DSpace Komunita:http://hdl.handle.net/11025/106712020-02-18T21:09:45Z2020-02-18T21:09:45ZEstimation of the nuclear fuel assembly eigenfrequencies in the probability senseZeman, VladimírHlaváč, Zdeněkhttp://hdl.handle.net/11025/119602019-10-02T10:53:08Z2014-01-01T00:00:00ZNázev: Estimation of the nuclear fuel assembly eigenfrequencies in the probability sense
Autoři: Zeman, Vladimír; Hlaváč, Zdeněk
Abstrakt: The paper deals with upper and lower limits estimation of the nuclear fuel assembly eigenfrequencies, whose
design and operation parameters are random variables. Each parameter is defined by its mean value and standard
deviation or by a range of values. The gradient and three sigma criterion approach is applied to the calculation
of the upper and lower limits of fuel assembly eigenfrequencies in the probability sense. Presented analytical
approach used for the calculation of eigenfrequencies sensitivity is based on the modal synthesis method and the
fuel assembly decomposition into six identical revolved fuel rod segments, centre tube and load-bearing skeleton
linked by spacer grids. The method is applied for the Russian TVSA-T fuel assembly in the WWER1000/320 type
reactor core in the Czech nuclear power plant Temelín.2014-01-01T00:00:00ZZeman, VladimírHlaváč, ZdeněkAnalytic solution of simplified Cardan’s shaft modelZajíček, MartinDupal, Janhttp://hdl.handle.net/11025/119592019-10-02T10:53:07Z2014-01-01T00:00:00ZNázev: Analytic solution of simplified Cardan’s shaft model
Autoři: Zajíček, Martin; Dupal, Jan
Abstrakt: Torsional oscillations and stability assessment of the homokinetic Cardan shaft with a small misalignment angle
is described in this paper. The simplified mathematical model of this system leads to the linearized equation of
the Mathieu’s type. This equation with and without a stationary damping parameter is considered. The solution of
the original differential equation is identical with those one of the Fredholm’s integral equation with degenerated
kernel assembled by means of a periodic Green’s function. The conditions of solvability of such problem enable
the identification of the borders between stability and instability regions. These results are presented in the form of
stability charts and they are verified using the Floquet theory. The correctness of oscillation results for the system
with periodic stiffness is then validated by means of the Runge-Kutta integration method.2014-01-01T00:00:00ZZajíček, MartinDupal, JanThree-scale model of single bone osteon modelled as double-porous fluid saturated body: Study of influence of micro/meso-structureTurjanicová, JanaRohan, EduardNaili, Salahhttp://hdl.handle.net/11025/119582019-10-02T10:53:06Z2014-01-01T00:00:00ZNázev: Three-scale model of single bone osteon modelled as double-porous fluid saturated body: Study of influence of micro/meso-structure
Autoři: Turjanicová, Jana; Rohan, Eduard; Naili, Salah
Abstrakt: This paper deals with the multiscale description of a single osteon of cortical bones. The cortical bone tissue is
modeled as a double-porous medium decomposed into the solid matrix and the fluid saturated canals. The resulting
homogenized model describes deformation of such medium in response to a static loading by external forces and
to an injection of slightly compressible fluid. Three numerical examples are presented, showing the influence of
selected lower-scales geometrical features on the macroscopic body behavior.2014-01-01T00:00:00ZTurjanicová, JanaRohan, EduardNaili, SalahModal parameters of a rotating multiple-disk-shaft system from simulated frequency response dataKhader, Naimhttp://hdl.handle.net/11025/119572019-10-02T10:58:02Z2014-01-01T00:00:00ZNázev: Modal parameters of a rotating multiple-disk-shaft system from simulated frequency response data
Autoři: Khader, Naim
Abstrakt: Modal parameters of a rotating multiple disk-shaft system are estimated in Multiple Input/Multiple Output (MIMO)
scheme. The response at multiple output degrees of freedom (dofs) and excitations at multiple input (reference)
dofs are related through the Frequency Response Function (FRF) matrix. The corresponding Impulse Response
Function (IRF) matrix is obtained by Inverse Fast Fourier Transform (IFFT) of the FRF matrix. The resulting
FRF matrix is not symmetric due to the gyroscopic effects introduced by rotation. The Eigensystem Realization
Algorithm (ERA) and its equivalent low order time domain algorithm, based on the Unified Matrix Polynomial
Approach (UMPA) are employed to estimate the desired modal parameters, i.e., system eigenvalues and the asso-
ciated right hand and left hand eigenvectors. The right hand vectors are estimated from multiple columns of the
FRF matrix with the structure rotating in one direction, and the left hand vectors are estimated from the multiple
rows of the FRF matrix, which are calculated as the transpose of the same multiple columns of the FRF matrix,
estimated with rotation in the opposite direction. The obtained results are found to be in excellent agreement with
results obtained from Theoretical Modal Analysis (TMA).2014-01-01T00:00:00ZKhader, Naim