Evaporation induced self-assembly of zeolite A micropatterns due to the stick-slip dynamics of contact line

In this study, a new surfactant-solvent system was described for the preparation of periodic stripe patterns of zeolite A on solid substrates. The evaporation induced self-assembly of zeolite A particles was due to the stick-slip dynamics of the three-phase contact line of the colloid solutions in acetone containing 10% (v/v) poly(dimethylsiloxane) (PDMS) fluid (2 cst.). In order to investigate the possible effects of particle size and the particle concentration on the stick-slip dynamics, three types of zeolite A samples with different particle sizes (zeolite A-I: 250-500 nm, zeolite A-II: 100-250 nm and zeolite A-III: 0-100 nm) were utilized to prepare 0.007-0.06% (w/v) colloidal dispersions. Zeolite A micropatterns were self-assembled on the surface of glass, high density polyethylene (HDPE) and poly(tetrafluoroethylene) (PTFE) substrates, which were placed vertically inside the colloid solutions and held against the wall of the cylindrical vial during the evaporation of acetone. The stripe patterns of zeolite A particles were analyzed with field emission scanning electron microscope (FE-SEM) and optical microscope. The widths of microstripes and the distance between the stripes were found as 2-20 μm and 40-60 μm respectively depending on the particle concentration. By using the stick-slip dynamics of colloids, the linear micropatterns of zeolite A nanocrystals were prepared with low cost and low energy.     

基于S2A6000存储的新闻制播网络安全设计

从分析S2A6000新闻制播网系统特点,拓扑结构入手,完整总结了S2A6000存储的新闻制播网络安全设计与安全措施。     

Optimal estimation of parameters of dynamical systems by neural network collocation method

In this paper we propose a new method to estimate parameters of a dynamical system from observation data on the basis of a neural network collocation method. We construct an object function consisting of squared residuals of dynamical model equations at collocation points and squared deviations of the observations from their corresponding computed values. The neural network is then trained by optimizing the object function.The proposed method is demonstrated by performing several numerical experiments for the optimal estimates of parameters for two different nonlinear systems. Firstly, we consider the weakly and highly nonlinear cases of the Lorenz model and apply the method to estimate the optimum values of parameters for the two cases under various conditions. Then we apply it to estimate the parameters of one-dimensional oscillator with nonlinear damping and restoring terms representing the nonlinear ship roll motion under various conditions. Satisfactory results have been obtained for both the problems.     

Tribological behavior of PTFE nanocomposite films reinforced with carbon nanoparticles

Carbon-based nanoparticles synthesized by heat treatment of nanodiamond in the temperature range of 1000–1900 °C were added to PTFE film to investigate the structural effect of the carbon particles on the tribological properties of PTFE composite film. Carbon-based nanoparticles were prepared by milling with micron sized beads in chemically treated water before their addition to PTFE film. The wear and frictional properties of PTFE nanocomposite film were measured by the ball on plate type wear test. The wear resistance of PTFE film was found to be enhanced by the addition of 2 wt% of carbon nanoparticles. The wear coefficient of PTFE film was decreased from 16.2 to 3.5 × 10⁻⁶ mm³/N m by the addition of carbon-based nanoparticles heat-treated at 1000 °C. Increasing the heating temperature of the nanodiamonds caused the extent of aggregation and particle size to increase. The wear resistance of PTFE nanocomposite film was enhanced by the addition of nanodiamonds heat-treated at 1000 °C, but decreased when the heat treatment temperature of carbon nanoparticles was further increased. Tribological behavior of PTFE nanocomposite films depending on the types of carbon nanoparticles were explained based on the structural, physical and chemical modification of carbon nanoparticles.     

Study of the effective parameters on mechanical and electrical properties of carbon black filled PP/PA6 microfibrillar composites

In this study the electrical and mechanical properties of microfibrillar polypropylene (PP)/polyamide6 (PA6) blend filled with super conductive carbon black (CB) have been investigated. In situ microfibrillar PP/PA6 composites filled with CB are produced using a single screw extruder equipped with a spinneret. Glycidyl methacrylate (GMA) grafted polypropylene (PP-g-GMA) is used as the compatibilizer. To investigate the effects of extensional flow on the microstructure, electrical and mechanical properties, three adaptors with various convergence angles were designed, prepared and applied between the extruder and the spinneret. To optimize the effects of processing and material parameters on the electrical and mechanical properties, the Taguchi method of experimental design is used. Material and processing factors which are studied include: concentration of PA6, compatibilizer level, CB concentration, drawing speed of melt spinning line, adaptor angle, order of mixing and temperature profile along the extruder. The results show an increase in DC conductivity of up to 10¹¹ times in comparison with pure PA6, by increasing the concentration of CB, drawing speed, adaptor angle and optimizing other parameters. By optimizing processing and material factors studied here, strength of microfibrillar structured composites is increased of up to 80% in comparison to pure PP.     

