Tensile testing and fracture mechanism analysis of polyvinyl alcohol nanofibrous webs

A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs.     

Numerical Simulation of Waveguides of Arbitrary Cross-Section

Finite difference equations are derived for the simulation of dielectric waveguides using an H_z-E_z formulation defined on a nonuniform triangular grid. The resulting equations may be solved as a banded eigenproblem for waveguide structures of arbitrary shape composed of regions of piecewise constant isotropic dielectric, and all transverse fields then computed from the solutions. Benchmark comparisons are presented for problems with analytic solutions, as well as a sample calculation of the propagation loss of a hollow Bragg fiber.     

MANAGEMENT SUPPORT SYSTEM AT PROMUS Using IT to Ensure Customer Satisfaction

Information-based organizations are structured to function with as small and efficient a staff as possible. To this end, executives at The Promus Companies are using IT to spread decision-making authority and responsibility for customer satisfaction and customer service throughout the organization.     

Microprocessor-Based Control of an Ion Beam Deposition System

A microprocessor-based system with 32 A/D, 24 D/A, and 16 ac load controllers, has been designed and built to monitor and control an ion beam thin-film deposition system. The A/D and D/A channels have electrical isolation of 7.5 kV between channels and between input and output. The microprocessor system keeps the ion beam deposition parameters stable for extended periods of operation and it is proposed as a means to greatly simplify switching from one deposition species to another to grow thin multilayer or alloy films.     

Finite-element grid improvement by minimization of stiffness matrix trace

A new and simple method of finite-element grid improvement is presented. The objective is to improve the accuracy of the analysis. The procedure is based on a minimization of the trace of the stiffness matrix. For a broad class of problems this minimization is seen to be equivalent to minimizing the potential energy. The method is illustrated with the classical tapered bar problem examined earlier by Prager and Masur. Identical results are obtained.     

Multiple perspectives of rejected, neglected, and accepted children: Relation between sociometric status and behavioral characteristics.

Hypothesized, on the basis of findings from several studies, that rejected children are more disruptive, aggressive, and socially inappropriate than are their classmates. Three groups of 39 rejected, 29 neglected, and 39 accepted children were randomly selected from 282 boys and 210 girls who were identified separately on the basis of sociometric scores for 492 children in Grades 3–6. The 3 groups were compared using multiple analysis of variance (MANOVA) on measures from 4 domains: peer behavioral attributions, teacher ratings, analog assertiveness task, and self-evaluation. Rejected Ss were clearly distinguished from their same-sex neglected and accepted classmates and were described by teachers and peers as aggressive, disruptive and inattentive. Neglected Ss were only marginally discriminable from same-sex accepted children. Neither neglected nor rejected Ss were differentiated from accepted Ss with respect to observed assertiveness and self-ratings of shyness, unhappiness, and feeling unaccepted. The results replicate previous findings for rejected children. Currently, there is not sufficient justification to consider the group of socially neglected children as a clinical category. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Studies of elemental distributions within discrete coal macerals: Use of secondary ion mass spectrometry and X-ray photoelectron spectroscopy

Secondary ion mass spectrometry has been used to measure qualitatively the distributions of many trace and minor elements within some well-characterized coal macerals: vitrinite, fusinite and exinite. Complementary information was obtained by using X-ray photoelectron spectroscopy. Within the vitrinite specimens studied, a widely-dispersed largely inorganic aluminosilicate phase was identified, which contained a number of other trace elements. By contrast, within the organic-rich phase of this macerai, titanium was detected in a very even distribution; this suggests that some titanium may be bonded in an organic complex. The fusinite was shown to contain elevated concentrations of calcium, magnesium and fluorine, dispersed over a large portion of the maceral. The high fluorine content could be identified as an organo-fluoro compound using XPS. Exinite was found to contain lower concentrations of most elements, compared to other macerals. The organic composition of this maceral was significantly different from that of surrounding macerals; this could be seen from the enhanced emission of the C₂H₂-secondary ion and images of this ion thus clearly outlined the position of such macerals.     

Creating a Student Centered Learning Environment at the University of Denver

A team of faculty members at the University of Denver changed the learning environment in key courses in the Department of Engineering from predominately teacher centered to student centered. Through this funded project new grading methods were implemented, classrooms were renovated and wired with studio layouts to facilitate learning, the Engineering Circuits Laboratory was rewired and instrumented for automated data acquisition and reporting, and two new pedagogical approaches were developed. At the onset of the project, six goals were established related to student learning. The introduction of industry standard hardware and software provided students with unprecedented hands‐on experience and project related activities stimulated faculty innovations in other current and future courses. Assessment results indicate that the new grading system improved the clarity of expectations for students before assignments were given resulting in increased reported motivation for learning in many courses. Even though course GPAs did not always reflect higher achievement on graded work, faculty members firmly believe that deeper understanding was achieved because more complex material was assimilated.     

Multiobjective evaluation of advanced manufacturing system technology investments with risk

Advanced manufacturing system technologies are difficult to evaluate using ordinary financial measures owing to the presence of risk and significant intangible factors. In this paper a methodology is proposed that quantifies financial, strategic, and tactical attributes of each alternative. Attribute values are denned for each period of project life. Both project life and attributes are treated as random variables. Attributes are discounted to the current time and the multiple objectives are combined by composite programming. The distribution of the combined objective is estimated. The procedure is demonstrated on an actual case study.