8,840 research outputs found
The Sunyaev Zel'dovich effect: simulation and observation
The Sunyaev Zel'dovich effect (SZ effect) is a complete probe of ionized
baryons, the majority of which are likely hiding in the intergalactic medium.
We ran a CDM simulation using a moving mesh hydro code to
compute the statistics of the thermal and kinetic SZ effect such as the power
spectra and measures of non-Gaussianity. The thermal SZ power spectrum has a
very broad peak at multipole with temperature fluctuations
K. The power spectrum is consistent with available
observations and suggests a high and a possible role of
non-gravitational heating. The non-Gaussianity is significant and increases the
cosmic variance of the power spectrum by a factor of for .
We explore optimal driftscan survey strategies for the AMIBA CMB
interferometer and their dependence on cosmology. For SZ power spectrum
estimation, we find that the optimal sky coverage for a 1000 hours of
integration time is several hundred square degrees. One achieves an accuracy
better than 40% in the SZ measurement of power spectrum and an accuracy better
than 20% in the cross correlation with Sloan galaxies for . For
cluster searches, the optimal scan rate is around 280 hours per square degree
with a cluster detection rate 1 every 7 hours, allowing for a false positive
rate of 20% and better than 30% accuracy in the cluster SZ distribution
function measurement.Comment: 34 pages, 20 figures. Submitted to ApJ. Simulation maps have been
replaced by high resolution images. For higher resolution color images,
please download from http://www.cita.utoronto.ca/~zhangpj/research/SZ/ We
corrected a bug in our analysis. the SZ power spectrum decreases 50% and y
parameter decrease 25
Tripartite Graph Clustering for Dynamic Sentiment Analysis on Social Media
The growing popularity of social media (e.g, Twitter) allows users to easily
share information with each other and influence others by expressing their own
sentiments on various subjects. In this work, we propose an unsupervised
\emph{tri-clustering} framework, which analyzes both user-level and tweet-level
sentiments through co-clustering of a tripartite graph. A compelling feature of
the proposed framework is that the quality of sentiment clustering of tweets,
users, and features can be mutually improved by joint clustering. We further
investigate the evolution of user-level sentiments and latent feature vectors
in an online framework and devise an efficient online algorithm to sequentially
update the clustering of tweets, users and features with newly arrived data.
The online framework not only provides better quality of both dynamic
user-level and tweet-level sentiment analysis, but also improves the
computational and storage efficiency. We verified the effectiveness and
efficiency of the proposed approaches on the November 2012 California ballot
Twitter data.Comment: A short version is in Proceeding of the 2014 ACM SIGMOD International
Conference on Management of dat
The conduciveness of CA-rule graphs
Given two subsets A and B of nodes in a directed graph, the conduciveness of
the graph from A to B is the ratio representing how many of the edges outgoing
from nodes in A are incoming to nodes in B. When the graph's nodes stand for
the possible solutions to certain problems of combinatorial optimization,
choosing its edges appropriately has been shown to lead to conduciveness
properties that provide useful insight into the performance of algorithms to
solve those problems. Here we study the conduciveness of CA-rule graphs, that
is, graphs whose node set is the set of all CA rules given a cell's number of
possible states and neighborhood size. We consider several different edge sets
interconnecting these nodes, both deterministic and random ones, and derive
analytical expressions for the resulting graph's conduciveness toward rules
having a fixed number of non-quiescent entries. We demonstrate that one of the
random edge sets, characterized by allowing nodes to be sparsely interconnected
across any Hamming distance between the corresponding rules, has the potential
of providing reasonable conduciveness toward the desired rules. We conjecture
that this may lie at the bottom of the best strategies known to date for
discovering complex rules to solve specific problems, all of an evolutionary
nature
Charge renormalization and phase separation in colloidal suspensions
We explore the effects of counterion condensation on fluid-fluid phase
separation in charged colloidal suspensions. It is found that formation of
double layers around the colloidal particles stabilizes suspensions against
phase separation. Addition of salt, however, produces an instability which, in
principle, can lead to a fluid-fluid separation. The instability, however, is
so weak that it should be impossible to observe a fully equilibrated
coexistence experimentally.Comment: 7 pages, Europhysics Letters (in press
Indexação de plantas básicas de citros da Embrapa Mandioca e Fruticultura para a presença de viróides.
Os citros são hospedeiros naturais de espécies de viróides: viróide da exocorte dos citros (Citrus exocortis viroid, CEVd), viróide do nanismo do lúpulo (Hop stunt viroid, HSVd), Citrus bark cracking viroid (CBCVd), viróide da folha curvada dos citros (Citrus bent leaf viroid, CBLVd), viróide do nanismo dos citros (Citrus dwarfing viroid, CDVd) e, mais recentemente, também foi descrita a ocorrência do Citrus Viroid V (CVd-V) e Citrus viroid VI (CVd-VI). Somente o CEVd e variantes do HSVd são agentes causais de doenças, exocorte e xiloporose, respectivamente. No Brasil já foram identificados as espécies CEVd, HSVd e o CDVd
Study of the Van der Pol Oscillator with Fractional Derivatives
In this paper we propose a modified version of the classical Van der Pol oscillator by introducing fractional-order time derivatives into the state-space model. The resulting fractional-order Van der Pol oscillator is analyzed in the time and frequency domains, by using phase portraits, spectral analysis and bifurcation diagrams. The fractional-order dynamics is illustrated through numerical simulations of the proposed schemes by using approximations to fractional-order operators. Finally, the analysis is extended to the forced Van der Pol oscillator.N/
Análise do potencial alelopático de Luehea divaricata L. sobre o peso de raízes de capim-annoni.
EVALUATION OF ACCIDENTS WITH DOMINO EFFECT IN LPG STORAGE AREAS
The term domino effect denotes a chain of accidents, or situations, in which a fire/explosion
load generated by an accident in one unit in an industry causes secondary and higher order
accidents in other units. Such chains of accidents have a greater propensity to cause damage
than stand-alone accidents. Most of the past risk assessment studies deal with accident in
a single industry, more so in one of the units of an industry. But, often, accident in one unit
causes a secondary accident in a nearby unit, which in turn may trigger a tertiary accident,
and so on. The probability of occurrence and adverse impacts of such domino or
cascading effects are increasing due to increasing congestion in industrial complexes
and increasing density of human population around such complexes. Accidents with domino
effect are seldom studied. LPG storage areas could produce the worst possible consequences
in the event of an unforeseen incident. This work illustrates the application of models to
evaluate the impacts of events with fire and explosion in LPG tanks on other similar units
in the park and the possibility of occurrence of a domino effect. The criteria for occurrence
of accidents with domino effect adopted in this work were 37.5 kW/m2 in case of fire
radiation and an overpressure of 0.7 atm in explosion cases in a receptor body. The spacing
between LPG tanks was evaluated. The results show that such spacing is minimal and
does not represent, as it should, a parameter indicating a safe distance able to prevent the
propagation of an accident with domino effect
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