Articles de revues : « Boosted-jet »

1

Bhattacherjee, Biplob, Sourav K. Mandal et Mihoko Nojiri. « Top Polarization from Boosted Jet Substructure ». EPJ Web of Conferences 49 (2013) : 17007. http://dx.doi.org/10.1051/epjconf/20134917007.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

2

Kagan, Michael, Luke de Oliveira, Lester Mackey, Benjamin Nachman et Ariel Schwartzman. « Boosted Jet Tagging with Jet-Images and Deep Neural Networks ». EPJ Web of Conferences 127 (2016) : 00009. http://dx.doi.org/10.1051/epjconf/201612700009.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

3

Klimek, Matthew D. « The time substructure of jets and boosted object tagging ». Journal of Physics G : Nuclear and Particle Physics 49, n^o 4 (18 mars 2022) : 045008. http://dx.doi.org/10.1088/1361-6471/ac446a.

Texte intégral

Résumé :

Abstract We propose the study of the time substructure of jets, motivated by the fact that the next generation of detectors at particle colliders will resolve the time scale over which jet constituents arrive. This effect is directly related to the fragmentation and hadronization process, which transforms partons into massive hadrons with a distribution of velocities. We review the basic predictions for the velocity distribution of jet hadrons, and suggest an application for this information in the context of boosted object tagging. By noting that the velocity distribution is determined by the properties of the color string which ends on the parton that initiates the jet, we observe that jets originating from boosted color singlets, such as Standard Model electroweak bosons, will exhibit velocity distributions that are boosted relative to QCD jets of similar jet energy. We find that by performing a simple cut on the corresponding distribution of charged hadron arrival times at the detector, we can discriminate against QCD jets that would otherwise give a false positive under a traditional spatial substructure-based boosted object tagger.

Styles APA, Harvard, Vancouver, ISO, etc.

4

Dasgupta, Mrinal, Laís Schunk et Gregory Soyez. « Jet shapes for boosted jet two-prong decays from first-principles ». Journal of High Energy Physics 2016, n^o 4 (avril 2016) : 1–50. http://dx.doi.org/10.1007/jhep04(2016)166.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

5

ALON, RAZ. « JET RESULTS, JET RECONSTRUCTION, AND UNDERLYING EVENT STUDIES AT CDF ». International Journal of Modern Physics E 20, n^o 07 (juillet 2011) : 1572–77. http://dx.doi.org/10.1142/s0218301311019891.

Texte intégral

Résumé :

We present recent results of jet studies from the CDF Collaboration. The inclusive jet cross section measurements using different clustering algorithms, dijet production, and vector boson plus jet production measurements, are discussed. We also present the first study of highly boosted and massive jets. The properties of these jets, including the mass of the jet and several other observables, such as angularity and planar flow, are discussed.

Styles APA, Harvard, Vancouver, ISO, etc.

6

Schramm, Steven. « ATLAS Jet Reconstruction, Calibration, and Tagging of Lorentzboosted Objects ». EPJ Web of Conferences 182 (2018) : 02113. http://dx.doi.org/10.1051/epjconf/201818202113.

Texte intégral

Résumé :

Jet reconstruction in the ATLAS detector takes multiple forms, as motivated by the intended usage of the jet. Different jet definitions are used in particular for the study of QCD jets and jets containing the hadronic decay of boosted massive particles. These different types of jets are calibrated through a series of mostly sequential steps, providing excellent uncertainties, including a first in situ calibration of the jet mass scale. Jet tagging is investigated, including both not-top-quark vs gluon discrimination as well as W/Z boson, H → bb, and top-quark identification. This includes a first look at the use of Boosted Decision Trees and Deep Neural Networks built from jet substructure variables, as well as Convolutional Neural Networks built from jet images. In all cases, these advanced techniques are seen to provide gains over the standard approaches, with the magnitude of the gain depending on the use case. Future methods for improving jet tagging are briefly discussed, including jet substructure-oriented particle flow primarily for W/Z tagging and new subjet reconstruction strategies for H → bb tagging.

Styles APA, Harvard, Vancouver, ISO, etc.

7

Kim, Hyo J., Yang S. Park, Gae H. Lee, Kee B. Lee, Hasuck Kim et Jae S. Kim. « Emission Characteristics of Jet Configurations for Jet-Boosted Glow Discharge Atomic Emission Spectrometry ». Microchemical Journal 59, n^o 3 (juillet 1998) : 399–412. http://dx.doi.org/10.1006/mchj.1998.1627.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

8

Cacciari, Matteo. « Phenomenological and theoretical developments in jet physics at the LHC ». International Journal of Modern Physics A 30, n^o 31 (5 novembre 2015) : 1546001. http://dx.doi.org/10.1142/s0217751x1546001x.

Texte intégral

Résumé :

We review the history of jets in high energy physics, and describe in more detail the developments of the past ten years, discussing new algorithms for jet finding and their main characteristics, and summarising the status of perturbative calculations for jet cross sections in hadroproduction. We also describe the emergence of jet grooming and tagging techniques and their application to boosted jets analyses.

Styles APA, Harvard, Vancouver, ISO, etc.

9

Chiodini, Gabriele. « Jet Substructure Measurements Sensitive to Soft QCD effects with the ATLAS Detector ». EPJ Web of Conferences 192 (2018) : 00007. http://dx.doi.org/10.1051/epjconf/201819200007.

Texte intégral

Résumé :

Jet substructure observables are powerful tools for the identification of boosted heavy particles and for probing QCD at different energy scales in proton-proton collisions at the LHC. In this work three recent ATLAS measurements sensitive to soft QCD effects and performed with the use of jet substructures are described. Their are kt splitting scales, soft-drop jet masses and pull-jet angles. Some discrepancies between data and predictions are observed in the non-perturbative regime.

Styles APA, Harvard, Vancouver, ISO, etc.

10

Kitadono, Yoshio. « Energy profile of b-jet for boosted top quarks ». EPJ Web of Conferences 80 (2014) : 00027. http://dx.doi.org/10.1051/epjconf/20148000027.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

11

Coleman, E., M. Freytsis, A. Hinzmann, M. Narain, J. Thaler, N. Tran et C. Vernieri. « The importance of calorimetry for highly-boosted jet substructure ». Journal of Instrumentation 13, n^o 01 (9 janvier 2018) : T01003. http://dx.doi.org/10.1088/1748-0221/13/01/t01003.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

12

Dillon, Barry M., Darius A. Faroughy, Jernej F. Kamenik et Manuel Szewc. « Learning Latent Jet Structure ». Symmetry 13, n^o 7 (29 juin 2021) : 1167. http://dx.doi.org/10.3390/sym13071167.

Texte intégral

Résumé :

We summarize our recent work on how to infer on jet formation processes directly from substructure data using generative statistical models. We recount in detail how to cast jet substructure observables’ measurements in terms of Bayesian mixed membership models, in particular Latent Dirichlet Allocation. Using a mixed sample of QCD and boosted tt¯ jet events and focusing on the primary Lund plane observable basis for event measurements, we show how using educated priors on the latent distributions allows to infer on the underlying physical processes in a semi-supervised way.

