2,008 research outputs found
Particle contact laws and their properties for simulation of fluid-sediment interaction with coupled SPH-DEM model
The transport of sediment due to the interaction of fluid and solids is a prevalent geophysical process. The detailed modelling of the interaction between the fluid and the sediment particles is still a challenging task. In the present study we model the fluid phase by smoothed particle hydrodynamics (SPH) using the classical approach where the fluid is assumed to be weakly compressible. The sediment, in terms of solid spheres made of granite, is modelled by the discrete element method (DEM). Both of them are meshfree particle methods but SPH is a continuum approach and DEM describes the motion and interaction of discrete solid objects. The interaction between SPH and DEM particles is modelled as particle-to-particle contact in combination with a boundary condition at the solid interface. Therefore, a contact law is used to capture the collision process and to ensure balancing of collision forces. In doing so, two contact types have to be modelled, i.e. sediment-sediment and fluid-sediment. The approach and properties these contact types are presented in detail. Advantages and drawbacks of the approaches are discussed based on examples
Fused Spectatorship: Designing Bodily Experiences Where Spectators Become Players
Spectating digital games can be exciting. However, due to its vicarious
nature, spectators often wish to engage in the gameplay beyond just watching
and cheering. To blur the boundaries between spectators and players, we propose
a novel approach called ''Fused Spectatorship'', where spectators watch their
hands play games by loaning bodily control to a computational Electrical Muscle
Stimulation (EMS) system. To showcase this concept, we designed three games
where spectators loan control over both their hands to the EMS system and watch
them play these competitive and collaborative games. A study with 12
participants suggested that participants could not distinguish if they were
watching their hands play, or if they were playing the games themselves. We
used our results to articulate four spectator experience themes and four fused
spectator types, the behaviours they elicited and offer one design
consideration to support each of these behaviours. We also discuss the ethical
design considerations of our approach to help game designers create future
fused spectatorship experiences.Comment: This paper is going to be published at Annual Symposium on
Computer-Human Interaction in Play (CHI PLAY) 202
Pharmacokinetic modeling of intravenous sildenafil in newborns with congenital diaphragmatic hernia
Purpose: We developed a pharmacokinetic model of intravenous sildenafil in newborns with congenital diaphragmatic hernia (CDH) to achieve a target plasma concentration of over 50 μg/l. Methods: Twenty-three CDH newborns with pulmonary hypertension (64 blood samples) received intravenous sildenafil. Patients received a loading dose of 0.35 mg/kg (IQR 0.16 mg/kg) for 3 h, followed by a continuous infusion of 1.5 mg/kg/day (IQR 0.1 mg/kg/day). For model development, non-linear mixed modeling was used. Inter-individual variability (IIV) and inter-occasion variability were tested. Demographic and laboratory parameters were evaluated as covariates. Normalized prediction distribution errors (NPDE) and visual predictive check (VPC) were used for model validation. Results: A two-compartment disposition model of sildenafil and a one-compartment disposition model of desmethyl sildenafil (DMS) was observed with IIV in sildenafil and DMS clearance and volume of distribution of sildenafil. NPDE and VPC revealed adequate predictability. Only postnatal age increased sildenafil clearance. This was partly compensated by a higher DMS concentration, which also has a therapeutic effect. In this small group of patients, sildenafil was tolerated well. Conclusions: This model for sildenafil in CDH patients shows that concentration-targeted sildenafil dosing of 0.4 mg/kg in 3 h, followed by 1.6 mg/kg/day continuous infusion achieves appropriate sildenafil plasma levels
Next-to-leading order QCD corrections to inclusive-hadron photoproduction in polarized lepton-proton collisions
We calculate the next-to-leading order QCD corrections to the `direct' part
of the spin-dependent cross section for single-inclusive charged-hadron
photoproduction. This process could be studied experimentally in future
polarized fixed-target lepton-nucleon experiments, but also at the HERA ep
collider after an upgrade to both beams being polarized. We present a brief
numerical evaluation of our results by studying the K-factors and the scale
dependence of the NLO cross section.Comment: 25 Pages, LaTeX, 4 figures as eps file
Phenomenology of event shapes at hadron colliders
We present results for matched distributions of a range of dijet event shapes
at hadron colliders, combining next-to-leading logarithmic (NLL) accuracy in
the resummation exponent, next-to-next-to leading logarithmic (NNLL) accuracy
in its expansion and next-to-leading order (NLO) accuracy in a pure alpha_s
expansion. This is the first time that such a matching has been carried out for
hadronic final-state observables at hadron colliders. We compare our results to
Monte Carlo predictions, with and without matching to multi-parton tree-level
fixed-order calculations. These studies suggest that hadron-collider event
shapes have significant scope for constraining both perturbative and
non-perturbative aspects of hadron-collider QCD. The differences between
various calculational methods also highlight the limits of relying on
simultaneous variations of renormalisation and factorisation scale in making
