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 $2 \times 14.3$ 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 $8.0\times10^{-8}$ GeV$^{-1}$. 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