Search
Filters
total: 2773
filtered: 2239
-
Catalog
Chosen catalog filters
displaying 1000 best results Help
Search results for: MEDIUM FREQUENCY TRANSFORMER
-
Low-frequency tripping characteristics of residual current devices
PublicationFast development of various types of converters makes their utilization in industry and in domestic installations very common. Due to converters, an earth fault current waveform in modern circuits can be distorted or its frequency can be different than 50/60 Hz. Frequency of earth fault (residual) current influences tripping of residual current devices which are widely used in low voltage systems. This paper presents the behaviour...
-
Digital Processing of Frequency–Pulse Signal in Measurement System
PublicationThe work presents the issue of the use of multichannel measurement systems of sensors processing input value to impulse signal frequency. The frequency impulse signal obtained from such sensors is often required to be processed at the same time with a voltage signal which is obtained from other sensors used in the same measurement system. In such case, it is usually necessary to sample the output signals from all sensors in the...
-
Properties and interpretation of Instantaneous Complex Frequency
PublicationThe concept of Instantaneous Complex Frequency (ICF) was first defined by Lindon and developed mainly in works of two authors S. Hahn and M. Rojewski. Although it is not widely used in signal analysis, ICF was already used as a complex signal representation in the verification of handwritten signatures, pitch estimation, symbol timing recovery in PSK receiver and in detection of anomalies in data transmission. It should be noted,...
-
Design analysis of Tesla micro-turbine operating on a low-boiling medium
PublicationThis paper presents results of the design analysis of a Tesla bladeless turbine intended for a co-generating micro-power plantof heat capacity 20 kW, which operates in an organic Rankine cycle on a low-boiling medium. Numerical calculations of flowin several Tesla turbine models were performed for a range of design parameters. Results of investigations exhibit interestingfeatures in the distribution of flow parameters within the...
-
N-point estimators of the Instantaneous Complex Frequency
PublicationIn this paper estimators of the instantaneous complex frequency (ICF) are presented and discussed. The differential approach for the estimation of the ICF is used, therefore the estimators are based on maximally flat N-point FIR filters: differential and delay. The investigation of the filter performance includes static characteristics of ICF estimation and the error of the ICF estimation in the discrete frequency domain.W pracy...
-
A novel method of time-frequency analysis: an essential spectrogram
PublicationA novel precise method of time-frequency analysis is presented. In the algorithm, a new energy distribution is estimated by simultaneously discard or displacement of the classical spec- trogram energy. A channelized instantaneous frequency and a local group delay are used in order to replacement in the same manner as formulated by Kodera et al. [1, 2]. Additionally, new representations: a channelized instantaneous bandwidth and...
-
Dissecting gamma frequency activities during human memory processing
PublicationGamma frequency activity (30-150 Hz) is induced in cognitive tasks and is thought to reflect underlying neural processes. Gamma frequency activity can be recorded directly from the human brain using intracranial electrodes implanted in patients undergoing treatment for drug-resistant epilepsy. Previous studies have independently explored narrowband oscillations in the local field potential and broadband power increases. It is not...
-
On ship roll resonance frequency
PublicationThe paper deals with the problem of modeling of rolling motion under a variety of excitation parameters. Special emphasis is put on the analysis and prediction of the frequency of the resonant mode of rolling, since it is often an essential issue in terms of motion of a ship related to her safety against capsizing or excessive amplitudes of roll. The research is performed for both free rolling and excited rolling and it is based...
-
Earthquake-Induced Pounding of Medium-to-High-Rise Base-Isolated Buildings
PublicationDuring earthquakes, out-of-phase vibrations in adjacent buildings with limited distance may cause pounding between them. In recent years, the use of seismic isolation has expanded considerably as an effective approach to reduce seismic damage. However, the isolated building experiences large displacements during earthquakes, and there is a possibility of collisions with adjacent structures. The research on earthquake-induced pounding...
-
Knowledge management approaches of small and medium-sized firms: a cluster analysis
PublicationPurpose This paper aims to categorise the approaches to knowledge management (KM) by companies. In the literature, there is no consensus on a universal or “best” approach to KM. Especially, this paper singles out and discusses the variegated features that characterise the implementation of KM by small- and medium-sized enterprises (SMEs) having different characteristics. Design/methodology/approach A cluster analysis was used...
