Preliminary study of a radiantly heated fluidized bed for the production of high purity silicon

The preparation of very pure silicon from silane (SIH4) using radiant heating of the hot silicon particles of a fluidized bed is discussed. The fraction of electrical energy supplied to the heater which is actually absorbed by the particles and the heat transfer coefficient between the hot bed and the cool distributor plate were investigated. The experimental design is presented and the results of the study are summarized

A study of the relationships between selected perceptual-motor behaviors and: achievement in reading; achievement in mathematics; classroom behavior; academic self-concept; and academic motivation for first and third grade boys and girls

This study investigated the relationships between selected perceptual-motor behaviors and the following: achievement in reading, achievement in mathematics, academic self-concept, academic motivation and classroom behavior. This investigation was designed to explore the suggestion of Newell Kephart that there is a relationship between perceptual-motor behavior and school success, and to provide useful information for future research projects which could lead to the development of training programs. The subjects for this study consisted of 84 students, 49 girls and 35 boys, from the first and third grades at Lincoln School, Corvallis, Oregon. The following tests were administered to all subjects: the Metropolitan Achievement Test, to assess achievement in reading and mathematics, the Self- Concept and Motivation Inventory, to assess academic self-concept and academic motivation, the Devereux Elementary Behavior Rating Scale, to assess classroom behavior, and six sub-tests from the Purdue Perceptual-Motor Survey, to assess the perceptual-motor behaviors of balance, jumping, angels-in-the-snow, obstacle course, chalkboard and identification of body parts. The data from this study were analysed in the following manner: Using the Pearson product moment coefficient of correlation, "r" values were determined showing the relationship between the scores obtained on the six sub-tests of the Purdue Perceptual-Motor Survey and the scores obtained on the other tests administered; t-tests were run to determine the differences in the "r" values obtained for boys and girls and first and third grade subjects; and tests of significance were run for each correlation coefficient obtained. The t-test analysis revealed no significant difference between the "r" values for boys and the "r" values for girls in any of the comparisons. A significant difference was found between the "r" values for first and third grade subjects in the correlation between perceptual-motor behavior and academic motivation. Comparisons were not made between first and third grade subjects in mathematics and reading correlations because different test batteries were administered and were not comparable. Correlation coefficients were found between first grade reading scores and the following perceptual-motor scores: the total perceptual-motor behavior score p < .001, angels-in-the-snow p < .001, jumping p < .001, balance p < .001, identification of body parts p < .05, and chalkboard p < .10. Correlation coefficients were found between first grade mathematics scores and the following perceptual-motor scores: the total perceptual-motor score p < .001, jumping p < .001, balance p < .001, angels-in-the-snow p < .001 and chalkboard p < .10. Correlation coefficients were found between third grade reading scores and the following perceptual-motor scores: the total perceptual-motor score p < .01, balance p < .05, jumping p < .01, identification of body parts p < .01, obstacle course p < .10 and chalkboard p < .10. Correlation coefficients were found between third grade mathematics scores and the following perceptual-motor scores: the total perceptual-motor score p < .001, balance p < .01, jumping p < .01, identification of body parts p < .01, obstacle course p < .05 and chalkboard p < .05. Correlation coefficients were found between classroom behavior and the following perceptual-motor scores: the total perceptual-motor score p < .01, balance p < .05, jumping p < .10, identification of body parts p < .001, obstacle course p < .10 and chalkboard p < .05. None of the correlation coefficients between perceptual-motor behavior and academic self concept were found to be significant at the significance levels of .10, .05, .01 and .001. The findings for the relationship between academic motivation and perceptual-motor behavior were inconclusive. This study has identified perceptual-motor behaviors which are definitely related to achievement in reading, achievement in mathematics and classroom behavior. These findings are consistent with Kephart's suggestion that perceptual-motor development is related to school success. By identifying the specific perceptual-motor behaviors which are related to school success the findings of this study have provided useful data for the design of experimental research projects and the development of perceptual-motor training programs. Further research is indicated to explore the relationships between self-concept, motivation and perceptual-motor behaviors

