Short and long term non-linear analysis of RR variability series

2002 ◽  
Vol 24 (1) ◽  
pp. 21-32 ◽  
Author(s):  
G. Baselli ◽  
S. Cerutti ◽  
A. Porta ◽  
M.G. Signorini
Keyword(s):  
Linear Analysis ◽  
Non Linear ◽  
Short And Long Term ◽  
Rr Variability

scholarly journals Short- and long-term variations in non-linear dynamics of heart rate variability

1996 ◽  
Vol 31 (3) ◽  
pp. 400-409 ◽  
Author(s):  
J. K. Kanters ◽  
M. V. Hojgaard ◽  
E. Agner ◽  
N.-H. Holstein-Rathlou
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Linear Dynamics ◽  
Non Linear ◽  
Short And Long Term ◽  
Long Term Variations

scholarly journals An application of a solar-type dynamo model for ε Eridani

2020 ◽  
Vol 497 (3) ◽  
pp. 3968-3975
Author(s):  
A P Buccino ◽  
L Sraibman ◽  
P M Olivar ◽  
F O Minotti
Keyword(s):  
Activity Cycle ◽  
Maunder Minimum ◽  
Dynamo Model ◽  
Dynamo Theory ◽  
Great Opportunity ◽  
Non Linear ◽  
Solar Type ◽  
Short And Long Term ◽  
Activity Cycles

ABSTRACT During the last decade, the relation between activity cycle periods and stellar parameters has received special attention. The construction of reliable registries of activity reveals that solar-type stars exhibit activity cycles with periods from few years to decades and, in some cases, long and short activity cycles coexist suggesting that two dynamos could operate in these stars. In particular, ε Eridani is an active young K2V star (0.8 Gyr), which exhibits short and long-term chromospheric cycles of ∼3 and ∼13-yr periods. Additionally, between 1985 and 1992, the star went through a broad activity minimum, similar to the solar Maunder Minimum state. Motivated by these results, we found in ε Eridani a great opportunity to test the dynamo theory. Based on the model developed in Sraibman & Minotti, in this work we built a non-linear axisymmetric dynamo for ε Eridani. The time series of the simulated magnetic field components near the surface integrated in all the stellar disc exhibits both the long and short activity cycles with periods similar to the ones detected from observations and also time intervals of low activity that could be associated with the broad Minimum. The short activity cycle associated with the magnetic reversal could be explained by the differential rotation, while the long cycle is associated with the meridional mass flows induced by the Lorentz force. In this way, we show that a single non-linear dynamo model derived from first principles with accurate stellar parameters could reproduce coexisting activity cycles.

scholarly journals Long Term Non Linear Thermal Effects in the Pulsation of Mira Variables

1995 ◽  
Vol 155 ◽  
pp. 139-140
Author(s):  
A. Yaari ◽  
Y. Tuchman
Keyword(s):  
Limit Cycle ◽  
Fundamental Mode ◽  
Thermal Effects ◽  
Linear Analysis ◽  
Dominant Mode ◽  
Mira Variables ◽  
Non Linear ◽  
Actual Limit ◽  
Good Agreement

The main conclusions that can be drawn from most of previous non-linear simulations of LPV (Keeley 1970, Rose & Smith 1972, Wood 1974, Tuchman et al. 1978, 1979) are the following:In all cases where the fundamental mode is predicted, by the linear analysis, to be the dominant, the pulsations are seen to diverge and lead to a rather violent mass-loss process (Wood 1974, Tuchman, Sack & Barkat 1979).A steady pulsation with (roughly) a limit cycle does set in only in those cases where the linear analysis predicts that the dominant mode (with the largest value of the growth rate) is the first overtone (or higher). In all these cases the actual limit cycle is found to be in a good agreement with the linear predictions, with regard to the pulsation mode and period (Wood 1974, Tuchman, Sack & Barkat 1979). However, it is important to note that periods, for these overtone pulsators, are always found to be smaller than 300 days (Wood 1974, Tuchman, Sack & Barkat 1979). Increasing the luminosity of these models, in order to increase their periods, results in a switch to the fundamental mode, followed by the violent relaxation oscillations, mentioned above.

