162 research outputs found
On Fast Large-Scale Program Analysis in Datalog
Designing and crafting a static program analysis is challenging due to the complexity of the task at hand. Among the challenges are modelling the semantics of the input language, finding suitable abstractions for the analysis, and handwriting efficient code for the analysis in a traditional imperative language such as C++. Hence, the development of static program analysis tools is costly in terms of development time and resources for real world languages. To overcome, or at least alleviate the costs of developing a static program analysis, Datalog has been proposed as a domain specific language (DSL).With Datalog, a designer expresses a static program analysis in the form of a logical specification. While a domain specific language approach aids in the ease of development of program analyses, it is commonly accepted that such an approach has worse runtime performance than handcrafted static analysis tools. In this work, we introduce a new program synthesis methodology for Datalog specifications to produce highly efficient monolithic C++ analyzers. The synthesis technique requires the re-interpretation of the semi-naïve evaluation as a scaffolding for translation using partial evaluation. To achieve high-performance, we employ staged compilation techniques and specialize the underlying relational data structures for a given Datalog specification. Experimentation on benchmarks for large-scale program analysis validates the superior performance of our approach over available Datalog tools and demonstrates our competitiveness with state-of-the-art handcrafted tools
Measurement of the Crab Nebula Spectrum Past 100 TeV with HAWC
We present TeV gamma-ray observations of the Crab Nebula, the standard
reference source in ground-based gamma-ray astronomy, using data from the High
Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory. In this analysis we use
two independent energy-estimation methods that utilize extensive air shower
variables such as the core position, shower angle, and shower lateral energy
distribution. In contrast, the previously published HAWC energy spectrum
roughly estimated the shower energy with only the number of photomultipliers
triggered. This new methodology yields a much improved energy resolution over
the previous analysis and extends HAWC's ability to accurately measure
gamma-ray energies well beyond 100 TeV. The energy spectrum of the Crab Nebula
is well fit to a log parabola shape with emission up to at least 100 TeV. For the first
estimator, a ground parameter that utilizes fits to the lateral distribution
function to measure the charge density 40 meters from the shower axis, the
best-fit values are
=(2.350.04)10 (TeV cm
s), =2.790.02, and
=0.100.01. For the second estimator, a neural
network which uses the charge distribution in annuli around the core and other
variables, these values are
=(2.310.02)10 (TeV cm
s), =2.730.02, and
=0.060.010.02. The first set of uncertainties are statistical;
the second set are systematic. Both methods yield compatible results. These
measurements are the highest-energy observation of a gamma-ray source to date.Comment: published in Ap
Managed Aquifer Recharge as a Tool to Enhance Sustainable Groundwater Management in California
A growing population and an increased demand for water resources have resulted in a global trend of groundwater depletion. Arid and semi-arid climates are particularly susceptible, often relying on groundwater to support large population centers or irrigated agriculture in the absence of sufficient surface water resources. In an effort to increase the security of groundwater resources, managed aquifer recharge (MAR) programs have been developed and implemented globally. MAR is the approach of intentionally harvesting and infiltrating water to recharge depleted aquifer storage. California is a prime example of this growing problem, with three cities that have over a million residents and an agricultural industry that was valued at 47 billion dollars in 2015. The present-day groundwater overdraft of over 100 km3 (since 1962) indicates a clear disparity between surface water supply and water demand within the state. In the face of groundwater overdraft and the anticipated effects of climate change, many new MAR projects are being constructed or investigated throughout California, adding to those that have existed for decades. Some common MAR types utilized in California include injection wells, infiltration basins (also known as spreading basins, percolation basins, or recharge basins), and low-impact development. An emerging MAR type that is actively being investigated is the winter flooding of agricultural fields using existing irrigation infrastructure and excess surface water resources, known as agricultural MAR. California therefore provides an excellent case study to look at the historical use and performance of MAR, ongoing and emerging challenges, novel MAR applications, and the potential for expansion of MAR. Effective MAR projects are an essential tool for increasing groundwater security, both in California and on a global scale. This chapter aims to provide an overview of the most common MAR types and applications within the State of California and neighboring semi-arid regions
HAWC and Fermi-LAT Detection of Extended Emission from the Unidentified Source 2HWC J2006+341
The discovery of the TeV point source 2HWC J2006+341 was reported in the
second HAWC gamma-ray catalog. We present a follow-up study of this source
here. The TeV emission is best described by an extended source with a soft
spectrum. At GeV energies, an extended source is significantly detected in
Fermi-LAT data. The matching locations, sizes and spectra suggest that both
gamma-ray detections correspond to the same source. Different scenarios for the
origin of the emission are considered and we rule out an association to the
pulsar PSR J2004+3429 due to extreme energetics required, if located at a
distance of 10.8 kpc.Comment: 12 pages, 2 figures. To appear in ApJ
Novel Crystalline SiO2 Nanoparticles via Annelids Bioprocessing of Agro-Industrial Wastes
The synthesis of nanoparticles silica oxide from rice husk, sugar cane bagasse and coffee husk, by employing vermicompost with annelids (Eisenia foetida) is reported. The product (humus) is calcinated and extracted to recover the crystalline nanoparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS) show that the biotransformation allows creating specific crystalline phases, since equivalent particles synthesized without biotransformation are bigger and with different crystalline structure
Multiple Galactic Sources with Emission Above 56 TeV Detected by HAWC
We present the first catalog of gamma-ray sources emitting above 56 and 100
TeV with data from the High Altitude Water Cherenkov (HAWC) Observatory, a wide
field-of-view observatory capable of detecting gamma rays up to a few hundred
TeV. Nine sources are observed above 56 TeV, all of which are likely Galactic
in origin. Three sources continue emitting past 100 TeV, making this the
highest-energy gamma-ray source catalog to date. We report the integral flux of
each of these objects. We also report spectra for three highest-energy sources
and discuss the possibility that they are PeVatrons.Comment: Accepted by Physical Review Letter
A Contribution of the HAWC Observatory to the TeV era in the High Energy Gamma-Ray Astrophysics: The case of the TeV-Halos
We present a short overview of the TeV-Halos objects as a discovery and a
relevant contribution of the High Altitude Water \v{C}erenkov (HAWC)
observatory to TeV astrophysics. We discuss history, discovery, knowledge, and
the next step through a new and more detailed analysis than the original study
in 2017. TeV-Halos will contribute to resolving the problem of the local
positron excess observed on the Earth. To clarify the latter, understanding the
diffusion process is mandatory.Comment: Work presented in the 21st International Symposium on Very High
Energy Cosmic Ray Interactions(ISVHECRI 2022) as part of the Ph. D. Thesis of
Ramiro Torres-Escobedo (SJTU, Shanghai, China). Accepted for publication in
SciPost Physics Proceedings (ISSN 2666-4003). 11 pages, 3 Figures. Short
overview of HAWC and TeV Halos objects until 202
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