reliable estimates of uncertainties in QCD predictions. We also discuss the
sensitivity of event shapes to the topology of multi-jet events, which are
expected to appear in many New Physics scenarios.Comment: 70 pages, 25 figures, additional material available from
http://www.lpthe.jussieu.fr/~salam/pp-event-shapes
Deep strong light-matter coupling in plasmonic nanoparticle crystals
In the regime of deep strong light–matter coupling, the coupling strength exceeds the transition energies of the material, fundamentally changing its properties; for example, the ground state of the system contains virtual photons and the internal electromagnetic field gets redistributed by photon self-interaction. So far, no electronic excitation of a material has shown such strong coupling to free-space photons. Here we show that three-dimensional crystals of plasmonic nanoparticles can realize deep strong coupling under ambient conditions, if the particles are ten times larger than the interparticle gaps. The experimental Rabi frequencies (1.9 to 3.3 electronvolts) of face-centred cubic crystals of gold nanoparticles with diameters between 25 and 60 nanometres exceed their plasmon energy by up to 180 per cent. We show that the continuum of photons and plasmons hybridizes into polaritons that violate the rotating-wave approximation. The coupling leads to a breakdown of the Purcell effect—the increase of radiative damping through light–matter coupling—and increases the radiative polariton lifetime. The results indicate that metallic and semiconducting nanoparticles can be used as building blocks for an entire class of materials with extreme light–matter interaction, which will find application in nonlinear optics, the search for cooperative effects and ground states, polariton chemistry and quantum technology
Limiting fragmentation in hadron-hadron collisions at high energies
Limiting fragmentation in proton-proton, deuteron-nucleus and nucleus-nucleus
collisions is analyzed in the framework of the Balitsky-Kovchegov equation in
high energy QCD. Good agreement with experimental data is obtained for a wide
range of energies. Further detailed tests of limiting fragmentation at RHIC and
the LHC will provide insight into the evolution equations for high energy QCD.Comment: 28 pages, 10 figures (2 new figures, text slightly expanded, and some
additional references
Azimuthal and Single Spin Asymmetries in Hard Scattering Processes
In this article we review the present understanding of azimuthal and single
spin asymmetries for inclusive and semi-inclusive particle production in
unpolarized and polarized hadronic collisions at high energy and moderately
large transverse momentum. After summarizing the experimental information
available, we discuss and compare the main theoretical approaches formulated in
the framework of perturbative QCD. We then present in some detail a
generalization of the parton model with inclusion of spin and intrinsic
transverse momentum effects. In this context, we extensively discuss the
phenomenology of azimuthal and single spin asymmetries for several processes in
different kinematical configurations. A comparison with the predictions of
other approaches, when available, is also given. We finally emphasize some
relevant open points and challenges for future theoretical and experimental
investigation.Comment: 70 pages, 34 ps figures. Invited review paper to be published in
Progress in Particle and Nuclear Physic
Massively distributed authorship of academic papers
Wiki-like or crowdsourcing models of collaboration can provide a number of benefits to academic work. These techniques may engage expertise from different disciplines, and potentially increase productivity. This paper presents a model of massively distributed collaborative authorship of academic papers. This model, developed by a collective of thirty authors, identifies key tools and techniques that would be necessary or useful to the writing process. The process of collaboratively writing this paper was used to discover, negotiate, and document issues in massively authored scholarship. Our work provides the first extensive discussion of the experiential aspects of large-scale collaborative research.Peer ReviewedPostprint (author's final draft
Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at s√=8 TeV with ATLAS
Measurements of fiducial and differential cross sections are presented for Higgs boson production in proton-proton collisions at a centre-of-mass energy of s√=8 TeV. The analysis is performed in the H → γγ decay channel using 20.3 fb−1 of data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The signal is extracted using a fit to the diphoton invariant mass spectrum assuming that the width of the resonance is much smaller than the experimental resolution. The signal yields are corrected for the effects of detector inefficiency and resolution. The pp → H → γγ fiducial cross section is measured to be 43.2 ±9.4(stat.) − 2.9 + 3.2 (syst.) ±1.2(lumi)fb for a Higgs boson of mass 125.4GeV decaying to two isolated photons that have transverse momentum greater than 35% and 25% of the diphoton invariant mass and each with absolute pseudorapidity less than 2.37. Four additional fiducial cross sections and two cross-section limits are presented in phase space regions that test the theoretical modelling of different Higgs boson production mechanisms, or are sensitive to physics beyond the Standard Model. Differential cross sections are also presented, as a function of variables related to the diphoton kinematics and the jet activity produced in the Higgs boson events. The observed spectra are statistically limited but broadly in line with the theoretical expectations
- …