Structural Integrity Management for a Large Pre-Stressed Concrete Floating Production Unit

2007 ◽  
Author(s):  
Bertrand Lanquetin ◽  
Pascal Collet ◽  
Jose Esteve
Keyword(s):  
High Performance ◽  
Structural Integrity ◽  
High Performance Concrete ◽  
Element Model ◽  
Linear Analysis ◽  
Production Unit ◽  
Non Linear ◽  
Integrity Management ◽  
Field Production

Offshore Floating Production Units, usually deployed under long-term plan, handle the field production so they cannot be easily removed for dry-docking and repair. In order to constantly analyze and monitor the condition of the units, a tailor-made methodology has been developed and implemented since 2004 for the Integrity Management of our Floating Units currently in operation. The paper gives a description of this methodology, and then focuses on how the methodology was deployed for the large pre-stressed concrete Floating Production Unit (FPU) located offshore Congo on N’KOSSA field. This FPU is the largest existing pre-stressed concrete Floating Production Unit, built with high performance concrete, installed offshore since 1996 in 170 m water depth. She has now accumulated 10 years of production. A significant part of the methodology is based on a full Finite Element Model (FEM) with non-linear analysis capacity for the concrete structure, incorporating a description of passive and active steel. There is often an anchored perception that a concrete unit is something not requiring attention once installed. This paper shows otherwise, underlining the complexity of modeling the highly non linear characteristics of pre-stressed high performance concrete and degradation modes.

Short- and Long-Term Results of Total vs Subtotal Thyroid- ectomies in the Surgical Treatment of Graves' Disease

Swiss Surgery ◽  
2001 ◽  
Vol 7 (1) ◽  
pp. 20-24 ◽  
Author(s):  
Robert ◽  
Mariéthoz ◽  
Pache ◽  
Bertin ◽  
Caulfield ◽  
...  
Keyword(s):  
Recurrent Laryngeal Nerve ◽  
Nerve Palsy ◽  
Recurrent Laryngeal Nerve Palsy ◽  
Laryngeal Nerve ◽  
Long Term Results ◽  
Graves Disease ◽  
Laryngeal Nerve Palsy ◽  
Short And Long Term

Objective: Approximately one out of five patients with Graves' disease (GD) undergoes a thyroidectomy after a mean period of 18 months of medical treatment. This retrospective and non-randomized study from a teaching hospital compares short- and long-term results of total (TT) and subtotal thyroidectomies (ST) for this disease. Methods: From 1987 to 1997, 94 patients were operated for GD. Thirty-three patients underwent a TT (mostly since 1993) and 61 a ST (keeping 4 to 8 grams of thyroid tissue - mean 6 g). All patients had received propylthiouracil and/or neo-mercazole and were in a euthyroid state at the time of surgery; they also took potassium iodide (lugol) for ten days before surgery. Results: There were no deaths. Transient hypocalcemia (< 3 months) occurred in 32 patients (15 TT and 17 ST) and persistent hypocalcemia in 8 having had TT. Two patients developed transient recurrent laryngeal nerve palsy after ST (< 3 months). After a median follow-up period of seven years (1-15) with five patients lost to follow-up, 41 patients having had a ST are in a hypothyroid state (73%), thirteen are euthyroid (23%), and two suffered recurrent hyperthyroidism, requiring completion of thyroidectomy. All 33 patients having had TT - with follow-ups averaging two years (0.5-8) - are receiving thyroxin substitution. Conclusions: There were no instances of persistent recurrent laryngeal nerve palsy in either group, but persistent hypoparathyroidism occurred more frequently after TT. Long after ST, hypothyroidism developed in nearly three of four cases, whereas euthyroidy was maintained in only one-fourth; recurrent hyperthyroidy was rare.

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