Filters
total: 1184
filtered: 922
Search results for: COMPACT IMPEDANCE TRANSFORMERS
-
The behavioural model of graphene field-effect transistor
PublicationThe behavioural model of a graphene field-effect transistor (GFET) is proposed. In this approach the GFET element is treated as a “black box” with only external terminals available and without considering the physical phenomena directly. The presented circuit model was constructed to reflect steady-states characteristics taking also into account GFET capacitances. The authors’ model is defined by a relatively small number of equations...
-
Broadband Modeling of Motor Cable Impact on Common Mode Currents in VFD
PublicationExamination of conducted EMI generation and propagation in AC motor drives fed by frequency converter requires to consider parasitic capacitances in converters, motor windings and feeding cables to be taken into account. AC motor winding voltage transients and related common mode currents are significantly correlated with resonance effects occurring in converter's load circuits. Intensity levels of these phenomena depend...
-
Motor Cable Influence on the Conducted EMI Emission of the Converter Fed AC Motor Drive. - Vol. 1
PublicationInvestigation of conducted electromagnetic interference in AC motor drives fed by pulse width modulated voltage converters requires considering parasitic capacitances in converters, motor windings and feeding cables to be taken into account. Motor voltage transients and related conducted electromagnetic emission are significantly correlated with resonance effects occurring in load circuits. The levels of intensity of these phenomena...
-
Potentiometric Solid-Contact Multisensor System for Simultaneous Measurement of Several Ions
PublicationThe design and performance of potentiometric multisensor system made in solid-contact technology is described. Both, the measuring electrodes as well as the reference electrode are in a compact cell. The system allows for simultaneous measurement of various ions. The characteristics of the electrodes for Na+, K+ and Ca2+ ions were determined using the designed system and compared with ISEs of the same membrane composition in classical...
-
Macro-elements and Model Order Reduction for Efficient Three-Dimensional FEM Analysis
PublicationAn efficient model order reduction (MOR) methodology for three dimensional vector finite element method (FEM) is developed to accelerate simulations of the structures containing features that cause strong variations of mesh density. As the result of presented algorithm, FEM subsystems of equations corresponding to the selected refined region are converted into a very compact sets of linear equations, called macro-elements.Numerical...
-
Filtering EBG Structures Implemented in Coplanar Waveguide Feedline of Planar Slot Antenna
PublicationA novel compact dual-band slot antenna fed by a coplanar waveguide (CPW) incorporating electromagnetic band gap (EBG) structures has been proposed. At first, a classic wideband slot antenna fed by a CPW, dedicated to work in 2 ÷ 18 GHz band, has been designed. Subsequently, by adding simple EBG filtering structures into a CPW feedline, a dual-band performance ranging from 2.5 to 5.3 GHz and from 13.5 to 16.3 GHz, with the voltage...
-
Miniaturized dual‐band branch‐line coupler with enhanced bandwidth
PublicationIn this letter, a miniaturized hybrid dual-band branch-line coupler (BLC) with enhanced fractional bandwidths is proposed. Compact size and bandwidth enhancement are obtained using meandered transmission line sections with broken symmetry between cross-coupling branches. The circuit is designed at a low numerical cost using surrogate-assisted techniques. The optimized design features small size of only 0.25λg×0.19λg(28% miniaturization...
-
Influence of Dielectric Overlay Permittivity on Size and Performance of Miniaturized ESPAR Antenna
PublicationIn this paper, influence of dielectric overlay permittivity on miniaturized ESPAR antenna parameters is presented. ESPAR antenna is a low-cost and energy-efficient way to implement beam steering capability to a node and improve network performance. The antenna size reduction is obtained by embedding its active and passive elements in ABS based materials of relative permittivity equal to 4, 5.5 and 7.5 in order to achieve network...
