856 resultados para Absolute stability


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Using the solutions of the gap equations of the magnetic-color-flavor-locked (MCFL) phase of paired quark matter in a magnetic field, and taking into consideration the separation between the longitudinal and transverse pressures due to the field-induced breaking of the spatial rotational symmetry, the equation of state of the MCFL phase is self-consistently determined. This result is then used to investigate the possibility of absolute stability, which turns out to require a field-dependent ""bag constant"" to hold. That is, only if the bag constant varies with the magnetic field, there exists a window in the magnetic field vs bag constant plane for absolute stability of strange matter. Implications for stellar models of magnetized (self-bound) strange stars and hybrid (MCFL core) stars are calculated and discussed.

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Bien qu’il y ait de plus en plus d’études sur le soutien maternel à l’autonomie, de nombreuses questions restent à éclaircir dans le domaine. Notamment, on en sait très peu sur ses relations avec le développement cognitif de l’enfant, sa stabilité temporelle et les antécédents de celle-ci. La thèse est composée de trois articles empiriques. Le premier explore le rôle médiateur du langage dans la relation entre le soutien maternel à l'autonomie et les fonctions exécutives de l'enfant. Le deuxième examine la stabilité relative et absolue du soutien maternel à l'autonomie entre la petite enfance et l’âge préscolaire en fonction des représentations d'attachement de la mère, des évènements de vie stressants et du sexe de l'enfant. Le troisième article se penche sur le rôle du soutien maternel à l’autonomie mesuré à la petite enfance et à l’âge préscolaire dans la prédiction des fonctions exécutives de l’enfant, ainsi que sur l’impact de différents patrons de stabilité du soutien maternel à l’autonomie sur les fonctions exécutives. 70 dyades mère-enfant ont participé à 5 visites à domicile. Lorsque l’enfant était âgé de 7-8 mois, les représentations d’attachement de la mère ont été mesurées à l’aide de l’entrevue d’attachement à l’âge adulte (George, Kaplan, & Main, 1996). Le soutien maternel à l’autonomie a été mesuré à 15 mois et à 3 ans à l’aide du système de codification de Whipple, Bernier, et Mageau (2011). Les évènements de vie stressants ont été mesurés à 3 reprises entre l’âge de 15 mois et 3 ans à l’aide de l’inventaire des expériences de vie (Sarason, Johnson, & Siegel, 1978). À 2 ans, le langage de l’enfant a été évalué à l’aide des inventaires MacArthur du développement de la communication (Dionne, Tremblay, Boivin, Laplante, & Pérusse, 2003). Les fonctions exécutives de l’enfant ont quant à elles été mesurées à l’âge de 3 ans à l’aide d’une batterie de tâches (Carlson, 2005). Les résultats du premier article indiquent que le langage de l’enfant joue un rôle médiateur dans la relation entre le soutien maternel à l’autonomie et une composante des fonctions exécutives de l’enfant, l’inhibition volontaire. Les résultats du deuxième article démontrent que le soutien maternel à l’autonomie est stable de façon relative, mais non absolue. Les résultats démontrent aussi que les mères qui ont une fille, qui ont vécu peu d’évènements de vie stressants ou qui ont des représentations d’attachement sécurisées sont plus stables dans leur degré de soutien à l’autonomie. Le troisième article démontre d’abord que la moyenne de soutien maternel à l’autonomie entre 15 mois et 3 ans est un prédicteur plus efficace des fonctions exécutives de l’enfant que ne l’est le soutien à l’autonomie à 15 mois ou à 3 ans pris séparément. De plus, les enfants dont les mères conservent un degré élevé de soutien à l’autonomie entre 15 mois et 3 ans performent mieux aux tâches d’inhibition que les enfants dont les mères conservent un faible degré de soutien à l’autonomie. Les résultats présentés dans les articles sont discutés ainsi que leurs implications.

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This research presents a systematic procedure to obtain estimates, via extended Lyapunov functions, of attracting sets of a class of nonlinear systems, as well as an estimate of their stability regions. The considered class of nonlinear systems, called in this note the extended Lurie system, consists of nonlinear systems like those of the Lurie problem where one of the nonlinear functions can violate the sector conditions of the Lurie problem around the origin. In case of nonautonomous systems the concept of absolute stability is extended and uniform estimates of the attracting set are obtained. Two classical nonlinear systems, the forced duffing equation and the Van der Pol system, are analyzed with the proposed procedure.

