3,135 research outputs found
Computational Public Safety in Emergency Management Communications
Communications are very important in any situation but in emergency management it is imperative that the communications be reliable and responsive to the evolving situation. In emergency management there are many different types of networks with different objectives. It is of immense value to have the ability to seamlessly integrate other networks and computing resources into one interconnected heterogeneous network. The entire management team should be able to access any of the individual networks and their resources. In this paper we discuss various wireless network communication options in the context of their viability for use in emergency management. We analyze various technical aspects such as propagation delay, packet delivery ratio, and transmission rates. In addition the environmental conditions that impair communications are discussed. All experiments we conducted took place in a setting that was real, using real equipment that was physically situated in settings that can be expected in urban disaster settings—our results are not simulations. They were performed in cooperation with the Ontario Provincial Police, Provincial Emergency Response Tea
Cross Layer Design for Wi-Fi Sensor Network Handling Static and Dynamic Environment Using Local Automate Based Autonomic Network Architecture
In social activities with shared Wi-Fi needs to accommodate large number of users and effectively handle congestion. These are critical issues due to the presence of larger density nodal activity at nearby access points involving inter-technology interference. An interference involves a statistical approach in monitoring access points with its received errors. The received errors vary with frame reception at their fields like PHY, MAC headers and payloads. Local automate-based Autonomic Network Architecture a cross layer approach algorithm is proposed to channelize a frame reception and can effectively avoid inter-technology interference. This results in P2P communication at initial stages and can accommodate multiple mobile devices with varying signal strengths. The algorithm is deployed for a dynamic environment along with static clusters. The throughput of the entire network is increased by 20% because of
Performance of the Gemini Planet Imager Non-Redundant Mask and spectroscopy of two close-separation binaries HR 2690 and HD 142527
The Gemini Planet Imager (GPI) contains a 10-hole non-redundant mask (NRM),
enabling interferometric resolution in complement to its coronagraphic
capabilities. The NRM operates both in spectroscopic (integral field
spectrograph, henceforth IFS) and polarimetric configurations. NRM observations
were taken between 2013 and 2016 to characterize its performance. Most
observations were taken in spectroscopic mode with the goal of obtaining
precise astrometry and spectroscopy of faint companions to bright stars. We
find a clear correlation between residual wavefront error measured by the AO
system and the contrast sensitivity by comparing phase errors in observations
of the same source, taken on different dates. We find a typical 5-
contrast sensitivity of at . We explore the
accuracy of spectral extraction of secondary components of binary systems by
recovering the signal from a simulated source injected into several datasets.
We outline data reduction procedures unique to GPI's IFS and describe a newly
public data pipeline used for the presented analyses. We demonstrate recovery
of astrometry and spectroscopy of two known companions to HR 2690 and HD
142527. NRM+polarimetry observations achieve differential visibility precision
of in the best case. We discuss its limitations on
Gemini-S/GPI for resolving inner regions of protoplanetary disks and prospects
for future upgrades. We summarize lessons learned in observing with NRM in
spectroscopic and polarimetric modes.Comment: Accepted to AJ, 22 pages, 14 figure
Supporting Large Scale Communication Systems on Infrastructureless Networks Composed of Commodity Mobile Devices: Practicality, Scalability, and Security.
Infrastructureless Delay Tolerant Networks (DTNs) composed of
commodity mobile devices have the potential to support communication
applications resistant to blocking and censorship, as well as certain
types of surveillance. In this thesis we study the utility,
practicality, robustness, and security of these networks.
We collected two sets of wireless connectivity traces of commodity
mobile devices with different granularity and scales.
The first dataset is collected through active installation of
measurement software on volunteer users' own smartphones, involving 111 users of a DTN microblogging application that we developed. The second dataset is collected through passive observation of WiFi association
events on a university campus, involving 119,055 mobile devices.
Simulation results show consistent message delivery performances of the
two datasets. Using an epidemic flooding protocol, the large network
achieves an average delivery rate of 0.71 in 24 hours and a median delivery delay of 10.9 hours. We show that this performance is appropriate for sharing information that is not time sensitive, e.g., blogs and photos. We also show that using an energy efficient variant of the epidemic flooding protocol, even the large network can support text messages while only consuming 13.7% of a typical smartphone battery in 14 hours.
We found that the network delivery rate and delay are robust to
denial-of-service and censorship attacks. Attacks that randomly remove
90% of the network participants only reduce delivery rates by less than 10%. Even when subjected to targeted attacks, the network suffered a less than 10% decrease in delivery rate when 40% of its participants were removed.
Although structurally robust, the openness of the proposed network
introduces numerous security concerns. The Sybil attack, in
which a malicious node poses as many identities in order to gain
disproportionate influence, is especially dangerous as it breaks the assumption underlying majority voting. Many defenses based on spatial variability of wireless channels exist, and we extend them to be practical for ad hoc networks of commodity 802.11 devices without mutual trust. We present the Mason test, which uses two efficient methods for separating valid channel measurement results of behaving nodes from those falsified by malicious participants.PhDElectrical Engineering: SystemsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120779/1/liuyue_1.pd
Unveiling the Dynamics of the Universe
We explore the dynamics and evolution of the Universe at early and late
times, focusing on both dark energy and extended gravity models and their
astrophysical and cosmological consequences. Modified theories of gravity not
only provide an alternative explanation for the recent expansion history of the
universe, but they also offer a paradigm fundamentally distinct from the
simplest dark energy models of cosmic acceleration. In this review, we perform
a detailed theoretical and phenomenological analysis of different modified
gravity models and investigate their consistency. We also consider the
cosmological implications of well motivated physical models of the early
universe with a particular emphasis on inflation and topological defects.
