Laser-induced fabrication of highly branched CuS nanocrystals with excellent near-infrared absorption properties

We report on the successful fabrication of highly branched Cu S nanocrystals by laser-induced photochemical reaction.Surprisingly, the single-crystalline nature with preferential alignment of the（107） orientation can be well improved during the moderate growth process. The branch length drastically increases from about 5 nm to 6 μm with an increase of photochemical reaction time（0-40 min）. The absorption spectra of as-prepared Cu S nanodendrites show that localized surface plasmon resonance（LSPR） peaks can be modulated from about 1037 nm to 1700 nm with an increase of branch length. Our results have a promising potential for photodynamic therapy and biological imaging application.

Spin Coulomb Dragging Inhibition of Spin-Polarized Electric Current Injecting into Organic Semiconductors

We introduce a one-dimensional spin injection structure comprising a ferromagnetic metal and a nondegenerate organic semiconductor to model electric current polarizations. With this model we analyse spin Coulomb dragging （SCD） effects on the polarization under various electric fields, interface and conductivity conditions. The results show that the SCD inhibits the current polarization. Thus the SCD inhibition should be well considered for accurate evaluation of current polarization in the design of organic spin devices.

Transmission Properties of an Air Waveguide with Left-Handed Holographic Photonic Crystal Cladding

An air waveguide of left-handed photonic crystal （PhC） formed by holographic lithography is proposed. The symmetry mismatch between the incident wave and the Bloch modes of the holographic PhC is used to guide light efficiently. By properly designing the waveguide, backscattering loss can be significantly reduced. Due to the unique advantages of holographic photonie crystals, the serious problems of material loss and fabrication difficulty in left-handed material waveguides are also avoided. Furthermore it is shown that high transmission efficiency is easily achieved in the frequencv region with effective refraction index near zero. These features may extend the possible guiding ability of holographic photonic crystal waveguide and its promising potential in the application of photonic integrated circuits.

Cylindrical and Spherical Membranes of Anodic Aluminum Oxide with Highly Ordered Conical Nanohole Arrays

Nanoporous anodic aluminum oxide (AAO) with uniform and controllable pore diameters and periods over a wide range has been explored for various applications due to relatively easy fabrication processes. Moreover, one of the interesting possibilities afforded by the anodization process is that the anodization can take place on aluminum films with arbitrary shape, such as a section of cylinder or sphere, which has not yet been well studied or applied in nanofabrication. In this paper, we report that highly ordered conical nanohole arrays prepared by the anodization of cylindrical and spherical Al films have been fabricated. As can be seen by scanning electron microscopy (SEM), straight nanohole arrays have been grown along the radical directions of the cylindrical or spherical alumina membrane without bending or branching at all, the diameter of the conical nanoholes and the diameter change along individual channels can be tuned by changing the curvature of the membrane. These new types of templates may open new opportunities in optical, electronic and electrochemical applications.

The effect of spin-orbit coupling on magnetoresistance in nonmagnetic organic semiconductors

We investigated the effect of spin-orbit coupling on magnetoresistance in nonmagnetic organic semiconductors.A Lorentz-type magnetoresistance is obtained from spin-orbit coupling-dependent spin precession under the condition of a space-charge-limited current.The magnetoresistance depends on the initial spin orientation of the electron with respect to the hole in electron-hole pairs,and the increasing spin-orbit coupling slows down the change in magnetoresistance with magnetic field.The field dependence,the sign and the saturation value of the magnetoresistance are composite effects of recombination and dissociation rate constants of singlet and triplet electron-hole pairs.The simulated magnetoresistance shows good consistency with the experimental results.

Investigation of Barree-Conway non-Darcy flow effects on coalbed methane production

Coalbed gas non-Darcy flow has been observed in high permeable fracture systems,and some mathematical and numerical models have been proposed to study the effects of non-Darcy flow using Forchheimer non-Darcy model.However,experimental results show that the assumption of a constant Forchheimer factor may cause some limitations in using Forchheimer model to describe non-Darcy flow in porous media.In order to investigate the effects of non-Darcy flow on coalbed methane production,this work presents a more general coalbed gas non-Darcy flow model according to Barree-Conway equation,which could describe the entire range of relationships between flow velocity and pressure gradient from low to high flow velocity.An expanded mixed finite element method is introduced to solve the coalbed gas non-Darcy flow model,in which the gas pressure and velocity can be approximated simultaneously.Error estimate results indicate that pressure and velocity could achieve first-order convergence rate.Non-Darcy simulation results indicate that the non-Darcy effect is significant in the zone near the wellbore,and with the distance from the wellbore increasing,the non-Darcy effect becomes weak gradually.From simulation results,we have also found that the non-Darcy effect is more significant at a lower bottom-hole pressure,and the gas production from non-Darcy flow is lower than the production from Darcy flow under the same permeable condition.

