Study of Nd-Fe-B Alloys with Nonstoichiometric Nd Content in Optimal Magnetic State

Characterization of two rapid-quenched Nd-Fe-B alloys with nonstoichiometric Nd content in the optimized magnetic state was carried out using the X-ray diffractometry (XRD), (57)Fe Mossbauer spectroscopic phase analysis (MS), electron microscopy (TEM), high resolution TEM (HREM) and Superconducting Quantum Interference Device (SQUID) magnetometer. The experimental results demonstrate the fundamental difference in the structure and magnetic properties of the two investigated alloys in the optimized magnetic state. The Nd-Fe-B alloy with the reduced Nd content (Nd(4.5)Fe(77)B(18.5)) was found to have the nanocomposite structure of Fe(3)B/Nd(2)Fe(14)B and partly alpha-Fe/Nd(2)Fe(14)B, with mean grain size below 30 nm. On the other side, the overstoichiometric Nd(14)Fe(79)B(7) alloy has almost a monophase structure with the dominant content of the hard magnetic phase Nd(2)Fe(14)B (up to 95 wt. %) and a mean crystallite size about 60 nm, as determined by XRD and TEM analysis. The results of magnetic measurements on SQUID magnetometer also suggest the nanocomposite structure of the Nd-low alloy and nanocrystalline decoupled structure of the Nd-rich alloy after the optimal heat treatment.open

Distributed intelligent illumination control in the context of probabilistic graphical models

Lighting systems based on light-emitting diodes (LEDs) possess many benefits over their incandescent counterparts including longer lifespans, lower energy costs, better quality of light and no toxic elements, all without sacrificing consumer satisfaction. Their lifespan is not affected by switching frequency allowing for better illumination control and system efficiency. In this paper, we present a fully distributed energy-saving illumination dimming control strategy for the system of a lighting network which consists of a group of LEDs and user-Associated devices. In order to solve the optimization problem, we are using a distributed approach that utilizes factor graphs and the belief propagation algorithm. Using probabilistic graphical models to represent and solve the system model provides for a natural description of the problem structure, where user devices and LED controllers exchange data via line-of-sight communication

Polymer-Bonded Magnetic Materials with Various Nd-Fe-B Filler Content

One of the more important developments in magnetic materials, polymer bonded magnets, have opened a new world of application opportunities. The Nd-Fe-B/polymer composite materials offer an excellent combination of strong magnetic and dynamical-mechanical properties. However, the transition temperatures of filler and matrix should be selected carefully considering the future application. Uniform particle distribution and good adhesion between Nd-Fe-B powder particles and polymer are essential for the quality of the composite, while stiffness of polymer matrix is one of the influencing factors as well. The damping properties of Nd-Fe-B/polymer composites with 15 wt.%, 50 wt.% and 75 wt.% of Nd-Fe-B powder were studied by dynamic mechanical analysis and compared with a pure polymer sample. Thermal stability was analyzed using a simultaneous differential scanning calorimetric and thermogravimetric analysis technique.11th Annual Conference of the Materials-Research-Society-of-Serbia (YUCOMAT 2009), Aug 31-Sep 04, 2009, Herceg Novi, Montenegr

The Northern segment of the External Dinarides (Croatia) in relation to stable Adria: paleomagnetic constraints

In recent years, the (mid) late Jurassic\u2013Eocene segment of the APW path for stable Adria became well constrained by paleomagnetic results obtained directly from the northern part of stable Adria (foreland of the Southern Alps and autochthonous Istria). Thus, a well-defined reference system is now available which facilitates the quantitative description of the displacements having taken place in the External Dinarides with respect to stable Adria through coeval paleomagnetic results from the External Dinarides. Such comparison does not reveal any difference between stable Adria and the Northern Adriatic islands, which belong to the external zone of the External Dinarides. In contrast, the internal belt represented by Gorski Kotar and the Velebit Mts. exhibits an about 30 CW rotation with respect to Adria. So far, direct comparison between the external and internal belts of the External Dinarides is not possible, since the paleomagnetic results from the two belts are not coeval. Thus, the significant difference in the rotation of the two belts may be interpreted as due to the existence of two carbonate platforms, an Adriatic and a Dinaric which moved independently before the Paleogene or could have taken place when the NE belt of the External Dinarides were trusted over Adria

Microstructure refinement and physical properties of Ag-SnO2 based contact materials prepared by high-energy ball milling

