Deformation analysis of nanocutting using atomistic model

This paper adopts an atomic-scale model based on the atomistic formulation to analyze the deformation mechanism induced in a copper substrate during nanometric cutting process. The deformation evolution during the nanometric cutting process is evaluated using the energy minimization method, thereby greatly reducing the required computation time compared to the traditional Molecular Dynamics (MD) simulations. The simulation results indicate that the microscopic plastic deformation in the substrate is caused by instability of its crystalline structure, and that slip vector analysis reveals the activity of dislocations is the fundamental deformation mechanism during the cutting process.     

基于超声波下淀粉纳米颗粒作载体的基因转导

报道了多聚赖氨酸淀粉纳米颗粒(PLL-StNP)在超声波介导下作基因载体的研究,实验发现DNA-PLL-StNPs复合物经过超声波处理不同的时间后的电泳分析显示,结合的DNA受到保护,其生物学性质没有改变;将pIRGFP质粒DNA-PLL-StNPs复合物与COS-7细胞混合,在120W和40kHz的超声波强度下处理2min,细胞表达绿色荧光蛋白的比率最大,达到70.这种基于超声波下淀粉纳米颗粒作载体的基因转导方法可被广泛应用于动物转基因技术和人类基因治疗,同样可被广泛应用于植物转基因技术.     

预先负载原料法的制备过程对复合分子筛形成的影响

采用预先负载原料法合成了具有核/壳结构的复合分子筛, 并研究了铝源类型和制备过程对反应的影响. 结果表明, 以异丙醇铝为铝源时, 晶化时间较短, 产物中没有SAPO-5晶体, 延长晶化时间可以提高SAPO-5的结晶度. 将负载磷的ZSM-5分别与不同组成的凝胶混合, 经室温陈化后可以明显加快晶化速度. 制备过程中凝胶的水含量和搅拌方式也根据铝源类型的不同有所差别. 当以拟薄水铝石为原料时, 在相同的处理条件下, 产物的结晶度都较高.     

一种圆孔单元厚屏频率选择表面结构的传输特性研究

设计了一种圆孔单元的厚屏频率选择表面(FSS)结构,采用矩量法对该结构的传输特性进行仿真研究.主要研究厚屏FSS在无介质加载条件下,其单元直径、排布周期、电磁波入射角等参数对厚屏FSS传输特性的影响规律.结果发现,厚屏FSS的单元直径、单元间距、入射角对带宽影响较大;而单元直径对中心频率影响不大.     

High-temperature,high-pressure hydrothermal synthesis,crystal structure,and solid state NMR spectroscopy of a new vanadium(IV) silicate: Rb(2)(VO)(Si(4)O(10)).xH(2)O

A new vanadium(IV) silicate, Rb(2)(VO)(Si(4)O(10)).xH(2)O (x approximately 0.1), has been synthesized by a high-temperature, high-pressure hydrothermal method. It crystallizes in the tetragonal space group I4(1)md (No. 109) with a = 12.2225(7) A, c = 7.7948(6) A, and Z = 4. The structure consists of spiral chains of corner-sharing SiO(4) tetrahedra linked to neighboring chains via corner sharing to form a 3-D silicate framework which delimits channels to accommodate the VO(2+) groups. The Rb(+) ions are located in the cavities within the silicate framework. Magnetic susceptibility confirms the valence of vanadium. A partially occupied lattice water site is confirmed by IR and solid state (1)H NMR spectroscopy. The structure of the title compound is considerably different from those of the synthetic silicate K(2)(VO)(Si(4)O(10)).H(2)O and the two polymorphs of the natural mineral Ca(VO)(Si(4)O(10)).4H(2)O, although they have identical framework stoichiometry.     

