4,783 research outputs found
Effective Dynamics of Solitons in the Presence of Rough Nonlinear Perturbations
The effective long-time dynamics of solitary wave solutions of the nonlinear
Schr\"odinger equation in the presence of rough nonlinear perturbations is
rigorously studied. It is shown that, if the initial state is close to a slowly
travelling soliton of the unperturbed NLS equation (in norm), then, over
a long time scale, the true solution of the initial value problem will be close
to a soliton whose center of mass dynamics is approximately determined by an
effective potential that corresponds to the restriction of the nonlinear
perturbation to the soliton manifold.Comment: Reference [16] added. 19 page
Evaluating Trust and Safety in HRI : Practical Issues and Ethical Challenges
Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage, and that copies bear this notice and the full citation on the first page. Copyrights for third-party components of this work must be honored. For all other uses, contact the owner/author(s). Copyright is held by the owner/author(s). Date of Acceptance: 11/02/2015In an effort to increase the acceptance and persuasiveness of socially assistive robots in home and healthcare environments, HRI researchers attempt to identify factors that promote human trust and perceived safety with regard to robots. Especially in collaborative contexts in which humans are requested to accept information provided by the robot and follow its suggestions, trust plays a crucial role, as it is strongly linked to persuasiveness. As a result, human- robot trust can directly affect people's willingness to cooperate with the robot, while under- or overreliance could have severe or even dangerous consequences. Problematically, investigating trust and human perceptions of safety in HRI experiments is not a straightforward task and, in light of a number of ethical concerns and risks, proves quite challenging. This position statement highlights a few of these points based on experiences from HRI practice and raises a few important questions that HRI researchers should consider.Final Accepted Versio
Cyclic thermodynamic processes and entropy production
We study the time evolution of a periodically driven quantum-mechanical
system coupled to several reserviors of free fermions at different
temperatures. This is a paradigm of a cyclic thermodynamic process. We
introduce the notion of a Floquet Liouvillean as the generator of the dynamics
on an extended Hilbert space. We show that the time-periodic state to which the
true state of the coupled system converges after very many periods corresponds
to a zero-energy resonance of the Floquet Liouvillean. We then show that the
entropy production per cycle is (strictly) positive, a property that implies
Carnot's formulation of the second law of thermodynamics.Comment: version accepted for publication in J. Stat. Phy
Status of the Fundamental Laws of Thermodynamics
We describe recent progress towards deriving the Fundamental Laws of
thermodynamics (the 0th, 1st and 2nd Law) from nonequilibrium quantum
statistical mechanics in simple, yet physically relevant models. Along the way,
we clarify some basic thermodynamic notions and discuss various reversible and
irreversible thermodynamic processes from the point of view of quantum
statistical mechanics.Comment: 23 pages. Some references updated. To appear in J. Stat. Phy
A Robust Solution Procedure for Hyperelastic Solids with Large Boundary Deformation
Compressible Mooney-Rivlin theory has been used to model hyperelastic solids,
such as rubber and porous polymers, and more recently for the modeling of soft
tissues for biomedical tissues, undergoing large elastic deformations. We
propose a solution procedure for Lagrangian finite element discretization of a
static nonlinear compressible Mooney-Rivlin hyperelastic solid. We consider the
case in which the boundary condition is a large prescribed deformation, so that
mesh tangling becomes an obstacle for straightforward algorithms. Our solution
procedure involves a largely geometric procedure to untangle the mesh: solution
of a sequence of linear systems to obtain initial guesses for interior nodal
positions for which no element is inverted. After the mesh is untangled, we
take Newton iterations to converge to a mechanical equilibrium. The Newton
iterations are safeguarded by a line search similar to one used in
optimization. Our computational results indicate that the algorithm is up to 70
times faster than a straightforward Newton continuation procedure and is also
more robust (i.e., able to tolerate much larger deformations). For a few
extremely large deformations, the deformed mesh could only be computed through
the use of an expensive Newton continuation method while using a tight
convergence tolerance and taking very small steps.Comment: Revision of earlier version of paper. Submitted for publication in
Engineering with Computers on 9 September 2010. Accepted for publication on
20 May 2011. Published online 11 June 2011. The final publication is
available at http://www.springerlink.co
- …