PL
 |
EN
Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 19

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  Laplace transforms
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
1
Content available Natural frequency and critical velocities of heated inclined pinned PP-R pipe conveying fluid
Mohmmed J. H., Tawfik M. A., Atiyah Q. A.
Journal of Achievements in Materials and Manufacturing Engineering
|
2021
|
Vol. 107, nr 1
15--27
EN
Purpose: The flow velocity and pressure of fluid flowing through a pipeline can cause the vibration of pipes, and consequently result in the modification in natural frequency via fluid-structure interaction. The value of the natural frequency of a component when approaches the excitation force to a certain degree, a severe resonance failure may occur. Hence, avoiding the resonance failure of a pipe subjected to complex conditions is an essential issue that requires to be solved urgently in the engineering field. This work treats the transverse vibration for flexible inclined heated pipe, made of polypropylene randomcopolymer (PP-R), conveying fluid assuming pinned connections at the ends. The pipe was placed at different support angles and subjected to variant temperatures. Design/methodology/approach: The inclined pipe is modelled as Euler-Bernoulli beam taking into account its self-weight, temperature variation, inclination angle, aspect ratio, and internal fluid velocity. The integral transforms method, which includes the finite Fourier sine and the Laplace transforms, was used to develop an analytic solution to the modified equation of motion and the analytical expressions for dual natural frequencies of the pipefluid interaction system were computed. Findings: The proposed solution technique via finite Fourier sine and Laplace transforms offers a more convenient alternative to calculate the dynamic characteristic of pipes conveying fluid. The obtained results showed that the dynamical behaviour of pipe–fluid system is strongly affected by fluid flow velocity, degree of inclination, temperature variation, and aspect ratio of the pipe in transverse modes. Research limitations/implications: This work focuses on fundamental (first) mode in the most discussions. Practical implications: It was revealed that the thermal effects in the pipe are a very important factor and more significant in comparison with the internal fluid velocity and the inclination angle has a larger impact on vibration characteristics at a higher aspect ratio. The findings can be useful for the design of engineering components. Originality/value: Determining the combining effect of inclination angle, aspect ratio, and thermal loading on vibration characteristic of the pipes conveying fluid by using an improved analytic solution to the modified equation of motion via mixed of finite Fourier sine and Laplace transforms.
2
Content available remote Unified fractional derivative models of magneto-thermo-viscoelasticity theory
Ezzat M. A., El-Bary A. A.
Archives of Mechanics
|
2016
|
Vol. 68, nr 4
285--308
EN
A unified mathematical model of fractional magneto-thermo-viscoelasticty for isotropic perfectly conducting media involving fractional relaxation operator is given. Some essential theorems on the linear coupled and generalized theories of thermoviscoelasticity can be easily obtained. The new fractional model is applied to a halfspace subjected to two different forms of time-dependent thermal shock in, the presence of a transverse magnetic field. The Laplace transform techniques are used. Numerical computation is performed by using a numerical inversion technique and the resulting quantities are shown graphically. The effects of the fractional orders on viscoelastic material are discussed.
3
Content available Response due to mechanical source in second axisymmetric problem of micropolar elastic medium
Singh R.
International Journal of Applied Mechanics and Engineering
|
2013
|
Vol. 18, no. 4
1249--1261
EN
The second axisymmetric problem in a micropolar elastic medium has been investigated by employing an eigen value approach after applying the Laplace and the Hankel transforms. An example of infinite space with concentrated force at the origin has been presented to illustrate the application of the approach. The integral transforms have been inversed by using a numerical technique to obtain the components of microrotation, displacement, force stress and couple stress in the physical domain. The results for these quantities are given and illustratred graphically.
4
Content available Some practical applications of generating functions and LSTS
Ziółkowski M.
Scientific Issues of Jan Długosz University in Częstochowa. Mathematics
|
2012
|
Vol. 17
97–110
EN
In many various practical problems we often deal with computing distribution functions of sums of independent non-negative random variables. In applied mathematics (ex. queueing theory) we can find many formulas with Stieltjes convolutions of distribution functions of random variables of the same type. Finding convolutions on the base of definition is not easy and convenient, because there are some technical problems connected with computations. There are some interesting ways to obtain such distribution functions applying other methods. In this paper we present methods connected with applications of generating functions and Laplace-Stieltjes transforms.
5
Content available remote Method of finding incomes in HM-Networks with time-dependent intensity of requests service
Matalytski M., Kiturko O., Czhornaja N.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
|
2011
|
Vol. 10, nr 2
169-178
EN
The article deals with an HM-network with time-dependent service rates of applications in the systems. The presented methods for finding the expected income systems: the direct method, Laplace transforms, the method of difference scheme, are implemented using the software package Mathematica. Expected earnings are important for solving problems of optimization and control of HM-networks, which are used in practice as stochastic models of various objects in computer technology, insurance, logistics, and medicine.
