Filters
total: 2801
filtered: 2512
displaying 1000 best results Help
Search results for: UNSTEADY FRICTION
-
Dynamic Charging of Electric Buses as a Way to Reduce Investment Risks of Urban Transport System Electrification
PublicationNight charging and fast charging are currently the two most common systems for charging electric buses. Despite the fact that numerous trial installations were started, neither of these two systems has obtained unqualified approval of the users. The alternative is to charge vehicles in motion - dynamic charging which combines the advantages of trolleybus transport and of electric buses. One of the advantages is the reduction of...
-
Global Complex Roots and Poles Finding Algorithm Based on Phase Analysis for Propagation and Radiation Problems
PublicationA flexible and effective algorithm for complex roots and poles finding is presented. A wide class of analytic functions can be analyzed, and any arbitrarily shaped search region can be considered. The method is very simple and intuitive. It is based on sampling a function at the nodes of a regular mesh, and on the analysis of the function phase. As a result, a set of candidate regions is created and then the roots/poles are verified...
-
Shape Optimisation of Kaplan Turbine Blades Using Genetic Algorithms
PublicationThis monograph is a comprehensive guide to a method of blade profile optimisation for Kaplan-type turbines. This method is based on modelling the interaction between rotor and stator blades. Additionally, the shape of the draft tube is investigated. The influence of the periodic boundary condition vs. full geometry is also discussed. Evolutionary algorithms (EA) are used as an optimisation method together with artificial neural...
-
Modelowanie bezpiecznika rozłącznikowego w układach formowania impulsów wielkiej mocy
PublicationProblem modelowania bezpieczników o dużej dynamice wyłączania prądu jest zagadnieniem szeroko opisywanym w literaturze. Układy takie mogą być wykorzystane w szczególności do formowania impulsów wysokiego napięcia o wartościach rzędu setek kV, charakteryzujących się czasem trwania rzędu ułamka μs. W niniejszej pracy przedstawiono empiryczny model bezpiecznika wielotopikowego, rozszerzony w oparciu o wyniki badań eksperymentalnych.
-
Accumulation of volatile constituents in agar and bioreactor shoot cultures of Verbena officinalis L.
PublicationIn vitro shoot cultures of common vervain (Verbena officinalis L., Verbenaceae) were established and evaluated for essential oil content. The shoots were maintained as stationary microshoot culture, grown on Schenk–Hildebrandt medium supplemented with 9.84 µM of 2-isopentenyladenine and 1.0 µM of thidiazuron. The shoots were further adapted to grow in two temporary immersion bioreactors (RITA and Plantform), using Schenk–Hildebrandt...
-
Distinction of citrus fruits based on their volatile composition using the electronic nose
PublicationThe aim of the study was to analyze the volatile fraction of the citrus fruit using an electronic nose device integrated with ultrafast gas chromatography. The subjects were Citrus aurantifolia, Fortunella margarita Swingle and Citrus × floridana. The chromatographic data obtained were analyzed by means of chemometric methods: PCA and SQC. On the basis of the charts obtained, it is possible to distinguish the fruits tested on the...
-
Curlicues generated by circle homeomorphisms
PublicationWe investigate the curves in the complex plane which are generated by sequences of real numbers being the lifts of the points on the orbit of an orientation preserving circle homeomorphism. Geometrical properties of these curves such as boundedness, superficiality, local discrete radius of curvature are linked with dynamical properties of the circle homeomorphism which generates them: rotation number and its continued fraction...
-
Evolutionary Sets of Safe Ship Trajectories: Evaluation of Individuals
PublicationThe paper presents a description of the evaluation phase of the Evolutionary Sets of Safe Ship Trajectories method. In general, the Evolutionary Sets of Safe Ship Trajectories method combines some of the assumptions of game theory with evolutionary programming and finds an optimal set of cooperating trajectories of all ships involved in an encounter situation. While developing a new version of this method, the au-thors decided...
-
The Hybrid Fuzzy - SOEKS Approach to the Polish Internet Mortgage Market
PublicationThe paper presents the hybrid fuzzy- SOEKS approach to the Polish Internet mortgage market, which is treated as an example of a fast changing market. Firstly, the market and market problems are described. Then, the first approach to the market problems is presented: the complete fuzzy model which was built basing on the rules. The fuzzy model is presented on one real data case. Next, the new approach, called Set of Experience Knowledge...
-
The Effect of Water and Frost on Fatigue Life of Asphalt Concrete
PublicationThis paper presents testing of fatigue life of asphalt concrete that has been subjected to action of water and frost. Simulation of water and frost action was based on the original AASHTO T283 method and its modification. The original method was modified in such a way that instead of a single freeze-thaw cycle, 50 and 150 cycles were applied. Fatigue life was measured in the indirect tensile fatigue test in the Nottingham asphalt...
