INTEGRAL EQUATION APPEOACH FOZ SIHULATION-OF - HEAT AND MASS TRANSFER PROCESSES

An integral equation approach was recommended for modelling and simulation of heat and mass transfer processes. It was shown that several mixing models that have been dealt with up to now dlfferently, can be unified in a single integral equation. An effective numerical method was developed for the solution of non-linear integral equation. A construction method for the source and kernel functions were lntroduced in connection with the simulation and control of heat treatlng processes taking place in tunnel kiln and heat and mass transfer processes in tunnel dryer.

We have concluded that our method is advantageous If the slmulated process 1s slgnlficantly affected by the degree of mixing and/or the kernel function can be determined by direct measurement of the streaming phases including feedback, recirculation etc.     

Hydroxyalkylation of barbituric acid. III. Product analysis and reaction pathway

Polyetherols containing a thermally stable pyrimidine ring were obtained upon the reaction of hydroxymethyl derivatives of barbituric acid with an excess of ethylene or propylene oxide. The reaction was monitored by ¹H‐NMR and IR spectroscopy for the systems with variable starting molar ratios of reagents. We found that formaldehyde rearranged from N‐hydroxymethyl and oxymethylene bridges into the end of the polyetherol chain during the reaction. Simultaneously, the O‐hydroxymethyl groups underwent blocking by oxirane. The structures of the polyetherols was deduced on the basis of the course of the reaction and the analytical data. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Depth Dependence of Nanoindentation Pile-Up Patterns in Copper Single Crystals

A study of the dependence of nanoindentation pile-up patterns on the indentation load and crystallographic orientation is presented. Three different orientations—(001), (011), and (111)—of single crystal copper were investigated. Experiments were conducted on a CSM ultra-nanoindentation tester using a Berkovich tip. The topographic images were obtained using an atomic force microscope. The evolution of pile-up patterns with different applied loads was observed. The results show that for applied loads equal to 0.45 mN and smaller the pile-up patterns do not depend on the crystallographic orientation of the indented surface; instead, they depend on the tip’s geometry. On the other hand, in the case of indentation loads bigger than 2 mN, pile-up patterns on the surfaces of (001)-, (011)-, and (111)-oriented single crystals have fourfold, twofold, and sixfold (or threefold) symmetry, respectively. An intermediate state was also reported. Furthermore, a detailed analysis of residual impressions with maximal applied loads equal to 2 mN and bigger reveals that both pile-up and sink-in patterns are present.     

An overdeterrnined two-dimensional transient inverse heat conduction problem

The method of solving the two-dimensional nonlinear inverse heat conduction problems is presented. The time- and space temperature distribution inside a solid and heat transfer coefficient distribution on the boundary of the solid is determined based on the temperature histories measured in several selected inside locations. The problem is overdetermined because the number of measuring points is higher than the number of calculated parameters (components of heat transfer coefficient).     

Heterogenization of 12-tungstophosphoric acid on stabilized zeolite Y

Topics in Catalysis - 12-tungstophosphoric acid (PW12) has been supported on dealuminated zeolite Y, containing a secondary pore system with the predominant pore radii of 15 Å. The interaction...     

An integrated multichannel waveform generator for large-scale spatio-temporal stimulation of neural tissue

We present an ASIC designed for electrical stimulation of neural tissue using multielectrode arrays. The ASIC is foreseen for applications in systems that require simultaneous stimulation and recording of signals from various types of neural tissue, both in vitro and in vivo. The developed ASIC comprises 64 independent stimulation channels, which are capable to generate arbitrarily defined bipolar current or voltage waveforms, controlled in real time with time resolution of 12.5 μs and amplitude resolution of 7 bits. The amplitude range of output signal can be scaled over a very wide range, which ensures compatibility with various electrode arrays of different size and geometry. Each channel is also equipped with a stimulation artifact suppressor controlled in real time, which reduces the dead time of the system after each stimulation pulse.     

Wettability Studies of Pb-Free Soldering Materials

For Pb-free soldering materials, two main substitutes are currently being considered, consisting of Sn–Ag and Sn–Ag–Cu eutectics, both with melting points higher than that of the Sn–Pb eutectic. Therefore, both will require higher soldering temperatures for industrial applications. Also, both eutectics have a higher surface tension than the Sn–Pb eutectic, requiring wettability studies on adding Bi, Sb, and In to the eutectics to decrease the melting points and surface tension. The experimental results for the surface tension were compared with thermodynamic modeling by Butler’s method and were used to create the SURDAT database, which also includes densities for pure metals, binary, ternary, quaternary, and quinary alloys. To model the surface tension, excess Gibbs energies of the molten components were taken from the ADAMIS database. For the case of the Ag–Sn system, enthalpies of formation of Ag₃Sn from solution calorimetry were used for checking optimized thermodynamic parameters. In the study of Sn–Ag–Cu–Bi–Sb liquid alloys, the range of possible Bi compositions for practical applications has been used to formulate a generalized metric of wettability, which was checked by measurements of the influence of In on the Sn–Ag–Cu system.     

Phenol Removal through Chemical Oxidation using Fenton Reagent

In this study, phenol, aromatic, and non‐biodegradable organic matter were investigated and found to be removed from the model solution through chemical oxidation using Fenton reagent. The effects of the initial phenol concentration, hydrogen peroxide, and ferrous sulfate concentrations on the removal efficiency were investigated. Performance of the chemical oxidation process was monitored with phenol and COD (Chemical Oxygen Demand) analyses. In the experimental studies, phenol removal of over 98 % and COD removal of nearly 70 % were achieved. The optimum conditions for Fenton reaction both for initial phenol concentrations of 200 and 500 mg/L were found at a ratio [Fe²⁺]/[H₂O₂] (mol/mol) equal to 0.11. According to the results, chemical oxidation using Fenton reagent was found to be too effective, especially for phenol removal. However, this method has limited removal efficiency for COD.