1,613 research outputs found
New SETI Sky Surveys for Radio Pulses
Berkeley conducts 7 SETI programs at IR, visible and radio wavelengths. Here
we review two of the newest efforts, Astropulse and Fly's Eye.
A variety of possible sources of microsecond to millisecond radio pulses have
been suggested in the last several decades, among them such exotic events as
evaporating primordial black holes, hyper-flares from neutron stars, emissions
from cosmic strings or perhaps extraterrestrial civilizations, but to-date few
searches have been conducted capable of detecting them.
We are carrying out two searches in hopes of finding and characterizing these
mu-s to ms time scale dispersed radio pulses. These two observing programs are
orthogonal in search space; the Allen Telescope Array's (ATA) "Fly's Eye"
experiment observes a 100 square degree field by pointing each 6m ATA antenna
in a different direction; by contrast, the Astropulse sky survey at Arecibo is
extremely sensitive but has 1/3,000 of the instantaneous sky coverage.
Astropulse's multibeam data is transferred via the internet to the computers of
millions of volunteers. These computers perform a coherent de-dispersion
analysis faster than the fastest available supercomputers and allow us to
resolve pulses as short as 400 ns. Overall, the Astropulse survey will be 30
times more sensitive than the best previous searches. Analysis of results from
Astropulse is at a very early stage.
The Fly's Eye was successfully installed at the ATA in December of 2007, and
to-date approximately 450 hours of observation has been performed. We have
detected three pulsars and six giant pulses from the Crab pulsar in our
diagnostic pointing data. We have not yet detected any other convincing bursts
of astronomical origin in our survey data. (Abridged)Comment: 9 pages, 6 figures, Accepted to Acta Astronautica "Special Issue:
Life Signatures
Advanced engineering - Communications systems research
Communications systems research on information systems and on digital telemetry and command in Deep Space Networ
Sixth Annual Users' Conference
Conference papers and presentation outlines which address the use of the Transportable Applications Executive (TAE) and its various applications programs are compiled. Emphasis is given to the design of the user interface and image processing workstation in general. Alternate ports of TAE and TAE subsystems are also covered
Viaduct : an interactive, very-high-level data manipulation language for a microcomputer-based database system.
Bibliography: leaves 203-210.A very-high-level data manipulation language for a database system is one in which the user specifies in non-procedural terms the operations that are to be performed on the data stored in the database; the actual method by which the operations are executed does not concern the user. VIADUCT provides such an interface to a microcomputer-based database system known as MDBS. Thus VIADUCT allows a microcomputer user lacking in computer sophistication to interact with, and derive the benefits of, a powerful database management system. Additional security restrictions and integrity constraints usually found only on mainframe database management systems are provided by VIADUCT through the mechanism of a subschema generator
Fast Radio Bursts
The discovery of radio pulsars over a half century ago was a seminal moment
in astronomy. It demonstrated the existence of neutron stars, gave a powerful
observational tool to study them, and has allowed us to probe strong gravity,
dense matter, and the interstellar medium. More recently, pulsar surveys have
led to the serendipitous discovery of fast radio bursts (FRBs). While FRBs
appear similar to the individual pulses from pulsars, their large dispersive
delays suggest that they originate from far outside the Milky Way and hence are
many orders-of-magnitude more luminous. While most FRBs appear to be one-off,
perhaps cataclysmic events, two sources are now known to repeat and thus
clearly have a longer-lived central engine. Beyond understanding how they are
created, there is also the prospect of using FRBs -- as with pulsars -- to
probe the extremes of the Universe as well as the otherwise invisible
intervening medium. Such studies will be aided by the high implied all-sky
event rate: there is a detectable FRB roughly once every minute occurring
somewhere on the sky. The fact that less than a hundred FRB sources have been
discovered in the last decade is largely due to the small fields-of-view of
current radio telescopes. A new generation of wide-field instruments is now
coming online, however, and these will be capable of detecting multiple FRBs
per day. We are thus on the brink of further breakthroughs in the
short-duration radio transient phase space, which will be critical for
differentiating between the many proposed theories for the origin of FRBs. In
this review, we give an observational and theoretical introduction at a level
that is accessible to astronomers entering the field.Comment: Invited review article for The Astronomy and Astrophysics Revie
Fast Radio Bursts
The discovery of radio pulsars over a half century ago was a seminal moment
in astronomy. It demonstrated the existence of neutron stars, gave a powerful
