Jet energy Dotaz Zobrazit nápovědu
We describe a method to obtain point and dispersion estimates for the energies of jets arising from b quarks produced in proton-proton collisions at an energy of s = 13 TeV at the CERN LHC. The algorithm is trained on a large sample of simulated b jets and validated on data recorded by the CMS detector in 2017 corresponding to an integrated luminosity of 41 fb - 1 . A multivariate regression algorithm based on a deep feed-forward neural network employs jet composition and shape information, and the properties of reconstructed secondary vertices associated with the jet. The results of the algorithm are used to improve the sensitivity of analyses that make use of b jets in the final state, such as the observation of Higgs boson decay to b b ¯ .
- Klíčová slova
- CMS, Deep learning, Higgs boson, Jet energy, Jet resolution, b jets,
- Publikační typ
- časopisecké články MeSH
OBJECTIVES: The contribution deals with a risk assessment in practical applications of the high-energy liquid jet technology from the point of view of the risk identification, estimation and evaluation. MATERIALS AND METHODS: Differences between three different types of workplaces are highlighted and analysed - the indoor, the outdoor and the research ones. Theoretical analyses are supported by particular application of the method for the risk assessment in the Laboratory of Liquid Jets at the VŠB - Technical University of Ostrava. This laboratory is primarily oriented to research. Nevertheless, the conclusions can be used also for predominantly commercial workplaces. RESULTS: Some new considerations and evaluations concerning health and safety are presented. CONCLUSIONS: Failure Mode and Effect Analysis (FMEA) procedures were applied and their limitations in risk assessment of water jet-based technologies are explained.
- MeSH
- hodnocení rizik MeSH
- hygiena práce * MeSH
- lidé MeSH
- pracovní úrazy prevence a kontrola MeSH
- těžební a zpracovatelský průmysl MeSH
- tlak škodlivé účinky MeSH
- voda * MeSH
- vyrobené materiály MeSH
- výzkum MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- voda * MeSH
This study was undertaken to look for confirmation that heat transfer induced by abrasive water jet machining (AWJM) affects the microstructure of the material cut. The structure of S235JR carbon steel used in the experiments was reported to change locally in the jet impact zone due to the high concentration of energy generated during cutting with the abrasive water jet. It is assumed that some of the energy is transferred into the material in the form of heat. This is particularly true for materials of considerable thickness with a high thermal conductivity coefficient when cutting is performed at low speeds or with high abrasive consumption. The literature on the subject suggests that in AWJM there is little or no thermal energy effect on the microstructure of the material cut. The research described here involved the measurement of the cutting temperature with thermocouples placed at four different distances from the edge. The distances were measured using computed tomography inspection. The thermocouples used in the tests were capable of detecting temperatures of up to 100 °C. Locally, temperatures at the edge may reach much higher values. The results of the X-ray diffraction qualitative phase analysis reveal that locally the temperatures may be much higher than the eutectoid temperature. Phase changes occurred along the edge since austenite was observed. This suggests that the temperature in the jet impact zone was much higher than the eutectoid temperature. Optical microscopy was also employed to study the material microstructure. Finally, the material nanohardness was determined.
- Klíčová slova
- XRD analysis, abrasive water jet, computed tomography inspection, cutting temperature, jet impact zone, temperature measurement,
- Publikační typ
- časopisecké články MeSH
This article considers effects of local heat transfer taking place insteel cutting by abrasive water jet machining (AWJM). The influence of temperature changes during AWJM has not been investigated thoroughly. Most studies on AWJM suggest that thermal energy has little or no effect on the material cut. This study focused on the analysis of the material microstructure and indentation microhardness in the jet impact zone and the adjacent area. The structure features revealed through optical metallography and scanning microscopy suggest local temperature changes caused by the impact of the abrasive water jet against the workpiece surface. From the microscopic examinationand hardness tests, it is clear that, during the process, large amounts of energy were transferred locally. The mechanical stress produced by the water jet led to plastic deformation at and near the surface. This was accompanied by the generation and transfer of large amounts of heat resulting in a local rise in temperature to 450 °C or higher.
- Klíčová slova
- abrasive water jet, cutting, jet impact zone, metallographic analysis, microstructure, temperature measurement,
- Publikační typ
- časopisecké články MeSH
The measurement of the jet energy resolution is presented using data recorded with the ATLAS detector in proton-proton collisions at [Formula: see text]. The sample corresponds to an integrated luminosity of 35 pb-1. Jets are reconstructed from energy deposits measured by the calorimeters and calibrated using different jet calibration schemes. The jet energy resolution is measured with two different in situ methods which are found to be in agreement within uncertainties. The total uncertainties on these measurements range from 20 % to 10 % for jets within |y|<2.8 and with transverse momenta increasing from 30 GeV to 500 GeV. Overall, the Monte Carlo simulation of the jet energy resolution agrees with the data within 10 %.