-
Influence of Heat Treatment Temperature on Fatigue Toughness in Medium-Carbon High-Strength Steels
PublicationCurrent research has demonstrated that the tempering temperature affects the martensitic transformation of medium-carbon high-strength steels. This temperature plays an important role in the final microstructure, percentage ratios of martensite to ferrite phases and, consequently, in the mechanical properties and the fatigue response. So far, the relationship between the martensitic tempering temperature and the cyclic deformation...
-
Low Frequency Conducted Emissions of Grid Connected Static Converters
PublicationPulse-width modulated rectifiers are nowadays commonly used for AC to DC power conversion. PWM rectification technology is very effective and allows for bidirectional power flow with the possibility of power factor improvement and low-order harmonic emission limitation. Unfortunately, employed PWM boost topology results with generation of input current harmonic distortions in a frequency range tightly correlated to modulation frequency....
-
Detection and time/frequency analysis of electric fields in the ground
PublicationThis paper sets out to detect and characterize electric fields in the ground (such as stray current fields) using a tandem time/frequency method of signal analysis. Results were obtained from investigations performed in the presence of a generated electric field with controlled variable characteristics, and in the presence of an electric field generated by a tramline. The analysis of measurement registers was performed using Short‐Time...
-
Design of a simple modular active power electronic transformer
Publication -
Some remarks on the design of microstrip to coplanar line transformer.
PublicationPrzedyskutowano technikę projektowania transformatora standardu umożliwiającego współpracę linii mikropaskowej i linii koplanarnej. Jako sekcję pośrednią wykorzystano uziemiony falowód koplanarny (conductor backed coplanar waveguide). Dokonano oceny różnych profili sekcji pośredniej w oparciu o szereg symulacji elektromagnetycznych, jak i pomiarów charakterystyk transmisji wykonanych modeli transformatorów.
-
Demagnetization of the core and reduction of power transformer inrush current
PublicationW artykule przedstawiono metodę ograniczenia prądów włączania transformatora energetycznego za pomocą demagnetyzacji rdzenia magnetycznego. Jako źródło energii do demagnetyzacji w proponowanej metodzie zastosowano kondensator. Do wytworzenia pola rozmagnesowującego wykorzystano uzwojenia robocze transformatora. Przeprowadzono obliczenia magnetyzmu szczątkowego rdzenia po demagnetyzacji dla różnych wartości pojemności, napięcia...
-
Effect of power frequency on the stress state of disc actuator
PublicationThis paper presents the concept of determining the optimum frequency of coil supply in inductive-dynamic drive. As a criterion to obtain the sought frequency, the smallest value of reduced stress in the disc was assumed while maintaining the desired dynamics. The disc stress is determined on the basis of solution of vibrating thin plate equation. Magnetic pressure acting on the disc is obtained from a hybrid circumferentially-field...
-
The Effect of Posaconazole, Itraconazole and Voriconazole in the Culture Medium on Aspergillus fumigatus Triazole Resistance
PublicationTriazoles are the only compounds used as antibiotics in both medicine and agriculture. The presence of triazoles in the environment can contribute to the acquisition of azole resistance among isolates of Aspergillus fumigatus. The objective of this study was to investigate the effect of A. fumigatus exposure to triazoles on susceptibility to these compounds. Seventeen triazole-resistant and 21 triazole-sensitive A. fumigatus isolates...
-
Analysis and Detection of Faults at Insulated Conductors of Overhead Medium Voltage Lines
PublicationThe paper dealt with the issue of breakdowns detection of isolated hanging wires on the medium-voltage transmission. The main aim of article is to describe the function of created breakdowns detector and evaluation its. The breakdowns detector is created based in indicators of faults such as touch between tree limbs and insulated wire, touch tree limbs with several phases or fall insulated wire on the ground. Breakdowns detector...
