2,415 research outputs found
Geometric approach to Fletcher's ideal penalty function
Original article can be found at: www.springerlink.com Copyright Springer. [Originally produced as UH Technical Report 280, 1993]In this note, we derive a geometric formulation of an ideal penalty function for equality constrained problems. This differentiable penalty function requires no parameter estimation or adjustment, has numerical conditioning similar to that of the target function from which it is constructed, and also has the desirable property that the strict second-order constrained minima of the target function are precisely those strict second-order unconstrained minima of the penalty function which satisfy the constraints. Such a penalty function can be used to establish termination properties for algorithms which avoid ill-conditioned steps. Numerical values for the penalty function and its derivatives can be calculated efficiently using automatic differentiation techniques.Peer reviewe
A Study into the Effect of the Presence of Moisture at the Wheel/Rail Interface during Dew and Damp Conditions
Incidents involving low levels of adhesion between the wheel and rail are a recurrent issue in the rail
industry. The problem has been mitigated using friction modifiers and traction enhancers, but a significant
number of incidents still occur throughout the year. The following work looks at the environmental
conditions that surround periods of low adhesion in order to provide an insight into why low adhesion
events occur. Network Rail Autumn data, which provided details on the time and location of low adhesion
incidents, was compared against weather data on a national and then local scale. Low adhesion incidents
have often been attributed to contamination on the rail, such as organic leaf matter, but other incidents occur
when no contamination is visible. The time, date and location of incidents were linked to local weather data
to establish any specific weather conditions that could lead to these events. The effects of precipitation,
temperature and humidity on the rail were analysed in order to further the understanding of low adhesion
in the wheel-rail contact, which will lead to better methods of mitigating this problem
WhoLoDancE: Towards a methodology for selecting Motion Capture Data across different Dance Learning Practice
<p>In this paper we present the objectives and preliminary work of WhoLoDancE a Research and Innovation Action funded under the European Union‘s Horizon 2020 programme, aiming at using new technologies for capturing and analyzing dance movement to facilitate whole-body interaction learning experiences for a variety of dance genres. Dance is a diverse and heterogeneous practice and WhoLoDancE will develop a protocol for the creation and/or selection of dance sequences drawn from different dance styles for different teaching and learning modalities. As dance learning practice lacks standardization beyond dance genres and specific schools and techniques, one of the first project challenges is to bring together a variety of dance genres and teaching practices and work towards a methodology for selecting the appropriate shots for motion capturing, to acquire kinetic material which will provide a satisfying proof of concept for Learning scenarios of particular genres. The four use cases we are investigating are 1) classical ballet, 2) contemporary dance, 3) flamenco and 4) Greek folk dance.</p
Activation of Ventral Tegmental Area 5-HT2C Receptors Reduces Incentive Motivation
FUNDING AND DISCLOSURE The research was funded by Wellcome Trust (WT098012) to LKH; and National Institute of Health (DK056731) and the Marilyn H. Vincent Foundation to MGM. The University of Michigan Transgenic Core facility is partially supported by the NIH-funded University of Michigan Center for Gastrointestinal Research (DK034933). The remaining authors declare no conflict of interest. ACKNOWLEDGMENTS We thank Dr Celine Cansell, Ms Raffaella Chianese and the staff of the Medical Research Facility for technical assistance. We thank Dr Vladimir Orduña for the scientific advice and technical assistance.Peer reviewedPublisher PD
A precise asteroseismic age and radius for the evolved Sun-like star KIC 11026764
The primary science goal of the Kepler Mission is to provide a census of
exoplanets in the solar neighborhood, including the identification and
characterization of habitable Earth-like planets. The asteroseismic
capabilities of the mission are being used to determine precise radii and ages
for the target stars from their solar-like oscillations. Chaplin et al. (2010)
published observations of three bright G-type stars, which were monitored
during the first 33.5 days of science operations. One of these stars, the
subgiant KIC 11026764, exhibits a characteristic pattern of oscillation
frequencies suggesting that it has evolved significantly. We have derived
asteroseismic estimates of the properties of KIC 11026764 from Kepler
photometry combined with ground-based spectroscopic data. We present the
results of detailed modeling for this star, employing a variety of independent
codes and analyses that attempt to match the asteroseismic and spectroscopic
constraints simultaneously. We determine both the radius and the age of KIC
11026764 with a precision near 1%, and an accuracy near 2% for the radius and
15% for the age. Continued observations of this star promise to reveal
additional oscillation frequencies that will further improve the determination
of its fundamental properties.Comment: 16 pages, 6 figures, 4 tables, ApJ in pres
Nicotinic receptors
