Novel Poly(vinyl alcohol)‐tetraethoxysilane hybrid matrix membranes as oxygen barriers

Novel type of membranes based on poly(vinyl alcohol) crosslinked with tetraethoxysilane have been prepared by solution casting and solvent‐evaporation method. The membranes thus formed were characterized by Fourier transform infrared spectroscopy (FTIR) to study the chemical interactions, X‐ray diffraction (XRD), and thermogravimetry (TGA) to investigate morphological and thermal properties. Membranes were prepared in two different thicknesses (30 and 55 μm) and used for measuring the oxygen permeability under varying feed pressures (maintaining the desired pressure differential across the membrane) in the range from 1 to 50 kg/cm² pressure. Oxygen permeability of the membranes ranged from 0.0091 to 1.6165 Barrer for 30 μm and 0.0305 to 0.1409 Barrer for 55‐μm thick membranes by increasing the feed pressures on the feed side. Except at 50 kg/cm² pressure, the observed oxygen permeability values are almost close to total permeability. Membranes of this study could be useful as oxygen barriers for applications in food packaging industries. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 273–278, 2007     

Molecular Transport of Organic Esters Into Fluoropolymer Membranes

The effects of different fluorine contents of the Du Pont VITON fluoropolymers have been studied in the presence of esters such as methyl acetoacetate, ethyl acetoacetate, methyl benzoate, ethyl benzoate, and 1-butyl acetate in the temperature interval of 25°–60°C. The sorption and diffusion of these liquids into the polymer membranes tend to deviate slightly from the Fickian mechanism; however, the diffusion data have been calculated from the Fickian model. It is suggested that the hindered chain segmental motion and the structural differences in the polymer membranes contribute to the overall sorption process, in addition to strictly thermodynamic considerations. The activation parameters for the transport processes have been estimated and the results are discussed in terms of the nature of polymer-solvent interactions.     

Magnetic ferrite/carbonized cotton fiber composites for improving electromagnetic absorption properties at gigahertz frequencies

Ferrite/carbon composited materials,especially the bio-derived composited materials possessing both environmental friendliness and outstanding microwave absorption performance,attract numerous attentions for solving the"electromagnetic problem"in the Gigahertz frequency range.In this work,we demonstrate a bio-derived ferrite/carbon material by compositing functional carbonized cotton fibers(CCFs)and Fe3O4 nanoparticles with optimized microwave-absorption properties.By adjusting the carbonization conditions systematically,the Fe3O4 loading contents and the microwave absorption properties can be varied simultaneously-and,indeed,optimized and tuned.The CCFs-Fe3O4 composites exhibited a minimum reflection-loss capacity RL(dB)of-56.8 dB at 10.9 GHz with a thickness of 1.67 mm,and its effective absorption bandwidth(RL(dB)＜-20 dB)was found to broaden to 7.1 GHz.Electromagnetic characterizations,coupled with microstructure analyses,revealed that the enhancement in microwave absorption was triggered by the different microstructures of CCFs-Fe3O4 composites-attributable to the different carbonization processes.These different conditions result in different amounts of Fe3O4 attachment sites and lead to the enhancement of dielectric polarization at localized microstructures.The present work of bio-derived ferrite/carbon materials has important implications in understanding structure-performance relationships in dielectric-magnetic materials,and,meanwhile,could well be extended to a microwave-absorber design approach.     

Pistol shooting accuracy as dependent on experience, eyes being opened and available viewing time

A study of the shooting accuracy of three groups of pistol shooters is reported. The groups included (i) experienced gas pistol shooters; (ii) persons with experience in video shooting games; and (iii) persons with no shooting experience. The viewing time was varied in the tests. The results showed that experience had a significant effect on the mean and root mean square (RMS) shooting errors at the target. The results also showed that the viewing time does not need to exceed about 2 s for an experienced pistol shooter and about 3 s for a novice shooter to reach the best performance. Two models for the effects of limited viewing time are proposed; both models fit the data well when the viewing time is less than about 2 s. The results indicated that the differences occurring with varying levels of experience are due to postural balance and not due to the aiming or cognitive component of the task.     

A constrained recursive pseudo-linear regression scheme for on-line parameter estimation in adaptive control

In adaptive control of systems with poles close to the unit circle, application of the recursive estimation techniques can lead to excursions of the poles of the identified model outside the unit circle even when the process is open loop stable. These excursions can be of two types. The poles of the deterministic component of the model can drift outside unit circle even when the process has no unstable modes. Alternatively, the poles and/or zeros of the unmeasured disturbance (noise) model can drift outside the unit circle. In either case, the identified model is not suitable for on-line controller adaptation. In this work, a novel constrained recursive formulation is proposed for on-line parameter estimation based on the pseudo-linear regression (PLR) approach. The efficacy of the proposed approach is demonstrated by conducting experimental studies on a benchmark laboratory scale heater-mixer setup. The analysis of the open and closed loop experimental results reveals that the proposed constrained parameter estimation scheme provides a systematic and computationally attractive approach to ensure that the identified model parameters are restricted to the feasible region.     

