33,318 research outputs found
Low power techniques for video compression
This paper gives an overview of low-power techniques proposed in the literature for mobile multimedia and Internet applications. Exploitable aspects are discussed in the behavior of different video compression tools. These power-efficient solutions are then classified by synthesis domain and level of abstraction. As this paper is meant to be a starting point for further research in the area, a lowpower hardware & software co-design methodology is outlined in the end as a possible scenario for video-codec-on-a-chip implementations on future mobile multimedia platforms
Towards the design of a platform for abuse detection in OSNs using multimedial data analysis
Online social networks (OSNs) are becoming increasingly popular every day. The vast amount of data created by users and their actions yields interesting opportunities, both socially and economically. Unfortunately, these online communities are prone to abuse and inappropriate behaviour such as cyber bullying. For victims, this kind of behaviour can lead to depression and other severe problems. However, due to the huge amount of users and data it is impossible to manually check all content posted on the social network. We propose a pluggable architecture with reusable components, able to quickly detect harmful content. The platform uses text-, image-, audio- and video-based analysis modules to detect inappropriate content or high risk behaviour. Domain services aggregate this data and flag user profiles if necessary. Social network moderators need only check the validity of the flagged profiles. This paper reports upon key requirements of the platform, the architectural components and important challenges
Using MCD-DVS for dynamic thermal management performance improvement
With chip temperature being a major hurdle in microprocessor design, techniques to recover the performance loss due to thermal emergency mechanisms are crucial in order to sustain performance growth. Many techniques for power reduction in the past and some on thermal management more recently have contributed to alleviate this problem. Probably the most important thermal control technique is dynamic voltage and frequency scaling (DVS) which allows for almost cubic reduction in power with worst-case performance penalty only linear. So far, DVS techniques for temperature control have been studied at the chip level. Finer grain DVS is feasible if a globally-asynchronous locally-synchronous (GALS) design style is employed. GALS, also known as multiple-clock domain (MCD), allows for an independent voltage and frequency control for each one of the clock domains that are part of the chip. There are several studies on DVS for GALS that aim to improve energy and power efficiency but not temperature. This paper proposes and analyses the usage of DVS at the domain level to control temperature in a clustered MCD microarchitecture with the goal of improving the performance of applications that do not meet the thermal constraints imposed by the designers.Peer ReviewedPostprint (published version
Five new real-time detections of Fast Radio Bursts with UTMOST
We detail a new fast radio burst (FRB) survey with the Molonglo Radio
Telescope, in which six FRBs were detected between June 2017 and December 2018.
By using a real-time FRB detection system, we captured raw voltages for five of
the six events, which allowed for coherent dedispersion and very high time
resolution (10.24 s) studies of the bursts. Five of the FRBs show temporal
broadening consistent with interstellar and/or intergalactic scattering, with
scattering timescales ranging from 0.16 to 29.1 ms. One burst, FRB181017, shows
remarkable temporal structure, with 3 peaks each separated by 1 ms. We searched
for phase-coherence between the leading and trailing peaks and found none,
ruling out lensing scenarios. Based on this survey, we calculate an all-sky
rate at 843 MHz of events sky day to a fluence
limit of 8 Jy-ms: a factor of 7 below the rates estimated from the Parkes and
ASKAP telescopes at 1.4 GHz assuming the ASKAP-derived spectral index
(). Our results suggest that FRB
spectra may turn over below 1 GHz. Optical, radio and X-ray followup has been
made for most of the reported bursts, with no associated transients found. No
repeat bursts were found in the survey.Comment: 13 pages, 11 figures, submitted to MNRA
Extreme Scale De Novo Metagenome Assembly
Metagenome assembly is the process of transforming a set of short,
overlapping, and potentially erroneous DNA segments from environmental samples
into the accurate representation of the underlying microbiomes's genomes.
State-of-the-art tools require big shared memory machines and cannot handle
contemporary metagenome datasets that exceed Terabytes in size. In this paper,
we introduce the MetaHipMer pipeline, a high-quality and high-performance
metagenome assembler that employs an iterative de Bruijn graph approach.
MetaHipMer leverages a specialized scaffolding algorithm that produces long
scaffolds and accommodates the idiosyncrasies of metagenomes. MetaHipMer is
end-to-end parallelized using the Unified Parallel C language and therefore can
run seamlessly on shared and distributed-memory systems. Experimental results
show that MetaHipMer matches or outperforms the state-of-the-art tools in terms
of accuracy. Moreover, MetaHipMer scales efficiently to large concurrencies and
is able to assemble previously intractable grand challenge metagenomes. We
demonstrate the unprecedented capability of MetaHipMer by computing the first
full assembly of the Twitchell Wetlands dataset, consisting of 7.5 billion
reads - size 2.6 TBytes.Comment: Accepted to SC1
Pressure Fluctuations in Natural Gas Networks caused by Gas-Electric Coupling
The development of hydraulic fracturing technology has dramatically increased
the supply and lowered the cost of natural gas in the United States, driving an
expansion of natural gas-fired generation capacity in several electrical
inter-connections. Gas-fired generators have the capability to ramp quickly and
are often utilized by grid operators to balance intermittency caused by wind
generation. The time-varying output of these generators results in time-varying
natural gas consumption rates that impact the pressure and line-pack of the gas
network. As gas system operators assume nearly constant gas consumption when
estimating pipeline transfer capacity and for planning operations, such
fluctuations are a source of risk to their system. Here, we develop a new
method to assess this risk. We consider a model of gas networks with
consumption modeled through two components: forecasted consumption and small
spatio-temporarily varying consumption due to the gas-fired generators being
used to balance wind. While the forecasted consumption is globally balanced
over longer time scales, the fluctuating consumption causes pressure
fluctuations in the gas system to grow diffusively in time with a diffusion
rate sensitive to the steady but spatially-inhomogeneous forecasted
distribution of mass flow. To motivate our approach, we analyze the effect of
fluctuating gas consumption on a model of the Transco gas pipeline that extends
from the Gulf of Mexico to the Northeast of the United States.Comment: 10 pages, 7 figure
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