Search results

1

Complex Characteristics of Sintered Nd-Fe-B Magnets in Terms of Hydrogen Based Recycling

100%

Szymański M., Michalski B., Leonowicz M., Miazga Z.

|

2017

|

vol. 131

|

issue 5

1270-1273

EN

Sintered Nd-Fe-B magnets, dismantled by the P.P.H.U. Polblume company from scrap hard disc drives and medical device, were thermally demagnetized and analyzed in terms of their chemical composition, structure and magnetic properties. Magnets from hard disc drives drives had a magnetic structure of two opposite poles in a plane of a magnet and were covered with a nickel coating (around 50 μ m in thick), which however was often discontinuous and deeply scratched. The majority of the magnets were partially destroyed (broken or corroded). The magnet from hard disc drives were basically made of iron (65±1 wt%) and neodymium (30±2 wt%) however, they also included alloying elements such as Co (1-2.5 wt%), Dy (0-1 wt%) or Pr (0-5 wt%). The magnets from medical device consisted only of iron (65±1 wt%) and neodymium (34±1 wt%). Magnets of both kinds were textured thus their XRD patterns were amended. Diffraction patterns, typical for the Nd₂Fe₁₄B (φ) phase, were achieved after mechanical crushing of the bulk magnets. A regular X-ray diffraction pattern was achieved after mechanical crushing of the magnets. The microstructure of both types of the magnets, observed by scanning electron microscopy, consisted of grey grains of a Nd₂Fe₁₄B (φ) phase and a Nd-rich grain boundary phase. The magnets from hard disc drives exhibited excellent magnetic properties and anisotropy: maximum energy product above 300 kJ/m³, remanence around 1.4 T and coercivity around 1000 kA/m, slightly varying between each magnet. Magnetic properties of medical magnet were only a little worse: maximum energy product above 200 kJ/m³, remanence around 1.1 T and coercivity around 900 kA/m. Hydrogen disproportionation phase diagrams (temperature vs. pressure) were constructed for both kinds of the magnets, revealing possible conditions for the hydrogenation, disproportionation, desorption and recombination reaction.

2

Structure and Properties of Nd-Fe-B Alloy Subjected to HDDR Process

100%

Szymański M., Michalski B., Leonowicz M., Miazga Z.

Archives of Metallurgy and Materials

|

2016

|

issue 1

3

Effects of Solute-Solvent Interactions on Radiationless Decay of Thioketones Excited to Their S_{2}- and T_{1}-States

76%

Szymański M., Balicki M., Binkowski M., Kubicki J., Maciejewski A., Pawłowska E., Wróżowa T.

Acta Physica Polonica A

|

1996

|

vol. 89

|

issue 4

527-546

EN

Spectral and photophysical properties of a few aromatic thioketones in their S_{2}- and T_{1}-states, in particular those determined by their interactions with solvents, are discussed. The reasons for a drastically different behaviour of thioketones in interactions with benzene as well as saturated hydrocarbons and perfluoroalkanes are analysed in more detail. Results of the time-resolved transient absorption measurements in the pico- and nanosecond time scale are given. An analysis of these results proves that a product of the decay of the S_{2}-state of xanthione in benzene is a new transient (τ_{1/e} ≥ 60 ps) individuum which, regarding the system properties and the conditions of the experiment, has been identified as an exciplex in S_{2}-state formed as a result of an efficient interaction with benzene molecule. Also in xanthione//alkane systems the involvement of a transient individuum was proved. Most probably, this individuum was a thioketyl radical which could be formed by hydrogen abstraction from a hydrocarbon molecule by xanthione in the S_{2}-state. Such individua act as intermediates in passing excitation to the triplet states of thioketones and are effective channels of the S_{2}-state decay. The changes observed in the transient absorption spectra of xanthione in C_{6}H_{6} in the time range of 10^{-7}-10^{-6} s can be attributed to the formation of an excimer in the T_{1}-state as a result of the T_{1}-state selfquenching.

4

Structure and Transport Properties of La_{0.75-x}RE_xCa_{0.25}MnO_3 (RE = Gd, Dy, Ho; 0≤ x≤0.75) Manganites

76%

Drozd V., Pękała M., Kovac J., Skorvanek I., Szymański M., Nedilko S.

Acta Physica Polonica A

|

2004

|

vol. 106

|

issue 5

751-758

EN

Structure and transport properties have been studied for a series of La_{0.75-x}RE_xCa_{0.25}MnO_3 manganites with heavy rare earth ions of Gd, Dy, Ho substituting La with x=0, 0.10, 0.25, 0.50, and 0.75. Polycrystalline samples were prepared by the carbonate precipitation route. The oxygen content was determined by the iodometric titration. The X-ray investigations carried out by the powder method show that the unit cell volume gradually decreases and orthorhombic distortion of the lattice increases with rising RE content. Below the room temperature the electrical resistivity is of the semiconducting type for all the samples studied. Electrical resistivity vs. temperature dependences were analyzed within different models: simple thermal activation, Mott's variable range hopping, adiabatic, nonadiabatic, and bipolaron. The Curie temperatures of Gd, Dy, and Ho substituted manganites determined from magnetization measurements show that at 280 K all the samples are in the paramagnetic phase. The increasing RE fraction reduces magnetization at 4 K as compared to La_{0.75}Ca_{0.25}MnO_3.