Styles APA, Harvard, Vancouver, ISO, etc.

13

YU, MEILING, et LIANSHOU LIU. « AN EMPIRICAL STUDY OF BOOSTED NEURAL NETWORK FOR PARTICLE CLASSIFICATION IN HIGH ENERGY COLLISIONS ». International Journal of Modern Physics A 22, n^o 06 (10 mars 2007) : 1201–11. http://dx.doi.org/10.1142/s0217751x07034301.

Texte intégral

Résumé :

The possible application of boosted neural network to particle classification in high energy physics is discussed. A two-dimensional toy model, where the boundary between signal and background is irregular but not overlapping, is constructed to show how boosting technique works with neural network. It is found that boosted neural network not only decreases the error rate of classification significantly but also increases the efficiency and signal–background ratio. Besides, boosted neural network can avoid the disadvantage aspects of single neural network design. The boosted neural network is also applied to the classification of quark- and gluon-jet samples from Monte Carlo e+e- collisions, where the two samples show significant overlapping. The performance of boosting technique for the two different boundary cases — with and without overlapping is discussed.

Styles APA, Harvard, Vancouver, ISO, etc.

14

Benford, Gregory. « Links Between Jet Instabilities, Radiation and Propagation in Astrophysics ». Symposium - International Astronomical Union 107 (1985) : 131–38. http://dx.doi.org/10.1017/s0074180900075562.

Texte intégral

Résumé :

At the head of a jet the confining medium of plasma frequency νp is compressed, so that streaming instabilities between relativistic electrons and this plasma produce waves at νp′ > νp. Considerable power can be lodged in these electrostatic waves, and conversion to electromagnetic waves allows them to propagate far beyond the jet. Emission at ν ≈ νp′ or Compton boosted radiation at ν ≲ γ2 νp′ yields a cone of radiation of angle ~ 1/γ, which illuminates the region directly in front of the jet. This emission is not absorbed by the surrounding plasma unless a cloud blocks the jet. Absorption in a cloud can lead to tunneling through large clouds, or propelling of smaller clouds out of the jet path. In this fashion jets may clear their way through an inhomogeneous medium, avoiding lateral disturbances and preheating their path.

Styles APA, Harvard, Vancouver, ISO, etc.

15

Salafia, Om Sharan, et Giancarlo Ghirlanda. « The Structure of Gamma Ray Burst Jets ». Galaxies 10, n^o 5 (30 août 2022) : 93. http://dx.doi.org/10.3390/galaxies10050093.

Texte intégral

Résumé :

Due to relativistic bulk motion, the structure and orientation of gamma-ray burst (GRB) jets have a fundamental role in determining how they appear. The recent discovery of the GW170817 binary neutron star merger and the associated GRB boosted the interest in the modeling and search for signatures of the presence of a (possibly quasi-universal) jet structure in long and short GRBs. In this review, following a pedagogical approach, we summarize the history of GRB jet structure research over the last two decades, from the inception of the idea of a universal jet structure to the current understanding of the complex processes that shape the structure, which involves the central engine that powers the jet and the interaction of the latter with the progenitor vestige. We put some emphasis on the observable imprints of jet structure on prompt and afterglow emission and on the luminosity function, favoring intuitive reasoning over technical explanations.

Styles APA, Harvard, Vancouver, ISO, etc.

16

QUIROGA-ARIAS, PALOMA, et SEBASTIAN SAPETA. « A COMPARATIVE STUDY OF JET SUBSTRUCTURE TAGGERS ». International Journal of Modern Physics A 28, n^o 18 (20 juillet 2013) : 1350087. http://dx.doi.org/10.1142/s0217751x13500875.

Texte intégral

Résumé :

We explicitly study how jet substructure taggers act on a set of signal and background events. We focus on two-pronged hadronic decay of a boosted Z-boson. The background to this process comes from QCD jets with masses of the order of mZ. We find a way to compare various taggers within a single framework by applying them to the most relevant splitting in a jet. We develop a tool, TOY-TAG, which allows one to get insight into what happens when a particular tagger is applied to a set of signal or background events. It also provides estimates for significance and purity. We use our tool to analyze differences between various taggers and potential ways to improve the performance by combining several of them.

Styles APA, Harvard, Vancouver, ISO, etc.

17

Andrews, Michael, Bjorn Burkle, Shravan Chaudhari, Davide DiCroce, Sergei Gleyzer, Ulrich Heintz, Meenakshi Narain, Manfred Paulini et Emanuele Usai. « End-to-End Jet Classification of Boosted Top Quarks with CMS Open Data ». EPJ Web of Conferences 251 (2021) : 04030. http://dx.doi.org/10.1051/epjconf/202125104030.

Texte intégral

Résumé :

We describe a novel application of the end-to-end deep learning technique to the task of discriminating top quark-initiated jets from those originating from the hadronization of a light quark or a gluon. The end-to-end deep learning technique combines deep learning algorithms and low-level detector representation of the high-energy collision event. In this study, we use lowlevel detector information from the simulated CMS Open Data samples to construct the top jet classifiers. To optimize classifier performance we progressively add low-level information from the CMS tracking detector, including pixel detector reconstructed hits and impact parameters, and demonstrate the value of additional tracking information even when no new spatial structures are added. Relying only on calorimeter energy deposits and reconstructed pixel detector hits, the end-to-end classifier achieves a ROC-AUC score of 0.975±0.002 for the task of classifying boosted top quark jets. After adding derived track quantities, the classifier ROC-AUC score increases to 0.9824±0.0013, serving as the first performance benchmark for these CMS Open Data samples.

Styles APA, Harvard, Vancouver, ISO, etc.

18

Kharb, Preeti, Ethan Stanley, Matthew Lister, Herman Marshall, Chris O'Dea et Stefi Baum. « Understanding jets from sources straddling the Fanaroff-Riley divide ». Proceedings of the International Astronomical Union 10, S313 (septembre 2014) : 211–18. http://dx.doi.org/10.1017/s1743921315002203.

Texte intégral

Résumé :

AbstractResults from Chandra-HST-VLA observations of 13 hybrid sources are presented. Data from ten sources in the literature are analysed along with new data from three hybrid blazars belonging to the MOJAVE sample. Studies of such hybrid sources displaying both FRI and FRII jet characteristics could provide the key to resolving the long-standing Fanaroff-Riley dichotomy issue. A majority of the 13 hybrid sources show FRII-like total radio powers, i.e., they are “hybrid” in radio morphology but not in total radio power. VLBI observations of ten of the 13 sources show that the X-ray jet is on the same side as the one-sided VLBI jet. X-rays are therefore emitted from relativistically-boosted approaching jets. This is consistent with the X-ray emission being IC/CMB in origin in the majority of sources. It is not completely clear from our study that asymmetries in the surrounding medium can create hybrid sources. Hybrid radio morphologies could also be indicative of intrinsically asymmetric jets.

Styles APA, Harvard, Vancouver, ISO, etc.

