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Search results for: DIRECTIONAL PULSE PROPAGATION
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Corrosion Properties of Dissimilar AA6082/AA6060 Friction Stir Welded Butt Joints in Different NaCl Concentrations
PublicationA solid-state friction stir welding method which is increasingly used in the marine and shipbuilding industry, has been developed to produce welds with high mechanical properties. In seawater, the oxide layer of aluminium is attacked by Cl− ions resulting in its disruption and formation of pitting corrosion. It is particularly important to determine the electrochemical properties of the produced welds and to evaluate the efect...
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The In-Depth Studies of Pulsed UV Laser-Modified TiO2 Nanotubes: The Influence of Geometry, Crystallinity, and Processing Parameters
PublicationThe laser processing of the titania nanotubes has been investigated in terms of morphology, structure, and optical properties of the obtained material. The length of the nanotubes and crystallinity, as well as the atmosphere of the laser treatment, were taken into account. The degree of changes of the initial geometry of nanotubes were checked by means of scanning electron microscopy, which visualizes both the surface and the cross-section....
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Detection and Imaging of Debonding in Adhesive Joints of Concrete Beams Strengthened with Steel Plates Using Guided Waves and Weighted Root Mean Square
PublicationStrengthening of engineering structures is an important issue, especially for elements subjected to variable loads. In the case of concrete beams or slabs, one of the most popular approaches assumes mounting an external reinforcement in the form of steel or composite elements by structural adhesives. A significant disadvantage of adhesive joints is the lack of access to the adhesive film for visual condition assessment, thus, there...
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Planar Microwave Bragg Reflector Resonant Dielectric Sensor
PublicationIn this paper, a periodic structure is used to design a microwave Bragg reflector with the help of hexagonal lattice, which provides a 5 GHz wide stopband between the low-pass band with cut-off frequency 2.6 GHz and the bandpass response with start and stop frequency 7.8 GHz and 10.5 GHz, respectively. A defect in lattice allows passing a narrowband signal at 6 GHz which is found, from the dispersion relation, to be in the region...
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Free-standing TiO2 nanotubes decorated with spherical nickel nanoparticles as a cost-efficient electrocatalyst for oxygen evolution reaction
PublicationHere, we report significant activity towards the oxygen evolution reaction (OER) of spherical nickel nanoparticles (NPs) electrodeposited onto free-standing TiO2 nanotubes (TNT) via cyclic voltammetry. It has been shown that simple manipulation of processing parameters, including scan rate and number of cycles, allows for formation of the NPs in various diameters and amounts. The polarization data with respect to transmission electron...
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Circularly Polarized Antenna Array design with the Potential of Gain-Size Trade-off and Omnidirectional Radiation for Millimeter-Wave Small Base Station Applications
PublicationThis paper presents the design and validation of a slot-patch-hybrid circularly polarized antenna array for 28 GHz millimeter (mm) wave (mm-wave) applications. The proposed design has a simple geometry that facilitates the fabrication process, which is otherwise a challenging task due to the sub-mm dimensions of the circuit in the mm-wave band. In the proposed structure, aperture-coupled series slot-fed array is utilized to excite...
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Derivation of motor mean phase currents in PMSM drives operating with low switching-to-fundamental frequency ratio
PublicationPulse width modulation (PWM) of inverter output voltage causes the waveforms of motor phase cur-rents to consist of distinctive ripples. In order to provide suitable feedback for the motor current con-trollers, the mean value must be extracted from the currents’ waveforms in every PWM cycle. A com-mon solution to derive the mean phase currents is to sample their value at the midpoint of a symmetrical PWM cycle. Using an assumption...
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Electrochemical determination of neurotransmitter serotonin using boron/nitrogen co-doped diamond-graphene nanowall-structured particles
PublicationElectrode fouling is a major issue in biological detection due to the adhesion of the protein itself and polymerization of biomolecules on the electrode surface, impeding the electron transfer ability and decreasing the current response. To overcome this issue, the use of anti-fouling material, especially boron-doped diamond (BDD) electrode, is an alternative way. However, the electrocatalytic activity of BDD is inadequate compared...
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Mechanical Properties and Residual Stress Measurements of Grade IV Titanium and Ti-6Al-4V and Ti-13Nb-13Zr Titanium Alloys after Laser Treatment
PublicationNowadays, surface engineering focuses on research into materials for medical applications. Titanium and its alloys are prominent, especially Ti-6Al-4V and Ti-13Nb-13Zr. Samples made of pure grade IV titanium and the titanium alloys Ti-6Al-4V and Ti-13Nb-13Zr were modified via laser treatment with laser beam frequency f = 25 Hz and laser beam power P = 1000 W during a laser pulse with duration t = 1 ms. Subsequently, to analyze...