Preparation and characterization of polymer-dispersed liquid crystal (PDLC) with different cation exchange capacity (CEC) clays

This work describes the morphology and electro-optical properties of polymer-dispersed liquid crystals (PDLCs). These composites consist of the nematic liquid crystal E7, filled with different types of inorganic nanoparticles in Norland optical adhesive (NOA65) polymer matrices. Natural clays CL120 (trade name: CN-C34 with higher cation exchange capacity CEC) and CL42 (trade name: PK802 with lower CEC) are used as various inorganic nanofillers. Wide angle X-ray diffraction was exploited to examine the dispersion of the inorganic nanoparticles in PDLCs. The morphology of liquid crystal droplets in PDLCs is investigated by the field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) as well. Transmittance vs. applied voltage is measured to study the electro-optical properties and the response times of the PDLCs. It is suggested that doping with inorganic nanoparticles in PDLCs effectively reduces the driving voltage and improves the electro-optical characteristics.     

Painlevé analysis, auto-Bäcklund transformation and new analytic solutions for a generalized variable-coefficient Korteweg-de Vries (KdV) equation

There has been considerable interest in the study on the variable-coefficient nonlinear evolution equations in recent years, since they can describe the real situations in many fields of physical and engineering sciences. In this paper, a generalized variable-coefficient KdV (GvcKdV) equation with the external-force and perturbed/dissipative terms is investigated, which can describe the various real situations, including large-amplitude internal waves, blood vessels, Bose-Einstein condensates, rods and positons. The Painlevé analysis leads to the explicit constraint on the variable coefficients for such a equation to pass the Painlevé test. An auto-B?cklund transformation is provided by use of the truncated Painlevé expansion and symbolic computation. Via the given auto-B?cklund transformation, three families of analytic solutions are obtained, including the solitonic and periodic solutions.     

<Emphasis Type="Italic">N</Emphasis>-Solitonic Solution in Terms of Wronskian Determinant for a Perturbed Variable-Coefficient Korteweg-de Vries Equation

With the help of symbolic computation, we first derive the bilinear form and an auto-Bäcklund transformation for a perturbed variable-coefficient Korteweg-de Vries equation in this paper. We also construct the N-solitonic solution in the Wronskian form and give the corresponding proof via the Wronskian technique. Furthermore, the authors verify that the (N?1)- and N-solitonic solutions indeed satisfy the auto-Bäcklund transformation.     

An Amine-Functionalized Zirconium Metal–Organic Polyhedron Photocatalyst with High Visible-Light Activity for Hydrogen Production

Metal–organic polyhedra (MOPs) are promising candidates for many potential applications; however, their use as photocatalysts for hydrogen production has yet to be developed. Herein, the photocatalytic performance of a water-stable Zr-MOP, ZrT-1-NH₂, was evaluated, for the first time, through photocatalytic hydrogen evolution under visible-light irradiation. ZrT-1-NH₂ shows clearly enhanced photocatalytic activity (510.42 μmol g⁻¹ h⁻¹) for hydrogen production, in comparison with that of other homogeneous crystalline materials. If platinum nanoparticles were introduced into the photocatalytic system, the hydrogen production efficiency of ZrT-1-NH₂ could be further improved. For ZrT-1-NH₂, the conspicuous improvement in photocatalysis can be attributed to efficient electron–hole separation, targeted electron transfer, and excellent recombination suppression. Furthermore, ZrT-1-NH₂ shows excellent stability during photocatalytic hydrogen evolution over five continuous runs. This work illustrates that MOP-based photocatalysts hold promise for broad applications in the domain of clean energy.     

Magneticresonant three dimensional kinetic theory of the free electron laser with waveguide cavity

Vlasov kinetic theory of the free electron laser employing waveguide frifting tube and helical pump is presented. Distinct from the former theories this theory has (1) taken into account the 3-d structure of the scattering field; (2) applied the plasma kinetic theory, which is more accurate than the other methods, to analysing the effect of the longitudinal. field; (3) taken account of the influence of the annular structure of the beam. The magnetic resonant effect appearing when the cyclotron frequency of electrons approaches the effective frequency of the magnetic pump is analysed and the growth rate formula in the linear regime derived. Results show that on taking into account the 3-d structure of the field and beam, one cannot arbitrarily choose the radius of the hollow beam, or else within certain range the instability may disappear altogether. Lastly, the equation for determination of the optimum beam radius is given and the possibility of raising growth rate by operating in high order modes shown.