-
TOWARDS EXPLAINABLE CLASSIFIERS USING THE COUNTERFACTUAL APPROACH - GLOBAL EXPLANATIONS FOR DISCOVERING BIAS IN DATA
PublicationThe paper proposes summarized attribution-based post-hoc explanations for the detection and identification of bias in data. A global explanation is proposed, and a step-by-step framework on how to detect and test bias is introduced. Since removing unwanted bias is often a complicated and tremendous task, it is automatically inserted, instead. Then, the bias is evaluated with the proposed counterfactual approach. The obtained results...
-
Influence of local bush wear on water lubricated sliding bearing load carrying capacity
PublicationOne of main problems concerning water-lubricated bearings is their durability. There are known cases of bearings with life time measured in decades, and some, whose refurbishment was necessary just days after start-up. Obtaining stable fluid film friction plays key role in the durability of these bearings. Unfortunately, their load-carrying capacity is limited due to water's low-viscosity. The conducted experimental...
-
Prospects of Decreasing Power Losses in a Hydrostatic Thrust Bearing
PublicationIn numerous machines, axial load is carried by tilting pad thrust bearings known since the beginning of 20th century. These bearings are commonly bath lubricated, which is simple, does not require any additional pumps, and, due to this, such systems are highly reliable. In a contemporary technology, however, minimization of friction losses became an important goal of machinery improvement. Calculations based on elementary rules...
-
Enhanced energy conversion as a result of fluid-solid interaction in micro- and nanoscale
PublicationIt is known that nano- and micromechanics require new approaches to right describing of surface-like phenomena which lead to an enhanced energy conversion. In this work, a general form of surface forces that consist of a contribution from both the friction and mobility components has been extended to collect the effects of bulk and surface motion of a fluid. Quite similar impact can be observed for a solid-fluid mixture, where...
-
A comparative performance assessment of a hydrodynamic journal bearing lubricated with oil and magnetorheological fluid
PublicationThis work presents the investigation results of a journal bearing lubricated with magnetorheological fluid that is activated by a local constant magnetic field to vary both the local flow resistance and pressure. The bearing performance is assessed via Finite Element Modelling (FEM) and results are corroborated by experiments. The FEM model uses the Bingham model to describe the fluid film. A dedicated test rig is used to assess...
-
Experimental study of the multi-disc negative brake for a hydraulic motor
PublicationThis paper describes the methodology for experimental testing of a multi-disc brake. The construction of this brake was also present. The brake is dedicated to hydraulic motors with a small working volume. Experimental tests were carried out on a brake with plates immersed in oil and, for comparison, tests were carried out on a dry brake. As a result of the tests, the permissible torque (load) that is able to transfer the brake...
-
Second-order Stark effect and polarizability of a relativistic two-dimensional hydrogenlike atom in the ground state
PublicationThe second-order Stark effect for a planar Dirac one-electron atom in the ground state is analyzed within the framework of the Rayleigh-Schrödinger perturbation theory, with the use of the Sturmian series expansion of the generalized Dirac-Coulomb Green's function. A closed-form analytical expression for the static dipole polarizability of that system is found. The formula involves the generalized hypergeometric function ${}_{3}F_{2}$...
-
Simulation of the remanence influence on the transient states in a single-phase multiwinding transformer
PublicationThis paper presents the mathematical model of a single-phase multi-winding core type transformer taking into account magnetic hysteresis phenomenon based on the feedback Preisach model (FPM). The set of loop differential equations was developed for a K-th winding transformer model where the flux linkages of each winding includes flux Φ common to all windings as a function of magneto motive force Θ of all windings. The first purpose...
-
PRZESTRZEŃ PUBLICZNA MIASTA EUROPEJSKIEGO– SALON MIEJSKI CZY ISTOTNY ELEMENT BUDOWYPROGRAMU REWITALIZACJI? PRZYKŁAD MQW WIEDNIUEUROPEAN PUBLIC SPACE – SHOWROOM ORAN IMPORTANT ELEMENT OF REVITALIZATIONPROGRAMME?
PublicationPrzedmiotem artykułu jest próba odpowiedzi na pytanie, jakie miejsce weuropejskich programach rewitalizacji zajmuje obecnie przestrzeń publiczna iczy istotnie jest jego główną składową. Czy miejskość przestrzenipublicznej, która jest jakością miejsc niezwykłych, łączących w sobie kontekst polityczny wswojej materialnej formie tzw.material urbanity[2, s. 24]) jest brana pod uwagę przy programach rewitalizacji?! Czy wreszcie,mówiąc...