Global Strong Solutions for a Class of Heterogeneous Catalysis Models

We consider a mathematical model for heterogeneous catalysis in a finite three-dimensional pore of cylinder-like geometry, with the lateral walls acting as a catalytic surface. The system under consideration consists of a diffusion-advection system inside the bulk phase and a reaction-diffusion-sorption system modeling the processes on the catalytic wall and the exchange between bulk and surface. We assume Fickian diffusion with constant coefficients, sorption kinetics with linear growth bound and a network of chemical reactions which possesses a certain triangular structure. Our main result gives sufficient conditions for the existence of a unique global strong $L^2$-solution to this model, thereby extending by now classical results on reaction-diffusion systems to the more complicated case of heterogeneous catalysis.Comment: 30 page

Melt-Mixing by Novel Pitched-Tip Kneading Disks in a Co-Rotating Twin-Screw Extruder

Melt-mixing in twin-screw extruders is a key process in the development of polymer composites. Quantifying the mixing performance of kneading elements based on their internal physical processes is a challenging problem. We discuss melt-mixing by novel kneading elements called "pitched-tip kneading disk (ptKD)". The disk-stagger angle and tip angle are the main geometric parameters of the ptKDs. We investigated four typical arrangements of the ptKDs, which are forward and backward disk-staggers combined with forward and backward tips. Numerical simulations under a certain feed rate and screw revolution speed were performed, and the mixing process was investigated using Lagrangian statistics. It was found that the four types had different mixing characteristics, and their mixing processes were explained by the coupling effect of drag flow with the disk staggering and pitched-tip and pressure flows, which are controlled by operational conditions. The use of a pitched-tip effectively to controls the balance of the pressurization and mixing ability

Measurement of adsorption of a single component from the liquid phase : modelling investigation and sensitivity analysis

In this work, we consider an alternative approach for the measurement of adsorption from the liquid phase. Consider a mixture consisting of a non-adsorbed component (B) and an adsorbed component (A) present at some low concentration. Initially, a feed of component B only flows through a column packed with an adsorbent. Then, the feed is switched to the mixture of A and B. As soon as the mixture enters the column, there will be a reduction in the outlet flow rate as component A leaves the liquid phase and passes into the adsorbed phase. There are three stages to this work. The first is to develop overall and component balances to show how the amount adsorbed of component A can be determined from the variation in the column outlet flow rate. The second is to determine the actual variation in the column outlet flow rate for both plug flow and axial-dispersed plug flow. The final stage is to consider the suitability of a gravity-fed system to deliver the feed to the column. An analysis of the results shows that the experimental arrangement should be able to accurately monitor adsorption from the liquid phase where the mass fraction of the solute is of the order of 1%: the limiting experimental factor is how constant the volumetric flow rate of the liquid feed can be maintained

Self-similarity of fluid residence time statistics in a turbulent round jet

Fluid residence time is a key concept in the understanding and design of chemically reacting flows. In order to investigate how turbulent mixing affects the residence time distribution within a flow, this study examines statistics of fluid residence time from a direct numerical simulation (DNS) of a statistically stationary turbulent round jet with a jet Reynolds number of 7290. The residence time distribution in the flow is characterised by solving transport equations for the residence time of the jet fluid and for the jet fluid mass fraction. The product of the jet fluid residence time and the jet fluid mass fraction, referred to as the mass-weighted stream age, gives a quantity that has stationary statistics in the turbulent jet. Based on the observation that the statistics of the mass fraction and velocity are self-similar downstream of an initial development region, the transport equation for the jet fluid residence time is used to derive a model describing a self-similar profile for the mean of the mass-weighted stream age. The self-similar profile predicted is dependent on, but different from, the self-similar profiles for the mass fraction and the axial velocity. The DNS data confirm that the first four moments and the shape of the one-point probability density function of mass-weighted stream age are indeed self-similar, and that the model derived for the mean mass-weighted stream-age profile provides a useful approximation. Using the self-similar form of the moments and probability density functions presented it is therefore possible to estimate the local residence time distribution in a wide range of practical situations in which fluid is introduced by a high-Reynolds-number jet of fluid