High energy ball milling was used in order to improve dispersion of metal oxide in Ag-SnO2 electrical contact materials. The processed Ag-SnO2 (92:8) and Ag-SnO2In2O3 (87.8:9.30:2.9) powder mixtures were subsequently consolidated to bulk solid pieces by conventional powder metallurgy method. The characterization of the prepared samples included microstructural analysis by XRD and SEM, as well as measurements of physical properties such as density, hardness and electrical conductivity. The results of X-Ray analysis point to reduction of crystallite size after milling of about ten times. Microstructures of sintered Ag-SnO2 and Ag-SnO2 In2O3 materials display very fine dispersion of the oxide components in silver matrix. Somewhat higher uniformity was obtained for Ag-SnO2 In2O3 material which was illustrated by results of SEM analysis and more consistent microhardness values. The obtained values of studied physical properties were found to be in accordance with observed higher dispersion of metal oxide particles and comparable to properties of commercial electrical contact materials of this type.Metoda visokoenergetskog mehaničkog mlevenja je primenjena za pripremu elektrokontaktnih materijala na bazi Ag-SnO2 sa ciljem postizanja visokog stepena disperzije čestica metalnih oksida u srebrnoj matrici. Smeše prahova sastava Ag- SnO2 (92:8) i Ag-SnO2In2O3 (87.8:9.30:2.9) su posle mlevenja procesuirane konvencionalnim tehnikama metalurgije praha. Karakterizacija sinterovanih uzoraka obuhvatila je mikrostrukturnu analizu (XRD, SEM) kao i merenje važnijih fizičkih svojstava: gustina, tvrdoća i električna provodljivost. Rezultati XRD analize su pokazali značajno smanjenje veličine kristalita od oko deset puta. Mikrostrukturna analiza sinterovanih materijala ukazala je na veoma finu i uniformnu disperziju oksidnih komponenti u srebrnoj matrici. SEM mikrofotografije takođe pokazuju veću uniformnost mikrostrukture uzorka Ag-SnO2In2O3 što potvrđuju i ujednačenije vrednosti mikrotvrdoće dobijene za ovaj materijal. Izmerene vrednosti analiziranih fizičkih svojstava su u saglasnosti sa postignutim većim stepenom disperzije čestica metalnih oksida u srebrnoj matrici i uporedive su sa svojstvima komercijalnih elektrokontaktnih materijala ovog tipa

The Colli Berici

The paper delas with the stratigraphical setting of the Colli Berici. After the geological and stratigraphical setting of the area, a detailed biostratigraphical setting of the Eocene successions is presented. The stops of the filed trips organised within the last meeting of the IGCP393 are also described and illustrated

New Cretaceous paleomagnetic results from the foreland of the Southern Alps and the refined apparent polar wander path for stable Adria

The central-western and the eastern Southern Alps are separated by the triangular shaped Adige embayment, which belongs to stable Adria and was the site of pelagic sedimentation from the Tithonian through Maastrichtian. The first part of this study presents paleomagnetic results from the Tithonian\u2013 Cenomanian Biancone and Turonian\u2013Maastrichtian Scaglia Rossa formations sampled at 33 geographically distributed and biostratigraphically dated localities. The new and high quality paleomagnetic results from the Adige embayment are then combined with coeval paleomagnetic directions from autochthonous Istria (M\ue1rton et al., 2008), which also belongs to stable Adria. The combined data set (which for the Late Albian\u2013Maastrichtian time period is constructed similarly to the synthetic African curve by Besse and Courtillot, 2002, 2003) reveals an important tectonic event (Late Aptian\u2013Early Albian) characterized by 20\ub0 CCW rotation and sedimentary hiatus. Comparison between paleomagnetic declinations/inclinations expected in an African framework (i.e. with the assumption that Adria is still an African promontory) leads to the following conclusions. The timedistributed Tithonian and Berriasian (150\u2013135 Ma) paleomagnetic directions exhibit the \u201cAfrican hairpin\u201d with an inclination minimum and a sudden change from CW to CCW rotation at 145 Ma. Concerning the younger ages, the declinations for Adria continue to follow the African trend of CCW rotation till the end of Cretaceous. However, the Tithonian\u2013Maastrichtian declination curve for stable Adria is displaced by 10\ub0 from the \u201cAfrican\u201d curve as a result of two rotations. The first, an about 20\ub0 CW rotation of Adria with respect to Africa took place between the Maastrichtian and the mid-Eocene. During this time the orientation of Adria remained the same, while Africa continued its CCW rotation. The younger rotation (30\ub0CCW) changed the orientation of Adria relative to Africa as well as to the present North