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The quark gluon plasma (QGP) at zero temperature and high baryon number is a system that may be present inside compact stars. It is quite possible that this cold QGP shares some relevant features with the hot QGP observed in heavy ion collisions, being also a strongly interacting system. In a previous work we have derived from the QCD Lagrangian an equation of state (EOS) for the cold QGP, which can be considered an improved version of the MIT bag-model EOS. Compared to the latter, our EOS reaches higher values of the pressure at comparable baryon densities. This feature is due to perturbative corrections and also to nonperturbative effects. Here we apply this EOS to the study of neutron stars, discussing the absolute stability of quark matter and computing the mass-radius relation for self-bound (strange) stars. The maximum masses of the sequences exceed two solar masses, in agreement with the recently measured values of the mass of the pulsar PSR J1614-2230, and the corresponding radii of around 10-11 km.

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Power electronic converters are extensively adopted for the solution of timely issues, such as power quality improvement in industrial plants, energy management in hybrid electrical systems, and control of electrical generators for renewables. Beside nonlinearity, this systems are typically characterized by hard constraints on the control inputs, and sometimes the state variables. In this respect, control laws able to handle input saturation are crucial to formally characterize the systems stability and performance properties. From a practical viewpoint, a proper saturation management allows to extend the systems transient and steady-state operating ranges, improving their reliability and availability. The main topic of this thesis concern saturated control methodologies, based on modern approaches, applied to power electronics and electromechanical systems. The pursued objective is to provide formal results under any saturation scenario, overcoming the drawbacks of the classic solution commonly applied to cope with saturation of power converters, and enhancing performance. For this purpose two main approaches are exploited and extended to deal with power electronic applications: modern anti-windup strategies, providing formal results and systematic design rules for the anti-windup compensator, devoted to handle control saturation, and “one step” saturated feedback design techniques, relying on a suitable characterization of the saturation nonlinearity and less conservative extensions of standard absolute stability theory results. The first part of the thesis is devoted to present and develop a novel general anti-windup scheme, which is then specifically applied to a class of power converters adopted for power quality enhancement in industrial plants. In the second part a polytopic differential inclusion representation of saturation nonlinearity is presented and extended to deal with a class of multiple input power converters, used to manage hybrid electrical energy sources. The third part regards adaptive observers design for robust estimation of the parameters required for high performance control of power systems.

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This paper is intended to provide conditions for the stability of the strong uniqueness of the optimal solution of a given linear semi-infinite optimization (LSIO) problem, in the sense of maintaining the strong uniqueness property under sufficiently small perturbations of all the data. We consider LSIO problems such that the family of gradients of all the constraints is unbounded, extending earlier results of Nürnberger for continuous LSIO problems, and of Helbig and Todorov for LSIO problems with bounded set of gradients. To do this we characterize the absolutely (affinely) stable problems, i.e., those LSIO problems whose feasible set (its affine hull, respectively) remains constant under sufficiently small perturbations.

