John wilson

With the development and operation of high speed trains, condition based maintenance becomes an important approach for the improvement of reliability and safety of rail transportation. This paper reports a feasibility study using pulsed eddy current thermography for imaging multiple cracks caused by rolling contact fatigue (RCF). After reviewing rail track inspection and RCF cracks, a PEC thermography system is introduced and applied to the imaging of multiple rolling contact fatigue cracks. Potential on-line inspection for rail track is also discussed.

Abstract The analysis of magnetic Barkhausen noise (MBN) has been used to provide information about the stress state and microstructural properties of ferromagnetic materials. Recent work has shown that a technique using acoustic Barkhausen noise (ABN) detection can provide the similar capabilities as traditional MBN along with additional information for defect characterisation and thickness measurement in a single system. Because the detection of ABN using a piezoelectric sensor can be carried out at any point on the ...

Thermographic inspection with eddy current (EC) excitation is an emerging integrative NDT&E method with the ability to inspect for defects over large areas. The resultant surface heat distribution from direct EC heating and diffused heat can be obtained easily with a thermal camera, but techniques for the determination of heating mechanisms around a particular defect for quantitative defect characterisation are required. In this paper, numerical modelling and experimental studies are applied to understand EC stimulated thermography on simple discontinuity defects, including transient EC distribution and heating propagation for slots and notches. This fundamental understanding of transient EC distribution and heating propagation will aid in the development of feature extraction and pattern recognition techniques for the quantitative analysis of EC…

This paper studies ‘tax competition’ between two regions that tax interregionally mobile capital to finance local public goods. In the Nash equilibrium, residents of a relatively small region, measured by population size, are better off than residents of the large region; and they are better off than they would be under the economy's Pareto efficient tax rates, if their region is sufficiently small. These results are compared with related findings in the international trade and local public economics literatures. The same results are proved for a model where both capital and labor are taxed to satisfy an exogenous expenditure requirement.

Models of tax competition among local or regional governments typically assume that only a source-based tax on capital income is available. This paper presents a model where a wage tax is also available and shows that small regions choose not to tax capital income, given that it can only be taxed on a source basis. However, the model also yields the conclusion from previous tax competition models that local public goods are underprovided. In contrast, government use of the available tax instruments is efficient when both source- and residence-based capital taxes are available, even in the absence of wage taxation.

This paper reviews potential advantages and disadvantages of capital tax competition. Tax competition may introduce, mitigate, or exacerbate inefficiencies in both the private sector and the public sector. In different models, tax competition may either limit or increase public expenditures and taxes on mobile factors, with differing welfare consequences. We also discuss the implications of tax competition for redistributive policies and for policies dealing with risk, and we identify some of the possible empirical implications of tax competition.

A general equilibrium model is constructed to study tax competition, where local governments compete for capital by holding down property tax rates and public expenditure levels. An exact definition of tax competition is provided, and both the existence and nonexistence of tax competition are shown to be theoretically possible. It is argued, however, that tax competition must occur under empirically reasonable conditions. Inefficiency in public production is also explicitly modeled. The amount of capital used to produce a given level of public service output is shown to be greater than that which is required to minimize costs evaluated at the prices facing private firms.

We review the theoretical basis for, and the advantages of, random flight models for the trajectories of tracer particles in turbulence. We then survey their application to calculate dispersion in the principal types of atmospheric turbulence (stratified, vertically-inhomogeneous, Gaussian or non-Gaussian turbulence in the surface layer and above), and show that they are especially suitable for some problems (e.g., quantifying ground emissions).