Reliability Criteria For Turbine Shaft Based On Coupling Type - Geared To Have Flexibility.

LecturePg. 43-50A turbine shaft end at the coupling is exposed not only to constant torque load but to various variable loads as well. These externally imposed variable loads come from sources like compressor surge, misalignment between turbine shaft, and the driven machine, to name a few. These loads can be bending or torsional in nature. To assure reliability, the design method should include the influence of such loads on the final sizing of the shaft end. The design method should also include the effects of shrink fits, keyways, fillets, chrome plating and fretting on the fatigue properties of the shaft material. Due to variable nature of loads superimposed on the steady torque load, the design method must be based on fatigue behavior of materials. Many fatigue theories have been used in the design of components of turbomachinery. These depend on the nature of the load, type of material and component being designed. A designer should realize not only the nature of loads imposed on the .shaft and their source but also have an estimate of the magnitude of those loads. A design method is described which includes many of the factors governing the useful life of the shaft at the coupling end. This method is based on the von Mises reliability criteria, including the influence of the driven machine and the choice of coupling type. This design method has resulted in many successful designs throughout the years and has helped in selecting a less costly but reliable option in many rerate situations

Sodium alginate microspheres for extending drug release: formulation and in vitro evaluation

In the present study, spherical microspheres of theophylline (TP) using sodium alginate as the hydrophilic carrier were prepared to prolong the release. The shape, surface and size characteristics were determined by scanning electron microscopy. The microspheres were found to be discreet and spherical in shape and had a smoother surface. The mean diameter of seven alginate microspheres formulations were between 7.6 ± 0.52 and 22.35 ±0.31 μm. It was observed that mean particle size of the microspheres increased with an increase in the concentration of polymer. The entrapment efficiency was found to be in the range of 70–93%. Optimized alginate microspheres were found to possess good sphericity, size and adequate entrapment efficiency. The in vitro release studies were carried out in pH progression media (pH 1.2, 2.5, 4.5, 7 and 7.4 solutions). Results indicated that percent drug release decreased with an increased alginate concentration. TP-loaded Alginate microspheres showed extended in vitro drug release thus use of microspheres potentially offers sustained release profile along with improved delivery of TP.Keywords: Extended drug delivery; Sodium alginate; Microspheres; Bronchial asthm

Natural Entropy Production in an Inflationary Model for a Polarized Vacuum

Though entropy production is forbidden in standard FRW Cosmology, Berman and Som presented a simple inflationary model where entropy production by bulk viscosity, during standard inflation without ad hoc pressure terms can be accommodated with Robertson-Walker's metric, so the requirement that the early Universe be anisotropic is not essential in order to have entropy growth during inflationary phase, as we show. Entropy also grows due to shear viscosity, for the anisotropic case. The intrinsically inflationary metric that we propose can be thought of as defining a polarized vacuum, and leads directly to the desired effects without the need of introducing extra pressure terms.Comment: 7 pages including front one. Accepted to publication, Astrophysics and Space Science, subjected to a minor correction, already submitte

The Reciprocal Influence Criterion: An Upgrade of the Information Quality Ratio

Understanding and quantifying the mutual influence between systems remain crucial but challenging tasks in any scientific enterprise. The Pearson correlation coefficient, the mutual information, and the information quality ratio are the most widely used indicators, only the last two being valid for nonlinear interactions. Given their limitations, a new criterion is proposed, the reciprocal influence criterion, which is very simple conceptually and does not make any assumption about the statistics of the stochastic variables involved. In addition to being normalised as the information quality ratio, it provides a much better resilience to noise and much higher stability to the issues related to the determination of the involved probability distribution functions. A conditional version, to counteract the effects of confounding variables, has also been developed, showing the same advantages compared to the more traditional indicators. A series of systematic tests with numerical examples is reported, to compare the properties of the new indicator with the more traditional ones, proving its clear superiority in practically all respects

Data driven theory for knowledge discovery in the exact sciences with applications to thermonuclear fusion

In recent years, the techniques of the exact sciences have been applied to the analysis of increasingly complex and non-linear systems. The related uncertainties and the large amounts of data available have progressively shown the limits of the traditional hypothesis driven methods, based on first principle theories. Therefore, a new approach of data driven theory formulation has been developed. It is based on the manipulation of symbols with genetic computing and it is meant to complement traditional procedures, by exploring large datasets to find the most suitable mathematical models to interpret them. The paper reports on the vast amounts of numerical tests that have shown the potential of the new techniques to provide very useful insights in various studies, ranging from the formulation of scaling laws to the original identification of the most appropriate dimensionless variables to investigate a given system. The application to some of the most complex experiments in physics, in particular thermonuclear plasmas, has proved the capability of the methodology to address real problems, even highly nonlinear and practically important ones such as catastrophic instabilities. The proposed tools are therefore being increasingly used in various fields of science and they constitute a very good set of techniques to bridge the gap between experiments, traditional data analysis and theory formulation