Creeping thermocapillary motion of a Newtonian droplet suspended in a viscoelastic fluid

In this work we consider theoretically the problem of a Newtonian droplet moving in an otherwise quiescent infinite viscoelastic fluid under the influence of an externally applied temperature gradient. The outer fluid is modelled by the Oldroyd-B equation, and the problem is solved for small Weissenberg and Capillary numbers in terms of a double perturbation expansion. We assume microgravity conditions and neglect the convective transport of energy and momentum. We derive expressions for the droplet migration speed and its shape in terms of the properties of both fluids. In the absence of shape deformation, the droplet speed decreases monotonically for sufficiently viscous inner fluids, while for fluids with a smaller inner-to-outer viscosity ratio, the droplet speed first increases and then decreases as a function of the Weissenberg number. For small but finite values of the Capillary number, the droplet speed behaves monotonically as a function of the applied temper-ature gradient for a fixed ratio of the Capillary and Weissenberg numbers. We demonstrate that this behaviour is related to the polymeric stresses de-forming the droplet in the direction of its migration, while the associated changes in its speed are Newtonian in nature, being related to a change in the droplet’s hydrodynamic resistance and its internal temperature distribu-tion. When compared to the results of numerical simulations, our theory exhibits a good predictive power for sufficiently small values of the Capillary and Weissenberg numbers

Effect of deuterium implantation dose on properties of CrN coatings

The methods of X-ray diffraction analysis, atomic-force microscopy, nanoindentation and thermodesorption spectroscopy have been applied to investigate the effect of a dose (from 5∙10¹⁶ to 1.5∙10¹⁸ D/сm²) of implanted deuterium with energy of 24 keV on the structure, surface morphology and mechanical properties of vacuum-arc CrN coatings. Deuterium ion implantation in the range of doses from 5∙10¹⁶ to 1.5∙10¹⁷ D/сm² decreases by 10…15% the nanohardness and elastic modulus of coatings. Under exposition to doses ≥ 1∙10¹⁸ D/сm² the coating nanohardness sharply decreases because of blisters being formed and occupying about 30% of the CrN coating surface. Deuterium implantation did not lead to formation of new phases in the CrN coating.Методами рентгеноструктурного аналізу, атомно-силової мікроскопії, наноіндентування і термодесорбційної спектроскопії досліджено вплив дози (5∙10¹⁶…1.5∙10¹⁸ D/см²) імплантованого дейтерію з енергією 24 кеВ на структуру, морфологію поверхні та механічні властивості вакуумно-дугових покриттів CrN. Імплантований дейтерій в інтервалі доз 5∙10¹⁶…1.5∙10¹⁷ D/см² призводить до зменшення на 10…15% нанотвердості і модуля пружності покриттів. Опромінення дозами ≥ 1∙10¹⁸ D/см² викликає різке зниження нанотвердості покриттів через формування блістерів, які займають близько 30% поверхні покриття CrN. Імплантація дейтерію не призводить до утворення нових фаз у покритті CrN.Методами рентгеноструктурного анализа, атомно-силовой микроскопии, наноиндентирования и термодесорбционной спектроскопии исследовано влияния дозы (5∙10¹⁶…1,5∙10¹⁸ D/см²) имплантированного дейтерия с энергией 24 кэВ на структуру, морфологию поверхности и механические свойства вакуумно-дуговых покрытий CrN. Имплантированный дейтерий в интервале доз 5∙10¹⁶…5∙10¹⁷ D/см² приводит к уменьшению на 10…15% нанотвердости и модуля упругости покрытий. Облучение дозами ≥ 1∙10¹⁸ D/см² вызывает резкое снижение нанотвердости покрытий из-за формирования блистеров, которые занимают около 30% поверхности покрытия CrN. Имплантация дейтерия не приводит к образованию новых фаз в покрытии CrN

Project of deuteron accelerator based neutron source for rib production

The project of a high-intense neutron source for the SPES project in LNL, Legnaro, Italy [1] is developed. The source is based on the rotating carbon target. The target is bombarded by the deuteron beam with energy 20 MeV, diameter 1 cm, average power 100 kW. The target is cooled by its thermal radiation, and its temperature can reach 1800ºC. It is shown that high density graphite can be used as a material for neutron production. The source can produce up to 10¹⁴ neutrons per second with energy within few MeV - few dozens MeV range, its lifetime is around few thousand hours

Mapping of periodically poled crystals via spontaneous parametric down-conversion

A new method for characterization of periodically poled crystals is developed based on spontaneous parametric down-conversion. The method is demonstrated on crystals of Y:LiNbO3, Mg:Y:LiNbO3 with non-uniform periodically poled structures, obtained directly under Czochralski growth procedure and designed for application of OPO in the mid infrared range. Infrared dispersion of refractive index, effective working periods and wavelengths of OPO were determined by special treatment of frequency-angular spectra of spontaneous parametric down-conversion in the visible range. Two-dimensional mapping via spontaneous parametric down-conversion is proposed for characterizing spatial distribution of bulk quasi-phase matching efficiency across the input window of a periodically poled sample.Comment: 19 pages, 6 figure

Project of a fast neutron target based on a 10 MeV 300 kW proton accelerator

Project of targets for high intense neutron source is proposed. The source is based on a proton continuous accelerator with the 10 MeV particle energy and up to 300 kW mean beam power. Problems of fabrication of these targets are discussed. Hot solid state and liquid target designs are considered. Maximum admissible target parameters are presented. Advantages and disadvantages of various types of target for neutron production are discussed

Stochastic Approximation to Understand Simple Simulation Models

This paper illustrates how a deterministic approximation of a stochastic process can be usefully applied to analyse the dynamics of many simple simulation models. To demonstrate the type of results that can be obtained using this approximation, we present two illustrative examples which are meant to serve as methodological references for researchers exploring this area. Finally, we prove some convergence results for simulations of a family of evolutionary games, namely, intra-population imitation models in n-player games with arbitrary payoffs.Ministerio de Educación (JC2009- 00263), Ministerio de Ciencia e Innovación (CONSOLIDER-INGENIO 2010: CSD2010-00034, DPI2010-16920

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters