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Wyniki wyszukiwania dla: modulacja amplitudy
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Investigation of long-range dependencies in the stochastic part of daily GPS solutions
PublikacjaThe long-range dependence (LRD) of the stochastic part of GPS-derived topocentric coordinates change (North, East, Up) results with relatively high autocorrelation values with a focus on self-similarity. One of the reasons for such self-similarity in the GPS time series are noises that are commonly recognised to prevail in the form of the flicker noise model. To prove the self-similarity of the stochastic part of GPS time series...
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Comparative study on fracture evolution in steel fibre and bar reinforced concrete beams using acoustic emission and digital image correlation techniques
PublikacjaIn recent decades, the demand for sustainable construction practices has increased, but raw materials such as reinforcing steel remain scarce. Therefore, steel fibres have emerged as a popular and sustainable choice in the construction industry, offering a cost-effective alternative to traditional steel bar reinforcement for both flatwork and elevated structures. The purpose of this study is therefore to compare the performance...
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Generalized adaptive notch smoothers for real-valued signals and systems
PublikacjaSystems with quasi-periodically varying coefficients can be tracked using the algorithms known as generalized adaptive notch filters (GANFs). GANF algorithms can be considered an extension, to the system case, of classical adaptive notch filters (ANFs). We show that estimation accuracy of the existing algorithms, as well as their robustness to the choice of design parameters, can be considerably improved by means of compensating...
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Modeling of a rock fall using the discrete element method and study of the seismic signal
PublikacjaMechanizm dużego spadającego bloku skalnego lub lawiny pozostaje nadal słabo rozpoznany zarówno w zakresie pęknięć jak i procesów propagacji. Jedynie ilościowe dane, które aktualnie są mierzone i uchwytne podczas spadania skały, zarejestrowane są jako sejsmiczne sygnały przez szereg sejsmografów. Właściwości sygnału (amplituda, trwanie, częstotliwość) są wyraźnie powiązane z cechami spadania (masa, wysokość spadania, odległość...
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Effect of waviness and roughness components on transverse profiles of turned surfaces
PublikacjaThis paper presents the authors method of simultaneous analysis of roughness and waviness irregularity components, with the aim of better defining the key qualities and characteristics.Periodical surface machining traces may be analyzed spectrally, with the irregularity's peaks and troughs being used to define the wave's amplitude.In this work the standard composition for filtering waviness and roughness components of a surface...
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Low cost microwave X-band generator
PublikacjaA low cost microwave X-band generator for educational purposes was designed and built. Its simple construction and user's interface makes it suitable for a student laboratory.The generator is based on a single frequency conversion concept. It uses a digitally tunable PLL chip for intermediate frequency generation and an active frequency multiplier for frequency conversion. The generator covers 9,7 - 11 GHz part of the X frequency...
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POSSIBILITY OF IDENTIFICATION OF TECHNICAL CONDITION OF BEARINGS FOR SELF-IGNITION ENGINES BY APPLICATION OF ACOUSTIC EMISSION AS A DIAGNOSTIC SIGNAL
PublikacjaThis paper presents the results of empirical studies where the acoustic emission (AE) method was applied to identify the technical condition of sliding surfaces of main and crank bearings for main diesel engines. The test results indicate that the measurements of the AE parameters allow the technical condition identification for bearings of this type. The results refer to the measurements of the parameters for AE generated in the...
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Positron scattering on molecular hydrogen: Analysis of experimental and theoretical uncertainties
PublikacjaExperiments performed in recent years on positron scattering from molecular hydrogen indicated a rise of the total cross section in the limit of zero energy, but essentially disagree on the amplitude of this rise. Mitroy and collaborators [J.-Y. Zhang et al., Phys. Rev. Lett. 103, 223202 (2009)] predicted a scattering length somewhat different from values deduced experimentally. Using a Markov chain Monte Carlo modified effective...
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Obliczenia niezawodności użytkowej kładek dla pieszych
PublikacjaW pracy zaprezentowano metodę obliczania niezawodności użytkowej kładek dla pieszych. Obciążenie pieszymi opisano definiując następujące zmienne losowe: amplitudę i częstość wymuszenia pieszego, jego prędkość, a także czas i miejsce pojawienia się na kładce. Zastosowano metodę Monte Carlo. Wygenerowane realizacje obciążenia stanowią zbiór danych wejściowych do obliczeń przeprowadzanych dowolnym programem stosującym metodę elementów...