Astrophysical and cosmological tests over a wide range of scales, from the
solar system to the observable horizon, severely restrict the allowed models of
the Universe. Here, we review several observational probes -- including
gravitational lensing, galaxy clusters, cosmic microwave background temperature
and polarization, supernova and baryon acoustic oscillations measurements --
and their relevance in constraining our cosmological description of the
Universe.Comment: 94 pages, 14 figures. Review paper accepted for publication in a
Special Issue of Symmetry. "Symmetry: Feature Papers 2016". V2: Matches
published version, now 79 pages (new format
Nonlinear tube-fitting for the analysis of anatomical and functional structures
We are concerned with the estimation of the exterior surface and interior
summaries of tube-shaped anatomical structures. This interest is motivated by
two distinct scientific goals, one dealing with the distribution of HIV
microbicide in the colon and the other with measuring degradation in
white-matter tracts in the brain. Our problem is posed as the estimation of the
support of a distribution in three dimensions from a sample from that
distribution, possibly measured with error. We propose a novel tube-fitting
algorithm to construct such estimators. Further, we conduct a simulation study
to aid in the choice of a key parameter of the algorithm, and we test our
algorithm with validation study tailored to the motivating data sets. Finally,
we apply the tube-fitting algorithm to a colon image produced by single photon
emission computed tomography (SPECT) and to a white-matter tract image produced
using diffusion tensor imaging (DTI).Comment: Published in at http://dx.doi.org/10.1214/10-AOAS384 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Constraining High Redshift X-ray Sources with Next Generation 21 cm Power Spectrum Measurements
We use the Fisher matrix formalism and semi-numerical simulations to derive
quantitative predictions of the constraints that power spectrum measurements on
next-generation interferometers, such as the Hydrogen Epoch of Reionization
Array (HERA) and the Square Kilometre Array (SKA), will place on the
characteristics of the X-ray sources that heated the high redshift
intergalactic medium. Incorporating observations between and , we
find that the proposed 331 element HERA and SKA phase 1 will be capable of
placing constraints on the spectral properties of these first
X-ray sources, even if one is unable to perform measurements within the
foreground contaminated "wedge" or the FM band. When accounting for the
enhancement in power spectrum amplitude from spin temperature fluctuations, we
find that the observable signatures of reionization extend well beyond the peak
in the power spectrum usually associated with it. We also find that lower
redshift degeneracies between the signatures of heating and reionization
physics lead to errors on reionization parameters that are significantly
greater than previously predicted. Observations over the heating epoch are able
to break these degeneracies and improve our constraints considerably. For these
two reasons, 21\,cm observations during the heating epoch significantly enhance
our understanding of reionization as well.Comment: 15 pages, 10 figures, Accepted to MNRA
Viral Quasispecies Reconstruction Using Next Generation Sequencing Reads
The genomic diversity of viral quasispecies is a subject of great interest, especially for chronic infections. Characterization of viral diversity can be addressed by high-throughput sequencing technology (454 Life Sciences, Illumina, SOLiD, Ion Torrent, etc.). Standard assembly software was originally designed for single genome assembly and cannot be used to assemble and estimate the frequency of closely related quasispecies sequences.
This work focuses on parsimonious and maximum likelihood models for assembling viral quasispecies and estimating their frequencies from 454 sequencing data. Our methods have been applied to several RNA viruses (HCV, IBV) as well as DNA viruses (HBV), genotyped using 454 Life Sciences amplicon and shotgun methods
Design study of an earthquake rescue robot
This thesis describes the design of a brush robot for earthquake rescue and for traversing pipes with varied cross sectional shape. Earthquake rescue is a very dangerous, difficult and challenging task, in which emergency services rescue people who are trapped in man-made structures, such as collapsed buildings after an earthquake. The building collapse may have been caused by natural or man-made events. This technology is also applicable to tunnel collapse and land slips. The focus of this work is finding the location of victims and provision of primary life support and communications. To illustrate the concept of the robot, the thesis first discusses the current development of rescue robots and pipe robots. Then the thesis focuses on the description of a brush based pipe robot, developed by the University of Durham, which would be used as the basis of an earthquake rescue robot. The concept of the robot was illustrated and compared with other current rescue robots and pipe robots. After outlining the advantages of this robot concept, a robot body shape change theory was proposed and theoretical simulations were used to verily the practicality of the robot shape change theory. The thesis also illustrates the design of the working principle and design of a robot sensor, which was subsequently used in the robot shape change experiments. The robot body shape change experiments and the experimental results are described and discussed. The experimental results illustrate the robot concept and support the robot body shape change theory. Chapter 6 focuses on the brush unit traction investigation, bristle theory and mathematical model. Furthermore, the bristle theory and mathematical model were used to explain the variation of traction force in the traction experiments
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