Wyniki wyszukiwania - BazTech

1

Mapy środowiska radiowego bazujące na PEM w sieciach FANET

Kryk Michał, Malon Krzysztof, Kelner Jan M.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2023

|

nr 4

289--292

PL

Mapa środowiska radiowego to pomocne narzędzie, które jest obecnie wykorzystywane do planowania sieci radiowych i zarządzania nimi. Znajdują one zastosowanie np. w sieciach radia kognitywnego lub mobilnych sieciach doraźnych. W przypadku sieci doraźnych z węzłami rozmieszczonymi na bezzałogowych statkach powietrznych, wykorzystanie dwuwymiarowych map jest niewystarczające. Ten artykuł koncentruje się na generowaniu trójwymiarowej mapy, która jest zbiorem map dwuwymiarowych zdefiniowanych dla dyskretnych wysokości nad poziomem gruntu lub morza. Każda taka mapa jest wyznaczana za pomocą metody równań parabolicznych, która pozwala określić tłumienia dróg propagacyjnych dla wielu profili terenu rozchodzących się promieniście od analizowanego węzła sieci. W artykule przedstawiono opracowany algorytm oraz przykładowe wyniki dla rozległego obszaru.

EN

A radio environment map is a helpful tool currently used to plan and manage radio networks. They are used, e.g., in cognitive radio networks or mobile ad-hoc networks. In the case of flying ad-hoc networks, the use of two dimensional maps is insufficient. This paper focuses on generating a three-dimensional map as a set of two-dimensional maps defined for discrete heights above ground or sea level. Each map is determined using the parabolic equation method, which allows for determining the path losses for many terrain profiles outgoing radially from the analyzed transmitting node. The paper presents the developed algorithm and exemplary results for a large area.

2

Wave propagation and free vibration of FG graphene platelets sandwich curved beam with auxetic core resting on viscoelastic foundation via DQM

Al Mukahal F. H. H., Sobhy Mohammed

Archives of Civil and Mechanical Engineering

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2022

|

Vol. 22, no. 1

art. no. e12, 2022

EN

A novel shear and normal deformations theory is presented in this article to illustrate the wave propagation and free vibration of three-layer sandwich curved beams subjected to elevated temperature and moisture environments and resting on viscoelastic foundation. The upper and lower layers are made of metal matrix reinforced with functionally graded (FG) graphene platelets (GPLs). While, the core layer is made of auxetic honeycomb structures. For the layers to be more bonded, the matrix of the face layers and the auxetic layer are both made of aluminum material. The volume fraction of GPLs is varied through the thickness of the face layers according to a layer-wise rule. The modified Halpin–Tsai model is used to describe the effective material properties of the face layers. Four types of GPLs distribution are considered in the present analysis. The differential quadrature method (DQM) is employed to discretize the equations of motion and then converted to a system of algebraic equations. This system can be solved to obtain the natural frequencies of the sandwich curved beams. Whereas, the wave dispersion relations are determined by solving the motion equations analytically. Convergence and comparison examples are presented to adjust and validate the present solution. In addition, comprehensive parametric studies are performed to investigate the effects of the weight fraction of GPLs, temperature, moisture concentrations, core thickness, boundary conditions, and viscoelastic foundation stiffness on the natural frequency, wave frequency and phase velocity of the honeycomb sandwich curved beams.

3

Analysis of the harmful influence of parasiteismic vibrations using the example of a failure in the building structure of a school gymnasium

Liszewski Wiesław

Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo

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2021

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Z. 27 (177)

152-157

EN

This article describes, based on the failure of a public utility building structure, the issues related to the destructive impact of vibrations on the ground in connection with the load-bearing structure of the facility. An external source of wave propagation was identified, located in the immediate vicinity of the analyzed building. Additionally, errors in the interpretation of the behavior of the structure during its operation were presented by performing ineffective construction works related to the attempt to strengthen the ground on which the school sports hall was directly erected. On the basis of the analysis of archival materials and additional tests, the necessary scope of repair works necessary to be performed on the site was determined, along with guidelines for the implementation of the diaphragm in the form of a ground vibro-isolating screen, aimed at minimizing the impact of parasiteismic impacts on the public building.

