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Search results for: STOCHASTIC WAVE REALIZATION
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Investigations of the Methods of Time Delay Measurement of Stochastic Signals Using Cross-correlation with the Hilbert Transform
PublicationThe article presents the results of simulation studies of four methods of estimating time delay for random signals using cross-correlation with the Hilbert Transform. Selected models of mutually delayed stochastic signals were used in the simulations, corresponding to the signals obtained from scintillation detectors in radioisotope measurements of liquid-gas two-phase flow. Standard deviations of the values of the individual functions...
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New Approach to Noncasual Identification of Nonstationary Stochastic FIR Systems Subject to Both Smooth and Abrupt Parameter Changes
PublicationIn this technical note, we consider the problem of finite-interval parameter smoothing for a class of nonstationary linear stochastic systems subject to both smooth and abrupt parameter changes. The proposed parallel estimation scheme combines the estimates yielded by several exponentially weighted basis function algorithms. The resulting smoother automatically adjusts its smoothing bandwidth to the type and rate of nonstationarity...
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Application of guided wave propagation in diagnostics of steel bridge components
PublicationEarly detection of potential defects and identification of their location are necessary to ensure safe, reliable and long-term use of engineering structures. Non-destructive diagnostic tests based on guided wave propagation are becoming more popular because of the possibility to inspect large areas during a single measurement with a small number of sensors. The aim of this study is the application of guided wave propagation in...
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Waves Along Fractal Coastlines: From Fractal Arithmetic to Wave Equations
PublicationBeginning with addition and multiplication intrinsic to a Koch-type curve, we formulate and solve wave equation describing wave propagation along a fractal coastline. As opposed to examples known from the literature, we do not replace the fractal by the continuum in which it is embedded. This seems to be the first example of a truly intrinsic description of wave propagation along a fractal curve. The theory is relativistically...
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An Efficient PEEC-Based Method for Full-Wave Analysis of Microstrip Structures
PublicationThis article introduces an efficient method for the equivalent circuit characterization and full-wave analysis of microstrip structures, leveraging the full-wave partial element equivalent circuit (PEEC). In particular, the multilayered Green's function is evaluated using the discrete complex-image method (DCIM) and employed to establish the mixed potential integral equations. The proposed strategy considers time delays for the...
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Theoretical Model of Acoustic Wave Propagation in Shallow Water
PublicationThe work is devoted to the propagation of low frequency waves in a shallow sea. As a source of acoustic waves, underwater disturbances generated by ships were adopted. A specific feature of the propagation of acoustic waves in shallow water is the proximity of boundaries of the limiting media characterised by different impedance properties, which affects the acoustic field coming from a source situated in the water layer “ deformed”...
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Numerical Study of Concrete Mesostructure Effect on Lamb Wave Propagation
PublicationThe article presents the results of the numerical investigation of Lamb wave propagation in concrete plates while taking into account the complex concrete mesostructure. Several concrete models with randomly distributed aggregates were generated with the use of the Monte Carlo method. The influence of aggregate ratio and particle size on dispersion curves representing Lamb wave modes was analyzed. The results obtained for heterogeneous...
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Simulation of Wave Propagation in Media Described by Fractional-Order Models
PublicationIn this paper, algorithms for simulation of the wave propagation in electromagnetic media described by fractional-order (FO) models (FOMs) are presented. Initially, fractional calculus and FO Maxwell's equations are introduced. The problem of the wave propagation is formulated for media described by FOMs. Then, algorithms for simulation of the non-monochromatic wave propagation are presented which employ computations in the time...
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Baseline-free debonding detection in reinforced concrete structures by elastic wave propagation
PublicationThe article presents the results of the numerical and experimental analysis concerning wave propagation in reinforced concrete (RC) beams with various extent of debonding between the steel rod and concrete cover. The main aim of the paper was to consider the unsolved research gaps, which considerably limit the application of wave-based methods in practice. The propagation of the flexural wave modes excited and registered on the...
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Stochastic approach to the dynamics of a linear floating object
PublicationArtykuł stanowi prezentację metody różniczkowych równań stochastycznych w zastosowaniu do analizy dynamiki obiektów pływających. Analizowany jest ruch jednostki pływającej jako obiektu liniowego z uwzględnieniem w równaniach stochastycznych nieliniowości, występującej w wymuszeniach zewnętrznych działających na obiekt. Stochastyczne równania różniczkowe są zapisane dla sprzężonych ruchów symetrycznych.
