National Centre of Scientific Research "Demokritos"

About: National Centre of Scientific Research "Demokritos" is a facility organization based out in Athens, Greece. It is known for research contribution in the topics: Computer science & Aerosol. The organization has 471 authors who have published 640 publications receiving 14478 citations. The organization is also known as: Demokritos.

Magnetic Properties and Electronic Structure of the S = 2 Complex [MnIII{(OPPh2)2N}3] Showing Field-Induced Slow Magnetization Relaxation.

Abstract: The high-spin S = 2 Mn(III) complex [Mn{(OPPh2)2N}3] (1Mn) exhibits field-induced slow relaxation of magnetization (Inorg. Chem.2013, 52, 12869). Magnetic susceptibility and dual-mode X-band electron paramagnetic resonance (EPR) studies revealed a negative value of the zero-field-splitting (zfs) parameter D. In order to explore the magnetic and electronic properties of 1Mn in detail, a combination of experimental and computational studies is presented herein. Alternating-current magnetometry on magnetically diluted samples (1Mn/1Ga) of 1Mn in the diamagnetic gallium analogue, [Ga{(OPPh2)2N}3], indicates that the slow relaxation behavior of 1Mn is due to the intrinsic properties of the individual molecules of 1Mn. Investigation of the single-crystal magnetization of both 1Mn and 1Mn/1Ga by a micro-SQUID device reveals hysteresis loops below 1 K. Closed hysteresis loops at a zero direct-current magnetic field are observed and attributed to fast quantum tunneling of magnetization. High-frequency and -field EPR (HFEPR) spectroscopic studies reveal that, apart from the second-order zfs terms (D and E), fourth-order terms (B4m) are required in order to appropriately describe the magnetic properties of 1Mn. These studies provide accurate spin-Hamiltonian (sH) parameters of 1Mn, i.e., zfs parameters |D| = 3.917(5) cm-1, |E| = 0.018(4) cm-1, B04 = B42 = 0, and B44 = (3.6 ± 1.7) × 10-3 cm-1 and g = [1.994(5), 1.996(4), 1.985(4)], and confirm the negative sign of D. Parallel-mode X-band EPR studies on 1Mn/1Ga and CH2Cl2 solutions of 1Mn probe the electronic-nuclear hyperfine interactions in the solid state and solution. The electronic structure of 1Mn is investigated by quantum-chemical calculations by employing recently developed computational protocols that are grounded on ab initio wave function theory. From computational analysis, the contributions of spin-spin and spin-orbit coupling to the magnitude of D are obtained. The calculations provide also computed values of the fourth-order zfs terms B4m, as well as those of the g and hyperfine interaction tensor components. In all cases, a very good agreement between the computed and experimentally determined sH parameters is observed. The magnetization relaxation properties of 1Mn are rationalized on the basis of the composition of the ground-state wave functions in the absence or presence of an external magnetic field.

Mutual coupling control in a multiple antenna system using ferrimagnetic substrate

Abstract: In this paper, we present the design of a printed multiple antenna system that uses a ferrimagnetic compound (YIG) as part of the substrate. We investigate the influence of this material on the mutual coupling between the antenna elements when an external magnetic field is applied. It is proved that the proper application of the magnetic field changes the polarization of the elements from linear to circular and additionally reduces their mutual coupling.

Scene categorization using low-level visual features

Abstract: In this paper, we have built two binary classifiers for indoor/outdoor and city/landscape categories, respectively. The proposed classifiers consist of robust visual feature extraction that feeds a support vector classification. In the case of indoor/outdoor classification, we combine color and texture information using the first three moments of RGB color space components and the low order statistics of the energy wavelet coefficients from a two-level wavelet pyramid. In the case of city/landscape classification, we combine the first three moments of L*a*b color space components and structural information (line segment orientation). Experimental results show that a high classification accuracy is achieved.

Software Life-Cycle for an Adaptive Geographical Information System.

Abstract: This paper presents the software life-cycle for the development of a knowledge-based GIS. The life-cycle framework used is called MBIUI and provides the experimental studies that are required for designing, implementing and testing a decision making theory in a graphical user interface. The decision making theory has been adapted in the user interface for is used for the evaluation of different environmental data in terms of some criteria that concern the user needs and skills and select the one that seems most suitable for a user.

A small angle neutron scattering study of the spin-glass Fe90Nd3Zr7 amorphous alloy

Abstract: The spin-glass state of the amorphous alloy Fe90Nd3Zr7 has been studied by small angle neutron scattering. Irreversibility between zero-field cooling and warming up appears at around 200 K and below. During cooling down a sharp transition appears at 188 K, whereas on warming up the transition at the same temperature is smooth. From the analysis of the data is concluded that, below the transition temperature, the system breaks up into regions having a multitude of transition temperatures. The scattering is attributed to the interaction among the different regions as they attempt to undergo a ferromagnetic transition in competition with each other.