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Introdução: As experiências adversas na infância, tal como a exposição a acontecimentos traumáticos e vivências de vergonha, podem ter um contributo importante na vida dos adolescentes moldando a forma estes se percecionam a si próprios e aos outros, e como lidam com as adversidades, podendo aumentar a sua vulnerabilidade para desenvolver uma perturbação depressiva. Este estudo, de desenho longitudinal, consistiu em estudar os factores preditores (acontecimentos de vida traumáticos e sentimentos de vergonha) no desenvolvimento de psicopatologia depressiva a seis meses. Método: A amostra é constituída por 325 adolescentes, com idades compreendidas entre os 12 e os 18 anos a frequentar o 3º ciclo do ensino básico e ensino secundário. Para o estudo das variáveis referidas, foram utilizados os seguintes instrumentos de medida: o Child Depression Inventory, o Childhood Trauma Questionaire e a Escala de Vergonha Externa. Resultados: Os resultados obtidos relativamente à estabilidade absoluta das variáveis demonstram diferenças significativas entre os valores médios do 1ºmomento de avaliação e do 2º momento de avaliação (após 6 meses) para a variável vergonha. Ao longo do estudo, verificou-se uma associação positiva entre as variáveis relacionadas com o trauma e os sentimentos de vergonha avaliados no primeiro tempo (T1) e a variável sintomas depressivos (T2). O modelo de regressão linear múltipla, explicou 63% da variância dos sintomas depressivos no tempo 2, mostrando que o facto de pertencer ao sexo feminino, experienciar mais vivências de vergonha, e mais experiências traumáticas de abuso afetivo, abuso sexual e de negligência emocional permitem predizer mais sintomas depressivos na adolescência. Conclusão: Podemos concluir com a presente investigação, que o impacto de acontecimentos traumáticos, do tipo abuso/negligência, bem como de sentimentos de vergonha durante a fase da adolescência pode ser nocivo para o desenvolvimento harmonioso posterior, nomeadamente no desenvolvimento de sintomatologia depressiva. / Introduction: The adverse experiences in childhood, such as an exhibition of traumatic events and experiences of sham can have important contribution in teenager’s life shaping the way they perceive themselves and the others and how they deal with adversity, increasing their vulnerability to develop a depressive disorder. This study, longitudinal design, it was consisted in study of the predictive factors (traumatic life events and feelings of shame) in the development of depressive psychopathology in six months. Method: The sample consisted of 325 adolescents aged between 12 and 18 years attending the 3rd cycle of basic education and secondary education. To the study of the variables mentioned, the following measuring instruments were used: the Child Depression Inventory, the Childhood Trauma Questionnaire and External Shame Scale. Results: The results obtained regarding the absolute stability of the variables showed significant differences between the mean values of the evaluation 1st moment and 2nd moment of evaluation (after 6 months) for the variable shame. Throughout the study, there was a positive association between variables related to the trauma and feelings of shame evaluated at the first time (T1) and the variable depressive symptoms (T2). The multiple linear regression model explained 63% of variance in depressive symptoms at time 2 , showing that the fact of being female experience more shame experiences, and most traumatic experiences of emotional abuse, sexual abuse and emotional neglect permit predict more depressive symptoms in adolescence. Conclusion: We can conclude with this research, that the impact of traumatic events, the type abuse/neglect, as well as feelings of shame during adolescence can be harmful to the subsequent harmonious development, including the development of depressive symptoms.

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La publicación de una nueva ley, trae consigo la derogatoria total o parcial de otra ley y con ello, la imperiosa necesidad de conocer aquella reforma que cambia la realidad jurídica respecto de la materia que rige. Tal es el caso de la Ley Orgánica de Justicia Laboral y Reconocimiento del Trabajo en el Hogar, publicada en abril de 2015, que modificó el Código de Trabajo y la Ley de Seguridad Social, siendo uno de los temas más relevantes de esta reforma, el despido ineficaz. El tema de estabilidad laboral absoluta en Ecuador, era únicamente una ilusión para los trabajadores, y a palabras de un gran catedrático de la Facultad de Jurisprudencia de la Universidad de Cuenca, Doctor Jorge Morales, la estabilidad absoluta era “simples mariposas amarillas”; sin embargo, desde abril del 2015, la estabilidad absoluta pasó de la teoría a la praxis, aunque únicamente para un grupo mínimo de trabajadores, representantes sindicales y mujeres embarazadas o asociadas a su condición de maternidad;debido que, por su condición de vulnerabilidad en el marco laboral, la Reforma transformala estabilidad relativa manifestada en el despido intempestivo de estos trabajadores en ineficaz. “La ley, una vez publicada se presume conocida por todos y no podrá alegarse ignorancia por ninguna persona”, todos los ciudadanos dentro de la circunscripción para la cual rige la nueva norma, tenemos la obligación de informarnos sobre tal, siendo este, el motivo y objetivo principal de la presente investigación, otorgar a la ciudadanía un análisis profundo de la reforma laboral precisamente sobre las disposiciones que regulan la aplicación, alcance, causas y efectos del despido ineficaz.

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We propose a self-reference multiplexed fibre interferometer (MFI) by using a tunable laser and fibre Bragg grating (FBG). The optical measurement system multiplexes two Michelson fibre interferometers with shared optical path in the main part of optical system. One fibre optic interferometer is used as a reference interferometer to monitor and control the high accuracy of the measurement system under environmental perturbations. The other is used as a measurement interferometer to obtain information from the target. An active phase tracking homodyne (APTH) technique is applied for signal processing to achieve high resolution. MFI can be utilised for high precision absolute displacement measurement with different combination of wavelengths from the tuneable laser. By means of Wavelength-Division-Multiplexing (WDM) technique, MFI is also capable of realising on-line surface measurement, in which traditional stylus scanning is replaced by spatial light-wave scanning so as to greatly improve the measurement speed and robustness.

