9,103 research outputs found
On Beltrami Model of de Sitter Spacetime
Based on some important properties of space, we present a Beltrami model
that may shed light on the observable puzzle of space
and the paradox between the special relativity principle and cosmological
principle. In , there are inertial-type coordinates and
inertial-type observers. Thus, the classical observables can be defined for
test particles and light signals. In addition, by choosing the definition of
simultaneity the Beltrami metric is transformed to the Robertson-Walker-like
metric. It is of positive spatial curvature of order . This is more or
less indicated already by the CMB power spectrum from WMAP and should be
further confirmed by its data in large scale.Comment: 4 page
Reverse Engineering Psychologically Valid Facial Expressions of Emotion into Social Robots
Social robots are now part of human society, destined for schools, hospitals, and homes to perform a variety of tasks. To engage their human users, social robots must be equipped with the essential social skill of facial expression communication. Yet, even state-of-the-art social robots are limited in this ability because they often rely on a restricted set of facial expressions derived from theory with well-known limitations such as lacking naturalistic dynamics. With no agreed methodology to objectively engineer a broader variance of more psychologically impactful facial expressions into the social robots' repertoire, human-robot interactions remain restricted. Here, we address this generic challenge with new methodologies that can reverse-engineer dynamic facial expressions into a social robot head. Our data-driven, user-centered approach, which combines human perception with psychophysical methods, produced highly recognizable and human-like dynamic facial expressions of the six classic emotions that generally outperformed state-of-art social robot facial expressions. Our data demonstrates the feasibility of our method applied to social robotics and highlights the benefits of using a data-driven approach that puts human users as central to deriving facial expressions for social robots. We also discuss future work to reverse-engineer a wider range of socially relevant facial expressions including conversational messages (e.g., interest, confusion) and personality traits (e.g., trustworthiness, attractiveness). Together, our results highlight the key role that psychology must continue to play in the design of social robots
Quantum ratchet transport with minimal dispersion rate
We analyze the performance of quantum ratchets by considering the dynamics of
an initially localized wave packet loaded into a flashing periodic potential.
The directed center-of-mass motion can be initiated by the uniform modulation
of the potential height, provided that the modulation protocol breaks all
relevant time- and spatial reflection symmetries. A poor performance of quantum
ratchet transport is characterized by a slow net motion and a fast diffusive
spreading of the wave packet, while the desirable optimal performance is the
contrary. By invoking a quantum analog of the classical P\'eclet number, namely
the quotient of the group velocity and the dispersion of the propagating wave
packet, we calibrate the transport properties of flashing quantum ratchets and
discuss the mechanisms that yield low-dispersive directed transport.Comment: 6 pages; 3 figures; 1 tabl
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