-
Low-cost multi-objective optimization of antennas using Pareto front exploration and response features
PublicationIn the paper, a procedure for low-cost multi-objective optimization of antenna structures is presented. Our approach is based on exploration of the Pareto front representing the best possible trade-offs between conflicting objectives, here, the structure size and its electrical performance. Starting from the design representing the best in-band reflection level, subsequent Pareto-optimal designs are identified through local constrained...
-
Electrical conductivity and relaxation processes in V2O5 nanorods prepared by sol–gel method
PublicationProperties of high purity V2O5 nanorods prepared by a sol – gel method are presented. The studied materials were characterized by: X-ray diffractometry (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The electrical impedance was measured as a function of temperature and frequency. The obtained results show that the electrical conductivity increases with increasing temperature. The d.c. conductivity...
-
Exploring Mechanism of Corrosion Inhibition of WE43 and AZ31 Alloys by Aqueous Molybdate in Hank’s Solution by Multisine Impedimetric Monitoring
PublicationThe concept of utilizing multisine dynamic electrochemical impedance spectroscopy to monitor effectiveness of a model molybdate inhibitor for AZ31 and WE43 Mg alloys is proposed. The corrosion kinetics and instantaneous values of inhibition efficiency (IE) of molybdate at concentrations up to 150 mM were examined. The inhibitor provides inhibition in Hank’s solution at concentrations starting from ca. 25 mM, with the IE of about...
-
Improvement of electrochemical action of zinc-rich paints by addition of nanoparticulate zinc
PublicationThe influence of nanosized particles on electrochemical action of standard zinc-rich paints by means of SEM as well as potential and impedance measurements has been investigated. The motivation for doing this was to obtain additional electrical connection between the spherical microparticles themselves and zinc particles and steel substrate. Overall zinc content was at the level of 92% by weight. Samples with different concentration...
-
Hybrid Technique for the EM Scattering Analysis with the Use of Ring Domain Decomposition
PublicationA hybrid technique combining finite-element and mode-matching methods for the analysis of scattering problems in open space is presented here. The main idea is based on impedance matrix descriptions of the boundary surrounding the discrete computational domain and combine it with external field described analytically. The discrete analysis, which is the most time- and memory-consuming, is limited here only to the close proximity...
-
Insightful Analysis of Phenomena Arising at the Metal|Polymer Interphase of Au-Ti Based Non-Enzymatic Glucose Sensitive Electrodes Covered by Nafion
PublicationThis paper focuses on the examination of glucose oxidation processes at an electrode material composed of gold nanoparticles embedded in a titanium template. Three dierent conditions were investigated: the chloride content in the electrolyte, its ionic conductivity and the presence of a Nafion coating. The impact of the provided environment on the oxidation reaction was evaluated by cyclic voltammetry (CV) and electrochemical impedance...
-
Determination of Mathematical Model Parameters of a Medium Frequency Transformer
PublicationThe paper presents the results of experimental studies of the medium frequency transformer. The object of the research was a prototype of a single-phase transformer with a core made of ferrite I-core elements and windings made of Litz conductors. The research was carried out to determine the parameters of the transformer's mathematical model. The scope of the tests included determining the magnetic hysteresis loop and measuring...
-
Left-handed propagation characteristics of a dielectric and metal-loaded periodic circular waveguide
PublicationIn this paper, a periodic dielectric/metallic rod is located in a circular waveguide to obtain left-handed operation. Two geometries of the dielectric/metallic rod are proposed and examined. The dispersion characteristics of the investigated waveguides are obtained using a surface impedance model. Moreover, equivalent circuit models are proposed allowing for calculation of the dispersion characteristics and scattering parameters...
-
A novel sensor for measuring temperature profile during the thermoablation
PublicationAbstract — A novel approach for monitoring a temperature distribution inside a tissue during thermoablation is presented in the paper. A thermal profile is measured using a set of serially connected thermistors each bypassed by a capacitor. This technique allows a two-wire and simultaneous multi- point measurements using a multi-frequency measurement of electrical impedance. It is...
