Stability of viscosity solutions on expanding networks

In this paper, we prove the stability of viscosity solutions of the Hamilton--Jacobi equations for a sequence of networks embedded in Euclidean space. The network considered in this paper is not merely a graph -- it comprises a collection of line segments. We investigate the conditions under which the stability of viscosity solutions holds if the sequence of networks converges to some compact set in the Hausdorff sense. As a corollary, a characterization of the limit of a sequence of networks on which viscosity solutions can be considered, is obtained. In consideration of this problem, we adopt the concept of viscosity solutions as presented in the sense of Gangbo and \'{S}wi\k{e}ch.Comment: 21 page

The influence of magnetic field on wear in sliding contacts

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University on 13/12/2010.The influence of the horizontal magnetic field has not been sufficiently studied in contrast to study activity on the influence of the vertical magnetic field by researchers. The reason was that the influence of horizontal magnetic field to change the wear mass loss of ferromagnetic materials is smaller compared to the vertical magnetic field. However, the influence of horizontal magnetic field on rolling contact changes the subsurface crack initiation point toward surface is postulated by a researcher. Therefore, it is significance finding out how the horizontal magnetic field influences the tribological characteristics. This thesis presents a study on the influence of the horizontal magnetic field on wear in sliding contacts contributes for ascertainment the effect and mechanism of horizontal magnetic field on tribological characteristics of sliding contacts, through the experimental approach.The static magnetic field with densities of 0 and 1.1 Tesla and different orientations was applied to different contact conditions, different surface modifications and two sliding frequencies, using a ball-on-plate contact configuration. In conclusion, the presence of magnetic field enhances the chemical adsorption between iron or oxide iron and oxygen, and causes the transition of adhesive wear to oxidative wear. Besides, the presence of magnetic field combined with low sliding frequency forms the bulging on the wear surface and weakens the prevailing wear mechanism due to the low frictional temperature. On the other hand, the presence of magnetic field combined with high sliding frequency induces the transition to the oxidative wear mechanism and reduces the wear. Also, distinctly different appearances of wear surface are created by different magnetic field orientations. In the lubricated sliding contact, the magnetic field causes the reduction of wear and induction of oxide. It is postulated that the presence of magnetic field enhances the oxygen adsorption on the wear track by iron wear particles and hence varies the tribological behaviour. The influence of magnetic field on carbon steel coating consists in changes of oxide iron layer and steel layer, alterations of mechanical properties of the coating, and decrease in the mass loss and the surface roughness on the dry sliding contact. All these could be suggested the influence of adhesive strength of the interface between the base material and coating

Experimental Study on Physical Properties of CuO - PVE Nano-oil and its Mixture with Refrigerant

Refrigeration oil is generally used in refrigerant compressor for lubrication. Recently, a nano-oil, which is a suspension of base lubrication oil and nano-order particles, is proposed to pursue further improvement of refrigeration cycle efficiency. There are many advantages by using nano-oil as lubrication oil in refrigerant compressor; (a) improvement of thermophysical property of lubrication oil, (b) bearing effect at sliding part, and (c) sealing effect of leakage of refrigerant and so on. For actual application of nano-oil to refrigeration system, it is important to investigate the effect of addition of nano-particles to the physical properties of refrigeration oil and its mixture of refrigerant at first. In this study, we measured not only thermal conductivity, but also other physical properties such as viscosity and dielectric constant of nano-oil itself. In addition to nano-oil, such physical properties of refrigerant / nano-oil mixture were also measured and the effect of nano-particles was discussed. Nano-oil was prepared by dispersing CuO nano-particles into refrigeration oil with 0.5, 1.0 and 3.0 vol% of the volume fraction. We chose Polyvinyl ether (PVE) as a refrigeration oil in this study. Temperature of nano-oil was ranged from 30 to 100 °C. The results show that thermal conductivity, viscosity and dielectric constant of the nano-oil are larger than those of the base oil. The increase of these properties becomes large with increasing volume fraction of nano-particles. On the other hand, the physical properties of refrigerant / nano-oil mixture were measured in a pressure vessel. R410A was used as a refrigerant in this study. The temperature was kept at 30 °C. The concentration of refrigerant in nano-oil was measured by the sampling method. The results show that thermal conductivity, viscosity and dielectric constant of R410A / PVE-CuO nano-oil are larger than those of R410A / PAG for the small concentration of refrigerant. The tendency that the increasing level of these properties becomes small with increasing refrigerant concentration was observed

