Effect of surface treatments on rheological,mechanical and magnetic properties of ferrite-filled polymeric systems

Experimental data on the effect of the type and amount of surface treating agents on the rheological and mechanical properties of the ferrite-filled styrene-isoprene-styrene systems at high levels of loading has been presented. The viscosities of the treated ferrite systems are found to be lower than the untreated systems, with the extent in reduction depending upon the type and amount of surface treatment. It is also found that surface treatment decreases the tensile strength and percentage elongation in the present filler-matrix system, and the extent of the decrease in viscosity as well as mechanical properties is more in the presence of titanates than with silanes.     

Re-analysis of extensional flow data of polymer melts

Extensional flow behaviour is very important in polymer processing operations such as fiber spinning and film blowing but there is scanty experimental data in the literature due to inherent difficulties in measurement of the relevant flow parameters. In the present paper, an attempt has been made to correlate the existing available data on the extensional flow of three generic types of polymer melts through a logarithmic plot of modified extensional viscosity function, η_E · MFI, and a modified extension rate, (ε/MFI)². The method may be extended to other polymeric systems.     

Laminar natural convection heat transfer from a slender vertical cone to a power-law fluid

A theoretical analysis of laminar natural convection heat transfer from a slender vertical cone to a power-law fluid has been done by the approximate integral method. Assuming unequal thermal and momentum boundary layer thicknesses, and using the appropriate boundary and compatibility conditions, a “similar” solution of the boundary layer equations has been obtained for high Prandtl numbers. Due to lack of experimental data for power-law fluids, a comparison of the predictions of the present analysis has been done with the experimental data available for Newtonian fluids and good agreement has been found.     

Supercontinuum generation in a Bragg fiber：a novel proposal

Nonlinear optical effects such as self-phase modula-tion,four-wave mixing,cross-phase modulation,sti mula-ted Raman scattering,together with appropriate tempo-ral dispersion profileinan optical fiber couldsignificant-ly broaden ( >100 nm) the spectrumof a…     

Partitioning and mapping in embedded multiprocessor architectures in the presence of constraints

The paper focuses on the problem of partitioning and mapping parallel programs onto heterogeneous embedded multiprocessor architectures for real-time applications. Such applications present unique constraints and challenges. In addition to heterogeneity, the proposed partitioning and mapping algorithms satisfy memory, task throughput, task placement, intertask communication bandwidth, and co-location constraints. They do so for architectures that utilize circuit-switched (rather than packet-switched) interprocessor communication and optimize latency and throughput in addition to load-balancing. Finally, these mapping algorithms make use of knowledge of the local scheduling discipline to accommodate real-time scheduling constraints. Our focus is on unstructured parallel programs that fall into one of two classes: (i) the class of computations characteristic of control applications in a real-time environment where tasks execute concurrently, periodically exchanging information, and (ii) pipelined computation graphs found in sensor data processing applications. The algorithms are implemented in a set of tools that operate with commercial CASE tools at one end, and present an interface to multiprocessor simulators at the other end. Collectively, the algorithms form a significant component of an interactive design environment for the development and mapping of real-time embedded parallel programs. The paper describes the algorithms, the encapsulating toolset, and presents an example of their application to an existing embedded application—an Autonomous Underwater Vehicle application.     

Rheograms of filled polymer melts from melt-flow index

Polymers filled with extending fillers, such as calcium carbonate or talc, or with reinforcing fillers, such as glass fibers or mica, are increasingly being used in a number of applications. The addition of fillers to a polymer changes the melt rheological behavior of the polymer. A knowledge of the viscosity vs. shear-rate flow curves of the filled system at various temperatures and as a function of filler parameters (such as filler type, shape, and amount) is necessary for process design, optimization, and trouble shooting. The generation of such rheological data is ezpensive and cumbersome in view of the broad range of fillers and the large numbers of filler parameters. In the present article, a unifying approach is proposed that coalesces the flow curves of filled systems of a polymer at various temperatures into a master curve that is independent of the filler parameters. An effective methods is presented to estimate the rheograms of filled systems with the use of a master curve, characteristic of a genetic resin type, knowing the melt-flow index and glass-transition temperature of the system. Master curves have been reported for filled system of low-density polyethylene, high-density polyethylene, poly-propylene polystyrene, nylons, poly(ethylene terephthalate), and polycarbonate.     

Melt rheology of highly loaded ferrite-filled polymer composites

This paper presents new experimental data on the viscosity of ferrite-filled polymers at high levels of loading. The choice of matrix and the choice of filler and filler loading has direct relevance to commercially important systems of magnetic plastics and rubbers. The effect of shear rate, concentration, and temperature on the rheological behavior of such highly loaded systems has been discussed in detail. The differences in the relative viscosities between the filled and unfilled systems for various matrices have been explained on the basis of polymer filler affinity and filler-filler interaction.