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Search results for: finite-difference discretization
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Response of high voltage disconnector under seismic excitation - experimental and numerical study
PublicationThe efficiency of the energetic infrastructure system is a very import safety issue in the region experienced by the ground motion. The aim of the present paper is to show the results of the experimental and numerical study focused on the earthquake-induced response of the high voltage disconnector, which is an important element of energetic network. First, the impact tests as well as the sweep-sine shaking table tests were conducted....
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Structural response of existing spatial truss roof construction based on Cosserat rod theory
PublicationPaper presents the application of the Cosserat rod theory and newly developed associated finite elements code as the tools that support in the expert-designing engineering practice. Mechanical principles of the 3D spatially curved rods, dynamics (statics) laws, principle of virtual work are discussed. Corresponding FEM approach with interpolation and accumulation techniques of state variables are shown that enable the formulation...
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Behaviour of steel columns under impact
PublicationOne of import issues related to the idea of sustainable society is the safety of civil engineering structures. The safety and reliability of steel structures under impact loading is among a number of different aims during the design state. The aim of this paper is to present the results of investigation focused on dynamic behaviour of steel columns under impact loading. Modal and transient dynamic analyses using Finite Element...
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LNG TANK IN ŚWINOUJŚCIE: NONLINEAR ANALYSIS OF THE TANK DOME ELEMENTS BEHAVIOUR
PublicationIn this paper, the dome of a tank in the Świnoujście LNG terminal is analysed. Some of the rafter ribs at the connection with hangers were not mounted during construction of the tank dome. Therefore, it has become necessary to estimate its response, which has been done with the aid of some computational models of the dome, that have been created in the finite element method environment. Different local models are studied, aiming...
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A Bayesian regularization-backpropagation neural network model for peeling computations
PublicationA Bayesian regularization-backpropagation neural network (BRBPNN) model is employed to predict some aspects of the gecko spatula peeling, viz. the variation of the maximum normal and tangential pull-off forces and the resultant force angle at detachment with the peeling angle. K-fold cross validation is used to improve the effectiveness of the model. The input data is taken from finite element (FE) peeling results. The neural network...
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Application of regularized Savitzky–Golay filters to identification of time-varying systems
PublicationSavitzky–Golay (SG) filtering is a classical signal smoothing technique based on the local least squares approximation of the analyzed signal by a linear combination of known functions of time (originally — powers of time, which corresponds to polynomial approximation). It is shown that the regularized version of the SG algorithm can be successfully applied to identification of time-varying finite impulse response (FIR) systems....
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Efficient FPGA Implementation of an RFIR Filter Using the APC–OMS Technique with WTM for High-Throughput Signal Processing
PublicationNowadays, Finite Impulse Response (FIR) filters are used to change the attributes of a signal in the time or frequency domain. Among FIR filters, a reconfigurable filter has the advantage of changing the coefficient in real-time, while performing the operation. In this paper, the Anti-Symmetric Product Coding (APC) and Odd Multiple Storage (OMS) modules are utilized to implement the reconfigurable FIR filter (RFIR–APC–OMS). Herein,...
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Identification and non-integer order modelling of synchronous machines operating as generator
PublicationThis paper presents an original mathematical model of a synchronous generator using derivatives of fractional order. In contrast to classical models composed of a large number of R-L ladders, it comprises half-order impedances, which enable the accurate description of the electromagnetic induction phenomena in a wide frequency range, while minimizing the order and number of model parameters. The proposed model takes into account...
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On the necessity of experimental verification of numerical results in biomedical applications
PublicationPorous structures made of metal or biopolymers with a structure similar in shape and mechanical properties to human bone can be easily produced by stereolitography techniques, e.g. selective laser melting (SLM). Numerical techniques, like finite element method (FEM) have great potential in testing new, even the most sophisticated designs, according to their mechanical properties, i.e. strength or stiffness. However, due to different...
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Buckling of simplified models of silo with corrugated walls and vertical stiffeners
PublicationThe paper deals with buckling of cylindrical silos composed of corrugated sheets and vertical stiffeners (columns). Comprehensive finite element analyses were carried out for a perfect silo by means of a linear buckling approach. Corrugated walls were simulated as an equivalent orthotropic shell and vertical thin-walled columns as beam elements. Calculations for perfect silos with different numbers of columns made it possible to...