Control of Vicinal Stereocenters through Nickel-Catalyzed Alkyl-Alkyl Cross-Coupling

Vicinal stereocenters are found in many natural and unnatural compounds. Although metal-catalyzed cross-coupling reactions of unactivated alkyl electrophiles are emerging as a powerful tool in organic synthesis, there have been virtually no reports of processes that generate, much less control, vicinal stereocenters. In this investigation, we establish that a chiral nickel catalyst can mediate doubly stereoconvergent alkyl–alkyl cross-coupling, specifically, reactions of a racemic pyrrolidine-derived nucleophile with cyclic alkyl halides (as mixtures of stereoisomers) to produce vicinal stereocenters with very good stereoselectivity

Measurements of Atmospheric Antiprotons

We measured atmospheric antiproton spectra in the energy range 0.2 to 3.4 GeV, at sea level and at balloon altitude in the atmospheric depth range 4.5 to 26 g/cm^2. The observed energy spectra, including our previous measurements at mountain altitude, were compared with estimated spectra calculated on various assumptions regarding the energy distribution of antiprotons that interacted with air nuclei.Comment: Accepted for publication in PL

Measurement of cosmic-ray low-energy antiproton spectrum with the first BESS-Polar Antarctic flight

The BESS-Polar spectrometer had its first successful balloon flight over Antarctica in December 2004. During the 8.5-day long-duration flight, almost 0.9 billion events were recorded and 1,520 antiprotons were detected in the energy range 0.1-4.2 GeV. In this paper, we report the antiproton spectrum obtained, discuss the origin of cosmic-ray antiprotons, and use antiprotons to probe the effect of charge sign dependent drift in the solar modulation.Comment: 18 pages, 1 table, 5 figures, submitted to Physics Letters

The influence of magnetic field on wear in sliding contacts

The influence of the horizontal magnetic field has not been sufficiently studied in contrast to study activity on the influence of the vertical magnetic field by researchers. The reason was that the influence of horizontal magnetic field to change the wear mass loss of ferromagnetic materials is smaller compared to the vertical magnetic field. However, the influence of horizontal magnetic field on rolling contact changes the subsurface crack initiation point toward surface is postulated by a researcher. Therefore, it is significance finding out how the horizontal magnetic field influences the tribological characteristics. This thesis presents a study on the influence of the horizontal magnetic field on wear in sliding contacts contributes for ascertainment the effect and mechanism of horizontal magnetic field on tribological characteristics of sliding contacts, through the experimental approach.The static magnetic field with densities of 0 and 1.1 Tesla and different orientations was applied to different contact conditions, different surface modifications and two sliding frequencies, using a ball-on-plate contact configuration. In conclusion, the presence of magnetic field enhances the chemical adsorption between iron or oxide iron and oxygen, and causes the transition of adhesive wear to oxidative wear. Besides, the presence of magnetic field combined with low sliding frequency forms the bulging on the wear surface and weakens the prevailing wear mechanism due to the low frictional temperature. On the other hand, the presence of magnetic field combined with high sliding frequency induces the transition to the oxidative wear mechanism and reduces the wear. Also, distinctly different appearances of wear surface are created by different magnetic field orientations. In the lubricated sliding contact, the magnetic field causes the reduction of wear and induction of oxide. It is postulated that the presence of magnetic field enhances the oxygen adsorption on the wear track by iron wear particles and hence varies the tribological behaviour. The influence of magnetic field on carbon steel coating consists in changes of oxide iron layer and steel layer, alterations of mechanical properties of the coating, and decrease in the mass loss and the surface roughness on the dry sliding contact. All these could be suggested the influence of adhesive strength of the interface between the base material and coating.EThOS - Electronic Theses Online ServiceGBUnited Kingdo