PL

Na przykładzie awarii konstrukcji budynku użyteczności publicznej, opisano problematykę związaną z destrukcyjnym wpływem drgań na podłoże gruntowe w powiązaniu z ustrojem nośnym obiektu. Ustalono zewnętrzne źródło propagacji fal, zlokalizowane w bezpośrednim sąsiedztwie analizowanego budynku. Dodatkowo przedstawiono błędy w interpretacji zachowania konstrukcji w trakcie jej eksploatacji, poprzez wykonywanie nieskutecznych prac budowlanych związanych z próbą wzmocnieniem podłoża gruntowego, na którym w sposób bezpośredni posadowiono przyszkolną salę sportową. Na podstawie przeprowadzonej analizy materiałów archiwalnych oraz dodatkowych badań określono niezbędny zakres robót naprawczych, koniecznych do wykonania na obiekcie wraz z wytycznymi do realizacji przepony w formie gruntowego ekranu wibroizolacyjnego, mającego na celu zminimalizowanie wpływu oddziaływań parasejsmicznych na budynek użyteczności publicznej.

4

Studies on the effect of kinematic viscosity on electron-acoustic cylindrical and spherical solitary waves in a plasma with trapped electrons

Roy Subrata, Saha Sandip, Raut Santanu, Das Apurba Narayan

Journal of Applied Mathematics and Computational Mechanics

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2021

|

Vol. 20, nr 2

65--76

EN

In this article, using the standard reductive perturbation technique (RPT) to the basic governing equations for plasma comprising stationary ions, cold electrons and hot electrons abiding by vortex-like distribution, nonplanar Schamel Burger (NSB) equations is derived. In order to study the propagating properties of Electron acoustic (EA), progressive wave solution is obtained by employing the weighted residual method (WRM). Most of the observations of the EA wave are limited to the plasma environment where the effects of viscosity, collisions, ion streaming velocity are totally neglected. In our present observation, propagation of EA waves in a viscous plasma is described considering a weak damping (by adding a Burgers term) due to the inner particle collision and viscosity. Special attention has been given to study the impact of the other physical parameters in wave propagation in the framework of the Schamel Burgers medium.

5

Evaluation of the resistance of steel–concrete adhesive connection in reinforced concrete beams using guided wave propagation

Zima B., Kędra R.

Archives of Civil and Mechanical Engineering

|

2020

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Vol. 20, no. 1

1--13

EN

The development of the nondestructive diagnostic methods is of significant importance in the last decades. A special attention is paid to diagnostics of reinforced concrete structures, which are very popular in the civil engineering field. A possible use of the guided waves in the estimation of the resistance of steel–concrete adhesive connection is studied in the following paper. The relationships relating adhesive connection resistance and wave propagation characteristics (wave velocity and the time of flight) have been derived and experimentally verified during pull-out tests conducted on a number of reinforced concrete beams varying in the debonding area. The pull-out tests were also monitored ultrasonically. On the basis of the results in the form of the time-domain signals, the theoretical load-carrying capacities of the pulled-out bars have been calculated and compared with the exact experimentally determined values. The high agreement of the results obtained proved the correctness of the developed method. Moreover, the signals registered during pull-out tests allowed to observe the changes of the wave velocity induced by the deterioration of the adhesive connection.

6

Investigation of waves generated in transversely isotropic micropolar generalized thermoelastic half space under temperature dependent properties

Gupta R. R., Gupta R. R.

International Journal of Applied Mechanics and Engineering

|

2019

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Vol. 24, no. 4

53--65

EN

The present study deals with the propagation of waves in a transversely isotropic micropolar generalized thermoelastic material possessing temperature dependent elastic properties. After developing the solution for LS, GL and CT theory, the phase velocities and attenuation quality factor have been obtained. The expressions for amplitudes of stresses, displacements, microratation and temperature distribution have been derived and computed numerically. The numerically evaluated results have been plotted graphically. Some particular cases of interest have also been obtained.

7

Modelowanie tłumienia sygnału przy transmisji do wnętrza budynków

Lewicki F., Ługowski A., Kinal G., Lesiak S.A., Zagórda G.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2018

|

nr 6

242--245, CD

PL

W referacie przedstawiono wynik prac nad modelem tłumienia sygnału transmitowanego z zewnątrz budynku do wnętrza budynku (ang. building entry loss – BEL). Zaproponowany przez Orange Polska model BEL został wykorzystany w Zaleceniu ITU-R P.2109 do wyznaczania wartości BEL jakie nie będą przekroczone w 50% miejsc. Model powstał na podstawie wyników pomiarów dla budynków tradycyjnych i budynków nowoczesnych o zwiększonym tłumieniu sygnałów.

EN

In this paper the results of the development of the building entry loss (BEL) model. This model was proposed by Orange Polska and accepted as a part of the ITUR Recommendation P.2109 “„Prediction of building entry loss” for the evaluation of the BEL value that is not exceeded in the 50% of locations. This model based on the results of measurements in traditional and thermally efficient buildings.