5

Development of Large Vocabulary Continuous Speech Recognition for Polish

64%

Demenko G., Szymański M., Cecko R., Kuśmierek E., Lange M., Wegner K., Klessa K., Owsianny M.

Acta Physica Polonica A

|

2012

|

vol. 121

|

issue 1A

A-86-A-91

EN

In this study, the results of acoustic modeling used in a large vocabulary continuous speech recognition system are presented. The acoustic models have been developed with the use of a phonetically controlled large corpus of contemporary spoken Polish. Evaluation experiments showed that relatively good speech recognition results may be obtained with adequate training material, taking into account: (a) the presence of lexical stress; (b) speech styles (a variety of segmental and prosodic structures, various degrees of spontaneity of speech (spontaneous vs. read speech), pronunciation variants and dialects); (c) the influence of the sound level and background noises. The present large vocabulary continuous speech recognition evaluation results were obtained with Sclite assessment software. Moreover, the article delivers information about the speech corpus structure and contents and also a brief outline of the design and architecture of the automatic speech recognition system.

6

Magnetic Order and Magnetic Inhomogeneities in SnCrTe-PbCrTe Solid Solutions

52%

Kilanski L., Szymański M., Brodowska B., Górska M., Szymczak R., Podgórni A., Avdonin A., Reszka A., Kowalski B., Domukhovski V., Arciszewska M., Dobrowolski W., Slynko V., Slynko E.

Acta Physica Polonica A

|

2014

|

vol. 126

|

issue 5

1203-1206

EN

We present the studies of structural, electrical and magnetic properties of bulk Sn_{1-x-y}Pb_xCr_yTe mixed crystals with chemical composition 0.18 ≤ x ≤ 0.35 and 0.007 ≤ y ≤ 0.071. The magnetometric studies indicate that for the high Cr-content, y=0.071, the alloy shows ferromagnetic alignment with the Curie temperature, T_{C}, around 265 K. The Cr_5Te_8 clusters are responsible for the ferromagnetic order. At low Cr content, y ≈ 0.01, a peak in the ac magnetic susceptibility identified as the cluster-glass-like transition is observed at a temperature about 130 K. The cluster-glass-like transition is likely due to the presence of Cr_2Te_3 clusters in the samples with y ≈ 0.01. The transport characterization of the samples indicated strong metallic p-type conductivity with relatively high carrier concentration, n > 10^{20} cm^{-3}, and carrier mobility, μ > 150 cm^2/(V s).

7

Optically Pumped Laser Action on Nitride Based Separate Confinement Heterostructures Grown along the (11¯20) Crystallographic Direction

52%

Teisseyre H., Szymański M., Khachapuridze A., Skierbiszewski C., Feduniewicz-Żmuda A., Siekacz M., Łucznik B., Kamler G., Kryśko M., Suski T., Perlin P., Grzegory I.

|

EN

The intention of this work is to discuss and report on our research on nonpolar laser structures grown on bulk GaN crystal substrates along the (11¯20) nonpolar direction. The main advantages of such nonpolar structures are related to the elimination of the built-in electric fields present in commonly used systems grown along the polar (0001) axis of nitride crystals. We demonstrated the optically pumped laser action on separate confinement heterostructures. Laser action is clearly shown by spontaneous emission saturation, abrupt line narrowing, and strong transversal electric polarization of output light. The lasing threshold was reached at an excitation power density of 260 kW/cm^2 for a 700μm long cavity (at room temperature).

Refine search results

Complex Characteristics of Sintered Nd-Fe-B Magnets in Terms of Hydrogen Based Recycling

Structure and Properties of Nd-Fe-B Alloy Subjected to HDDR Process

Effects of Solute-Solvent Interactions on Radiationless Decay of Thioketones Excited to Their S_{2}- and T_{1}-States

Structure and Transport Properties of La_{0.75-x}RE_xCa_{0.25}MnO_3 (RE = Gd, Dy, Ho; 0≤ x≤0.75) Manganites

Development of Large Vocabulary Continuous Speech Recognition for Polish

Magnetic Order and Magnetic Inhomogeneities in SnCrTe-PbCrTe Solid Solutions

Optically Pumped Laser Action on Nitride Based Separate Confinement Heterostructures Grown along the (11¯20) Crystallographic Direction