The main objective of this thesis is to develop a constraint algorithm for sin- gular k-cosymplectic field theories. We begin by reviewing the Hamiltonian and Lagrangian formalisms for autonomous and nonautonomous mec...
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The main objective of this thesis is to develop a constraint algorithm for sin- gular k-cosymplectic field theories. We begin by reviewing the Hamiltonian and Lagrangian formalisms for autonomous and nonautonomous mechanics and field theory. Then we present the constraint algorithms for presym- plectic and precosymplectic systems, which are geometric frameworks for singular autonomous and nonautonomous mechanical systems. We also re- view the constraint algorithm k-presymplectic systems, which are geometric models for singular autonomous field theories. Finally, the last part of the work is devoted to defining the concepts of k-precosymplectic manifold, prov- ing the existence of Reeb vector fields in these manifolds, k-precosymplectic Hamiltonian system and to develop a constraint algorithm in order to find a submanifold where the existence of solutions of the field equations is assured.
Current research on suture simulation mainly focus on the construction of suture line, and existing suture simulation systems still need to be improved in terms of diversity, soft tissue effects, and stability. This p...
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Current research on suture simulation mainly focus on the construction of suture line, and existing suture simulation systems still need to be improved in terms of diversity, soft tissue effects, and stability. This paper presents an integrated liver suture surgery system composed of three consecutive suture circumstances, which is conducive to liver suture surgery training. The physically-based models used in this simulation are based on different mass-spring models regulated by a special constrained algorithm, which can improve the model accuracy, and stability by appropriately restraining the activity sphere of the surrounding mass nodes around the suture points. We also studied the kinematic model to update the status of suture points in real time, according to an external force exerted by the operators, which can sense synchronous force feedback in return as well. Moreover, in case that the sutured wounds tear open again, a suture control strategy is designed to ensure the stability of the whole suturing procedure. Several experiments are carried out to validate the model performance in terms of model accuracy, suture control effects, and comprehensive training effects. The experiment results show that the proposed models have realistic visual and haptic feedback, stable control on the suture, as well as good training effects as an integrated liver suture surgery system compared to other suture simulation systems which only simulate suture on a single kind of soft tissue.
Lie groupoid, called second-order non-holonomic material Lie groupoid, is associated in a natural way to any Cosserat medium. This groupoid is used to give a new definition of homogeneity which does not depend on a ma...
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Lie groupoid, called second-order non-holonomic material Lie groupoid, is associated in a natural way to any Cosserat medium. This groupoid is used to give a new definition of homogeneity which does not depend on a material archetype. The corresponding Lie algebroid, called second-order non-holonomic material Lie algebroid, is used to characterize the homogeneity property of the material. We also relate these results with the previously obtained ones in terms of non-holonomic second-order G-structures.
To solve the stiffness reduction problem caused by cohesive surfaces in the intrinsic cohesive finite element model (CFEM), a series of constraint conditions are introduced into the algebraic equation system of the CF...
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To solve the stiffness reduction problem caused by cohesive surfaces in the intrinsic cohesive finite element model (CFEM), a series of constraint conditions are introduced into the algebraic equation system of the CFEM to constrain the separation of cohesive surfaces. To make the constrained cohesive surfaces active at the appropriate time, the constraint conditions will be removed in the high stress zone where fracture could initiate and propagate. The efficiency of the constrained CFEM, instead of being reduced by the constraint conditions, is significantly improved because the constrained cohesive surfaces are not counted in the numerical implementation. (C) 2015 Elsevier Ltd. All rights reserved.
The k-symplectic formulation of field theories is especially simple, since only tangent and cotangent bundles are needed in its description. Its defining elements show a close relationship with those in the symplectic...
