wyświetlamy 1000 najlepszych wyników Pomoc
Wyniki wyszukiwania dla: COMPLEX LINEAR SYSTEM OF EQUATIONS
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Peer assessment as a method for measuring harmful internet use
PublikacjaHarmful Internet use (HIU) describes unintended use of the Internet. It could be both self-harm and harming others. Our research goal is to develop a more accurate method for measuring HIU by this novel peer assessment. As such, it may become, with our call for more research, a paradigm shift supplementing every rating scale or other type of Internet use assessment. In addition to classic statistical analysis, structural equations...
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Design criterion for hydrodynamic vortex separators
PublikacjaTechnical objects designing involves determination of geometrical parameters that characterize a given object. When the device is described by the differential equations, an inverse problem brings difficulties, as geometrical values sought condition the solution to the problem. Vortex separators can be designed by the "criterion method'. Firstly, a critical particle is distinguished such that bigger particles are removed from...
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On the Nonlinea Distortions of Sound and its Coupling with Other Modes in a Gasesous Plasma with Finite Electric Conductivity in a Magnetic Field
PublikacjaNonlinear phenomena of the planar and quasi-planar magnetoacoustic waves are considered. We focus on deriving of equations which govern nonlinear excitation of the non-wave motions by the intense sound in initially static gaseous plasma. The plasma is treated as an ideal gas with finite electrical conductivity permeated by a magnetic field orthogonal to the trajectories of gas particles. This introduces dispersion of a flow. Magnetoacoustic...
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Positive solutions to fractional differential equations involving Stieltjes integral conditions
PublikacjaIn this paper, we investigate nonlocal boundary value problems for fractional differential equations with dependence on the first-order derivatives and deviating arguments. Sufficient conditions which guarantee the existence of at least three positive solutions are new and obtained by using the Avery–Peterson theorem. We discuss problems (1) and (2) when argument b can change the character on [0, 1], so in some subinterval I of...
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The influence of stainless steels microstructure evolution on the mechanical properties of pressure installation elements
PublikacjaIn this paper results of FEM analysis performed for pipe and 90o elbow, made of super duplex stainless steel, after precipitation of sigma phase (),were presented. Heat treatment conditions simulate accidental overheating that can occur in nuclear installations after cooling circulation fails. For initial and modified microstructure tensile test was performed and numerical description of work hardening curves was done. Verification...
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The influence of stainless steels microstructure evolution on the mechanical properties of pressure installation elements
PublikacjaIn this paper results of FEM analysis performed for pipe and 90o elbow, made of super duplex stainless steel, after precipitation of sigma phase (s), were presented. Heat treatment conditions simulate accidental overheating that can occur in nuclear installations after cooling circulation fails. For initial and modified microstructure tensile test was performed and numerical description of work hardening curves was done. Verification...
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Numerical tests of time-stepping schemes in the context of FEM for 6-field shell dynamics
PublikacjaThe paper deals with integration of dynamic equations of irregular shells performed with relatively long time steps. Numerical instability appearing often in this kind of analysis motivated the authors to present some studies based on numerical tests referring to convergence problems of finite element analysis as well the applied stability conditions. The analysis is carried out on simulations of shell dynamics with the where the...
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Vibrational excitation of acetylene by positron impact
PublikacjaVibrationally inelastic quantum calculations are carried out at low collision energies for the scattering of a beam of positrons off acetylene gaseous molecules. The normal mode analysis is assumed to be valid and the relative fluxes into the C–C and C–H symmetric vibrational modes are computed within a Body-Fixed (BF) formulation of the dynamics by solving the relevant vibrational Coupled Channels (VCC) equations. The clear dominance...
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Modelling of heat and mass transfer through wooden buildings
PublikacjaThe aim of this review paper is to examine the most recent available studies dealing with theoretical, numerical and experimental aspects related to modelling of heat and mass transfer through wooden buildings. The main thermophysical, mechanical and hygrometric properties of wood are firstly discussed. Then, the basic governing equations of heat and mass transfer phenomena are presented. A detailed description of the physical...
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Simplified probabilistic analysis of settlement of cyclically loaded soil stratum using point estimate method
PublikacjaThe paper deals with the probabilistic analysis of settlement of a non-cohesive soil layer subjected to cyclic loading. Originally, the settlement assessment is based on deterministic compaction model which requires integration of a set of differential equations. However, making use of the Bessel functions the settlement of the soil stratum can be calculated by means of simplified algorithm. The compaction model parameters were...