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In vivo imaging of the human eye using a two-photon excited fluorescence scanning laser ophthalmoscope
PublicationBACKGROUND. Noninvasive assessment of metabolic processes that sustain regeneration of human retinal visual pigments (visual cycle) is essential to improve ophthalmic diagnostics and to accelerate development of new treatments to counter retinal diseases. Fluorescent vitamin A derivatives, which are the chemical intermediates of these processes, are highly sensitive to UV light; thus, safe analyses of these processes in humans...
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Mechanical and fracture properties of concrete reinforced with recycled and industrial steel fibers using Digital Image Correlation technique and X-ray micro computed tomography
PublicationPaper presents investigation of fracture phenomenon in plain concrete and in concrete reinforced with both recycled steel fibers (RSF) and industrial steel fibers (ISF). The wedge splitting test (WST), which enables stable crack propagation for quasi-brittle materials, was carried out on 75 75 75 mm cube samples. Initially, fracture process zone development was investigated only on the surface of samples using Digital Image Correlation...
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Poroelastic Road Surface – a Promising Road Traffic Noise Abatement Solution
PublicationRoad surfaces have a direct impact on the generation of noise by rolling tyres, the main and dominant source of noise of moving vehicles, as well as may affect propagation of noise emitted by all noise sources of a vehicle. Thus there is no doubt that pavement should be considered as one of the major potential road traffic noise abatement measure. Low noise pavements of existing types may in new conditions provide up to 8 dB of...
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Edge-Guided Mode Performance and Applications in Nonreciprocal Millimeter-Wave Gyroelectric Components
PublicationThe analogies between the behavior of gyromagnetic and gyroelectric nonreciprocal structures, the use of the simple transfer matrix approach, and the edge-guided (EG) wave property, supported in a parallel plate model for integrated magnetized semiconductor waveguide, are investigated in those frequency regions, where the effective permittivity is negative or positive. As with their ferrite counterparts, the leakage of the EG waves...
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Wave Frequency Effects on Damage Imaging in Adhesive Joints Using Lamb Waves and RMS
PublicationStructural adhesive joints have numerous applications in many fields of industry. The gradual deterioration of adhesive material over time causes a possibility of unexpected failure and the need for non-destructive testing of existing joints. The Lamb wave propagation method is one of the most promising techniques for the damage identification of such connections. The aim of this study was experimental and numerical research on...
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A procedure for the identification of effective mechanical parameters of additively manufactured elements using integrated ultrasonic bulk and guided waves
PublicationThe subject of the current work was a simple but robust novel two-stage procedure for the non-destructive determination of effective elastic constants using ultrasonic wave propagation. First, ultrasonic bulk wave velocities measured on cubic samples were used to calculate most of the elements of the stiffness matrix. Secondly, the remaining elements were determined using the dispersion curves of elastic guided waves measured on...
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Wireless Link Selection Methods for Maritime Communication Access Networks—A Deep Learning Approach
PublicationIn recent years, we have been witnessing a growing interest in the subject of communication at sea. One of the promising solutions to enable widespread access to data transmission capabilities in coastal waters is the possibility of employing an on-shore wireless access infrastructure. However, such an infrastructure is a heterogeneous one, managed by many independent operators and utilizing a number of different communication...
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Reinforcement Learning Algorithm and FDTD-based Simulation Applied to Schroeder Diffuser Design Optimization
PublicationThe aim of this paper is to propose a novel approach to the algorithmic design of Schroeder acoustic diffusers employing a deep learning optimization algorithm and a fitness function based on a computer simulation of the propagation of acoustic waves. The deep learning method employed for the research is a deep policy gradient algorithm. It is used as a tool for carrying out a sequential optimization process the goal of which is...
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The influence of the grid density of measurement points on damage detection in an isotropic plate by the use of elastic waves and laser scanning Doppler vibrometry
PublicationDamage detection in structural components, especially in mechanical engineering, is an 2 important element of engineering practice. There are many methods of damage detection, in which 3 changes in various parameters caused by the presence of damage are analysed. Recently, methods 4 based on the analysis of changes in dynamic parameters of structures, i.e. frequencies or mode shapes 5 of natural vibrations, as well as changes in...
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Estimation of Coherence Bandwidth for Underwater Acoustic Communication Channel
PublicationA shallow underwater acoustic communication channel is characterized by strong multipath propagation. The signal reaching the receiver consists of a direct waveform and a number of its delayed and suppressed replica. A significant time dispersion of the transmitted signal and selective fading of its spectrum are observed. Coherence bandwidth defines maximal bandwidth, wherein the channel amplitude characteristic remains constant...