19

Granelli, Alessandro, Piero Ullio et Jin-Wei Wang. « Blazar-boosted dark matter at Super-Kamiokande ». Journal of Cosmology and Astroparticle Physics 2022, n^o 07 (1 juillet 2022) : 013. http://dx.doi.org/10.1088/1475-7516/2022/07/013.

Texte intégral

Résumé :

Abstract Dark matter particles near the center of a blazar, after being accelerated by the elastic collisions with relativistic electrons and protons in the blazar jet, can be energetic enough to trigger detectable signals at terrestrial detectors. In this work, focusing on the blazars TXS 0506+056 and BL Lacertae, we derive novel limits on the cross section of the elastic scattering between dark matter and electrons by means of the available Super-Kamiokande data. Thanks to the large blazar-boosted dark matter flux, the limit on the dark matter-electron scattering cross section for dark matter masses below 100 MeV can be as low as ∼ 10-38 cm2, that is orders of magnitude stronger than the analogous results from galactic cosmic rays.

Styles APA, Harvard, Vancouver, ISO, etc.

20

Cimò, Giuseppe, et Leonid Gurvits. « Multi-Epoch VLBI observations of the extreme scintillator J1819+3845 ». Proceedings of the International Astronomical Union 6, S275 (septembre 2010) : 192–93. http://dx.doi.org/10.1017/s1743921310016005.

Texte intégral

Résumé :

AbstractThe quasar J1819+3845 has shown extreme variability with flux density variations in the radio regime up to 600% in less than one hour. In case of intrinsic high varibility, the short time scale sets a limit on the size of the emitting region and allows to estimate its brightness temperature. This would exceed 1021 K in the case of J1819+3845. Even an high relativistic jet beamed and doppler boosted in our line of sight cannot explain such an extreme violation of the Inverse Compton limit (1012 K). The variability of this source has been proven to be due to scattering in the Interstellar medium by a number of different experiments. Such an explanation requires a closeby scattering screen (few parsecs) and it results in a brightness temperature of about 1014 K. Many observing campaigns have been carried on to map the innermost jet structures of J1819+3845. Here we present the results of a number of VLBI observations, including space VLBI, to search for the missing jet in this puzzling source.

Styles APA, Harvard, Vancouver, ISO, etc.

21

Heinz, Sebastian, et Andrea Merloni. « Exploring Regimes in Black Hole Scaling ». Proceedings of the International Astronomical Union 8, S290 (août 2012) : 29–36. http://dx.doi.org/10.1017/s174392131201914x.

Texte intégral

Résumé :

AbstractRecent observational evidence suggests the existence of two tracks in the radio-X-ray relation for X-ray binaries. Claims have also been made for deviations from the so-called fundamental plane of black hole activity due to the influence of radiative cooling on synchrotron emission from jets and the relative importance of disk and jet emission. In addition, cases of strongly boosted classes of objects, such as BL Lacs, show evidence for jet emission in their location relative to the fundamental plane. In light of the recent literature activity discussing these issues, we revisit the scaling relations expected for synchrotron emission from jet cores. We review the set of scaling laws expected for different types of emission and discuss their relevance to the new observational data, and the conditions under which breaks in the observed scaling relations should be expected. None of the canonical cases offer a satisfactory explanation for the best fit slope of the steep branch of the radio-X-ray relation in hard-state X-ray binaries.

Styles APA, Harvard, Vancouver, ISO, etc.

22

del Palacio, S., V. Bosch-Ramon et G. E. Romero. « Gamma rays from jets interacting with BLR clouds in blazars ». Astronomy & ; Astrophysics 623 (mars 2019) : A101. http://dx.doi.org/10.1051/0004-6361/201834231.

Texte intégral

Résumé :

Context. The innermost parts of powerful jets in active galactic nuclei are surrounded by dense, high-velocity clouds from the broad-line region, which may penetrate into the jet and lead to the formation of a strong shock. Such jet-cloud interactions are expected to have measurable effects on the γ-ray emission from blazars. Aims. We characterise the dynamics of a typical cloud-jet interaction scenario, and the evolution of its radiative output in the 0.1–30 GeV energy range, to assess to what extent these interactions can contribute to the γ-ray emission in blazars. Methods. We use semi-analytical descriptions of the jet-cloud dynamics, taking into account the expansion of the cloud inside the jet and its acceleration. Assuming that electrons are accelerated in the interaction and making use of the hydrodynamical information, we then compute the high-energy radiation from the cloud, including the absorption of γ-rays in the ambient photon field through pair creation. Results. Jet-cloud interactions can lead to significant γ-ray fluxes in blazars with a broad-line region (BLR), in particular when the cloud expansion and acceleration inside the jet are taken into account. This is caused by 1) the increased shocked area in the jet, which leads to an increase in the energy budget for the non-thermal emission; 2) a more efficient inverse Compton cooling with the boosted photon field of the BLR; and 3) an increased observer luminosity due to Doppler boosting effects. Conclusions. For typical broad-line region parameters, either (i) jet-cloud interactions contribute significantly to the persistent γ-ray emission from blazars or (ii) the BLR is far from spherical or the fraction of energy deposited in non-thermal electrons is small.

Styles APA, Harvard, Vancouver, ISO, etc.

23

Voutilainen, Mikko. « Heavy quark jets at the LHC ». International Journal of Modern Physics A 30, n^o 31 (5 novembre 2015) : 1546008. http://dx.doi.org/10.1142/s0217751x15460082.

Texte intégral

Résumé :

We summarize measurements of [Formula: see text] and [Formula: see text] jet production at the LHC, which are an important signature and background for decays of massive particles such as [Formula: see text]. These include measurements of the inclusive and dijet production of heavy quark jets, [Formula: see text] and [Formula: see text] jets produced in association with vector bosons [Formula: see text] and [Formula: see text], and decays of boosted [Formula: see text] bosons into pairs of [Formula: see text]. The current status of [Formula: see text] tagging and [Formula: see text] jet energy scale is also reviewed. These measurements test perturbative QCD in the four and five-flavor number schemes, and provide insight into the relative importance of heavy flavor production through flavor creation, flavor excitation and gluon splitting channels. The [Formula: see text] measurement provides additionally a powerful way to probe the strange quark and antiquark sea in the proton. The recent studies looking separately at production of one and two [Formula: see text] jets find generally good agreement with theory predictions for two [Formula: see text]-jet production, while some discrepancies are observed for singly produced [Formula: see text] jets, particularly at large [Formula: see text]-jet [Formula: see text], where gluon splitting becomes dominant.

Styles APA, Harvard, Vancouver, ISO, etc.

24

Hanafusa, Hiroaki, Ryosuke Nakashima, Wataru Nakano et Seiichiro Higashi. « Extremely high-power-density atmospheric-pressure thermal plasma jet generated by the nitrogen-boosted effect ». Japanese Journal of Applied Physics 57, n^o 6S2 (9 mai 2018) : 06JH01. http://dx.doi.org/10.7567/jjap.57.06jh01.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

25

Hayashida, Masaaki, et Greg Madejski. « The picture of relativistic jet from Fermi-LAT and multi-band observations of blazar 3C 279 ». Proceedings of the International Astronomical Union 6, S275 (septembre 2010) : 155–59. http://dx.doi.org/10.1017/s1743921310015851.

