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1
Determination of transfer function through solution in time domain
100%
Wielądek R. , Nowożyński K.
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2001
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tom Vol. 49, nr 1
131-142
EN
A new method of transfer function determination through solution in time domain is presented. As compared to the linear problem the proposed new formulation of the problem employs five instead of three sequences of unknowns. This makes it possible to bring the errors of adjusted observations closer to white noise and to improve the accuracy of transfer function approximation. In this formulation, however, the problem looses its linearity and one must use a nonlinear instead of linear method of least-squares. The authors propose an economical algorithm of the method of successive approximations. For finding the initial approximation, the use is made of the linear problem solution.
2
Content available remote Nonlinear time domain analysis of vertical ship motions
70%
Bruzzone D. , Grasso A.
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2007
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tom Vol. 7, no 4
27-37
EN
A nonlinear time domain seakeeping analysis has been performed for ships advancing in head seas with regular waves. A hybrid approach has been employed, solving the unsteady hydrodynamic problem in the frequency domain and the equations of motion in the time domain. This procedure transfers radiation and diffraction forces, supposed linear, from frequency to time domain, where nonlinear FroudeKrylov and hydrostatic forces are computed considering the actual hull wetted surface at each time step. In a first test case, a monohull, both a strip theory and a three-dimensional Rankine panel method have been used for the frequency domain analysis, while for another test case, a trimaran, only the three-dimensional methodology has been applied. A comparison of the results shows a good agreement with experimental data and the hybrid approach appears to be actually independent of the technique used in the frequency domain, even if the reliability of the results is strongly related with the accuracy of the evaluation of the hydrodynamic terms.
PL
Przedstawiona została nieliniowa analiza właściwości morskich statku w dziedzinie czasu dla statków poruszających się przy regularnej fali przeciwnej. Zastosowana została metoda hybrydowa polegająca na rozwiązywaniu nieustalonego zagadnienia hydrodynamicznego w dziedzinie częstotliwości i równań ruchu w dziedzinie czasu. Siły radiacyjne i dyfrakcyjne, z założenia liniowe, są przekazywane z dziedziny częstotliwości do dziedziny czasu, gdzie w każdym kroku czasowym obliczane są nieliniowe siły Froude'a-Kryłowa i siły hydrostatyczne z uwzględnieniem rzeczywistej powierzchni zwilżonej kadłuba. W pierwszym prezentowanym przypadku - statku jednokadłubowego, do analizy w dziedzinie częstotliwości została zastosowana zarówno metoda paskowa (strip theory), jak i trójwymiarowa metoda panelowa Rankine'a, natomiast w drugim przypadku - trimarana, zastosowano tylko metodę trójwymiarową. Porównanie wyników pokazuje dobrą zgodność z danymi doświadczalnymi. Metoda hybrydowa okazała się rzeczywiście niezależna od metody zastosowanej w dziedzinie częstotliwości nawet, jeżeli wiarygodność wyników jest silnie zależna od dokładności wyznaczania członów hydrodynamicznych.
3
Content available remote Foreign direct investment and growth causal-nexus in economic community of West African States: Evidence from spectral causality
70%
Adam A. M.
Business and Economic Horizons
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2018
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tom Volume 14
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nr Issue 1
17-28
EN
The paper examines the causal relationship between FDI and economic growth (GDP) in thirteen ECOWAS countries using both time domain and frequency domain testing procedures using annual data from 1970 to 2015. The results showed that time domain is not adequate in detecting causality. The time domain detected causality in only four out of thirteen countries whilst the frequency domain detected causality at different frequencies and cycles in nine out of thirteen countries. The findings of this study indicate the importance of frequency domain causality, that it decomposes causality at different frequencies and subsequently detects causality at certain cycles lengths. The general observation that economic growth leads FDI calls for ECOWAS leaders to rethink about painful sacrifices they make to attract FDI into the region.
4
Content available An introduction to envelope constrained filter design
60%
Cantoni A. , Vo B. N. , Teo K. L.