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The k-symplectic formulation of field theories is especially simple, since only tangent and cotangent bundles are needed in its description. Its defining elements show a close relationship with those in the symplectic formulation of mechanics. It will be shown that this relationship also stands in the presymplectic case. In a natural way, one can mimick the presymplectic constraint algorithm to obtain a constraint algorithm that can be applied to k-presymplectic field theory, and more particularly to the Lagrangian and Hamiltonian formulations of field theories defined by a singular Lagrangian, as well as to the unified Lagrangian-Hamiltonian formalism (Skinner-Rusk formalism) for k-presymplectic field theory. Two examples of application of the algorithm are also analyzed.
In order to shorten new product development cycles, parallel approach is emphasized to organize and plan the process of product design in Collaborative Product Development (CPD), in which a great deal of constraints o...
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ISBN:
(纸本)9783642160653
In order to shorten new product development cycles, parallel approach is emphasized to organize and plan the process of product design in Collaborative Product Development (CPD), in which a great deal of constraints of interdependent, interactive and restrictive relationships exist. The motivation of this article is to provide a simple and effective method to solve this problem. In new product development, collaboration is usually conducted according to product structure. In accordance with this principle, a constraint network is presented and an algorithm is given out. While the constraints can not be met, then conflict will arise. A consultation model is established. Finally, a case is put forward to explain how the algorithm for constraint network and consultation model work.
The purpose of this article is to describe Lagrangian mechanics for constrained systems on Lie algebroids, a natural framework which covers a wide range of situations (systems on Lie groups, quotients by the action of...
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The purpose of this article is to describe Lagrangian mechanics for constrained systems on Lie algebroids, a natural framework which covers a wide range of situations (systems on Lie groups, quotients by the action of a Lie group, standard tangent bundles ). In particular, we are interested in two cases: singular Lagrangian systems and vakonomic mechanics (variational constrained mechanics). Several examples illustrate the interest of these developments.
A new type of array signal processing combined with a weighted least squares algorithm to enable two-channel output with binaural information is proposed in this paper. This algorithm may be effective for use in a bin...
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A new type of array signal processing combined with a weighted least squares algorithm to enable two-channel output with binaural information is proposed in this paper. This algorithm may be effective for use in a binaural hearing aid because the interaural relationship can be preserved after array signal processing. Retaining spatial information on specified directions while sufficiently suppressing unnecessary ambient noise coming from directions other than those of target sounds is required for this type of algorithm. In order to satisfy these two simultaneous requirements, the proposed algorithm was derived from a constraint algorithm by employing the weighted least squares algorithm. Performance in directivity patterns as well as interaural time difference (ITD) and interaural level difference (ILD) were evaluated. Computer simulations showed that this algorithm yields robust performance in various conditions compared with array signal processing based on a constraint algorithm. (C) 2004 Elsevier Ltd. All rights reserved.
作者：
Cortés, JMartínez, SCantrijn, FUniv Ghent
Dept Math Phys & Astron B-9000 Ghent Belgium CSIC
Inst Matemat & Fis Fundamental E-28006 Madrid Spain Univ Twente
Fac Math Sci Syst Signals & Control Dept NL-7500 AE Enschede Netherlands
The geometric approach to autonomous classical mechanical systems in terms of a canonical first-order system on the Whitney sum of the tangent and cotangent bundle, developed by Skinner and Rusk, is extended to the ti...
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The geometric approach to autonomous classical mechanical systems in terms of a canonical first-order system on the Whitney sum of the tangent and cotangent bundle, developed by Skinner and Rusk, is extended to the time-dependent framework. (C) 2002 Elsevier Science B.V. All rights reserved.
A geometrical setting in terms of jet manifolds is developed for time-dependent non-holonomic Lagrangian systems. An almost product structure on the evolution space is constructed in such a way that the constrained dy...
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A geometrical setting in terms of jet manifolds is developed for time-dependent non-holonomic Lagrangian systems. An almost product structure on the evolution space is constructed in such a way that the constrained dynamics is obtained by projection of the free dynamics. A constrained Poincare-Cartan 2-form is defined. If the non-holonomic system is singular, a constraint algorithm is constructed. Special attention is devoted to Caplygin systems and a reduction theorem is proved.
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