed for a definitive range of sphere sizes. The numerical simulations for the settling velocities showed good agreement with existing experimental data. The most accurate analytic solution for a sphere settling along the axis of a circular conduit produced results which were almost indistinguishable from the present BEM calculations. For a sphere falling along the centre-line of a square conduit, the BEM calculations for small spheres agreed well with analytic results. No analytic results for a sphere falling along the axis of a triangular conduit were available for comparison. Extrapolation of the BEM predictions for the pressure drops, to infinitely small spheres, showed remarkable agreement with analytic results. For the circular conduit, the sphere's settling velocity and angular velocity were computed as a function of drop position for small, medium and large spheres. Excellent agreement with a reflection solution was achieved for the small sphere. In addition, end effects were investigated for centre-line drops and compared where possible with available experimental data and analytic results.Los Alamos National Laboratory, Los Alamos, New Mexico, USA. 相似文献
70.