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2001
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tom nr 3
3-14
EN
Envelope constrained filter design is concerned with the time domain synthesis of a filter whose response to a specified input signal stays within prescribed upper and lowe bounds and in addition has minimal noise enhancement. In many practical applications, a "soft" approach, such as least mean square, is not the most suitable and it becomes necessary to use "hard" constraints such as the ones considered in the paper. We present an overview of key ideas related to robust continuous time envelope constrained filter design.
5
Content available The wave transformer – analysis and application of time digital filters and the integral-derivative operators of ½ order
60%
Siwczyński M. , Drwal A. , Żaba S.
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6
Content available remote Rozkłady: prąd aktywny, prąd rozrzutu, prąd bierny w dziedzinie czasu - podstawy matematyczne, metoda operatorowa
60%
Siwczyński M.
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2011
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tom R. 87, nr 4
134-141
PL
W artykule podano podstawy matematyczne rachunku operatorowego L-impulsów i sygnałów okresowych. Takie podejście umożliwia identyfikację zjawisk energetycznych w obwodach elektrycznych bezpośrednio w dziedzinie czasu. W szczególności dotyczy to kwestii rozkładu prądu odbiornika na składowe fizyczne.
EN
In the article the mathematical theory of the operational calculus of the L- impulses and periodical signals are presented. Was shown that this approach makes identification of power phenomena in electrical circuit in the time domain: the distribution of current to physical components in special case.
7
Content available remote GMAW process stability evaluation through acoustic emission by time and frequency domain analysis
51%
Huanca Cayo E. , Absi Alfaro S. C.
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2009
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tom Vol. 34, nr 2
157-164
EN
Purpose: In the present work was made the comparative analysis in time domain and frequency domain to the acoustical pressure generate by the electric arc to determinate which of the two analysis methods is better to evaluates the stability in GMAW process. Design/methodology/approach: Welds had been made with the parameters adjusted to get the highest stability. In these conditions, were simulated instabilities that had been generated by the grease presence in the weld trajectory. In both experimental groups was acquired the acoustical pressure signal produced by electric arc to made analysis based in time domain and frequency domain. Findings: After this comparative study we conclude that the acoustical evaluation of the stability on the GMAW process presents more clarity for the analysis based in the time domain that the frequency domain. Research limitations/implications: In the gotten results, the time domain analysis method could represent adequately the stability and the instability of the process. The stability characterizes for the continuity and minim variation of the statistical parameters, but in the presence of instabilities, these parameters present chaotic changes. In the frequency domain method the variations are imperceptible for steady and unstable regions, but it presents little definite variations in the amplitude of determined bands of frequencies. Originality/value: The stability evaluation in welding is crucial because it is responsible in the weld quality. The non contact methods as the acoustical method have a potentiality extraordinary to monitoring and detect instabilities in welding. The acoustical sensing has the capacity to make an on-line monitoring of the weld process.
8
Transmission of stress induced electric signals in dielectric media. Part III
51%
Varotsos P. , Sarlis N. , Skodras E.
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2000
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tom Vol. 48, nr 3
263-297
EN
The frequency dependence of the electric field produced by an electric current dipole lying inside or very close to a highly conductive cylinder (s), of infinite length and radius R, embedded in a significantly less conductive medium (s') is investigated. The study is extended to the case when the dipole is located inside or very close to a highly conductive layer (s), of infinite extent and width w, embedded in a significantly less conductive medium (s'). At large distances d from the source and for appreciably low frequencies, i.e., f<fc or f >f0, the electric field is attenuated with a skin depth significantly smaller than deltaout having as a lower limit the skin depth deltain for a full volume of conductivity s. The properties of the recordings, at remote distances, from a current dipole source emitting an exponentially decaying signal of unit initial amplitude and a relaxation time constant t is also studied. The source is located either inside a full volume of conductivity s' or inside a conductive half-space at a depth h (<< d). In the case of homogeneous medium s', a certain relaxation time t0 = žs'd(2)/4 exists due to the diffusion dynamics, leading to the following conclusions. If t << t0 the recordings have an enlarged duration of around t0 and an amplitude orders of magnitude smaller than that corresponding to the static case. If t > t0 the recordings have a duration almost equal to that of the emitted signal, and arrive after a time of around t0, and their amplitude approaches that of the static case. In the case of the current source located within a conductive half-space, the signal recorded at remote observation sites on the interface, arrives in two parts. The first part (which "diffuses" from the source to the interface and then propagates as a surface wave) has a duration significantly smaller than the second part ("solely diffusing" through the conductive medium). The study is extended to the case of a series of signals emitted at equal time-intervals. The application of the above to the earth explain the absence of co-fracture signals but do indicate, that the precursory Seismic Electric Signals reach detectable values at certain sites on the earth's surface.