6
Content available remote Bivariate natural exponential families with linear diagonal variance functions
Chachulska J.
Probability and Mathematical Statistics
|
2010
|
Vol. 30, Fasc. 1
121--139
EN
It is well known that natural exponential families (NEFs) are uniquely determined by their variance functions (VFs). However, there exist examples showing that even an incomplete knowledge of a matrix VF can be sufficient to determine a multivariate NEF. Following such an idea, in this paper a complete description of bivariate NEFs with linear diagonal of the matrix VF is given. As a result we obtain the families of distributions with marginals that are some combinations of Poisson and normal distributions. Furthermore, the characterization extends (in two-dimensional case) the classification of NEFs with linear matrix VF obtained by Letac [11]. The main result is formulated in terms of regression properties.
7
Content available remote The Sequence Project of the Control Plan of Reliability of the Weibull Model Distribution
Grubicka J.
Computational Methods in Science and Technology
|
2010
|
Vol. 16, No. 2
135-139
EN
It is no exaggeration to say that the PN-IEC 61124 standard is inapplicable in many branches e.g. electronic industry. It is because PN-IEC 61124 assumes failure rate to be constant in time. This paper rejects this assumption and presents mathematical foundation of an alternative of PN-IEC 61124 applicable in electronic industry.
8
Content available Analysis of fundamental solutions to fractional diffusion-wave equation in polar coordinates
Povstenko Y.
Scientific Issues of Jan Długosz University in Częstochowa. Mathematics
|
2009
|
Vol. 14
97-104
EN
The diffusion-wave equation is a mathematical model of a wide range of important physical phenomena. The first and second Cauchy problems and the source problem for the diffusion-wave equation are considered in cylindrical coordinates. The Caputo fractional derivative is used. The Laplace and Hankel transforms are employed. The results are illustrated graphically.
9
Content available remote Inverse Laplace transforms using convolution integral
Jha B. K., Ajibade A. O.
International Journal of Applied Mechanics and Engineering
|
2008
|
Vol. 13, no 4
1119-1123
EN
In the present article, the convolution theorem is used to obtain the inverse Laplace-transforms of some Laplace-transforms functions. Although the inverse Laplace-transforms of these functions are available in the works of Abramowitz and Stegun (1965), Carlslaw and Jaeger (1952), Churchill (1972), Miles (1971) and Özisik (1980), they require integration of complementary-error-function for computational purposes. The results presented in this article are directly applicable in many branches of science where time-dependent initial and boundary conditions are frequently occurring.
10
Content available remote Modified technique of FFT-based numerical inversion of Laplace transforms with applications
Brancik L.
Przegląd Elektrotechniczny
|
2007
|
R. 83, nr 11
53-56
EN
The paper presents a modified technique of numerical inversion of Laplace transforms based on FFT and quotient-difference algorithms and its Matlab implementation. The method enables to process general transforms of more complex variables and can therefore serve as a basis for inversion of multidimensional Laplace transforms. An application of the method is illustrated by getting matrix exponential function derivative needed at sensitivity calculation in multiconductor-transmission-line systems.
PL
W artykule przedstawiono zmodyfikowaną metodę numerycznego obliczania transformaty odwrotnej Laplace'a, opartą o FFT i algorytmy ilorazowo-różniczkowe wraz z ich implementacją w Matlabie. Metoda ta umożliwia przetwarzanie transformat wielu zmiennych zespolonych, a więc może służyć jako podstawa do odwracania wielowymiarowych transformat Laplace'a. Zastosowanie algorytmu zostało zilustrowane przykładem wyznaczenia macierzy pochodnych funkcji eksponencjalnych, wykorzystywanej przy obliczeniach wieloprzewodowych linii transmisyjnych.
11
Content available remote Numerical Solution of Electro-magneto-thermo-mechanical Shock Problem
El-Bary A.
Computational Methods in Science and Technology
|
2006
|
Vol. 12, nr 2
101-108
EN
A conducting half-space, permeated by an initial magnetic field governed by the generalized equations of thermoelasticity is considered. The bounding plane is acted upon by a combination of thermal and mechanical shock. The formulation is applied to both generalizations, Lord-Shulman theory and the Green-Lindsay theory, as well as to the coupled theory. Laplace transform techniques together with the method of potentials are used. The inversion of the Laplace is carried out using a numerical approach. Numerical results for the temperature, the stress and the induced magnetic and electric field distributions are obtained and illustrated graphically for a particular case. Comparisons are made with the results obtained in the case of the absence of the magnetic field.