-
A high-accuracy method of computation of x-ray waves propagation through an optical system consisting of many lenses
PublicationThe propagation of X-ray waves through an optical system consisting of many X-ray refractive lenses is considered. Two differential equations are contemplated for solving the problem for electromagnetic wave propagation: first – an equation for the electric field, second – an equation derived for a complex phase of an electric field. Both equations are solved by the use of a finite-difference method. The simulation error is estimated...
-
Impact of rotor geometry optimization on the off-design ORC turbine performance
PublicationThe paper describes the method of CFD based Nelder-Mead optimization of a 10 kW single-stage axial turbine operating in an ORC system working on R7100. The total-to-static isentropic efficiency is defined as an objective function. Multi-point linear regression is carried out to determine the significance of the objective function arguments and to pick up the set of particular variables and characteristic quantities (e.g. flow angles)...
-
SFEM Analysis of Beams with Scaled Lengths including Spatially Varying and Cross-Correlated Concrete Properties
PublicationThis paper presents the results obtained for plain concrete beams under four-point bending with spatially varying material properties. Beams of increasing length but constant depth were analyzed using the stochastic finite element method. Spatial fluctuation of a uniaxial tensile strength, fracture energy and elastic modulus was defined within cross-correlated random fields. The symmetrical Gauss probability distribution function...
-
Cross-linked epoxy-isocyanate blends containing Epidian-6 modified by glycols
PublicationPolymeric films of cross-linked structure may be formed using epoxy-isocyanate blends composed of Epidian-5 epoxy resin, 4,4’-diphenylmethanediisocyanate (MDI), Z-1 polyamine hardener and Epidian-6 epoxy resin modified by glycols. The effect of the component natures and ratio, process temperature and time on the gel-fraction content, as well as film hardness, was examined. The chemistry of the film forming process was determined...
-
Secondary emission influenced fluorescence decay of a homogeneous fluorophore solution
PublicationAn analytical expression is found allowing the calculation of the secondary emission influenced fluorescence decay of a homogeneous fluorophore solution. Before starting the calculation one has to know the shape of the primary fluorescence decay of the fluorophore and the value of the parameter kappa denoting the ratio of the secondary to primary steady-state fluorescence intensities. The method elaborated by Budo and Ketskemety...
-
Representation of magnetic hysteresis in tape wound core using feedback Preisach model
PublicationThis paper presents a mathematical model for the hysteresis phenomenon in ferromagnetic tape wound core. The feedback scalar Preisach model of hysteresis is used to simulate magnetic behavior of the grain oriented silicon strip of ET114-27 type. Determination of B-H hysteretic curve is based on measurement of the initial magnetization curve and the main hysteresis loop. The Preisach distribution function (PDF) of ET114-27 material...
-
Arm EMG Wavelet-Based Denoising System
PublicationThese paper presents research results of muscle EMG signal denoising. In the same time two muscles were examined - an adductor muscle (biceps brachii) and an abductor muscle (tricpeps brachii). The EMG signal was filtered using the wavelet transform technique, having selected the crucial parameters as: wavelet basis function (Daubechies 4), 10 th decomposition level, threshold selection algorithm (Heurestic) and a sln rescaling...
-
Acceleration of the DGF-FDTD method on GPU using the CUDA technology
PublicationWe present a parallel implementation of the discrete Green's function formulation of the finite-difference time-domain (DGF-FDTD) method on a graphics processing unit (GPU). The compute unified device architecture (CUDA) parallel computing platform is applied in the developed implementation. For the sake of example, arrays of Yagi-Uda antennas were simulated with the use of DGF-FDTD on GPU. The efficiency of parallel computations...
-
Multi-objective weather routing of sailboats considering wave resistance
PublicationThe article presents a method to determine the route of a sailing vessel with the aid of deterministic algorithms. The method assumes that the area in which the route is to be determined is limited and the basic input data comprise the wind vector and the speed characteristic of the vessel. Compared to previous works of the authors, the present article additionally takes into account the effect of sea waves with the resultant resistance...
-
Efficient Fabry-Perot Open Resonator Analysis by the use of a Scattering Matrix Method
PublicationIn this paper a comparative study of the computational efficiency of two modeling methods applied to the analysis of the plano- and double-concave Fabry-Perot open resonators is presented. In both numerical approaches, a scattering matrix method was applied, which allows splitting the analysis of the resonator into several sections, including the one with a spherical mirror, which requires the largest computing resources. Two modeling...
