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Wyszukujesz frazę "Ahmed, S." wg kryterium: Autor


Wyświetlanie 1-5 z 5
Tytuł:
Investigations of Couette flow unsteady radiative convective heat transfer in a vertical channel using the generalized method of lines (MOL)
Autorzy:
Sowayan, Ahmed S.
Powiązania:
https://bibliotekanauki.pl/articles/2174210.pdf
Data publikacji:
2022
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
promieniowanie
konwekcja naturalna
metoda Runge-Kutty
vertical channel
radiation
natural convection
method of lines (MOL)
Runge-Kutta method
Opis:
This study describes a very efficient and fast numerical solution method for the non-steady free convection flow with radiation of a viscous fluid between two infinite vertical parallel walls. The method of lines (MOL) is used together with the Runge-Kutta ODE Matlab solver to investigate this problem numerically. The presence of radiation adds more stiffness and numerical complexity to the problem. A complete derivation in dimensionless form of the governing equations for momentum and energy is also included. A constant heat flux condition is applied at the left wall and a transient numerical solution is obtained for different values of the radiation parameter (R). The results are presented for dimensionless velocity, dimensionless temperature and Nusselt number for different values of the Prandtl number (Pr), Grashof number (Gr), and the radiation parameter (R). As expected, the results show that the convection heat transfer is high when the Nusselt number is high and the radiation parameter is low. It is also shown that the solution method used is simple and efficient and could be easily adopted to solve more complex problems.
Źródło:
International Journal of Applied Mechanics and Engineering; 2022, 27, 3; 199--211
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A conservative scheme with optimal error estimates for a multidimensional space-fractional Gross–Pitaevskii equation
Autorzy:
Hendy, Ahmed S.
Macías-Díaz, Jorge E.
Powiązania:
https://bibliotekanauki.pl/articles/330834.pdf
Data publikacji:
2019
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
generalized Gross–Pitaevskii system
Riesz fractional diffusion
Sobolev inequality
conservative method
optimal error bounds
równanie Grossa-Pitaevskiego
nierówność Sobolewa
metoda konserwatywna
optymalna granica błędu
Opis:
The present work departs from an extended form of the classical multi-dimensional Gross–Pitaevskii equation, which considers fractional derivatives of the Riesz type in space, a generalized potential function and angular momentum rotation. It is well known that the classical system possesses functionals which are preserved throughout time. It is easy to check that the generalized fractional model considered in this work also possesses conserved quantities, whence the development of conservative and efficient numerical schemes is pragmatically justified. Motivated by these facts, we propose a finite-difference method based on weighted-shifted Grünwald differences to approximate the solutions of the generalized Gross–Pitaevskii system. We provide here a discrete extension of the uniform Sobolev inequality to multiple dimensions, and show that the proposed method is capable of preserving discrete forms of the mass and the energy of the model. Moreover, we establish thoroughly the stability and the convergence of the technique, and provide some illustrative simulations to show that the method is capable of preserving the total mass and the total energy of the generalized system.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2019, 29, 4; 713-723
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase velocity and attenuation of longitudinal shear vibrations of hollow poroelastic cylinders
Autorzy:
Ahmed Shah, S.
Javvad Hussaini, S.
Powiązania:
https://bibliotekanauki.pl/articles/955126.pdf
Data publikacji:
2014
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
prędkość fazowa
tłumienie drgań podłużnych
teoria Biota
Biot's theory
hollow cylinder
shear waves
frequency equation
phase velocity
attenuation
wavenumber
dissipation
Opis:
The present paper is devoted to the study of phase velocity and attenuation of longitudinal shear vibrations of hollow poroelastic circular cylinders in the presence of dissipation. The explicit expressions for phase velocity and attenuation of longitudinal shear vibrations are derived. The frequency equation of longitudinal shear vibrations and modes obtained in a previous paper are used to compute the phase velocity and attenuation for different dissipations for thin and thick poroelastic cylindrical shells and poroelastic solid cylinder. The physical parameters of sandstone saturated with kerosene and sandstone saturated with water are used for the purpose of computation. It is found that the phase velocity is linear beyond certain frequency. Phase velocity is smaller for a typical anti-symmetric mode compared to the flexural mode. It is greater for the second mode than that of the first mode. Also the phase velocity is larger for a thin poroelastic cylindrical shell than that of a thick poroelastic cylindrical shell. The same is true for attenuation also. Attenuation is very high for the considered dissipations and it increases with the increase in dissipation.