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We propose a self-reference multiplexed fibre interferometer (MFI) by using a tunable laser and fibre Bragg grating (FBG). The optical measurement system multiplexes two Michelson fibre interferometers with shared optical path in the main part of optical system. One fibre optic interferometer is used as a reference interferometer to monitor and control the high accuracy of the measurement system under environmental perturbations. The other is used as a measurement interferometer to obtain information from the target. An active phase tracking homodyne (APTH) technique is applied for signal processing to achieve high resolution. MFI can be utilised for high precision absolute displacement measurement with different combination of wavelengths from the tuneable laser. By means of Wavelength-Division-Multiplexing (WDM) technique, MFI is also capable of realising on-line surface measurement, in which traditional stylus scanning is replaced by spatial light-wave scanning so as to greatly improve the measurement speed and robustness. © 2004 Optical Society of America.

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The recognition of temporally stable locations with respect to soil water content is of importance for soil water management decisions, especially in sloping land of watersheds. Neutron probe soil water content (0 to 0.8 m), evaluated at 20 dates during a year in the Loess Plateau of China, in a 20 ha watershed dominated by Ust-Sandiic Entisols and Aeolian sandy soils, were used to define their temporal stability through two indices: the standard deviation of relative difference (SDRD) and the mean absolute bias error (MABE). Specific concerns were (a) the relationship of temporal stability with soil depth, (b) the effects of soil texture and land use on temporal stability, and (c) the spatial pattern of the temporal stability. Results showed that temporal stability of soil water content at 0.2 m was significantly weaker than those at the soil depths of 0.6 and 0.8 m. Soil texture can significantly (P<0.05) affect the stability of soil water content except for the existence of an insignificant difference between sandy loam and silt loam textures, while temporal stability of areas covered by bunge needlegrass land was not significantly different from those covered by korshinsk peashrub. Geostatistical analysis showed that the temporal stability was spatially variable in an organized way as inferred by the degree of spatial dependence index. With increasing soil depth, the range of both temporal stability indices showed an increasing trend, being 65.8-120.5 m for SDRD and 148.8-214.1 m for MABE, respectively. This study provides a valuable support for soil water content measurements for soil water management and hydrological applications on sloping land areas. (C) 2010 Elsevier B.V. All rights reserved.

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The knowledge of soil water storage (SWS) of soil profiles is crucial for the adoption of vegetation restoration practices. With the aim of identifying representative sites to obtain the mean SWS of a watershed, a time stability analysis of neutron probe evaluations of SWS was performed by the means of relative differences and Spearman rank correlation coefficients. At the same time, the effects of different neutron probe calibration procedures were explored on time stability analysis. mean SWS estimation. and preservation of the spatial variability of SWS. The selected watershed, with deep gullies and undulating slopes which cover an area of 20 ha, is characterized by an Ust-Sandiic Entisol and an Aeolian sandy soil. The dominant vegetation species are bunge needlegrass (Stipa bungeana Trim) and korshinsk peashrub (Carugano Korshinskii kom.). From June 11, 2007 to July 23,2008, SWS of the top1 m soil layer was evaluated for 20 dates, based on neutron probe data of 12 sampling sites. Three calibration procedures were employed: type 1, most complete, with each site having its own linear calibration equation (TrE); type II. with TrE equations extended over the whole field: and type III, with one single linear calibration curve for the whole field (UnE) and also correcting its intercept based on site specific relative difference analysis (RdE) and on linear fitting of data (RcE), both maintaining the same slope. A strong time stability of SWS estimated by TrE equations was identified. Soil particle size and soil organic matter content were recognized as the influencing factors for spatial variability of SWS. Land use influenced neither the spatial variability nor the time stability of SWS. Time stability analysis identified one site to represent the mean SWS of the whole watershed with mean absolute percentage errors of less than 10%, therefore. this site can be used as a predictor for the mean SWS of the watershed. Some equations of type II were found to be unsatisfactory to yield reliable mean SWS values or in preserving the associated soil spatial variability. Hence, it is recommended to be cautious in extending calibration equations to other sites since they might not consider the field variability. For the equations with corrected intercept (type III), which consider the spatial variability of calibration in a different way in relation to TrE, it was found that they can yield satisfactory means and standard deviation of SWS, except for the RdE equations, which largely leveled off the SWS values in the watershed. Correlation analysis showed that the neutron probe calibration was linked to soil bulk density and to organic matter content. Therefore, spatial variability of soil properties should be taken into account during the process of neutron probe calibration. This study provides useful information on the mean SWS observation with a time stable site and on distinct neutron probe calibration procedures, and it should be extended to soil water management studies with neutron probes, e.g., the process of vegetation restoration in wider area and soil types of the Loess Plateau in China. (C) 2009 Elsevier B.V. All rights reserved.

