scholarly journals Effective time‐domain approach for the assessment of the stability characteristics and other non‐linear effects of RF and microwave circuits

2019 ◽  
Vol 13 (14) ◽  
pp. 2470-2479 ◽  
Author(s):  
Leonardo Pantoli ◽  
Domenico Spina ◽  
Daniele Romano ◽  
Giulio Antonini ◽  
Giorgio Leuzzi ◽  
...  
Keyword(s):  
Time Domain ◽  
Microwave Circuits ◽  
Effective Time ◽  
Non Linear ◽  
Linear Effects ◽  
The Stability

Linear and Nonlinear Stability Analysis of a Self-Pressurized, Natural Circulation, Integral Reactor

2004 ◽  
Author(s):  
Pablo Zanocco ◽  
Dari´o Delmastro ◽  
Marcelo Gime´nez
Keyword(s):  
Time Domain ◽  
Amplification Factor ◽  
Natural Circulation ◽  
The Self ◽  
The Core ◽  
Non Linear ◽  
Pressure Feedback ◽  
Linear Effects ◽  
The Stability ◽  
Integral Reactor

The stability of a self-pressurized, integral reactor cooled by natural circulation is analyzed. CAREM reactor prototype is taken as reference for the present study. Because of the self-pressurization condition, the system is very close to saturation, and some boiling occurs along the hot leg - reactor core and riser -. Possible instabilities caused by this condition are analyzed in this work in the nominal pressure, with special attention to some particular issues of this design. A numerical code is developed to describe the reactor dynamics and it is briefly described. It includes the coolant with a one-dimensional scheme, steam dome and core modelling, considering the flashing phenomena, neutronic and pressure feedbacks. The code numerically solves the whole set of non-linear equations in a time-domain approach; it also includes a linearization method by numerical perturbations, then a classical frequency-domain stability analysis can be also carried out for the linearized system, by means of eigenvalues calculation. The amplification factor for the oscillation is plotted in the core power/steam dome condensation parameter-plane. A parametric study is carried out, to analyze the influence of core dynamic and the pressure feedback due to the self-pressurization. The pressure feedback has a stabilizing effect, increasing stability for smaller steam volumes. The core dynamic has a stabilizing effect when the core power and the steam dome condensation are low, and relatively destabilizing when they are higher. The stability boundary is determined, for several cases. The amplification factor is enlarged in the region where the flashing phenomenon occurs. The dynamic non-linear effects are studied by means of a time-domain approach, for selected conditions in growing and damped oscillations. The limit-cycle for the growing oscillations is determined, and the main non-linear sources are studied: the amplitude is restricted by strong non-linear effects, which appear when the boiling boundary crosses the core-riser limit, and more than one boiling point coexists at the same time, bounding the amplitude of oscillation to values that would remain un-noticed in case of being present in the reactor.

On the Stability of Fast Ferry in Damage Scenarios

2015 ◽  
Vol 157 (A3) ◽  
pp. 153-160
Keyword(s):  
Time Domain ◽  
Critical Condition ◽  
Regular Wave ◽  
Loss Of Life ◽  
Damage Scenarios ◽  
Linear Effects ◽  
Ship Grounding ◽  
The Stability ◽  
Heeling Moment ◽  
Damaged Ship

"The ro-ro ships are characterized by a large garage compartment extending from stern to bow. Damage conditions, heavy weather and large floodable spaces could create serious accidents, with the loss of life and goods at sea, both for conventional ferries and fast ferries. The occurred accidents showed the need of a more accurate approach to the damaged ship stability in waves, also in head sea and following sea conditions, because of the great movements of water on the car deck. With this aim a tool for analysing the ship response in wave with damaged compartments has been developed and applied on a typical fast ferry. The ship dynamic is simulated in time domain, including non-linear effects, taking into account critical scenarios on the damaged ship. The applications regard ship grounding, assuming head sea, modelled by regular wave. In addition to that, also the particularly critical condition of a transversal wind heeling moment has been applied to compute non symmetrical behaviour. Moreover the stability problems arising from the presence of trapped water in the garage compartment are investigated assuming the same environmental scenarios."

ON THE STABILITY OF FAST FERRY IN DAMAGE SCENARIOS

2021 ◽  
Vol 157 (A3) ◽  
Author(s):  
M Acanfora ◽  
F De Luca
Keyword(s):  
Time Domain ◽  
Critical Condition ◽  
Regular Wave ◽  
Loss Of Life ◽  
Damage Scenarios ◽  
Linear Effects ◽  
Ship Grounding ◽  
The Stability ◽  
Heeling Moment ◽  
Damaged Ship

The ro-ro ships are characterized by a large garage compartment extending from stern to bow. Damage conditions, heavy weather and large floodable spaces could create serious accidents, with the loss of life and goods at sea, both for conventional ferries and fast ferries. The occurred accidents showed the need of a more accurate approach to the damaged ship stability in waves, also in head sea and following sea conditions, because of the great movements of water on the car deck. With this aim a tool for analysing the ship response in wave with damaged compartments has been developed and applied on a typical fast ferry. The ship dynamic is simulated in time domain, including non-linear effects, taking into account critical scenarios on the damaged ship. The applications regard ship grounding, assuming head sea, modelled by regular wave. In addition to that, also the particularly critical condition of a transversal wind heeling moment has been applied to compute non symmetrical behaviour. Moreover the stability problems arising from the presence of trapped water in the garage compartment are investigated assuming the same environmental scenarios.

A Higher Order Time Domain Rankine Panel Method for Linear and Weakly Non-Linear Computation

2015 ◽  
Author(s):  
Felipe Ruggeri ◽  
Rafael A. Watai ◽  
Alexandre N. Simos
Keyword(s):  
Time Domain ◽  
Domain Boundary ◽  
Higher Order ◽  
Floating Body ◽  
Wave Runup ◽  
Floating Bodies ◽  
B Splines ◽  
Non Linear ◽  
Boundary Elements Method ◽  
Linear Effects

This paper presents a higher order time domain boundary elements method based on the Rankine sources for the computation of both linear and weakly non-linear effects for both fixed and free floating bodies. The geometry is described based on surfaces in a standard iges file, considering a NURBS (Non Uniform Rational Basis-Spline) description. The potential function, velocity, free-surface elevation and other quantities are defined using b-splines of arbitrary degree and the floating body interaction is solved using the potential acceleration approach on a Runge-Kutta scheme for time evolution. The integral equation is obtained and solved considering several possibilities for the collocation points, leading to an over-determined system. The integration over the panels is performed using a mixed desingularized-numerical method over Gaussian points. The results comparison are performed with WAMIT solution for a floating sphere concerning wave runup, body motions, velocity field, mean drift components in time domain.

Investigation of the stability of periodic motions in a nonlinear automatic control system based on the fast fourier transform

2003 ◽  
Vol 3 ◽  
pp. 297-307
Author(s):  
V.V. Denisov
Keyword(s):  
Fourier Transform ◽  
Control System ◽  
Automatic Control ◽  
Fast Fourier Transform ◽  
Automatic Control System ◽  
Resonance Phenomenon ◽  
Periodic Motions ◽  
Multiply Connected ◽  
Non Linear ◽  
The Stability

An approach to the study of the stability of non-linear multiply connected systems of automatic control by means of a fast Fourier transform and the resonance phenomenon is considered.

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