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The influence of the local pipeline leak on water hammer properties
PublikacjaPrzedstawiono wyniki eksperymentalnej i numerycznej analizy zjawiska uderzenia hydraulicznego. Pomiary przeprowadzono dla przewodu MDPE o długości 36 m, w którym zamodelowano lokalną nieszczelność. W tym celu, w pewnej odległości od zaworu umieszczonego na końcu przewodu zainstalowano kształtki imitujące lokalny wyciek. Przeprowadzono analizę otrzymanych charakterystyk ciśnienia i wyznaczono parametry: okres oscylacji, amplitudę...
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Badania wykrywalności wad sztucznych w rurach impulsami akustycznymi, wzbudzanymi metodą magnetostrykcyjną
PublikacjaW artykule opisano wyniki badań nad oryginalną metodą detekcji wad w rurach, wykorzystującą efekty magnetosprężyste. Stanowi to kolejny etap badań rozwijania metody generacji impulsów magnetostrykcyjnych. W pracy przedstawiliśmy wyniki prac badawczych nad układem defektoskopu wykorzystującego metodę generacji akustycznych impulsów magnetostrykcyjnych. W badaniach wykorzystano trzy sztuczne wadyw rurze w kształcie otworów oraz nacięcia...
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Ocena wykrywalności modelowych wad wąskoszczelinowych metodą pomiaru przestrzennego rozkładu magnetycznego pola rozproszonego
PublikacjaWykazano, że metoda pomiaru natężenia metodą pomiaru natężenia pola rozproszonego (MPR) w polu szczątkowym umożliwia skuteczne wykrywanie zewnętrznych wad szczelinowych o głębokościach 0,2 mm przy długości 2,5 mm, oraz wad punktowych o średnicy mniejszej od 1mm i głębokości 0,3 mm. Zwiększenie poziomu namagnesowania (pomiary w pełnym polu magnetycznym) umożliwiło wykrywanie wad o znacznie mniejszych rozmiarach. Wykazano również,...
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Electron interactions with Bis(pentamethylcyclopentadienyl) titanium(IV) dichloride and difluoride
PublikacjaWe present a combined experimental and theoretical study of the interaction of electrons with Bis(pentamethylcyclopentadienyl)titanium(IV) dichloride (Cp∗2TiCl2) and difluoride (Cp∗2TiF2). We report the experimental measurements of partial cross sections for the dissociative electron attachment (DEA) and the electron ionization (EI) mass spectra of isolated molecules. Estimates of the absolute cross sections are done on the basis...
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Effect of manufacturing errors of the pad sliding surface on the performance of the hydrodynamic thrust bearing
PublikacjaIn the present study, investigation of the effect of manufacturing errors on the performance of large tilting pad thrust bearings has been performed, following a CFD-based Thermohydrodynamic analysis of a single pad. A 3D model has been generated, including the pad, the lubricant film and the corresponding part of the collar. The pad has been assumed to be deformed about the pivot point, due to thrust loading. Manufacturing errors...
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Compact 4 × 4 butler matrix with non‐standard phase differences for IoT applications
PublikacjaButler matrices represent a popular class of feeding networks for antenna arrays. Large dimensions and the lack of flexibility in terms of achievable output phase difference make conventional Butler structures of limited use for modern communication devices. In this work, a compact planar 4 × 4 matrix with non-standard relative phase shifts of –30º, 150º, –120º, and 60º has been proposed. The structure is designed to operate at...
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Expedited Design Closure of Antennas By Means Of Trust-Region-Based Adaptive Response Scaling
PublikacjaIn the letter, a reliable procedure for expedited design optimization of antenna structures by means of trust-region adaptive response scaling (TR-ARS) is proposed. The presented approach exploits two-level electromagnetic (EM) simulation models. A predicted high-fidelity model response is obtained by applying nonlinear frequency and amplitude correction to the low-fidelity model. The surrogate created this way is iteratively rebuilt...
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Fluctuation-Enhanced Sensing of Organic Vapors by Ink-Printed MoS2 Devices under UV Irradiation
PublikacjaThis work presents the results of fluctuationenhanced sensing (FES) of selected organic gases by MoS2 sensor fabricated via a simple ink printing method. We demonstrate that low-frequency noise measured under UV irradiation (275 nm) is more sensitive to different gases than measured in the dark. The noise at 1 Hz under UV light increased 3.3, 3.5, 1.6, and 2.9 times for chloroform, tetrahydrofuran, acetonitrile, and acetone ambiances, respectively....
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Method of Monitoring of the Grinding Process with Lapping Kinematics Using Audible Sound Analysis
PublikacjaUtilising microphones as audible sound sensors for monitoring a single-side grinding process with lapping kinematics is presented in the paper. The audible sound generated during grinding depended on the cutting properties of electroplated tools with D107 diamond grains and different thicknesses of the nickel bond. The tool wear affected the obtained technological effects such as material removal rate and the surface roughness...
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Wideband Off-Body Channel Characteristics with Dynamic User
PublikacjaThis paper presents the preliminary results of a dynamic off-body channel characterisation study, based on wideband measurements at 5.8 GHz in an indoor environment. The Channel Impulse Response (CIR) was measured for a scenario with the user approaching and departing from the off-body antenna. A CIR deconvolution procedure was performed jointly in two polarisations, and the received signal power, Cross-Polarisation Discrimination...
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Wykorzystanie zespolonej pulsacji chwilowej do ślepej synchronizacji symbolowej sygnałów QPSK
PublikacjaIzochronicznie nadawane i synchronicznie odbierane sygnały QPSK (z ang. Quadrature Phase-Shift Keying) dominują w dzisiejszej radiowej i przewodowej telekomunikacji cyfrowej. Poprawne działanie odbiornika sygnałów QPSK wymaga skomplikowanego systemu synchronizacji poszczególnych etapów odbioru. W skład systemu synchronizacji odbiornika wchodzi odtwarzanie częstotliwości i fazy sinusoidy (fali) nośnej oraz wyznaczanie chwil próbkowania...
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Diagnostyka łożysk silnika indukcyjnego z wykorzystaniem analizy prądu silnika metodą potrójnej kowariancji.
PublikacjaPrzedmiotem niniejszej rozprawy doktorskiej jest opracowanie nowej metody diagnostyki łożysk w silniku indukcyjnym opartej na pomiarach i analizie prądu zasilającego silnik. Ze względu na ciągłe doskonalenie i rozwój badao w kierunku metod prądowych, za pomocą których możliwa byłaby diagnostyka całego silnika, temat ten jest cały czas otwarty i jak najbardziej aktualny. Rozdział pierwszy zawiera wprowadzenie w zagadnienia będące...
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Error analysis for European IGS stations
PublikacjaEach of the GPS time series that describes the changes of topocentric components consists of a deterministic and a stochastic part, whose character influences the errors of the deterministic parameters. As to the uncertainties of reliable velocities of permanent satellite station systems, surveys that estimate and take into account any dependencies that may affect subsequent operational efficiency are very important. For this analysis,...
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Hydroacoustic ships berthing aid systems in Gdańsk north harbour
PublikacjaManewry dobijania statków do nabrzeży portowych są trudnymi operacjami, przy których należy uwzględniać m. in. na pływy, wiatry, widzialność, prędkość, masę statku, odległość od pirsu. Ewentualna kolizja z pirsem niesie poważne konsekwencje, szczególnie groźne dla wielkich statków a zwłaszcza tankowców. Referat prezentuje hydroakustyczne systemy kontroli manewrów statków wykonane przez zespół pracowników Katedry Systemów Elektroniki...
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Automated Detection of Sleep Apnea and Hypopnea Events Based on Robust Airflow Envelope Tracking in the Presence of Breathing Artifacts. - [IEEE JOURNAL OF BIOMEDICAL AND HEALTH INFORMATICS]
PublikacjaThe paper presents a new approach to detection of apnea/hypopnea events, in the presence of artifacts and breathing irregularities, from a single channel airflow record. The proposed algorithm, based on a robust envelope detector , identifies segments of signal affected by a high amplitude mo d- ulation corresponding to apnea/hypopnea events. It is show n that a robust airflow envelope - free of breathing artifacts - improves effectiveness...
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Drgania tarcz łożyskowych silników asynchronicznych wymuszane siłami elektromagnetycznymi
PublikacjaNa podstawie wyników badań akustycznych zwrócono uwagę na emitowanie hałasu przez tarcze łożyskowe silników i elektrycznych. Sklasyfikowano mechanizmy generowania drgań i hałasu w maszynach asynchronicznych, uwypuklając rolę wymuszeń elektromagnetycznych. Omówiono badania postaci drgań eksploatacyjnych kadłuba i tarczy łożyskowych metodą RORO, MORO i za pomocą lasera skanującego. Poddano analizie związki przyczynowo-skutkowe postaci...
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Analysis of unsteady flow forces on the thermowell of steam temperature sensor
PublikacjaIn this paper, 3D numerical analysis of unsteady flow forces acting on the measuring sheath of steam temperature is presented. According to that purpose, the CFD (Computation Fluid Dynamic [1]) approach has been used. The nonstationary of fluid acting on the measuring sheath such as: Strouhal frequency, amplitude of pressure, structure of vortex, peak of pressure, field of pressure, field of velocity etc. are studied analytically...
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Application of Structural Control Systems for the Cables of Cable-Stayed Bridges: State-of-the-Art and State-of-the-Practice
PublikacjaStay cables are one of the key elements of cable-stayed bridges and are characterized by lightweight, low inherent damping, and high flexibility. They are continuously subjected to small-to large-amplitude vibrations due to various types of dynamic loads that may, in the long term, cause fatigue and fracture problems for the cable system, and may eventually compromise the safety of cable-stayed bridges. Thus, several countermeasures...
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New Methods of Short-Circuit Current Limiting and Switching-off
PublikacjaPrzedstawiono wyniki badań symulacyjnych i eksperymentalnych hybrydowych indukcyjno-tyrystorowych ograniczników i wyłączników prądu zwarciowego. Impedancja dławika ogranicznika prądu jest wtrącana do obwodu zwarciowego dopiero w chwili, gdy prąd zwarciowy przekroczy wartość prądu wymuszonego w dławiku przez zewnętrzne źródło prądu. Ograniczanie dynamiki prądu zwarciowego jest bezzwłoczne. Układ nie generuje przepięć łączeniowych....
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Novel fast non-linear electrochemical impedance method for corrosion investigations
PublikacjaThe paper presents a novel approach to corrosion rate monitoring using non-linear electrochemical impedance spectroscopy. The authors propose a new variant of non-linear impedance measurement using amplitude-modulated multi-frequency ac perturbation signal. It allows shortening of measurement duration so it is possible to monitor corrosion rate of the systems experiencing rapid changes. In this way a limitation resulting from lack...
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NON-LOCAL VOLUMETRIC APPROACH TO ANALYSIS DEFECT'S SHAPE INFLUENCE ON SPECIMENS DURABILITY SUBJECTED TO BENDING AND TORSION
PublikacjaThe influence of defect features on fatigue behaviour is a complex trivial issue. Although the important advances over the last decades, the dialectical relationship between the defect orientation and durability is not clearly understood. The paper aims at studying the influence of the orientation of elliptical defects on the durability of samples made of C45 steel. Three types of samples with elliptical defects were subjected...
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On the use of the cumulative strain energy density for fatigue life assessment in advanced high-strength steels
PublikacjaIn this paper, the applicability of the cumulative strain energy density is explored as a fatigue indicator parameter for advanced high-strength steels subjected to strain-controlled conditions. Firstly, the cyclic stress-strain responses of nine steels, selected from three multiphase families, encompassing different elemental compositions and different heat treatment routes, were studied. Then, the predictive capabilities of the...
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Stress-driven nonlocal elasticity for nonlinear vibration characteristics of carbon/boron-nitride hetero-nanotube subject to magneto-thermal environment
PublikacjaStress-driven nonlocal theory of elasticity, in its differential form, is applied to investigate the nonlinear vibrational characteristics of a hetero-nanotube in magneto-thermal environment with the help of finite element method. In order to more precisely deal with the dynamic behavior of size-dependent nanotubes, a two-node beam element with six degrees-of freedom including the nodal values of the deflection, slope and curvature...
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High quality speech codec employing sines+noise+transients model
PublikacjaA method of high quality wideband speech signal representation employing sines+transients+noise model is presented. The need for a wideband speech coding approach as well as various methods for analysis and synthesis of sines, residual and transient states of speech signal is discussed. The perceptual criterion is applied in the proposed approach during encoding of sines amplitudes in order to reduce bandwidth requirements and...
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Signals Features Extraction in Radioisotope Liquid-Gas Flow Measurements using Autocorrelation Function
PublikacjaKnowledge of the two-phase flow structure is essential for the proper conduct of industrial processes. Description of liquid-gas flow regimes is possible by using of data analysis in time, frequency, or state-space domain. In this research studies, the autocorrelation function is applied for analysis of signals obtained for liquid-gas flow by use gamma-ray absorption. The experiments were carried out on the laboratory hydraulic...
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Programmable feedforward linearized CMOS OTA for fully differential continuous-time filter design
PublikacjaW artykule przedstawiono metodę linearyzacji wzmacniacza transkonduktancyjnego (OTA) CMOS z zastosowaniem sprzężenia w przód. Wzmacniacz zbudowany jest z użyciem prostych par różnicowych, wzmacniacza w pętli sprzężenia zwrotnego do samoregulacji transkonduktancji wzmacniaczy oraz liniowej rezystancji odniesienia (R). W wyniku uzyskano znaczną linaryzację charakterystyk przejściowych wzmacniacza OTA. Symulacje komputerowe SPICE...
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Zastosowanie metody elementów spektralych do modelowania zjawisk propagacji fal sprężystych dla celów diagnostyki
PublikacjaW artykule przedstawiono modelowanie propagacji fal sprężystych przy pomocy metody elementów spektralnych na bazie płytowych elementów Mindlina. Zaletą tego sformułowania jest diagonalizacja macierzy mas wynikająca ze zgodności rozkładu węzłów elementu wzorcowego i fizycznego z położeniem punktów całkowania kwadraturą Gaussa-Lobatto-Legendre'a. W pracy przedstawiono symulacje propagacji fal giętnych wzbudzonych na jednej krawędzi...
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Combined environmental testing device for picosatellites
PublikacjaAs access to space conditions becomes more available, both technically and economically, scientists’ interest in launching finer and more sophisticated experiments grows. To be qualified for launch, such experiments need to be carefully tested prior to the event. The tests should represent actual launch conditions as closely and in a detailed manner. Typical tests for payload include: vibration tests, thermal and vacuum tests,...
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Wyznaczenie trajektorii ruchu oraz parametrów geometrycznych zestawu trałowego podczas połowów pelagicznych
PublikacjaOpracowany, stosunkowo prosty model zestawu trałowego oraz program obliczeniowy pozwalają wyznaczyć trajektorię ruchu środka ciężkości zestawu trałowego w toni morskiej podczas jego trałowania w zależności od podstawowych parametrów pracy takich, jak: prędkość statku, prędkość wybierania lub wydawania lin przez wciągarki trałowe, długość wydanej liny, a także amplituda i okres przemieszczeń części rufowej statku. Umożliwia on także...
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EMPIRICAL ASSESMENT OF THE MAIN DRIVING SYSTEM OF THE CIRCULAR SAWING MACHINE
PublikacjaThe producers of panel saws tend to improve sawing accuracy and minimise a level of vibrations, to increase their competitiveness at the market. Mechanical vibrations in the main saw driving system, which level depend on a plethora independent factors, may really affect sawing accuracy and general machine tool vibrations. The objective of the research was to explore vibrations signals of the main spindle system, and to extract...
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Multichannel self-optimizing narrowband interference canceller
PublikacjaThe problem of cancellation of a nonstationary sinusoidal interference, acting at the output of an unknown multivariable linear stable plant, is considered. No reference signal is assumed to be available. The proposed feedback controller is a nontrivial extension of the SONIC (self-optimizing narrowband interference canceller) algorithm, developed earlier for single-input, single-output plants. The algorithm consists of two loops:...
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POSSIBILITY OF ASSESSMENT OF OPERATION OF SLIDING BEARINGS IN PISTON-CRANK MECHANISMS OF DIESEL ENGINES WITH REGARD TO LOAD AND TIME OF CORRECT WORK OF THE BEARINGS BY APPLYING ACOUSTIC EMISSION AS A DIAGNOSTIC SIGNAL
PublikacjaAbstract: The paper presents a possibility of determining (assessing) operation of sliding bearings with multilayer bushings in crank-piston mechanisms of diesel engines. Properties of load and wear, particularly fatigue and abrasive, are characterized in general. Acoustic emission as a diagnostic signal was proved to be useful for detection of the wear of sliding and barrier layers. Results of measurements of acoustic emission...
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Sea surface temperature distribution during upwelling along the Polish Baltic coast
PublikacjaAmong over 150 maps of sea surface temperature in the Polish Baltic coastal region derived from satellite data during the warm period of the year (April-October) in 2000-2002, 41 cases were noted where its distribution showed characteristic features indicating the occurrence of coastal upwelling. The fundamental parameters of range, probability of occurrence and temperature modification caused by water from deeper sea layers...
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DETERMINING THE TIME CONSTANT USING TWO METHODS AND DEFINING THE THERMOCOUPLE RESPONSE TO SINE EXCITATION OF GAS TEMPERATURE
PublikacjaThis paper describes the two methods of determining the time constant of type K thermocouple, for two construction solutions: the exposed weld and the mantle fillet weld. This is an important parameter indicating the response time of the thermocouple on the recorded signal. The first method consists of determining the value of τ in the way of numerical simulation of heat exchange between the thermocouple and the current of gas...
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Reliability assessment of an OVH HV power line truss transmission tower subjected to seismic loading
PublikacjaThe study focuses on the reliability of a transmission tower OS24 ON150 + 10, an element of an OVH HV power line, under seismic loading. In order to describe the seismic force, the real-life recording of the horizontal component of the El Centro earthquake was adopted. The amplitude and the period of this excitation are assumed random, their variation is described by Weibull distribution. The possible space state of the phenomenon...
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Optical flow method for measuring deformation of soil specimen subjected to torsional shearing
PublikacjaIn this study optical flow method was used for soil small deformation measurement in laboratory tests. The main objective was to observe how the deformation distributes along the whole height of cylindrical soil specimen subjected to torsional shearing (TS test). The experiments were conducted on dry non-cohesive soil specimens under two values of isotropic pressure. Specimens were loaded with low-amplitude cyclic torque to analyze...
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Oriented Gaussian beams for high-accuracy computation with accuracy control of X-ray propagation through a multi-lens system
PublikacjaA highly accurate method for calculating X-ray propagation is developed. Within this approach, the propagating wave is represented as a superposition of oriented Gaussian beams. The direction of wave propagation in each Gaussian beam agrees with the local direction of propagation of the X-ray wavefront. When calculating the propagation of X-ray waves through lenses, the thin lens approximation is applied. In this approximation,...
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Broadband Compact Single-Layer Magic-T Junction with Separation of DC Signals between All Ports
PublikacjaA novel structure for a four-port microstrip magic-T junction is presented. The device is composed of microstrip and slotline circuits etched onto two sides of a dielectric substrate. The device is extremely compact and occupies an area more than three times smaller than similar structures recently reported in the literature. The novelty of the device lies in the use of microstrip/slotline transitions for both input ports: summation...
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Failure Monitoring and Condition Assessment of Steel-Concrete Adhesive Connection Using Ultrasonic Waves
PublikacjaAdhesive bonding is increasingly being incorporated into civil engineering applications. Recently, the use of structural adhesives in steel-concrete composite systems is of particular interest. The aim of the study is an experimental investigation of the damage assessment of the connection between steel and concrete during mechanical degradation. Nine specimens consisted of a concrete cube and two adhesively bonded steel plates...
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Propagation of initially sawtooth periodic and impulsive signals in a quasi-isentropic magnetic gas
PublikacjaThe characteristics of propagation of sawtooth periodic and impulsive signals at a transducer are analytically studied in this work. A plasma under consideration is motionless and uniform at equilibrium, and its perturbations are described by a system of ideal magnetohydrodynamic equations. Some generic heating/cooling function, which in turn depends on equilibrium thermodynamic parameters, may destroy adiabaticity of a flow and...
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Friction-Induced Oscillations of a Non-Asbestos Organic Pin Sliding on a Steel Disc
PublikacjaFriction-induced oscillations result in deterioration of performance of disc brakes and are generally undesired. We conduct experimental study of friction-induced oscillations in a non-asbestos organic material / steel pair used in disc brakes of motor vehicles. The tests are done by use of a pin-on-disc machine which has the pin sample supported on a deformable beam. The adjustable friction parameters are the disc velocity, contact...