8

Komputerowe wspomaganie analizy propagacji fali w betonowych konstrukcjach sprężonych

Krzyżyński T., Maciejewski I., Szczurowski K.

Materiały Budowlane

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2018

|

nr 11

24--26

PL

Wykorzystywane w praktyce metody oceny stanu konstrukcji sprężonych, które mogą występować w konstrukcjach betonowych, polegają na wykryciu zarysowań, wtrąceń, korozji lub innych uszkodzeń. Na ogół metody te są ukierunkowane na znalezienie miejsca ich występowania. Proponowane w artykule podejście do oceny stanu elementów sprężonych polega na obserwacji charakterystyk dynamicznych elementów konstrukcji pod wpływem zmian w rozkładzie naprężeń. Przedstawiono metodę bazującą na analizie propagacji fali w betonowych konstrukcjach sprężonych na potrzeby predykcji stanu naprężenia w przekrojach poprzecznych belki. Badania eksperymentalne poparte są symulacjami komputerowymi z wykorzystaniem Metody Elementów Skończonych.

EN

Used in practice methods of prestressed concrete state identification which can occurred in the structures base at a detection of cracks, inclusions, corrosion or other small damages. Mostly they are targeted at detecting of their localization. An alternative approach consisting an observation of changes in dynamical characteristics of construction elements, due to a change in a structure of internal stresses. In the present paper an analysis of wave propagation in concrete prestressed structures for needs of stress state prediction in beam cross-sections is presented. Experimental approach is aided by means of computer simulations with a use of Finite Element Method.

9

Propagation of torsional surface waves in a nonhomogeneous half-space with circular irregularity in free surface

Sethi M., Sharma A. K., Sharma A.

International Journal of Applied Mechanics and Engineering

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2018

|

Vol. 23, no. 4

929--939

EN

The present paper studies the effect of circular regularity on propagation of torsional surface waves in an elastic non-homogeneous half-space. Both rigidity and density of the half-space are assumed to vary inversely linearly with depth. Separation of variable method has been used to get the analytical solutions for the dispersion equation of the torsional surface waves. Also, the effects of non-homogeneity and irregularity on the phase velocity of torsional surface waves have shown graphically.

10

Sun transits in geo satellite systems in the aspect of radio waves propagation

Wilk-Jakubowski J. Ł.

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2018

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T. 8, nr 4

56--59

EN

The article includes description of process of Sun transits, including indispensable information on the parameters employed to show their impact on these phenomena. On this basis the date, the start time and the end time and the duration time of Sun transits could be presented for a given location. The main considerations are pertinent to propagation studies. The part of results connected with Sun transits for the limited frequencies of Ku band (downlink) in satellite systems, depending on the antennae, is presented in this article.

PL

Artykuł zawiera opis zjawiska influencji słonecznych, ukazując niezbędne informacje na temat zastosowanych parametrów, aby przedstawić ich wpływ na te zdarzenia. Na tej podstawie data, czasy początku i końca oraz czas trwania influencji słonecznych mogą zostać określone dla danej lokalizacji. Rozważania dotyczą badań propagacyjnych. W artykule dla łącza downlink zamieszczono część wyników, w zależności od zastosowanych anten, dla granicznych częstotliwości pasma Ku powszechnie wykorzystywanego w łączności satelitarnej.

11

Comments on "Archives of Civil and Mechanical Engineering 17 (2017) 564–573"

Pantokratoras A.

Archives of Civil and Mechanical Engineering

|

2018

|

Vol. 18, no. 4

1643--1644

EN

The present comment concerns some doubtful results included in the above paper.

12

Separation of split shear waves based on a hodogram analysis of HTI media

Yang Y., Lu J., Wang Y.

Acta Geophysica

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2018

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Vol. 66, no. 4

643--658

EN

Although the shear-wave birefringence phenomenon affects the imaging of converted shear waves, it also provides a considerable amount of information on subsurface fracture development. Therefore, it is significant to separate split shear waves before seismic interpretation and reservoir prediction. In this paper, we propose a new method of split shear waves separation based on the polarization directions derived from hodogram analysis. Through the hodogram analysis, we find that the split shear-wave particle motions are within the range of a specific and fixed rectangle, which have relations with the fracture azimuth in strata. In addition, we found that a couple of split shear waves can only be fitted to the unique trajectory rectangle through the theoretical derivation. Based on this, we establish the trajectory rectangle through the wave vector calculation and calculate the fracture azimuth according to the fact that the one edge of the trajectory rectangle is along or perpendicular to the fracture azimuth. Synthetic data analysis shows that the calculation accuracy of fracture azimuth under the constraint of trajectory rectangle is less affected by the time delay between split shear waves than using the method of eigenvector–eigenvalue decomposition (EED). Therefore, we can obtain better results for separation of split shear waves using our method than using EED. Eventually, we propose an approach of layer stripping to deal with the problem that shear wave split several times due to the situation that different strata have different fracture azimuths. Synthetic data test indicates that our method can achieve higher calculation efficiency and faster convergence speed than the conventional eigenvector–eigenvalue decomposition method, even though the data are of a low signal-to-noise ratio. Moreover, field data applications show the effectiveness and potential of our method.

