Linear Analysis of Longshore Currents Instability over Mild Slopes

Longshore current instability is important to nearshore hydrodynamic and sediment transport. This paper investigates the longshore current instability growth model based experimental data with different velocity profiles of slopes1:100 and 1:40 by adopting a linear shear instability model with the bottom friction effects. The results show that:(1)Only backshear mode exists in the instability of longshore current for slope 1:40 and frontshear and backshear modes may exist slope 1:100.(2) The peaks of linear instability growth mode for slope 1:100 correspond to three cases: the dominant peak is formed by the joint action of both frontshear and backshear, or by backshear alone without the existence of the smaller peak or formed by either the frontshear or backshear.(3) Bottom friction can decrease the corresponding unstable growth rate but it cannot change the unstable fluctuation period. The results of fluctuation period, wavelength and spatial variation obtained by the analysis of linear shear instability are in good agreement with experimental results.

Analytical solution of time fractional Cattaneo heat equation for finite slab under pulse heat flux

A fractional Cattaneo model is derived for studying the heat transfer in a finite slab irradiated by a short pulse laser. The analytical solutions for the fractional Cattaneo model, the classical Cattaneo-Vernotte model, and the Fourier model are obtained with finite Fourier and Laplace transforms. The effects of the fractional order parameter and the relaxation time on the temperature fields in the finite slab are investigated.The results show that the larger the fractional order parameter, the slower the thermal wave. Moreover, the higher the relaxation time, the slower the heat flux propagates. By comparing the fractional order Cattaneo model with the classical Cattaneo-Vernotte and Fourier models, it can be found that the heat flux predicted using the fractional Cattaneo model always transports from the high temperature to the low one, which is in accord with the second law of thermodynamics. However, the classical Cattaneo-Vernotte model shows that the unphysical heat flux sometimes transports from the low temperature to the high one.

Experimental Study on Crescent Waves Diffracted by A Circular Cylinder

Crescent waves often observed on the sea surface are unusual wave pattern induced by the instability of Stokes wave.The paper presents the experimental results of the wave field around a circular cylinder generated by the diffraction of crescent wave in order to examine the difference of diffracted crescent waves from the commonly-used diffracted Stokes waves. The results show that with the existence of the cylinder, the crescent wave pattern can still get fully developed, and with the presence of this type of wave pattern, the symmetry breaking of the wave amplitude distribution occurs and there are extra wave components at the frequencies of 0.5 ω;, 1.5ω;and 2.5ω;（ω;is the frequency of Stokes waves） appearing in the wave amplitude spectrum.

Screening promising TM-doped CeO_(2) monolayer for formaldehyde sensor with high sensitivity and selectivity

Developing convenient,fast-response and high-performance formaldehyde detection sensor is significant but challenging.Herein,two CeO_(2) phases(Fm■m and P4_(2)/mnm),three facets(CeO_(2)(100),CeO_(2)(110)and CeO_(2)(111))and three adsorption sites(top,bridge and hollow)are selected as substrate to interact with formaldehyde.Twenty-eight candidated transition metals(TM)are doped on CeO_(2) surfaces to investigate the performance of detecting formaldehyde by density functional theory.It shows that(i)CeO_(2) in a cubic fluorite structure with the space group Fm■m is suitable for formaldehyde adsorption compared with P4_(2)/mnm;(ii)TM-CeO_(2)(100)(TM=Au,Hf,Nb,Ta,Zr)are considered as candidated materials to absorb formaldehyde ascribed to lower adsorption energies.The d-band center,partial density of states,charge density difference and electron localization function are employed to clarify the mechanism of TM-doped CeO_(2) improving the performance of formaldehyde adsorption.It obviously displays that TM doped CeO_(2)(100)changes the d orbit and rearranges electrons resulting in the superior ability to the adsorbed formaldehyde.This work provides theoretical guidance and experimental motivation for the development of novel formaldehyde sensor based on metal oxide semiconductor materials.