Texte intégral

Résumé :

AbstractStrong and variable radiation detected over all accessible energy bands in blazar arises from a relativistic, Doppler-boosted jet pointing close to our line of sight. Flat Spectrum Radio Quasar 3C 279 was one of the brightest γ-ray blazars in the sky at the time of the discovery with EGRET. Since the successful launch of the Fermi Gamma-ray Space telescope in 2008, we have organized extensive multi-band observational campaign of 3C 279 from radio to γ-ray bands, also including optical polarimetric observations. The uninterrupted monitoring in the γ-ray band by Fermi-LAT together with the multi-band data provide us with new insights of the relativistic jet of blazar. Here, we present the results of the first-year multi-band campaign of 3C 279 including the discovery of a γ-ray flare event associated with a dramatic change of the optical polarization - as well as a discovery of an “orphan” X-ray flare, unassociated with prominent outbursts in other bands.

Styles APA, Harvard, Vancouver, ISO, etc.

26

Cho, Won B., Myung Y. Kim et Hyo J. Kim. « Effect of magnetic field on the gas-jet boosted radio frequency glow discharge atomic emission spectrometry ». Microchemical Journal 64, n^o 1 (janvier 2000) : 41–50. http://dx.doi.org/10.1016/s0026-265x(99)00010-7.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

27

Boudraa, Bouziane, et Rachid Bessaïh. « Numerical investigations of heat transfer around a hot block subject to a cross-flow and an extended jet hole using ternary hybrid nanofluids ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 236, n^o 8 (30 décembre 2021) : 4412–28. http://dx.doi.org/10.1177/09544062211049872.

Texte intégral

Résumé :

In the last few years, modern heat transfer technologies significantly improved to provide more efficient systems in industries. One of those technologies is cooling electronic components in laminar flow using water nanofluids, which is interesting. This research used a ternary hybrid nanofluid with various nanoparticle forms to conduct a numerical investigation of three-dimensional heat transfer and fluid flow over a heated block exposed to a horizontal flow and an impinging jet. The effects of several variables such as the Reynolds number ratio [Formula: see text], volume fraction of nanoparticles [Formula: see text], length of extended jet hole [Formula: see text], and the influence of the inclination angle of the impinging jet inlet [Formula: see text] on the fluid flow and heat transfer were examined. Using the Ansys-Fluent 14.5 program and under laminar flow conditions, the finite-volume method was applied with the help of the SIMPLE algorithm to solve continuity, momentum, and energy equations. Several characteristics are assessed, including velocity streamline, isotherm contours, Nusselt number contours, the average Nusselt number ([Formula: see text]), the friction factor [Formula: see text], and drop pressure [Formula: see text]. The findings of the current analysis revealed that adding an impinging jet can boost the heat transfer rate up to [Formula: see text] better than a non-impingement jet. Also, a significant enhancement in the heat transfer rate was obtained when growing one of these parameters α, [Formula: see text], and E. Moreover, the ternary hybrid nanofluid with different nanoparticle forms significantly boosts the heat transfer rate compared to the traditional nanofluid. The maximum heat transfer is reached as the velocity of the impinging jet rises. Inclining the angle of the impinging jet inlet with [Formula: see text] toward the channel inlet boosted the rate of heat transfer up to [Formula: see text] compared to the perpendicular impinging jet [Formula: see text]. A strong consensus has been reached with the theoretical and experimental findings found in the literature.

Styles APA, Harvard, Vancouver, ISO, etc.

28

Cagnotta, Antimo, Francesco Carnevali et Agostino De Iorio. « Machine Learning Applications for Jet Tagging in the CMS Experiment ». Applied Sciences 12, n^o 20 (19 octobre 2022) : 10574. http://dx.doi.org/10.3390/app122010574.

Texte intégral

Résumé :

The fundamental physics research at the frontier accessible by today’s particle accelerators such as the CERN Large Hadron Collider pose unique challenges in terms of complexity and abundance of data to analyse. In this context, it is of paramount importance to develop algorithms capable of dealing with multivariate problems to enhance humans’ ability to interpret data and ultimately increase the discovery potential of the experiments. Machine learning techniques therefore assume an increasingly important role in the experiments at the LHC. In this work, we give an overview of the latest developments in this field, with a particular focus on the algorithms developed and used within the CMS Collaboration. The review follows this structure: (1) Introduction presents the CMS Experiment at LHC and the most common methods used in particle physics; (2) Jet Flavour Tagging briefly describes the main algorithms used to reconstruct heavy-flavour jets; (3) Jet Substructure and Deep Tagging focuses on the identification of heavy-particle decay in boosted jets; (4) Analysis Applications gives examples of applying the algorithm in physics analyses; and (5) Conclusions summarises the state-of-the-art and gives indications for future studies.

Styles APA, Harvard, Vancouver, ISO, etc.

29

Burd, P. R., M. Kadler, K. Mannheim, A. K. Baczko, J. Ringholz et E. Ros. « Dual-high-frequency VLBI study of blazar-jet brightness-temperature gradients and collimation profiles ». Astronomy & ; Astrophysics 660 (30 mars 2022) : A1. http://dx.doi.org/10.1051/0004-6361/202142363.

Texte intégral

Résumé :

Context. On the kiloparsec scale, extragalactic radio jets show two distinct morphologies related to their power: collimated high-power jets ending in a bright termination shock and low-power jets opening up close to the core and showing a more diffuse surface brightness distribution. The emergence of this morphological dichotomy on the parsec scale at the innermost jet regions can be studied with very-long-baseline interferometry (VLBI) radio observations of blazars in which the jet emission is strongly Doppler boosted due to relativistic bulk motion at small angles between the jet direction and the line of sight. Aims. We seek to characterize the geometry and emission profiles of the parsec-scale radio jets of flat-spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs) on parsec scales to derive properties of the magnetic field, environment, and energetics for different classes of extragalactic jets. Methods. We analyze the VLBI radio data of 15 FSRQs, 11 BL Lacs, and two radio galaxies contained in both the Monitoring Of Jets in Active galactic nuclei with VLBA Experiments data archive and the Boston University blazar group sample archive at 15 GHz and 43 GHz, repectively. We derived the brightness-temperature and jet-width gradients along the jet axis from parameterizations of the jets using 2D Gaussian brightness distributions. Results. In most BL Lac objects, the diameter and brightness-temperature gradients along the jet axis can generally be described well by single power laws, while the jets of FSRQs show more complex behavior and remain more strongly collimated on larger physical scales. We find evidence for a transition of the global jet geometry from a parabolic to a conical shape in the BL Lac objects 3C 66A, Mrk 421 and BL Lacertae, the radio galaxy 3C 111 and the FSRQs CTA 26, PKS 0528+134, 4C +71.07, 4C +29.45, and 3C 279 outside the Bondi sphere. Conclusions. Our results combined with findings from kinematic VLBI studies that the jets of FSRQs exhibit larger bulk Lorentz factors than BL Lacs are in agreement with relativistic magnetohydrodynamical jet-disk simulations in which the flattening of the jet magnetization profile due to magnetic fields from the accretion disk leads to a more persistent collimation in high-accretion-rate blazars.