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Stochastic approach to the dynamics of marine floating object
PublicationAnalizowany jest ruch jednostki pływającej z uwzględnieniem w równaniach stochastycznych nieliniowości, występującej w wymuszeniach zewnętrznych działających na obiekt. Stochastyczne równania różniczkowe są zapisane dla sprzężonych ruchów symetrycznych.
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Stochastic model of the process of diesel engine operation.
PublicationStreszczenie: Najistotniejszym problemem eksploatacji silników o zapłonie samoczynnym jest problem racjonalnego (a zwłaszcza optymalnego) sterowania procesem eksploatacji tych silników. Sterowanie takie może ułatwić zastosowanie iteracyjnego algorytmu wyznaczania optymalnych strategii opracowanego przez R.A. Howarda. Wykorzystanie jednak tego algorytmu do sterowania procesem eksploatacji silników wymaga między innymi opracowania...
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Approximation of Covariance Function with Application to Stochastic Mechanics.
PublicationW pracy przedstawiono koncepcję rozwinięć kanonicznych dla funkcji losowych oraz możliwość ich zastosowania w stochastycznej mechanice gruntów. Rozpatrzono rozkład widmowy, rozwinięcia Karhunena-Loevego oraz rozwinięcia ortogonalne zmodyfikowanymi wielomianami Hermite'a. Przeprowadzono analizę błędów dla zagadnienia warstwy gruntu o losowych parametrach sprężystych, uzyskano analityczne rozwiązanie systemu stochastycznego.
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Limit Analysis of a Strip Footing on Stochastic Subsoil.
PublicationW pracy analizowana jest ława fundamentowa posadowiona na losowym podłożu.Poszukiwane są oszacowania nośności podłoża na podstawie twierdzeń o dolnej i górnej ocenie obciążenia granicznego. Dla różnych statycznie dopuszczalnych pól naprężenia i kinematycznie dopuszczalnych pól prędkości, wyznaczono wartości oczekiwane i wariancje obciążenia granicznego. Pozwoliło to na określenie odpowiednich dystrybuant, rozumianych...
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IEEE Microwave and Guided Wave Letters
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Damage localisation in a stiffened plate structure using a propagating wave
PublicationThe paper presents an application of changes in propagating waves for damage detection in a stiffened aluminium plate. The experimental investigation was conducted on an aluminium plate with riveted two L-shape stiffeners. The wave has been excited with a piezoelectric transducer and measured with the Laser Scanning Doppler Vibrometer. Recorded signals were analysed using the special signal processing techniques developed for damage...
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Simulations of wave propagation and attenuation in fields of colliding ice floes
Open Research DataThis dataset contains results of numerical smulations of sea ice-wave interactions, corresponding to laboratory experiments conducted at the Large Ice Model Basin (LIMB) at the Hamburg Ship Model Basin (HSVA) as part of the LS-WICE ("Loads on Structure and Waves in Ice"; https://zenodo.org/record/1067170#.XrLt_dhpxhE) project. THe simulations were conducted...
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FPGA realization of high-speed multi-stage FIR filter in residue arithmetic
PublicationW pracy przedstawiono implementację szybkiego wielostopniowego, kaskadowego filtru FIR w technologii FPGA. Zastosowanie arytmetyki resztowej pozwala na uzyskanie dużych częstotliwości próbkowania w zwiżaku z użyciem małych mnożników. Zalety wynikające z uzycia arytmetyki resztowej sa w pewnym stopniu ograniczne koniecznością wykonania skalowania przy kaskadowym połaczeniu filtrów FIR, tak aby uniknąć nadmiaru arytmetycznego. W...
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Non-destructive inspection of ground anchors using guided wave propagation
PublicationThis paper deals with numerical and experimental investigations of specific problems of guided wave propagation in ground anchors. The research focuses on recognizing the phenomenon of the energy transfer between anchor components. Particular attention is paid to characteristic features of guided waves propagating in free and embedded parts of the tendon, at the interface between the tendon and the surrounding anchor body as well...
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Nonlinear Excitation of the Non-Wave Perturbations by the Magnetoacoustic Waves in the Non-Isentropic Plasma
PublicationNonlinear excitation of slow modes by the planar magnetosonic perturbations in a plasma is discussed. Plasma is an open system due to radiation and external heating. This may stipulate enhancement of wave perturbations and hence the acoustical activity of plasma. Plasma is assumed to be a homogeneous ideal gas with infinite electrical conductivity. The straight magnetic field is orthogonal to the velocity of fluid’s...
