20,940 research outputs found
Enhancing the significance of gravitational wave bursts through signal classification
The quest to observe gravitational waves challenges our ability to
discriminate signals from detector noise. This issue is especially relevant for
transient gravitational waves searches with a robust eyes wide open approach,
the so called all- sky burst searches. Here we show how signal classification
methods inspired by broad astrophysical characteristics can be implemented in
all-sky burst searches preserving their generality. In our case study, we apply
a multivariate analyses based on artificial neural networks to classify waves
emitted in compact binary coalescences. We enhance by orders of magnitude the
significance of signals belonging to this broad astrophysical class against the
noise background. Alternatively, at a given level of mis-classification of
noise events, we can detect about 1/4 more of the total signal population. We
also show that a more general strategy of signal classification can actually be
performed, by testing the ability of artificial neural networks in
discriminating different signal classes. The possible impact on future
observations by the LIGO-Virgo network of detectors is discussed by analysing
recoloured noise from previous LIGO-Virgo data with coherent WaveBurst, one of
the flagship pipelines dedicated to all-sky searches for transient
gravitational waves
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Room-Temperature Sputtered SnO2 as Robust Electron Transport Layer for Air-Stable and Efficient Perovskite Solar Cells on Rigid and Flexible Substrates.
Extraordinary photovoltaic performance and intriguing optoelectronic properties of perovskite solar cells (PSCs) have aroused enormous interest from both academic research and photovoltaic (PV) industry. In order to bring PSC technology from laboratory to market, material stability, device flexibility, and scalability are important issues to address for vast production. Nevertheless, PSCs are still primarily prepared by solution methods which limit film scalability, while high-temperature processing of metal oxide electron transport layer (ETL) makes PSCs costly and incompatible with flexible substrates. Here, we demonstrate rarely-reported room-temperature radio frequency (RF) sputtered SnO2 as a promising ETL with suitable band structure, high transmittance, and excellent stability to replace its solution-processed counterpart. Power conversion efficiencies (PCEs) of 12.82% and 5.88% have been achieved on rigid glass substrate and flexible PEN substrate respectively. The former device retained 93% of its initial PCE after 192-hour exposure in dry air while the latter device maintained over 90% of its initial PCE after 100 consecutive bending cycles. The result is a solid stepping stone toward future PSC all-vapor-deposition fabrication which is being widely used in the PV industry now
Optical communication on CubeSats - Enabling the next era in space science
CubeSats are excellent platforms to rapidly perform simple space experiments.
Several hundreds of CubeSats have already been successfully launched in the
past few years and the number of announced launches grows every year. These
platforms provide an easy access to space for universities and organizations
which otherwise could not afford it. However, these spacecraft still rely on RF
communications, where the spectrum is already crowded and cannot support the
growing demand for data transmission to the ground. Lasercom holds the promise
to be the solution to this problem, with a potential improvement of several
orders of magnitude in the transmission capacity, while keeping a low size,
weight and power. Between 2016 and 2017, The Keck Institute for Space Studies
(KISS), a joint institute of the California Institute of Technology and the Jet
Propulsion Laboratory, brought together a group of space scientists and
lasercom engineers to address the current challenges that this technology
faces, in order to enable it to compete with RF and eventually replace it when
high-data rate is needed. After two one-week workshops, the working group
started developing a report addressing three study cases: low Earth orbit,
crosslinks and deep space. This paper presents the main points and conclusions
of these KISS workshops.Comment: 7 pages, 5 figures, 2 tables, Official Final Report of KISS (Keck
Institute for Space Studies) workshop on "Optical communication on CubeSats"
(http://kiss.caltech.edu/workshops/optcomm/optcomm.html
Independence in CLP Languages
Studying independence of goals has proven very useful in the context of logic programming. In particular, it has provided a formal basis for powerful automatic parallelization tools, since independence ensures that two goals may be evaluated in parallel while preserving correctness and eciency. We extend the concept of independence to constraint logic programs (CLP) and
prove that it also ensures the correctness and eciency of the parallel evaluation of independent goals. Independence for CLP languages is more complex than for logic programming as search space preservation is necessary but no longer sucient for ensuring correctness and eciency. Two
additional issues arise. The rst is that the cost of constraint solving may depend upon the order constraints are encountered. The second is the need to handle dynamic scheduling. We clarify these issues by proposing various types of search independence and constraint solver independence, and show how they can be combined to allow dierent optimizations, from parallelism to intelligent
backtracking. Sucient conditions for independence which can be evaluated \a priori" at run-time are also proposed. Our study also yields new insights into independence in logic programming languages. In particular, we show that search space preservation is not only a sucient but also a necessary condition for ensuring correctness and eciency of parallel execution
Remote-scope Promotion: Clarified, Rectified, and Verified
Modern accelerator programming frameworks, such as OpenCL, organise threads into work-groups. Remote-scope promotion (RSP) is a language extension recently proposed by AMD researchers that is designed to enable applications, for the first time, both to optimise for the common case of intra-work-group communication (using memory scopes to provide consistency only within a work-group) and to allow occasional inter-work-group communication (as required, for instance, to support the popular load-balancing idiom of work stealing). We present the first formal, axiomatic memory model of OpenCL extended with RSP. We have extended the Herd memory model simulator with support for OpenCL kernels that exploit RSP, and used it to discover bugs in several litmus tests and a work-stealing queue, that have been used previously in the study of RSP. We have also formalised the proposed GPU implementation of RSP. The formalisation process allowed us to identify bugs in the description of RSP that could result in well-synchronised programs experiencing memory inconsistencies. We present and prove sound a new implementation of RSP that incorporates bug fixes and requires less non-standard hardware than the original implementation. This work, a collaboration between academia and industry, clearly demonstrates how, when designing hardware support for a new concurrent language feature, the early application of formal tools and techniques can help to prevent errors, such as those we have found, from making it into silicon
Efficient separation of small microparticles at high flowrates using spiral channels: Application to waterborne pathogens
Detecting waterborne pathogens is a challenging task because of their low concentration in water and their wide diversity. In order to ease this detection process, the potential of microfluidics is investigated in this paper. Spiral channels are designed for separating particles, in a single device and without any external forces or additional buffer, depending on their size at high flowrates. This paper focuses first on the impact of the channel length, flowrate, particle concentration and size on the separation efficiency of polystyrene beads of relevant sizes . The system is then tested with viable and non-viable pathogens (Cryptosporidium parvum  ) with an average size around
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