Styles APA, Harvard, Vancouver, ISO, etc.

30

Down, Emily. « Modeling the Orientation of AGN ». Proceedings of the International Astronomical Union 5, S267 (août 2009) : 107. http://dx.doi.org/10.1017/s1743921310005685.

Texte intégral

Résumé :

The orientation of nineteen 0.8< z < 2.3 radio-loud quasars was measured using two independent methods. First, Hα was observed in the near IR using ISAAC at the VLT. The complex Hα emission lines were fitted with a range of models, some including emission from a flattened, extended accretion disk following Chen & Halpern (1989). The models were compared using the Bayesian evidence, and the disk axis angles recovered. Second, models were fitted to the ~10 MHz to 20 GHz radio spectral energy distributions (SEDs) to recover the jet angles, assuming that the emission is comprised of a broken power law arising from the radio lobes plus a Doppler-boosted core.

Styles APA, Harvard, Vancouver, ISO, etc.

31

Zhang, Shunlei, Xudong Yang et Bifeng Song. « Numerical Investigation of Performance Enhancement of the S809 Airfoil and Phase VI Wind Turbine Blade Using Co-Flow Jet Technology ». Energies 14, n^o 21 (21 octobre 2021) : 6933. http://dx.doi.org/10.3390/en14216933.

Texte intégral

Résumé :

Making full use of wind energy can effectively alleviate the global energy shortage and environment contamination problems. Nevertheless, how to significantly improve the performance of the wind turbine airfoil and blade is a crucial issue. As the novel flow control method, the co-flow jet (CFJ) technology is one of the most potential methods to solve this problem. Thus, the effects of the CFJ technology on the performance enhancement of the S809 airfoil and Phase VI wind turbine blade are explored in this study. Furthermore, the effects of the injection location and jet momentum coefficient are studied, and an adaptive jet momentum coefficient strategy of the CFJ technology is proposed. Results demonstrate that the CFJ technology can significantly improve the maximum lift coefficient and maximum corrected lift-to-drag ratio of the S809 airfoil. Moreover, the power coefficient of the Phase VI wind turbine blade at the low tip speed ratio is greatly enhanced as well. In particular, the maximum lift coefficient and maximum corrected lift-to-drag ratio of the typical S809 CFJ airfoil with adaptive Cμ are improved by 119.7% and 36.2%, respectively. The maximum power coefficient of CFJ blade can be increased by 4.5%, and the power coefficient of CFJ blade can be boosted by 226.7% when the tip speed ratio is 1.52.

Styles APA, Harvard, Vancouver, ISO, etc.

32

Himelblau, H., D. Kern et G. Davis. « Summary of Cassini Acoustic Criteria Development Using Titan IV Flight Data ». Journal of the IEST 36, n^o 5 (1 septembre 1993) : 19–27. http://dx.doi.org/10.17764/jiet.2.36.5.c408vvk263q216u5.

Texte intégral

Résumé :

The Cassini spacecraft is being developed by the Jet Propulsion Laboratory (JPL) for the National Aeronautics and Space Administration (NASA) to orbit and explore the planet Saturn, its rings, and satellites. Cassini will be launched on a Titan IV and boosted out of Earth orbit by a Centaur. This paper discusses the development of Cassini acoustic criteria using Titan IV flight data. Factors affecting the development of Cassini acoustic criteria using corrected Titan IV flight data1 include the statistical methods used to account for spatial and flight-to-flight variations, the use of maximax spectra, data corrections for acoustic pressure increases near the payload fairing surfaces, and corrections for payload fill factor effects. Separate acoustic criteria were developed for the two launch sites.

Styles APA, Harvard, Vancouver, ISO, etc.

33

Secrest, Nathan J. « Optical–Radio Position Offsets Are Inversely Correlated with AGN Photometric Variability ». Astrophysical Journal Letters 939, n^o 2 (1 novembre 2022) : L32. http://dx.doi.org/10.3847/2041-8213/ac8d5d.

Texte intégral

Résumé :

Abstract Using photometric variability information from the new Gaia DR3 release, I show for the first time that photometric variability is inversely correlated with the prevalence of optical–radio position offsets in the active galactic nuclei (AGNs) that comprise the International Celestial Reference Frame (ICRF). While the overall prevalence of statistically significant optical–radio position offsets is 11%, objects with the largest fractional variabilities exhibit an offset prevalence of only ∼2%. These highly variable objects have redder optical color and steeper optical spectral indices indicative of blazars, in which the optical and radio emission is dominated by a line-of-sight jet, and indeed nearly ∼100% of the most variable objects have γ-ray emission detected by the Fermi Large Area Telescope. This result is consistent with selection on variability preferentially picking jets pointed closest to the line of sight, where the projected optical–radio position offsets are minimized and jet emission is maximally boosted in the observed frame. While only ∼9% of ICRF objects exhibit such large photometric variability, these results suggest that taking source variability into account may provide a means of optimally weighting the optical–radio celestial reference frame link.

Styles APA, Harvard, Vancouver, ISO, etc.

34

GHISELLINI, GABRIELE. « EMISSION AND POWER OF BLAZAR JETS ». International Journal of Modern Physics D 17, n^o 09 (septembre 2008) : 1491–501. http://dx.doi.org/10.1142/s0218271808013078.

Texte intégral

Résumé :

Through the modelling of the spectral energy distribution of blazars, we can infer the physical parameters required to originate the flux we see. Then we can estimate the power of blazar jets in the form of matter and fields. These estimates are rather robust for all classes of blazars, although they are in part dependent on the chosen model (i.e. leptonic rather than hadronic). The indication is that, in almost all cases, the carried Poynting flux is not dominant, while protons should carry most of the power. In emission line blazars the jet has a comparable, and often larger, power than the luminosity of the accretion disk. This is even more true for line–less BL Lacs. If the jet is structured at the sub–pc scale, with a fast spine surrounded by a slower layer, then one component sees the radiation of the other boosted, and this interplay enhances the inverse Compton flux of both. Since the layer emission is less beamed, it can be seen also at large viewing angles, making radio-galaxies very interesting GLAST candidates. Such structures need not be stable components, and can form and disappear rapidly. Ultrafast TeV variability is challenging all existing models, suggesting that at least parts of the jets are moving with large bulk Lorentz factors and at extremely small viewing angles. However, these fast "bullets" are not necessarily challenging our main ideas about the energetics and the composition of the bulk of the jet.

Styles APA, Harvard, Vancouver, ISO, etc.

35

Rosen, Meghan. « Genes & ; cells : Immune system has daily rhythm : Mice with jet lag have boosted supply of inflammatory cells ». Science News 184, n^o 12 (3 décembre 2013) : 10. http://dx.doi.org/10.1002/scin.5591841209.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

36

Xiao, Hubing, Zhihao Ouyang, Lixia Zhang, Liping Fu, Shaohua Zhang, Xiangtao Zeng et Junhui Fan. « The Relativistic Jet and Central Engine of Fermi Blazars ». Astrophysical Journal 925, n^o 1 (1 janvier 2022) : 40. http://dx.doi.org/10.3847/1538-4357/ac36da.