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Generalized temperature dependence model for anammox process kinetics
PublikacjaTemperature is a key operational factor influencing the anammox process kinetics. In particular, at temperatures below 15 °C, the specific anammox activity (SAA) considerably decreases. This study aimed to describe the temperature dependence of the anammox process kinetics in the temperature range from 10 to 55 °C, including the specific characteristics of“cold anammox”. The commonly used Arrhenius and extended and modifiedRatkowsky...
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Buckling analysis of piezo-magnetoelectric nanoplates in hygrothermal environment based on a novel one variable plate theory combining with higher-order nonlocal strain gradient theory
PublikacjaIn the present investigation, a new first-order shear deformation theory (OVFSDT) on the basis of the in-plane stability of the piezo-magnetoelectric composite nanoplate (PMEN) has been developed, and its precision has been evaluated. The OVFSDT has many advantages compared to the conventional first-order shear deformation theory (FSDT) such as needless of shear correction factors, containing less number of unknowns than the existing...
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A Compact Basis for Reliable Fast Frequency Sweep via the Reduced-Basis Method
PublikacjaA reliable reduced-order model (ROM) for fast frequency sweep in time-harmonic Maxwell’s equations by means of the reduced-basis method is detailed. Taking frequency as a parameter, the electromagnetic field in microwave circuits does not arbitrarily vary as frequency changes, but evolves on a very low-dimensional manifold. Approximating this low-dimensional manifold by a low dimension subspace, namely, reduced-basis space, gives...
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A Quasi-2D MOSFET Model — 2D-to-Quasi-2D Transformation
PublikacjaA quasi-two-dimensional (quasi-2D) representation of the MOSFET channel is proposed in this work. The representation lays the foundations for a quasi 2D MOSFET model. The quasi 2D model is a result of a 2D into quasi 2D transformation. The basis for the transformation are an analysis of a current density vector field and such phenomena as Gradual Channel Detachment Effect (GCDE), Channel Thickness Modulation Effect (CTME), and...
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Lax-Wendroff and McCormack Schemes for Numerical Simulation of Unsteady Gradually and Rapidly Varied Open Channel Flow
PublikacjaTwo explicit schemes of the finite difference method are presented and analyzed in the paper. The applicability of the Lax-Wendroff and McCormack schemes for modeling unsteady rapidly and gradually varied open channel flow is investigated. For simulation of the transcritical flow the original and improved McCormack scheme is used. The schemes are used for numerical solution of one dimensional Saint-Venant equations describing free...
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Approximate models and parameter analysis of the flow process in transmission pipelines
Publikacjathe paper deals with the problem of early leak detection in transmission pipelines. First we present the derivation of state-space equations of the flow process in the pipelines. This description is then aggregated in order to obtain a principal model. Next, the problem of process model parameterization is addressed, taking into account the maximization of a model stability margin. The location of the maximum is determined using...
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Smooth Particle Hydrodynamics (SPH) approach in simulating large penetration into soil
PublikacjaA study of Smooth Particle Hydrodynamics (SPH) approach for predicting large soil deformation is presented. Theoretical basics of SPH method, including the equations governing, discussion of the importance of smoothing function length, contact formulation, boundary treatment and finally utilization in hydrocodes simulations are presented. An application of SPH to a real case of large penetrations (crater creating) into soil caused...
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Predicting the viscosity and electrical conductivity of ionic liquids on the basis of theoretically calculated ionic volumes
PublikacjaSelected physical properties of the ionic liquids might be quantitatively predicted based on the volumes of the ions these systems are composed of. It is demonstrated that the ionic volumes calculated using relatively simple theoretical quantum chemistry methods can be utilised to estimate the viscosities and electrical conductivities of various commonly used ionic liquids. The fitting formulas of the exponential form are offered...
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Discussion of “Development of an Accurate Time integration Technique for the Assessment of Q-Based versus h-Based Formulations of the Diffusion Wave Equation for Flow Routing” by K. Hasanvand, M.R. Hashemi and M.J. Abedini
PublikacjaThe discusser read the original with great interest. It seems, however, that some aspects of the original paper need additional comments. The authors of the original paper discuss the accuracy of a numerical solution of the diffusion wave equation formulated with respect to different state variables. The analysis focuses on nonlinear equations in the form of a single transport equation with the discharge Q (volumetric flow rate)...
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Surface finite viscoelasticity and surface anti-plane waves
PublikacjaWe introduce the surface viscoelasticity under finite deformations. The theory is straightforward generalization of the Gurtin–Murdoch model to materials with fading memory. Surface viscoelasticity may reflect some surface related creep/stress relaxation phenomena observed at small scales. Discussed model could also describe thin inelastic coatings or thin interfacial layers. The constitutive equations for surface stresses are...