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Fast Full-Wave Multilevel Zero-Pole Optimization of Microwave Filters
PublicationA new concept is proposed for the full-wave computer-aided design of microwave filters. The method consists of two stages and operates on the zeros and poles of the transfer function and their derivatives. These quantities are evaluated from the response computed by a full-wave electromagnetic solver with two levels of accuracy. The two stages make use of different models that are optimized using a low-accuracy electromagnetic...
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Elastic wave propapagation in diagnostics of self-drilling system of grouted anchors
PublicationThe paper presents an experimental investigation of elastic wave propagation in a self-drilling hollow bar system, which is commonly used in geotechnical industry as the element of grouted ground anchors and soil nails. The single self-drilling hollow bar and self-drilling system of two bars connected by a coupler were considered. Longitudinal waves were excited at one end of the bar and registered at both ends, by means of PZT...
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Wave propagation signals for ultrasonic tomography of concrete during splitting
Open Research DataThe DataSet contains the results of the mechanical behaviour of a concrete cube with dimensions 70 x 70 x 70 cm3under the splitting test. Three cubes were tested: cube 1 (concrete with polymer fibres), cube 2 (concrete with steel fibres) and cube 3 (plain concrete).
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Millimeter Wave Negative Refractive Index Metamaterial Antenna Array
PublicationIn this paper, a novel negative refractive index metamaterial (NIM) is developed and characterized. The proposed metamaterial exhibits negative effective permittivity (εeffe) and negative effective permeability (µeffe) at millimeter wave frequency of 28GHz. This attractive feature is utilized to enhance the gain of a microstrip patch antenna (MPA). Two thin layers of 5 5 subwavelength unit cell array of NIM are placed above a...
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Investigation of Continuous Wave Jamming in an IEEE 802.15.4 Network
PublicationThis paper presents how continuous wave jamming affects IEEE 802.15.4 network. To this end, an office-based measurement setup has been proposed. Within the measurement area, 25 nodes have been set up in order to create a IEEE 802.15.4 tree-based test network structure. A dedicated jamming device that generates and transmits a continuous wave signal has been developed. Several tests have been conducted and presented to demonstrate...
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Preload monitoring in a bolted joint using Lamb wave energy
PublicationThe knowledge of the load in prestressed bolted connections is essential for the proper operation and safety of engineering structures. Recently, bolted joints have become an area of intensive research associated with non-destructive diagnostics, in particular in the context of wave propagation techniques. In this paper, a novel procedure of bolt load estimation based on the energy of Lamb wave signals was proposed. Experimental...
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Field-induced suppression of charge density wave in GdNiC2
PublicationWe report the specific heat, magnetic, magnetotransport, and galvanomagnetic properties of polycrystalline GdNiC 2 . In the intermediate temperature region above T N = 20 K, we observe large negative magnetoresistance due to Zeeman splitting of the electronic bands and partial destruction of a charge density wave ground state. Our magnetoresistance and Hall measurements show that at low temperatures a magnetic field-induced transformation from...
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A higher order shell element for wave propagation in isotropic shell structures
PublicationThe presents the new multi mode higher order shell element for wave propagation problems in shell structures.
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Charge density wave and large nonsaturating magnetoresistance in YNiC2 and LuNiC2
PublicationWe report a study of physical properties of two quasi-low-dimensional metals YNiC2 and LuNiC2 including the investigation of transport, magnetotransport, galvanomagnetic, and specific heat properties. In YNiC2 we reveal two subsequent transitions associated with the formation of weakly coupled charge density wave at TCDW=318K and its locking in with the lattice at T1=275K. These characteristic temperatures follow the previously...
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Jumping Wave Characteristic during Low Plasticity Burnishing Process
PublicationDuring the low plasticity burnishing process of soft materials such as carbon steel with a hardness of up to 40 HRC (Rockwell grade) a raised structure of the material known as the Jumping Wave forms in front of the tool roll. This phenomenon significantly disturbs the burnishing process, but is very poorly described in the literature. This article presents studies of this phenomenon on the example of burnished 1.0562 steel. The...