A qualitative study on the comfort and fit of ladies' dress shoes

The perceived differences between comfortable and uncomfortable shoes and the fit preferences in the different regions of ladies' shoes were explored. Twenty Hong Kong Chinese females participated in the study. Each participant wore and rated the different aspects of their own comfortable and uncomfortable shoes. The Wilcoxon signed rank tests showed significant differences in ten perceived characteristics between the comfortable and uncomfortable shoes. Among the ten were tactile, auditory and olfactory sensations. The ten items reliably (Cronbach alpha>0.9) distinguished between comfortable and uncomfortable shoes. There were no significant differences between comfortable and uncomfortable shoes for aesthetic-related characteristics. Further analysis on the fit ratings showed a significant impact on the fit preferences in the Toe region (p<0.0001), Metatarsophalangeal (MPJ) region (p<0.0001), Arch region (p=0.002) and Ingress/egress opening (p<0.001). Knowing the preferred type of fit can help establish a specification for comfortable shoes and also brings out the criteria that a comfortable shoe does not necessarily have the same perceived fit in every region of a shoe.     

The Effect of a Web-Based Tutorial on Problem Formulation Ability

Business programs are under greater pressure than ever to provide their students with the analytical skills they will need for effective problem solving. The increasing complexity of today's business environment and the expanding volume of data to support decision making require students to have better modeling skills. Tutorials can shape and enhance skill development in domains which are process intensive and contain problems where mastery and proficiency require practice. In this paper, we present a web-based tutorial, MS-Tutor, to coach students on all aspects of algebraic formulation of linear and integer programs. Such tutorials have the potential to become an integral component of web-based course offerings. However, it is important to design the content in such a way that it enhances the learning process. MS-Tutor was designed by considering the following dimensions: Structure, which refers to the organization of the content; Feedback, so students can learn from mistakes; and Dialog, which affects the interaction between the user and the tutor. The results indicate there is potential for performance improvement if the tutor is used.     

Sol-gel derived la modified PZT thin films: structure and properties

Lanthanum modified PZT thin films with compositions, namely 8/60/40, 8/70/30, 10/70/30 and 12/70/30 were deposited on platinized silicon substrates by sol-gel spin coating technique. Characterization of these films by XRD and SEM show that the films possess perovskite phase with submicron crystallite size. The saturation polarization (Ps), remnant polarization (PR) and coercive field (Ec) of polarization-electric field hysteresis loop are presented for all compositions. The 8/60/40 composition shows hysteresis loop with P/sub R/ = 11 /spl mu/C/cm/sup 2/. The temperature dependence of dielectric constant and dielectric loss of these films are also studied. Leakage current densities for these thin films are found to be in the range of 10/sup -/-10/sup -/ A/cm/sup 2/. To show the possible application of these thin films for micro electromechanical system (MEMS), a device incorporating an 8/60/40 PLZT thin film has been fabricated using silicon micromachining technology. This device functions satisfactorily as a vibration sensor with a resonance frequency of approximately 8.45 MHz.     

Model based foot shape classification using 2D foot outlines

This study introduces a novel technique to identify foot outline characteristics and to classify feet into groups using turning functions and clustering techniques so that shape can complement anthropometry in producing good fitting shoes. The digital 3D foot scans, obtained from 50 Hong Kong Chinese subjects (25 males and 25 females) were processed to generate the foot outlines at heights of 2 mm and 40 mm. The outlines were represented as turning functions and the similarity among shapes was determined using average linkage clustering. The results show that there are two distinct shape groups for the 40 mm foot outlines on both medial and lateral sides of the foot. The presence (46%) or absence (54%) of a medial bulge characterizes the medial side, while the two shape groups on the lateral side are mainly due to the lateral concavity in the mid-foot region. The group with a lateral concavity consists of more females (68%) and thus lateral side of foot outline appears to be gender related. Furthermore, the medial and lateral side clusters are not related to each other. The medial side shape from the 2 mm foot outline is a good indicator of fallen arches. Based on the analyses, four types of feet were identified: feet with (1) lateral concavity and a medial bulge, (2) a medial bulge and no lateral concavity, (3) lateral concavity and no medial bulge and (4) lateral concavity and a medial bulge. These shape differences can be useful in the design of shoe lasts and in the manufacture of compatible footwear so that trial and error fitting can be minimized.