Texte intégral

Résumé :

Abstract The origin of jets is one of the most important issues concerning active galactic nuclei, yet it has remained obscure. In this work, we made use of information from emission lines, spectral energy distributions, and Fermi–LAT γ-ray emission to construct a blazar sample that contains 667 sources. We note that jet power originations are different for BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs). The correlation between jet power P jet and the normalized disk luminosity L Disk/L Edd shows a slope of −1.77 for BL Lacs and a slope of 1.16 for FSRQs. The results seem to suggest that BL Lac jets are powered by extracting black hole (BH) rotation energy, while FSRQ jets are mostly powered by accretion disks. Meanwhile, we find the accretion ratio M ̇ / M ̇ Edd increases with the normalized γ-ray luminosity. Based on this, we propose a dividing line, log ( L BLR / L Edd ) = 0.25 log ( L γ / L Edd ) − 2.23 , to separate FSRQs and BL Lacs in the diagram of L BLR/L Edd against L γ /L Edd using a machine-learning method; the method gives an accuracy of 84.5%. In addition, we propose an empirical formula, M BH / M ☉ ≃ L γ 0.65 / 21.46 , to estimate BH mass based on a strong correlation between γ-ray luminosity and BH mass. Strong γ-ray emission is typical in blazars, and the emission is always boosted by a Doppler-beaming effect. In this work, we generate a new method to estimate a lower limit of Doppler factor δ and give δ BL Lac = 7.94 and δ FSRQ = 11.55.

Styles APA, Harvard, Vancouver, ISO, etc.

37

Choplin, Arthur, Nozomu Tominaga et Bradley S. Meyer. « A strong neutron burst in jet-like supernovae of spinstars ». Astronomy & ; Astrophysics 639 (juillet 2020) : A126. http://dx.doi.org/10.1051/0004-6361/202037966.

Texte intégral

Résumé :

Context. Some metal-poor stars have abundance patterns, which are midway between the slow (s) and rapid (r) neutron capture processes. Aims. We show that the helium shell of a fast rotating massive star experiencing a jet-like explosion undergoes two efficient neutron capture processes: one during stellar evolution and one during the explosion. It eventually provides a material whose chemical composition is midway between the s- and r-process. Methods. A low metallicity 40 M⊙ model with an initial rotational velocity of ∼700 km s−1 was computed from birth to pre-supernova with an extended nuclear network following the slow neutron capture process. A two-dimensional hydrodynamic relativistic code was used to model a E = 1052 erg relativistic jet-like explosion hitting the stellar mantle. The jet-induced nucleosynthesis was calculated in post-processing with an optimised network of 1812 nuclei. Results. During the star’s life, heavy elements from 30 ≲ Z ≲ 82 are produced thanks to an efficient s-process, which is boosted by rotation. At the end of evolution, the helium shell is largely enriched in trans-iron elements and in (unburnt) 22Ne, whose abundance is ∼20 times higher than in a non-rotating model. During the explosion, the jet heats the helium shell up to ∼1.5 GK. It efficiently activates (α, n) reactions, such as 22Ne(α, n), and leads to a strong n-process with neutron densities of ∼1019 − 1020 cm−3 during 0.1 s. This has the effect of shifting the s-process pattern, which was built during stellar evolution, towards heavier elements (e.g. Eu). The resulting chemical pattern is consistent with the abundances of the carbon-enhanced metal-poor r/s star CS29528-028, provided the ejecta of the jet model is not homogeneously mixed. Conclusions. The helium burning zones of rotating massive stars experience an efficient s-process during the evolution followed by an efficient n-process during a jet-like explosion. This is a new astrophysical site which can explain at least some of the metal-poor stars showing abundance patterns midway between the s- and r-process.

Styles APA, Harvard, Vancouver, ISO, etc.

38

van Eerten, Hendrik, et Andrew MacFadyen. « GAMMA-RAY BURST AFTERGLOW LIGHT CURVES FROM A LORENTZ-BOOSTED SIMULATION FRAME AND THE SHAPE OF THE JET BREAK ». Astrophysical Journal 767, n^o 2 (5 avril 2013) : 141. http://dx.doi.org/10.1088/0004-637x/767/2/141.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

39

Cho, Won B., Young A. Woo, Hyo J. Kim, Il J. Kim et Won K. Kang. « Comparison between Direct-Current and Radio-Frequency Gas-Jet-Boosted Glow Discharge Atomic Emission Spectrometry for the Analysis of Steel ». Applied Spectroscopy 51, n^o 7 (juillet 1997) : 1060–66. http://dx.doi.org/10.1366/0003702971941494.

Texte intégral

Résumé :

Comparisons between direct-current (dc) and radio-frequency (rf) gas jet-boosted glow discharge atomic emission spectrometry (GD-AES) have been made with regard to fundamental characteristics and analytical performance. The study of fundamental characteristics includes the voltage—current relationship; a gas flow rate of 0 mL/min to 800 mL/min and pressures ranging from 3 Torr to 5 Torr on dc bias potential; the sample weight loss; and the emission intensity. The dc-powered glow discharge at 90 mA/450 V and 60 mA/710 V at 5 Torr shows 3 × more sample weight loss than the rf discharge at 40 W. Radio-frequency glow discharge shows a short-term precision of <1% relative standard deviation (RSD) and a long-term stability of <5% RSD for both major and trace element lines. Both rf and dc show calibration curves that are linear over 2–3 orders of magnitude, with a general improvement in linearity from ratioing the signal to an internal standard of the matrix. Further improvement of linearity was possible by correcting the bias potential in the rf glow discharge. Limits of detection (LODs) for rf are tens of parts per billion from many trace elements in low-alloy steel, which is one order of magnitude improvement over those for dc.

Styles APA, Harvard, Vancouver, ISO, etc.

40

Kapanadze, Bidzina. « The First- and Second-Order Fermi Acceleration Processes in BL Lacertae Objects ». Galaxies 6, n^o 4 (25 novembre 2018) : 125. http://dx.doi.org/10.3390/galaxies6040125.

