42,749 research outputs found
Network simulation using the simulation language for alternate modeling (SLAM 2)
The simulation language for alternate modeling (SLAM 2) is a general purpose language that combines network, discrete event, and continuous modeling capabilities in a single language system. The efficacy of the system's network modeling is examined and discussed. Examples are given of the symbolism that is used, and an example problem and model are derived. The results are discussed in terms of the ease of programming, special features, and system limitations. The system offers many features which allow rapid model development and provides an informative standardized output. The system also has limitations which may cause undetected errors and misleading reports unless the user is aware of these programming characteristics
Stratospheric circulation studies based on Tiros 7, 15-micron data Final report
Stratospheric temperature distribution data based on Tiros 7 radiometer dat
Modification of nucleon properties in nuclear matter and finite nuclei
We present a model for the description of nuclear matter and finite nuclei,
and at the same time, for the study of medium modifications of nucleon
properties. The nucleons are described as nontopological solitons which
interact through the self-consistent exchange of scalar and vector mesons. The
model explicitly incorporates quark degrees of freedom into nuclear many-body
systems and provides satisfactory results on the nuclear properties. The
present model predicts a significant increase of the nucleon radius at normal
nuclear matter density. It is very interesting to see the nucleon properties
change from the nuclear surface to the nuclear interior.Comment: 22 pages, 10 figure
Data acquisition and path selection decision making for an autonomous roving vehicle
Problems related to the guidance of an autonomous rover for unmanned planetary exploration were investigated. Topics included in these studies were: simulation on an interactive graphics computer system of the Rapid Estimation Technique for detection of discrete obstacles; incorporation of a simultaneous Bayesian estimate of states and inputs in the Rapid Estimation Scheme; development of methods for estimating actual laser rangefinder errors and their application to date provided by Jet Propulsion Laboratory; and modification of a path selection system simulation computer code for evaluation of a hazard detection system based on laser rangefinder data
Parametric down-conversion from a wave-equations approach: geometry and absolute brightness
Using the approach of coupled wave equations, we consider spontaneous
parametric down-conversion (SPDC) in the narrow-band regime and its
relationship to classical nonlinear processes such as sum-frequency generation.
We find simple expressions in terms of mode overlap integrals for the absolute
pair production rate into single spatial modes, and simple relationships
between the efficiencies of the classical and quantum processes. The results,
obtained with Green function techniques, are not specific to any geometry or
nonlinear crystal. The theory is applied to both degenerate and non-degenerate
SPDC. We also find a time-domain expression for the correlation function
between filtered signal and idler fields.Comment: 10 pages, no figure
Analysis of the spectral function of Nd1.85Ce0.15CuO4, obtained by angle resolved photoemission spectroscopy
Samples of Nd(2-x)Ce(x)CuO(4), an electron-doped high temperature
superconducting cuprate (HTSC), near optimal doping at x = 0.155 were measured
via angle resolved photoemission (ARPES). We report a renormalization feature
in the self energy ("kink") in the band dispersion at 50 - 60 meV present in
nodal and antinodal cuts across the Fermi surface. Specifically, while the kink
had previously only been seen in the antinodal region, it is now observed also
in the nodal region, reminiscent of what has been observed in hole-doped
cuprates.Comment: 4 pages, 4 figure
Nonlinear optical probe of tunable surface electrons on a topological insulator
We use ultrafast laser pulses to experimentally demonstrate that the
second-order optical response of bulk single crystals of the topological
insulator BiSe is sensitive to its surface electrons. By performing
surface doping dependence measurements as a function of photon polarization and
sample orientation we show that second harmonic generation can simultaneously
probe both the surface crystalline structure and the surface charge of
BiSe. Furthermore, we find that second harmonic generation using
circularly polarized photons reveals the time-reversal symmetry properties of
the system and is surprisingly robust against surface charging, which makes it
a promising tool for spectroscopic studies of topological surfaces and buried
interfaces
Regulating Highly Automated Robot Ecologies: Insights from Three User Studies
Highly automated robot ecologies (HARE), or societies of independent
autonomous robots or agents, are rapidly becoming an important part of much of
the world's critical infrastructure. As with human societies, regulation,
wherein a governing body designs rules and processes for the society, plays an
important role in ensuring that HARE meet societal objectives. However, to
date, a careful study of interactions between a regulator and HARE is lacking.
In this paper, we report on three user studies which give insights into how to
design systems that allow people, acting as the regulatory authority, to
effectively interact with HARE. As in the study of political systems in which
governments regulate human societies, our studies analyze how interactions
between HARE and regulators are impacted by regulatory power and individual
(robot or agent) autonomy. Our results show that regulator power, decision
support, and adaptive autonomy can each diminish the social welfare of HARE,
and hint at how these seemingly desirable mechanisms can be designed so that
they become part of successful HARE.Comment: 10 pages, 7 figures, to appear in the 5th International Conference on
Human Agent Interaction (HAI-2017), Bielefeld, German
Hard photon flow and photon-photon correlation in intermediate energy heavy-ion collisions
Hard photons emitted from energetic heavy ion collisions are very interesting
since they do not experience nuclear interaction, and therefore they are useful
to explore properties of nuclear matter. We investigated hard photon production
and its properties in intermediate energy heavy-ion collisions with the help of
the Blotzmann-Uehling-Ulenbeck model. Two components of hard photons are
discussed: direct and thermal. The positive directed flow parameter and
negative elliptic flow parameter of direct photons are demonstrated and they
are anti-correlated to the flows of free protons. The dependencies of hard
photon production and anisotropic parameters on impact parameter, beam energy,
nuclear equation of state and symmetry energy are also discussed. Furthermore,
we investigated the two-photon momentum correlation function from which the
space-time structure information of the photon source could be extracted as
well as the two-photon azimuthal correlation which could provide another good
method to determine the elliptic flow parameter of direct hard photons.Comment: 13 pages, 18 figure
- …