Microgeometrical tooth profile modification influencing efficiency of planetary hub gears

Planetary hub systems offer desired speed and torque variation with a lighter, compact and coaxial construction than the traditional gear trains. Generated friction between the mating teeth flanks of vehicular planetary hubs under varying load-speed conditions is one of the main sources of power loss. Modification of gear tooth geometry as well as controlling the contacting surface topography is the remedial action. The paper studies the effect of tooth crowning and tip relief upon system efficiency. It includes an analytical elastohydrodynamic analysis of elliptical point contact of crowned spur gear teeth. The analysis also includes the effect of direct contact of asperities on the opposing meshing surfaces. Tooth contact analysis (TCA) is used to obtain the contact footprint shape as well as contact kinematics and load distribution. A parametric study is carried out to observe the effect of gear teeth crowning and tip relief with different levels of surface finish upon the planetary hubs’ power loss

The synthesis and base-induced rearrangements of alpha-halophosphonamidates.

The work described in the thesis is concerned with the preparation and rearrangement of alpha-halophosphonamidates. The introduction reviews some of the important examples of Favorskii and Ramberg-Backlund rearrangements which illustrate the suspected mechanism and synthetic utility of these reactions. Analogous rearrangements in Organophosphorus chemistry have been reported, but there are few such examoles in the literature. The Discussion describes the synthesis of alpha-halophosphonamidates, by the conversion of the corresponding alpha-halophosphonic dichloride into the phosphonamidate by one of several variations. The effect of base on the phosphonamidates is described. Where reaction had occurred the products could be explained by the postulation of a three-membered ring formed from the loss of the elements of hydrogen halide from the alpha-halophosphonamidate. The nature of the products depended upon the direction of the ring- opening, which in turn depended upon the relative stability of the anions formed in ring-opening. By making several variations in the structure of the alpha-halophosphonamidate under study, an insight into the finer details of the mechanism is possible. The experimental conditions which have been employed in relation to the above work are described in the final section

Kinetics of the thermal decomposition of biomass and the influence of alkali metals on these kinetics

The thermal degradation of biomass has received extensive consideration due to its central role in biomass combustion. Biomass decomposition is also a major step in fast pyrolysis and other thermal processing methods involved in the production of chemicals. Detailed understanding of the kinetics of biomass decomposition is vital for reactor kinetics and combustion processes modeling. Analysis methods were studied to determine which method is best suited for reliable kinetic parameter extraction based TGA derived data, kinetics most applicable to industrial applications were explored. This paper then goes on to develop a preliminary expression (involving only SRC Willow and only potassium) directly linking biomass degradation kinetics to the inherent alkali metal content. The Senum-Yang, the Murray and White, and the reaction rate constant methods all yield apparent first-order kinetics that give excellent predictions of pyrolysis under slow heating rate conditions. For higher heating rates, as encountered under flash pyrolysis conditions, kinetics expressions with high E and A values typically give more sensible predictions of conversion. A Langmuir-Hinshelwood relation can be applied to describe the catalytic effect of potassium on biomass pyrolysis. The maximum reaction rate constant of 3.26 x 10-3 (s-1) and the potassium saturation constant of 0.56 (wt%) can be accurately used to derive the pyrolysis reaction rate at 300 °C of any willow sample with a known potassium concentration. A leveling off of the catalytic effect is seen with regard to potassium concentration and the apparent first-order reaction rate at ca. 4.5 wt%.</p

Assessment of the self-ignition characteristics of both torrefied and untreated biomass fuels

Legacy description not available</p

Commodity fuels from biomass through pre-treatment and torrefaction: effects of mineral content on torrefied fuel characteristics and quality

Legacy description not available</p

Behavior and role of alkali metals in biomass combustion

This paper details fundamental work on alkali metals (sodium, potassium, and cesium) to determine if group chemistry has an effect upon the catalytic process observed in SRC Willow thermal degradation, thereby gaining mechanistic insight into the process. Work detailing both pyrolysis and combustion (TGA), and combustion under flame conditions is presented. DTG profiles and first order reaction kinetics comparing the pyrolysis and combustion of the three alkali metal impregnated, raw, and demineralized samples revealed a strong and similar catalytic effect that all three alkali metals have on these reactions. Combustion under flame conditions again showed a stark contrast between the strongly catalyzed degradation of samples with alkali metal presence, and the uncatalyzed degradation of mineral-free samples. As with the low heating rate results, at flame conditions, no observable difference between samples impregnated with varous group 1 metals is noted. These findings imply that a similar thermal degredation mechanisim is followed when this woody biomass contains any alkali metals.</p

Assessment of the self-ignition characteristics of raw and processed biomass fuels

This paper is concerned with the self-ignition characteristics of untreated and torrefied biomass fuels and two coals. Using thermogravimetry in air, first order reaction kinetics at low temperature were derived, and the point of ignition and the maximum weight loss in air measured. In oxygen, data was obtained for the characteristic ignition temperature. Self–ignition temperatures and ignition delays were measured for two untreated and two torrefied biomass fuels for a number of different basket sizes using the European standard test method of spontaneous combustion.</p

Combustion of two imported biomass feedstocks for co-firing in the UK

Legacy description not available</p

Contra-indicators observed in cynomolgus macaques of Mauritian origin following aerosol infection with <i>M</i>. <i>tuberculosis</i>.

<p>Contra-indicators observed in cynomolgus macaques of Mauritian origin following aerosol infection with <i>M</i>. <i>tuberculosis</i>.</p