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Energy conversion in systems-contained laser irradiated metallic nanoparticles - comparison of results from analytical solutions and numerical methods
PublikacjaThis work introduces the theoretical method of metallic nanoparticles’ (NPs’) heat and mass transfer where the particles are coated on a surface (base), together with considering the case wherein nanoparticles move freely in a pipe. In order to simulate the heat transfer, energy and radiative transfer equations are adjusted to the considered issue. NPs’ properties are determined following the nanofluidic theories, whereas absorption...
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Kinetics of nitrogen removal processes in constructed wetlands
PublikacjaThe aim of this paper is to present a state-of-the-art review of the kinetics of nitrogen removal in constructed wetlands. Biological processes of nitrogen removal from wastewater can be described using equations and kinetic models. Hence, these kinetic models which have been developed and evaluated allow for predicting the removal of nitrogen in treatment wetlands. One of the most important, first order removal model, which is...
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Modelling a 6-dof manipulator using Matlab software
PublikacjaThis paper presents an alternative approach to modelling a revolute robot. The manipulator in question is Kuka KR 16-2. The main problem in robot modelling is a kinematic analysis. The revolute robot consist of six rotary joints (6-DOF) with base, shoulder, elbow and wirst. The kinematics problem is defined as a transformation from the cartesian space to the joint space. The Denavit- Hartenberg (D-H) model of representation was...
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Positive solutions to second-order differential equations with dependence on the first-order derivative and nonlocal boundary conditions
PublikacjaIn this paper, we consider the existence of positive solutions for second-order differential equations with deviating arguments and nonlocal boundary conditions. By the fixed point theorem due to Avery and Peterson, we provide sufficient conditions under which such boundary value problems have at least three positive solutions. We discuss our problem both for delayed and advanced arguments α and also in the case when α(t)=t, t∈[0,1]....
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Flexomagneticity in Functionally Graded Nanostructures
PublikacjaFunctionally graded structures have shown the perspective of materials in a higher efficient and consistent manner. This study reports a short investigation by concentrating on the flexomagnetic response of a functionally graded piezomagnetic nano-actuator, keeping in mind that the converse magnetic effect is only taken into evaluation. The rule of mixture assuming exponential composition of properties along with the thickness...
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An inclination in Thermal Energy Using Nanoparticles with Casson Liquid Past an Expanding Porous Surface
PublikacjaPhysical aspects of inclined MHD nanofluid towards a stretching sheet embedded in a porous medium are visualized. Two types of nanoparticles are used named as copper and alumna dioxide with water as base fluid. Similarity transformations are used to convert the partial differential equations into the set of ordinary differential equation. Closed solutions are found to examine the velocity and the temperature profiles. It is examined...
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Janusz Smulko prof. dr hab. inż.
OsobyUrodził się 25 kwietnia 1964 r. w Kolnie. Ukończył w 1989 r. z wyróżnieniem Wydział Elektroniki Politechniki Gdańskiej, specjalność aparatura pomiarowa. Zajął II miejsce w konkursie Czerwonej Róży na najlepszego studenta Wybrzeża w 1989 r. Od początku kariery związany z Politechniką Gdańską: asystent (1989–1996), adiunkt (1996–2012), profesor nadzwyczajny PG (od 2012). Odbył staże naukowe w Texas A&M University (2003, NATO...
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NUMERICAL SIMULATION OF CRATER CREATING PROCESS IN DYNAMIC REPLACEMENT METHOD BY SMOOTH PARTICLE HYDRODYNAMICS
PublikacjaA theoretical base of SPH method, including the governing equations, discussion of importance of the smoothing function length, contact formulation, boundary treatment and finally utilization in hydrocode simulations are presented. An application of SPH to a real case of large penetrations (crater creating) into the soil caused by falling mass in Dynamic Replacement Method is discussed. An influence of particles spacing on method...
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Novel Analytic-Numerical Model of Free Convection: with Leading Edge Considered
PublikacjaA novel solution of the free convection boundary problem is represented in analytical form for velocity and temperature for an isothermal vertical plate, as an example. These fields are built as a Taylor Series in the x coordinate with coefficients as functions of the vertical coordinate (y). We restrict ourselves by cubic approximation for both functions. The basic Navier-Stokes and Fourier-Kirchhoff equations and boundary conditions...