13

Numerical modeling of Gaussian beam propagation and diffraction in inhomogeneous media based on the complex eikonal equation

Huang X., Sun H.

Acta Geophysica

|

2018

|

Vol. 66, no. 4

497--508

EN

Gaussian beam is an important complex geometrical optical technology for modeling seismic wave propagation and diffraction in the subsurface with complex geological structure. Current methods for Gaussian beam modeling rely on the dynamic ray tracing and the evanescent wave tracking. However, the dynamic ray tracing method is based on the paraxial ray approximation and the evanescent wave tracking method cannot describe strongly evanescent fields. This leads to inaccuracy of the computed wave fields in the region with a strong inhomogeneous medium. To address this problem, we compute Gaussian beam wave fields using the complex phase by directly solving the complex eikonal equation. In this method, the fast marching method, which is widely used for phase calculation, is combined with Gauss–Newton optimization algorithm to obtain the complex phase at the regular grid points. The main theoretical challenge in combination of this method with Gaussian beam modeling is to address the irregular boundary near the curved central ray. To cope with this challenge, we present the non-uniform finite difference operator and a modified fast marching method. The numerical results confirm the proposed approach.

14

The modification of the dynamic properties of cohesive soil resulting from triaxial consolidation

Kogut J., Zięba J.

Technical Transactions

|

2017

|

Vol. 9(114)

75--89

EN

This paper describes the laboratory examination of the dynamic parameters of cohesive soil together with an analysis of these parameters using artificial intelligence. The analysis yielded the propagation velocity of shear wave Vs and the dynamic Kirchhoff modulus G obtained during the soil tests in the triaxial stress apparatus. The investigation was conducted using bender elements. The artificial neural networks trained on data obtained from the test were used for the further analysis.

PL

Artykuł łączy ze sobą badania laboratoryjne parametrów dynamicznych gruntu spoistego wraz z ich analizą z użyciem metod sztucznej inteligencji. Rezultatami analizy są wartości prędkości propagacji fali ścinającej Vs oraz dynamicznego moduł Kirchhoffa G uzyskane podczas badania gruntu w aparacie trójosiowego ściskania. Do otrzymania tych parametrów posłużyło wykorzystanie elementów bender. Do analizy użyto sztucznych sieci neuronowych uczonych na danych pozyskanych z badań.

15

Propozycja wyznaczania wybranych współczynników transportu wilgoci w materiałach ceramicznych porowatych na podstawie pomiarów ultradźwiękowych

Kucharczyk A.

Inżynieria i Budownictwo

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2017

|

R. 73, nr 2

100--102

PL

Przedstawiono metodę wyznaczania wybranych współczynników opisujących proces transportu wilgoci z wykorzystaniem pomiarów ultradźwiękowych ceramiki budowalnej. W tym celu zaproponowano model propagacji fali ultradźwiękowej i wykonano pomiary czasu propagacji podłużnej fali ultradźwiękowej.

EN

In the paper the method of determining the selected moisture transport coefficients using ultrasonic measurements was presented. For this purpose a model of the wave propagation was proposed and the ultrasonic measurements of time propagation of longitudinal wave were made.

16

Mathematical modeling of torsional surface wave propagation in a non-homogeneous transverse isotropic elastic solid semi-infinite medium under a layer

Sethi M., Sharma A., Vasishth A.

International Journal of Applied Mechanics and Engineering

|

2017

|

Vol. 22, no. 2

415--426

EN

The present paper deals with the mathematical modeling of the propagation of torsional surface waves in a non-homogeneous transverse isotropic elastic half-space under a rigid layer. Both rigidities and density of the half-space are assumed to vary inversely linearly with depth. Separation of variable method has been used to get the analytical solutions for the dispersion equation of the torsional surface waves. Also, the effects of nonhomogeneities on the phase velocity of torsional surface waves have been shown graphically. Also, dispersion equations have been derived for some particular cases, which are in complete agreement with some classical results.

17

The measurement of selected soil parameters of former open pit mine with the use of triaxial stress apparatus

Kogut J. P., Zięba J.

