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Bucharest, Romania

Stancu C.,Polytechnic University of Bucharest | Notingher P.V.,Polytechnic University of Bucharest | Panaitescu D.,ICECHIM | Marinescu V.,INCDIE ICPE CA
2014 International Conference on Optimization of Electrical and Electronic Equipment, OPTIM 2014 | Year: 2014

Polymer/metal composite materials have good rheological properties due to the polymer matrix and superior electrical or magnetic properties through the conductive or magnetic filler. For this reason, they can be used in a number of industrial applications as electromagnetic shields or permanent magnets. This paper deals with the results of an experimental study regarding the manufacturing and characterization of composite materials containing low density polyethylene (LDPE) as matrix and neodymium (Nd) as filler, obtained by melt processing. The structure of composites, the loss factor measured in harmonic fields at frequencies between 1 mHz and 1 MHz and temperature between 30 and 80°C and the relative and specific losses are presented and discussed in this paper. Both loss factor and specific losses vary with the frequency of the electric field, temperature and filler content. For certain values of the frequency, the loss factor and relative losses show maximum values which increase of the temperature and filler content. The specific losses decrease with temperature but increase with the filler content and frequency of the electric field. For frequency values close to 1 MHz the specific losses overlap the ones in copper conductors. © 2014 IEEE. Source

Zaharescu T.,INCDIE ICPE CA | Pielichowski K.,Cracow University of Technology
Journal of Thermal Analysis and Calorimetry | Year: 2015

The characterization of radiation stability of polyurethane nanocomposites by chemiluminescence and optical spectroscopies (FTIR and UV–VIS) is presented. Samples consisting of polyurethane and various percentages of polyhedral oligomeric silsesquioxane (POSS), namely 0, 2, 4, 6, 8 and 10 mass% loading, were aged by γ(137Cs)-irradiation. The polyurethane composites with 2 and 4 mass% POSS have presented slower rate of degradation in comparison with unmodified polymer. The consequences of the increase POSS loading are analyzed starting from the structural configuration of POSS which allows the scavenging of free radicals formed in polymer phase. The received moderate doses (10 and 20 kGy) like a sterilization procedure at a dose rate of 0.4 kGy h−1 brought significant changes in the thermal behavior of our hybrid composites, splitting the formulations into two groups: one group is characterized by the increasing thermal stability, while the second group presents an advancing oxidative degradation. © 2015 Akadémiai Kiadó, Budapest, Hungary Source

Dan D.,INCDIE ICPE CA | Dan D.,Polytechnic University of Bucharest
2015 9th International Symposium on Advanced Topics in Electrical Engineering, ATEE 2015 | Year: 2015

This paper presents the modeling and optimal design of a sextupole magnet prototype for the High-Energy Storage Ring (HESR) [1] of the Facility for Antiproton and Ion Research (FAIR) Project. Magnetic pole shape optimization by way of 2D magnetic modelling and mechanical optimization of magnetic yoke are also presented. Also, the paper analyses the Hall Probe (HP) [2] measurement procedure of the magnetic field in this sextupole magnet prototype for HESR. In these devices, it is of interest to determinate the magnetic field distribution, in the neighborhood of their axis. This distribution is not measured directly, but by using the measurements of magnetic flux density, in a finite number of points selected by users. © 2015 IEEE. Source

Stancu C.,INCDIE ICPE CA | Notingher P.V.,Polytechnic University of Bucharest | Badicu L.V.,Polytechnic University of Bucharest
Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP | Year: 2011

Dielectric response function f(t) of an insulation allows its behavior estimation in any electric field, constant or time variable. Generally, for the f(t) computation, a DC voltage U 0 is applied, for a long enough period of time, on the insulation and the resorption (depolarization) current i r (t) is measured. In the present paper, the dielectric response function is determined based on its Fourier transform, taking into account the frequency variation curve of real part of complex permittivity. Thus, the time variation curve of resorption currents and frequency variation curve of real part of complex permittivity have been determined and, based on them, the dielectric response function has been calculated for two different kinds of samples, mineral oil impregnated paper and water treed polyethylene. Finally, the time variation curves of f(t) obtained with both methods are analyzed. © 2011 IEEE. Source

Craciunescu O.,Romanian National Institute for Research and Development for Biological Sciences | Tardei C.,INCDIE ICPE CA | Moldovan L.,Romanian National Institute for Research and Development for Biological Sciences | Zarnescu O.,University of Bucharest
Central European Journal of Biology | Year: 2011

Of great interest in developing artificial bone is the incorporation of magnesium (Mg) ions into the ceramic lattice in order to improve the physico-chemical and structural properties of the material and to increase its morphological affinity towards newly formed osseous tissue. In the present study, we evaluated the morphological and biological properties of composite scaffolds fabricated by mixing a nanopowder of Mg-substituted beta-tricalcium phosphate with collagen type I in two dry weight ratios (variant I and II). We used biochemical methods, and electron and light microscopy to investigate their porosity, biodegradability and morphology. Osteoblast cell culture behavior in the presence of nanocomposite variants was also examined. Variant I scaffold presented a higher percentage of cross-links and a better resistance to collagenase degradation compared to variant II scaffold. Their porosity did not vary significantly. Osteoblasts cultivated in the presence of nanocomposite scaffolds for 72 h exhibited good cell viability and a normal morphology. When osteoblasts were injected into the scaffolds, a slightly higher proportion of adhered cells were observed for Mg-substituted samples after 7 days of cultivation. All these results showed that Mg-containing porous composite scaffolds had controlled degradation, allowed osteoblast proliferation and adhesion and are good candidates for bone repair. © 2011 Versita Warsaw and Springer-Verlag Wien. Source

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