2,326 research outputs found
Airy-function electron localization in the oxide superlattices
Oxide superlattices and microstructures hold the promise for creating a new
class of devices with unprecedented functionalities. Density-functional studies
of the recently fabricated superlattices of lattice-matched perovskite
titanates (SrTiO3)n/(LaTiO3)m reveal a classic wedge-shaped potential
originating from the Coulomb potential of a charged sheet of La atoms. The
potential in turn confines the electrons in the vicinity of the sheet, leading
to an Airy-function localization of the electron states. Magnetism is
suppressed for structures with a single LaTiO3 monolayer, while the bulk
antiferromagnetism is recovered in the structures with a thicker LaTiO3, with a
narrow transition region separating the magnetic LaTiO3 and the non-magnetic
SrTiO3
The Distribution of Minimum of Ratios of Two Random Variables and Its Application in Analysis of Multi-hop Systems
The distributions of random variables are of interest in many areas of science. In this paper, ascertaining on the importance of multi-hop transmission in contemporary wireless communications systems operating over fading channels in the presence of cochannel interference, the probability density functions (PDFs) of minimum of arbitrary number of ratios of Rayleigh, Rician, Nakagami-m, Weibull and α-µ random variables are derived. These expressions can be used to study the outage probability as an important multi-hop system performance measure. Various numerical results complement the proposed mathematical analysis
Ground state, electronic structure and magnetism of LaMnO3
We have calculated the discrete low-energy electronic structure in LaMnO3
originating from the atomic-like states of the strongly correlated 3d4
electronic system occurring in the Mn3+ ion. We take into account very strong
intra-atomic correlations, crystal field interactions and the intra-atomic
spin-orbit coupling. We calculated magnetic and paramagnetic state of LaMnO3
within the consistent description given by Quantum Atomistic Solid State Theory
(QUASST). Our studies indicate that the intra-atomic spin-orbit coupling and
the orbital magnetism are indispensable for the physically adequate description
of electronic and magnetic properties of LaMnO3.
Keywords: 3d oxides, crystal field, spin-orbit coupling, LaMnO3
PACS: 71.70Ej, 75.10DgComment: 5 pages, 2 figures, in RevTex
DEVELOPMENT OF SMES IN AGRIBUSINESS OF VOJVODINA COMMUNES - STATE AND PERSPECTIVES
Agriculture as the economic sector is an important factor of economic development of Serbia and an important part of economic structure. Serbia has agrarian resources (land, climate and water) that are not used enough, and therefore, represent a significant economic potential for further development. Vojvodina is the best-developed economic region of the Republic of Serbia, with dominant role of agricultural production. The main economic potential of Vojvodina development is, among other things, the strengthening and improvement of agriculture in the private sector. Economic potential of agriculture impose the need to analyze this situation in the field of small and medium sized entrepreneurship as the bearer of the future development of agriculture in Vojvodina. Cluster analysis is a method that will determine how to group communes in Vojvodina according to the level of development of small and medium-sized enterprises in the field of agriculture, and thus get an insight into the current state of development of this sector of agriculture, as well as point out the possibilities for the future development of SMEs in agribusiness of Vojvodina.Agricultural production, Small and medium sized enterprises (SMEs), Clusters analysis, Clustering of communes in Vojvodina, Agribusiness, Community/Rural/Urban Development, Public Economics,
Influence of Intra-cell Traffic on the Output Power of Base Station in GSM
In this paper we analyze the influence of intracell traffic in a GSM cell on the base station output power. It is proved that intracell traffic increases this power. If offered traffic is small, the increase of output power is equal to the part of intracell traffic. When the offered traffic and, as the result, call loss increase, the increase of output power becomes less. The results of calculation are verified by the computer simulation of traffic process in the GSM cell. The calculation and the simulation consider the uniform distribution of mobile users in the cell, but the conclusions are of a general nature
First evidence for charge ordering in NaVO from Raman spectroscopy
