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Three-dimensional finite-element modelling and improvement of a bispherical intervertebral disc prosthesis (1999)

Templier, A. ; Skalli, W. ; Lemaire, J. P. ; [et al.]

Springer

European journal of orthopaedic surgery & traumatology 9 (1999), S. 51-58

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ISSN: 1432-1068

Keywords: Lumbar ; Disc prosthesis ; F.e.m. ; In vitro testing

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Summary The load-displacement behaviour of six fresh human cadaveric L2–L3 spinal segments was studied through in vitro testing in flexion, and torsion. The lumbar spinal units were tested firstly intact, then instrumented by the SB Charité III intervertebral disc prosthesis with respect to the surgical requirements. These experiments highlighted an increase of mobility yielded by the implantation of the prosthesis, especially in torsion. Numerical models of both the L2–L3 spinal segment and the disc prosthesis were used. Simulations were performed on an intact spinal segment model, as well as on an instrumented segment model, by reproducing the same boundary conditions as used experimentally. The results of these simulations indicated a realistic behaviour of the model when comparing numerical results to experimental ones. This allowed us to validate our numerical models and to use them to calculate compressive forces transmitted by the posterior facets. Numerical results indicated an increase of the facet loading during torsion, yielded by the implantation of the prosthesis. Three technical changes to the original design were then simulated. These changes were meant to increase the global stiffness of the implanted segment, and to reduce articular facet loading in torsion. One of the solutions reduced axial rotation in torsion without decreasing articular loading. This observation is explained through a simple mechanical model of a lumbar spinal unit in torsion. This mechanical model was used to define the last solution, which succeeded in both reducing axial rotation and intra-articular loading.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01695723

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Advanced multivariable control of a pilot-plant distillation column (1983)

Ogunnaike, B. A. ; Lemaire, J. P. ; Morari, M. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

AIChE Journal 29 (1983), S. 632-640

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ISSN: 0001-1541

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology

Notes: This paper reports an experimental study of the multivariable control of a pilot-plant distillation column having a side stream as well as overhead and bottom products. A recently developed multivariable controller for systems having multiple time delays is implemented for the first time on an experimental process. The controller consists of a new multivariable time delay compensator coupled with traditional PI controllers. Realization is accomplished with a PDP 11 minicomputer. Improved system performance was observed with the delay compensator, especially in disturbance rejection.

Additional Material: 17 Ill.