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DETECTION OF DEBONDING IN STEEL BARS EMBEDDED IN CONCRETE USING GUIDED WAVE PROPAGATION
PublicationThe paper presents a non-destructive diagnostic technique based on guided wave propagation phenomenon used to assess the adhesive bonding between a steel bar and a concrete cover. Double-layered cylindrical specimens with different levels of debonding and its location were investigated. The influence of bonding length on the excitation of multiple modes of longitudinal guided waves was analysed. Numerical simulations of guided...
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Spectral Methods for Modelling of Wave Propagation in Structures in Terms of Damage Detection—A Review
PublicationModern methods of detection and identification of structural damage direct the activities of scientific groups towards the improvement of diagnostic methods using for example the phenomenon of mechanical wave propagation. Damage detection methods that use mechanical wave propagation in structural components are extremely effective. Many different numerical approaches are used to model this phenomenon, but, due to their universal...
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Robust-adaptive dynamic programming-based time-delay control of autonomous ships under stochastic disturbances using an actor-critic learning algorithm
PublicationThis paper proposes a hybrid robust-adaptive learning-based control scheme based on Approximate Dynamic Programming (ADP) for the tracking control of autonomous ship maneuvering. We adopt a Time-Delay Control (TDC) approach, which is known as a simple, practical, model free and roughly robust strategy, combined with an Actor-Critic Approximate Dynamic Programming (ACADP) algorithm as an adaptive part in the proposed hybrid control...
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Lamb wave propagation in a single lap adhesive joint
PublicationThe aim of the paper is the analysis of Lamb wave propagation in adhesive joints. The research was performed on a single lap adhesive joint of two steel plates. Two types of joints, namely an intact and with defect were considered. In experimental investigations the condition assessment of the joint was performed with the use of antisymmetric Lamb waves excited by a plate piezo actuators and measured by a laser vibrometer. Numeri-cal...
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Nondestructive corrosion degradation assessment based on asymmetry of guided wave propagation field
PublicationThe article presents the results of numerical and experimental investigation of guided wave propagation in steel plates subjected to corrosion degradation. The development of novel procedures allowing for the assessment of the corrosion degradation level is crucial in the effective diagnostics of offshore and ship structures that are especially subjected to aggressive environments. The study’s main aim is to investigate the influence...
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High-Resolution Wind Wave Parameters in the Area of the Gulf of Gdańsk During 21 Extreme Storms
PublicationThis dataset contains the results of wind-wave parameter modelling in the area of the Gulf of Gdańsk (Southern Baltic). For the simulations, a high resolution SWAN model was used. The dataset consists of the significant wave height, the direction of the wave approaching the shore and the wave period during 21 historical, extreme storms. The storms were selected by an automatic search over the 44-year-long significant wave height...
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Damage Imaging in Lamb Wave-Based Inspection of Adhesive Joints
PublicationAdhesive bonding has become increasingly important in many industries. Non-destructive inspection of adhesive joints is essential for the condition assessment and maintenance of a structure containing such joints. The aim of this paper was the experimental investigation of the damage identification of a single lap adhesive joint of metal plate-like structures. Nine joints with different defects in the form of partial debonding...
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Modelling of Longitudinal Elastic Wave Propagation in a Steel Rod Using the Discrete Element Method
PublicationThe paper deals with the issue of modelling elastic wave propagation using the discrete element method (DEM). The case of a longitudinal wave in a rod with a circular cross-section was considered. A novel, complex algorithm consisting of the preparation of models and simulation of elastic waves was developed. A series of DEM models were prepared for simulations, differing in discretisation and material parameters. Additional calculations...
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Wave transmission across surface interfaces in lattice structures
PublicationWithin the lattice dynamics formulation, we present an exact solution for anti-plane surface waves in a square lattice strip with a surface row of material particles of two types separated by a linear interface. The considered problem is a discrete analog of an elastic half-space with surface stresses modelled through the simplified Gurtin–Murdoch model, where we have an interfacial line separating areas with different surface...
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Design of an Autonomous IoT Node Powered by a Perovskite-Based Wave Energy Converter
PublicationThis paper presents the results of experimental research focused on wave energy harvesting and its conversion to power Internet of Things (IoT) devices. The harvesting and conversion process was performed using a wave energy converter (WEC) consisting of a lead zirconate titanate piezoelectric ceramic perovskite material and a prototype power electronic circuit. The designed WEC was considered as a power supply for an end node...
