2,726 research outputs found
Ergonomic Models of Anthropometry, Human Biomechanics and Operator-Equipment Interfaces
The Committee on Human Factors was established in October 1980 by the Commission on Behavioral and Social Sciences and Education of the National Research Council. The committee is sponsored by the Office of Naval Research, the Air Force Office of Scientific Research, the Army Research Institute for the Behavioral and Social Sciences, the National Aeronautics and Space Administration, and the National Science Foundation. The workshop discussed the following: anthropometric models; biomechanical models; human-machine interface models; and research recommendations. A 17-page bibliography is included
InAs-AlSb quantum wells in tilted magnetic fields
InAs-AlSb quantum wells are investigated by transport experiments in magnetic
fields tilted with respect to the sample normal. Using the coincidence method
we find for magnetic fields up to 28 T that the spin splitting can be as large
as 5 times the Landau splitting. We find a value of the g-factor of about 13.
For small even-integer filling factors the corresponding minima in the
Shubnikov-de Haas oscillations cannot be tuned into maxima for arbitrary tilt
angles. This indicates the anti-crossing of neighboring Landau and spin levels.
Furthermore we find for particular tilt angles a crossover from even-integer
dominated Shubnikov-de Haas minima to odd-integer minima as a function of
magnetic field
Universality of the Gunn effect: self-sustained oscillations mediated by solitary waves
The Gunn effect consists of time-periodic oscillations of the current flowing
through an external purely resistive circuit mediated by solitary wave dynamics
of the electric field on an attached appropriate semiconductor. By means of a
new asymptotic analysis, it is argued that Gunn-like behavior occurs in
specific classes of model equations. As an illustration, an example related to
the constrained Cahn-Allen equation is analyzed.Comment: 4 pages,3 Post-Script figure
Learning to predict phases of manipulation tasks as hidden states
Phase transitions in manipulation tasks often occur
when contacts between objects are made or broken. A
switch of the phase can result in the robot’s actions suddenly
influencing different aspects of its environment. Therefore, the
boundaries between phases often correspond to constraints or
subgoals of the manipulation task.
In this paper, we investigate how the phases of manipulation
tasks can be learned from data. The task is modeled as an
autoregressive hidden Markov model, wherein the hidden phase
transitions depend on the observed states. The model is learned
from data using the expectation-maximization algorithm. We
demonstrate the proposed method on both a pushing task
and a pepper mill turning task. The proposed approach was
compared to a standard autoregressive hidden Markov model.
The experiments show that the learned models can accurately
predict the transitions in phases during the manipulation tasks
Proximity Effect, Andreev Reflections, and Charge Transport in Mesoscopic Superconducting-Semiconducting Heterostructures
In the quasi-twodimensional (Q2D) electron gas of an InAs channel between an
AlSb substrate and superconducting Niobium layers the proximity effect induces
a pair potential so that a Q2D mesoscopic
superconducting-normal-superconducting (SNS) junction forms in the channel. The
pair potential is calculated with quasiclassical Green's functions in the clean
limit. For such a junction alternating Josephson currents and current-voltage
characteristics (CVCs) are computed, using the non-equilibrium quasiparticle
wavefunctions which solve the time-dependent Bogoliubov-de Gennes Equations.
The CVCs exhibit features found experimentally by the Kroemer group: A steep
rise of the current at small voltages ("foot") changes at a "corner current" to
a much slower increase of current with higher voltages, and the zero-bias
differential resistance increases with temperature. Phase-coherent multiple
Andreev reflections and the associated Cooper pair transfers are the physical
mechanisms responsible for the oscillating Josephson currents and the CVCs.
Additional experimental findings not reproduced by the theory require model
improvements, especially a consideration of the external current leads which
should give rise to hybrid quasiparticle/collective mode excitations.Comment: 8 pages, 4 figures (consisting of 5 .ps-files), added referenc
Axisymmetric pulse recycling and motion in bulk semiconductors
The Kroemer model for the Gunn effect in a circular geometry (Corbino disks)
has been numerically solved. The results have been interpreted by means of
asymptotic calculations. Above a certain onset dc voltage bias, axisymmetric
pulses of the electric field are periodically shed by an inner circular
cathode. These pulses decay as they move towards the outer anode, which they
may not reach. As a pulse advances, the external current increases continuously
until a new pulse is generated. Then the current abruptly decreases, in
agreement with existing experimental results. Depending on the bias, more
complex patterns with multiple pulse shedding are possible.Comment: 8 pages, 15 figure
Interaction primitives for human-robot cooperation tasks
To engage in cooperative activities with human
partners, robots have to possess basic interactive abilities
and skills. However, programming such interactive skills is a
challenging task, as each interaction partner can have different
timing or an alternative way of executing movements. In this
paper, we propose to learn interaction skills by observing how
two humans engage in a similar task. To this end, we introduce
a new representation called Interaction Primitives. Interaction
primitives build on the framework of dynamic motor primitives
(DMPs) by maintaining a distribution over the parameters of
the DMP. With this distribution, we can learn the inherent
correlations of cooperative activities which allow us to infer the
behavior of the partner and to participate in the cooperation.
We will provide algorithms for synchronizing and adapting the
behavior of humans and robots during joint physical activities
Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018
Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field
- …