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Search results for: frequency-dependent couplings

Search results for: frequency-dependent couplings

  • Flicker Noise in Resistive Gas Sensors—Measurement Setups and Applications for Enhanced Gas Sensing

    Publication

    - SENSORS - Year 2024

    We discuss the implementation challenges of gas sensing systems based on low-frequency noise measurements on chemoresistive sensors. Resistance fluctuations in various gas sensing materials, in a frequency range typically up to a few kHz, can enhance gas sensing by considering its intensity and the slope of power spectral density. The issues of low-frequency noise measurements in resistive gas sensors, specifically in two-dimensional...

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  • Comparative study of flow condensation in conventional and small diameter tubes

    Flow boiling and flow condensation are often regarded as two opposite or symetrical phenomena. Their description however with a single correlation has yet to be suggested.In the case of flow boiling in minichannels there is mostly encountered the annular flow structure, where the buble generetion is not present. Similar picture holds for the case of inside tube condensation, where annular flow structure predominates. In such case...

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  • Coupling between Blood Pressure and Subarachnoid Space Width Oscillations during Slow Breathing

    Publication

    - ENTROPY - Year 2021

    The precise mechanisms connecting the cardiovascular system and the cerebrospinal fluid (CSF) are not well understood in detail. This paper investigates the couplings between the cardiac and respiratory components, as extracted from blood pressure (BP) signals and oscillations of the subarachnoid space width (SAS), collected during slow ventilation and ventilation against inspiration resistance. The experiment was performed on...

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  • Dynamics analysis of footbridge mode shapes the s8 expressway on the basis of the results of in situ tests

    Publication

    - Year 2016

    Non-destructive diagnostics for structure may use dynamic measurements realized during vibrations of a facility induced by dynamic environmental impact, enforced by the use of inductors or impulse impact. Dynamic tests and the analysis were undertaken for a footbridge situated over the expressway S8. The studies in situ allowed for dynamic characteristics to be determined: frequency, shape modes and damping for respective frequency...

  • Transient detection for speech coding applications

    Signal quality in speech codecs may be improved by selecting transients from speech signal and encoding them using a suitable method. This paper presents an algorithm for transient detection in speech signal. This algorithm operates in several frequency bands. Transient detection functions are calculated from energy measured in short frames of the signal. The final selection of transient frames is based on results of detection...

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  • Microwave Alignment and Displacement Sensors in Groove Gap Waveguide Technology

    This paper is aimed at presenting highly sensitive microwave displacement and alignment sensors. With this goal, the method of realizing mechanically tunable cavity resonators in groove gap waveguides technology is presented. The resonance frequency of the cavity is then used for displacement sensing. It is also demonstrated that the symmetry properties of a pair of groove gap waveguide cavities can be used to improve the robustness...

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  • Neural network based algorithm for hand gesture detection in a low-cost microprocessor applications

    In this paper the simple architecture of neural network for hand gesture classification was presented. The network classifies the previously calculated parameters of EMG signals. The main goal of this project was to develop simple solution that is not computationally complex and can be implemented on microprocessors in low-cost 3D printed prosthetic arms. As the part of conducted research the data set EMG signals corresponding...

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  • Distance measurement errors in silent FM-CW sonar with matched filtering

    The secretiveness of sonar operation can be achieved by using continuous frequency-modulated sounding signalswith reduced power and significantly prolonged repeat time. The application of matched filtration in the sonarreceiver provides optimal conditions for detection against the background of white noise and reverberation, and avery good resolution of distance measurements of motionless targets. The article shows that target...

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  • Analysis of the Usefulness of Cheap Audio Recorders for Spectral Measurement of Environmental Noise

    Environmental noise pollution is nowadays one of the most serious health threats. The impact of noise on the human body depends not only on the sound level but also on its spectral distribution. Reliable measurements of the environmental noise spectrum are often hampered by the very high price of top quality measuring devices. This paper explores the possibility of using much cheaper audio recorders for the frequency analysis....

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  • WARUNKI REZONANSOWE W WĘŹLE Z KOMPENSATOREM SVC

    Instalowanie kompensatorów statycznych w sieciach rozdzielczych i przesyłowych służy poprawie profili napięciowych. Kompensatory jako źródła mocy biernej zwiększają stabilność napięciową systemu. Pozwalają także na szybszą odbudowę systemu w przypadku awarii napięciowej. W artykule zaprezentowano wpływ struktury i wysterowania układu SVC na zmianę impedancji w układzie zasilania. Ma to bezpośredni wpływ na częstotliwości, przy...

