Hardware implementation of radial-basis neural networks with Gaussian activation functions on FPGA

Neural Computing and Applications - This article introduces a method for realizing the Gaussian activation function of radial-basis (RBF) neural networks with their hardware implementation on...     

Photoluminescence decay rate of silicon nanoparticles modified with gold nanoislands

We investigated plasmon-assisted enhancement of emission from silicon nanoparticles (ncs-Si) embedded into porous SiO _x matrix in the 500- to 820-nm wavelength range. In the presence in the near-surface region of gold nanoisland film, ncs-Si exhibited up to twofold luminescence enhancement at emission frequencies that correspond to the plasmon resonance frequency of Au nanoparticles. Enhancement of the photoluminescence (PL) intensity was attributed to coupling with the localized surface plasmons (LSPs) excited in Au nanoparticles and to increase in the radiative decay rate of ncs-Si. It has been shown that spontaneous emission decay rate of ncs-Si modified by thin Au film over the wide emission spectral range was accelerated. The emission decay rate distribution was determined by fitting the experimental decay curves to the stretched exponential model. The observed increase of the PL decay rate distribution width for the Au-coated nc-Si-SiO _x sample in comparison with the uncoated one was explained by fluctuations in the surface-plasmon excitation rate.

PACS

78. 67. Bf; 78.55.-m     

热泵干燥技术简介

简介热泵干燥技术原理，并通过热泵干燥超细粉末的实验与部分其他应用实例，说明该技术的节能特点及其应用前景。     

Preparation of hydrophobic poly(isobutylene) star polymers with hydrophilic poly(propylene imine) dendritic cores

Summary Poly(propylene imine) dendrimers with amino chain ends have been used for the preparation of hydrophobic star polymers with hydrophilic dendritic cores. The unsaturated end groups of polyisobutylene (PIB) were transformed into reactive anhydride end groups by an “ene” reaction with maleic anhydride, and the resulting functionalized PIB was then reacted with dendrimers to afford dendrimer-PIB star copolymers. Received: 20 May 1999/Accepted: 17 June 1999     

Urokinase-type and tissue-type plasminogen activators as growth factors of human fibroblasts

In this study we have verified the mitogenic effect of urokinase-type (u-PA) and tissue-type plasminogen activators (t-PA) on human normal fibroblasts. We report that both PAs can induce DNA replication and cell division in serum-deprived cultured human skin fibroblasts. The activity of u-PA and t-PA is, respectively, three- and twofold more potent than that exerted by epidermal growth factor (EGF) with an activity slightly lower (50-60%) than that induced by basic fibroblast growth factor (bFGF). The u-PA and t-PA, but not plasmin, induced DNA synthesis, which could be neutralized by anti-u-PA and anti-t-PA antibodies, respectively, but was insensitive to aprotinin treatment. The addition of anti-u-PA-receptor (u-PAR) monoclonal antibodies to the assays selectively suppressed the mitogenic effect exerted by u-PA, but not that of t-PA, and the amino-terminal fragment of u-PA, containing the EGF-like domain and the kringle module, did not elicit any mitogenic activity. Anti-bFGF antibodies completely suppressed the mitogenic activity of bFGF, but did not have any effect on that of u-PA and t-PA; the activity of both PAs was inhibited by anti-fibronectin IgG concentrations ineffective on bFGF. These results indicate that PAs may be considered growth factors of human fibroblasts.     

Molded rigid polymer monoliths as separation media for capillary electrochromatography. 2. Effect of chromatographic conditions on the separation

