Melt rheology and morphology of PP/SEBS/PC ternary blend

Melt rheological properties of the ternary blend of isotactic polypropylene (PP), styreneethylene–butylene–styrene terpolymer (SEBS), and polycarbonate (PC), PP/SEBS/PC, are studied in a wide range of composition, such that PP is the matrix and SEBS and PC are the minor components, with the proportion of one varying from 0 to 30% at various fixed compositions of the other. The respective binary blends, PP/SEBS and PP/PC, studied as the reference systems for interpretation of results on the ternary blends yielded interesting new information about the morphology development and its correlation with melt rheological properties of these binary blends. The studies include the measurement of melt rheological properties on a capillary rheometer in the shear rate range 10¹–10⁴ s^?1 at a fixed temperature of 240°C. The data presented as conventional flow curves are analyzed for the effect of blend composition and shear rate on pseudoplasticity, melt viscosity, and melt elasticity, and role of each individual component is identified. Morphology of dispersed phases of these blends is studied through scanning electron microscopy of the cryogenically fractured and suitably etched surfaces. Variations of morphology with blend composition and shear rate showed interesting correlation with melt rheological properties, which are discussed in detail. An important finding of the morphological studies is that in the PP/SEBS/PC ternary blend the SEBS phase forms two types of morphologies depending on the blend composition and shear rate: (i) simple droplets and (ii) boundary layer at the surface of the PC droplets. © 1993 John Wiley & Sons, Inc.     

Explicit finite difference scheme for nonlinear convective problems

An explicit finite difference scheme is proposed for nonlinear convective problems. The procedure is applied to a nonlinear convective diffusion problem with a nonlinear boundary condition. It is shown that the nonlinear boundary condition may be treated directly without linearization which has to be carried out in the implicit method to avoid a nonlinear system of algebraic equations. The explicit procedure is more direct and less cumbersome than the implicit procedure and the answers are in excellent agreement with those of the implicit method.     

A microfluidic device for thermal particle detection

We demonstrate the use of heat to count microscopic particles. A thermal particle detector (TPD) was fabricated by combining a 500-nm-thick silicon nitride membrane containing a thin-film resistive temperature detector with a silicone elastomer microchannel. Particles with diameters of 90 and 200 μm created relative temperature changes of 0.11 and ?0.44 K, respectively, as they flowed by the sensor. A first-order lumped thermal model was developed to predict the temperature changes. Multiple particles were counted in series to demonstrate the utility of the TPD as a particle counter.     

An electrochemically regenerative hydrogen-chlorine energy storage system: electrode kinetics and cell performance

The electrochemical oxidation and reduction of hydrogen and chlorine in hydrochloric acid has been investigated on graphite, ruthenized titanium and platinum electrodes. Both steady state and potentiostatic pulse methods were used. Cell studies were also carried out in cells with flow-by and flow-through chlorine electrodes. Results indicate that the electrode kinetics are fast and the electrolysis and fuel cell reactions can be carried out in the same cell with electric-to-electric efficiencies in excess of 75% at current densities of 300 mA cm^–2. Mass transfer limitations at the chlorine electrode during discharge can be eliminated by cell pressurization and the use of flow-through electrodes.This study was carried out under the auspices of the US Department of Energy.in the summers of 1976 and 1977     

Poly(ethyl acrylate) in dilute solution

Poly(ethyl acrylate) (PEA), solution polymerized in methyl ethyl ketone by free radical initiation, was fractionated and the fractions were characterized by light scattering, viscometry and osmometry. Fractions obtained were in the molecular weight range of 0·3 × 10⁶ to 1·6 × 10⁶ with a polydispersity of 1.40. The following Mark-Houwink relations were established:

$\text{[η]}{}^{\mathrm{<mtext>35°</mtext><mtext>C</mtext>}}{}_{\mathrm{<mtext>acetone</mtext>}}\text{=4·15×10}{}^{\mathrm{?2}}\text{M}{}^{\mathrm{0?61}}{}_{\mathrm{W}}$

$\text{[η]}{}^{\mathrm{<mtext>35°</mtext><mtext>C</mtext>}}{}_{\mathrm{<mtext>MEK</mtext>}}\text{=2·03×10}{}^{\mathrm{?2}}\text{M}{}^{\mathrm{0?66}}{}_{\mathrm{W}}$

$\text{[η]}{}^{\mathrm{<mtext>39.5°</mtext><mtext>C</mtext>}}{}_{\mathrm{<mtext>n-propanal</mtext>}}\text{=7·89×10}{}^{\mathrm{?2}}\text{M}{}^{\mathrm{0?50}}{}_{\mathrm{W}}$

It was found that n-propanol at 39.5°C was a theta solvent for poly(ethyl acrylate) and that acetone was a poor solvent compared to methyl ethyl ketone. A relation between the molecular dimension and the molecular weight was established. It was observed that the chain dimensions of poly(ethyl acrylate) and poly(butyl acrylate) were considerably larger than poly(ethyl methacrylate) and poly(butyl methacrylate) respectively. The validity of various extrapolation procedures that have been proposed for calculating the unperturbed dimensions have been examined. The steric factor for PEA was 2·16 compared to 2·10 for poly(ethyl methacrylate). Root mean square end-to-end distances were calculated from the Debye-Bueche and Kirkwood-Riseman methods and compared with the experimental values.     

