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Starting from the coupled thermoelastic equations, an analytic formula is obtained for the surface deformation of a semi-infinite homogeneous and isotropic solid in an impulsive stimulated scattering (ISS) experiment. The surface ripple consists of a transient diffusive grating and a standing Rayleigh wave. The time evolution of the diffusive part directly reveals the thermal diffusivity. The oscillatory part then reveals the elastic properties, and explicit formulae are presented for retrieving the elastic moduli as a function of the frequency and amplitude of the standing Rayleigh wave. The analytic formulae not only allow to avoid time-consuming and delicate numerical integration but they also demonstrate the uniqueness of the inversion from signal to material parameters and offer direct insight into the error propagation. The formulae are applied to real experimental data, illustrating the strength and the limitations of the ISS technique. [ABSTRACT FROM AUTHOR]

The thermal characteristics of layered materials were investigated using a photoacoustic technique. The photoacoustic method was based on thermal waves, which posses other transmission and reflection properties than optical or acoustical waves. This characteristic allows it to obtain data which other techniques cannot. An inversion procedure was effective in obtaining depth information from the photoacoustic signal.

Starting from the Debye model for frequency-dependent specific heat and the Vogel-Fulcher-Tammann (VFT) model for its relaxation time, an analytic expression is presented for the heat capacity versus temperature trace for differential scanning calorimetry (DSC) of glass transitions, suggesting a novel definition of the glass transition temperature based on a dimensionless criterion. An explicit expression is presented for the transition temperature as a function of the VFT parameters and the cooling rate, and for the slope as a function of fragility. Also a generalization of the results to non-VFT and non-Debye relaxation is given. Two unique ways are proposed to tackle the inverse problem, i.e., to extract the fragility from an experimental DSC trace. Good agreement is found between theoretically predicted DSC traces and experimental DSC traces for glycerol for different cooling rates. [ABSTRACT FROM AUTHOR]

Starting from the exact solution for the photothermal signal in semi-infinite materials with an exponential and with a piecewise linear thermal conductivity profile, a set of equations valid for a broad class of profiles is derived for the direct computation of the conductivity profile depth and surface conductivity from the properties of the photothermal phase maximum alone. By virtue of the usual anticorrelation between conductivity gradient and hardening gradient, this can be used for the assessment of case depth and surface hardening of case-hardened steels. The results compare very well with the results of Vickers hardness tests. The methodology only applies to concave conductivity profiles, excluding e.g., sigmoidal shapes. [ABSTRACT FROM AUTHOR]

In this article, we apply our analytical theory, published earlier in this journal, to obtain information on the earth surface temperature history from some borehole temperature data. Compared to the results of the five different methods applied to the same temperature data, our method seems to be easier, assumption-free, and yields internally consistent results. The results suggest a cooling a few centuries ago, followed by a continuing warming up to these days, in agreement with a little ice age scenario. [ABSTRACT FROM AUTHOR]

In this article we address the problem of the reconstruction of surface temperature history of a semi-infinite solid from subsurface temperature wave data at one instant. This problem proves particularly interesting in relation to the geothermal history and the detection of climatic changes using borehole data. In particular we present exact analytical results valuable for this important inverse problem. We show how this provides us with a straightforward method which eliminates the need of foreknowledge typical of the current numerical approaches. [ABSTRACT FROM AUTHOR]