1,613 research outputs found
Trends and developments in green cement and concrete technology
Peer reviewedPublisher PD
Studies of Nanotube Channeling for Efficient Beam Scraping at Accelerators
While particle beam steering (and in particular, "scraping") in accelerators
by bent channeling crystals is an established technique extensively tested at
IHEP Protvino and other major high-energy labs, an interesting question is how
one could improve channeling capabilities by applying modern nanotechnology.
Theoretical research of nanotube channeling was in progress over recent years.
In this work, we assess potential benefits from nanotube channeling for real
accelerator systems. We report simulation studies of channeling in
nanostructured material (carbon SWNT and MWNT) tested for possible serving as a
primary scraper for the collimation systems of hadron colliders. The advantages
of nanostructured material as a potential choice for a primary scraper in a
high-energy accelerator such as LHC or the Tevatron are discussed in comparison
to crystal lattices and amorphous material. We evaluate physical processes
relevant to this application and reveal nanotechnology requirements.Comment: Presented at the Int. Conf. on Atomic Collisions with Solids
(ICACS-21, Genova 4-9 July 2004
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Where's the harm? A social marketing approach to reframing 'problem' drinking cultures
Alcohol consumption is often linked to a broad range of social and health problems, yet alcohol also plays a fundamental role in social bonding between people. This paper considers the potential of social marketing to contribute to alcohol consumption reduction and reframe social norms that encourage 'problem' drinking. Based on qualitative research with a variety of Scottish drinkers, the paper emphasises how and why a better understanding of the culturally bound meanings of alcohol (e.g. social identity, self-concept) are of crucial importance to inform any social marketing approach to reframing excessive drinking
Charting the TeV Milky Way: H.E.S.S. Galactic plane survey maps, catalog and source populations
Very-high-energy (VHE, E>100 GeV) gamma-rays provide a unique view of the
non-thermal universe, tracing the most violent and energetic phenomena at work
inside our Galaxy and beyond. The latest results of the H.E.S.S. Galactic Plane
Survey (HGPS) undertaken by the High Energy Stereoscopic System (H.E.S.S.), an
array of four imaging atmospheric Cherenkov telescopes located in Namibia, are
described here. The HGPS aims at the detection of cosmic accelerators with
environments suitable for the production of photons at the highest energies and
has led to the discovery of an unexpectedly large and diverse population of
over 60 sources of TeV gamma rays within its current range of l = 250 to 65
degrees in longitude and |b|<3.5 degrees in latitude. The data set of the HGPS
comprises 2800 hours of high-quality data, taken in the years 2004 to 2013. The
sensitivity for the detection of point-like sources, assuming a power-law
spectrum with a spectral index of 2.3 at a statistical significance of 5 sigma,
is now at the level of 2% Crab or better in the core HGPS region. The latest
maps of the inner Galaxy at TeV energies are shown alongside an introduction to
the first H.E.S.S. Galactic Plane Survey catalog. Finally, in addition to an
overview of the H.E.S.S. Galactic source population a few remarkable, recently
discovered sources will be highlighted.Comment: 8 pages, 6 figures, in Proceedings of the 48th Rencontres de Moriond
(2013), La Thuile (Italy
A Population of Teraelectronvolt Pulsar Wind Nebulae in the H.E.S.S. Galactic Plane Survey
The most numerous source class that emerged from the H.E.S.S. Galactic Plane
Survey are Pulsar Wind Nebulae (PWNe). The 2013 reanalysis of this survey,
undertaken after almost 10 years of observations, provides us with the most
sensitive and most complete census of gamma-ray PWNe to date. In addition to a
uniform analysis of spectral and morphological parameters, for the first time
also flux upper limits for energetic young pulsars were extracted from the
data. We present a discussion of the correlation between energetic pulsars and
TeV objects, and their respective properties. We will put the results in
context with the current theoretical understanding of PWNe and evaluate the
plausibility of previously non-established PWN candidates.Comment: 4 pages, 5 figures. In Proceedings of the 33rd International Cosmic
Ray Conference (ICRC2013), Rio de Janeiro (Brazil
Very-high-energy gamma radiation from supernova remnants as seen with H.E.S.S
Very-high-energy (VHE, E > 100 GeV) gamma radiation has already been detected
from several supernova remnants (SNRs). These objects, which are well-studied
in radio, optical and X-ray wavelengths, constitute one of the most intriguing
source classes in VHE astronomy. H.E.S.S., an array of four imaging atmospheric
Cherenkov telescopes in Namibia, has recorded an extensive dataset of VHE
gamma-ray observations covering the central region of the Milky Way, both from
pointed observations as well as from the Galactic Plane Survey conducted in the
inner region of the Galaxy. From radio observations, several hundred SNRs are
known in the Milky Way, but until now only few of them have been identified as
VHE gamma-ray emitters. Using the H.E.S.S. dataset and a large ensemble of
radio SNRs localized in the inner region of the Galaxy, the standard framework
that links the origin of cosmic rays to the gamma-ray visibility of SNRs can
now be tested. Here we present the ensemble of investigated SNRs and discuss
constraints on the parameter space used within a theoretical model of hadronic
VHE gamma-ray production.Comment: Proceeding of the 32nd ICRC, August 11-18 2011, Beijing, Chin
SQG-Differential Evolution for difficult optimization problems under a tight function evaluation budget
In the context of industrial engineering, it is important to integrate
efficient computational optimization methods in the product development
process. Some of the most challenging simulation-based engineering design
optimization problems are characterized by: a large number of design variables,
the absence of analytical gradients, highly non-linear objectives and a limited
function evaluation budget. Although a huge variety of different optimization
algorithms is available, the development and selection of efficient algorithms
for problems with these industrial relevant characteristics, remains a
challenge. In this communication, a hybrid variant of Differential Evolution
(DE) is introduced which combines aspects of Stochastic Quasi-Gradient (SQG)
methods within the framework of DE, in order to improve optimization efficiency
on problems with the previously mentioned characteristics. The performance of
the resulting derivative-free algorithm is compared with other state-of-the-art
DE variants on 25 commonly used benchmark functions, under tight function
evaluation budget constraints of 1000 evaluations. The experimental results
indicate that the new algorithm performs excellent on the 'difficult' (high
dimensional, multi-modal, inseparable) test functions. The operations used in
the proposed mutation scheme, are computationally inexpensive, and can be
easily implemented in existing differential evolution variants or other
population-based optimization algorithms by a few lines of program code as an
non-invasive optional setting. Besides the applicability of the presented
algorithm by itself, the described concepts can serve as a useful and
interesting addition to the algorithmic operators in the frameworks of
heuristics and evolutionary optimization and computing
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