114 research outputs found
Evolution and stability of a magnetic vortex in small cylindrical ferromagnetic particle under applied field
The energy of a displaced magnetic vortex in a cylindrical particle made of
isotropic ferromagnetic material (magnetic dot) is calculated taking into
account the magnetic dipolar and the exchange interactions. Under the
simplifying assumption of small dot thickness the closed-form expressions for
the dot energy is written in a non-perturbative way as a function of the
coordinate of the vortex center. Then, the process of losing the stability of
the vortex under the influence of the externally applied magnetic field is
considered. The field destabilizing the vortex as well as the field when the
vortex energy is equal to the energy of a uniformly magnetized state are
calculated and presented as a function of dot geometry. The results (containing
no adjustable parameters) are compared to the recent experiment and are in good
agreement.Comment: 4 pages, 2 figures, RevTe
The Tunka Experiment: Towards a 1-km^2 Cherenkov EAS Array in the Tunka Valley
The project of an EAS Cherenkov array in the Tunka valley/Siberia with an
area of about 1 km^2 is presented. The new array will have a ten times bigger
area than the existing Tunka-25 array and will permit a detailed study of the
cosmic ray energy spectrum and the mass composition in the energy range from
10^15 to 10^18 eV.Comment: 3 pages, 2 figures, to be published in IJMP
BAIKAL experiment: status report
We review the present status of the Baikal Neutrino Project and present the
results obtained with the deep underwater neutrino telescope NT-200.Comment: 4 pages, 3 figures. Presented at TAUP 2001 (7th international
workshop on Topics in Astroparticle and Underground Physics), Sep. 2001,
Laboratori Nazionali del Gran Sasso, Assergi, Ital
The Lake Baikal neutrino experiment: selected results
We review the present status of the lake Baikal Neutrino Experiment and
present selected physical results gained with the consequetive stages of the
stepwise increasing detector: from NT-36 to NT-96. Results cover atmospheric
muons, neutrino events, very high energy neutrinos, search for neutrino events
from WIMP annihilation, search for magnetic monopoles and environmental
studies. We also describe an air Cherenkov array developed for the study of
angular resolution of NT-200.Comment: 25 pages, 12 figures. To appear in the Procrrdings of International
Conference on Non-Accelerator New Physics, June 28 - July 3, 1999, Dubna,
Russi
Transportation and focusing of accelerated proton beams by means of dielectric channels
Prediction of inter-particle adhesion force from surface energy and surface roughness
Fine powder flow is a topic of great interest to industry, in particular for the pharmaceutical industry; a major concern being their poor flow behavior due to high cohesion. In this study, cohesion reduction, produced via surface modification, at the particle scale as well as bulk scale is addressed. The adhesion force model of Derjaguin-Muller-Toporov (DMT) was utilized to quantify the inter-particle adhesion force of both pure and surface modified fine aluminum powders (∼8 μm in size). Inverse Gas Chromatography was utilized for the determination of surface energy of the samples, and Atomic Force Microscopy was utilized to evaluate surface roughness of the powders. Surface modification of the original aluminum powders was done for the purpose of reduction in cohesiveness and improvement in flowability, employing either silane surface treatment or dry mechanical coating of nano-particles on the surface of original powders. For selected samples, the AFM was utilized for direct evaluation of the particle pull-off force. The results indicated that surface modification reduced the surface energy and altered the surface nano-roughness, resulting in drastic reduction of the inter-particle adhesion force. The particle bond number values were computed based on either the inter-particle adhesion force from the DMT model or the inter-particle pull-off force obtained from direct AFM measurements. Surface modification resulted in two to three fold reductions in the Bond number. In order to examine the influence of the particle scale property such as the Bond number on the bulk-scale flow characterization, Angle of Repose measurements were done and showed good qualitative agreements with the Bond number and acid/base surface characteristics of the powders. The results indicate a promising method that may be used to predict flow behavior of original (cohesive) and surface modified (previously cohesive) powders utilizing very small samples
Simultaneous measurements of water optical properties by AC9 transmissometer and ASP-15 Inherent Optical Properties meter in Lake Baikal
Measurements of optical properties in media enclosing Cherenkov neutrino
telescopes are important not only at the moment of the selection of an adequate
site, but also for the continuous characterization of the medium as a function
of time. Over the two last decades, the Baikal collaboration has been measuring
the optical properties of the deep water in Lake Baikal (Siberia) where, since
April 1998, the neutrino telescope NT-200 is in operation. Measurements have
been made with custom devices. The NEMO Collaboration, aiming at the
construction of a km3 Cherenkov neutrino detector in the Mediterranean Sea, has
developed an experimental setup for the measurement of oceanographic and
optical properties of deep sea water. This setup is based on a commercial
transmissometer. During a joint campaign of the two collaborations in March and
April 2001, light absorption, scattering and attenuation in water have been
measured. The results are compatible with previous ones reported by the Baikal
Collaboration and show convincing agreement between the two experimental
techniques.Comment: 16 pages, submitted to NIM-
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