Incorporation of TiC particles on AlSi 4340 low alloy steel surfaces via tungsten inert gas melting

Surface cladding utilizes a high energy input to deposit a layer on substrate surfaces providing protection against wear and corrosion. In this work, TiC particulates were incorporated by melting single tracks in powder preplaced onto AISI 4340 low alloy steel surfaces using a Tungsten Inert Gas (TIG) torch with a range of processing conditions. The effects of energy input and powder content on the melt geometry, microstructure and hardness were investigated. The highest energy input (1680J/mm) under the TIG torch produced deeper (1.0 mm) and wider melt pools, associated with increased dilution, compared to that processed at the lowest energy (1008J/mm). The melt microstructure contained partially melted TiC particulates associated with dendritic, cubic and globular type carbides precipitated upon solidification of TiC dissolved in the melt; TiC accumulated more near to the melt-matrix interface and at the track edges. Addition of 0.4, 0.5 and 1.0 mg/mm2 TiC gave hardness values in the resolidified melt pools between 750 to over 1100Hv, against a base hardness of 300 Hv; hardness values are higher in tracks processed with a grcater TiC addition and reduced energy input

Complete set of electromagnetic corrections to the nucleon mass in the Nambu-Jona-Lasinio model

We show how to derive the complete set of electromagnetic corrections to the Nambu-Jona-Lasinio (NJL) model of the nucleon. Our results enable an accurate estimate of the electromagnetic contribution to the neutron-proton mass difference within this model. At the same time, our procedure demonstrates the way to calculate the complete set of meson corrections to the NJL model that maintains chiral symmetry.Comment: Contribution to Proceedings, KEK-Tanashi International Symposium on Physics of Hadrons and Nuclei, 14-17 December 1998, Tokyo, Japan, to be published in Nuclear Physics A. 5 pages, revtex, epsf, 2 postscript figures. Minor addition to last figure, typos correcte

Evolution of a qubit under the influence of a succession of unsharp measurements

We investigate the evolution of a single qubit subject to a continuous unitary dynamics and an additional interrupting influence which occurs periodically. One may imagine a dynamically evolving closed quantum system which becomes open at certain times. The interrupting influence is represented by an operation, which is assumed to equivalently describe a non-selective unsharp measurement. It may be decomposed into a positive operator, which in case of a measurement represents the pure measurement part, followed by an unitary back-action operator. Equations of motion for the state evolution are derived in the form of difference equations. It is shown that the 'free' Hamiltonian is completed by an averaged Hamiltonian, which goes back to the back-action. The positive operator specifies a decoherence rate and results in a decoherence term. The continuum limit to a master equation is performed. The selective evolution is discussed and correcting higher order terms are worked out in an Appendix.Comment: 19 pages, no figure

Computing Tropical Varieties

The tropical variety of a $d$-dimensional prime ideal in a polynomial ring with complex coefficients is a pure $d$-dimensional polyhedral fan. This fan is shown to be connected in codimension one. We present algorithmic tools for computing the tropical variety, and we discuss our implementation of these tools in the Gr\"obner fan software \texttt{Gfan}. Every ideal is shown to have a finite tropical basis, and a sharp lower bound is given for the size of a tropical basis for an ideal of linear forms.Comment: 22 pages, 2 figure

Multi-layer LBIC system for thin film PV module characterisation

Several non-destructive characterisation tools - solar simulator, LBIC, thermography - are used together to investigate the performance of and locate possible defects in TF silicon PV modules of different structures. A special module is investigated where all techniques are compared and good agreement is demonstrated

Large area LBIC measurement system for thin film photovoltaic modules

A laser beam induced current system has been developed for large area thin film technology. Employing a non-destructive laser scanning approach, such a system is used as a characterisation tool that is able to perform local performance investigation and allows efficient defect detection in large scale devices. In this paper, the results are shown for large area single junction amorphous silicon modules. The scanning images reveal an inhomogeneous current signal. Cross-section analysis illustrates that in some modules, there is considerable performance variation between cells. Certain cells are nearly or completely inactive. Interconnection problems, tiny cracks and defects that cannot be detected by visual inspection can also be identified

Lives Saved by Helicopter Emergency Medical Services: An Overview of Literature

Introduction: The objective of this review is to give an overview of literature on the survival benefits of Helicopter Emergency Medical Services (HEMS). The included studies were assessed by study design and statistical methodology. Methods: A literature search was performed in the National Library of Medicine's Medline database, extending from 1985 until April 2007. Manuscripts had to be written in English and describe effects of HEMS on survival expressed in number of lives saved. Moreover, analysis had to be performed using adequate adjustment for differences in case-mix. Results: Sixteen publications met the inclusion criteria. All indicated that HEMS assistance contributed to increased survival: Between 1.1 and 12.1 additional survivors were recorded for every 100 HEMS uses. A combination of four reliable studies shows overall mortality reduction of 2.7 additional lives saved per 100 HEMS deployments. Conclusion: Literature shows a clear positive effect on survival associated with HEMS assistance. Efforts should be made to promote consistent methodology, including uniform outcome parameters, in order to provide sufficient scientific evidence to conclude the ongoing debate about the beneficial effects of HEMS