-
HOW TO ASSESS THE MATURITY OF SMALL AND MEDIUM-SIZED ENTERPRISES TO LEAN SIX SIGMA PROJECTS
PublicationThis article describes the considerations for the implementation of the Lean Six Sigma (LSS) methodology in small and medium-sized enterprises. Pilot research was conducted in Polish and French SMEs (nine Polish and nine French enterprises from the service and production sectors) referring to the context of the implementation and application of the Lean Six Sigma concept. The studies led to the identification of the motives, needs,...
-
Modelling of high frequency dynamic responses of engineering structures
PublicationModelling of high frequency dynamic responses of engineering structures, especially those related to wave propagation, is a real numerical challenge. Nowadays most of numerical models, used for that purpose, are based on the application of various finite element techniques. However, finite element discrete models may also be considered as possessing certain periodic structures, which may manifest themselves in particular scenarios....
-
Temperature influence on tyre/road noise frequency spectra
PublicationThe correction for temperature effect on measured tyre/road noise is very important as it may be one of the main sources of errors in measurement results due to substantial influence of this parameter on obtained values. The latest version of the Technical Specification ISO/CD TS 13471-1 about Temperature Corrections contains a proposal of correction procedure for normalizing measured noise levels to a reference air temperature...
-
Training Services in Small and Medium-sized Enterprises: Evidence from Poland
PublicationIn the knowledge-based economy knowledge and skills are becoming more and more significant for the success of companies. This applies also to firms from small and medium-sized enterprises (SMEs) sector. As large companies in many cases posses special divisions devoted to trainings, they normally have no problems with updating the knowledge and skills of their employees. The situation is different with regard to SMEs, which often...
-
Assessment of preparedness for Lean Six Sigma projects in small and medium-sized organizations
PublicationThe article presents a proposal for the maturity indicator of Lean Six Sigma projects within the framework of the original comprehensive methodology of Lean Six Sigma implementation dedicated to the SME sector. The indicator allows an LSS project to be matched to the real needs and preparedness of any small or medium-sized organization. The indicator was designed as a result of pilot research conducted in Polish and French SMEs...
-
Chirp-rate estimation of FM signals in the time-frequency domain
PublicationNovel dynamic representations of a complex signal in the time-frequency domain including: a channelized instantaneous complex frequency (CICF), a complex local group delay (CLGD) and a channelized instantaneous chirp-rate (CICR) are introduced. The proposed approach is based on the use of the gradient of the short-time Fourier transform complex phase. An interpretation of the newly-introduced distributions especially of the CICR...
-
Knowledge Safety in Small and Medium Sized Service Companies:Case Study Analysis
PublicationPurpose: This paper aims to explore the topic of knowledge safety, defined as the state of knowledge being safe from loss, attrition, oblivion or theft. The paper first presents a theoretical background and review of previous studies on knowledge loss and retention and then illustrates the topic of knowledge safety with ten case studies from the small and medium-sized enterprises (SMEs) sector. Methodology: The paper is based...
-
Extending the Frequency Limit of Microstrip-Coupled CSRR Using Asymmetry
PublicationAbstract— This article explains the frequency limitation in designing microstrip circuits based on a complementary split-ring resonator (CSRR) and reports a novel technique for increasing its operating frequency, which makes the CSRR suitable for high-frequency applications. This study helps in synthesizing the dimensions of symmetric CSRR (SCSRR) and asymmetric CSRR (ACSRR) circuits, which shows the applicability of the proposed...
-
Improvement of Task Management with Process Models in Small and Medium Software Companies
PublicationSmall and medium software companies exhibit many special features that give reason for a dedicated approach to process improvement. They often cannot afford implementing maturity models or quality standards both in terms of time and money. Instead, they expect simpler solutions that can allow to run projects in more systematic and repeatable way, increase quality and knowledge management. In this paper, we present a method focused...
-
Shaping the competence of future spatial policymakers for small- and medium-sized towns
PublicationIn this article, the authors aim to present issues addressed within the framework of the architecture and spatial development courses offered by the Faculty of Architecture at Gdańsk University of Technology (FA-GUT), Gdańsk, Poland. These issues concern competence in the education of future spatial planners and their readiness to deal with the development challenges facing small- and medium-sized towns. Within the article, the...
