Search results for "Control and Systems Engineering"

Performance Study of Split Ferrite Cores Designed for EMI Suppression on Cables

2020

The ideal procedure to start designing an electronic device is to consider the electromagnetic compatibility (EMC) from the beginning. Even so, EMC problems can appear afterward, especially when the designed system is interconnected with external devices. Thereby, electromagnetic interferences (EMIs) could be transmitted to our device from power cables that interconnect it with an external power source or are connected to another system to establish wired communication. The application of an EMI suppressor such as a sleeve core that encircles the cables is a widely used technique to attenuate EM disturbances. This contribution is focused on the characterization of a variation of this cable …

Description of Relaxor State in Na1/2Bi1/2TiO3-SrTiO3-PbTiO3 System of Solid Solutions

2011

Vogel-Fulcher law, traditionally applied to describe dispersion of dielectric permittivity in relaxor ferroelectrics, requires introduction of two different relaxation mechanisms above and below freezing temperature correspondingly. Extending distribution function of relaxation times, previously known for low-temperature region, allows creating common description of relaxation in all range, where distribution function of relaxation times can be regarded as wide, without freezing at certain temperature.

ELECTRICAL PROPERTIES OF LEAD FERROTANTALATE CERAMICS

2009

ABSTRACT Perovskite structures with high dielectric constants and magnetic properties play an important role in micro- and optoelectronics and have numerous practical applications. Relaxor type ferroelectric ceramics PbFe1/2Ta1/2O3 with perovskite structure was subject of present studies. Pyrochlore free lead ferrotantalate ceramics were produced by solid state technology from oxides. Low- and infra-low frequency studies of dielectric properties of PbFe1/2Ta1/2O3 ceramics have revealed considerable infra-low frequency dispersion at temperatures above the temperature of maximum dielectric permittivity. The observed dispersion described by lemniscates is due to a considerable Maxwell-Wagner r…

Comparative Hybrid Hartree-Fock-DFT Calculations of ReO3, SrTiO3, BaTiO3, PbTiO3 and CaTiO3 (001) Surfaces

2021

DIRECT NUMERICAL SIMULATION OF MOTION OF FERROMAGNETIC PARTICLES IN MAGNETORHEOLOGICAL SUSPENSION

2008

ABSTRACT Results simulation of magnetorheological suspension at particle level are reported. The present approach accounts for a better description of hydrodynamic interaction between close spheres. Development of lamellar structures similar to those obtained by other researchers in Poiseuille flow is observed in shear flow. Studies of single layer lamellar structures reveal presence of short chains and more complex aggregates.

SYNTHESIS AND CHARACTERIZATION OF SB-SUBSTITUTED (K0.5Na0.5)NbO3 PIEZOELECTRIC CERAMICS

2008

ABSTRACT Lead-free piezoelectric ceramics (K0.5Na0.5)(Nb1-xSbx)O3+0.5 mol.%MnO2, where x = 0 ÷ 0.10, with single phase structure and rhombohedral symmetry at room temperature were prepared by conventional ceramic technology. The optimal sintering temperatures of compositions were within 1100°–1140°C. MnO2 functions as a sintering aid and effectively improves the densification. The samples reached density from 4.26 g/cm3 for undoped (K0.5Na0.5)NbO3 to 4.40 g/cm3 for Mn/Sb5+ co-doped ceramics. The co-effects of MnO2 doping and Sb5+ substitution lead to significant improvement in dielectric and piezoelectric properties: e at the Tc increased from 6000 (KNN) to 12400 (x = 0.04), d33 = 92 ÷ 192 …

SINTERING OF LEAD-FREE (K0.5Na0.5)NbO3 BASED SOLID SOLUTION

2009

ABSTRACT In this study lead-free solid solution (K0.5Na0.5)NbO3 was prepared, structure, dielectric parameters of ceramics were investigated. The doping of sintering aids did not affect the crystallographic structure of the ceramics significantly; all ceramic samples had a single-phase perovskite structure. Added elements CdO, ZnO, MnO2, V2O5 effectively decreased the sintering temperature of KNN by 50°–80°C. All sintering aids influenced sinterability, microstructure and dielectric properties of ceramics. Dielectric constant for doped samples increased from 6000 up to 8000; Pr = 15 μC/cm2, Ec = 9 kV/cm, d33 = 110 pC/N, kp = 0.38 and Qm = 190 for MnO2 doped samples.

Effect of Heat Exchange Transient Conditions with Moving Water-Air Interface on Space Charge Accumulation in Undersea HVdc Cables

2021

The accumulation of space charge inside the dielectric layer of an HVdc cable is one of the most important issue to be considered in the design stage and during the operating conditions. The separation of space charge is due to several factors including the dependence on temperature of the electrical conductivity of the insulation and the establishment of a thermal gradient under load conditions. This article is focused on the investigation of the effect of an axial heat transmission on the space charge and electric field distributions in an HVdc cable. In order to assess the impact of this phenomenon, a case study involving a cable immersed partly in water and partly in air has been simula…

Editorial for the Special Issue on Nanofabrication with Focused Electron/Ion Beam Induced Processing

2021

Focused electron beam (FEB) and focused ion beam (FIB) technologies have opened novel paths for material science research and technology at the micro and nano scales in recent decades [...]

Transient absorption and luminescence of LiNbO3 and KNbO3

2001

Abstract The results of time-resolved optical absorption spectra in congruent and stoichiometric LiNbO3 as well as KNbO3 crystals are reported. The role of different polaron types in transient absoiption and luminescence spectra and decay kinetics are discussed.