11,032 research outputs found
Introducing random walk measures to space syntax
We introduce Random Walk Closeness (RWC) to the space syntax computational paradigm. Random
walks are stochastic processes in which an unbiased walker traverses a network purely based on his
current location. Random walks have been used by space syntax in an agent based scenario, where
results are simulation based. Here, the results are mathematical based, i.e. RWC is derived from
access times, which are the average number of steps it takes to walk between locations. Results
suggest an improvement in correlating pedestrian movement over Integration, RA and network
Closeness
Radio-frequency dressing of multiple Feshbach resonances
We demonstrate and theoretically analyze the dressing of several proximate
Feshbach resonances in Rb-87 using radio-frequency (rf) radiation. We present
accurate measurements and characterizations of the resonances, and the dramatic
changes in scattering properties that can arise through the rf dressing. Our
scattering theory analysis yields quantitative agreement with the experimental
data. We also present a simple interpretation of our results in terms of
rf-coupled bound states interacting with the collision threshold.Comment: 4+ pages, 3 figures, 1 table; revised introduction & references to
reflect published versio
Simulations of a Scintillator Compton Gamma Imager for Safety and Security
We are designing an all-scintillator Compton gamma imager for use in security
investigations and remediation actions involving radioactive threat material.
To satisfy requirements for a rugged and portable instrument, we have chosen
solid scintillator for the active volumes of both the scatter and absorber
detectors. Using the BEAMnrc/EGSnrc Monte Carlo simulation package, we have
constructed models using four different materials for the scatter detector:
LaBr_3, NaI, CaF_2 and PVT. We have compared the detector performances using
angular resolution, efficiency, and image resolution. We find that while PVT
provides worse performance than that of the detectors based entirely on
inorganic scintillators, all of the materials investigated for the scatter
detector have the potential to provide performance adequate for our purposes.Comment: Revised text and figures, Presented at SORMA West 2008, Published in
IEEE Transactions on Nuclear Scienc
Erbium-doped fiber amplifier elements for structural analysis sensors
The use of erbium-doped fiber amplifiers (EDFA's) in optical fiber sensor systems for structural analysis is described. EDFA's were developed for primary applications as periodic regenerator amplifiers in long-distance fiber-based communication systems. Their in-line amplification performance also makes them attractive for optical fiber sensor systems which require long effective lengths or the synthesis of special length-dependent signal processing functions. Sensor geometries incorporating EDFA's in recirculating and multiple loop sensors are discussed. Noise and polarization birefringence are also considered, and the experimental development of system components is discussed
Effects of Force Level and Hand Dominance on Bilateral Transfer of a Fine Motor Skill
Our research is about bilateral transfer, a concept in motor learning where skills
learned by one limb are "transferred", allowing the opposite limb to benefit from what
was learned by the first limb. Previous research into bilateral transfer has raised
questions about whether specific aspects of motor coordination are or are not
transferred. We wanted to see whether learning to control pinch force by the thumb
and index finger is transferable, and if it is, whether the learning transfers equally
from either hand. We also want to look into the effects of different force levels on
the degree of transfer. We designed a task using a program that takes force levels
as inputs and has the participant trace shapes on a screen. By having participants
perform with one hand, then practice with the other, and finally perform again with
the initial hand, we can measure transfer as the difference in performance before
and after practice with the other hand.Kinesiology and Health Educatio
Efficient room temperature cw Yb:glass laser pumped by a 946nm Nd:YAG laser
By pumping with a cw diode-pumped Nd:YAG laser operating at 946nm laser operation of a new Yb-doped phosphate glass with 440mW cw output power and a slope efficiency of 48% with respect to the absorbed pump power was achieved at room temperature
Opportunities of artificial neural network generated VGA: Training a Multilayer Perceptron to recognize the underlying structures of space
This paper presents the research conducted with the aim of understanding if new advances in computer science, more specifically a type of supervised, feedforward Artificial Neural Network, a Multilayer Perceptron (MLP) is able to estimate the values of Visibility Graph Analysis (VGA) without the need for expensive calculation. The overarching hypothesis is that an MLP can be setup in a way that it can be trained to learn the relationship between spatial configuration and the VGA (neighbourhood size and clustering coefficient) derived from it. Two hypotheses are stated: firstly, if such an MLP can be created than it will be able to generate spatial configurations for specific VGA values as inputs (mode A); secondly, the network would be able to generate VGA when presented with spatial configuration faster, compared to current method and with negligible error (mode B). The hypotheses were tested by creating unique setups of an MLP for each mode, all of which had a different configuration. As each combination of possible setups were tested, the performance of the networks could be compared to each other and to the traditional method of VGA calculation. Both mode A and mode B was able to achieve satisfying results that prove that an MLP is able to generate –with limitations- configurations based on VGA input and it is able to calculate the neighbourhood size and the clustering coefficient of a 2D layout substantially faster and with negligible error. All MLPs were created at a generic space, therefore the MLP taught once can be adopted universally to most spaces. The implications of the two systems is that spatial analysis can be integrated into the design process, enabling interactive, instant analysis and the possible deployment of optimisation procedures, for instance a Genetic Algorithm
A coherent triggered search for single spin compact binary coalescences in gravitational wave data
In this paper we present a method for conducting a coherent search for single
spin compact binary coalescences in gravitational wave data and compare this
search to the existing coincidence method for single spin searches. We propose
a method to characterize the regions of the parameter space where the single
spin search, both coincident and coherent, will increase detection efficiency
over the existing non-precessing search. We also show example results of the
coherent search on a stretch of data from LIGO's fourth science run but note
that a set of signal based vetoes will be needed before this search can be run
to try to make detections.Comment: 14 pages, 4 figure
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