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System setup and software for cyclic, staircase and square wave voltammetry measurements
PublicationHardware dedicated for electrochemical measurement sometimes does not allow performing certain voltammetry experiments. Staircase and square wave voltammetry, techniques which have many advantages comparing with standard voltammetric techniques, are rarely implemented in software controlling electrochemical measuring equipment. These methods, however, can be relatively easy realized with some addition...
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High-resolution wind wave parameters in the area of the Gulf of Gdańsk during 21 extreme storms
Open Research DataThis dataset contains the results of wind-wave parameter modelling in the area of the Gulf of Gdańsk (Southern Baltic). For the simulations, a high resolution SWAN model was used. The dataset consists of the significant wave height, the direction of the wave approaching the shore and the wave period during 21 historical, extreme storms. The storms were...
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A stochastic approach for the solution of single and multi – objective optimisation problems of biological processes in sequencing batch reactor
PublicationThis paper investigates the impact of implementing single and multi-optimisation solutions on the biological treatment process in a sequencing batch reactor (SBR). The research is based on a case study of the water resource recovery facility (WRRF) in Swarzewo, Northern Poland. The paper introduces the adaptive extremum seeking control (ESC) method for dissolved oxygen (DO) concentration control and places it in a layered control structure....
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Radix-4 dft butterfly realization with the use of the modified quadratic residue number system
PublicationW pracy zaprezentowano projektowanie i realizację obliczenia motylkowego dft dla podstawy 4 z użyciem zespolonego systemu resztowego (CRNS) i zmodyfikowanego kwadratowego systemu resztowego (MQRNS). System MQRNS oprócz własności dekompozycyjnych pozwala na realizację mnożenia zespolonego przy zastosowaniu trzech mnożeń rzeczywistych. Przedstawiono konwertery wejściowy CRNS/MQRNS i wyjściowy MQRNS/CRNS, mnożenie zespolone w MQRNS,...
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Radix-4 dft butterfly realization with the use of the modified quadratic residue number system
PublicationW pracy przedstawiono algorytm realizacji mnożenia zespolonego z użyciem zmodyfikowanego kwadratowego zmodyfikowanego systemu liczbowego (mqrns) oraz jego zastosowanie do wykonania obliczenia motylkowego dft dla podstawy 4. pokazano też wstępne rezultaty implementacji w układzie xilinx fpga.
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FPGA realization of the high-speed residue-to-binary converter based on chinese remainder theorem
PublicationW pracy przedstawiono architekturę, realizację FPGA oraz symulację numeryczną na poziomie bitowym szybkiego konwertera z systemu resztowego do systemu binarnego dla modułów 5-bitowych opartego na chińskim twierdzeniu o resztach. Algorytm konwertera obejmuje obliczanie projekcji ortogonalnych poprzez odczyt pamięci oraz sumowanie modulo M realizowane dwustopniowo, pierwszy stopień oparty o sumatory CSA umożliwia redukcję do zakresu...
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FPGA realization of the high-speed residue-to-binary converter based on the Chinese Remainder Theorem
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A stochastic approach to the problem of bearing capacity by the method of characteristics
PublicationW pracy omówiono zagadnienie nośności granicznej podłoża o własnościach losowych, przy obciążeniu od spoczywającego na nim fundamentu. Zaproponowano stochastyczną modyfikację metody charakterystyk bazującej na metodzie różnic skończonych. Analizowano zagadnienia związane z dyskretyzacją losowego ośrodka gruntowego, symulacją pola losowego oraz ze zbieżnością i stabilnością rozwiązania. Przedstawione podejście umożliwiło uwzględnienie...
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ENHANCED EVAPORATION OF THE DROPLETS OF CONDENSATE IN THE ASYMMETRICAL SHOCK WAVE ZONE
PublicationIn the low-pressure part of steam turbine, the state path usually crosses the saturation line in penultimate stages [4,5]. The formation and evolution of these droplets lower the performance of the wet stages of the turbines, and their effects on the efficiency are collectively known as wetness losses [4]. Nowadays, due to work of steam turbines at partial load, process of homogeneous and heterogeneous condensation still is current....
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Application of the ISE Optimized Proportional Control of the Wave Maker in a Towing Tank
PublicationThis paper presents the improvement of the wave maker control system. The wave maker is a facility widely used in hydromechanics laboratories to generate waves in towing tanks. It is equipped with an electrohydraulic drive and an actuator submerged into water. The waves are generated to model the environmental conditions for physical experiments, performed on reduced-scale models of maritime objects. The physical experiments allow...