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  • Spectral Finite Element Method in Condition Monitoring and Damage Detection

    Publication

    It is well known that the dynamic behaviour of engineering structures may carry very important and crucial information that can be further used for the assessment of their condition as well as detection of any damage induced. The current interest in monitoring techniques based on the propagation of guided elastic waves requires that numerical techniques used for modelling the phenomena associated must shift into the realm of high...

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  • Waveguide model of the hearing aid earmold system

    Publication

    - Year 2006

    Background The earmold system of the Behind-The-Ear hearing aid is an acoustic system that modifies the spectrum of the propagated sound waves. Improper selection of the earmold system may result in deterioration of sound quality and speech intelligibility. Computer modeling methods may be useful in the process of hearing aid fitting, allowing physician to examine various earmold system configurations and choose the optimum one...

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  • Waveguide model of the hearing aid earmold system

    Publication

    Background The earmold system of the Behind-The-Ear hearing aid is an acoustic system that modifies the spectrum of the propagated sound waves. Improper selection of the earmold system may result in deterioration of sound quality and speech intelligibility. Computer modeling methods may be useful in the process of hearing aid fitting, allowing physician to examine various earmold system configurations and choose the optimum one...

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  • A concept of Signal Equalization Method Based on Music Genre and the Listener's Room Characteristics

    Publication

    - Year 2016

    A research study that investigates the influence of the room acoustics environment on the frequency characteristic of the audio signal playback is presented. First, a novel spectral equalization method of the room acoustic conditions is introduced. On the basis of the frequency response of the room, a system for room acoustics compensation based on eight-band equalizer is proposed. The system settings depend on music genre. In...

  • Generation-recombination and 1/f noise in carbon nanotube networks

    Publication
    • A. Rehman
    • A. Krajewska
    • B. Stonio
    • K. Pavlov
    • G. Cywinski
    • D. Lioubtchenko
    • W. Knap
    • S. Rumyantsev
    • J. Smulko

    - APPLIED PHYSICS LETTERS - Year 2021

    The low-frequency noise is of special interest for carbon nanotubes devices, which are building blocks for a variety of sensors, including radio frequency and terahertz detectors. We studied noise in as-fabricated and aged carbon nanotube networks (CNNs) field-effect transistors. Contrary to the majority of previous publications, as-fabricated devices demonstrated the superposition of generation-recombination (GR) and 1/f noise...

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  • Smart acoustic band structures

    Publication

    Smart acoustic band structures exhibit very interesting and non-standard physical properties due to the periodic nature of their certain characteristic on different scale levels. They manifest mostly in their frequency spectra as socalled frequency band-gaps or stop-bands, what has a great impact on the behaviour of these structures in relation to the propagation of vibro-acoustic signals that can be transmitted through the structures...

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  • Design of Microwave-Based Angular Displacement Sensor

    Publication

    This letter presents a novel microwave-based rotation sensor having a wide dynamic range to detect and measure the angular displacement in terms of the change in resonant frequency. The proposed sensor is based on the microstrip technology, where a rotor comprised of a complementary splitring resonator (CSRR) placed on the ground plane of the microstrip line is free to rotate around its axis. The mechanical rotation of CSRR determines...

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  • Planar Microwave Bragg Reflector Resonant Dielectric Sensor

    Publication

    - Year 2019

    In this paper, a periodic structure is used to design a microwave Bragg reflector with the help of hexagonal lattice, which provides a 5 GHz wide stopband between the low-pass band with cut-off frequency 2.6 GHz and the bandpass response with start and stop frequency 7.8 GHz and 10.5 GHz, respectively. A defect in lattice allows passing a narrowband signal at 6 GHz which is found, from the dispersion relation, to be in the region...

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  • Continuous blood pressure monitoring by photoplethysmography - signal preprocessing requirements based on blood flow modelling

    Publication

    Objective. The aim of the study is to investigate the effect of the signal sampling frequency and low-pass filtering on the accuracy of the localisation of the fiducial points of the photoplethysmographic signal (PPG), and thus on the estimation of the blood pressure (i.e. the accuracy of the estimation). Approach. Statistical analysis was performed on 3,799 data samples taken from a publicly available database. Four PPGfiducial...

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  • Pollutant deposition via dew in urban and rural environment, Cracow, Poland

    Publication

    - ATMOSPHERIC RESEARCH - Year 2015

    This study is a comparative analysis of dew in rural and urban environment. Dew samples were collected between May and October, 2009 in two reference stations in southern Poland: Cracow and Gaik-Brzezowa. The investigation included comparison of volume and chemistry of the collected samples. Due to its formation mechanisms, dew is a good indicator of air pollution. Following parameters were analyzed in 159 collected samples: pH,...