9
Content available remote Methods for vehicle vibration analysis in time domain
41%
Gerlici J. , Lack T.
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2007
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tom z. 63
71-81
EN
Simulation computations, mainly supported by computational technique, are used for the vehicle vibration analysis. The procedures and methods are used for the forced oscillation of a mechanical system solution. The vehicle model has been created for this purpose. A kinematical excitation and accelerations act on the model. We can search a response from a harmonic excitation via the solution in a complex, or a real form, or we can analyse the vehicle vibration in the time domain. It is useful to use the HHT method [3] as a special variant of the Newmark method. The procedures may be performed with the DELTA programme [2].
PL
Obliczenia symulacyjne, wspomagane głownie przez technikę obliczeniową, wykorzystano do analizy drgań pojazdu. Procedury i metody wykorzystuje się do rozwiązania drgań wymuszonych układu mechanicznego. W tym celu zbudowano model pojazdu. Na model oddziaływują wymuszenia kinematyczne i przyspieszenia. Odpowiedzi na wymuszenia harmoniczne można poszukać poprzez rozwiązania w postaci zespolonej lub rzeczywistej lub można analizować drgania pojazdu w dziedzinie czasu. Użyteczne jest wykorzystanie metody HHT [3] jako szczególnej odmiany metody Newmarka. Procedury można poprowadzić wykorzystując program DELTA [2].
10
Content available remote Rozkłady: prąd aktywny, prąd rozrzutu, prąd bierny, prąd niesymetrii w dziedzinie czasu - obwody trójfazowe
41%
Siwczyński M.
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2010
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tom R. 86, nr 8
210-213
PL
W artykule pokazano, że dziedzina czasu ujawnia wszystkie zjawiska energetyczne także w obwodach trójfazowych, tj. rozkład prądu odbiornika na prąd aktywny, prąd bierny i prąd rozrzutu i prąd niesymetrii.
EN
In the article was shown that the time domain approach makes identification of power phenomena in three phase electrical circuits: the current distribution to physical components: active current, reactive current, scattered current and asymmetrical current.
11
Content available remote Rozkłady: prąd aktywny, prąd rozrzutu, prąd bierny w dziedzinie czasu – obwody jednofazowe
41%
Siwczyński M.
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2010
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tom R. 86, nr 6
196-201
PL
W artykule tym pokazano, że zarówno dziedzina częstotliwościowa jak i czasowa ujawnia wszystkie zjawiska energetyczne w obwodach elektrycznych, tj. rozkład prądu obwodu na prąd aktywny, prąd bierny i prąd rozrzutu.
EN
In the article was shown that the frequency domain and the time domain approach too makes identification of power phenomena in electrical circuit: the current distribution to physical components: active current, reactive current, scattered current.
12
Rozkład admitancji odbiornika na składową czynną i bierną w dziedzinie czasu
41%
Siwczyński M. , Drwala A. , Żaba S.
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2011
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tom R. 79, nr 10
36-39
PL
Przedstawiono nowy sposób rozkładu admitancji odbiornika na składową czynną i bierną w dziedzinie czasu. Opisany rozkład z dziedziny czasu można uzyskać dla transmisji z biegunami rzeczywistymi, zespolonymi i urojonymi. Rozkład admitancji indukuje rozkład prądu na składową czynną i bierną w dziedzinie czasu przy użyciu splotów cyklicznych.
EN
The paper presents a new method of decomposition of load admittance into active and reactive components in the time domain. Described decomposition in the time domain may be obtained for transmission with real, complex and imaginary poles. Decomposition of admittance implies decomposition of current into real and reactive components in time domain using cyclic convolutions.
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