Experimental study of regional fractal speckle produced in large angle scattering

Using the interference of speckle and the spherical reference wave, we extract the real and the imaginary parts of the complex amplitudes of the speckle in large angle scattering. By calculating the spatial correlation functions of intensity, we find that the speckle has a property of regional fractality, i.e. the fractal exponent equals 1 in a small spatial region and it becomes less than 1 in a bigger region. The empirical analytic expression of the intensity correlation function is gained. The probability density distributions of the intensities and the complex amplitudes show that the regional fractal speckle still obeys zero-mean circular complex Gaussian statistics.

Correlation and fractal properties of speckles in the extremely deep Fresnel diffraction region

Based on the Kirchhoff approximation and the theoretical analysis of the random light fields, the speckle intensity distributions in the extremely deep Fresnel diffraction region are simulated. The fractal property of the speckles as well as the relation between the speckle intensity distribution and the corresponding random surface is investigated. We design a microscope system to detect experimentally the speckles in the extremely deep Fresnel diffraction region, and the experimental results prove the conclusions drawn from our simulations.

First-Principle Studies on the Ga and As Doping of Germanane Monolayer

The study of energetics, structural, the electronic and optical properties of Ga and As atoms substituted for doped germanane monolayers were studied by first-principles calculations based on density functional theory. Both of the two doping are thermodynamically stable. According to the band structure and partial density of the states, gallium is p-type doping. Impurity bands below the conduction band lead the absorption spectrum moves in the infrared direction. Arsenic doping has impurity level passing through the Fermi level and is n-type doping. The analysis of optical properties confirms the value of bandgap and doping properties.

Investigation of Critical Thinking Tendency of Engineering Students and Analysis of Teaching Countermeasures

“New Engineering”construction puts forward higher requirements for the critical thinking ability of engineering talents in the future.With“California Critical Thinking Disposition Inventory Chinese Revision”,the critical thinking tendency of engineering majors in local engineering colleges was investigated and analyzed.The results showed that the critical thinking level of the engineering students was obviously lower.According to the findings and teaching practice,this paper gives some teaching countermeasures to strengthen the cultivation of critical thinking of engineering students.

Extraction of Parameters of Random Self-Affine Fractal Surfaces from Light Scattered Intensity by Levenberg-Marquardt Algorithm

A method for simultaneously extracting the parameters of self-affine fractal surfaces from a single experimental profile of scattered intensity data is proposed. The Levenberg-Marquardt algorithm is introduced to fit the theoretical equation for the scattering intensity profile to the experimental data. A precision system is designed for acquisition of scattering intensity data using the Boxcar integration technique. The surface parameters extracted （root-mean-square roughness w, lateral correlation length ζ, and roughness exponent α） are compared to those obtained using atomic force microscopy.

Energetic Evolution of Single-Crystalline ZnO Nanowires and Nanotubes

We report the formation energies of wurtzite zinc oxide （w-ZnO） nanowires （NWs） and nanotubes （NTs） with faceted morphologies, and show that hexagonal NWs （h-NWs） are energetically advantageous over the NWs with rhombic （r-）, squared （s-）, and triangular （t-） cross sections. The formation energies of h-NWs are proportional to the inverse of wire radius, whereas those of single-crystalline NTs are proportional to the inverse of wall thickness, irrespectively to tube radius. A simple model is presented to interpret these features.

Spin-Polarized Carriers Injection from Ferromagnetic Metal into Organic Semiconductor

Charge carriers in organic semiconductor are different from that of traditional inorganic semiconductor. Based on three-current model, considering electrical field effect, we present a theoretical model to discuss spin-polarized injection from ferromagnetic electrode into organic semiconductor by analyzing electrochemical potential both in ferromagnetic electrode and organic semiconductors. The calculated result of this model shows effects of electrode＇s spin polarization, equilibrium value of polarons ratio, interracial conductance, bulk conductivity of materials and electrical field. It is found that we could get decent spin polarization with common ferromagnetic electrode by increasing equilibrium value of polarons ratio. We also find that large and matched bulk conductivity of organic semiconductor and electrode, small spin-dependent interracial conductance, and enough large electrical field are critical factors for increasing spin polarization.