Texte intégral

Résumé :

BL Lacertae objects constitute a rare class of active galactic nuclei with extreme observational features attributed to the Doppler-boosted emission from a relativistic jet, closely aligned to our line-of-sight. Their spectral energy distribution, extending over 17–19 orders of frequency from radio to the TeV energy range, is of non-thermal origin and shows a typical two-component structure. The lower-energy component, ranging from the radio to X-rays in the high-energy peaked BL Lacertae sources, is widely accepted to be a synchrotron radiation emitted by ultra-relativistic charged particles, to be initially accelerated via the Blandford–Znajek mechanism or magneto-hydrodynamic processes in the vicinity of the central super-massive black hole. However, the accelerated particles should lose the energy, sufficient for the emission of the keV-GeV photons, very quickly and the source can maintain its flaring state on the daily-weekly timescales only if some additional acceleration mechanisms are continuously at work. According to different studies and simulations,the particles can gain tremendous energies due to the propagation of relativistic shocks through the jet: By means of first-order Fermi mechanism at the shock front, or they undergo an efficient stochastic (second-order Fermi) acceleration close to the shock front, in the turbulent jet medium. Our intensive X-ray spectral study of TeV-detected, bright BL Lacertae objects (Mrk 421, 1ES 1959+650, Mrk 501) often show the signatures of the stochastic acceleration, while those related to the first-order Fermi process arefound relatively rarely. The TeV-undetected sources (1H 1516+660, BZB J1341+3959, BZB J1237+6258) mostly do not show the signatures of the efficient stochastic acceleration in their jets.

Styles APA, Harvard, Vancouver, ISO, etc.

41

Gottschalk, Hannes C., Taija L. Fischer, Volker Meyer, Reinhard Hildebrandt, Ulrich Schmitt et Martin A. Suhm. « A Sustainable Slit Jet FTIR Spectrometer for Hydrate Complexes and Beyond ». Instruments 5, n^o 1 (17 mars 2021) : 12. http://dx.doi.org/10.3390/instruments5010012.

Texte intégral

Résumé :

Fourier transform infrared (FTIR) absorption spectroscopy of cold molecules and clusters in supersonic slit jet expansions complements and extends more sensitive action spectroscopy techniques and provides important reference data for the latter. We describe how its major drawback, large substance and carrier gas consumption, can be alleviated by one to two orders of magnitude via direct and continuous recycling of the gas mixture. This is achieved by a combination of dry rotary lobe and screw pump compression. The signal-to-noise ratio is boosted by the established buffered giant gas pulse technique with full interferogram synchronization. The buildup of water impurities typically limits the recycling gain, but is turned into a feature for the study of hydrate complexes of volatile molecules. Continuous operation with a single gas filling over several days becomes practical and useful. Decadic absorbances in the low ppm range are detectable and the mid infrared range can be recorded simultaneously with the near infrared. The less straightforward hydration number assignment of spectral features in direct absorption spectroscopy is supported by a gradual water buildup at a rate of less than 0.5 mg/h. A recent reassignment proposal for the water dimer OH stretching spectrum is refuted and vibrational spectra of vacuum-isolated 18O-water clusters are presented for the first time. Methanol docking on asymmetric ketones is used to illustrate the advantages and limitations of the recycling concept. Previous assignments of the hydrate complex of 1-phenylethanol are confirmed. Additional features of the setup await testing and refinement, but the recycling technique already substantially widens the applicability of direct absorption spectroscopy of neutral molecular clusters. It may be attractive for other high-throughput jet spectrometers.

Styles APA, Harvard, Vancouver, ISO, etc.

42

Liu, Da, Jia Liu, Carlos E. M. Wagner et Xiao-Ping Wang. « Bottom-quark forward–backward asymmetry, dark matter and the LHC ». International Journal of Modern Physics A 34, n^o 13n14 (20 mai 2019) : 1940009. http://dx.doi.org/10.1142/s0217751x19400098.

Texte intégral

Résumé :

The LEP experiment at CERN provided accurate measurements of the [Formula: see text] neutral gauge boson properties. Although all measurements agree well with the SM predictions, the forward–backward asymmetry of the bottom-quark remains almost [Formula: see text] away from the SM value. We proposed that this anomaly may be explained by the existence of a new [Formula: see text] gauge boson, which couples with opposite charges to the right-handed components of the bottom and charm quarks. Cancellation of gauge anomalies demands the presence of a vector-like singlet charged lepton as well as a neutral Dirac (or Majorana) particle that provides a dark matter candidate. Constraints from precision measurements imply that the mass of the new gauge boson should be around 115 GeV. We discuss the experimental constraints on this scenario, including the existence of a di-jet resonance excess at an invariant mass similar to the mass of this new gauge boson, observed in boosted topologies at the CMS experiment.

Styles APA, Harvard, Vancouver, ISO, etc.

43

Gong, Guo, Linying Zhang, Haijun Yuan, Jianbing Jiang, Min Ouyang et Lijian Xu. « Second Step Aging on Nanosized Precipitates and Properties of Al–Zn–Mg–Cu–Cr Spray-Deposited Alloys ». Journal of Nanoscience and Nanotechnology 20, n^o 3 (1 mars 2020) : 1955–61. http://dx.doi.org/10.1166/jnn.2020.17342.

Texte intégral

Résumé :

The effects of second step aging (T76, T74, T73) on nano-sized precipitates and properties of Al–Zn–Mg–Cu–Cr spray-deposited alloys were explored through tensile tester, impact testing machine, metallographic microscope (OM), eddy-current device, scanning electron microscopy (SEM), twin-jet electro-polishing machine and transmission electron microscopy (TEM). Fine grain size (compared with as-deposited billet) and directional microstructures were obtained. T76 heat treatment of the alloy provided higher tensile strength, yield strength, impact toughness and hardness which were 767 MPa, 708 MPa, 39.41 J/cm1/2 99.1 HRB, respectively in comparison with T74 and T73 samples. However, they provided lower elongation and electrical conductivity which were 7.6% and 31.1% IACS, respectively in comparison with T74 and T73 samples. This resulted from the larger quantity and volume of tiny η′ precipitates that distribute homogeneously in matrix. However, coarse precipitates with increasing second step aging time (T74, T73) made wider grain boundary width and discontinuous η precipitates boosted conductivity of the Al–Zn–Mg–Cu–Cr alloy. Furthermore, proportion of white precipitated phase in the matrix decreased slightly and volume became larger with increasing second step aging time.

Styles APA, Harvard, Vancouver, ISO, etc.

44

Cao, Meichun, et Zhaohui Lin. « Impact of Urban Surface Roughness Length Parameterization Scheme on Urban Atmospheric Environment Simulation ». Journal of Applied Mathematics 2014 (2014) : 1–14. http://dx.doi.org/10.1155/2014/267683.

Texte intégral

Résumé :

In this paper, the impact of urban surface roughness lengthz0parameterization scheme on the atmospheric environment simulation over Beijing has been investigated through two sets of numerical experiments using the Weather Research and Forecasting model coupled with the Urban Canopy Model. For the control experiment (CTL), the urban surfacez0parameterization scheme used in UCM is the model default one. For another experiment (EXP), a newly developed urban surfacez0parameterization scheme is adopted, which takes into account the comprehensive effects of urban morphology. The comparison of the two sets of simulation results shows that all the roughness parameters computed from the EXP run are larger than those in the CTL run. The increased roughness parameters in the EXP run result in strengthened drag and blocking effects exerted by buildings, which lead to enhanced friction velocity, weakened wind speed in daytime, and boosted turbulent kinetic energy after sunset. Thermal variables (sensible heat flux and temperature) are much less sensitive toz0variations. In contrast with the CTL run, the EXP run reasonably simulates the observed nocturnal low-level jet. Besides, the EXP run-simulated land surface-atmosphere momentum and heat exchanges are also in better agreement with the observation.