Czasopismo Inżynierii Lądowej, Środowiska i Architektury / Journal of Civil Engineering, Environment and Architecture

|

2017

|

z. 64, nr 1

97--104

EN

Identification of geotechnical soil conditions often requires execution of laboratory tests, especially if you want to measure dynamic parameters of the soil. At present, the triaxial shear apparatus is widely applied in determination of the parameters of the soil. On the basis of the soil samples analysis, the examination results provide a wide range of data from basic performance parameters, e.g. internal friction angle and cohesion, to most complex ones like Young’s modulus permanent side effective stress of water samples. Furthermore, the Soil Structure Interaction Laboratory of Cracow University of Technology, has carried out the measurements of propagation of shear waves velocity with the use of bender elements tests. This work presents geotechnical conditions and the analysis of the results, which might be found useful to determine the transportation load parameters of designed S-7 and S-52 routes, as well as overall impact on soil/structure and surrounding areas located over the former clay open-pit mine. The landslides existing in the vicinity of the mine have prompted the authors to take that action.

PL

Rozpoznanie warunków geotechnicznych podłoża gruntowego wykonywanego w celu ustalenia parametrów dynamicznych podłoża często wymaga wykonania badań laboratoryjnych. Obecnie jednym z najbardziej popularnych sposobów określania parametrów gruntów jest użycie aparatu trójosiowego ściskania. Wynikami badania próbki gruntowej w aparacie trójosiowym mogą być oprócz podstawowych parametrów wytrzymałościowych czyli kąta tarcia wewnętrznego i spójności, parametry takie jak moduł odkształcenia liniowego przy stałym bocznym naprężeniu efektywnym w próbce w warunkach z odpływem, jak i bez odpływu wody z próbki. Dodatkowo w laboratorium Katedry Współdziałania Budowli z Podłożem Politechniki Krakowskiej, przeprowadzano badania określenia prędkości fali poprzecznej przy wykorzystaniu elementów bender. W pracy przedstawiono warunki geotechniczne, a następnie podsumowano wyniki badań, które w przyszłości posłużą autorom do określenia wpływu obciążeń komunikacyjnych trasy S-7 i S-52 na podłoże gruntowe terenu kopalni i ich okolic. Analiza ta wynika z występowania kilku osuwisk w bezpośredniej otoczeniu kopalni.

18

A novel formulation of 3D spectral element for wave propagation in reinforced concrete

Rucka M., Witkowski W., Chróścielewski J., Burzyński S.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2017

|

Vol. 65, nr 6

805--813

EN

The paper deals with numerical simulations of wave propagation in reinforced concrete for damage detection purposes. A novel formulation of a 3D spectral element was proposed. The reinforcement modelled as the truss spectral element was embedded in the 3D solid spectral finite element. Numerical simulations have been conducted on cuboid concrete specimens reinforced with two steel bars. Different degradation models were considered to study the real behaviour of bended beams.

19

Propagation of a thermoelastic wave in a half-space of a homogeneous isotropic material subjected to the effect of gravity field

Abd-Alla A. M., Abo-Dahab S. M., Alotaibi H. A.

Archives of Civil and Mechanical Engineering

|

2017

|

Vol. 17, no. 3

564--573

EN

The propagation of thermoelastic waves in a homogeneous, isotropic elastic semi-infinite space is subjected to a gravitational field, which is at temperature T0 initially, and whose boundary surface is subjected to heat source and load moving with finite velocity. Temperature and stress distribution occurring due to heating or cooling and have been determined using certain boundary conditions. Numerical results have been given and illustrated graphically in each case considered. The results indicate that the effect of gravity field is very pronounced. Comparison is made with the results predicted by the theory of thermoelasticity in the absence of gravity. The results indicate that the effect of the gravity is very pronounced.

20

Propagacja fal podłużnych w ośrodkach anizotropowych na przykładzie struktury uskokowej horstu

Kostecki A., Żuławiński K.

Prace Naukowe Instytutu Nafty i Gazu

|

2016

|

nr 209 wyd. konferencyjne

211--221

PL

W artykule przedstawiono podstawy teoretyczne modelowania „w przód” w ośrodkach anizotropowych typu TI (Transverse Isotropy) zilustrowane przykładami propagacji fal podłużnych w strefie uskokowej. Te same przykłady posłużyły do wykonania wstecznej propagacji, tj. migracji zero-offset, umożliwiającej odwzorowanie założonego ośrodka.

EN

In this paper, we present fundamentals of compressional waves forward modeling in anisotropic media of TI (Transverse Isotropy) type on some examples of these waves propagation. Back propagation i.e. zero-offset migration was used to image the trust zone.