Coefficient Multipliers on Some Analytic Function Spaces

In this paper, we give some new results of the coefficient multiplier of some analytic function spaces, characterize the coefficient multiplier spaces (Hα, p Hβ q) and (Ap,α), Aq,β) with 0 < p ≤ 1, p ≤ q ≤∞, 0 ≤α < β < ∞ and show (Hα∞, Hβ∞) = Hβ-α1 with 0 < α < β < ∞.

Two waveguide layers in lithium niobate crystal formed by swift heavy Kr ion irradiation

We report the formation of two waveguide layers in a lithium niobate crystal by irradiation with swift heavy Kr ions with high （GeV） energies and ultralow fluences. The micro-Raman spectra are measured at different depths in the irradiated layer and show that the high electronic energy loss can cause lattice damage along the ion trajectory, while the nuclear energy loss causes damage at the end of the ion track. Two waveguide layers are formed by confinement with two barriers associated with decreases in the refractive index that are caused by electronic and nuclear energy losses, respectively.

The Rectangle Rule for Computing Cauchy Principal Value Integral on Circle

The classical composite rectangle (constant) rule for the computation of Cauchy principle value integral with the singular kernel is discussed. We show that the superconvergence rate of the composite midpoint rule occurs at certain local coodinate of each subinterval and obtain the corresponding superconvergence error estimate. Then collation methods are presented to solve certain kind of Hilbert singular integral equation. At last, some numerical examples are provided to validate the theoretical analysis.

Controlled fabrication of Fe_(3)N@NG composites as superior oxygen evolution reaction electrocatalysts

We report the controlled fabrication of nitrogen doped graphene(NG)nanoplates,which are uniformly decorated with iron nitride(Fe_(3)N)nanoparticles,via ball milling of mixtures of graphite and iron nitrates and the following ammonia annealing.The obtained Fe_(3)N@NG composites demonstrate excellent electrocatalytic activity and durability for oxygen evolution reaction,both of which outperform those of the state-of-the-art iridium oxide catalysts.This may be attributed to nitrogen doping as well as the synergistic effect between Fe3N and graphene nanoplates.

OSCILLATION OF THIRD-ORDER NONLINEAR DELAY DIFFERENTIAL EQUATIONS

In this paper, we give some new criteria for the asymptotic behavior and oscillation of third-order delay differential equation. The oscillation of the studied equation is studied under two conditions, and our results improve some ones in D?urina et al.(2018). Some examples are given to illustrate the main results with Euler-type differential equations.

Gorenstein Projective Dimensions of Modules over Minimal Auslander-Gorenstein Algebras

In this article we investigate the relations between the Gorenstein projective dimensions of Λ-modules and their socles for re-minimal Auslander-Gorenstein algebras Λ.First we give a description of projective-injective Λ-modules in terms of their socles.Then we prove that a Λ-module N has Gorenstein projective dimension at most n if and only if its socle has Gorenstein projective dimension at most n if and only if N is cogenerated by a projective Λ-module.Furthermore,we show that n-minimal Auslander-Gorenstein algebras can be characterised by the relations between the Gorenstein projective dimensions of modules and their socles.

Arbitrary manipulations of focused higher-order Poincare beams by a Fresnel zone metasurface with alternate binary geometric and propagation phases

The manipulation of high-quality vector beams(VBs)with metasurfaces is an important topic and has potential for classical and quantum applications.In this paper,we propose a Fresnel zone(FZ)metasurface with metallic nanoslits arranged on FZs,which sets alternate binary geometric and propagation phases to cancel the incident spin component and focus the converted spin component(CSC).The rotation designs of nanoslits transform the incident polarization state on the conventional Poincare sphere to VBs on the higher-order Poincare(HOP)sphere.The two orbital angular momentum states of the CSCs were manipulated,and the focused HOP beams were generated.The experimental results demonstrate the broadband generation of arbitrarily focused HOP beams of high quality under the illumination of the red(632.8 nm),green(532 nm),and blue(473 nm)light.This work will be of significance for the applications of VBs in different areas,such as precision metrology,optical micromanipulation,and quantum information.