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  • Voltage Harmonics Transfer through Medium Voltage Instrument Transformers

    Publication

    Voltage transformers are widely used in power quality monitoring systems in medium and high voltage grids. This paper presents accuracy problems related to voltage harmonics transfer through instrument transformers. A simplified lumped-parameters wideband circuit model of the voltage transformer is proposed and verified by simulation and experimental investigations. A number of voltage transformers have been tested in the frequency...

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  • New Algorithms for Adaptive Notch Smoothing

    The problem of extraction/elimination of a nonstationary complex sinusoidal signal buried in noise is considered. This problem is usually solved using adaptive notch filtering (ANF)algorithms. It is shown that accuracy of signal estimation can be increased if the results obtained from ANF are further processed using a cascade of appropriately designed filters. The resulting adaptive notch smoothing (ANS) algorithms can be employed...

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  • Simplified Method of Modelling Behaviour of Ship in Waves with Partially Flooded Compartments

    Publication
    • P. Szulczewski

    - Transactions on Maritime Science-ToMS - Year 2021

    This paper contains a description of a numerical model for calculating behaviour of ships in waves. There are many models available, but the one described here can be characterised with a set of parameters that have a decisive impact on the final values of roll motion amplitude and frequency. In this paper, it is shown how a fitting of a standard-shape hull characterised by certain readily available parameters affects...

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  • Voltage Transients Transfer over Medium Voltage Instrument Transformers

    Publication

    - Year 2011

    This paper presents voltage harmonic transfer accuracy problems through voltage transformers which are used in power quality monitoring systems in medium and high voltage grids. A simplified lumped parameters circuit model of the voltage transformer is proposed and verified by simulation and experimental investigations. A number voltage transformers typically used in medium voltage grid has been tested in the conducted disturbances...

  • Stress Detection of Children With ASD Using Physiological Signals

    Publication
    • S. N. B. Aktas
    • P. Uluer
    • B. Coskun
    • E. Toprak
    • D. E. Barkana
    • H. Kose
    • T. Zorcec
    • B. Robins
    • A. Landowska

    - Year 2022

    This paper proposes a physiological signal-based stress detection approach for children with autism spectrum disorder (ASD) to be used in social and assistive robot inter- vention. Electrodermal activity (EDA) and blood volume pulse (BVP) signals are collected with an E4 smart wristband from children with ASD in different countries. The peak count and signal amplitude features are derived from EDA signal and used in order to detect...

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  • Music signal equalization in a changing environment

    Publication

    - Year 2019

    The paper presents the concept of an automatic system for music signal correction, considering room frequency response and music genre being played. The proposed algorithm, based on the room frequency response, compensates acoustic conditions surrounding the sound source. Additionally, the compensation process considers the signal content by recognizing music genre. As part of the described research, a series of subjective tests...

  • A concept of software extension of 3D low-PRF radar systems to 4D semi-medium-PRF radar systems

    Publication

    We present a concept of software modification of three-dimensional (3D) radar systems, designed to work in the low pulse repetition frequency mode, that equips them with the ability to estimate the radial velocity and to properly measure the range of targets that are detected outside the radar’s instrumented range. Despite the fact that the proposed modifications are designed so as to require only minor changes in software, they...

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  • Analysis of the Factors Affecting Static In Vitro Pepsinolysis of Food Proteins

    In this meta-analysis, we collected 58 publications spanning the last seven decades that reported static in vitro protein gastric digestion results. A number of descriptors of the pepsinolysis process were extracted, including protein type; pepsin activity and concentration; protein concentration; pH; additives; protein form (e.g., ‘native’, ‘emulsion’, ‘gel’, etc.); molecular weight of the protein; treatment; temperature; and...

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  • Factory Acceptance Test – Strain Gauge Measurement, Report no: WOiO /II/123/2014

    Publication

    Tested object was 40 meters long jib and its foundation, placed in Gdansk Shiprepair Yard, manufactured by KMK. The contruction was dedicated to the passenger cruise vessel "Quantum of the Seas" The Strain Gauge measurement in different location and load situation was done in order to validate calculation finite element models used during strength analysis for project. The expertise contains: methodology of the measurements, description...

  • Factory Acceptance Test – Strain Gauge Measurement - Report no: WOiO /II/88/2014

    Publication

    Tested object was 40 meters long jib and its foundation, placed in Gdansk Shiprepair Yard, manufactured by KMK. The contruction was dedicated to the passenger cruise vessel "North Star" The Strain Gauge measurement in different location and load situation was done in order to validate calculation finite element models used during strength analysis for project. The expertise contains: methodology of the measurements, description...