-
Nested Space Mapping Technique for Design and Optimization of Complex Microwave Structures with Enhanced Functionality
PublicationIn this work, we discuss a robust simulation-driven methodology for rapid and reliable design of complex microwave/RF circuits with enhanced functionality. Our approach exploits nested space mapping (NSM) technology, which is dedicated to expedite simulation-driven design optimization of computationally demanding microwave structures with complex topologies. The enhanced func-tionality of the developed circuits is achieved by means...
-
Dynamiczne wyznaczanie parametrów elektrycznego obwodu szeregowego
PublicationPo załączeniu napięcia na skutek istnienia inercji prąd w obwodzie zaczyna narastać od wartości zerowej do znamionowej. W tym czasie narastają spadki napięć na rezystancjach (impedancjach obwodu) do chwili spełnienia prawa Kirchhoffa. Można utworzyć układ ze sprzężeniem zwrotnym (układ regulacji stałowartościowej bądź nadążnej), który poszukuje parametrów obwodu spełniających prawa Kirchhoffa – elementy nie muszą być liniowe. W...
-
CHARAKTERYSTYKA WYMIANY CIEPŁA I OPORÓW PRZEPŁYWU OMYWANIA MIKROSTRUGAMI ROZWINIĘTEJ POWIERZCHNI
PublicationW artykule przedstawiono eksperymentalne badania kompaktowego wymiennika ciepła z intensyfikacją przejmowania ciepła przy użyciu mikrostrug. Niniejszy artykuł przedstawia projekt i testy prototypu, wymiennika ciepła typu mikrostrugowego. Modułowa konstrukcja wymiennika umożliwia zmianę wymiarów geometrycznych, a także zmianę materiału przegrody wymiennika ciepła. Metoda graficzna Wilsona została z zastosowana w celu określenia...
-
Numerical analysis of high temperature minichannels heat exchanger performance
PublicationNowadays, the most difficult technological challenge in energy sector is connected with the gas micro-CHP units, dedicated to the distributed power generation. They are expected to be of high efficiency and at the same time of compact in size. Regarding the first reason, significant increase in microturbine efficiency can only be achieved by increase in the engine operating temperature. Therefore, one of the critical elements in...
-
Globalized Knowledge-Based Simulation-Driven Antenna Miniaturization Using Domain-Confined Surrogates and Dimensionality Reduction
PublicationDesign of contemporary antenna systems encounters multifold challenges, one of which is a limited size. Compact antennas are indispensable for the new fields of application such as inter-net of things or 5G/6G mobile communication. Still, miniaturization generally undermines elec-trical and field performance. When attempted through numerical optimization, it turns into a constrained problem with costly constraints requiring electromagnetic...
-
Electronic conductivity in the SiO2-PbO-Fe2O3 glass containing magnetic nanostructures
PublicationThe linear impedance spectra of iron–silicate–lead glass samples were measured in the frequency range from 1 MHz to 1 MHz and in the temperature range from 153 K to 423 K. The structure was investigated by means of XRD and atomic force microscopy. Local electrical and magnetic properties of the samples were tested with the aid of electrostatic force microscopy (EFM) and magnetic force microscopy (MFM). The obtained results show...
-
Electrochemical and photoelectrochemical properties of the interface between titania nanotubes covered by conducting polymer in aqueous by conducting polymer in aqueous electrolytes – The effect of various geometry and electrolytes concentration
PublicationIn the present work we show the impact of nanotubes (NTs) geometry of titania utilized as a substrate in organic-inorganic systems acting as a p-n junction on efficient conversion of radiation energy into electrochemical energy. The electrolytic bath composition and electrolysis conditions were controlled in order to obtain TiO2NTs of various geometry as a result of electrochemical oxidation of titanium foil. The electrode material...
-
Development Of Dynamic Method For Evaluation Of Corrosion Rate On The Example Of Organic Corrosion İnhibitor
PublicationMeasurements of the corrosion rate belong to the most important aspects of materials science. In order to reduce material loss corrosion inhibitors are used. However selection of proper inhibitor should be based on evaluation of its mechanism and effective concentrations. Mechanism of inhibition usually has dynamic character so physicochemical parameters are changing in time. Most of actually used methods...