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Expedited constrained multi-objective aerodynamic shape optimization by means of physics-based surrogates
PublicationIn the paper, computationally efficient constrained multi-objective design optimization of transonic airfoil profiles is considered. Our methodology focuses on fixed-lift design aimed at finding the best possible trade-offs between the two objectives: minimization of the drag coefficient and maximization of the pitching moment. The algorithm presented here exploits the surrogate-based optimization principle, variable-fidelity computational...
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Cost-Efficient EM-Driven Size Reduction of Antenna Structures by Multi-Fidelity Simulation Models
PublicationDesign of antenna systems for emerging application areas such as the Internet of Things (IoT), fifth generation wireless communications (5G), or remote sensing, is a challenging endeavor. In addition to meeting stringent performance specifications concerning electrical and field properties, the structure has to maintain small physical dimensions. The latter normally requires searching for trade-off solutions because miniaturization...
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Międzysektorowa mobilność zatrudnienia oraz płac a efektywność rynku pracy.
PublicationCelem artykułu jest uzyskanie odpowiedzi na pytanie, czy ocenę efektywności funkcjonowania rynków pracy, rozumianej jako zdolność rynków do „oczyszczania się”, można przedstawić za pomocą analizy międzysektorowej mobilności płac oraz zatrudnienia. W połowie lat 90. XX wieku Paul Krugman dowodził, iż negatywne szoki gospodarcze skutkują w krajach europejskich wzrostem bezrobocia, natomiast w USA wzrostem rozpiętości płac. Tymczasem...
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Color transformation methods for dichromats
PublicationColor blindness is a serious perception problem. Suffering individuals cannot understand messages, which are carrying by many images, especially those, distributed by WWW. In this paper we are proposing three image processing methods to enhance image recognition and understanding by persons with dichromacy. Color difference image is introduced to represent color perception dissimilarity. Two color transformation methods are presented....
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Comparison of Doppler Effect Estimation Methods for MFSK Transmission in Multipath Hydroacoustic Channel
PublicationUnderwater wireless communication remains a challenging topic, particularly for applications such as wreck penetration where multipath and Doppler effects are very intense. These effects are becoming even more difficult to mitigate for fast data transmission systems that utilize wideband signals. Due to the low propagation speed of acoustic wave in the water, there is a significant difference between the Doppler shift for lower...
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Closing the gap – the opportunity for sustainability and smart transition in the Central and East Europe countries
PublicationFor almost half a century the countries of CEE were part of- or were remaining under the influence of- the Soviet Union what caused gaping difference in the starting line towards sustainability. Here the prefabricated concrete blocks of flats were being built at the scale unseen in the western countries. Those buildings, approximately a quarter of the residential market, are in a structurally sound condition to last another five...
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Low-frequency noise in Au-decorated graphene–Si Schottky barrier diode at selected ambient gases
PublicationWe report results of the current–voltage characteristics and low-frequency noise in Au nanoparticle (AuNP)-decorated graphene–Si Schottky barrier diodes. Measurements were conducted in ambient air with addition of either of two organic vapors, tetrahydrofuran [(CH2)4O; THF] and chloroform (CHCl3), as also during yellow light illumination (592nm), close to the measured particle plasmon polariton frequency of the Au nanoparticle...
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Optoelectronic properties of curved carbon systems
PublicationSystematic investigation of optoelectronic properties of curved carbon systems has been performed and the results have been compared with the representatives of flat carbon systems. Moreover, the application of third order dispersion corrected density functional tight binding method (with third order corrections of self-consistent charges) including Becke-Johnson dumping (DFTB3-D3(BJ)) has been validated in order to obtain reliable...
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Path Loss Analysis in Off-Body Channels in Indoor Environment
PublicationThis temporary document describes an analysis of path loss in off-body channels in an indoor environment. The influence of body orientation and on-body antenna placement on path loss in off-body communications as well as of different bodies has been investigated. Five static scenarios, six distances between body and antenna and eight body orientations were analysed; moreover, two dynamic scenarios were investigated. The smallest...
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Synthesis and properties of AxV2Al20 (A = Th, U, Np, Pu) ternary actinide aluminides
PublicationPolycrystalline samples of AxV2Al20 (A = Ce, Th, U, Np, Pu; 0.7 ≤ x ≤ 1.0) actinide intermetallics were synthesized using the arc-melting method. Crystal structure studies were performed by means of powder x-ray diffraction and the Rietveld refinement method. All studied compounds crystallize in the CeCr2Al20-type structure (space group Fd-3m, no. 227) with the actinoid and Ce atom located in the oversized icosahedral cage formed...