- Publikační typ
- časopisecké články MeSH
The authors present their own experience with the use of a hot-jet coagulator in resections of the liver. The principle is based on contact-free transmission of thermal energy by means of a current of hot air to achieve haemostasis and tissue coagulation. They mention the use of the apparatus in animal experiments and in resections of the liver in nine patients. They recommend the procedure as one possibility of haemostasis where conventional methods do not affect haemostasis.
The aim of this study was to investigate the potential of polymeric cell structures for the production of energy absorbers and to focus on the geometric optimization of polymeric cell structures producible by additive technologies to achieve the required deformation characteristics, high material efficiency and the low weight of the resulting absorber. A detailed analysis of different types of cell structures (different lattice structures and honeycombs) and their properties was performed. Honeycombs, which have been further examined in more detail, are best suited for absorbing large amounts of energy and high levels of material efficiency at known load directions. Honeycombs have the potential to absorb large amounts of energy relative to their low weight and their deformation characteristics have a relatively constant course. Honeycombs have the major disadvantage of an initial peak. However, this peak can be removed by appropriately adjusting the geometry of the honeycomb. Thanks to the possibilities that additive technology allows us, honeycombs with progressive wall thickness have been designed and researched. The output of this study is a detailed analysis of the properties and several design recommendations for the design of a honeycomb with a progressive wall thickness to achieve the required properties.
- Klíčová slova
- cellular structures, energy absorber, explicit solver, honeycombs, lattice structures,
- Publikační typ
- časopisecké články MeSH
The jet energy scale (JES) and its systematic uncertainty are determined for jets measured with the ATLAS detector using proton-proton collision data with a centre-of-mass energy of [Formula: see text] TeV corresponding to an integrated luminosity of [Formula: see text][Formula: see text]. Jets are reconstructed from energy deposits forming topological clusters of calorimeter cells using the anti-[Formula: see text] algorithm with distance parameters [Formula: see text] or [Formula: see text], and are calibrated using MC simulations. A residual JES correction is applied to account for differences between data and MC simulations. This correction and its systematic uncertainty are estimated using a combination of in situ techniques exploiting the transverse momentum balance between a jet and a reference object such as a photon or a [Formula: see text] boson, for [Formula: see text] and pseudorapidities [Formula: see text]. The effect of multiple proton-proton interactions is corrected for, and an uncertainty is evaluated using in situ techniques. The smallest JES uncertainty of less than 1 % is found in the central calorimeter region ([Formula: see text]) for jets with [Formula: see text]. For central jets at lower [Formula: see text], the uncertainty is about 3 %. A consistent JES estimate is found using measurements of the calorimeter response of single hadrons in proton-proton collisions and test-beam data, which also provide the estimate for [Formula: see text] TeV. The calibration of forward jets is derived from dijet [Formula: see text] balance measurements. The resulting uncertainty reaches its largest value of 6 % for low-[Formula: see text] jets at [Formula: see text]. Additional JES uncertainties due to specific event topologies, such as close-by jets or selections of event samples with an enhanced content of jets originating from light quarks or gluons, are also discussed. The magnitude of these uncertainties depends on the event sample used in a given physics analysis, but typically amounts to 0.5-3 %.
- Publikační typ
- časopisecké články MeSH
Double-differential three-jet production cross-sections are measured in proton-proton collisions at a centre-of-mass energy of [Formula: see text] using the ATLAS detector at the large hadron collider. The measurements are presented as a function of the three-jet mass [Formula: see text], in bins of the sum of the absolute rapidity separations between the three leading jets [Formula: see text]. Invariant masses extending up to 5 TeV are reached for [Formula: see text]. These measurements use a sample of data recorded using the ATLAS detector in 2011, which corresponds to an integrated luminosity of [Formula: see text]. Jets are identified using the anti-[Formula: see text] algorithm with two different jet radius parameters, [Formula: see text] and [Formula: see text]. The dominant uncertainty in these measurements comes from the jet energy scale. Next-to-leading-order QCD calculations corrected to account for non-perturbative effects are compared to the measurements. Good agreement is found between the data and the theoretical predictions based on most of the available sets of parton distribution functions, over the full kinematic range, covering almost seven orders of magnitude in the measured cross-section values.
- Publikační typ
- časopisecké články MeSH
This paper presents a measurement of the inclusive 3-jet production differential cross section at a proton-proton centre-of-mass energy of 7 TeV using data corresponding to an integrated luminosity of 5[Formula: see text]collected with the CMS detector. The analysis is based on the three jets with the highest transverse momenta. The cross section is measured as a function of the invariant mass of the three jets in a range of 445-3270 GeV and in two bins of the maximum rapidity of the jets up to a value of 2. A comparison between the measurement and the prediction from perturbative QCD at next-to-leading order is performed. Within uncertainties, data and theory are in agreement. The sensitivity of the observable to the strong coupling constant [Formula: see text] is studied. A fit to all data points with 3-jet masses larger than 664 GeV gives a value of the strong coupling constant of [Formula: see text].
- Klíčová slova
- 3-jet mass, Alpha-S, CMS, Jets, PDF, Physics, QCD, Strong coupling constant,
- Publikační typ
- časopisecké články MeSH
