Rayleigh Waves Generated by a Thermal Source: A Three-Dimensional Transient Thermoelasticity Solution

A three-dimensional transient thermoelastic solution is obtained for Rayleigh-type disturbances propagating on the surface of a half-space. These surface waves are generated by either a buried or surface thermal source, which has the form of a concentrated heat flux applied impulsively. In an effort to model this problem as realistically as possible, the half-space material is taken to respond according to Biot’s fully coupled thermoelasticity. The problem has relevance to situations involving heat generation due to: (i) laser action (impulsive electromagnetic radiation) on a surface target, (ii) underground nuclear activity, and (iii) friction developed during underground fault motions related to seismic activity. The problem was attacked with unilateral and double bilateral Laplace transforms, which suppress, respectively, the time variable and two of the space variables. The Rayleigh wave contribution is obtained as a closed-form expression by utilizing asymptotics, complex-variable theory and certain results for Bessel functions. The dependence of the normal displacement associated with the Rayleigh wave upon the distance from the source epicenter and the distance from the wavefront is also determined

Transient crack propagation in asymmetric cruciform paths

The problem of two cracks emanating from the same origin and propagating asymmetrically at different velocities in an elastic and isotropic solid is treated in this paper. An unbounded and otherwise undisturbed medium and a constant anti-plane loading at infinity were assumed. Techniques of self-similar elastodynamics were utilized in conjunction with analytic-function theory. Since a closed-form solution of such a problem is impossible we relied in the last steps of the procedure upon numerical analysis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41718/1/707_2005_Article_BF01190888.pd

Cracked orthotropic strip with clamped boundaries

The stress intensity factor at the tip of a semi-infinite crack in an orthotropic infinite strip was determined. Clamped strip boundaries were considered.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43435/1/33_2004_Article_BF00948963.pd

The Panel Conditionally Homogenous Vector-Autoregressive Model

In the panel conditionally homogenous vectorautoregressive model, the cross-sectional units' dynamics are generally heterogenous, but homogenous if units share the same structural characteristics. The panel conditionally homogenous vectorautoregressive model thus allows (i) to account for heterogeneity in dynamic panel data sets, (ii) to nevertheless exploit the panel nature of the data, and (iii) to analyze the relationship between the units' observed heterogeneities and structural characteristics. I show how standard least squares estimation can be applied, how impulse responses can be computed, how multivariate conditioning is implemented, and how polynomial order restrictions can be incorporated. Finally, I present an easy-to-use Matlab routine which can be used to estimate the panel conditionally homogenous vectorautoregressive model and produce impulse responses as well as forecast error variance decompositions

An appropriate tool for entrepreneurial learning in SMEs? The case of the 20Twenty Leadership Programme

The 20Twenty Leadership Programme was developed by Cardiff Metropolitan University as an executive education programme to be delivered within South Wales to small businesses. It is funded by the European Social Fund (ESF) and administered by the Welsh European Funding Office and has the key aim of developing SME’s growth potential via a range of leadership and management skills, including a focus on ‘soft’ skills. The focus of this paper is to place the 20Twenty Leadership Programme within the wider context of entrepreneurship policy and SME training initiatives in particular, and then to examine the rationale and delivery methods of the Programme in relation to these. It also reflects on the Programme’s success (or otherwise) to date where possible. Finally, the paper seeks to suggest fruitful areas of further research both in terms of the 20Twenty Leadership Programme itself, but also with regard to evaluation in relation to other parallel programmes, and to SME training initiatives more generally

The problem of sharp notch in microstructured solids governed by dipolar gradient elasticity

In this paper, we deal with the asymptotic problem of a body of infinite extent with a notch (re-entrant corner) under remotely applied plane-strain or anti-plane shear loadings. The problem is formulated within the framework of the Toupin-Mindlin theory of dipolar gradient elasticity. This generalized continuum theory is appropriate to model the response of materials with microstructure. A linear version of the theory results by considering a linear isotropic expression for the strain-energy density that depends on strain-gradient terms, in addition to the standard strain terms appearing in classical elasticity. Through this formulation, a microstructural material constant is introduced, in addition to the standard Lamé constants . The faces of the notch are considered to be traction-free and a boundary-layer approach is followed. The boundary value problem is attacked with the asymptotic Knein-Williams technique. Our analysis leads to an eigenvalue problem, which, along with the restriction of a bounded strain energy, provides the asymptotic fields. The cases of a crack and a half-space are analyzed in detail as limit cases of the general notch (infinite wedge) problem. The results show significant departure from the predictions of the standard fracture mechanics