-
Tinnitus Therapy Based on High-Frequency Linearization
PublicationThe aim of this work was to present problems related to tinnitus symptoms, its pathogenesis, hypotheses on tinnitus causes, and therapy treatments to reduce or mask the phantom noise. In addition, the hypothesis on the existence of parasitic quantization that accompanies hearing loss was recalled. The paper contains a description of experiments carried out with the application of high-frequency dither having specially formed spectral...
-
A Model-Order Reduction Approach for Electromagnetic Problems With Nonaffine Frequency Dependence
PublicationThe aim of this paper is to present a novel model-order reduction (MOR) technique for the efcient frequency-domain nite-element method (FEM) simulation of microwave components. It is based on the standard reduced-basis method, but the subsequent expansion frequency points are selected following the so-called sparsied greedy strategy. This feature makes it especially useful to perform a fast-frequency sweep of problems that lead...
-
Small and Medium-Sized Enterprises in Poland
Publication -
Automatic Optimization Of Adaptive Notch Filter’s Frequency Tracking
PublicationEstimation of instantaneous frequency of narrowband com- plex sinusoids is often performed using lightweight algo- rithms called adaptive notch filters. However, to reach high performance, these algorithms require careful tuning. The paper proposes a novel self-tuning layer for a recently intr o- ducedadaptive notch filtering algorithm. Analysis shows th at, under Gaussian random-walk type assumptions, the resultin g solution converges...
-
An improved frequency estimator for an adaptive active noise control scheme
PublicationAn improved frequency tracker is proposed for the recently introduced self optimizing narrowband interference canceller (SONIC). The scheme is designed for disturbances with quasi-linear frequency modulation and, under second-order Gaussian random-walk assumption, can be shown to be statistically efficient. One real-world experiment and several simulations show that a considerable improvement in disturbance rejection may be achieved...
-
Performance-Driven Surrogate Modeling of High-Frequency Structures
PublicationThe development of modern high-frequency structures, including microwave and antenna components, heavily relies on full-wave electromagnetic (EM) simulation models. Notwithstanding, EM-driven design entails considerable computational expenses. This is especially troublesome when solving tasks that require massive EM analyzes, parametric optimization and uncertainty quantification be-ing representative examples. The employment of...
-
Assessment of Supercapacitor’s Quality by Means of Low Frequency Noise
PublicationLow frequency noise is a well-known tool for quality and reliability assessment of electronic devices. This phenomenon is observed in different electrochemical devices as well (e.g., smart windows, electrochemical corrosion processes). Thus, we can assume that the same tool can be used to asses quality of supercapacitors. Their quality is usually determined only by capacitance and/or equivalent series resistance (ESR), or impedance....
-
Interictal high-frequency oscillations in focal human epilepsy
PublicationPURPOSE OF REVIEW: Localization of focal epileptic brain is critical for successful epilepsy surgery and focal brain stimulation. Despite significant progress, roughly half of all patients undergoing focal surgical resection, and most patients receiving focal electrical stimulation, are not seizure free. There is intense interest in high-frequency oscillations (HFOs) recorded with intracranial electroencephalography as potential...
-
Reliable data-driven modeling of high-frequency structures by means of nested kriging with enhanced design of experiments
PublicationData-driven (or approximation) surrogate models have been gaining popularity in many areas of engineering and science, including high-frequency electronics. They are attractive as a way of alleviating the difficulties pertinent to high computational cost of evaluating full-wave electromagnetic (EM) simulation models of microwave, antenna, and integrated photonic components and devices. Carrying out design tasks that involve massive...
-
Frequency based criterion for distinguishing tonal and noisy spectral components
PublicationA frequency-based criterion for distinguishing tonal and noisy spectral components is proposed. For considered spectral local maximum two instantaneous frequency estimates are determined and the difference between them is used in order to verify whether component is noisy or tonal. Since one of the estimators was invented specially for this application its properties are deeply examined. The proposed criterion is applied to the...
