9,617 research outputs found
Loyalty to relationships: Examination of affluent casino guest retention in Las Vegas
This paper analyzes the challenges faced by Las Vegas, Nevada casinos when catering to their affluent guests. As part of the literature review, the paper will examine the various retention efforts taken by luxury products and service providers, along with luxury hotels and hotel casinos in Las Vegas. Personal communications with casino hotel executives provides a real-world comparison of the effectiveness and limitations of various techniques discussed in the literature review
On the formation of current sheets in response to the compression or expansion of a potential magnetic field
The compression or expansion of a magnetic field that is initially potential
is considered. It was recently suggested by Janse & Low [2009, ApJ, 690, 1089]
that, following the volumetric deformation, the relevant lowest energy state
for the magnetic field is another potential magnetic field that in general
contains tangential discontinuities (current sheets). Here we examine this
scenario directly using a numerical relaxation method that exactly preserves
the topology of the magnetic field. It is found that of the magnetic fields
discussed by Janse & Low, only those containing magnetic null points develop
current singularities during an ideal relaxation, while the magnetic fields
without null points relax toward smooth force-free equilibria with finite
non-zero current.Comment: Accepted for publication in Ap
Integrating heterogeneous distributed COTS discrete-event simulation packages: An emerging standards-based approach
This paper reports on the progress made toward the emergence of standards to support the integration of heterogeneous discrete-event simulations (DESs) created in specialist support tools called commercial-off-the-shelf (COTS) discrete-event simulation packages (CSPs). The general standard for heterogeneous integration in this area has been developed from research in distributed simulation and is the IEEE 1516 standard The High Level Architecture (HLA). However, the specific needs of heterogeneous CSP integration require that the HLA is augmented by additional complementary standards. These are the suite of CSP interoperability (CSPI) standards being developed under the Simulation Interoperability Standards Organization (SISO-http://www.sisostds.org) by the CSPI Product Development Group (CSPI-PDG). The suite consists of several interoperability reference models (IRMs) that outline different integration needs of CSPI, interoperability frameworks (IFs) that define the HLA-based solution to each IRM, appropriate data exchange representations to specify the data exchanged in an IF, and benchmarks termed CSP emulators (CSPEs). This paper contributes to the development of the Type I IF that is intended to represent the HLA-based solution to the problem outlined by the Type I IRM (asynchronous entity passing) by developing the entity transfer specification (ETS) data exchange representation. The use of the ETS in an illustrative case study implemented using a prototype CSPE is shown. This case study also allows us to highlight the importance of event granularity and lookahead in the performance and development of the Type I IF, and to discuss possible methods to automate the capture of appropriate values of lookahead
Gunrock: A High-Performance Graph Processing Library on the GPU
For large-scale graph analytics on the GPU, the irregularity of data access
and control flow, and the complexity of programming GPUs have been two
significant challenges for developing a programmable high-performance graph
library. "Gunrock", our graph-processing system designed specifically for the
GPU, uses a high-level, bulk-synchronous, data-centric abstraction focused on
operations on a vertex or edge frontier. Gunrock achieves a balance between
performance and expressiveness by coupling high performance GPU computing
primitives and optimization strategies with a high-level programming model that
allows programmers to quickly develop new graph primitives with small code size
and minimal GPU programming knowledge. We evaluate Gunrock on five key graph
primitives and show that Gunrock has on average at least an order of magnitude
speedup over Boost and PowerGraph, comparable performance to the fastest GPU
hardwired primitives, and better performance than any other GPU high-level
graph library.Comment: 14 pages, accepted by PPoPP'16 (removed the text repetition in the
previous version v5
Ballistic-Ohmic quantum Hall plateau transition in graphene pn junction
Recent quantum Hall experiments conducted on disordered graphene pn junction
provide evidence that the junction resistance could be described by a simple
Ohmic sum of the n and p mediums' resistances. However in the ballistic limit,
theory predicts the existence of chirality-dependent quantum Hall plateaus in a
pn junction. We show that two distinctively separate processes are required for
this ballistic-Ohmic plateau transition, namely (i) hole/electron Landau states
equilibration and (ii) valley iso-spin dilution of the incident Landau edge
state. These conclusions are obtained by a simple scattering theory argument,
and confirmed numerically by performing ensembles of quantum magneto-transport
calculations on a 0.1um-wide disordered graphene pn junction within the
tight-binding model. The former process is achieved by pn interface roughness,
where a pn interface disorder with a root-mean-square roughness of 10nm was
found to suffice under typical experimental conditions. The latter process is
mediated by extrinsic edge roughness for an armchair edge ribbon and by
intrinsic localized intervalley scattering centers at the edge of the pn
interface for a zigzag ribbon. In light of these results, we also examine why
higher Ohmic type plateaus are less likely to be observable in experiments.Comment: 9 pages, 6 figure
Precise Distributed Satellite Navigation: Differential GPS with Sensor-Coupling for Integer Ambiguity Resolution
Precise relative navigation is a critical enabler for distributed satellites
to achieve new mission objectives impossible for a monolithic spacecraft.
