Results 1 - 10 of 338
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[en] Gold nanoparticle is one of the widely research objects in various fields including catalysis and biotechnology. Precise control of gold nanoparticles placement and their integration is essential to take full advantage of these unique properties for applications. An approach to self-assembling of gold nanoparticles (AuNPs) from reconstructed block copolymer was introduced. Highly ordered polystyrene-block-poly(2-vinylpyridine)(PS-b-P2VP) micellar arrays were obtained by solvent annealing. Subsequent immersion of the films in a preferential solvent for P2VP caused a reorganization of the film to generate a porous structure upon drying. PEG-coated AuNPs were spin-coated onto this reconstruction PS-b-P2VP template. When such films were exposed to toluene vapor-which is non-selective solvent for PEO and P2VP, AuNPs were drawn into those porous to form ordered arrays. Gold nanospheres with size 12±1.8 nm were synthesized by reducing HAuCl4 via sodium citrate. Gold nanorods (aspect ratio about 6) were prepared from seed-mediated surfactant capping wet chemical method and the aspect ratio is tunable by changing surfactant amount. PEG ligand is used to modify gold nanoparticle surface by removing the original surfactant (sodium citrate -gold nanospheres: CTAB-gold nanorods), which have affinity with certain block copolymer component. Once gold nanoparticle is modified with PEG thiol, they were spin coated onto PS-b-P2VP template, which was prepared by solvent annealing and surface reconstruction process. So gold nanoparticle array was fabricated by this self-assembling process. The same idea can be applied on other nanoparticles
[en] Two magnetohydrodynamic (MHD) instabilities are studied. A simple sufficient condition is given for the linear ideal instability of plane parallel equilibria with antisymmetric shear flow and symmetric or antisymmetric magnetic field. Application of this condition demonstrates the destabilizing effect of the magnetic field on shear flow driven Kelvin-Helmholz instabilities. For the resistive tearing instability, the effect of equilibrium shear flow is systematically studied, using the boundary layer approach. Both the constant-psi tearing mode and the nonconstant-psi tearing mode are analyzed in the presence of flow. It is found that the shear flow has a significant influence on both the external ideal region and the internal resistive region. In the external ideal region, the shear flow can dramatically change the value of the matching quantity delta'. In the internal resistive region, the tearing mode scalings are sensitive to the flow shear at the magnetic null plane. When the flow shear is larger than the magnetic field shear at the magnetic null plane, both tearing modes are stabilized. Also, the transition to ideal instability was traced. Furthermore, the influence of small viscosity on the constant-psi tearing mode in the presence of shear flow is considered. It is found that the influence of viscosity depends upon the parameter, v sub 0'(O)B sub 0'(O), where V sub 0'(O) and B sub 0'(O) denote the flow shear and magnetic field shear at the magnetic null plane, respectively. Viscosity basically tends to suppress the tearing mode. Finally, the nonlinear interaction of two near-marginal tearing modes in the presence of shear flow is studied. To find the time asymptotic states, the resistive MHD equations are reduced to four amplitude equations, using center manifold reduction. These amplitude equations are subject to the constraint of translational symmetry of the physical problem
[en] This work investigates the effects of morphological changes of a cement-based material subjected to heat treatment (up to 400 C). For a model W/C=0.5 mortar, we have characterized experimentally hydraulic behaviour (gas permeability), mechanical behaviour (in uniaxial compression, hydrostatic compression with or without deviatoric stress) and poro-mechanical behaviour (incompressibility moduli Kb, Ks and Biot's coefficient b) after a heating/cooling cycle. We have also developed an original experiment aimed at quantifying the accessible pore space volume under hydrostatic compression. The creation of occluded porosity under high confinement is confirmed, which justifies the observed decrease of solid matrix rigidity Ks under high confinement. A gas retention phenomenon was identified under simultaneous thermal and hydrostatic loadings for mortar, and industrial concretes (provided by CERIB and ANDRA). A predictive thermo-elasto-plastic model with isotropic damage and a micro-mechanical approach, which represents micro-cracking, are coupled in order to analyze or predict the evolution of mechanical and poro-elastic properties after heat cycling. (author)
[en] The upper and lower bounds of entanglement of formation are given for two mode squeezed thermal state. The bounds are compared with other entanglement measure or bounds. The entanglement distillation and the relative entropy of entanglement of infinitive squeezed state are obtained at the postulation of hashing inequality