-
Statistically efficient smoothing algorithm for time-varying frequency estimation
PublicationThe problem of extraction/elimination of a nonstationary sinusoidal signal from noisy measurements is considered. This problem is usually solved using adaptive notch filtering (ANF) algorithms. It is shown that the accuracy of frequency estimates can be significantly increased if the results obtained from ANF are backward-time filtered by an appropriately designed lowpass filter. The resulting adaptive notch smoothing (ANS) algorithm...
-
Experimental and Numerical Analysis of Air Trapping in a Porous Medium with Coarse Textured Inclusions
PublicationThe paper presents a 2D upward infiltration experiment performed on a model porous medium consisting of fine sand background with two inclusions made of coarser sands. The purpose of the experiment was to investigate the effects of structural air trapping, which occurs during infiltration as a result of heterogeneous material structure. The experiment shows that a significant amount of air becomes trapped in each of the inclusions. Numerical...
-
Laboratory Load Model Based on 150 kVA Power Frequency Converter and Simulink Real-Time – Concept, mplementation, Experiments
PublicationFirst section of the paper provides technical specification of laboratory load model basing on 150 kVA power frequency converter and Simulink Real-Time platform. Assumptions, as well as control algorithm structure is presented. Theoretical considerations based on criteria which load types may be simulated using discussed laboratory setup, are described. As described model contains transformer with thyristor-controlled tap changer,...
-
Frequency-dependent coupling model for microwave band-pass filter
PublicationThe goal of this work was to create a circuit model which represents frequency-dependent coupling between microwave resonators. Our models are designed for in-line filters. The frequency-dependent coupling enables one to realize a transmission zero which is not possible in classical approach with frequency independent inverters. In addition, the proposed model allows us to observe out-of-band behavior, e.g. spurious resonance....
-
Frequency Guided Generalized Adaptive Notch Filtering - Tracking Analysis and Optimization
PublicationGeneralized adaptive notch filters (GANFs) are estimators of coefficients of quasi-periodically time-varying systems, encountered e.g., in RF applications when Doppler effect takes place. Current state of the art GANFs can deliver highly accurate estimates of system variations’ frequency, but underperform in terms of accuracy of system coefficient estimates. The paper proposes a novel multistage GANF with improved coefficient...
-
Influence of magnetic field on wear in high frequency reciprocatingsliding contacts
PublicationResults of experimental studies concerning the influence of permanent magnetic field on wear of dry sliding contact operating at short stroke and high frequency are presented. It was found that horizontal magnetic field with different orientations relative to the sliding direction is affecting performance of the contact. The increase in frequency of sliding reduces accumulated mass loss and lowers the surface roughness of the wear...
-
Chirp Rate and Instantaneous Frequency Estimation: Application to Recursive Vertical Synchrosqueezing
PublicationThis letter introduces new chirp rate and instantaneous frequency estimators designed for frequency-modulated signals. These estimators are first investigated from a deterministic point of view, then compared together in terms of statistical efficiency. They are also used to design new recursive versions of the vertically synchrosqueezed short-time Fourier transform, using a previously published method (D. Fourer, F. Auger, and...
-
Design and evaluation of a base module of active power electronic transformer
Publication -
Adaptacyjny regulator transformatora blokowego = Adaptive controller of generator transformer
PublicationW referacie przedstawiono koncepcję adaptacyjnego regulatora transformatora blokowego jako narzędzia do rozszerzenia ograniczeń generacji mocy biernej generatora synchronicznego.
-
Management of MV/LV Transformer Replacement Based on AMI Platform
PublicationThe paper presents the extended possibilities of managing the selection and replacement of MV/LV transformers using the measurement data from the Advanced Metering Infrastructure (AMI) system. The analysis was conducted on samples of over 1900 transformers that operate in two different types of MV grids: rural and urban. The analysis has shown that there is a great potential in the field of optimizing the rated power of the transformers.
-
High frequency oscillations in human memory and cognition: a neurophysiological substrate of engrams?
PublicationDespite advances in understanding the cellular and molecular processes underlying memory and cognition, and recent successful modulation of cognitive performance in brain disorders, the neurophysiological mechanisms remain underexplored. High frequency oscillations beyond the classic electroencephalogram spectrum have emerged as a potential neural correlate of fundamental cognitive processes. High frequency oscillations are detected...