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- Berbyuk, Viktor, 1953, et al.
(författare)
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Optimization of control laws of the bipedal locomotion systems
- 1999
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Ingår i: In Advances in Computational Multibody Dynamics, Jorge A.C. Ambrósio and Werner O. Schiehlen (Eds.), IDMEC/IST, Lisbon, Portugal, September 20-23, 1999. ; , s. 713-728
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Konferensbidrag (refereegranskat)abstract
- The mathematical statement of the problem of energy-optimal control for a bipedal locomotion system is given. The proposed statement of the problem is characterized by broad utilization of experimental data of normal human locomotion. It is done mainly by means of the mathematical formulation of the constraints imposed both on the phase coordinates and on the controlling stimuli of a system. A numerical method for the solution of the optimal control problems for highly nonlinear and complex bipedal locomotion systems is proposed. The method is based on a special procedure of converting the initial optimal control problem into a standard nonlinear programming problem. This is made by an approximation of the independent variable functions using smoothing cubic splines and by the solution of an inverse dynamics problem. The key features of the method are its high numerical effectiveness and the possibility to satisfy a lot of restrictions imposed on the phase coordinates of the system automatically and accurately. The proposed method is illustrated by computer simulation of the energy-optimal anthropomorphic motion of the bipedal walking robot over a horizontal surface.
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- Boström, Anders E, 1951, et al.
(författare)
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UTDefect: A simulation tool for ultrasonic NDT
- 1996
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Ingår i: Proc. 14th Int. Conf. on NDE in the nuclear and pressure vessel industries.. - 0871705893 ; 1, s. 621-626
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Konferensbidrag (refereegranskat)
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- Eichberger, Arno, et al.
(författare)
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EVALUATION OF THE APPLICABILITY OF THE NECK INJURY CRITERION (NIC) IN REAR END IMPACTS ON THE BASIS OF HUMAN SUBJECT TESTS
- 1998
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Ingår i: PROCEEDINGS OF THE 1998 INTERNATIONAL IRCOBI CONFERENCE ON THE BIOMECHANICS OF IMPACT. ; , s. 321-233
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Konferensbidrag (refereegranskat)abstract
- The purpose of this investigation is to apply the neck injury criterion (NIC) Criterion to data measured in human subject tests. 70 volunteer tests and 28 cadaver tests were analyzed in order to investigate the movement of the human spine. The NIC was calculated for all these tests and compared to other data that could be of interest for neck injuries (for instance angular acceleration of the head). It is concluded that the NIC in conjunction with other parameters is a useful indicator for the prediction of neck injuries following rear end impacts.
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- Eriksson, Arne S., 1961, et al.
(författare)
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Ultrasonic wave propagation through a cracked solid
- 1995
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Ingår i: Wave Motion. - 0165-2125. ; 22, s. 297-310
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Tidskriftsartikel (refereegranskat)abstract
- The propagation of ultrasonic waves through a perfectly elastic medium containing a random distribution of equally-sized penny-shaped cracks with spring boundary conditions across the crack faces are considered. As limiting cases results for open and fluid-filled cracks are derived also. The medium with the crack distribution is modelled as an effective viscoelastic medium, using the non-interecting scatterer approximation and Foldy's thery. For this purpose the scattering by a single crack is solved by an integral equation method. Distributions of both randomly oriented and parallel cracks are considered. Numerical results are presented for the phase velocity and attenuation. For parallel cracks when the effective medium becomes transversely isotropic two further issues are investigated.The first is the extension of a static result due to Kachanov, who showed the transverse isotropy to be of a very special kind. The second is consistency of the wave speeds obtained by using Foldy's theory, with the fact that the effective material is transversely isotropic. In particular, the vertically polarized shear wave should have the same wave speeds in directions parallel and normal to the cracks. It is found that the relations established by Kachanov and the consistency requirements are satisfied by the phase velocity for all frequencies considered.
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- Wirdelius, Håkan, 1963, et al.
(författare)
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A model for ultrasonic NDE on defect detection
- 1995
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Ingår i: Proc. 13th Int. Conf. on NDE in the nuclear and pressure vessel industries. - 0871705486 ; , s. 237-243
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Konferensbidrag (refereegranskat)
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