132,175 research outputs found
R&D on Triple-GEM detectors for the optimal and safe operation in the CMS experiment
No full textIn the framework of the High-Luminosity Large Hadron Collider project (HL-LHC), the
LHC experiments will require upgrades of their detectors to cope with the new accelerator
performance. The upgrade of the CMS Muon Spectrometer foresees the installation of
three new muon stations based on the Gas Electron Multiplier (GEM) technology, referred
to as GE1/1, GE2/1 and ME0. While the installation and commissioning of the GE1/1
detectors is currently underway, the GE2/1 and ME0 detectors are expected to be installed
between 2023 and 2026.
This thesis work took place in such framework. The main goal was to assure a safe
operation of all the GEM based stations from the gas mixture point of view, in particular
by developing a reliable system to detect any systematic variation of the gas mixture
composition. On the other hand the focus was on ensuring the correct operation of GEM
detectors when irradiated with harsh and intense particle fluxes, in particular testing the
detector rate capability and aging properties.
The first chapter gives a general overview on the LHC machine and the CMS experiment
with some details about its GEM based upgrades. The second will introduce
some basic concepts about the particle interactions with the matter and the physical
processes behind gaseous detectors operations, along with an overview of the main
gaseous detectors technologies.
The third chapter will focus on the work done to develop a reliable system for gases
concentrations detection in the gas mixture supplied to CMS GEM detectors (nominally
Ar/CO2 (70/30)). The R&D tests performed to reach the necessary knowledge level to
use a GEM detector for determining the relative ratio of the two gases will be described.
The fourth chapter will present the results that convinced the CMS Group to change
the GEM foil design to exploit the maximum performance of the technology in the high
hit rate environment. The results, along with the new design, will be described up to the
current R&D stage.
The fifth chapter will discuss the advanced aging tests performed to test the radiation
hardness and the aging mechanisms taking place in GEM detector when exposed to
heavy irradiation and gas contamination. Many experiments were performed also to
test different variables that play a role in the aging of both Wire Chambers and GEM
detectors
A virtual chemical mechanism for prediction of NO emissions from flames
No full textA reduced order kinetic model for NO (nitric oxide) prediction, based on the virtual chemistry methodology [M. Cailler, N. Darabiha, and B. Fiorina, Development of a virtual optimized chemistry method. Application to hydrocarbon/air combustion, Combust. Flame 211 (2020), pp. 281–302], is developed and applied. Virtual chemistry aims to optimise thermochemical properties and kinetic rate parameters of a network of virtual species and reactions. A virtual main chemical mechanism is dedicated to temperature and heat release prediction and is coupled with the flow governing equations, whereas satellite sub-mechanisms are designed to predict pollutants formation. Two virtual chemistry mechanisms are here employed: a main mechanism for calculating the temperature and heat release rate and a second mechanism dedicated to NO prediction. To recover the chemical structure of multi-mode combustion, both premixed and non-premixed flamelets are included in the learning database used to optimise the virtual NO mechanism. A multi-zone optimisation procedure is developed to accurately capture both fast and slow NO chemistry that include prompt, thermal and reburning pathways. The proposed NO sub-mechanism and optimisation methodology are applied to CH (Formula presented.) /air combustion. Laminar 1-D premixed and non-premixed flamelet configurations are first tested. The approach is then further assessed in 2-D CFD laminar flame simulations, by providing a direct comparison against detailed chemistry. 2-D premixed, non-premixed and partially premixed flame configurations are numerically investigated. For all cases, the virtual mechanism fairly captures temperature and (Formula presented.) chemistry with only 12 virtual species and 8 virtual reactions with a drastic CPU time reduction compared to detailed chemistry
Simulation and R&D studies for the muon spectrometer at a 10 TeV Muon Collider
No full textThe Muon Collider (MC) is one of the most promising machines in terms of discovery potential. However, technological challenges arise from muon instability. This paper introduces a novel approach to muon track reconstruction designed to manage the high background levels. In this context, a fast-timing detector is required. This contribution presents the results of R&D efforts on the Picosec detector, a new generation of fast- timing Micro-Pattern Gaseous Detectors (MPGD). Specifically, the results from various test beam campaigns, focused on optimizing this technology for future experiments at a MC facility, are discussed
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
A Comparison of IR-UWB Receivers Adapted to MUI with Mixture Based Distributions
No full textInternational audienc
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Valutazione e interpretazione delle testimonianze
No full textL'abstract non è fornito in questo sistema. Rivolgersi all'autore per avere informazion
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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