-
Fast EM-driven size reduction of antenna structures by means of adjoint sensitivities and trust regions
PublicationIn this letter, a simple yet robust and computationally efficient optimization technique for explicit size reduction of antenna structures is presented. Our approach directly handles the antenna size as the main design objective, while ensuring satisfactory electrical performance by means of suitably defined penalty functions. For the sake of accuracy, the antenna structure is evaluated using high-fidelity EM simulation. In order...
-
Benchmarking Deep Neural Network Training Using Multi- and Many-Core Processors
PublicationIn the paper we provide thorough benchmarking of deep neural network (DNN) training on modern multi- and many-core Intel processors in order to assess performance differences for various deep learning as well as parallel computing parameters. We present performance of DNN training for Alexnet, Googlenet, Googlenet_v2 as well as Resnet_50 for various engines used by the deep learning framework, for various batch sizes. Furthermore,...
-
Computations of the least number of periodic points of smooth boundary-preserving self-maps of simply-connected manifolds
PublicationLet $r$ be an odd natural number, $M$ a compact simply-connected smooth manifold, $\dim M\geq 4$, such that its boundary $\partial M$ is also simply-connected. We consider $f$, a $C^1$ self-maps of $M$, preserving $\partial M$. In [G. Graff and J. Jezierski, Geom. Dedicata 187 (2017), 241-258] the smooth Nielsen type periodic number $D_r(f;M,\partial M)$ was defined and proved to be equal to the minimal number of $r$-periodic points...
-
Phase Separation and Electrical Properties of Manganese Borosilicate Glasses
PublicationThe structure and electrical properties of manganese borosilicate glasses of a composition of xMnO-(0.8-x)SiO2-(0.2)B2O3 (x=0.4, 0.5 and 0.6 in mol) were investigated by impedance spectroscopy, SEM, XRD and confocal microscopy methods. The influence of composition on the glass structure and electrical properties was discussed. A separation of two amorphous phases was observed and it was concluded that one phase is SiO2-rich and...
-
A Goal-Oriented Error Estimator for Reduced Basis Method Modeling of Microwave Devices
PublicationThis letter proposes a novel a-posteriori error estimator suitable for the reduced order modeling of microwave circuits. Unlike the existing error estimators based on impedance function residuals, the new one exploits the residual error associated with the computation of the scattering matrix. The estimator can be effectively used in the Reduced Basis Method (RBM) to automatically generate reduced-order models. The results of numerical...
-
Hybrid piezoelectric motor based on electroactive lubrication principle
PublicationA novel conception of hybrid piezoelectric motor is presented in this paper. Proposed conception required synchronised work of quasi-static and resonant piezoelectric actuators that results in a rotary movement. The motor's working principle is explained and the main characteristics are described. Studied topology is compared to the existing piezoelectric motors with regards to its field of applications. The assembling process...
-
Analysis of Corrugated Coaxial Line with the Use of Body of Revolution and Finite Element Method
PublicationA combination of the body-of-revolution and finite element methods is utilized to the analysis of coaxial lines with corrugated rod and wall. Both periodic and non-periodic structures can be investigated. As the structure is axially symmetrical the two dimensional scalar-vector finite element method can be used, which allows for the investigation of complex geometries and is computationally efficient. A generalized impedance matrix...
-
Heterogeneous distribution of surface electrochemical activity in polycrystalline highly boron-doped diamond electrodes under deep anodic polarization
PublicationThe surface homogeneity of boron-doped diamond electrodes is variable and depends on anodic polarization conditions. The differentiation factor is the gradual and localized change in surface termination. A series of measurements under different polarization conditions was performed in order to investigate the scale of this effect. Nanoscale impedance microscopy (NIM) revealed large variation of surface resistance in individual...
