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[en] Microstructural features and magnetic behavior of epitaxially grown SmCo thin films with very high in-plane anisotropy are presented. Transmission electron microscopy was used to characterize the microstructure while magnetic measurements were performed using dc and SQUID magnetometers. Two substrate orientations were studied, i.e., MgO(100)/Cr(100)/SmCo(11 bar 20) and MgO(110)/Cr(211)/SmCo(1 bar 100). In the former, the SmCo(11 bar 20) film shows a bicrystalline microstructure, whereas in the latter, a uniaxial one is observed. Both microstructure consist of grains with a mixture of SmCo3 , Sm2Co7 and SmCo3 polytypoids. A deviation from the c-axes was observed in the in-plane anisotropy of the SmCo(11bar 20) thin film. A strong exchange interaction between the grains would, in principle, explain the observed deviation. On the other hand, both SmCo(11bar 20) and (1bar 100) thin films show very high coercivity values with pinning-type characteristics. Possible coercivity mechanisms related to intergranular exchange interactions and local variation in magnetocrystalline anisotropy constants are discussed
[en] Full text.The wavelet's transform has emerged as exciting new tool for statistical image processing. The wavelet domain provides a natural setting for many applications in medical imaging and tele medicine area. The interesting properties of wavelet transform have led to a powerful image processing technique based on a simple transformation of individual wavelet coefficient as thought it were dependent of all others. By exploiting the dependencies between wavelet coefficients, a new wavelet domain probability models have been developed based on the hidden Markov probability models. The Wavelet-domain hidden Markov (HMM) models have recently been introduced and successfully applied in image processing area and in particular the Hidden Markov tree (HMT) models. The HMT models can characterize the joint statistics of wavelet coefficients across scales. these models are tree-structured probabilistic graph that captures statistical properties of the coefficient of wavelet transform. Since the HMT is particularly well suited to image containing singularities like edge and ridge, it provides a good classifier for distinguishing between textures of image. Using the inherent tree structure of the wavelet HMT and it fast training and likelihood algorithms, the texture classification at range of different scales. We then fuse these multi scale classifications using Bayesian probabilistic graph to obtain reliable final segmentations. Finally, the compressed image can be segmented directly. In our work, we have applied these models for texture segmenting of compressed MRI images by using the HMT models. By concisely modeling and fusing the statistical behavior of textures at multiple scales, the algorithm developed on HTM models produces an accurate segmentation of texture images yielding a range of segmentation at different scales. One of the most important results is capability of segmenting compressed image without re-expanding, this create a framework for developing joint segmentation and compression of MRI image in tele medicine
[en] The use of AlN epitaxial films deposited on vicinal Si(111) as templates for the growth of GaN quantum dots is investigated by transmission electron microscopy and atomic force microscopy. It is found that the substrate vicinality induces both a slight tilt of the AlN (0001) direction with respect to the  direction and a step bunching mechanism. As a consequence, a dislocation dragging behavior is observed giving rise to dislocation-free areas well suited for the nucleation of GaN quantum dots
[en] The impact of the capping process on the structural and morphological properties of GaN quantum dots (QDs) grown on fully relaxed Al0.5Ga0.5N templates was studied by transmission electron microscopy. A morphological transition between the surface QDs, which have a pyramidal shape, and the buried ones, which have a truncated pyramid shape, is evidenced. This shape evolution is accompanied by a volume change: buried QDs are bigger than surface ones. Furthermore a phase separation into Al0.5Ga0.5N barriers was observed in the close vicinity of buried QDs. As a result, the buried QDs were found to be connected with the nearest neighbors by thin Ga-rich zones, whereas Al-rich zones are situated above the QDs
[en] We analyze an epitaxially grown heterostructure composed of InGaN nanodisks inserted in GaN nanowires in order to relate indium concentration to the electronic properties. This study was achieved with spatially resolved low-loss electron energy-loss spectroscopy using monochromated electrons to probe optical excitations—plasmons—at nanometer scale. Our findings show that each nanowire has its own indium fluctuation and therefore its own average composition. Due to this indium distribution, a scatter is obtained in plasmon energies, and therefore in the optical dielectric function, of the nanowire ensemble. We suppose that these inhomogeneous electronic properties significantly alter band-to-band transitions and consequently induce emission broadening. In addition, the observation of tailing indium composition into the GaN barrier suggests a graded well-barrier interface leading to further inhomogeneous broadening of the electro-optical properties. An improvement in the indium incorporation during growth is therefore needed to narrow the emission linewidth of the presently studied heterostructures
[en] Highlights: • New Hybrid system coupling photovoltaic and thermoelectric are studied. • Thermal transfer Method. • The effect of coupling types which are direct and indirect are examined. • The Heat Transfer is modeled in Hybrid system. • The indirect coupling significantly improves the overall efficiency. - Abstract: Advanced photovoltaic devices with a high performance/cost ratio is a major concern nowadays. In the present study, we investigate the energetic efficiency of a new concept based on an indirect (instead of direct) photovoltaic and thermoelectric coupling. Using state-of-the-art thermal transfer calculations, we have shown that such an indirect coupling is an interesting alternative to maximize solar energy exploitation. In our model, a concentrator is placed between photovoltaic and thermoelectric systems without any physical contact of the three components. Our major finding showed that the indirect coupling significantly improve the overall efficiency which is very promising for future photovoltaic developments.
[en] Highlights: • SnFe2O4 a new half-metal spinel oxides for spintronic application. • The most stable normal spinel structures are identified for SnFe2O4. • Spin-polarized calculations give a half-metallic character for SnFe2O4. - Abstract: In this work, a study of the electronic and magnetic properties of SnFe2O4 spinel ferrite for different case of octahedral and tetrahedral distribution was carried out by using the Full Potential Linearized Plane Wave (FP-LAPW) method in density functional theory (DFT) implemented in the WIEN2K package, with the generalized gradient (GGA) and Tran-Blaha modified Becke-Johnson approximations for the exchange and correlation functional. Our spin-polarized calculations based on mBJ correction show a half metallic behavior for SnFe2O4 which confirm the usefulness of SnFe2O4 in spintronic application. From the magnetic properties calculations, it is found that the magnetic moment per formula unit is 8.0327 µβ, 0.000015 µβ and 3.99µβ in SnFe2O4 100% normal, 100% inverse and 50% inverse, respectively.