A New Method for Getting Rational Approximation for Fractional Order Differintegrals

In this paper a new algorithm is presented to calculate the poles and zeros to approximate a fractional order (FO) differintegral (s^±α,α∈(0,1)) by a rational function on a finite frequency band ω∈(ω_l,ω_h). The constant phase property of the FO differintegral is the basis for development of the algorithm. Interlacing of real poles and zeros is used to achieve the constant phase. The calculations are done using the asymptotic Bode phase plot. A brief investigation is made to get a good approximation for the Bode phase plot. Two design parameters are introduced to keep the average phase close to the desired phase angle and to keep the error within the allowed bounds. A study is done to empirically understand the relationship between the error and the design parameters. The results thus obtained help in the further calculations. The algorithm is computationally simple and inexpensive, and gives a fairly good approximation of fractance frequency response on the specified frequency band.     

Mobile service oriented architectures for NN-queries

The ever-increasing number of mobile device users has also raised the users’ expectation of mobile services accordingly. This phenomenon has given pressures to the mobile service providers to improve their services in order to stay competitive in the market. The service oriented approach is seen to be a promising scheme for mobile services. This paper presents mobile service oriented architectures for Nearest-Neighbor (NN) queries that are classified into five categories, namely (i) intermittent query mobile services, (ii) continuous query mobile services, (iii) context-aware mobile services, (iv) continuous moving object query mobile services, and (v) data broadcast mobile services. These services incorporate query, location and context-aware services, ontological context model, and broadcast. The proposed architectures are concerned with mobile services for clients on the move requesting services based on their current location, which is arguably the most important feature in a wireless environment. Furthermore, we also discuss the Quality-of-Service (QoS) requirement for mobile services in which request latency time is one of the most important parameters to consider. Some analytical models for query latency measurement are presented and the results are compared with the simulation experiments.     

Characterizing the cross-sectional geometry of thin,non-cylindrical,twisted fibres (spider silk)

Quantitative tensile property evaluation of fibres requires accurate cross-sectional area measurement at a location close to the point of failure. Laser diffraction was evaluated as a non-destructive technique for characterizing the cross-sectional geometry of translucent, non-cylindrical, and/or twisted fibres with thicknesses in the range 2–5 m. Forcibly silked major ampullate fibres from Nephila clavipes spiders were used as specimens. Scanning electron microscopy was used to calibrate the extent to which laser diffraction over- or under-estimates fibre diameter. For the purpose of area measurement, elliptical or oval cross-sections can be treated as though they were circular. We demonstrate mathematically that the area can be obtained to within a few per cent of the true value, if (a) the circle is assigned an equivalent diameter equal to the average of at least four measurements of apparent diameter, (b) the apparent diameter measurements are taken at equal intervals of fibre rotation through a 180° range, and (c) the axial ratio of the cross-section is less than 1.5. The extent to which a non-cylindrical fibre is twisted can be deduced from the periodicity of bright and dark regions that alternate along the length of the fibre in reflected light. Values of cross-sectional ellipticity and area measured from a twisted fibre were smaller than the corresponding values obtained from a twist-free fibre. The apparent diameter of twist-free major ampullate fibre was found to be highly variable-by as much as ±20% relative to the mean within a 0.6 mm length. Therefore, local measurements of area, rather than a value derived from fibre denier, should be used in tensile property evaluation of this material.     

Mixed-Mode Stress Intensity Factor Determination of Riveted Lap Joints Used in Aircraft Fuselage Structures

Journal of Failure Analysis and Prevention - In the present work, mixed-mode stress intensity factor (SIF) of multiple cracks in a riveted lap joint has been determined, with and without the...     

A simulation study on the US rehabilitation service process for patients with modest-to-severe traumatic brain injury

Traumatic brain injury (TBI) is a devastating injury with severe consequences. In this paper, we conduct a simulation study on the commonly implemented care delivery process for TBI rehabilitation in the US, which covers three care categories: inpatient acute, outpatient sub-acute and general residential care. Our investigation is focused on assessing how coverage duration of publicly funded rehabilitation impacts two key system outcomes: sub-acute rehabilitation readmission and total rehabilitation spending. We develop prediction models on the above two outcomes for patients of different conditions. We introduce the notions of forceful transition and medical necessity adjustment, and embed the notions in a state-transition simulation model. Our simulation results suggest that to minimise the care spending, the duration of publicly insured outpatient sub-acute rehab be set smaller than what is currently implemented but not to the point where coverage should be completely removed. Our sensitivity analysis justifies the robustness of our results under variations on model parameters.