Search results for "Instability"
showing 10 items of 724 documents
Generation of optical domain-wall structures from modulational instability in a bimodal fiber.
1998
We study experimentally modulational instability in a normally dispersive bimodal fiber under modal group-velocity-matching conditions. In the strong pump depletion regime, higher order sideband harmonics detected in the output spectra as well as autocorrelation measurements reveal the formation of subpicosecond domain-wall structures. Across these temporal structures the electromagnetic field distribution switches abruptly between the two transverse modes of the fiber. These structures are reminiscent of the so-called domain-wall soliton. Our results constitute therefore an experimental indication of the existence of this fundamental soliton.
Comunicar : revista científica iberoamericana de comunicación y educación
2021
En el marco de la escuela inclusiva, el aprendizaje socioemocional y personalizado fomenta la implicación del alumnado en la vida del aula y se relaciona con la disminución de la conducta desadaptativa. El objetivo de este estudio es analizar el impacto de un programa de educación socioemocional en la agresividad y la inestabilidad emocional en la infancia. Han participado 555 niños/as de 7 a 12 años (M=9,2 y DT=1,5), 55,5% niños y 45,5% niñas. Estudian Educación Primaria en seis colegios públicos del área metropolitana de Valencia (España). La muestra se ha distribuido en un grupo experimental (317 niños/as; 57,2% de la población total participante) y un grupo control (238 niños/as; 42,8% …
Persistent Employment Instability and Fertility Intentions: The Gender-Specific Effect within Couples in Italy
2014
Our paper adds to the growing literature on the measurement of employment instability and on that on its consequences on fertility dynamics. We argue that many of these studies disregard a crucial dimension of employment instability: its persistence (duration). It is the persistence in an unstable condition, more than the status itself, that may have the most severe consequences on subsequent family choices. In this paper, we propose an index of persistence in employment instability that synthesizes all the information inside the individual sequence of employment statuses in a single number accounting simultaneously for the duration, sequencing, intensity, and labour market circumstances. T…
Fuzzy control for Electric Power Steering System with assist motor current input constraints
2015
Abstract Friction and disturbances of the road are the main sources of nonlinearity in the Electric Power Steering (EPS) System. Consequently, conventional linear controllers design based on a simplified linear model of the EPS system will result in poor dynamic performance or system instability. On the other hand, a brush-type DC motor is more used in EPS control with an input current that is limited in practice. The control laws designed without taking into account the saturation effect may have undesirable consequences on the system stability. In this paper, a Takagi–Sugeno (T−S) fuzzy is used to represent the nonlinear behavior of an EPS system, and stabilization conditions for nonlinea…
On the sway stability improvement of car–caravan systems by articulated connections
2015
The present analysis is addressed to some promising connection arrangements between the towing vehicles and the towed trailers, where the two units are linked by four-bar isosceles trapeziums in place of the conventional pintle hitch. Two types of instability, of the divergent type or the oscillating type, may be analysed by the Routh–Hurwitz criterion or by the direct analysis of the characteristic equation. The constant term of this equation vanishes at the divergent instability threshold (zero of a real root), whereas the equation splits into two lower degree algebraic ‘sub-equations’ when the oscillating instability arises (pair of pure imaginary roots). A large field of geometrical con…
Velocity sensorless control of uncertain load using RKF tuned with an evolutionary algorithm and mu-analysis
2010
Abstract In case of a velocity control scheme for a load directly driven by an actuator, large variations of its parameters are problematic due to possible instability and large variations of the final performances. This performances are then decreasing if a sensorless control is implemented due to cost, reliability or application constraints. This paper proposes solutions to quickly and accurately tune an observer with a lower computer time consumption and lower conception time. A previous calculated state feedback is used as base for a Kalman filter with special noise matrices. An evolutionary algorithm optimizes the observers degrees of freedom all over the variations. The mu-analysis th…
Losing DNA methylation at repetitive elements and breaking bad
2021
Abstract Background DNA methylation is an epigenetic chromatin mark that allows heterochromatin formation and gene silencing. It has a fundamental role in preserving genome stability (including chromosome stability) by controlling both gene expression and chromatin structure. Therefore, the onset of an incorrect pattern of DNA methylation is potentially dangerous for the cells. This is particularly important with respect to repetitive elements, which constitute the third of the human genome. Main body Repetitive sequences are involved in several cell processes, however, due to their intrinsic nature, they can be a source of genome instability. Thus, most repetitive elements are usually meth…
Why are viral genomes so fragile? The bottleneck hypothesis
2021
If they undergo new mutations at each replication cycle, why are RNA viral genomes so fragile, with most mutations being either strongly deleterious or lethal? Here we provide theoretical and numerical evidence for the hypothesis that genetic fragility is partly an evolutionary response to the multiple population bottlenecks experienced by viral populations at various stages of their life cycles. Modelling within-host viral populations as multi-type branching processes, we show that mutational fragility lowers the rate at which Muller’s ratchet clicks and increases the survival probability through multiple bottlenecks. In the context of a susceptible-exposed-infectious-recovered epidemiolog…
Parenting style and peer attachment as predictors of emotional instability in children
2017
We analyzed the roles of parenting style and peer attachment in predicting emotional instability in late childhood and early adolescence. Effects were analyzed separately by gender. Children's personal variables analyzed were empathy, anger, and the mechanisms used to cope with anger (externalization and self-control). Participants were 316 girls and 294 boys (N = 610) aged from 9 to 12 years who were students at schools in Valencia, Spain. Main gender differences for each variable were examined using one-way ANOVAs. Results of 2 multiple linear regression analyses (1 for boys and 1 for girls) explained 50.9% and 35.5%, respectively, of variance in the students' emotional instability. Consi…
Magnetic field dynamos and magnetically triggered flow instabilities
2017
The project A2 of the LIMTECH Alliance aimed at a better understanding of those magnetohydrodynamic instabilities that are relevant for the generation and the action of cosmic magnetic fields. These comprise the hydromagnetic dynamo effect and various magnetically triggered flow instabilities, such as the magnetorotational instability and the Tayler instability. The project was intended to support the experimental capabilities to become available in the framework of the DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN). An associated starting grant was focused on the dimensioning of a liquid metal experiment on the newly found magnetic destabilization of rotating flow…