[en] The local release factors kl, which are introduced to stand for the release or elongation effect of the impurity-ligand bond along the C4-axis at the cubic-tetragonal phase transition, are studied by analyzing the EPR zero-field splitting for Cr3+ and Ni2+ ions in RbCdF3 crystals. The results are compared with those of other paramagnetic ions in RbCdF3 and in the similar crystal RbCaF3. It is found that for the same crystal, the factor kl is different from impurity to impurity and that for the same impurity, the factors kl in both RbCdF3 and RbCaF3 crystals are close to each other. The cause of the very small zero-field splitting for Cr3+ in the tetragonal phase of RbCdF3 crystal is suggested
[en] We investigate in the present work the additional data to the previous reported paper (Zhao, et al.) that sufficiently enrich to understand the dielectric diffusive behavior of the (La_x(Na_0_._5Bi_0_._5)_1_-_1_._5_x)_0_._9_7Ba_0_._0_3TiO_3 lead-free ceramics. The dielectric diffusive behavior of the ceramics was investigated using Lorentz-type quadratic relationship and Gaussian-type quadratic relationship. By calculating mean-square-root error and dielectric constant variance, it was found that Lorenz-type quadratic relationship was better to describe the characterization of dielectric diffusive behavior than Gaussian-type quadratic relationship. The results confirm that the increase in La"3"+ content causes an increase in the degree of diffuseness of dielectric peak.
[en] Highlights: • Effects of Si addition on the properties of Fe-based alloy had been investigated. • Si addition was beneficial for enhancing the resistance to oxidation of the alloy. • Tensile strength was increased when Si was added. - Abstract: Effects of Si element on characteristics of Fe–Cr–W–Ti–Y2O3 alloy, including relative density, tensile strength, oxidation resistance and microstructure had been investigated. The results showed that the alloy with Si addition appeared superior properties than alloy without Si. The relative density and tensile strength of alloy without Si were only around 85% and 300 MPa, while that of alloy adding Si could reach up to 96.8% and 692.7 MPa after sintering at 1350 °C. Mass gain of alloy adding Si was approximately one tenth that of alloy without Si when oxidized at 650 °C and 850 °C. These superior properties were attributed to action of Si in sintering and oxidation processes. It would activate the sintering for more dense alloy, and form protective oxidized film preventing diffusion of oxygen and metal atoms
[en] Based on the Scalapino-Huberman μ* model, the possibility of temporally oscillating structures appearing in a superconducting film under high quasiparticle injection is discussed. The range of parameters in which these structures may occur is also given
[en] Structural, vibrational, and magnetic properties of Bi1−xSmxFeO3 (0≤x≤0.20) are investigated by using x-ray powder diffraction, Raman scattering, and magnetometry techniques. We show that the rare-earth ion Sm substitution at Bi site, serving chemical pressure, causes the structural transformation from rhombohedral R3c phase to orthorhombic Pnma phase at x∼0.15, accompanying with the ferroelectric–paraelectric transition. The magnetization is found to be enhanced initially with Sm substitution increasing before approaching ferroelectric–paraelectric boundary but it slightly decreases after passing a maximum. The enhanced magnetization is suggested to stem from the combined effects of the suppressed spin cycloids and increased degree of canting and magnetic interactions between magnetic ions
[en] Highlights: • A new configuration for water-cooled mirror with mini-channels is proposed. • A simplified model is derived for designing of the new configuration. • The new configuration is useful to improve the uniformity of flow field. • It performs well in reducing the thermal distortion of the reflecting surface. - Abstract: A novel water-cooled mirror with interdigitated channels is proposed for solving the problems of high flow resistance and non-uniform heat dissipation in a conventional water-cooled mirror with straight channels. The temperature field and the thermal deformation of the reflecting surface of the mirror are analyzed by fluid-solid-heat coupling simulation. A comparative analysis of the new configuration and the conventional straight channel water-cooled mirror is carried out under equal flow rate and equal pressure drop, respectively. The numerical results demonstrate that the new configuration is better on the consistency of heat transfer coefficients than the conventional one. At the same time, under the condition of equal flow rate, the peak value of the deformation on the reflecting surface is decreased by around 1/3, and the global thermal distortion within the irradiated region is only about half that of the conventional one. Besides, the flow resistance of the new configuration is so small that the flow rate is about triple that of the conventional configuration under the condition of equal pressure drop, which raises its superiority over other designs. The new flow channel structure provides a feasible solution to reduce the thermal deformation of a large size laser mirror.