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The equations for interactions of polarization modes in optical fibres including the kerr effect
PublikacjaWe have derived coupled nonlinear Schro¨ dinger equations (CNLSE) for arbitrary polarized light propagation in a single-mode fibre employing electromagnetic field complete description. We used a basis of transverse eigenmodes with appropriate projecting; hence, the nonlinear constants depend on the waveguide geometry. Accounting for a weak nonlinearity, which is connected to the Kerr effect, we have given explicit expressions for...
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Simulation of the remanence influence on the transient states in a single-phase multiwinding transformer
PublikacjaThis 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...
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Straightened characteristics of McKendrick-von Foerster equation
PublikacjaWe study the McKendrick-von Foerster equation with renewal (that is the age-structured model, with total population dependent coefficient and nonlinearity). By using a change of variables, the model is then transformed to a standard age-structured model in which the total population dependent coefficient of the transport term reduces to a constant 1. We use this transformation to get existence, uniqueness of solutions of the problem...
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Finite element modeling of plastic hinges based on ductility demand-capacity method using nonlinear material for dynamic analysis
PublikacjaThe article discusses modeling plastic hinges in reinforced concrete interme-diate supports using finite elements methods. The ductility demand-capacitymethod was used to determine the geometrical parameters of cross-section plas-ticization zones, their ability to move and rotate, as well as their ductility. Dueto the varied geometry and stiffness of the supports and their nonlinear behav-ior under dynamic load, this method was...
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Maximum transportation growth in energy and solute particles in Prandtl martial across a vertical 3D-heated surface: Simulations achieved using by finite element approach
PublikacjaThe 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...
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Effect of Sinusoidal Corrugated Geometries on the Vibrational Response of Viscoelastic Nanoplates
PublikacjaThe vibrational behavior of viscoelastic nanoplates with a corrugated geometry is a key topic of practical interest. This problem is addressed here for wrinkled nanoplates with small corrugations related to incorrect manufacturing. To this end, a new One-Variable First-order Shear Deformation plate Theory (OVFSDT) is proposed in a combined form with a non-local strain gradient theory. The Kelvin–Voigt model is employed to describe...
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On the Nonlinear Effects of Magnetoacoustic Perturbations in Optically Thin Quasi-Isentropic Plasmas
PublikacjaNonlinear effects of planar magnetosound perturbations in a plasma are discussed. Plasma is non-adiabatic due to optically thin radiation and external heating. For these reasons, thermal instability of a plasma may appear which makes it acoustically active. The plasma is assumed to be initially homogeneous ideal gas with infinite electrical conductivity permeated by a straight magnetic field which is orthogonal to the trajectories...
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Robust identification of quadrocopter model for control purposes
PublikacjaThe paper addresses a problem of quadrotor unmanned aerial vehicle (so-called X4-flyer or quadrocopter) utility model identification for control design purposes. To that goal the quadrotor model is assumed to be composed of two abstracted subsystems, namely a rigid body (plant) and four motors equipped with blades (actuators). The model of the former is acquired based on a well-established dynamic equations of motion while the...
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Vibration and buckling characteristics of nonlocal beam placed in a magnetic field embedded in Winkler–Pasternak elastic foundation using a new refined beam theory: an analytical approach
PublikacjaIn this article, a new refined beam theory, namely one variable first-order shear deformation theory, has been employed to study the vibration and buckling characteristics of nonlocal beam. The beam is exposed to an axial magnetic field and embedded in Winkler–Pasternak foundation. The von Kármán hypothesis along with Hamilton’s principle has been implemented to derive the governing equations for both the vibration and buckling...
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A Measurement-Based Approach for Speed Control of Induction Machines
PublikacjaThis paper presents an approach to design a measurement-based controller for induction machines. The proposed control approach is motivated by the fact that developing an appropriate mechanical model of such induction machines is a challenging task. Since our proposed control methodology is only on the basis of measured data, the controller design does not require any information about the model of the mechanical part. The control...
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A Comparison of Simplified Two-dimensional Flow Models Exemplified by Water Flow in a Cavern
PublikacjaThe paper shows the results of a comparison of simplified models describing a two-dimensional water flow in the example of a water flow through a straight channel sector with a cavern. The following models were tested: the two-dimensional potential flow model, the Stokes model and the Navier-Stokes model. In order to solve the first two, the boundary element method was employed, whereas to solve the Navier-Stokes equations, the...