12
Content available remote Laplace transforms for MIMO SD systems with delay
Lampe B. P., Rosenwasser E. N.
Archives of Control Sciences
|
2006
|
Vol. 16, no. 4
363-381
EN
The paper constructs the Laplace transform of the solution with zero initial energy for a MIMO sampled-data system containing pure time-delays in its stationary elements. The properties of the Laplace transform as a function of the complex variable are studied.
13
Content available remote Wave Approach to the Transient Processes in Pantograph – Catenary System
Kumaniecka A., Snamina J.
Vibrations in Physical Systems
|
2004
|
Vol. 21
239--242
14
Content available Are infinite dimensional models applicable in modelling and analysis of cancer chemotherapy?
Świerniak A., Kimmel M., Śmieja J., Rzeszowska-Wolny J.
Journal of Medical Informatics & Technologies
|
2004
|
Vol. 8
MM3--10
EN
Drug resistance and phase dependence have been regarded by many authors as the main obstacles against successful cancer chemotherapy. We propose a model which takes into account both these phenomena and give a tool to use phase specificity as an advantage rather than a fault and make it resistant of drug resistance. It combines models that so far have been studied separately, taking into account both the phenomenon of gene amplification and drug specificity in chemotherapy, in their different aspects. The mathematical description is given by an infinite dimensional state equation with a system matrix, the form of which enables decomposition of the model into two interacting subsystems. While the first one, of finite dimension, can have any form, the second one is infinite dimensional and tridiagonal.
15
Content available remote H2-norm computation for stable linear continuous-time periodic systems
Lampe B. P., Obraszo M., Rosenwasser E. N.
Archives of Control Sciences
|
2004
|
Vol. 14, no. 2
147-160
EN
The paper deals with the H2-norm of finite dimensional linear continuous-time periodic (FDLCP) systems, represented in state space. on basis of general formulae for the H2-norm significantly simpler formulae are derived under the assumption of stability of the system. the proposed method needs to compute the transition matrix on the interval (...) An example is given, where the H2-norm is determined exactly, and the proposed method turns out to be superior to other known methods.
16
A control design for linear time-delay systems
Tingey D., Busawon K., Danaher S., Waterworth G.
Systems Science
|
2003
|
Vol. 29, nr 4
5-17
EN
In this paper, we propose a control design for single-input linear systems with a known delay in the state. A systematic construction of the controller gain is given such that the system is asymptotically stable in the sense of Krasovskii. An academic example is used to show the performance of the controller via simulation.
17
An M/G/1 queue with second optional service and Bernoulli schedule server vacations
Madan K.C., Abu-Dayyeh W., Saleh M.F.
Systems Science
|
2002
|
Vol. 28, nr 3
51-62
EN
We study an M/G/1 queue with second optional service and Bernoulli schedule server vacations. Poisson arrivals with mean arrival rate lambda ([right angle bracket] 0), all demand the first 'essential' service, whereas only some of them demand the second 'optional' service. The service times of the first essential service are assumed to follow a general (arbitrary) distribution with distribution function B( nu ) and that of the second optional service are exponential with mean service time 1/ mu /sub 2/ ( mu /sub 2/ [right angle bracket] 0). We have assumed that after completion of a service, the server takes Bernoulli schedule server vacations. The time-dependent probability generating functions have been obtained in terms of their Laplace transforms and the corresponding steady state results have been derived explicitly in closed form. Some known results have been derived as particular cases.
18
Content available remote Influence and Green's functions for orthotropic micropolar continua
Kumar R., Choudhary S.
Archives of Mechanics
|
2002
|
Vol. 54, nr 3
185-198
EN
The article reports on a methodology to synthesize the response of orthotropic micropolar half-space subjected to concentrated and distributed loads. The disturbance due to normal and tangential loads are investigated by employing the eigenvalue approach. The integral transforms have been inverted by using a numerical technique to obtain the normal displacement, normal force stress and tangential couple stress in the physical domain. The results concerning these quantities are given and illustrated graphically.
19
Modelling of cell aging - system theoretic approach
Świerniak A., Kimmel M., Śmieja J., Rzeszowska-Wolny J.
Journal of Medical Informatics & Technologies
|
2001
|
Vol. 2, Part. 1
MI3--MI8
EN
We characterize the asymptotic behavior of telomeres shortening of which is supposed to be the mechanism of aging and death. The problem is described by models in the form of infinitely many differential linear first order equations, resulting from branching random walk processes used to represent the evolution of particles in this problem, under different assumptions dealing with stochastic characterization of the process. We use control theoretical machinery based on Laplace transforms, Tauberian theorems and transfer loop reduction.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.