Monolithic columns for capillary electrochromatography have been prepared within the confines of untreated fused-silica capillaries in a single step by a simple copolymerization of mixtures of butyl methacrylate, ethylene dimethacrylate, and 2-acrylamido-2-methyl-1-propane-sulfonic acid (AMPS) in the presence of a porogenic solvent. The use of these novel macroporous monoliths eliminates the need for frits, the difficulties encountered with packed capillaries, and capillary surface functionalization. Since the porous properties of the monolithic materials can be easily tailored through changes in the composition of the ternary porogenic solvent, the effects of both pore size and the percentage of sulfonic acid monomer on the efficiency and the electroosmotic flow velocity of the capillary columns could be studied independently over a broad range. A simple increase in the content of charged functionalities within the monolith leads to an expected acceleration of the flow velocity. However, increasing the pore size leads to a substantial deterioration of the efficiency of the separation. In contrast, monoliths with increasing levels of AMPS in which the pore size remains fixed due to adjustments in the composition of the porogenic solvent show no deterioration in efficiency while maintaining the same increase in flow velocity, thus producing a significant reduction in separation time. Additionally, measurements on monoliths with constant levels of AMPS but different pore sizes suggest that flow velocity may be affected by the flow resistance within the capillary column.     

Monodisperse hydrolyzed poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads as a stationary phase for normal-phase HPLC

The basic characteristics of a rugged, stable, and highly efficient polymeric stationary phase for normal-phase HPLC prepared by hydrolysis of porous monodisperse poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads have been studied and compared with those of bare Nucleosil silica and Nucleosil silica-diol. As a result of their overall chemical composition and the more than 10-fold larger surface coverage with hydroxyl groups, the polymer beads provide much higher retention of model solute molecules. In contrast to silica hydroxyls, all of the polymer surface diol groups are chemically equal and homogeneously distributed over all of the surface. In addition, they are less acidic than typical silanol functionalities. The exceptional selectivity of the polymeric column can be controlled by the composition of the mobile phase, as demonstrated with a broad spectrum of separations involving positional isomers of benzene derivatives, nonpolar isobutylene copolymers with minute composition differences, and hydrophilic poly(ethylene oxides) differing only in their chain length. Unlike silica phases, the properties of the polymeric stationary phrase are not affected by the presence of water in the mobile phase. As a result, repetitive gradient separations in eluents ranging in polarity from hexane through tetrahydrofuran to water can be easily accomplished.     

On the RF frequency dependence of the scattered spectral energy produced by intermittent contacts among elements of a target

A discussion of the factors that affect the RF frequency dependence of the spectral energy scattered by a target loaded at a single port by a time-varying impedance is presented. This frequency dependence is illustrated theoretically and experimentally for a centrally loaded dipole undergoing square-wave modulation by a reed switch.     

The effect of reaction conditions on the oxidation of veratryl alcohol catalyzed by cobalt salen-complexes

Cobalt salen-type [salen=N,N′-bis(salicylidene)ethylenediamine] complexes 1–6 were studied as catalysts for dioxygen activation in the oxidation of veratryl alcohol in basic aqueous conditions. The complexes Co(salen) (1), Co(CH₃salen) (2) [CH₃salen=N,N′-bis(methylsalicylidene)ethylenediamine], Co(4OHsalen) (3) [4OHsalen=N,N′-bis(4-hydroxosalicylidene)ethylenediamine], Co(sulfosalen) (4) [sulfosalen=N,N′-bis(5-sulfonatosalicylidene)ethylenediamine], Co(acacen) (5) [acacen=N,N′-bis(acetylacetone)ethylenediamine) and Co(N-Me-salpr) (6) [N-Me-salpr=bis(salicylideniminato-3-propyl)methylamine] were chosen to examine the influence of ligand structure on the catalytic activity. The effect of reaction conditions on the oxidation of veratryl alcohol was studied by varying temperature, pH, time or the nature and amount of the axial base needed to enhance the activity of complexes 1–5. The catalytic behaviour of the studied complexes was shown to be very depended on the applied conditions and distinct differences could be observed among the complexes. In all reactions, veratraldehyde was the only product observed. The unsubstituted complex 1 was the most efficient catalyst in the studied system achieving turnover numbers of up to 28 at 80 °C and pH 12.5.     

基于Matlab的RLC二阶电路零输入响应的研究

应用Matalb软件对RLC串联放电二阶电路的零输入响应进行了深入分析，给出了在3种情况下脉冲放电电流峰值im与R、L、C等参数的函数关系，用计算和绘图方法证明了在两种情况下不同形式的im=f(R、L、C）及i=f(t)、uc=f(t）等函数式的一致性，介绍了用能量平衡求该电路im值的方法。