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AN OVERVIEW OF HEAT TRANSFER ENHANCEMENT BASED UPON NANOPARTICLES INFLUENCED BY INDUCED MAGNETIC FIELD WITH SLIP CONDITION VIA FINITE ELEMENT STRATEGY
PublikacjaThe mathematical model of heat generation and dissipation during thermal energy transmission employing nanoparticles in a Newtonian medium is investigated. Dimensionless boundary layer equations with correlations for titanium dioxide, copper oxide, and aluminium oxide are solved by the finite element method. Parameters are varied to analyze their impact on the flow fields. Various numerical experiments are performed consecutively...
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On Wrinkling in Sandwich Panels with an Orthotropic Core
PublikacjaThis paper deals with the local loss of stability (wrinkling) problem of a thin facing of a sandwich panel. Classical solutions to the problem of facing instability resting on a homogeneous and isotropic substructure (a core) are compared. The relations between strain energy components associated with different forms of core deformations are discussed. Next, a new solution for the orthotropic core is presented in detail, which...
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Direct-contact condensation from vapour- gas mixture in a spray ejector condenser for negative CO2 power plant
PublikacjaDirect-contact condensation of vapour containing the inert gas on a spray of subcooled liquid exists in a number of technical applications. For example, it may be found in the nuclear industry (e.g. pressurized jet under normal operating conditions, in safety analyses) or in the chemical industry (e.g. mixing-type heat exchanger, degasser, sea water desalting). The problem is also essential to modelling and analysis of some...
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Tuning matrix-vector multiplication on GPU
PublikacjaA matrix times vector multiplication (matvec) is a cornerstone operation in iterative methods of solving large sparse systems of equations such as the conjugate gradients method (cg), the minimal residual method (minres), the generalized residual method (gmres) and exerts an influence on overall performance of those methods. An implementation of matvec is particularly demanding when one executes computations on a GPU (Graphics...
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Analysis of the process of water entry of an amphibious vehicle
PublikacjaThe paper presents a method of computational and experimental analysis of the process of water entry of an amphibious vehicle. The computational method is based on the Reynolds Averaged Navier-Stokes Equations (RANSE) solver and the xperiment was carried out in the towing tank at Ship Design and Research Centre S.A. with the use of a scale model. The analysis was focused on the safety of water entry, i.e. the maximum pitch and...
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Vortex flow caused by periodic and aperiodic sound in a relaxing maxwell fluid
PublikacjaThis paper concerns the description of vortex flow generated by periodic and aperiodic sound in relaxing Maxwell fluid. The analysis is based on governing equation of vorticity mode, which is a result of decomposition of the hydrodynamic equations for fluid flow with relaxation and thermal conductivity into acoustical and non-acoustical parts. The equation governing vorticity mode uses only instantaneous, not averaged over sound...
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Relativity of arithmetic as a fundamental symmetry of physics
PublikacjaArithmetic operations can be defined in various ways, even if one assumes commutativity and associativity of addition and multiplication, and distributivity of multiplication with respect to addition. In consequence, whenever one encounters ‘plus’ or ‘times’ one has certain freedom of interpreting this operation. This leads to some freedom in definitions of derivatives, integrals and, thus, practically all equations occurring in...
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Propagation of acoustic pulses in some fluids with yield stress
PublikacjaThis study is devoted to the derivation of approximate equations governing acoustic pulses in flows with yieldstress, including some time-dependent flows with a slow dependence on time of yield stress and apparent viscosity. Themodeling of yield stress and apparent viscosity in the vicinity of a zero deformation rate allows us to consider a thixotropicfluid as a Bingham plastic with coefficients that are dependent on time. The...
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Higher harmonics of the intensity modulated Photocurrent/Photovoltage spectroscopy response - a tool for studying photoelectrochemical nonlinearities
PublikacjaIn this work, a higher harmonic analysis (HHA) of the intensity modulated photocurrent/photovoltage (IMPS/IMVS) spectroscopy data is proposed as a potent tool for studying nonlinear phenomena in photoelectrochemical and photovoltaic systems. Analytical solutions of kinetic equations were constructed for cases of single and double resonance accounting for various sources of higher harmonics. These sources correspond to the physical...
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A subdomain model for armature reaction field and open‐circuit field prediction in consequent pole permanent magnet machines
PublikacjaIn this paper, the machine quantity, such as electromagnetic torque, self and mutual inductances, and electromotive force, is analytically calculated for non-overlapping winding consequent pole slotted machine for open-circuit field and armature reaction. The sub-domain approach of (2-D) analytical model is developed using Maxwell's equations and divide the problem into slots, slot-openings, airgap and magnets region, the magnet...