Processing of Thermoplastic Composites Using a Powder Slurry Technique. I. Impregnation and Preheating

The success of thermoplastic matrix composites depends upon the development of economical methods of impregnation. The purpose of this work was to develop and understand an economical impregnation procedure using a slurry based powder technology. An impregnation and preheating line consisting of a fiber tensioner, a slurry bath, a drying heater, a coating heater, and a fiber winder was used to make resin coated fibers. The influence of the process parameters on the impregnation, preheating, coating, and consolidation were studied. Part I of this paper presents the experimental investigation of the impregnation and preheating stages of the process together with a preheating model. Luikov's coupled equations of heat and mass transfer were used to model the heating and drying of the tow in the preheater. The predictions of the preheating and drying model are compared to the experimentally obtained results.     

Performance posting, goal setting, and activity-contingent praise as applied to a university hockey team.

Rate of legal body checking (hit rate) was targeted for change for each of two consecutive seasons for a university hockey team that had a chronic losing record. Following baseline recording (A), the interventions of publicly posted individual feedback (B), goal setting (C), and praise (D) were successively introduced "on-the-baseline" using a components-analysis research strategy. An analogous design and procedure was used the following season, with the exception that more intensive training was given to the coach on the delivery of praise. Overall, the mean hit rate increased 82% (excluding the highly talented senior players who initiated the first project application) and 141% (no exclusions), respectively, for the 2 years. Moreover, with the single exception of the praise treatment of the first year, increments in hit rate occurred with the onset and tenure of each intervention (most ps?     

Tetragonal → twinned hexagonal crystal phase transformation in polybutene-1

The spontaneous transformation of the metastable (Form II) tetragonal crystals into the stable twinned hexagonal (Form I) crystals in polybutene-1 was studied using several techniques. The mechanical properties of the heat moulded material undergo significant changes in the process and the crystalline melting point increases from 112 to 128‡ C. Results from an Avrami analysis suggest the nucleation of the stable crystalline phase occurs shortly after crystallization from the melt and the subsequent growth of the nuclei follows a rod-like geometry. Transmission electron microscopy of melt-grown thin films shows that nucleation occurs at random positions within a spherulite and growth propagates along the radially oriented fibrillar crystals. As a result of multiple nucleation, each tetragonal crystal generates several twinned hexagonal crystallites with different crystallographic orientations. Besides exhibiting multiple nucleation within each individual tetragonal crystal, solution-grown single crystals also reveal twisting of the crystal lattice about thec-axis. The information obtained shows that residual stresses present in the material do not appear essential for the nucleation of the stable phase. Current concepts of the transformation mechanism are examined.     

Numerical Model for Unsteady Open Channel Flow in C

Abstract: This paper addresses the application of C languagees in developing hydraulic engineering software and depicts the implementation and the rigorous verification of a gererally applicable finite difference numerical model, tailored for use on the IBM PC/XT or PC/AT personal computers, for simulation of unsteady open channel flow. The program is written in the C language, compiling and executing under the integrated program environment TURBO C version 2.0. The various advantages and limitations of employing the TERBO C environment in developing hydraulic engineering software are also presented thoroughly. In the development of the mathematical model, apart from the simplified channel tests where analytical results are available. The program's successful application provides confidence for its capablity as a predictive tool in situations involving complex bathymetry and/or nonlinear bottom frictional effects.     

Subject variables and performance on the Halstead Neuropsychological Test Battery: A multivariate analysis.

Administered the Halstead Neuropsychological Test Battery for Adults (HNTB) to 288 15–52 yr old (mean WAIS IQ 84) Ss with seizure disorder and examined age, sex, SES, handedness, and educational level as predictor variables. MANOVA showed considerable variability in the magnitude and nature of the relationship between predictor variables and measures of the HNTB. It is suggested that the influence of subject variables (especially sex) should be considered in the clinical-decision process involving neuropsychological evaluations so that adjusted cutoff scores and norms used are appropriate. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decision-theoretic utility analysis applied to employee separations and acquisitions.

Describes a decision-theoretic utility model that outlines the consequences of 3 types of employee movement: repeated acquisitions without separations, repeated unreplaced separations over time, and repeated separations over time that are replaced with new employees. In addition to a conceptual and algebraic model development, a computer algorithm is developed and used to provide a numerical simulation. Results suggest that decisions about employee separations can substantially affect the utility of human resources. (56 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of the PHOCI™ data integrated video sensor technology

In this article, we report the characterization results of two data integrated video sensors designed by Clifton Labs, Inc. A data integrated video sensor consists of an array of photodetectors that each provide both an analog (video) and digital (data) output based on the amount of incident light on the detector. Video capture occurs using a simple sample-and-hold circuit. In the first sensor, data capture occurs using an externally supplied voltage to provide a threshold that is used to determine if a value is a ?1’ or ?0’. In the second sensor, another sample-and-hold circuit is use to capture data values. The first design is characterized for output response at a given sample frequency for the video portion. The maximum data rate and optical response at a given data threshold are defined for the digital circuitry. Next, the digital and analog output values of the second chip are correlated to the incident optical power and the sample time used to capture the data. The results of these tests provide insight into the operation of the two designs and confirm simulation results used in the design of the circuits.     

Individual differences in the efficiency of word recognition.

Examined the hypothesis that the attentional demands of word recognition covary with other measures of reading efficiency. Individual differences in efficiency were indexed by (1) speed and accuracy of lexical access, (2) obligatory activation of phonological codes, and (3) working memory capacity. The attentional demands of word recognition were measured with a dual-task technique. Ss performed naming and probe-detection tasks separately (single task) and in combination (dual task). The results showed that single-task to dual-task decrements in performance on the naming and probe tasks were predicted by measures of the speed and accuracy of lexical access, obligatory activation of phonological codes, and efficiency of working memory. These findings provide support for the widespread assumption that the attentional demands of basic reading processes are a source of individual differences in reading skill. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wear and friction of aramid fibre and PTFE filled composites

The most widespread reinforcements and lubricants used for wear applications include polytetrafluoroethylene (PTFE), silicone, glass fibre, carbon fibre and aramid fibre. Of these, PTFE and aramid fibre play a key role in the production and performance of a huge variety of seal components. This article describes work undertaken at LNP Engineering Plastics to optimise the aramid fibre loadings in systems with and without PTFE. Mechanical properties, tribological performance and cost were all considered, and in addition the transfer film formed when these composites are wearing was examined.