Regulation of normal or abnormal behaviour is critically controlled by the central serotonergic systems. Recent evidence has suggested that serotonin (5-HT) neurotransmission dysfunction contributes to a variety of pathological conditions, including depression, anxiety, schizophrenia and Parkinson’s disorders. There is also a great amount of evidence indicating that 5-HT signalling may affect the reinforcing properties of drugs of abuse by the interaction and modulation of dopamine (DA) function. This chapter is focused on one of the more addictive drugs, nicotine. It is widely recognised that the effects of nicotine are strongly associated with the stimulatory action it exhibits on mesolimbic DAergic function. We outline the role of 5-HT and its plethora of receptors, focusing on 5-HT2 subtypes with relation to their involvement in the neurobiology of nicotine addiction. We also explore the novel pharmacological approaches using 5-HT agents for the treatment of nicotine dependence. Compelling evidence shows that 5-HT2C receptor agonists may be possible therapeutic targets for smoking cessation, although further investigation is required.peer-reviewe
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Modeling trends in cohort survival probabilities
A new dynamic parametric model is proposed for analyzing the cohort survival function. A one-factor parameterized polynomial in age effects, complementary log-log link and multinomial cohort responses are utilized, within the generalized linear models (GLM) framework. Sparse Principal component analysis (SPCA) is then applied to cohort dependent parameter estimates and provides (marginal) estimates for a two-factor structure. Modeling the two-factor residuals in a similar way, in age-time effects, provides estimates for the three-factor age-cohort-period model. An application is presented for Sweden, Norway, England & Wales and Denmark mortality experience
The primary cosmic ray composition between 10**15 and 10**16 eV from Extensive Air Showers electromagnetic and TeV muon data
The cosmic ray primary composition in the energy range between 10**15 and
10**16 eV, i.e., around the "knee" of the primary spectrum, has been studied
through the combined measurements of the EAS-TOP air shower array (2005 m
a.s.l., 10**5 m**2 collecting area) and the MACRO underground detector (963 m
a.s.l., 3100 m w.e. of minimum rock overburden, 920 m**2 effective area) at the
National Gran Sasso Laboratories. The used observables are the air shower size
(Ne) measured by EAS-TOP and the muon number (Nmu) recorded by MACRO. The two
detectors are separated on average by 1200 m of rock, and located at a
respective zenith angle of about 30 degrees. The energy threshold at the
surface for muons reaching the MACRO depth is approximately 1.3 TeV. Such muons
are produced in the early stages of the shower development and in a kinematic
region quite different from the one relevant for the usual Nmu-Ne studies. The
measurement leads to a primary composition becoming heavier at the knee of the
primary spectrum, the knee itself resulting from the steepening of the spectrum
of a primary light component (p, He). The result confirms the ones reported
from the observation of the low energy muons at the surface (typically in the
GeV energy range), showing that the conclusions do not depend on the production
region kinematics. Thus, the hadronic interaction model used (CORSIKA/QGSJET)
provides consistent composition results from data related to secondaries
produced in a rapidity region exceeding the central one. Such an evolution of
the composition in the knee region supports the "standard" galactic
acceleration/propagation models that imply rigidity dependent breaks of the
different components, and therefore breaks occurring at lower energies in the
spectra of the light nuclei.Comment: Submitted to Astroparticle Physic
Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
Quantum ESPRESSO is an integrated suite of computer codes for
electronic-structure calculations and materials modeling, based on
density-functional theory, plane waves, and pseudopotentials (norm-conserving,
ultrasoft, and projector-augmented wave). Quantum ESPRESSO stands for "opEn
Source Package for Research in Electronic Structure, Simulation, and
Optimization". It is freely available to researchers around the world under the
terms of the GNU General Public License. Quantum ESPRESSO builds upon
newly-restructured electronic-structure codes that have been developed and
tested by some of the original authors of novel electronic-structure algorithms
and applied in the last twenty years by some of the leading materials modeling
groups worldwide. Innovation and efficiency are still its main focus, with
special attention paid to massively-parallel architectures, and a great effort
being devoted to user friendliness. Quantum ESPRESSO is evolving towards a
distribution of independent and inter-operable codes in the spirit of an
open-source project, where researchers active in the field of
electronic-structure calculations are encouraged to participate in the project
by contributing their own codes or by implementing their own ideas into
existing codes.Comment: 36 pages, 5 figures, resubmitted to J.Phys.: Condens. Matte
In situ evidence for the structure of the magnetic null in a 3D reconnection event in the Earth's magnetotail
Magnetic reconnection is one of the most important processes in
astrophysical, space and laboratory plasmas. Identifying the structure around
the point at which the magnetic field lines break and subsequently reform,
known as the magnetic null point, is crucial to improving our understanding
reconnection. But owing to the inherently three-dimensional nature of this
process, magnetic nulls are only detectable through measurements obtained
simultaneously from at least four points in space. Using data collected by the
four spacecraft of the Cluster constellation as they traversed a diffusion
region in the Earth's magnetotail on 15 September, 2001, we report here the
first in situ evidence for the structure of an isolated magnetic null. The
results indicate that it has a positive-spiral structure whose spatial extent
is of the same order as the local ion inertial length scale, suggesting that
the Hall effect could play an important role in 3D reconnection dynamics.Comment: 14 pages, 4 figure
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