Analytical modeling and experimental study of tensile strength of asphalt concrete composite at low temperatures

In this study, analytical modeling of the tensile strength of hot-mix asphalt (HMA) mixtures at low temperatures was developed. To do this, HMA mixtures were treated as a two-phase composite material with aggregates (coarse and fine) dispersed in an asphalt mastic matrix. A two-phase composite model, which was similar to Papanicolaou and Bakos's [J. Reinforced Plast. Compos. 11 (1992) 104] model with a particle embedded in an infinite matrix, was proposed. Unlike Papanicolaou and Bakos's model, an axial stress was introduced to the fiber end to consider the load transferred from the asphalt mastic the aggregate. Efforts were also made to consider the effect of aggregate gradation, asphalt mastic degradation, and interfacial damage between the aggregates and asphalt mastic matrix on the tensile strength of the HMA mixtures. Experimental investigations were conducted to validate the developed theoretical relations. A reasonable agreement was found between the predicted tensile strength and the experimental results at low temperatures. Parameters affecting the tensile strength of asphalt mixtures were discussed based on the calculated results.     

The oxidation of two ternary Ni-Cu-10 at.% Al alloys in 1 atm of pure O2 at 800-900 °C

The oxidation of the ternary alloys Ni-45Cu-10Al and Ni-30Cu-10Al has been studied at 800-900 °C under 1 atm O₂. The presence of 10 at.% Al reduces significantly the oxidation rate of the corresponding Cu-Ni alloys during the initial oxidation stages, even before the establishment of a complete Al₂O₃ layer. The weight of individual sample of the two ternary Ni-Cu-10Al alloys at 800 °C increases more rapidly than at 900 °C during the initial oxidation stage. As oxidation proceeds, the weight gain at 800 °C slows down to a degree that the total weight gain after 24 h oxidation at 800 °C is less than that at 900 °C. Due to a faster formation of the Al₂O₃ layer, which suppresses earlier the further oxidation of Cu and Ni, the external region of the scales grown on Ni-45Cu-10Al contain much less Cu and Ni oxides than those grown on Ni-30Cu-10Al. The transition from the internal oxidation to the selective external oxidation of the most reactive component Al in Ni-Cu-Al alloys is favored by higher values of the Al content, of temperature and of the Cu/Ni ratio.     

Design of the ECRH/ECCD Launcher System for HL-2A Tokamak

An ECRH/ECCD system with two 68GHz/500kW/1S gyrotrons will be built up in HL-2A tokamak. The location of the Gaussian beam waist is 580 mm away from the center of the plasmas and the beam radius is 37 mm at the center of the plasmas. Compared to the minor plasma radius （420 mm）, it is small enough for localized control. The launcher system covers a wide toroidal and poloidal steering range by the two steering plane mirrors. Therefore it is possible to explore the on- and off-axis heating over half of the plasma minor cross section and the co-current drive.     

Electrochemical noise analysis for estimation of corrosion rate of carbon steel in bicarbonate solution

We have investigated the electrochemical noise behavior of carbon steel in fully deaerated aqueous bicarbonate solutions, and discussed the optimum conditions of the noise analysis for estimating corrosion rate of the steel. Noise of the potential difference and of the short-circuit current between two identical steel coupons were successfully measured. The time-series noise patterns were transformed into frequency domain by fast Fourier transformation, and then their power spectrum densities (PSDs) at a frequency were determined to be compared with the corrosion rate. The PSDs of the potential and of the current varied with changing environmental factors of bicarbonate concentration, pH, and immersion time. The factors also controlled the corrosion rate of the steel. The PSDs were associated with the corrosion rate, and then it was found that the PSDs of the potential and of the current showed linear correlation with the corrosion rate in log-log scale. There was also linear relationship between the corrosion rate and a spectral noise resistance obtained from the PSDs of the potential and the current. The linearities of the three correlations were better at a lower analyzed frequency. Furthermore, the PSDs of the current and the noise resistance indicated more linear correlation with the corrosion rate than that of the potential. As the simplicity of the measurement system is additionally considered, it is concluded that the PSD of the current noise at an analyzed frequency of 3 mHz is the optimum conditions for estimating the corrosion rate from 10⁻² to 10⁰ A m⁻² in this study.     

Passivation and corrosion behaviours of cobalt and cobalt-chromium-molybdenum alloy

Passivation and corrosion behaviour of the cobalt and cobalt-base alloy Co30Cr6Mo was studied in a simulated physiological solution containing chloride and bicarbonate ions and with pH of 6.8. The oxido-reduction processes included solid state transformations occurring at the cobalt/electrolyte interface are interpreted using theories of surface electrochemistry. The dissolution of cobalt is significantly suppressed by alloying it with chromium and molybdenum, since the alloy exhibited “chromium like” passivity. The structural and protective properties of passive oxide films formed spontaneously at the open circuit potential or during the anodic polarization were studied using electrochemical impedance spectroscopy in the wide frequency range.