Źródło:
International Journal of Applied Mechanics and Engineering; 2014, 19, 2; 337-346
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Response of non-linear shock absorbers-boundary value problem analysis
Autorzy:
Rahman, M. A.
Ahmed, U.
Uddin, M. S.
Powiązania:
https://bibliotekanauki.pl/articles/265424.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
amortyzator
tłumik drgań
stabilność
wartość graniczna
shock absorber
untuned vibration damper
frequency ratios
non-linear springs
non-linear dampers
stability
boundary value problem
multisegment method of integration
Opis:
A nonlinear boundary value problem of two degrees-of-freedom (DOF) untuned vibration damper systems using nonlinear springs and dampers has been numerically studied. As far as untuned damper is concerned, sixteen different combinations of linear and nonlinear springs and dampers have been comprehensively analyzed taking into account transient terms. For different cases, a comparative study is made for response versus time for different spring and damper types at three important frequency ratios: one at r = 1, one at r > 1 and one at r <1. The response of the system is changed because of the spring and damper nonlinearities; the change is different for different cases. Accordingly, an initially stable absorber may become unstable with time and vice versa. The analysis also shows that higher nonlinearity terms make the system more unstable. Numerical simulation includes transient vibrations. Although problems are much more complicated compared to those for a tuned absorber, a comparison of the results generated by the present numerical scheme with the exact one shows quite a reasonable agreement.
Źródło:
International Journal of Applied Mechanics and Engineering; 2013, 18, 3; 793-814
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hybrid cryptography with a one-time stamp to secure contact tracing for COVID-19 infection
Autorzy:
El-Douh, Ahmed Abdel-Rahim
Lu, Song Feng
Elkouny, Abdelatif A.
Amein, A.S.
Powiązania:
https://bibliotekanauki.pl/articles/2055157.pdf
Data publikacji:
2022
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
hybrid cryptography
digital signature
RSA
AES
asymmetric cryptography
symmetric cryptography
cybersecurity
COVID-19
kryptografia hybrydowa
podpis elektroniczny
kryptografia asymetryczna
kryptografia symetryczna
cyberbezpieczeństwo
Opis:
The COVID-19 pandemic changed the lives of millions of citizens worldwide in the manner they live and work to the so-called new norm in social standards. In addition to the extraordinary effects on society, the pandemic created a range of unique circumstances associated with cybercrime that also affected society and business. The anxiety due to the pandemic increased the probability of successful cyberattacks and as well as number and range. For public health officials and communities, location tracking is an essential component in the their efforts to combat the disease. The governments provide a lot of mobile apps to help health officials to trace the infected persons and contact them to aid and follow up on the health status, which requires an exchange of data in different forms. This paper presents the one-time stamp model as a new cryptography technique to secure different contact forms and protect the privacy of the infected person. The one-time stamp hybrid model consists of a combination of symmetric, asymmetric, and hashing cryptography in an entirely new way that is different from conventional and similar existing algorithms. Several experiments have been carried out to analyze and examine the proposed technique. Also, a comparison study has been made between our proposed technique and other state-of-the-art alternatives. Results show that the proposed one-time stamp model provides a high level of security for the encryption of sensitive data relative to other similar techniques with no extra computational cost besides faster processing time.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2022, 32, 1; 139--146
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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