307 research outputs found
Study of the first paramagnetic to ferromagnetic transition in as prepared samples of Mn-Fe-P-Si magnetocaloric compounds prepared by different synthesis routes
International audienceMagnetocaloric materials with composition of Mn 1.3 Fe 0.65 P 0.5 Si 0.5 have been prepared by ball milling and solid-state reaction methods and consolidated using powder annealing, and conventional and spark plasma sintering. Magnetic and calorimetric measurements show remarkable differences upon first cooling, and slight differences on second and further coolings between the samples prepared by different synthesis routes. Further measurements using Hall probe imaging in high magnetic field have been also carried out. As-prepared samples have been cooled down just above the critical temperature, and the first phase transition has been induced by application of a magnetic field. Bulk samples show staircase isothermal magnetization curves whereas powders show smoother transition curves
Research of strengthening process of machines details surfaces by treatment spark digits
Розраховано математичне сподівання площі зміцненої поверхні деталі шляхом обробки імпульсами одиничних іскрових розрядів, яке залежить від кількості розрядів та їх площі. Досліджено залежність частки зміцненої поверхні від кількості імпульсів розряду при різних значеннях їх площі та від величини площі одиничного розряду при дії різною кількістю розрядів. Аналіз отриманих результатів свідчить про необхідність урахування площі одиничного іскрового розряду та їх кількості при розробленні технології зміцнення деталей машин.The mathematical hope of area of the fixed detail surface is calculated by treatment of high spark bits impulses, which depends on the amount of digits and their area. Dependence of part of the fixed surface is investigational on the amount of impulses of digit at the different values of their area and from the size of area of high bit at the action of digits a different amount. An analysis of investigated results testifies to the necessity of account of area of high bit and their amount at development of technology of strengthening of details of machines
Elastic Spin Relaxation Processes in Semiconductor Quantum Dots
Electron spin decoherence caused by elastic spin-phonon processes is
investigated comprehensively in a zero-dimensional environment. Specifically, a
theoretical treatment is developed for the processes associated with the
fluctuations in the phonon potential as well as in the electron procession
frequency through the spin-orbit and hyperfine interactions in the
semiconductor quantum dots. The analysis identifies the conditions (magnetic
field, temperature, etc.) in which the elastic spin-phonon processes can
dominate over the inelastic counterparts with the electron spin-flip
transitions. Particularly, the calculation results illustrate the potential
significance of an elastic decoherence mechanism originating from the
intervalley transitions in semiconductor quantum dots with multiple equivalent
energy minima (e.g., the X valleys in SiGe). The role of lattice anharmonicity
and phonon decay in spin relaxation is also examined along with that of the
local effective field fluctuations caused by the stochastic electronic
transitions between the orbital states. Numerical estimations are provided for
typical GaAs and Si-based quantum dots.Comment: 57 pages, 14 figure
Adsorption of phenol and 2,4-dichlorophenol on carbon-containing sorbent produced from sugar cane bagasse
An adsorbent prepared from carbonized sugar cane bagasse Cl shows high adsorption capacity to phenol and 2,4-dichlorophenol that is equal to 2.24 and 2.45 mmol g-1, respectivel
Charge Radii and Magnetic Polarizabilities of the Rho and K* Mesons in QCD String Theory
The effective action for light mesons in the external uniform static
electromagnetic fields was obtained on the basis of QCD string theory. We imply
that in the presence of light quarks the area law of the Wilson loop integral
is valid. The approximation of the Nambu-Goto straight-line string is used to
simplify the problem. The Coulomb-like short-range contribution which goes from
one-gluon exchange is also neglected. We do not take into account spin-orbital
and spin-spin interactions of quarks and observe the and mesons.
The wave function of the meson ground state is the Airy function. Using the
virial theorem we estimate the mean charge radii of mesons in terms of the
string tension and the Airy function zero. On the basis of the perturbative
theory, in the small external magnetic field we find the diamagnetic
polarizabilities of and mesons: , Comment: 22 pages, no figures, in LaTeX 2.09, typos correcte
Search for nu(mu)-->nu(e) Oscillations in the NOMAD Experiment
We present the results of a search for nu(mu)-->nu(e) oscillations in the
NOMAD experiment at CERN. The experiment looked for the appearance of nu(e) in
a predominantly nu(mu) wide-band neutrino beam at the CERN SPS. No evidence for
oscillations was found. The 90% confidence limits obtained are delta m^2 < 0.4
eV^2 for maximal mixing and sin^2(2theta) < 1.4x10^{-3} for large delta m^2.
This result excludes the LSND allowed region of oscillation parameters with
delta m^2 > 10 eV^2.Comment: 19 pages, 8 figures. Submitted to Phys. Lett.
Final NOMAD results on nu_mu->nu_tau and nu_e->nu_tau oscillations including a new search for nu_tau appearance using hadronic tau decays
Results from the nu_tau appearance search in a neutrino beam using the full
NOMAD data sample are reported. A new analysis unifies all the hadronic tau
decays, significantly improving the overall sensitivity of the experiment to
oscillations. The "blind analysis" of all topologies yields no evidence for an
oscillation signal. In the two-family oscillation scenario, this sets a 90%
C.L. allowed region in the sin^2(2theta)-Delta m^2 plane which includes
sin^2(2theta)<3.3 x 10^{-4} at large Delta m^2 and Delta m^2 < 0.7 eV^2/c^4 at
sin^2(2theta)=1. The corresponding contour in the nu_e->nu_tau oscillation
hypothesis results in sin^2(2theta)<1.5 x 10^{-2} at large Delta m^2 and Delta
m^2 < 5.9 eV^2/c^4 at sin^2(2theta)=1. We also derive limits on effective
couplings of the tau lepton to nu_mu or nu_e.Comment: 46 pages, 16 figures, Latex, to appear on Nucl. Phys.
A study of backward going and in interactions with the NOMAD detector
Backward proton and production has been studied in
interactions with carbon nuclei. Detailed analyses of the momentum
distributions, of the production rates, and of the general features of events
with a backward going particle, have been carried out in order to understand
the mechanism producing these particles. The backward proton data have been
compared with the predictions of the reinteraction and the short range
correlation models.Comment: 29 pages, 14 figures, submitted to Nucl. Phys.
Study of the first paramagnetic to ferromagnetic transition in as prepared samples of Mn–Fe–P–Si magnetocaloric compounds prepared by different synthesis routes
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