Superconductivity and electronic structure of the W7Re13B compound

The superconductor W7Re13B has been studied by the magnetic measurements and microwave absorption. The crystal structure of W7Re13B is cubic (¯-Mn type). This compound exhibits a sharp superconducting transition at a temperature of Tc = 7:2 K. The electronic structure of W7Re13B has been studied by X-ray photoelectron spectroscopy and the band structure has been calculated by the full-potential local-orbital minimum-basis method using the scalar-relativistic mode. The main contribution to the density of states at the Fermi level is from 5d electrons of W and Re. The W and Re bands are similar and substituting W by Re does not change the total density of states

Formation of MnBi by Mechanical Alloying

In this report we demonstrate that mechanical alloying is an alternative process to produce the intermetallic compound MnBi. Magnetically MnBi powder is prepared from the elemental powders by mechanical alloying in a planetary ball mill and then solid-state reaction at a relatively low temperature. The MnBi powder was aligned in a magnetic field and isostatic pressed. The X-ray pattern of powder reacted clearly shows the intensity peaks of the MnBi phase. After annealing the magnetization was about 1.0×10$\text{}^{-4}$T m$\text{}^{3}$/kg

Peltier module in systems of cooling the LEDs and LED matrices

Układy chłodzenia diod i matryc LED stanowią obszerną grupę urządzeń i rozwiązań, która stale się powiększa z uwagi na ciągły rozwój w dziedzinie elektroluminescencyjnych źródeł promieniowania. Wraz z polepszaniem parametrów diod i matryc LED rosną też wymagania odnośnie ich układów chłodzenia. W układach tych występują wszystkie znane systemy używane do schładzania urządzeń elektronicznych: od najprostszych pasywnych (radiatory) do skomplikowanych kombinacji w aktywnych układach chłodzenia (wentylatorowe, cieczowe) oraz specjalne układy chłodzenia wykorzystujące np. ogniwa Peltiera. W niniejszym artykule skupiono się właśnie na zastosowaniu ogniw Peltiera w układach chłodzenia diod i matryc LED. Przedstawiono budowę, zasadę działania, rodzaje i parametry tych ogniw. Omówiono wybrane systemy chłodzenia oparte na ogniwach Peltiera oraz przeanalizowano wady i zalety takiego rozwiązania.Cooling systems the LEDs and LED matrices constitute the extensive group of devices and solutions, which constantly is growing considering the constant development in the field of electroluminescent radiation sources. Along with improving parameters of LEDs and LED matrices also requirements grow in relation to their cooling systems. All known systems used for cooling electronic devices are appearing in these arrangements: from straightest passive (radiators) to complicated combinations in active cooling systems (fan, heat pump) and special cooling systems using Peltier module. The present article is just concentrated on using Peltier module in cooling systems of LEDs and LED matrices. A structure, principle of operation, types and parameters of these modules were described. Chosen cooling systems based on Peltier modules were discussed as well as an advantages and disadvantages of such a solution was analysed

Systems of cooling the LEDs and LED matrices

Niniejsza praca zawiera przegląd obecnie stosowanych układów chłodzenia diod i matryc LED. Zaprezentowano, zarówno najprostsze sposoby odprowadzania ciepła, z których korzysta się przy najprostszych diodach LED małej mocy, jak i bardziej skomplikowane systemy wykorzystywane do chłodzenia diod LED mocy i matryc LED. Przedstawiono wybrane rodzaje pasywnych oraz aktywnych układów chłodzenia oraz omówiono ich parametry i właściwości. Zwrócono również uwagę na wpływ wybranych czynników na pracę, zarówno diod i matryc LED, jak i samego systemu chłodzącego. Ponadto pokrótce omówiono programy komputerowe wykorzystywane do projektowania i obliczeń przy konstruowaniu układów chłodzenia.This work contains a review of currently applied systems of cooling the LEDs and LED matrices. The simplest as well as more sophisticated cooling systems are presented. Parameters and properties of the selected kinds of passive and active cooling systems are described. Influence of some factors on the operation of the LEDs and on their cooling system has been taken into consideration. Moreover, computer programs to be used for the design these systems are briefly presented

Martensitic Transformations and Magnetic Properties of Ni-Mn-Sn Heusler Alloy Films

We report on structural and magnetic properties of $Ni_{50}Mn_{50-x}Sn_x$ (x=12÷14) films and compare them with those of the bulk Ni-Mn-Sn alloys. Magnetic measurements reveal clear presence of martensitic transformation in bulk alloys but in the flash-evaporated Ni-Mn-Sn thin films martensitic transformation is usually less visible. The best film samples annealed for 1 h at about 900 K exhibit clear signs of martensitic transformation: i.e., a small defect in magnetization and a substantial increase in ferromagnetic resonance line width

Electronic Structure of UCo4\text{}_{4}B Compound

UCo$\text{}_{4}$B is a member of uranium intermetallic borides family which crystallizes in the hexagonal CeCo$\text{}_{4}$B structure. The experimental data suggest the occurrence of the spin-fluctuation behaviour of UCo$\text{}_{4}$B. In this paper we present the results of band structure calculations using the ab-initio tight binding linear muffin-tin orbital method. We found good agreement between the experimental X-ray photoemission spectroscopy valence band spectrum and the ab-initio results

Magnetic Properties in Mn Pure Powder

The structural and magnetic properties of deformed powder of Mn obtained by mechanical grinding have been investigated using X-ray diffraction and magnetic measurements. The small values of ferromagnetic moment of Mn after grinding are attributed to the formation of a deformed phase at the surface of grains with enlargement of the interatomic spacings at the grains boundaries