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The blending of coals has become popular to improve the performance of coals, to meet specifications of power plants and, to reduce the cost of coals, This article reviews the results and provides new information on ignition, flame stability, and carbon burnout studies of blended coals. The reviewed studies were conducted in laboratory-, pilot-, and full-scale facilities. The new information was taken in pilot-scale studies. The results generally show that blending a high-volatile coal with a low-volatile coal or anthracite can improve the ignition, flame stability and burnout of the blends. This paper discusses two general methods to predict the performance of blended coals: (1) experiment; and (2) indices. Laboratory- and pilot-scale tests, at least, provide a relative ranking of the combustion performance of coal/blends in power station boilers. Several indices, volatile matter content, heating value and a maceral index, can be used to predict the relative ranking of ignitability and flame stability of coals and blends. The maceral index, fuel ratio, and vitrinite reflectance can also be used to predict the absolute carbon burnout of coal and blends within limits. (C) 2000 Elsevier Science Ltd. All rights reserved.

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Decline in gait stability has been associated with increased fall risk in older adults. Reliable and clinically feasible methods of gait instability assessment are needed. This study evaluated the relative and absolute reliability and concurrent validity of the testing procedure of the clinical version of the Narrow Path Walking Test (NPWT) under single task (ST) and dual task (DT) conditions. Thirty independent community-dwelling older adults (65-87 years) were tested twice. Participants were instructed to walk within the 6-m narrow path without stepping out. Trial time, number of steps, trial velocity, number of step errors, and number of cognitive task errors were determined. Intraclass correlation coefficients (ICCs) were calculated as indices of agreement, and a graphic approach called "mountain plot" was applied to help interpret the direction and magnitude of disagreements between testing procedures. Smallest detectable change and smallest real difference (SRD) were computed to determine clinically relevant improvement at group and individual levels, respectively. Concurrent validity was assessed using Performance Oriented Mobility Assessment Tool (POMA) and the Short Physical Performance Battery (SPPB). Test-retest agreement (ICC1,2) varied from 0.77 to 0.92 in ST and from 0.78 to 0.92 in DT conditions, with no apparent systematic differences between testing procedures demonstrated by the mountain plot graphs. Smallest detectable change and smallest real change were small for motor task performance and larger for cognitive errors. Significant correlations were observed for trial velocity and trial time with POMA and SPPB. The present results indicate that the NPWT testing procedure is highly reliable and reproducible.

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The only currently available method to measure brain glycogen in vivo is 13C NMR spectroscopy. Incorporation of 13C-labeled glucose (Glc) is necessary to allow glycogen measurement, but might be affected by turnover changes. Our aim was to measure glycogen absolute concentration in the rat brain by eliminating label turnover as variable. The approach is based on establishing an increased, constant 13C isotopic enrichment (IE). 13C-Glc infusion is then performed at the IE of brain glycogen. As glycogen IE cannot be assessed in vivo, we validated that it can be inferred from that of N-acetyl-aspartate IE in vivo: After [1-13C]-Glc ingestion, glycogen IE was 2.2 +/- 0.1 fold that of N-acetyl-aspartate (n = 11, R(2) = 0.77). After subsequent Glc infusion, glycogen IE equaled brain Glc IE (n = 6, paired t-test, p = 0.37), implying isotopic steady-state achievement and complete turnover of the glycogen molecule. Glycogen concentration measured in vivo by 13C NMR (mean +/- SD: 5.8 +/- 0.7 micromol/g) was in excellent agreement with that in vitro (6.4 +/- 0.6 micromol/g, n = 5). When insulin was administered, the stability of glycogen concentration was analogous to previous biochemical measurements implying that glycogen turnover is activated by insulin. We conclude that the entire glycogen molecule is turned over and that insulin activates glycogen turnover.