  • Evidence for SrHo2O4 and SrDy2O4 as model J1- J2 zigzag chain materials

    Publication
    • A. Fennell
    • V. Y. Pomjakushin
    • A. Uldry
    • B. Delley
    • B. Prévost
    • A. Désilets-Benoit
    • A. D. Bianchi
    • R. I. Bewley
    • B. R. Hansen
    • T. Klimczuk... and 2 others

    - PHYSICAL REVIEW B - Year 2014

    Neutron diffraction and inelastic spectroscopy is used to characterize the magnetic Hamiltonian of SrHo2O4 and SrDy2O4. Through a detailed computation of the crystal-field levels we find site-dependent anisotropic single-ion magnetism in both materials, and diffraction measurements show the presence of strong one-dimensional spin correlations.Our measurements indicate that competing interactions of the zigzag chain, combinedwith...

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  • Gas turbines – technological development and potential use in CAES systems

    Publication

    This article briefly describes Compressed Air Energy Storage (CAES), focusing on the technological development of one of the key elements of such systems – the gas turbines. It presents the basic parameters and features of gas turbines, as well as turbine classes with example models. Main tendencies in the structural and technological development are discussed. Changes and trends on electric energy markets are becoming more and...

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  • Nonlinear electrical properties of glass-ceramics nanocomposites containing ferroelectric nanocrystallites of Bi2VO5.5

    Nonlinear A.C. impedance measurements were conducted in the 50BiV-50SrBAlO nanocomposite as a function of frequency, temperature and A.C. voltage. This material is ferroelectric below temperature of 730 K, and above 730 K is a good ion-conductor. For this nanocomposite a low A.C. voltage of 1 V rms is enough to observe high nonlinearities. The origin of these nonlinear effects depends on the temperature and frequency. In the high...

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  • Independent dynamics of slow, intermediate, and fast intracranial EEG spectral activities during human memory formation

    Publication

    - Year 2021

    A wide spectrum of brain rhythms are engaged throughout the human cortex in cognitive functions. How the rhythms of various low and high frequencies are spatiotemporally coordinated across the human brain during memory processing is inconclusive. They can either be coordinated together across a wide range of the frequency spectrum or induced in specific bands. We used a large dataset of human intracranial electroencephalography...

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  • Low-Profile Interdigitated UHF RFID Tag Antenna for Metallic Objects

    Publication
    • F. Erman
    • D. Mansour
    • M. Kouali
    • A. Shabaneh
    • L. Leifsson
    • S. Kozieł
    • E. Hanafi

    - IEEE Access - Year 2022

    This article presents a novel miniature interdigitated ultra-high frequency (UHF) radio frequency identification (RFID) tag antenna that can be placed on metallic objects. The tag structure comprises two horizontal strip lines, each loaded with seven identical open stubs, and an integrated circuit (IC) chip connected directly to the feed lines in the middle of the structure. The perfect match to the IC chip’s impedance is realized...

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  • Behavior of residual current devices at frequencies up to 50 kHz

    Publication

    - ENERGIES - Year 2021

    The use of residual current devices (RCDs) is obligatory in many types of low-voltage circuits. They are devices that ensure protection against electric shock in the case of indirect contact and may ensure additional protection in the case of direct contact. For the latter purpose of protection, only RCDs of a rated residual operating current not exceeding 30 mA are suitable. Unfortunately, modem current-using equipment supplied...

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  • Fast geometry scaling of miniaturized microwave couplers with power split correction

    Redesigning a microwave circuit for various operating conditions is a practically important yet challenging problem. The purpose of this article is development and presentation of a technique for fast geometry scaling of miniaturized microwave couplers with respect to operating frequency. Our approach exploits an inverse surrogate model constructed using several reference designs that are optimized for a set of operating frequencies...

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  • Expedited simulation-driven design optimization of UWB antennas by means of response features

    In this work, a method for fast design optimization of broadband antennas is considered. The approach is based on a feature-based optimization (FBO) concept where reflection characteristics of the structure at hand are formulated in terms of suitably defined feature points. Redefinition of the design problem allows for reducing the design optimization cost, because the dependence of feature point coordinates on antenna dimensions...

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  • A Geometrically Simple Compact Wideband Circularly Polarized Antenna

    Publication

    A compact broadband wide-slot circular polarization (CP) antenna is proposed. An inverted L-shape parasitic strip at the open end of a microstrip line extension and a slot modification is applied to attain wideband CP. The advantage of this technique is simplicity which makes it readily re-designable for different frequency bands. To demonstrate the concept, three designs working at different frequencies are obtained. The redesign...

