Search results for "Fysik"
showing 10 items of 292 documents
First measurement of the |t|-dependence of coherent J/ψ photonuclear production
2021
The first measurement of the dependence on $|t|$, the square of the momentum transferred between the incoming and outgoing target nucleus, of coherent J/ψ photoproduction is presented. The data were measured with the ALICE detector in ultra-peripheral Pb-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}} = 5.02$ TeV with the J/$\psi$ produced in the central rapidity region $|y| < 0.8$, which corresponds to the small Bjorken-$x$ range $(0.3 − 1.4) \times 10 ^{−3}$. The measured $|t|$-dependence is not described by computations based only on the Pb nuclear form factor, while the photonuclear cross section is better reproduced by models including shadowing according t…
Fysikaalinen valaistus ja reaaliaikaiset heijastukset
2016
Epäsuora valaistus, kuten ympäristön heijastukset, ovat tärkeä osa uskottavaa tietokonegrafiikkaa. Tarvitaan kuitenkin fysikaalinen valaistusmalli, jotta epäsuoran valon vaikutus olisi realistinen. Vasta viime aikojen näytönohjainten tehokkuuden kasvu on mahdollistanut fysikaalisen epäsuoran valaistuksen mallintamisen reaaliajassa. Koska epäsuoran valaistuksen laskeminen on erittäin raskasta, joudutaan kuitenkin tekemään arviointia, jotta reaaliaikainen toteutus olisi mahdollista. Tässä tutkielmassa esitellään fysikaalisen valaistuksen perustaa ja annetaan esimerkkejä reaaliaikaisista heijastusmenetelmistä. Lopuksi evaluoidaan kahta heijastustekniikkaa, ympäristötutkaimia ja kuvapuskuriheij…
Kahden viikon laitoskuntoutuksen vaikutus koettuun kipuun ja kaularangan isometriseen maksimilihasvoimaan kroonisilla niskaoireisilla henkilöillä : k…
2001
Analysis of fluid flow through porous media based on x-ray micro-tomographic reconstructions
2010
This thesis deals with creeping fluid flow through fibrous porous materials. Permeability through a porous medium is a measure of the ability of the material to transmit fluids. For testing and demonstration purposes the permeability values of a few fibrous heterogeneous materials, namely synthetic non-woven felt, wet pressing felt, cardboard, newsprint and hardwood paper, were measured experimentally. Reconstructions of the same materials under similar compression states were captured by x-ray micro-tomography. The actual microscopic pore structure thus obtained was utilised in the numerical lattice-Boltzmann analysis for solving the fluid flow permeability of the materials. Agreement betw…
Change detection to tone pairs during the first year of life : Predictive longitudinal relationships for EEG-based source and time-frequency measures
2019
Brain responses related to auditory processing show large changes throughout infancy and childhood with some evidence that the two hemispheres might mature at different rates. Differing rates of hemispheric maturation could be linked to the proposed functional specialization of the hemispheres in which the left auditory cortex engages in analysis of precise timing information whereas the right auditory cortex focuses on analysis of sound frequency. Here the auditory change detection process for rapidly presented tone-pairs was examined in a longitudinal sample of infants at the age of 6 and 12 months using EEG. The ERP response related to change detection of a frequency contrast, its estima…
Measurement of the low-energy antideuteron inelastic cross section
2020
In this Letter, we report the first measurement of the inelastic cross section for antideuteron-nucleus interactions at low particle momenta, covering a range of $0.3 \leq p < 4$ GeV/$c$. The measurement is carried out using p-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV, recorded with the ALICE detector at the CERN LHC and utilizing the detector material as an absorber for antideuterons and antiprotons. The extracted raw primary antiparticle-to-particle ratios are compared to the results from detailed ALICE simulations based on the GEANT4 toolkit for the propagation of antiparticles through the detector material. The analysis of th…
Measurement of Atmospheric Neutrino Oscillations at 6–56 GeV with IceCube DeepCore
2018
We present a measurement of the atmospheric neutrino oscillation parameters using three years of data from the IceCube Neutrino Observatory. The DeepCore infill array in the center of IceCube enables the detection and reconstruction of neutrinos produced by the interaction of cosmic rays in Earth's atmosphere at energies as low as ∼5 GeV. That energy threshold permits measurements of muon neutrino disappearance, over a range of baselines up to the diameter of the Earth, probing the same range of L/Eν as long-baseline experiments but with substantially higher-energy neutrinos. This analysis uses neutrinos from the full sky with reconstructed energies from 5.6 to 56 GeV. We measure Δm322=2.31…
Monitoring and data quality assessment of the ATLAS liquid argon calorimeter
2014
The liquid argon calorimeter is a key component of the ATLAS detector installed at the CERN Large Hadron Collider. The primary purpose of this calorimeter is the measurement of electron and photon kinematic properties. It also provides a crucial input for measuring jets and missing transverse momentum. An advanced data monitoring procedure was designed to quickly identify issues that would affect detector performance and ensure that only the best quality data are used for physics analysis. This article presents the validation procedure developed during the 2011 and 2012 LHC data-taking periods, in which more than 98% of the proton-proton luminosity recorded by ATLAS at a centre-of-mass ener…
Exploration of jet substructure using iterative declustering in pp and Pb–Pb collisions at LHC energies
2020
The ALICE collaboration at the CERN LHC reports novel measurements of jet substructure in pp collisions at $\sqrt{s}$= 7 TeV and central Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV. Jet substructure of track-based jets is explored via iterative declustering and grooming techniques. We present the measurement of the momentum sharing of two-prong substructure exposed via grooming, the $z_{\rm{g}}$, and its dependence on the opening angle, in both pp and Pb-Pb collisions. We also present the first measurement of the distribution of the number of branches obtained in the iterative declustering of the jet, which is interpreted as the number of its hard splittings. In Pb-Pb collisions, we…
In vivo muscle mechanics during human locomotion : fascicle-tendinous tissue interaction during stretch-shortening cycle exercises
2005
Masaki Ishikawan tutkimuksessa selvitettiin, kuinka lihasten ja jännerakenteiden yhteistoiminta hyödyntää elastista energiaa ihmisen liikkumisessa. Ulomman reisilihaksen ja kolmipäisen pohjelihaksen lihassolujen ja jännerakenteiden pituuden muutoksia tarkasteltiin liikkeiden aikana ultraäänitekniikalla yhdessä ainutlaatuisen jänteen voimaa mittaavan optisen kuituanturin kanssa. The present series of studies were designed to examine how the interaction between muscle fibers and tendinous tissues (TT) were modulated for effective utilization of elastic energy during stretch-shortening cycle (SSC) exercises. By combining the in vivo direct recordings of tendon force with fascicle length change…