observational tool to study them, and has allowed us to probe strong gravity,
dense matter, and the interstellar medium. More recently, pulsar surveys have
led to the serendipitous discovery of fast radio bursts (FRBs). While FRBs
appear similar to the individual pulses from pulsars, their large dispersive
delays suggest that they originate from far outside the Milky Way and hence are
many orders-of-magnitude more luminous. While most FRBs appear to be one-off,
perhaps cataclysmic events, two sources are now known to repeat and thus
clearly have a longer-lived central engine. Beyond understanding how they are
created, there is also the prospect of using FRBs -- as with pulsars -- to
probe the extremes of the Universe as well as the otherwise invisible
intervening medium. Such studies will be aided by the high implied all-sky
event rate: there is a detectable FRB roughly once every minute occurring
somewhere on the sky. The fact that less than a hundred FRB sources have been
discovered in the last decade is largely due to the small fields-of-view of
current radio telescopes. A new generation of wide-field instruments is now
coming online, however, and these will be capable of detecting multiple FRBs
per day. We are thus on the brink of further breakthroughs in the
short-duration radio transient phase space, which will be critical for
differentiating between the many proposed theories for the origin of FRBs. In
this review, we give an observational and theoretical introduction at a level
that is accessible to astronomers entering the field.Comment: Invited review article for The Astronomy and Astrophysics Revie
Contributions to the development of an integrated toolbox of solvers in Derivative-Free Optimization
This dissertation is framed on the ongoing research project BoostDFO - Improving
the performance and moving to newer dimensions in Derivative-Free Optimization. The final
goal of this project is to develop efficient and robust algorithms for Global and/or
Multiobjective Derivative-free Optimization. This type of optimization is typically required
in complex scientific/industrial applications, where the function evaluation is
time-consuming and derivatives are not available for use, neither can be numerically
approximated. Often problems present several conflicting objectives or users aspire to
obtain global solutions.
Inspired by successful approaches used in single objective local Derivative-free Optimization,
we intend to address the inherent problem of the huge execution times by
resorting to parallel/cloud computing and carrying a detailed performance analysis. As
result, an integrated toolbox for solving single/multi objective, local/global Derivativefree
Optimization problems is made available, with recommendations for taking advantage
of parallelization and cloud computing, providing easy access to several efficient and
robust algorithms and allowing to tackle harder Derivative-free Optimization problems.Esta dissertação insere-se no projecto científico BoostDFO - Improving the performance
and moving to newer dimensions in Derivative-Free Optimization. O objectivo final desta
investigação é desenvolver algoritmos robustos e eficientes para problemas de Optimização
Sem Derivadas Globais e/ou Multiobjectivo. Este tipo de optimização é tipicamente
requerido em aplicações científicas/industriais complexas, onde a avaliação da função é
bastante demorada e as derivadas não se encontram disponíveis, nem podem ser aproximadas
numericamente. Os problemas apresentam frequentemente vários objectivos
divergentes ou os utilizadores procuram obter soluções globais.
Tendo por base abordagens prévias bem-sucedidas utilizadas em Optimização Sem
Derivadas local e uniobjectivo, pretende-se abordar o problema inerente aos grandes tempos
de execução, recorrendo ao paralelismo/computação em cloud e efectuando uma
detalhada análise de desempenho. Como resultado, é disponibilizada uma ferramenta
integrada destinada a problemas de Optimização Sem Derivadas uni/multiobjectivo, com
optimização local/global, incluindo recomendações que permitam tirar partido do paralelismo
e computação em cloud, facilitando o acesso a vários algoritmos robustos e eficientes
e permitindo abordar problemas mais difíceis nesta classe
Distributed multimedia systems
A distributed multimedia system (DMS) is an integrated communication, computing, and information system that enables the processing, management, delivery, and presentation of synchronized multimedia information with quality-of-service guarantees. Multimedia information may include discrete media data, such as text, data, and images, and continuous media data, such as video and audio. Such a system enhances human communications by exploiting both visual and aural senses and provides the ultimate flexibility in work and entertainment, allowing one to collaborate with remote participants, view movies on demand, access on-line digital libraries from the desktop, and so forth. In this paper, we present a technical survey of a DMS. We give an overview of distributed multimedia systems, examine the fundamental concept of digital media, identify the applications, and survey the important enabling technologies.published_or_final_versio
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