-
Assessment of copper surface coverage with corrosion inhibitor using AFM-based local electrical measurements
PublicationThe paper presents a new method of assessment of metal surface coverage with corrosion inhibitor and thus of inhibitor protective performance. It is based on the atomic force microscopy measurement performed in a contact mode. Apart from topography images the proposed approach allows acquisition of local DC maps and local electrical impedance spectra via application of DC bias voltage or AC perturbation signal between the conductive...
-
Conductivity and viscosity changes of imidazolium ionic liquids induced by H2O and CO2
PublicationSeveral solutions of ionic liquids based on 1-ethyl-3-methylimidazolium cation saturated and unsaturated with carbon dioxide were prepared and characterized by electrochemical impedance spectroscopy. The in fluence of ILs saturation on its electrical conductivity was determined. Additionally, the in fluence of the water presence and variations of temperature on electrical properties of ionic liquids were investigated. Changes of...
-
Tailoring the electrochemical degradation of iron protected with polypyrrole films for biodegradable cardiovascular stents
PublicationThe degradation of polypyrrole (PPy) coated iron is studied in phosphate buffer saline solution at 37 °C by odd random phase multisine electrochemical impedance spectroscopy (ORP-EIS). PPy is electropolymerized with anti-inflammatory salicylates incorporated in the film, as a drug release system. The modelling of EIS over time provides the quantitative description of the corrosion behaviour of the material. Thus, the reliable...
-
Leakage Current Measurements of Surge Arresters
PublicationThe paper presents the methods of assessing the technical condition of varistor surge arresters used in laboratory tests and in operation—performed without disconnecting the arresters from the network. The analysis of the diagnostic methods was supplemented with the results of the measurements of the leakage current of arresters coming directly from their production and used in the power industry. Among the available methods of...
-
Suppression of Supply Current Harmonics of 18-Pulse Diode Rectifier by Series Active Power Filter with LC Coupling
PublicationThe reported research aims at improving the quality of three-phase rectifier supply currents. An effective method consists of adding properly formed booster voltages to the fundamental supply voltages using a series active filter. In the proposed solution, the booster voltages are generated by three single-phase systems consisting of inverters, LC filters, and single-phase transformers. The application of LC couplings ensures low...
-
Structure and the space vector modulation for a medium-voltage power-electronic-transformer based on two seven-level cascade H-bridge inverters
PublicationThis study presents the structure and the space vector pulse-width modulation (SVPWM) for power electronic transformer (PET) based on two seven-level cascade H-bridge (CHB) inverters. The DC links of CHB inverters are coupled with nine dual-active bridge (DAB) converters with medium-frequency transformers. The DC-link voltages are equalised with two methods – through the control of DAB voltages...
-
Dual Active Bridge (DAB) DC-DC converter for multilevel propulsion converters for electrical multiple units (EMU)
PublicationSemiconductor power devices made from silicon carbide (SiC) reached a level of technology enabling their widespread use in power converters. Two different approaches to implementation of modern traction converters in electric multiple units (EMU) have been presented in recent years: (i) 3.3-kV SiC MOSFET-based three-level PWM inverter with regenerative braking and (ii) 6.5-kV IGBT-based four-quadrant power electronic traction transformer...
-
Weak forms of shadowing in topological dynamics
PublicationWe consider continuous maps of compact metric spaces. It is proved that every pseudotrajectory with sufficiently small errors contains a subsequence of positive density that is point-wise close to a subsequence of an exact trajectory with the same indices. Also, we study homeomor- phisms such that any pseudotrajectory can be shadowed by a finite number of exact orbits. In terms of numerical methods this property (we call it multishadowing)...
-
Formulation of Time-Fractional Electrodynamics Based on Riemann-Silberstein Vector
PublicationIn this paper, the formulation of time-fractional (TF) electrodynamics is derived based on the Riemann-Silberstein (RS) vector. With the use of this vector and fractional-order derivatives, one can write TF Maxwell’s equations in a compact form, which allows for modelling of energy dissipation and dynamics of electromagnetic systems with memory. Therefore, we formulate TF Maxwell’s equations using the RS vector and analyse their...