-
New Screening Protocol for Effective Green Solvents Selection of Benzamide, Salicylamide and Ethenzamide
PublicationNew protocol for screening efficient and environmentally friendly solvents was proposed and experimentally verified. The guidance for solvent selection comes from computed solubility via COSMO-RS approach. Furthermore, solute-solvent affinities computed using advanced quantum chemistry level were used as a rationale for observed solvents ranking. The screening protocol pointed out that 4-formylomorpholine (4FM) is an attractive...
-
A solution of non-linear differential problem with application to selected geotechnical problems
PublicationA certain non-linear differential equation containing a power of unknown function being the solution is considered with application to selected geotechnical problems. The equation can be derived to a linear differential equation by a proper substitution and properties of the operations G and S.
-
Testing Stability of Digital Filters Using Optimization Methods with Phase Analysis
PublicationIn this paper, novel methods for the evaluation of digital-filter stability are investigated. The methods are based on phase analysis of a complex function in the characteristic equation of a digital filter. It allows for evaluating stability when a characteristic equation is not based on a polynomial. The operation of these methods relies on sampling the unit circle on the complex plane and extracting the phase quadrant of a function...
-
Epoxy Composites Filled with Natural Calcium Carbonate. 1. Epoxy Composites Obtained in the Presence of Monoperoxy Derivative of Epidian-6 Epoxy Resin
PublicationPhysico-mechanical properties of the products based on filled epoxy-oligomeric mixtures composed of Epidian-5 epoxy resin, oligoesteracrylate TGM-3 and monoperoxide derivative of Epidian-6 epoxy resin (PO) have been investigated. CaCO3 was used as a filler and polyethylene polyamine was a curing agent. The effect of PO and CaCO3 on the gel-fraction content and physico-mechanical properties was examined. Using a scanning electron...
-
The Usage of the BP-Layers Stereo Matching Algorithm with the EBCA Camera Set
PublicationThis paper is concerned with applying a stereo matching algorithm called BP-Layers to a set of many cameras. BP Layers is designed for obtaining disparity maps from stereo cameras. The algorithm takes advantage of convolutional natural networks. This paper presents using this algorithm with a set called Equal Baseline Camera Array. This set consists of up to five cameras with one central camera and other ones aground it. Such a...
-
INFLUENCE OF A VERTEX REMOVING ON THE CONNECTED DOMINATION NUMBER – APPLICATION TO AD-HOC WIRELESS NETWORKS
PublicationA minimum connected dominating set (MCDS) can be used as virtual backbone in ad-hoc wireless networks for efficient routing and broadcasting tasks. To find the MCDS is an NP- complete problem even in unit disk graphs. Many suboptimal algorithms are reported in the literature to find the MCDS using local information instead to use global network knowledge, achieving an important reduction in complexity. Since a wireless network...
-
Calixthioamides as ionophores for transition and heavy-metal cations
PublicationThere is an increasing interest in applying p-tert-butylcalix[4]arenes as sensing materials in ion-selective electrodes(ISEs). Considerable efforts were made to design calixarenes that are selective for some heavy- or transitionmetal ions to be used in ISEs for controlling and monitoring the level of such pollutants in the environment. It has been reported that introduction of softer sulfur atoms instead of oxygen atoms in calix[4]arene...
-
Pylon foundation of a cable stayed bridge at the motorway ring road of Wrocław
PublicationThe largest bridge of the motorway ring road of Wroclaw is a cable stayed bridge over the Odra river near Rędzin. Due to hydrogeological conditions of the ground it was not convenient to use standard bored piles of high length. Instead shorter piles were applied with additional improvement by cement injections at the pile toes. This decision was possible by extending ground investigation program and application of numerical modeling...
-
The distributed model predictive controller for the nuclear power plant turbo-generator set
PublicationTypically there are two main control loops with PI controllers operating at each turbo-generator set. In this paper a distributed model predictive controller DMPC, with local QDMC controllers for the turbine generator, is proposed instead of a typical PI controllers. The local QDMC controllers utilize step-response models for the controlled system components. These models parameters are determined based on the proposed black-box...
-
Performance of the flat plate solar collector operated with water-Al2O3 nanofluid
PublicationThe paper discusses the effect of application of water-Al2O3 nanofluid, as a working fluid, on the efficiency of a flat plate solar collector. The mass concentration of nanoparticles was 0.1%, 0.2% and 0.4%. The tests were conducted for two values of radiation of about 1050 W/m2 and 400 W/m2, and volume flow rates of 60 l/h, 120 l/h and 170 l/h. The efficiency was calculated according to recommendations of the Polish Standard....