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Tracking of the broadband source of the underwater noise in the very shallow water conditions
PublicationThe paper contains the result s, both theoretical and experimental , connected with the tracking of the underwater noise source as small ships, pontoon , diver and so on. The pro blem of security in the shallow water area is the challenge for underwater acousticians. In this paper there is take n into account the detection of the sources that move on the surface of the sea or underwater in shallow...
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Nonlinear properties of the Gotland Deep – Baltic Sea
PublicationThe properties of the nonlinear phenomenon in water, including sea water, have been well known for many decades. The feature of the non homogeneous distribution of the speed of sound along the depth of the sea is very interesting from the physical and technical point of view. It is important especially in the observation of underwater area by means of acoustical method ( Grelowska et al ., 2013; 2014). The observation of the underwater...
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Fading Modelling in Dynamic Off-Body Channels
PublicationThis paper presents an off-body fading channel model for Body Area Networks (BANs) in indoor environments. The proposed model, which is based on both simulations and measurements in a realistic environment, consists of three components: mean path loss, body shadowing, and multipath fading. Seven scenarios in an indoor environment (a medium-size room with furniture, mostly consisting of wooden tables and chairs) have been measured:...
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Damage of a post-tensioned concrete bridge – Unwanted cracks of the girders
PublicationThe cracking of a post-tensioned T-beam superstructure, which was built using the incremental launching method, is analyzed in the paper. The problem is studied in detail, as specific damage was observed in the form of longitudinal cracks, especially in the mid-height zone of the girder at the interface of two assembly sections. The paper is a case study. A detailed inspection is done and non-destructive testing results of the...
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The influence oil additives on spread cracks in silicon nitride
PublicationThe paper presents an experimental study of the influence of oil additives (Cl, S, P, cerium dioxide (CeO2)) on spread cracks in silicon nitride. The additives Cl, S, P are bound in molecules in liquid form soluble in the base oil. The CeO2 is purely in powder form in suspension. The use of CeO2 powder was made based on the good results of polishing of silicon nitride. A ceramic angular contact ball bearing was modelled using a...
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Biological hazards in low noise, poroelastic road surfaces
PublicationDrainage pavements as well as poroelastic pavements ("PERS") are a very efficient way to decrease traffic noise by reducing tire/road noise at the source as well as noise propagation over the road surface. Many noise generating mechanisms at the tire/road interface are very much reduced by road porosity (pipe resonance, "air pumping", Helmholtz resonance and the horn effect). A well-designed porous or poroelastic road surface may...
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The shallow sea experiment with usage of linear hydrophone array
PublicationPurpose of this article is to present designed and made linear hydrophone array and the results obtained during in situ trails on Gulf of Gdańsk. The measuring system allowed to localize hydrophones in the selected points and perform measurements in both the horizontal antenna positioning and vertical. Made in this way recordings allow creating accurate 3D imaging of sound intensity/propagation. During research three floating objects...
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Supply current signal and artificial neural networks in the induction motor bearings diagnostics
PublicationThis paper contains research results of the diagnostics of induction motor bearings based on measurement of the supply current with usage of artificial neural networks. Bearing failure amount is greater than 40% of all engine failures, which makes their damage-free operation crucial. Tests were performed on motors with intentionally made bearings defects. Chapter 2 introduces the concept of artificial neural networks. It presents...
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About Unusual Diffraction and Thermal Self-Action of Magnetosonic Beam
PublicationThe dynamics of slightly diverging two-dimensional beams whose direction forms a constant angle θ with the equilibrium straight magnetic strength is considered. The approximate dispersion relations and corresponding links which specify hydrodynamic perturbations in confined beams are derived. The study is dedicated to the diffraction of a magnetosonic beam and nonlinear thermal self-action of a beam in a thermoconducting gaseous plasma....
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An Innovative Antenna Array with High Inter Element Isolation for Sub-6 GHz 5G MIMO Communication Systems
PublicationA novel technique is shown to improve the isolation between radiators in antenna arrays. The proposed technique suppresses the surface-wave propagation and reduces substrate loss thereby enhancing the overall performance of the array. This is achieved without affecting the antenna’s footprint. The proposed approach is demonstrated on a four-element array for 5G MIMO applications. Each radiating element in the array is constituted...
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A Numerical Study on Baseline-Free Damage Detection Using Frequency Steerable Acoustic Transducers
PublicationIn structural health monitoring (SHM) a considerable amount of damage detection algorithms based on guided waves (GW) have been developed. Most of them rely on extensive transducer networks, besides preliminary reference measurements of the structures. This originated a growing demand for hardware simplification and cost reduction of the wave-based SHM methods, driving the conception of new solutions enabling both: the reduction...
