A novel and simple method for finding the heterogeneity of adsorbents on the basis of adsorption kinetic data

The heterogeneity of adsorbent was characterized by a novel and simple method that uses adsorption kinetic data from solution. On the basis of different simulated adsorption kinetic data for heterogeneous adsorbents with two different adsorption sites, it was found that there is a deviation from linearity in pseudo-second-order adsorption kinetic models. The patterns of obtained diagrams (t/qt vs t) shows five main classes of adsorption. On the basis of this novel and simple method it is possible to show that the surface of adsorbents is homogeneous or heterogeneous, and in the case of heterogeneous surfaces it is possible to find the differences between adsorption sites. For finding kinetic constants of adsorption on heterogeneous surfaces with two different sites, a new equation was presented and called the two-site pseudo-second-order (TS-PSO) model. Finally, some experimental kinetic data of adsorption were analyzed by the new method.     

Synthesizing UHMWPE Using Ziegler-Natta Catalyst System of MgCl2(ethoxide type)/ TiCl4/tri-isobutylaluminum

Summery: A Ziegler-Natta catalyst of MgCl₂ (ethoxide type)/TiCl₄ has been synthesized. In order to obtain ultra high molecular weight polyethylene (UHMWPE) tri-isobutylaluminum which is less active to chain transfer was used as cocatalyst. Slurry polymerization was carried out for the polymerization of ethylene while, dilute solution viscometry was performed for the viscosity average molecular weight (Mv) measurement. The effect of [Al]/[Ti] molar ratio, temperature, monomer pressure and polymerization time on the Mv and productivity of the catalyst have been investigated. The results showed increasing [Al]/[Ti] ratio in the range of 78–117, decreased the Mv of the obtained polymer from 7.8 × 10⁶ to 3.7 × 10⁶ however, further increase of the ratio, resulted in decreased of by much slower rate up to [Al]/[Ti] = 588. The higher pressure in the range of 1–7 bars showed the higher the Mv of the polymer obtained, while increasing temperature in the range of 50 to 90 °C decreased the Mv from 9.3 × 10⁶ to 3.7 × 10⁶. The Mv rapidly increase with polymerization time in the first 15 minutes of the reaction, this increase was slowly up to the end of the reaction (120 min). Increasing [Al]/[Ti] ratio raised productivity of the catalyst in the range studied. Rising reaction temperature from 50 to 75 °C increased the productivity of the catalyst however, further increase in the temperature up to the 90 °C decreased activity of the catalyst. Monomer pressure in the range 1 to 7 bars yields higher productivity of the catalyst. Also by varying polymerization conditions synthesizing of UHMWPE with Mv in the range of 3 × 10⁶ to 9 × 10⁶ was feasible.     

Laser ultrasonic receivers based on organic photorefractive polymer composites

We present two laser ultrasonic receivers based on organic photorefractive polymer composites with 2-[4-bis(2-methoxyethyl)aminobenzylidene]malononitrile (AODCST) or 2-dicyanomethylen-3-cyano-5,5-dimethyl-4-(4′-dihexylaminophenyl)-2,5-dihydrofuran nonlinear optical chromophores. Experimental results show sensitivities of the ultrasonic receivers of ~9.5 × 10^?8 nm (W/Hz)^0.5 for both composites, and a faster response time (~60 ms) for the AODCST-based laser ultrasonic receiver. We show that such LUS detectors are highly suitable for contactless thickness measurements of aluminum, steel sheets and defect detection with an accuracy of 100 μm.     

Preparation,heat treatment and photoluminescence properties of V-doped ZnO–SiO2–B2O3 glasses

Four glasses in ZnO–SiO₂–B₂O₃ ternary system were prepared by the melt quenching method with the objective of optimizing sub-nanosecond emission over the UV region of zinc borosilicate glasses used in superfast scintillators. The effect of vanadium addition and heat treatment on phase formation, microstructure and photoluminescence properties of the glasses was characterized by means of DTA, XRD, SEM and fluorescence spectrophotometer. Vanadium contributed to the near-band-edge emission in two ways, by introducing donor levels in the energy band of ZnO particles and by facilitating the precipitation of ZnO and willemite crystals. Furthermore, nucleation of willemite and zinc oxide phases, which are both the origins of the intense emission bands in the UV region, was facilitated with increasing either the time or temperature of heat treatments. Photoluminescence spectra showed the elimination of the visible emission band which is favorable in scintillating glasses.     

The numerical and experimental study of photon diffusion inside biological tissue using boundary integral method

In this study, the diffusion of photons in turbid media, like biological tissue has been studied. Due to scattering and absorption of photons in such media, the study of photon propagation in biological tissue is complicated. The several numerical methods have been presented to simulate the behavior of diffused photons. Recently, Boundary Integral Method (BIM) has been offered to simulate photon migration inside biological tissues. This method has advantage, e.g. lower computational time in compared with other numerical methods. In this study, the accuracy and precision of BIM compares with another numerical method like Monte Carlo technique and finite difference method, and also the calculated results obtained by BIM and Monte Carlo method evaluate with measured results. Furthermore, the effects of scattering and absorption coefficient of tissue on the measured signal are studied.     

A new modification of false position method based on homotopy analysis method

A new modification of false position method for solving nonlinear equations is presented by applying homotopy analysis method （HAM）. Some numerical illustrations are given to show the efficiency of algorithm.     

基于同伦分析方法的一种改进的试位法

应用同伦分析方法,提出了一种求解非线性方程改进的试位法．给出的一些数值例证显示了该运算法则的有效性．