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1.
Journal of Fluorescence - A wide variety of medical, biomedical, and industrial applications has been reported for quinoxalines derivatives. In this work, a novel quinoxaline derivative was...  相似文献   
2.
In this work, an easily obtained procedure was successfully implemented to prepare novel palladium nanoparticles decorated on triethanolammonium chloride ionic liquid‐functionalized TiO2 nanoparticles [TiO2/IL‐Pd]. Different methods were carried out for characterizations of the synthesized nanocatalyst (HR‐TEM, XPS, XRD, FE‐SEM, EDX, FT‐IR and ICP). TiO2/IL‐Pd indicated good catalytic activity for the Suzuki–Miyaura cross‐coupling reaction of arylboronic acid with different aryl halides in aqueous media at ambient temperature. The recycled catalyst was investigated with ICP to amount of Pd leaching after 6 times that had diminished slightly, Thus, was confirmed that the nanocatalyst has a good sustainability for C–C Suzuki–Miyaura coupling reaction. The catalyst can be conveniently separated by filtration of the reaction mixture and reused for 6 times without significant loss of its activity. It supplies an environmentally benign alternative path to the existing protocols for the Suzuki–Miyaura reaction.  相似文献   
3.
Turbulent flow over variably-shaped rough walls, characterized by either a regular or a random arrangement of axisymmetric roughness elements in an open channel flow configuration, is investigated computationally within a VLES (Very Large Eddy Simulation) framework by utilizing a volumetric forcing-based roughness model. The prime objective of the present work is to assess the roughness model’s capability to predict mean velocities and turbulent intensities in conjunction with this recently formulated hybrid LES/RANS (Reynolds-Averaged Navier-Stokes) model. The friction velocity-based Reynolds number is in the range Reτ =?460 ? 500. A non-dimensional drag function accounting for the shape of the roughness elements is introduced and evaluated based on the results of complementary direct numerical simulations (DNS). The dynamics of the residual motion of the presently adopted VLES methodology is described by an appropriately modified elliptic-relaxation-based ζ ? f (\(\zeta =\overline {v^{2}}/k\)) RANS model.  相似文献   
4.
Wave interaction with bodies is an important practical application for smoothed particle hydrodynamics (SPH) which in principle applies to steep and breaking waves without special treatment. However, few detailed tests have been undertaken even with small amplitude waves. In order to reduce computer time a variable particle mass distribution is tested here with fine resolution near the body and coarse resolution further away, while maintaining a uniform kernel size. We consider two well‐defined test cases, in two dimensions, of waves generated by a heaving semi‐immersed cylinder and progressive waves interacting with a fixed cylinder. But first, still water with hydrostatic pressure is tested. The open‐source code SPHysics ( http://www.sphysics.org )§Update made here after initial online publication. is used with a Riemann solver in an Arbitrary Lagrangian–Eulerian formulation. For the heaving cylinder, SPH results for far field wave amplitude and cylinder force show good agreement with the data of Yu and Ursell (J. Fluid Mech. 1961; 11 :529–551). For wave loading on a half‐submerged cylinder the agreement with the experimental data of Dixon et al. (J. Waterway Port Coastal Ocean Div. 1979; 105 :421–438) for the root mean square force is within 2%. For more submerged cases, the results show some discrepancy, but this was also found with other modelling approaches. The sensitivity of results to the value of the slope limiter used in the MUSCL‐based Riemann solver is demonstrated. The variable mass distribution leads to a computer run speedup of nearly 200% in these cases. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
5.