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Objective selection of minimum acceptable mesh refinement for EMC simulations
PublicationOptimization of computational electromagnetics (CEM) simulation models can be costly in both time and computing resources. Mesh refinement is a key parameter in determining the number of unknowns to be processed. In turn, this controls the time and memory required for a simulation. Hence, it is important to use only a mesh that is good enough for the objectives of the simulation, whether for direct handling of high-fidelity EM...
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Response of a New Low-Coherence Fabry-Perot Sensor to Hematocrit Levels in Human Blood
PublicationIn this paper, a low-coherence Fabry-Perot sensor with a spectrally measured signal processing response to the refractive index of liquids is presented. Optical fiber sensors are potentially capable of continuous measuring hematocrit levels in blood. Low-coherence Fabry-Perot interferometric sensors offer a robust solution, where information about the measurand is encoded in the full spectrum of light reflected from the sensing...
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Time-Domain Description of Point-Source Acoustic Wavefields as a Useful Approach in Ultrasonic Techniques
PublicationIn traditional acoustics, field problems are usually treated in the frequency domain, broadband fields being reduced to superposition of harmonic spectrum components. However, this approach is inherently acausal and it is known that in case of arbitrary signals, the distribution-based, time-domain description can be more effective. The present paper is an attempt to expand the time-domain linear systems formalism onto space problems...
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Memory and Imagination: Artwork as a Form of Testimony
PublicationAs the generation of witnesses is passing away and the testimonies of Shoah survivors are replaced by an inherited, culturally constructed memory - post-memory – art becomes a meaningful landmark in the landscape of memory. Although the narration of history - being the researchers’ discourse rather than an objective view - has been considered to a certain extent fictitious, the difference between real and fictional, between remembering...
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Nanotubular Oxide Layer Formed on Helix Surfaces of Dental Screw Implants
PublicationSurface modification is used to extend the life of implants. To increase the corrosion resistance and improve the biocompatibility of metal implant materials, oxidation of the Ti-13Nb- 13Zr titanium alloy was used. The samples used for the research had the shape of a helix with a metric thread, with their geometry imitating a dental implant. The oxide layer was produced by a standard electrochemical method in an environment of...
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The impact of the AC922 Architecture on Performance of Deep Neural Network Training
PublicationPractical deep learning applications require more and more computing power. New computing architectures emerge, specifically designed for the artificial intelligence applications, including the IBM Power System AC922. In this paper we confront an AC922 (8335-GTG) server equipped with 4 NVIDIA Volta V100 GPUs with selected deep neural network training applications, including four convolutional and one recurrent model. We report...
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Membrane distillation assisting food production processes of thermally sensitive food liquid items: a review
PublicationPhysical separation technologies have become important tool for processing in the current food manufacturing industries, especially for the products containing bioactive compounds thanks to their health benefits in costumers. As for the processing of bioactive food ingredients implies the implementation of integrated systems oriented to their separation, fractionation, and recovery. In this field, membrane distillation (MD), which...
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Methods of Determining Pressure Drop in Internal Channels of a Hydraulic Motor
PublicationIn this paper, new methods for determining the pressure drop in internal channels of a hydraulic motor are proposed and described. Mathematical models of pressure losses in internal channels have also been described. Experimental tests of the satellite motor were carried out according to one of the proposed methods. The tests were carried out for two liquids, i.e., water and mineral oil. Experimental studies have shown that at...
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Time-domain description of point-source acoustic wavefields as a useful approach in ultrasonic techniques
PublicationIn traditional acoustics, field problems are usually treated in the frequency domain, broadband fields being reduced to superposition of harmonic spectrum components. However, this approach is inherently acausal and it is known that in case of arbitrary signals, the distribution-based, time-domain description can be more effective. The present paper is an attempt to expand the time-domain linear systems formalism onto space problems...
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Perfect hashing tree automata
PublicationWe present an algorithm that computes a function that assigns consecutive integers to trees recognized by a deterministic, acyclic, finite-state, bottom-up tree automaton. Such function is called minimal perfect hashing. It can be used to identify trees recognized by the automaton. Its value may be seen as an index in some other data structures. We also present an algorithm for inverted hashing.Przedstawiamy algorytm, który oblicza...