We argue on the basis of symmetry selection rules and Raman scattering
spectra that NaVO undergoes a charge ordering phase transition at
T=34 K. Such a transition is characterized by the redistribution of the
charges at the phase transition and corresponds to the change of the vanadium
ions, from uniform V to two different V and V states. In
the low temperature phase the V ions are forming a "zig-zag" ladder
structure along the {\bf b}-axis, consistent with the symmetry of the P2/b
space group.Comment: to be published in solid state communication
Electronic structure of the substitutional versus interstitial manganese in GaN
Density-functional studies of the electron states in the dilute magnetic
semiconductor GaN:Mn reveal major differences for the case of the Mn impurity
at the substitutional site Mn_Ga versus the interstitial site Mn_I. The
splitting of the two-fold and the three-fold degenerate Mn(d)states in the gap
are reversed between the two cases, which is understood in terms of the
symmetry-controlled hybridization with the neighboring atoms. In contrast to
Mn_Ga, which acts as a deep acceptor, Mn_I acts as a donor, suggesting the
formation of Coulomb-stabilized complexes such as (Mn_Ga Mn_I Mn_Ga), where the
acceptor level of Mn_Ga is passivated by the Mn_I donor. Formation of such
passivated clusters might be the reason for the observed low carrier-doping
efficiency of Mn in GaN. Even though the Mn states are located well inside the
gap,the wave functions are spread far away from the impurity center. This is
caused by the hybridization with the nitrogen atoms, which acquire small
magnetic moments aligned with the Mn moment. Implications of the differences in
the electronic structure for the optical properties are discussed
Management Measures in Brown Hare Population in Various Habitats in Serbia
Brown hare in Serbia lives in various habitats although the best brown hare habitats are lowland areas and river valleys. Brown hare has successfully adapted to agroecosystems in agricultural areas. In the last two decades in Serbia a number of studies was conducted associated with the analysis of themanagement measures in brown hare population, which recorded some cyclic oscillations in population abundance, density,age structure and exploitationrate. These measures are key elements in management of wildlife population so their implementation should be enforced. Problems related to brown hare population management in Serbia arise because there are neither proper guidelines to determine hare hunting productive areas nor how to define the solvency and capacities of hunting grounds that are not adapted to newly created habitat conditions in certain hunting grounds. Methodology of conducting and defining the number of hare population in various types of hunting grounds does not match given habitat conditions. Taking into account various habitat conditions in hunting grounds of Vojvodina and central Serbia it is very important to define in a correct manner population spring abundance, population density, age structure and exploitation rate for the purpose of sustainable management in hare population
Raman and infrared studies of La_1-ySr_yMn_1-xM_xO_3 (M=Cr, Co, Cu, Zn, Sc or Ga): Oxygen disorder and local vibrational modes
We present results of our study of polarized Raman scattering and infrared
reflectivity of rhombohedral ceramic La_1-ySr_yMn_1-xM_xO_3 manganites in the
temperature range between 77 and 320K. In our samples, a part of the Mn atoms
is substituted by M = Cr, Co, Cu, Zn, Sc, or Ga with x in the range 0 -- 0.1.
The hole concentration was kept at the optimal value of about 32% by tuning the
Sr content y. We have monitored the distortions of the oxygen sublattice by the
presence of broad bands in the Raman spectra, the increase of d.c. resistivity
extracted from the infrared reflectivity, and the change of the critical
temperature of the ferromagnetic transition. Our results support the idea, that
these properties are mainly determined by the radius of the substituent ion,
its electronic and magnetic structure playing only a minor role. Furthermore,
the Raman spectra exhibit an additional A_g-like high frequency mode attributed
to the local breathing vibration of oxygens surrounding the substituent ion.
Its frequency and intensity strongly depend on the type of the substituent. In
the Co-substituted sample, the mode anomalously softens when going from 300 to
77K. The frequency of the bulk A_{1g} mode depends linearly on the angle of the
rhombohedral distortion.Comment: 11 pages, 11 Figures, best-fit values table added, a discussion adde
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