Steady and pulsatile flow and heat transfer in a channel lined with two porous layers subject to constant wall heat flux under local thermal non-equilibrium (LTNE) condition is numerically investigated. To do this, a physical boundary condition in the interface of porous media and clear region of the channel is derived. The objective of this work is, first, to assess the effects of local solid-to-fluid heat transfer (a criterion indicating on departure from local thermal equilibrium (LTE) condition), solid-to-fluid thermal conductivity ratio and porous layer thickness on convective heat transfer in steady condition inside a channel partially filled with porous media; second, to examine the impact of pulsatile flow on heat transfer in the same channel. The effects of LTNE condition and thermal conductivity ratio in pulsatile flow are also briefly discussed. It is observed that Nusselt number inside the channel increases when the problem is tending to LTE condition. Therefore, careless consideration of LTE may lead to overestimation of heat transfer. Solid-to-fluid thermal conductivity ratio is also shown to enhance heat transfer in constant porous media thickness. It is also revealed that an increase in the amplitude of pulsation may result in enhancement of Nusselt number, while Nusselt number has a minimum in a certain frequency for each value of amplitude.  相似文献   
6.
A rapid and effective preconcentration method for extraction of rhodamine 6G was developed by using a dispersive liquid-liquid microextraction (DLLME) prior to UV-vis spectrophotometry. In this extraction method, a suitable mixture of acetone (disperser solvent) and chloroform (extractant solvent) was injected rapidly into a conical test tube containing aqueous solution of rhodamine 6G. Therefore, a cloudy solution was formed. After centrifugation of the cloudy solution, sedimented phase was evaporated, reconstituted with methanol and measured by UV-vis spectrophotometry. Different operating variables such as type and volume of extractant solvent, type and volume of disperser solvent, pH of the sample solution, salt concentration and extraction time were investigated. The optimized conditions (extractant solvent: 300 μL of chloroform, disperser solvent: 3 mL of acetone, pH: 8 and without salt addition) resulted in a linear calibration graph in the range of 5-900 ng mL−1 of rhodamine 6G in initial solution with R2 = 0.9988 (n = 5). The Limits of detection and quantification were 2.39 and 7.97 ng mL−1, respectively. The relative standard deviation for 50 and 250 ng mL−1 of rhodamine 6G in water were 2.88% and 1.47% (n = 5), respectively. Finally, the DLLME method was applied for determination of rhodamine 6G in different industrial waste waters.  相似文献   
7.
The magnetically recyclable graphene oxide-Fe3O4/polyallylamine (PAA)/Ag nanocatalyst was prepared via a green route using Eucalyptus comadulensis leaves extract as both reducing and stabilizing agent. The catalytic activity of this nanocatalyst was investigated for the reduction reaction of methylene blue and methyl orange in the presence of NaBH4 in aqueous medium at room temperature. The prepared nanocatalyst was characterized by different methods such as Fourier transformed infrared spectroscopy, X-ray diffraction, scanning electron microscopy–energy dispersive X–ray spectroscopy, thermogravimetric analysis, vibrating sample magnetometer, transmission electron microscopy, and UV–visible spectroscopy. The results show that graphene oxide/PAA/Ag nanocatalyst has good activity and recyclability, and can be reused several times without major loss of activity in the reduction process. The apparent rate constants of the methyl orange (MO) and methylene blue (MB) were calculated to be 0.077 s−1 (3 mg of catalyst) and 0.15 s−1 (2 mg of catalyst), respectively.  相似文献   
8.
Research on Chemical Intermediates - This study was conducted to synthesize and characterize the ZVINs stabilized with acid ascorbic (AAS-ZVINs) and to assess their ability to immobilize Pb2+ in...  相似文献   
9.
In this paper, the characteristics of structure II krypton hydrate are studied by molecular dynamics simulation under isobaric-isothermal (NPT) ensemble condition. The dissociation process of the hydrate is simulated and the effect of krypton (Kr) and various types of hydrocarbon guest molecules (HGMs) on the stability of the hydrate structure is investigated during the simulation time of 1 ns. The studied HGMs are propane, isobutane, neopentane, cyclopropane, cyclobutane, cyclopentane and cyclopentene. The structural change of the Kr-hydrate is analyzed with the radial distribution function, mean square displacement and diffusion coefficient. As temperature increases, the obtained results indicate a gradual increase in the Kr-hydrate cell size, which leads to distortion of the hydrate lattice and escaping of the encapsulated Kr molecules from the hydrate structure to form small bubbles of Kr aggregated in the aqueous solution.  相似文献   
10.
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