-
Evaluation of the efficiency of the duty cycle of refuse collection vehicle based on real-world data
PublicationIn this paper a method of the efficiency evaluation of the duty cycle of Refuse Collection Vehicle is presented. Using real world data, two representative duty cycles were analysed. Total cycle efficiency was calculated, as well as the efficiency of particular cycle phases. Then, energy needed to collect and compact the waste and energy from fuel were compared. Measured and calculated values were shown on the diagrams illustrating...
-
Microstructure and Dielectric Properties of Barium-vanadate Glasses
PublicationThe ac and dc conductivity in barium-vanadate glasses was investigated as a function of temperature and frequency with the use of impedance spectroscopy. The topography and microstructure of glasses were investigated by the means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The XRD results show that all samples are amorphous but microscopy investigation reveals that glasses with greater amount of V2O5...
-
Efficient Finite Element Analysis of Axially Symmetrical Waveguides and Waveguide Discontinuities
PublicationA combination of the body-of-revolution and finite element methods is adopted for full-wave analysis of waveguides and waveguide discontinuities involving angular field variation. Such an approach is highly efficient and much more flexible than analytical techniques. The method is performed in two different cases: utilizing a generalized impedance matrix to determine the scattering parameters of a single waveguide section and utilizing...
-
Improved performance of LaNi0.6Fe0.4O3 solid oxide fuel cell cathode by application of a thin interface cathode functional layer
PublicationIn this work, novel functional layers were prepared by a low temperature spray pyrolysis method on the oxygen side of the solid oxide cells. Thin layers of Ce0.8Gd0.2O2 and LaNi0.6Fe0.4O3 are prepared between the electrolyte and the porous oxygen electrode. Additionally the influence of the sprayed ceria barrier layer on the zirconia based electrolyte with the new layers is evaluated. Impedance spectroscopy results show improvement...
-
Induction machine behavioral modeling for prediction of EMI propagation.
PublicationThis paper presents the results of wideband behavioral modeling of an induction machine (IM). The proposed solution enables modeling the IM differential- and common-mode impedance for a frequency range from 1 kHz to 10 MHz. Methods of parameter extraction are derived from the measured IM impedances. The developed models of 1.5 kW and 7.5 kW induction machines are designed using the Saber Sketch scheme editor and simulated in the...
-
Phospholipid-functionalized gold electrode for cellular membrane interface studies - interactions between DMPC bilayer and human cystatin C
PublicationThis work describes the electrochemical studies on the interactions between V57G mutant of human cystatin C (hCC V57G) and membrane bilayer immobilized on the surface of a gold electrode. The electrode was modified with 6-mercaptohexan-1-ol (MCH) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). DMPC was used as a membrane mimetic for monitoring electrochemical changes resulting from the interactions between the functionalized...
-
Corrosion Resistance and Surface Bioactivity of Ti6Al4V Alloy after Finish Turning under Ecological Cutting Conditions
PublicationThe influence of cooling conditions and surface topography after finish turning of Ti6Al4V titanium alloy on corrosion resistance and surface bioactivity was analyzed. The samples were machined under dry and minimum quantity lubrication (MQL) conditions to obtain different surface roughness. The surface topographies of the processed samples were assessed and measured using an optical profilometer. The produced samples were subjected...
-
Discriminating macromolecular interactions based on an impedimetric fingerprint supported by multivariate data analysis for rapid and label-free Escherichia coli recognition in human urine
PublicationThis manuscript presents a novel approach to address the challenges of electrode fouling and highly complex electrode nanoarchitecture, which are primary concerns for biosensors operating in real environments. The proposed approach utilizes multiparametric impedance discriminant analysis (MIDA) to obtain a fingerprint of the macromolecular interactions on flat glassy carbon surfaces, achieved through self-organized, drop-cast,...