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Start Over Author "Kallel F" Publication Type Academic Journals
169 results on '"Kallel F"'

6. Tissue elasticity reconstruction using linear perturbation method

Author

Kallel, F. and Bertrand, M.

Subjects
Tissues -- Models, Perturbation (Mathematics) -- Usage, Finite element method -- Usage, Business, Electronics, Electronics and electrical industries, Health care industry
Abstract

A new method to reconstruct the elastic modulus of soft tissue subjected to an external static compression is presented. In this approach the Newton-Raphson method is used to vary a finite element (FE) model of the elasticity equations to fit, in a least squared sense, a set of axial tissue displacement fields estimated using a correlation technique applied to ultrasound signals. The ill-conditioning of the Hessian matrix is eliminated using the Tikhonov regularization technique. This regularization provides a compromise between fidelity to the observed data and a priori information of the solution. Using an echographic image formation model, it is shown that the method converges within a few iterations (8-10) and that strain images artifacts which are common in elastography are significantly reduced after the resolution of the inverse problem.

Published
1996

7. Effects of moisture on temperature during drying of consolidated porous materials

Author

Kallel, F., Galanis, N., Perrin, B., and Javelas, R.

Subjects
Porous materials -- Thermal properties, Bricks -- Usage, Moisture -- Measurement, Engineering and manufacturing industries, Science and technology
Abstract

Homogeneous brick and mortar slabs aid the analysis of continual transfer of heat and moisture in consolidated porous materials. The extent of moisture is numerically hypothesized and temperature evolutions are studied and compared to validate the hypothesis. Initially, saturated slabs at 20 degrees centigrade show a quick fall in temperature to 13 degrees centigrade when they come into contact with air at 20 degrees centigrade and a 50% humidity as the extra content of water evaporates. The temperature of the slabs and the period of reduction in temperature are influenced by the original moisture content and the coefficients of the convection transfer.

Published
1993

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