-
A new approach to cross-bonding in medium voltage cable lines
PublicationThe medium voltage underground cable sheaths are usually bonded and earthed in every substation on the cable route. This results in additional power losses in the sheaths. The paper presents an idea of reducing power losses caused by sheaths cross-bonding. The idea of sheaths cross-connecting only in selected MV/LV substations is given instead of a typical solution, where sheaths cross-bonding requires installing additional joints...
-
Robustness Analysis of a Distributed MPC Control System of a Turbo-Generator Set of a Nuclear Plant – Disturbance Issues
PublicationTypically, there are two main control loops with PI controllers operating at each turbo-generator set. In this paper, a distributed model predictive controller with local quadratic model predictive controllers for the turbine generator is proposed instead of a set of classical PI controllers. The local quadratic predictive controllers utilize step-response models for the controlled system components. The parameters of these models...
-
Analiza i ocena smarności olejów w ujęciu energetycznym i działania układu tribologicznego = Analysis and evaluation of oil lubricity from the viewpoint of energy apects and of the tribological system action
PublicationBased on measurement results, an interpretation is presented of the tribological system boundary layer action in the form of a four-ball tester friction node. The evaluation was performed of the boundary layer action understood as transfer of energy Ep resulting from loading the tribological system in a determined time t with work Lp, which may lead to breaking the boundary layer. That energy and time are the values unequivocally...
-
Fracture mechanics model of cutting power versus widespread regression equations while wood sawing with circular saw blades
PublicationA comparison of the theoretical cutting power consumption results forecasted with the model (FM_CM model) which include work of separation (fracture toughness) in addition to plasticity and friction, and two widespread regression equations while wood sawing with circular saw blades has been described. in and cutting power consumption forecasted. In computations of the cutting power consumption during rip sawing of Scots pine wood...
-
Empirical verification in industrial conditions of fracture mechanics models of cutting power prediction
PublicationA comparison of experimental results obtained in the industrial conditions at a sawmill located in the Baltic Natural Forest Region (PL) and theoretical cutting power consumption forecasted with the models which include work of separation (fracture toughness) in addition to plasticity and friction has been described. In computations of cutting power consumption during rip sawing of Scots pine wood (Pinus sylvestris L.) values of...
-
Maximum transportation growth in energy and solute particles in Prandtl martial across a vertical 3D-heated surface: Simulations achieved using by finite element approach
PublicationThe goal of this study is to determine the maximum energy and solute particles' transportation growth in a 3D-heated region of Prandtl martial through a dynamic magnetic field. The effects of this field on the properties of solvent molecules and heat conduction are studied. A correctly stated functional method and a finite element approach are comparable to a certain type of differential equations. In order demonstrate the effects...
-
Reliability of acicular grindable thermocouples for transient temperature measurements at sliding contacts
PublicationAcicular grindable thermocouples represent an interesting and prospective technique of temperature measurements at sliding contacts. This study aimed at the investigation of their reliability and accuracy as applied to the friction materials of various classes in contact with steel. The tests were conducted on a pin-on-disc tribometer under stationary and transient regimes. The experimental results were validated by comparing the...
-
Estimating the parameter of inequality aversion on the basis of a parametric distribution of incomes
PublicationResearch background: In applied welfare economics, the constant relative inequality aversion function is routinely used as the model of a social decisionmaker’s or a society’s preferences over income distributions. This function is entirely determined by the parameter, ε, of inequality aversion. However, there is no authoritative answer to the question of what the range of ε an analyst should select for empirical work. Purpose...
-
Smooth orthogonal projections on sphere.
PublicationWe construct a decomposition of the identity operator on the sphere S^d as a sum of smooth orthogonal projections subordinate to an open cover of S^d. We give applications of our main result in the study of function spaces and Parseval frames on the sphere.
-
Układy napędowe pojazdów elektrycznych
PublicationW artykule omówiono nowe technologie stosowane w układach napędowych pojazdów elektrycznych. Praca zawiera zależności teorii ruchu pojazdu, nowe rozwiązania w konstrukcji silników trakcyjnych. Przedstawiono również zagadnienia układów zasilania bateryjnego i magazynów energii z superkondensatorami. Pokazano metody sterowania zapewniające optymalizacje rozdziału energii pomiędzy akumulatorami a magazynem energii. Zaprezentowano...
-
Performance improvement of NN based RTLS by customization of NN structure - heuristic approach
PublicationThe purpose of this research is to improve performance of the Hybrid Scene Analysis – Neural Network indoor localization algorithm applied in Real-time Locating System, RTLS. A properly customized structure of Neural Network and training algorithms for specific operating environment will enhance the system’s performance in terms of localization accuracy and precision. Due to nonlinearity and model complexity, a heuristic analysis...