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ECHOES REDUCTION DURING DIGITAL DATA TRANSMISSION IN HYDROACOUSTIC CHANNEL – LABORATORY EXPERIMENT
PublicationThe possibility of using a hydroacoustic channel for digital data transmission is very limited. This is due to the effect of multipath propagation of the emitted acoustic wave and the damping of the mechanical wave in this medium, which increase with frequency. The first of these phenomena results in inter-symbol interference disturbances in data transmission systems, including even hundreds of symbols. Due to the number of reflections...
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Effects of CO2 and Nd:YAG Laser Remelting of the Ti6Al4V Alloy on the Surface Quality and Residual Stresses
PublicationThe titanium alloys are materials susceptible to tribological wear and the laser treatment can be applied in surface treatment processes to obtain for example higher hardness level. From the other side, it is important to take into consideration, that hardness increase that can be connected with cracks . The aim of this research was to investigate the effects of different lasers and the process parameters on the form and level...
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The optimization of enzyme immobilization at Au-Ti nanotextured platform and its impact onto the response towards glucose in neutral media
PublicationThe market of non-invasive glucose sensors is drastically growing due to increasing number of people suffering from diabetes. Therefore, there is a significant need for any improvement in the field of biosensors that can be used for monitoring glucose level in human body. In recent years the emphasis is put onto the modification of electrode material with enzymes possessing recognition centre specific towards particular molecules....
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Tailoring diamondised nanocarbon-loaded poly(lactic acid) composites for highly electroactive surfaces: extrusion and characterisation of filaments for improved 3D-printed surfaces
PublicationA new 3D-printable composite has been developed dedicated to electroanalytical applications. Two types of diamondised nanocarbons - detonation nanodiamonds (DNDs) and boron-doped carbon nanowalls (BCNWs) - were added as fillers in poly(lactic acid) (PLA)-based composites to extrude 3D filaments. Carbon black served as a primary filler to reach high composite conductivity at low diamondised nanocarbon concentrations (0.01 to 0.2...
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Type III Responses to Transient Inputs in Hybrid Nonlinear Neuron Models
PublicationExperimental characterization of neuronal dynamics involves recording both of spontaneous activity patterns and of responses to transient and sustained inputs. While much theoretical attention has been devoted to the spontaneous activity of neurons, less is known about the dynamic mechanisms shaping their responses to transient inputs, although these bear significant physiological relevance. Here, we study responses to transient...
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The influence of the Cu2O deposition method on the structure, morphology and photoresponse of the ordered TiO2NTs/Cu2O heterojunction
PublicationThe increased interest in highly ordered titania structures exhibiting tubular shape that could be directly formed onto the stable substrate is related with the intensive research on their modification enabling absorption of light within the wide solar spectrum and its further conversion into electric or chemical energy. Among others, formation of uniform 3D heterojunctions based on the TiO2 nanotubes attracts attention since porous...
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A new concept of PWM duty cycle computation using the Barycentric Coordinates in a Three-Dimensional voltage vectors arrangement
PublicationThe paper presents a novel approach to the Pulse Width Modulation (PWM) duty cycle computing for complex or irregular voltage vector arrangements in the two (2D) and three–dimensional (3D) Cartesian coordinate systems. The given vectors arrangement can be built using at least three vectors or collections with variable number of involved vectors (i.e. virtual vectors). Graphically, these vectors form a convex figure, in particular,...
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Interactions between bioactive components determine antioxidant, cytotoxic and nutrigenomic activity of cocoa powder extract
PublicationNumerous studies have shown, rather disappointingly, that isolated bioactive phytochemicals are not as biologically effective as natural plant products. Such a discrepancy may be explained by the concept of food synergy, which was verified in this research for cocoa extract versus its major components with regard to cancer chemoprevention. The evaluation embraced the relationship between redox properties evaluated in cell-free systems...
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X-Ray Computer Tomography Study of Degradation of the Zircaloy-2 Tubes Oxidized at High Temperatures
PublicationThe investigations of high-temperature oxidation of zirconium alloys, applied for fuel pellets in nuclear power plants, are usually limited to oxidation kinetics, phase transformations and microstructural characterization. The purpose of this research was to characterize the degradation phenomena occurring within oxide layer and at the interface oxide/metal, on internal and external Zircaloy-2 tube...
