196 research outputs found
Crack growth through low-cycle fatigue loading of material ARMOX 500T
This paper presents microstructure analysis of the creation and growth of cracks in uniaxial load. Analyse were done for steel Armox 500T (armour sheet). Results show that cracks are present quit early in steel lifetime. First micro cracks occur before the 200th cycles, whereby crack growth is progressive during further loading. Also it can be seen that after a certain number of cycles there are more longer cracks then shorter ones
Raw milk evaluation according to protein and fat content and its contamination
Do sada se u Jugoslaviji kvaliteta mlijeka, kao osnova za utvrđivanje cijene mlijeku, vrednovala samo na temelju podatka o količini masti. Zbog toga se selekcijom u govedarstvu nastojalo povećati proizvodnju mlijeka i količinu masti, ali se istovremeno smanjila količina suhe tvari bez masti i bjelančevina u mlijeku. U namjeri da se poboljšaju fizičke i kemijske karakteristike mlijeka predlaže se da se cijena mlijeku utvrđuje na temelju količine bjelančevina i masti. Zbrajanjem prosjeka masti (3,6%) i bjelančevina (3,0%) mlijeka utvrđuju se vrijednosne jedinice na temelju kojih se izvode cijene jedinica masti i bjelančevina. U Tabeli 1. navode se podaci za izračunavanje osnovne cijene mlijeka. Ovisno o kontaminaciji cijena mlijeka se može umanjivati ili povećati. Broj bakterija i somatskih stanica, te prisustvo inhibitora (dezinficijensa, detergenta, antibiotika i drugog) određuje razinu kontaminacije. Osnovna cijena mlijeka može se umanjiti ili povećati za 5% na temelju prisustva svakog pojedinog kontaminenta, što znači da bi u skladu s razinom kontaminacije, cijena mlijeka mogla biti veća ili manja za 15%. U Tabeli 2. su grupirani i prikazani kontaminenti mlijeka.So far, the milk quality evaluation in Yugoslavia as a basis for payments comprised only fat content. Therefore, selection in cattle breeding aimed to increase milk production and milk fat content but, at the same time, depressed solids-non-fat and protein content in milk. In order to improve physical and chemical characteristics of milk, it is suggested to pay milk according to its protein and fat contents. Summarizing the average present fat (3.6%) and protein contents (3.0%) of milk, total valuable units were obtained, from which derived prices of fat and protein units. In table 1 data are given on calculation of basic milk price. Depending on contamination, milk price could be lower or higher. Bacteria and somatic cells counts and presence of inhibitors (sanitizers, detergent, antibiotics and so on) determine the level of contamination. Based on the amount of each individual contaminator, the basic price of milk can be increased or decreased by 5%, which means that, according to the level of contamination, the price of milk could be greater or lower up to 15%. Common contaminators of milk are grouped and presented in tab. 2
Magneto-resistance quantum oscillations in a magnetic two-dimensional electron gas
Magneto-transport measurements of Shubnikov-de Haas (SdH) oscillations have
been performed on two-dimensional electron gases (2DEGs) confined in CdTe and
CdMnTe quantum wells. The quantum oscillations in CdMnTe, where the 2DEG
interacts with magnetic Mn ions, can be described by incorporating the
electron-Mn exchange interaction into the traditional Lifshitz-Kosevich
formalism. The modified spin splitting leads to characteristic beating pattern
in the SdH oscillations, the study of which indicates the formation of Mn
clusters resulting in direct anti-ferromagnetic Mn-Mn interaction. The Landau
level broadening in this system shows a peculiar decrease with increasing
temperature, which could be related to statistical fluctuations of the Mn
concentration.Comment: 8 pages, 6 figure
Fractional Quantum Hall Effect in a Diluted Magnetic Semiconductor
We report the observation of the fractional quantum Hall effect in the lowest
Landau level of a two-dimensional electron system (2DES), residing in the
diluted magnetic semiconductor Cd(1-x)Mn(x)Te. The presence of magnetic
impurities results in a giant Zeeman splitting leading to an unusual ordering
of composite fermion Landau levels. In experiment, this results in an
unconventional opening and closing of fractional gaps around filling factor v =
3/2 as a function of an in-plane magnetic field, i.e. of the Zeeman energy. By
including the s-d exchange energy into the composite Landau level spectrum the
opening and closing of the gap at filling factor 5/3 can be modeled
quantitatively. The widely tunable spin-splitting in a diluted magnetic 2DES
provides a novel means to manipulate fractional states
Enhancement of the spin-gap in fully occupied two-dimensional Landau levels
Polarization-resolved magneto-luminescence, together with simultaneous
magneto-transport measurements, have been performed on a two-dimensional
electron gas (2DEG) confined in CdTe quantum well in order to determine the
spin-splitting of fully occupied electronic Landau levels, as a function of the
magnetic field (arbitrary Landau level filling factors) and temperature. The
spin splitting, extracted from the energy separation of the \sigma+ and \sigma-
transitions, is composed of the ordinary Zeeman term and a many-body
contribution which is shown to be driven by the spin-polarization of the 2DEG.