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A complex variable fractional-delay FIR filter structure
PublicationW artykule wprowadzamy strukturę zespolonego filtru o skończonej odpowiedzi impulsowej (ang. finite impulse response - FIR) ze zmiennym opóźnieniem ułamkowym (ang. fractional delay - FD). Strukturę tę otrzymujemy na podstawie przestrajanego filtru FD FIR o współczynnikach rzeczywistych. Stanowi ona połączenie zbioru liniowo-fazowych filtrów FIR o współczynnikach stałych rzeczywistych i dwóch łańcuchów mnożąco-akumulujących, zawierających...
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TR-Based Antenna Design with Forward FD: The Effects of Step Size on the Optimization Performance
PublicationNumerical methods are important tools for design of modern antennas. Trust-region (TR) methods coupled with data-efficient surrogates based on finite differentiation (FD) represent a popular class of antenna design algorithms. However, TR performance is subject to FD setup, which is normally determined a priori based on rules-of-thumb. In this work, the effect of FD perturbations on the performance of TR-based design is evaluated...
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Numerical Determination of the Load-Bearing Capacity of a Perforated Thin-Walled Beam in a Structural System with a Steel Grating
PublicationThis article presents the results of numerical simulations of a structural system consisting of steel perforated thin-walled beams and a steel grating. The simulations were conducted using the finite element method. The analysis took into account physical and geometric nonlinearity as well as the contact between the steel grating and the beams. The main goal of the research was to develop load-bearing curves for the main beam in...
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The saga of a fish: from a survival guide to closing lemmas
PublicationIn the paper by D. Burago, S. Ivanov and A. Novikov, “A survival guide for feeble fish”, it has been shown that a fish with limited velocity can reach any point in the (possibly unbounded) ocean provided that the fluid velocity field is incompressible, bounded and has vanishing mean drift. This result extends some known global controllability theorems though being substantially nonconstructive. We give a fish a different recipe...
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Lattice-commensurate skyrmion texture in a centrosymmetric breathing kagome magnet
PublicationSkyrmion lattices (SkL) in centrosymmetric materials typically have a magnetic period on the nanometer-scale, so that the coupling between magnetic superstructures and the underlying crystal lattice cannot be neglected. We reveal the commensurate locking of a SkL to the atomic lattice in Gd3Ru4Al12 via high-resolution resonant elastic x-ray scattering (REXS). Weak easy-plane magnetic anisotropy, demonstrated here by a combination...
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Modelling of elastic wave propagation in a bolted joint using a thin layer of shell elements
PublicationThere are many mathematical models describing the propagation of elastic waves through the imperfect boundary of two media. They were successfully applied to modelling of high frequency bulk waves and their interaction with local defects. On the other hand, the existing literature models of bolted connections ignore the aspect of imperfect connection between elements. Therefore, this paper presents the concept of application of...
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Analysis of The Behavior of Foundations of Historical Buildings
PublicationThe article is devoted to the analysis of the behavior of the foundations of historic buildings. Some basic aspects of foundation engineering are discussed, with an emphasis placed on its development, applied techniques, and materials. Several different approaches and methods for the analysis of foundations of historical buildings are presented. A particular analysis has been focused on an example of a typical stone foundation...
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Application Isssues of the Semi-Markov Reliability Model
PublicationPredicting the reliability of marine internal combustion engines, for instance, is of particular importance, as it makes it possible to predict their future reliability states based on the information on the past states. Correct reliability prediction is a complex process which consists in processing empirical results obtained from operating practice, complemented by analytical considerations. The process of technical state changes...
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Ultrasonic Tomography of Brick Columns Based on FEM Calculations
PublicationUltrasonic tomography is one of the most developed method of non-destructive testing. Despite being used mainly in medicine, it is becoming more and more popular as a method for monitoring of structural elements. It allows to examine the internal structure and technical condition of the tested element. This paper investigates the influence of crosssectional geometry on an obtained tomographic image. Wave propagation signals were...
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Multimedia interface using head movements tracking
PublicationThe presented solution supports innovative ways of manipulating computer multimedia content, such as: static images, videos and music clips and others that can be browsed subsequently. The system requires a standard web camera that captures images of the user face. The core of the system is formed by a head movement analyzing algorithm that finds a user face and tracks head movements in real time. Head movements are tracked with...