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Numerical investigation on behaviour of cylindrical steel tanks during mining tremors and moderate earthquakes
PublicationCylindrical steel tanks are important components of industrial facilities. Their safety becomes a crucial issue since any failure may cause catastrophic consequences. The aim of the paper is to show the results of comprehensive FEM numerical investigation focused on the response of cylindrical steel tanks under mining tremors and moderate earthquakes. The effects of different levels of liquid filling, the influence of non-uniform...
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Filter-Hilbert Method for Automatic Correction of Non-Anechoic Antenna Measurements with Embedded Self-Calibration Mechanism
PublicationOne of the most important steps in the process of antenna development involves measurements of its prototype. Far-field performance of radiators is normally characterized in strictly controlled environments such as anechoic chambers which can ensure certification-grade accuracy. Unfortunately, they are also characterized by high construction costs which might not be justified for low-budget research and/or teaching-related activities....
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Data Compression in Ultrasonic Network Communication via Sparse Signal Processing
PublicationThis document presents the approach of using compressed sensing in signal encoding and information transferring within a guided wave sensor network, comprised of specially designed frequency steerable acoustic transducers (FSATs). Wave propagation in a damaged plate was simulated using commercial FEM-based software COMSOL. Guided waves were excited by means of FSATs, characterized by the special shape of its electrodes, and modeled...
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Broadband Modeling of Motor Cable Impact on Common Mode Currents in VFD
PublicationExamination of conducted EMI generation and propagation in AC motor drives fed by frequency converter requires to consider parasitic capacitances in converters, motor windings and feeding cables to be taken into account. AC motor winding voltage transients and related common mode currents are significantly correlated with resonance effects occurring in converter's load circuits. Intensity levels of these phenomena depend...
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GPR investigation of the strengthening system of a historic masonry tower
PublicationIn this paper the condition assessment of the strengthening system of a masonry tower was carried out by the GPR method. The study provided unique experimental data acquired during measurements of the reinforced concrete frame embedded in masonry walls. Conducted numerical and experimental investigations were focused on the phenomenon of the diffraction-refraction scattering of the electromagnetic energy. A hyperbola resulting...
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Damage-Involved Structural Pounding in Bridges under Seismic Excitation
PublicationDuring severe earthquakes, pounding between adjacent superstructure segments of highway elevated bridges was often observed. It is usually caused by the seismic wave propagation effect and may lead to significant damage. The aim of the present paper is to show the results of the numerical analysis focused on damage-involved pounding between neighbouring decks of an elevated bridge under seismic excitation. The analysis was carried...
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Daylight evaluation for multi-family housing in Poland
PublicationThis PhD dissertation focuses on methods of daylight appraisal useful in the design of the contemporary multifamily housing. The theoretical part of the thesis offers a review of daylight indicators, evaluations methods and tools within the built environment. It covers a review of daylight recommendations found in building standards and other normative documents affecting the design of the residential spaces. A pilot work survey...
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Analytical approach for membrane action in laterally-restrained reinforced concrete square slabs under uniformly distributed loads
PublicationLaterally-restrained reinforced concrete slabs can mobilise compressive membrane action and subsequent tensile membrane action under extreme loading conditions, thereby enhancing the load resistance under uniformly distributed loads. Previous analytical study focuses primarily on tensile membrane action in simply-supported slabs. This paper describes an analytical approach for membrane action in laterally-restrained square slabs....
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On nonlinear dilatational strain gradient elasticity
PublicationWe call nonlinear dilatational strain gradient elasticity the theory in which the specific class of dilatational second gradient continua is considered: those whose deformation energy depends, in an objective way, on the gradient of placement and on the gradient of the determinant of the gradient of placement. It is an interesting particular case of complete Toupin–Mindlin nonlinear strain gradient elasticity: indeed, in it, the...
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On possible applications of media described by fractional-order models in electromagnetic cloaking
PublicationThe purpose of this paper is to open a scientific discussion on possible applications of media described by fractional-order (FO) models (FOMs) in electromagnetic cloaking. A 2-D cloak based on active sources and the surface equivalence theorem is simulated. It employs a medium described by FOM in communication with sources cancelling the scattered field. A perfect electromagnetic active cloak is thereby demonstrated with the use...
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Stateczność i niezawodność pełnomorskich platform wiertniczych
PublicationW pracy przedstawiono wieloletnie doświadczenia Autora w zakresie wybranych aspektów numerycznej analizy pełnomorskich platform wiertniczych, w szczególności stacjonarnych platform stalowych poddanych działaniu fal wiatrowych i wiatru. W opisie zachowania się platform uwzględniono współoddziaływanie trzech ośrodków: materiału konstrukcji, morskich fal wiatrowych i podłoża gruntowego. Przyjęcie do opisu stochastycznych właściwości...