Carrier phase differential GPS (CDGPS) with integer ambiguity resolution (IAR)
is a promising means of achieving cm-level accuracy for high-precision
Rendezvous, Proximity-Operations and Docking (RPOD), In-Space Servicing,
Assembly and Manufacturing (ISAM) as well as satellite formation flying and
swarming. However, IAR is sensitive to received GPS signal noise, especially
under severe multi-path or high thermal noise. This paper proposes a
sensor-fusion approach to achieve IAR under such conditions in two coupling
stages. A loose coupling stage fuses through an Extended Kalman Filter the
CDGPS measurements with on-board sensor measurements such as range from
cross-links, and vision-based bearing angles. A second tight-coupling stage
augments the cost function of the integer weighted least-squares minimization
with a soft constraint function using noise-weighted observed-minus-computed
residuals from these external sensor measurements. Integer acceptance tests are
empirically modified to reflect added constraints. Partial IAR is applied to
graduate integer fixing. These proposed techniques are packaged into
flight-capable software, with ground truths simulated by the Stanford Space
Rendezvous Laboratory's S3 library using state-of-the-art force modelling with
relevant sources of errors, and validated in two scenarios: (1) a high
multi-path scenario involving rendezvous and docking in low Earth orbit, and
(2) a high thermal noise scenario relying only on GPS side-lobe signals during
proximity operations in geostationary orbit. This study demonstrates successful
IAR in both cases, using the proposed sensor-fusion approach, thus
demonstrating potential for high-precision state estimation under adverse
signal-to-noise conditions.Comment: 15 pages, 20 figures, IEEE AERO 2024 (pre-print
Heterogeneous Nuclear Ribonucleoproteins: Implications in Neurological Diseases
Heterogenous nuclear ribonucleoproteins (hnRNPs) are a complex and functionally diverse family of RNA binding proteins with multifarious roles. They are involved, directly or indirectly, in alternative splicing, transcriptional and translational regulation, stress granule formation, cell cycle regulation, and axonal transport. It is unsurprising, given their heavy involvement in maintaining functional integrity of the cell, that their dysfunction has neurological implications. However, compared to their more established roles in cancer, the evidence of hnRNP implication in neurological diseases is still in its infancy. This review aims to consolidate the evidences for hnRNP involvement in neurological diseases, with a focus on spinal muscular atrophy (SMA), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), multiple sclerosis (MS), congenital myasthenic syndrome (CMS), and fragile X-associated tremor/ataxia syndrome (FXTAS). Understanding more about hnRNP involvement in neurological diseases can further elucidate the pathomechanisms involved in these diseases and perhaps guide future therapeutic advances
The Emergence of a Twisted Flux Tube into the Solar Atmosphere: Sunspot Rotations and the Formation of a Coronal Flux Rope
We present a 3D simulation of the dynamic emergence of a twisted magnetic
flux tube from the top layer of the solar convection zone into the solar
atmosphere and corona. It is found that after a brief initial stage of flux
emergence during which the two polarities of the bipolar region become
separated and the tubes intersecting the photosphere become vertical,
significant rotational motion sets in within each polarity. The rotational
motions of the two polarities are found to twist up the inner field lines of
the emerged fields such that they change their orientation into an inverse
configuration (i.e. pointing from the negative polarity to the positive
polarity over the neutral line). As a result, a flux rope with sigmoid-shaped,
dipped core fields form in the corona, and the center of the flux rope rises in
the corona with increasing velocity as the twisting of the flux rope footpoints
continues. The rotational motion in the two polarities is a result of
propagation of non-linear torsional Alfv\'en waves along the flux tube, which
transports significant twist from the tube's interior portion towards its
expanded coronal portion. This is a basic process whereby twisted flux ropes
are developed in the corona with increasing twist and magnetic energy, leading
up to solar eruptions.Comment: 33 pages, 14 figures, Submitted to Ap
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