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  • An Analysis of Elliptical-Rectangular Multipatch Structure on Dielectric-Coated Confocal and Nonconfocal Elliptic Cylinders

    A rigorous analysis of the resonance frequency problem of an elliptical-rectangular microstrip structure mounted on dielectric-coated elliptic conducting cylinder, with electrically small radius, is investigated in this paper. A full-wave analysis and a moment-method calculation are employed. The analysis is carried out considering the expansion of the field as a series of Mathieu functions. The complex resonance frequencies of...

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  • Nonlinear Impedance as Possible Result of Ion-Polaron Interaction in Cu2O-Al2O3-SiO2 Glass

    Nonlinear a.c. impedance measurements were performed in Cu2O-Al2O3-SiO2 glass in wide frequency range. The obtained results shows that a large nonlinearity in the impedance signal is observed at moderate electric fields of an order 1V/mm. The contents of the third harmonics reaches about 10% and strongly depends on temperature and frequency. The investigated glass exhibits mixed electronic-ionic conductivity. Electronic conduction...

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  • Miniaturized uniplanar triple-band slot dipole antenna with folded radiator

    A miniaturized uniplanar slot dipole for triple-frequency operation is presented. The antenna consists of a folded slot radiator with an increased number of degrees of freedom that allow for efficient size reduction. Rigorous electromagnetic (EM)-driven design optimization is applied in order to achieve the smallest possible size while maintaining acceptable levels of antenna reflection at the required operating frequencies. The...

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  • Simulation of Signal Propagation Along Fractional-Order Transmission Lines

    Publication

    - Year 2020

    In this paper, the simulation method of signal propagation along fractional-order (FO) transmission lines is presented. Initially, fractional calculus and the model of FO transmission line are introduced. Then, the algorithm allowing for simulation of the nonmonochromatic wave propagation along FO transmission lines is presented. It employs computations in the frequency domain, i.e., an analytical excitation is transformed to the...

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  • Sound signals generated during lapping of technical ceramics using electroplated tools with diamond grains

    Open Research Data
    open access

    Data contains the recordings of sound generated during single-sided lapping with the use of electroplated diamond tools. This relationship was examined with the use of spectral analysis of the sound signal in the frequency domain with a focus on the Ra parameter of the surface roughness. The estimated sound coefficient increased as the surface roughness...

  • Strategies for computationally feasible multi-objective simulation-driven design of compact RF/microwave components

    Multi-objective optimization is indispensable when possible trade-offs between various (and usually conflicting) design objectives are to be found. Identification of such design alternatives becomes very challenging when performance evaluation of the structure/system at hand is computationally expensive. Compact RF and microwave components are representative examples of such a situation: due to highly compressed layouts and considerable...

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  • Expedited EM-Driven Design of Miniaturized Microwave Hybrid Couplers Using Surrogate-Based Optimization

    Publication

    - Year 2017

    Miniaturization of microwave hybrid couplers is important for contemporary wireless communication engineering. Using standard computer-aided design methods for development of compact structures is extremely challenging due to a general lack of computationally efficient and accurate simulation models. Poor accuracy of available equivalent circuits results from neglecting parasitic cross-couplings that greatly affect the performance...

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  • Suppression of Supply Current Harmonics of 18-Pulse Diode Rectifier by Series Active Power Filter with LC Coupling

    Publication

    - ENERGIES - Year 2020

    The 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...

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  • Security Evaluation of IT Systems Underlying Critical Networked Infrastructures

    Publication

    - Year 2008

    Critical infrastructures have become highly dependent on information and communication technology (ICT). The drawback of this situation is that the consequences of disturbances of the underlying ICT networks may be serious as cascading effects can occur. This raises a high demand for security assurance, with a high importance assigned to security evaluations. In this paper we present an experiment-centric approach for the characterisation...

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  • Security ontology construction and integration

    Publication

    - Year 2011

    There are many different levels on which we can examine security. Each one is different from others, all of them are dependent on the context. Hence the need to bear additional knowledge enabling efficient utilization of the knowledge by the computers. Such information can be provided by ontologies. The paper presentsgathered requirements needed to be taken into account when creating an ontology. The method of ontology creation...

  • Correlated Particle Motion and THz Spectral Response of Supercritical Water

    Publication

    - PHYSICAL REVIEW LETTERS - Year 2016

    Molecular dynamics simulations of supercritical water reveal distinctly different distance-dependent modulations of dipolar response and correlations in particle motion compared to ambient conditions. The strongly perturbed H-bond network of water at supercritical conditions allows for considerable translationaland rotational freedom of individual molecules. These changes give rise to substantially different infrared spectra and...

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