Structure and magnetic properties of co-sputtered Co–C thin films

We studied the structure and magnetic properties of co-sputtered Co_1−xC_x thin films using a transmission electron microscope (TEM) and a SQUID magnetometer. These properties were found to depend critically on deposition temperature, T_S, and composition, x. Generally, phase separation into metallic Co and graphite-like carbon phases proceeds with increasing T_S and decreasing x. Plan view and cross-sectional TEM images of the films prepared showed that Co grains about 10–20 nm in diameter and 30–50 nm in height are three-dimensionally separated by graphite-like carbon layers 1–2 nm thick. Optimum magnetic properties with saturation magnetization of 380 emu/cc and coercivity of 400 Oe were obtained for a film with x=0.5 and T_S=350°C.     

Self-consistent three-dimensional modeling and simulation of large-scale rectangular surface-wave plasma source

A self-consistent and three-dimensional (3D) model of argon discharge in a large-scale rectangular surface-wave plasma (SWP) source is presented in this paper, which is based on the finite-difference time-domain (FDTD) approximation to Maxwell's equations self-consistently coupled with a fluid model for plasma evolution. The discharge characteristics at an input microwave power of 1200~W and a filling gas pressure of 50~Pa in the SWP source are analyzed. The simulation shows the time evolution of deposited power density at different stages, and the 3D distributions of electron density and temperature in the chamber at steady state. In addition, the results show that there is a peak of plasma density approximately at a vertical distance of 3~cm from the quartz window.     

Image encryption using a synchronous permutation-diffusion technique

In the past decade, the interest on digital images security has been increased among scientists. A synchronous permutation and diffusion technique is designed in order to protect gray-level image content while sending it through internet. To implement the proposed method, two-dimensional plain-image is converted to one dimension. Afterward, in order to reduce the sending process time, permutation and diffusion steps for any pixel are performed in the same time. The permutation step uses chaotic map and deoxyribonucleic acid (DNA) to permute a pixel, while diffusion employs DNA sequence and DNA operator to encrypt the pixel. Experimental results and extensive security analyses have been conducted to demonstrate the feasibility and validity of this proposed image encryption method.     

Tuning the Schottky barrier in the arsenene/graphene van der Waals heterostructures by electric field

Using density functional theory calculations, we investigate the electronic properties of arsenene/graphene van der Waals (vdW) heterostructures by applying external electric field perpendicular to the layers. It is demonstrated that weak vdW interactions dominate between arsenene and graphene with their intrinsic electronic properties preserved. We find that an n-type Schottky contact is formed at the arsenene/graphene interface with a Schottky barrier of 0.54 eV. Moreover, the vertical electric field can not only control the Schottky barrier height but also the Schottky contacts (n-type and p-type) and Ohmic contacts (n-type) at the interface. Tunable p-type doping in graphene is achieved under the negative electric field because electrons can transfer from the Dirac point of graphene to the conduction band of arsenene. The present study would open a new avenue for application of ultrathin arsenene/graphene heterostructures in future nano- and optoelectronics.     

Spectroscopic properties of some mixed ligand copper(II) complexes of N-(2-aminoethyl)-1,2-ethanediamine and ethanediamine and its alkylated derivatives

IR, EPR and electronic spectral studies have been made on a series of complexes with general formula [M(dien)L](BØ₄)₂nH₂O (M = Cu(II), Zn(II), Cd(II), dien = N-(2-aminoethyl)-1,2-ethanediamine, L = ethanediamine (en), Me₄en, Et₂en, Me = methyl, Et = ethyl, BØ₄ = tetraphenylborate, n = 0 or 2] taking copper(II) as a magnetic probe in polycrystalline and solution forms to obtain stereochemical information. A five-coordinate square-based pyramidal (SBP) geometry with CuN₃N′₂ moiety having moderately covalent metal-ligand σ-bonds is found to exist in unalkylated mixed ligand complexes. Among alkylated complexes [Cu/Cd(dien)(Me₄en)](BØ₄)₂ is found to possess two species having tetrahedral and SBP with trigonal bipyramidal distortion geometries unlike the other alkylated complexes which have indicated the presence of one species having SBP coordination geometry with varying degrees of trigonal bipyramidal distortions and metal-ligand σ-bond strengths. EPR studies in dilute dmf and pyridine solutions of copper(II) complexes indicated the presence of solute-solvent interaction.     

并素元有限生成格的弱直积分解

本文建立了并素元有限生成格的弱直积分解,并给出一个解决并素元生成的完全Heyting代数的直积分解问题的新方法;作为弱直积分解的应用,证明了并素元有限生成的完全Heyting代数必然同构于有限个既约的完全Heyting代数的直积,证明了并素元有限生成格是Boole代数的充要条件是它同构于某有限集的幂集格.     

Chromatographic cross-fractionation

Chromatographic cross-fractionation applies current equipment and separation techniques to evaluate the molar mass distribution and chemical composition distribution of co-polymers. In comparison with traditional procedures based on fractional precipitation, chromatographic cross-fractionation offers the advantage of a wider range of application through the participation of stationary phases in separation, saving of time per analysis by a factor of 10³ and reduction of sample size by a factor of 10⁴. It also gives the possibility of automation and computerization of analyses.     

非对称扩散工艺制备近化学计量比钽酸锂晶体的研究

利用气相平衡输运法制备的近化学计量比钽酸锂晶体质量好,制备工艺简单,但受固体扩散速率低的影响,该方法较难制备大厚度晶体。本文基于钽酸锂晶体的扩散机制,采用待扩散晶片一侧为富锂气氛,另一侧为同成分气氛的非对称扩散工艺,对钽酸锂晶体进行了扩散处理,并对组分和畴反转电场进行表征。结果表明,非对称扩散工艺为反位钽离子的扩散提供了通道,提高了晶体中反位钽离子和锂离子的扩散速率,有利于制备大厚度近化学计量比钽酸锂晶体。     

高结晶氮化碳空心球的制备及其增强光催化产氢活性

石墨烯型氮化碳(g-C3N4)已经成为解决环境污染和能源危机问题的较为理想的光催化剂,但由于其较低的比表面积和较高的光生载流子重组效率而表现出较弱的光催化活性.因此,研究者们已经提出了许多策略,例如纳米结构设计,杂原子掺杂和增加结晶度,用来克服氮化碳的这些缺点,从而提高其光催化性能.其中,引起了较多关注的是增加g-C3...     

Photosynthetic production of H2O2 from water at n-TiO2 electrodes in a photoelectrochemical cell: influence of electrolyte pH AND Pt electrodeposition

The electroreduction of photogenerated and/or dissolved oxygen to H₂O₂ at n-TiO₂ polycrystalline electrodes in a photoelectrochemical cell has been studied by means of photocurrent transients and the rotating ring-disk electrode technique. The photoproduction of H₂O₂ from water under open circuit (photocatalytic mode), in a basic medium, reaches an efficiency η (defined as the ratio between the generation rates of H₂O₂ and “effective” h⁺⁺-e⁻ pairs) of ~1%. By contrast, under external polarization (photoelectrochemical mode) η reaches maximum values of about 10%. This value decreases drastically at acidic pHs because of the high overpotential for O₂ electroreduction at n-TiO₂. The effect of Pt overlayers on η has also been analysed.