Styles APA, Harvard, Vancouver, ISO, etc.

45

Cecere, Giovanni, Adrian Irimescu et Simona Silvia Merola. « Design of an Optically Accessible Intake Manifold for Characterization of Liquid and Gaseous Jets in PFI Operating Conditions ». Designs 7, n^o 1 (1 février 2023) : 24. http://dx.doi.org/10.3390/designs7010024.

Texte intégral

Résumé :

The intake manifold and its components play a key role in the proper formation of air–fuel mixtures suitable for correct engine operation. In this article, starting from the original intake manifold design fitted to an optically accessible spark-ignited engine, a new solution was developed so as to allow the application of high-speed imaging of the fuel jet located between the runner and intake valves (Port Fuel Injection). To compare the two designs in terms of overall engine performance parameters such as volumetric efficiency, 0D/1D simulations were performed in motored conditions. Measurements at different crankshaft speed values were used for calibrating the intake line parameters and providing boundary conditions. Finite Element Analysis (FEM) was performed in SolidWorks to verify the structural strength of the new design when operating in the most critical conditions, i.e., boosted operation. As an overall conclusion, the results show that the new design guarantees a wider range of intake pressure values during the intake stroke, thus expanding the possible operative points. This can be obtained without compromising structural integrity, given that predicted safety factors were well above acceptable limits even for relatively high boost levels.

Styles APA, Harvard, Vancouver, ISO, etc.

46

Robles, Mary, Odile Peyron, Guillemette Ménot, Elisabetta Brugiapaglia, Sabine Wulf, Oona Appelt, Marion Blache et al. « Climate changes during the Late Glacial in southern Europe : new insights based on pollen and brGDGTs of Lake Matese in Italy ». Climate of the Past 19, n^o 2 (23 février 2023) : 493–515. http://dx.doi.org/10.5194/cp-19-493-2023.

Texte intégral

Résumé :

Abstract. The Late Glacial (14 700–11 700 cal BP) is a key climate period marked by rapid but contrasted changes in the Northern Hemisphere. Indeed, regional climate differences have been evidenced during the Late Glacial in Europe and the northern Mediterranean. However, past climate patterns are still debated since temperature and precipitation changes are poorly investigated towards the lower European latitudes. Lake Matese in southern Italy is a key site in the central Mediterranean to investigate climate patterns during the Late Glacial. This study aims to reconstruct climate changes and their impacts at Matese using a multi-proxy approach including magnetic susceptibility, geochemistry (XRF core scanning), pollen data and molecular biomarkers like branched glycerol dialkyl glycerol tetraethers (brGDGTs). Paleotemperatures and paleo-precipitation patterns are quantitatively inferred from pollen assemblages (multi-method approach: modern analogue technique, weighted averaging partial least-squares regression, random forest and boosted regression trees) and brGDGT calibrations. The results are compared to a latitudinal selection of regional climate reconstructions in Italy to better understand climate processes in Europe and in the circum-Mediterranean region. A warm Bølling–Allerød and a marked cold Younger Dryas are revealed in all climate reconstructions inferred from various proxies (chironomids, ostracods, speleothems, pollen, brGDGTs), showing no latitudinal differences in terms of temperatures across Italy. During the Bølling–Allerød, no significant changes in terms of precipitation are recorded; however, a contrasted pattern is visible during the Younger Dryas. Slightly wetter conditions are recorded south of 42∘ N, whereas dry conditions are recorded north of 42∘ N. During the Younger Dryas, cold conditions can be attributed to the southward position of North Atlantic sea ice and of the polar frontal jet stream, whereas the increase in precipitation in southern Italy seems to be linked to relocation of Atlantic storm tracks into the Mediterranean, induced by the Fennoscandian ice sheet and the North European Plain. By contrast, warm conditions during the Bølling–Allerød can be linked to the northward position of North Atlantic sea ice and of the polar frontal jet stream.

Styles APA, Harvard, Vancouver, ISO, etc.

47

Ali Zaidi, Syed Zulfiqar, Syed Tauseef Mohyud-din et Bandar Bin-Mohsen. « A comparative study of wall jet flow containing carbon nanotubes with convective heat transfer and MHD ». Engineering Computations 34, n^o 3 (2 mai 2017) : 739–53. http://dx.doi.org/10.1108/ec-03-2016-0087.

Texte intégral

Résumé :

Purpose The purpose of this study is to conduct a comparative investigation for incompressible electrically conducting nanofluid fluid through wall jet. Single-walled carbon nanotubes (SWCNTs) and multiple-walled carbon nanotubes (MWCNTs) are considered as the nanoparticles. To record the effect of Lorentz forces, a magnetic field is applied normally with the assumption that the induced magnetic field is negligible. Design/methodology/approach Boundary layer approximation is used to convert governing equations into ordinary differential equations along with appropriate boundary conditions. To obtain the results, used homotopy analysis method (HAM) has been used as an analytical technique and to validate the obtained results a famous numerical Runge–Kutta–Fehlberg method is also exploited. It has been observed that the results obtained through both of the methods are in excellent agreement with exact solution. Findings The Hartmann number is used as controlling parameter for velocity and temperature profile. That can be recorded as its extended values help to normalize the velocity, whereas it controls the rapid increase in temperature. The temperature profile is boosted by increasing the value of the Biot number, a physical parameter. Similarly, it also increases for an increased percentage of volume fraction of particles (SWCNTs/MWCNTs). The Hartmann number plays an important role in decreasing local skin friction coefficient. The influence of the Biot number and volume fraction of nanoparticles caused similar increasing effects on the local Nusselt number. Nanoparticles of the form SWCNT provide better heat transfer as compared to MWCNTs. Influence of the Biot number and volume fraction of nanoparticles caused similar increasing effects on the local Nusselt number. Nanoparticles of the form SWCNT provide better heat transfer as compared to MWCNTs. Originality/value To gain insight into the problem, the effects of various emerging parameters and physical quantities such as Biot number, Nusselt number and skin friction coefficient, have been explored.

Styles APA, Harvard, Vancouver, ISO, etc.

48

Aaboud, M., G. Aad, B. Abbott, O. Abdinov, B. Abeloos, S. H. Abidi, O. S. AbouZeid et al. « Search for light resonances decaying to boosted quark pairs and produced in association with a photon or a jet in proton–proton collisions at s=13TeV with the ATLAS detector ». Physics Letters B 788 (janvier 2019) : 316–35. http://dx.doi.org/10.1016/j.physletb.2018.09.062.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

49

Schätzel, Sebastian. « Boosted top quarks and jet structure ». European Physical Journal C 75, n^o 9 (septembre 2015). http://dx.doi.org/10.1140/epjc/s10052-015-3636-x.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

50

Kitadono, Yoshio, et Hsiang-nan Li. « Jet substructures of boosted polarized top quarks ». Physical Review D 89, n^o 11 (2 juin 2014). http://dx.doi.org/10.1103/physrevd.89.114002.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Articles de revues sur le sujet « Boosted-jet »

Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres