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Wyszukujesz frazę "time domain" wg kryterium: Temat


Tytuł:
Existence and smoothing effects of the initial-boundary value problem for ∂u/∂t−Δσ(u) = 0 in time-dependent domains
Autorzy:
Nakao, Mitsuhiro
Powiązania:
https://bibliotekanauki.pl/articles/29519532.pdf
Data publikacji:
2023
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
quasilinear parabolic equation
time-dependent domain
smoothing effect
Opis:
We show the existence, smoothing effects and decay properties of solutions to the initial-boundary value problem for a generalized porous medium type parabolic equations of the form $ u_t − Δσ(u) = 0 $ in $ Q(0, T) $ with the initial and boundary conditions $ u(0) = u0 $ and $ u(t)|_{∂Ω(t)} = 0 $, where Ω(t) is a bounded domain in $ R^N $ for each t ≥ 0 and $ Q(0,T) = \bigcup_{0<t<T} \Omega(t) \times {t}, T>0 $. Our class of $ σ(u) $ includes $ σ(u) = |u|^m u $, $ σ(u) = u log(1 + |u|^m), 0 ≤ m ≤ 2, $ and $ σ(u) |u|^m u// \sqrt{1+|u|^2} $, $ 1 ≤ m ≤ 2 $ etc. We derive precise estimates for $ ||u(t)||_{Ω(t),∞} $ and $ ||∇σ(u(t))||_{Ω(t),2}^2, t > 0 $, depending on $ ||u_0||_{Ω(0),r} $ and the movement of $ ∂Ω(t) $.
Źródło:
Opuscula Mathematica; 2023, 43, 5; 703-734
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental study of nano-composite materials on vibration responses
Autorzy:
Mobark, Haidal Faisal Helal
Fahdel, Essam Z.
Hussein, Mustafa Turki
Mohamad, Barhm
Powiązania:
https://bibliotekanauki.pl/articles/13800132.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN
Tematy:
nanocomposite
time domain
mechanical properties
cantilever beam
finite element method
nanokompozyt
właściwości mechaniczne
metoda elementów skończonych
belka wspornikowa
Opis:
This paper present of experimental and numerical study of nano Al2O3 cantilever beam for forced vibration, addressing an unexplored area in the existing literature. The proposed nano composite cantilever beam is modeled with hole and crack. The study is based on history loading calculation and composite morphology a global parameter, the transverse crack in nano composite cantilever beam was studied and analyzed experimentally using a four-channel dynamic signal acquisition (NI 9234) module for making high-accuracy measurements and its ideal for vibration applications. The relationship between the dispersion and interaction of the alumina nanoparticles within the cantilever beam and morphology of the solid, hole and crack composite has been identified. Furthermore, the influence of particles Al2O3 at different concentrations (0%, 1%, 3% and 4%) have been studied respectively. Supporting results proved that the crack and hole depth increases with increases of history loading. Nanoparticles dispersed within the specimen can increase energy dissipation during vibration, leading to improved damping characteristics. For future work, it is recommended to utilize statistical frequency domain input, such as Power Spectral Density (PSD), for assessing the structural response instead of employing time history loading.
Źródło:
Diagnostyka; 2023, 24, 3; art. no. 2023312
1641-6414
2449-5220
Pojawia się w:
Diagnostyka
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fabrication of a test rig for gearbox fault simulation and diagnosis
Autorzy:
Dubaish, Asaad Abdulhussein
Jaber, Alaa Abdulhady
Powiązania:
https://bibliotekanauki.pl/articles/2203635.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN
Tematy:
fault detection
vibration analysis
time-domain signal
gearbox
LabVIEW
wykrywanie uszkodzeń
analiza drgań
przekładnia
Opis:
Gearboxes are one of the most important and widely exposed to different types of faults in machines. Therefore, manufacturers and researchers have made significant efforts to develop different fault detection and diagnostic approaches for gearboxes. However, many research foundations, such as universities, are currently working on developing different gearbox test rigs to understand the failure mechanisms in gearboxes. As a result, in this article, a gearbox testing rig was proposed and fabricated to evaluate gear performance under lowspeed working conditions. It describes the primary mechanical apparatus and the measurement tools used during the experimental analysis of a multistage gearbox transmission system. The data-gathering equipment used to acquire the observed vibration data is also discussed. LabVIEW software was used to build a data acquisition platform using an accelerometer and a NI DAQ device. Then different vibration tests were conducted under different operating conditions, when the gearbox was healthy and then faulty, on this test rig, and the gathered vibration data were analyzed based on time domain signal analysis. The preliminary results are promising and open the horizon for simulating different gearbox test scenarios.
Źródło:
Diagnostyka; 2023, 24, 2; art. no. 2023204
1641-6414
2449-5220
Pojawia się w:
Diagnostyka
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of spatial distribution and the type of material on the occurrence of bandgaps in phononic crystals
Autorzy:
Garus, Sebastian
Sochacki, Wojciech
Kwiatoń, Paweł
Nabiałek, Marcin
Petrů, Jana
Kubanek, Mariusz
Powiązania:
https://bibliotekanauki.pl/articles/27311439.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
finite difference time domain
band gap
phononic crystal
mechanical waves
propagation
domena czasowa różnic skończonych
kryształ fononiczny
fale mechaniczne
propagacja
przerwa energetyczna
Opis:
The study investigated the effect of the fill factor, lattice constant, and the shape and type of meta-atom material on the reduction of mechanical wave transmission in quasi-two-dimensional phononic structures. A finite difference algorithm in the time domain was used for the analysis, and the obtained time series were converted into the frequency domain using the discrete Fourier transform. The use of materials with large differences in acoustic impedance allowed to determine the influence of the meta-atom material on the propagation of the mechanical wave.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2023, 71, 3; art. no. e144609
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical simulations and optimization of highly sensitive biosensor for cancer cell detection
Autorzy:
El Mouncharih, Abdelkarim
Takassa, Rabi
Farkad, Omar
Tchenka, Abdelaziz
Ibnouelghazi, El Alami
Abouelaoualim, Driss
Powiązania:
https://bibliotekanauki.pl/articles/27310106.pdf
Data publikacji:
2023
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
refractive index sensor
sensitivity
cancer cell
photonic crystal
finite difference time domain
FDTD
Opis:
In this work, using the two-dimensional finite difference time domain method, we are theoretically studying the optical properties of a two-dimensional photonic crystal biosensor based on silicon rods arranged as a square structure in an air bottom with two waveguides and a nanocavity. For this purpose, six different cells are infiltrated into the point defect. These six cells are Jurkat, HeLa, PC-12, MDA-MB-231, MCF-7, and basal cells. As a result, we have successfully detected cancer and benign cases of these cells through resonance peaks in the transmission spectrum. We evaluated the sensitivity, quality factor, detection limit, and figure of merit at different values for sensing region radius for optimization purposes. We report that we observed the maximum sensitivity of 1350 nm/RIU at 0.15 μm for the basal cell. Finally, the proposed biosensor can be a miniaturized structure with extreme sensitivity in cancer cell detection models.
Źródło:
Optica Applicata; 2023, 53, 3; 407--418
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rapid design exploration of low pass highly efficient single loop single bit sigma delta (ΣΔ) modulators
Autorzy:
Krishna, S. Vamsee
Reddy, P. Sudhakara
Reddy, S. Chandra Mohan
Powiązania:
https://bibliotekanauki.pl/articles/38699542.pdf
Data publikacji:
2023
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
sigma delta modulator
single loop
time domain
virtual instrument
biomedical application
modulator sigma delta
pojedyncza pętla
dziedzina czasu
instrument wirtualny
zastosowanie biomedyczne
Opis:
A rapid design and verification of sigma delta modulators are presented at the systemlevel with high accuracy and computational efficiency. Sigma delta analog to digital converters showcased an excellent choice for low bandwidth applications from near DC tohigh bandwidth standard 5G applications. The conceptualization of the graphical userinterface (GUI) in the efficient selection of integrator weights has been proposed, whichsolves various tradeoffs between various abstraction levels. The sigma delta modulator of the 5th order is designed and simulated using the proposed design methodology of calculating integrator weights for targeted specifications. The efficiency of design explorationand optimum selection of integrator coefficients has been investigated on single loop architectures. Power and performance of the selected modulator has been verified in the timedomain behavioral simulation. The discrete time circuit technique has been adopted fordesign of distributed feedback, feed forward architectures and comparison of performancemetrics done between selected architectures. A huge design space is computed for the bestdesign parameters that offers ultra-low power and high performance. The proposed virtual instruments supported the methodology for designing delta sigma modulators at thesystem level achieving SNDR of 122 dB over a bandwidth of 5 kHz at a clock frequencyof 1 MHz.
Źródło:
Computer Assisted Methods in Engineering and Science; 2023, 30, 1; 27-39
2299-3649
Pojawia się w:
Computer Assisted Methods in Engineering and Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on Chinese Speech Intelligibility Under Different Low-Frequency Characteristics of Reverberation Time Using a Hybrid Method
Autorzy:
Huang, Wuqiong
Peng, Jianxin
Xie, Tinghui
Powiązania:
https://bibliotekanauki.pl/articles/31339871.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
low frequency
speech intelligibility
classroom
finite-difference time-domain method
Opis:
Reverberation time (RT) is an important indicator of room acoustics, however, most studies focus on the mid-high frequency RT, and less on the low-frequency RT. In this paper, a hybrid approach based on geometric and wave methods was proposed to build a more accurate and wide frequency-band room acoustic impulse response. This hybrid method utilized the finite-difference time-domain (FDTD) method modeling at low frequencies and the Odeon simulation at mid-high frequencies, which was investigated in a university classroom. The influence of the low-frequency RT on speech intelligibility was explored. For the low-frequency part, different impedance boundary conditions were employed and the effectiveness of the hybrid method has also been verified. From the results of objective acoustical parameters and subjective listening experiments, the smaller the low-frequency RT was, the higher the Chinese speech intelligibility score was. The syllables, consonants, vowels, and the syllable order also had significant effects on the intelligibility score.
Źródło:
Archives of Acoustics; 2023, 48, 3; 151-157
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelling and analysis of fibre microlenses with ray-tracing and finite-difference methods
Autorzy:
Śliwak, Adam
Jeleń, Mateusz
Patela, Sergiusz
Powiązania:
https://bibliotekanauki.pl/articles/2063899.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Tematy:
Finite-difference time-domain method
knife-edge method
microlens
raytracing
Opis:
Fibre optic microlenses are small optical elements formed on the end-faces of optical fibres. Their dimensions range from a few tens to hundreds of micrometres. In the article, four optical fibre microlenses are modelled and analysed. Microlenses are used for light beam manipulation and quantitative metrics are needed to evaluate the results, for example, the size of focusing spot or intensity distribution. All four lenses tested are made of rods of the same refractive index; they were welded to a single-mode fibre. Two modelling methods were used to analyse the lenses: ray-tracing and finite-difference time-domain. The ray-tracing algorithm moves rays from one plane to another and refracts them on the surfaces. Finite-difference time-domain consists of calculating Maxwell’s equations by replacing spatial and temporal derivatives by quotients of finite differences. In this paper, the results of the microlenses analyses obtained from ray-tracing and finite-difference timedomain methods were compared. Both mets of analysis showed the presence of undesirable side lobes related to lens design, namely rods too long for lens fabrication. The test results were compared with the measurements made with the knife-edge method. The use of a single tool to determine parameters of an optical fibre lens does not allow for precise determination of its properties. It is necessary to use different tools and programs. This allows a complete analysis of the beam parameters, letting us find the causes of technical issues that limit the performance of the lenses.
Źródło:
Opto-Electronics Review; 2022, 30, 1; 1--9
1230-3402
Pojawia się w:
Opto-Electronics Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulations of a simple refractive index sensor based on side-hole optical fibres
Autorzy:
Dudek, Michał
Köllő, Kinga K.
Powiązania:
https://bibliotekanauki.pl/articles/2174855.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Tematy:
fibre optic sensor
finite-difference time-domain
numerical simulations
refractive index
side-hole optical fibre
Opis:
In this work the influence of the cavity parameters on optical losses of a simple intensitybased in-line refractive index sensor utilizing a micromachined side-hole fibre was studied by means of numerical simulations. To perform these simulations, the Authors used the finite-difference time-domain method. The proposed sensor setup consists of light source, micromachined optical fibre as a sensor head, and a detector which makes it low-cost and easy to build. The changes of the external refractive index can be, therefore, recovered by direct measurements of the transmitted intensity from which insertion loss values can be calculated. By changing geometry of the cavity micromachined into the side-hole optical fibre, it was possible to determine its influence on the final sensor sensitivity and measurements range. Based on the provided analysis of simulations results, a simple fibre optic sensor can be fabricated mainly for sensing external liquids refractive index for application in biochemistry or healthcare.
Źródło:
Opto-Electronics Review; 2022, 30, 4; art. no. e143607
1230-3402
Pojawia się w:
Opto-Electronics Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Problem of Aliasing and Folding Effects in Spectrum of Sampled Signals in View of Information Theory
Autorzy:
Borys, Andrzej
Powiązania:
https://bibliotekanauki.pl/articles/2055264.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
signal sampling
modeling of sampled signal in the time domain
signal information content
spectrum aliasing and folding
Banach–Tarski-like paradox in signal sampling
Opis:
In this paper, the problem of aliasing and folding effects in spectrum of sampled signals in view of Information Theory is discussed. To this end, the information content of deterministic continuous time signals, which are continuous functions, is formulated first. Then, this notion is extended to the sampled versions of these signals. In connection with it, new signal objects that are partly functions but partly not are introduced. It is shown that they allow to interpret correctly what the Whittaker–Shannon reconstruction formula in fact does. With help of this tool, the spectrum of the sampled signal is correctly calculated. The result achieved demonstrates that no aliasing and folding effects occur in the latter. Finally, it is shown that a Banach–Tarski-like paradox can be observed on the occasion of signal sampling.
Źródło:
International Journal of Electronics and Telecommunications; 2022, 68, 2; 315--322
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Basic Logic Gates in Two Dimensional Photonic Crystals for All Optical Device Design
Autorzy:
Sonth, Mahesh V
Srikanth, Gimmadi
Agrawal, Pankaj
Premalatha, B.
Powiązania:
https://bibliotekanauki.pl/articles/1844637.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
basic gates
photonic crystals
finite difference time domain
plane wave expansion
photonic band gap
Opis:
The research carried out in the field of optics and photonics with an idea to design and develop the all optical logic devices in the fascinating material known as photonic crystals (PhCs). The structural investigation reveals that the two dimensional (2-D) PhCs is more suitable for fabrication of optoelectronic components. In this article we have designed basic logic gates in 2-D PhCs as they are the building blocks for the construction of optical devices and in these, refractive index is periodically modulated with the wavelength. The understanding of light behaviour in complex PhCs helps in creating photonic band gap (PBG) that can prevent light of certain wavelength propagating in crystal lattice structure. For the selected geometry structure, three PBG bands will exists out of which two of them are transverse electric (TE) and one is transverse magnetic (TM) mode. The PBG bands in the TE mode ranges from 0.31( α λ ) to 0.46( α λ ), 0.61( α λ ) to 0.63( α λ ) and TM mode ranges from 0.86( α λ ) to 0.93( α λ ). The free space wavelength of 1550 nm is set for the finite difference time domain (FDTD) simulation of the structure. The response time and computational overhead required for the proposed OR gate is 0.128ps and 4.4MB is obtained. Also we calculated the extinction ratio for AND gate and NOT gate as 6.19 dB and 10.21 dB respectively.
Źródło:
International Journal of Electronics and Telecommunications; 2021, 67, 2; 247-261
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Time-domain decomposition for optimal control problems governed by semilinear hyperbolic systems with mixed two-point boundary conditions
Autorzy:
Krug, Richard
Leugering, Günter
Martin, Alexander
Schmidt, Martin
Weninger, Dieter
Powiązania:
https://bibliotekanauki.pl/articles/2183473.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
time-domain decomposition
optimal control
semilinear hyperbolic systems
convergence
Opis:
In this article, we study the time-domain decomposition of optimal control problems for systems of semilinear hyperbolic equations and provide an in-depth well-posedness analysis. This is a continuation of our work, Krug et al. (2021) in that we now consider mixed two-point boundary value problems. The more general boundary conditions significantly enlarge the scope of applications, e.g., to hyperbolic problems on metric graphs with cycles. We design an iterative method based on the optimality systems that can be interpreted as a decomposition method for the original optimal control problem into virtual control problems on smaller time domains.
Źródło:
Control and Cybernetics; 2021, 50, 4; 427--455
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A hybrid approach for fault diagnosis of spur gears using Hu invariant moments and artificial neural networks
Autorzy:
Rex, F. Michael Thomas
Andrews, A.
Krishnakumari, A.
Hariharasakthisudhan, P.
Powiązania:
https://bibliotekanauki.pl/articles/220768.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
gear fault
Ahao-Atlas-Marks
time-frequency domain features
Hu invariant moments
ANN
Opis:
Achieving a reliable fault diagnosis for gears under variable operating conditions is a pressing need of industries to ensure productivity by averting unwanted breakdowns. In the present work, a hybrid approach is proposed by integrating Hu invariant moments and an artificial neural network for explicit extraction and classification of gear faults using time-frequency transforms. The Zhao-Atlas-Marks transform is used to convert the raw vibrations signals from the gears into time-frequency distributions. The proposed method is applied to a single-stage spur gearbox with faults created using electric discharge machining in laboratory conditions. The results show the effectiveness of the proposed methodology in classifying the faults in gears with high accuracy.
Źródło:
Metrology and Measurement Systems; 2020, 27, 3; 451-464
0860-8229
Pojawia się w:
Metrology and Measurement Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Extrapolation of Electromagnetic Response from Linear Antennas in Time Domain without Late-Time Instabilities in Numerical Solution of EFI Equation
Autorzy:
Witenberg, Anna
Powiązania:
https://bibliotekanauki.pl/articles/308882.pdf
Data publikacji:
2020
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
electric field integral equation (EFIE)
linear antenna
solution of time domain EFIE
late time instabilities
Opis:
The paper presents a new hybrid method relied upon to solve integral equations of the electric field in time domain and to model linear antennas with pulse excitation. The method consists in a mixed, numerical-analytical description of the process that helps maintain the stability of calculations during the late time phase. As described in the analytical part, the modified spherical Bessel function of the first kind allows for extrapolation with a high degree of accuracy and loworder expressions. The modified spherical Bessel functions of the first kind are of the oscillating character, and their combination with the exponential factor makes them convenient for extrapolation of the answer of the antenna with pulse excitation. New functions are introduced to computational practice.
Źródło:
Journal of Telecommunications and Information Technology; 2020, 2; 45-50
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Non-linear modelling of elastic hysteretic damping in the time domain
Autorzy:
Spitas, C.
Dwaikat, M. M. S.
Spitas, V.
Powiązania:
https://bibliotekanauki.pl/articles/38606055.pdf
Data publikacji:
2020
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
hysteresis
damping
modified viscous model
dynamics time-domain
mechanical vibration
frequency
non-linear modeling
Opis:
Elastic hysteretic damping is defined as the dissipation of energy at a rate that is weakly dependent on frequency of vibration. In this article, we propose that the elastic hysteretic damping can be achieved by a simple modification to the viscous damping model. The proposed modification is based on computing an instantaneous correction factor that recursively depends on the state variables of the system. This correction factor is related to the rate by which the velocity changes with respect to the displacement. The new model compares quite favourably with the other existing solutions in the time-domain and differences between the solutions become evident for higher damping ratios. It is found that the new model predicts consistently the weak variation in the loss factor as a function of frequency. In addition to its simple mathematical formulation, the proposed model is superior to the existing solutions in that it does not require knowledge of the past history of motion neither the knowledge of the excitation frequency and is extensible to any type of loading. Various aspects pertaining to the linearity of the proposed approach are finally discussed.
Źródło:
Archives of Mechanics; 2020, 72, 4; 323-353
0373-2029
Pojawia się w:
Archives of Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł

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