3,160 research outputs found
Performance Analysis of PCFICH and PDCCH LTE Control Channels
Control channels play a key role in the evaluation of mobile system performance. The purpose of our paper is to evaluate the performance of the control channels implementation in the Long Term Evolution (LTE) system. The paper deals with the simulation of the complete signal processing chain for Physical Control Format Indicator Channel (PCFICH) and Physical Downlink Control Channel (PDCCH) in the LTE system, Release 8. We implemented a complete signal processing chain for downlink control channels as an extension of the existing MATLAB LTE downlink simulator. The paper presents results of PCFICH and PDCCH control channel computer performance analysis in various channel conditions. The results can be compared with the performance of data channels
Aspherical Core-Collapse Supernovae in Red Supergiants Powered by Nonrelativistic Jets
We explore the observational characteristics of jet-driven supernovae by
simulating bipolar-jet-driven explosions in a red supergiant progenitor. We
present results of four models in which we hold the injected kinetic energy at
a constant ergs across all jet models but vary the specific
characteristics of the jets to explore the influence of the nature of jets on
the structure of the supernova ejecta. We evolve the explosions past
shock-breakout and into quasi-homologous expansion of the supernova envelope
into a red supergiant wind. The oppositely-directed, nickel-rich jets give a
large-scale asymmetry that may account for the non-spherical excitation and
substructure of spectral lines such as H and He I 10830\AA. Jets with a
large fraction of kinetic to thermal energy punch through the progenitor
envelope and give rise to explosions that would be observed to be asymmetric
from the earliest epochs, inconsistent with spectropolarimetric measurements of
Type II supernovae. Jets with higher thermal energy fractions result in
explosions that are roughly spherical at large radii but are significantly
elongated at smaller radii, deep inside the ejecta, in agreement with the
polarimetric observations. We present shock breakout light curves that indicate
that strongly aspherical shock breakouts are incompatible with recent {\it
GALEX} observations of shock breakout from red supergiant stars. Comparison
with observations indicates that jets must deposit their kinetic energy
efficiently throughout the ejecta while in the hydrogen envelope. Thermal
energy-dominated jets satisfy this criterion and yield many of the
observational characteristics of Type II supernovae.Comment: 21 pages, 19 figures, submitted to ApJ on 4 Nov 200
Influences the Aeromath in the Way of Ending Births
Air pollution represents a significant health problem in the Czech Republic (CR). Originally, the most polluted region was Northern Bohemia, later Northern Moravia. These specific conditions were used to study the impact of air pollution to children in those two regions. In Northern Bohemia, the impact of the increased concentrations of carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) to fetal growth was observed, expressed as intrauterine growth retardation and impact of air pollution to respiratory morbidity and neurodevelopment in children. In Northern Moravia was studied the effect of air pollution to the morbidity of preschool children; to asthma bronchiale—gene expression, children susceptibility to benzo[a]pyrene (B[a]P); to genetic damage in newborns; concentrations of PAHs in the urine of mothers and newborns, content of PAHs in human breast milk and diet
Post-Flight Evaluation of Stardust PICA Forebody Heatshield Material
This presentation was part of the session : Sample Return ChallengesSixth International Planetary Probe WorkshopPhenolic Impregnated Carbon Ablator (PICA) was developed at NASA Ames Research Center under the lightweight ceramic ablator development program in the '80s. PICA has the advantages of low density (~ 0.27g/cc) coupled with efficient ablative capability at high heat fluxes making PICA an enabling technology for the Stardust mission. Three cores at key locations were extracted from the forebody heatshield of the Stardust Sample Return Capsule (SRC) post flight and evaluated. Core locations include a near stagnation core, a flank core and a segment taken from the shoulder of the heatshield. Evaluation included density profiles, recession determination, thermal analysis profile, PICA bondline examination, strength of remaining virgin PICA, emissivity profile, chemical analysis profile and microstructural analysis. Comparisons between experimental density profiles and profiles derived from FIAT, a tool used to predict ablative performance, are in good agreement. Recession comparisons from measured values and FIAT predictions are currently being obtained. In addition a laser scanning tool developed at ARC is being used to evaluate recession measurements and compare to experimental and predicted values. In general, the PICA material examined in the cores is in good condition and intact. Impact damage is not evident and the main degradation observed was that caused by heating on entry. A substantial amount of "virgin" PICA was present in all cores examined. It is noted that the post-flight analysis of the Stardust heat shield is especially important since PICA is baselined for both the Orion (CEV) and Mars Science Laboratory vehicles.NASA; NESC; Orion Thermal Protection System Advanced Development Projec