It is argued that both these contributions result in a simple, rigid shift of
Landau level ladders with opposite spins.Comment: 4 pages, 3 figure
Effect of pressure on the Raman modes of antimony
The effect of pressure on the zone-center optical phonon modes of antimony in
the A7 structure has been investigated by Raman spectroscopy. The A_g and E_g
frequencies exhibit a pronounced softening with increasing pressure, the effect
being related to a gradual suppression of the Peierls-like distortion of the A7
phase relative to a cubic primitive lattice. Also, both Raman modes broaden
significantly under pressure. Spectra taken at low temperature indicate that
the broadening is at least partly caused by phonon-phonon interactions. We also
report results of ab initio frozen-phonon calculations of the A_g and E_g mode
frequencies. Presence of strong anharmonicity is clearly apparent in calculated
total energy versus atom displacement relations. Pronounced nonlinearities in
the force versus displacement relations are observed. Structural instabilities
of the Sb-A7 phase are briefly addressed in the Appendix.Comment: 10 pages, 8 figure
Raman spectra of MgB2 at high pressure and topological electronic transition
Raman spectra of the MgB2 ceramic samples were measured as a function of
pressure up to 32 GPa at room temperature. The spectrum at normal conditions
contains a very broad peak at ~590 cm-1 related to the E2g phonon mode. The
frequency of this mode exhibits a strong linear dependence in the pressure
region from 5 to 18 GPa, whereas beyond this region the slope of the
pressure-induced frequency shift is reduced by about a factor of two. The
pressure dependence of the phonon mode up to ~ 5GPa exhibits a change in the
slope as well as a "hysteresis" effect in the frequency vs. pressure behavior.
These singularities in the E2g mode behavior under pressure support the
suggestion that MgB2 may undergo a pressure-induced topological electronic
transition.Comment: 2 figure
Calculations on the Size Effects of Raman Intensities of Silicon Quantum Dots
Raman intensities of Si quantum dots (QDs) with up to 11,489 atoms (about 7.6
nm in diameter) for different scattering configurations are calculated. First,
phonon modes in these QDs, including all vibration frequencies and vibration
amplitudes, are calculated directly from the lattice dynamic matrix by using a
microscopic valence force field model combined with the group theory. Then the
Raman intensities of these quantum dots are calculated by using a
bond-polarizability approximation. The size effects of the Raman intensity in
these QDs are discussed in detail based on these calculations. The calculations
are compared with the available experimental observation. We are expecting that
our calculations can further stimulate more experimental measurements.Comment: 21 pages, 7 figure
Search for weakly interacting sub-eV particles with the OSQAR laser-based experiment: results and perspectives
Recent theoretical and experimental studies highlight the possibility of new
fundamental particle physics beyond the Standard Model that can be probed by
sub-eV energy experiments. The OSQAR photon regeneration experiment looks for
"Light Shining through a Wall" (LSW) from the quantum oscillation of optical
photons into "Weakly Interacting Sub-eV Particles" (WISPs), like axion or
axion-like particles (ALPs), in a 9 T transverse magnetic field over the
unprecedented length of m. No excess of events has been
detected over the background. The di-photon couplings of possible new light
scalar and pseudo-scalar particles can be constrained in the massless limit to
be less than GeV. These results are very close to the
most stringent laboratory constraints obtained for the coupling of ALPs to two
photons. Plans for further improving the sensitivity of the OSQAR experiment
are presented.Comment: 7 pages, 7 figure
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