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FEM modelling of stress and strain distribution in weld joints of steel sandwich panels
PublicationThe development of laser welding technology has enabled the mass production of thin-walled structures, including steel sandwich panels. The technology of joining plating panels with stiffeners by welding allows us to create joints with a specific geometry and material properties. In comparison with other types of joints, laser welds are characterized by their specific behaviour under cyclic load and, as a consequence, a different...
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Simplified method of applying loads to flat slab floor structural model
PublicationThe article analyses the impact of the live load position on the surface of a reinforced concrete flat slab floor of 32.0 m × 28.8 m. Four variants of a live load position are investigated: located on the entire concrete slab, set in a chessboard pattern, applied by bands and imposed separately in each of the slab panels. Conclusions are drawn upon differences in bending moments, the time of calculation and the size of output files....
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Discrete-continuous optimisation of an axial flow blood pump
PublicationThis paper presents results of discrete-continuous optimisation of an axial flow blood pump. Evolution Strategies (ES) are used as a global optimisation method in order to localise the optimal solution in relatively short time. The whole optimisation process is fully automated. This also applies to geometry modelling. Numerical simulations of the flow inside the pump is performed by means of the Reynolds-Average Navier-Stokes...
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LDFEM analysis of FDP auger installation in cohesive soil
PublicationThis paper deals with large deformation finite element (LDFE) preliminary modelling of Full Displacement Pile (FDP) installation in cohesive soil deposit located in Jazowa, Poland. The detailed FDP auger geometry is applied and the drilling process is modelled with full 3D Coupled Eulerian-Lagrangian (CEL) formulation. The total stress approach and elastic-perfectly plastic model with rate-dependent Mises plasticity is used. The...
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Knowledge Risks in the Sharing Economy
PublicationThis chapter presents a theoretical analysis of potential risks connected with knowledge that organizations operating in the sharing economy might potentially face. Nowadays, it can be stated that an increasing amount of individuals and organizations participate in sharing and exchanging data, information, and knowledge, as well as physical goods and services (Botsman & Rogers, 2011). The development of the sharing economy has...
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Influence of sheet/purlin fasteners spacing on shear flexibility of the diaphragm
PublicationThe paper presents the influence of sheet/purlin fasteners location (in reference to trapezoidal profile cross section) on shear flexibility of the cladding acting as a diaphragm. Analytical procedures were presented and their limitations were discussed. Next, selected schemes of fasteners location, known from engineering practice, but not included in European codes and recommendations, were analysed numerically in order to observe...
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Large deformation modelling of CPT probing in soft soil—pore water pressure analysis
PublicationThis paper presents the results of finite element modelling with Updated Lagrangian formulation of the Cone Penetration Test in soft soil deposit located in Jazowa, Poland. The numerical calculations are carried out for homogenous, normally consolidated, organic soil layer. The Modified Cam Clay constitutive model for soft soil and Coulomb model for interface are used. The study compares the registered pore water pressure distributions...
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The Discrete-Continuous, Global Optimisation of an Axial Flow Blood Pump
PublicationThis paper presents the results of the discrete-continuous optimisation of an axial flow blood pump. Differential evolution (DE) is used as a global optimisation method in order to localise the optimal solution in a relatively short time. The whole optimisation process is fully automated. This also applies to geometry modelling. Numerical simulations of the flow inside the pump are performed by means of the Reynolds-Average Navier-Stokes...
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On the current state of dovetail wall-corner joints in wooden Greek Catholic churches in Polish Subcarpathia with structural and sensitivity analyses
PublicationThis paper describes the current condition of some dovetail joints which form the wall corners of two Greek Catholic churches of wooden construction in Polish Subcarpathia. It also gives the historical background of the sacral architecture of that region. The two structures, which represent the same type of log corner joints are situated in Chotylub and Cewków. The buildings were examined e.g. for damage, wood moisture content,...
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Strongly anisotropic surface elasticity and antiplane surface waves
PublicationWithin the new model of surface elasticity, the propagation of anti-plane surface waves is discussed. For the proposed model, the surface strain energy depends on surface stretching and on changing of curvature along a preferred direction. From the continuum mechanics point of view, the model describes finite deformations of an elastic solid with an elastic membrane attached on its boundary reinforced by a family of aligned elastic...