Optical addressing of an individual erbium ion in silicon
The detection of electron spins associated with single defects in solids is a
critical operation for a range of quantum information and measurement
applications currently under development. To date, it has only been
accomplished for two centres in crystalline solids: phosphorus in silicon using
electrical readout based on a single electron transistor (SET) and
nitrogen-vacancy centres in diamond using optical readout. A spin readout
fidelity of about 90% has been demonstrated with both electrical readout and
optical readout, however, the thermal limitations of the electrical readout and
the poor photon collection efficiency of the optical readout hinder achieving
the high fidelity required for quantum information applications. Here we
demonstrate a hybrid approach using optical excitation to change the charge
state of the defect centre in a silicon-based SET, conditional on its spin
state, and then detecting this change electrically. The optical frequency
addressing in high spectral resolution conquers the thermal broadening
limitation of the previous electrical readout and charge sensing avoids the
difficulties of efficient photon collection. This is done with erbium in
silicon and has the potential to enable new architectures for quantum
information processing devices and to dramatically increase the range of defect
centres that can be exploited. Further, the efficient electrical detection of
the optical excitation of single sites in silicon is a major step in developing
an interconnect between silicon and optical based quantum computing
technologies.Comment: Corrected the third affiliation. Corrected one cross-reference of
"Fig. 3b" to "Fig. 3c". Corrected the caption of Fig. 3a by changing (+-)1 to
Design and prototype of a train-to-wayside communication architecture
Telecommunication has become very important in modern society and seems to be almost omnipresent, making daily life easier, more pleasant and connecting people everywhere. It does not only connect people, but also machines, enhancing the efficiency of automated tasks and monitoring automated processes. In this context the IBBT (Interdisciplinary Institute for BroadBand Technology) project TRACK (TRain Applications over an advanced Communication networK), sets the definition and prototyping of an end-to-end train-to-wayside communication architecture as one of the main research goals. The architecture provides networking capabilities for train monitoring, personnel applications and passenger Internet services. In the context of the project a prototype framework was developed to give a complete functioning demonstrator. Every aspect: tunneling and mobility, performance enhancements, and priority and quality of service were taken into consideration. In contrast to other research in this area, which has given mostly high-level overviews, TRACK resulted in a detailed architecture with all different elements present
Associating Natural Language Comment and Source Code Entities
Comments are an integral part of software development; they are natural
language descriptions associated with source code elements. Understanding
explicit associations can be useful in improving code comprehensibility and
maintaining the consistency between code and comments. As an initial step
towards this larger goal, we address the task of associating entities in
Javadoc comments with elements in Java source code. We propose an approach for
automatically extracting supervised data using revision histories of open
source projects and present a manually annotated evaluation dataset for this
task. We develop a binary classifier and a sequence labeling model by crafting
a rich feature set which encompasses various aspects of code, comments, and the
relationships between them. Experiments show that our systems outperform
several baselines learning from the proposed supervision.Comment: Accepted in AAAI 202
The ACS Virgo Cluster Survey II. Data Reduction Procedures
The ACS Virgo Cluster Survey is a large program to carry out multi-color
imaging of 100 early-type members of the Virgo Cluster using the Advanced
Camera for Surveys (ACS) on the Hubble Space Telescope. Deep F475W and F850LP
images (~ SDSS g and z) are being used to study the central regions of the
program galaxies, their globular cluster systems, and the three-dimensional
structure of Virgo itself. In this paper, we describe in detail the data
reduction procedures used for the survey, including image registration,
drizzling strategies, the computation of weight images, object detection, the
identification of globular cluster candidates, and the measurement of their
photometric and structural parameters.Comment: 33 pages, 8 figures. Accepted for publication in ApJS. Also available
at http://www.physics.rutgers.edu/~pcote/acs/publications.htm
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