Controlling Multistability in a Vibro-Impact Capsule System

This is the final version of the article. Available from Springer Verlag via the DOI in this record.This work concerns the control of multistability in a vibro-impact capsule system driven by a harmonic excitation. The capsule is able to move forward and backward in a rectilinear direction, and the main objective of this work is to control such motion in the presence of multiple coexisting periodic solutions. A position feedback controller is employed in this study, and our numerical investigation demonstrates that the proposed control method gives rise to a dynamical scenario with two coexisting solutions, corresponding to forward and backward progression. Therefore, the motion direction of the system can be controlled by suitably perturbing its initial conditions, without altering the system parameters. To study the robustness of this control method, we apply numerical continuation methods in order to identify a region in the parameter space in which the proposed controller can be applied. For this purpose, we employ the MATLAB-based numerical platform COCO, which supports the continuation and bifurcation detection of periodic orbits of non-smooth dynamical systems.The second author has been supported by a Georg Forster Research Fellowship granted by the Alexander von Humboldt Foundation, Germany. The authors would like to thank Dr. Haibo Jiang for stimulating discussions and comments on this work

Controlling coexisting attractors of an impacting system via linear augmentation

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.This paper studies the control of coexisting attractors in an impacting system via a recently developed control law based on linear augmentation. Special attention is given to two control issues in the framework of multistable engineering systems, namely, the switching between coexisting attractors without altering the system’s main parameters and the avoidance of grazing-induced chaotic responses. The effectiveness of the proposed control scheme is confirmed numerically for the case of a periodically excited, soft impact oscillator. Our analysis shows how path-following techniques for non-smooth systems can be used in order to determine the optimal control parameters in terms of energy expenditure due to the control signal and transient behavior of the control error, which can be applied to a broad range of engineering problemsThe second author has been supported by the ‘DRESDEN Fellowship Programm’ of the TU Dresden

Dry and wet rainy seasons in the Mantaro river basin (Central Peruvian Andes)

International audienceMonthly precipitation data from the period of 1970 to 2004 from 38 meteorological stations in the Mantaro river basin were used to classify the rainy seasons (September?April) of each year into anomalously dry or wet, and to determine the basin-wide extent of the anomalies based on the Standardized Precipitation Index (SPI). The wet periods mostly occurred in the early 1970's and during the first half of the 1980's, except for the event that occurred in the 1993/94 period which was the strongest and most generalized in the analyzed period. The dry periods occurred mostly during the second half of the 1980's and the 1990's. Consistent with this, a negative trend in precipitation of 2% per decade was found for the rainy season, due mainly to a stronger trend (?4%/decade) during the peak phase (January?March). Despite previously reported significant negative correlations between El Niño-Southern Oscillation (ENSO) and rainfall during the peak of the rainfall season, the similar amplitude variability of precipitation during the onset phase of the rainfall season (September?December), which is uncorrelated with ENSO, participate to the reduction of the absolute correlation for the full rainfall season. Correlations between rainfall in the Mantaro basin and sea surface temperature (SST) in the tropical Atlantic are significant only near the end of the rainy season, with more rain associated with a weaker north-south difference in SST in the tropical Atlantic

Formação de classes equivalentes mediante regras verbais e formato manual

Se analizó la formación de clases de estímulos equivalentes vía reglas verbales mediante la utilización de un procedimiento de igualación de la muestra en un formato de "papel y lápiz" para el entrenamiento y evaluación de discriminaciones condicionales. Participaron voluntariamente 36 estudiantes universitarios; el grupo experimental recibió entrenamiento de línea base vía reglas verbales, pruebas de mantenimiento de línea base y pruebas de equivalencia; el grupo control sólo recibió las pruebas. El instrumento desarrollado mostró ser efectivo. Un número considerable de participantes del grupo experimental logró formar dos clases de estímulos equivalentes, a diferencia del grupo control en que ninguno de los participantes formó las clases. El desarrollo de procedimientos efectivos con "papel y lápiz" y reglas, podría apoyar la enseñanza de habilidades básicas de lectura en poblaciones grandes con economía de tiempo y dinero

Spontaneous Symmetry Breakdown in non-relativistic Quantum Mechanics

The advantages and disadvantages of some pedagogical non-relativistic quantum-mechanical models, used to illustrate spontaneous symmetry breakdown, are discussed. A simple quantum-mechanical toy model (a spinor on the line, subject to a magnetostatic interaction) is presented, that exhibits the spontaneous breakdown of an internal symmetry.Comment: 19 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:1111.1213. Equations (30) and (31) have been corrected. Other minor correction

Influence of serological factors and BMI on the blood pressure/hematocrit association in healthy young men and women.

The association between mean arterial blood pressure (MAP) and hematocrit (Hct) as a surrogate for blood viscosity was investigated in a young (average 20.0±2.3 years), healthy population of 174 men and 442 women. Health status was assessed by clinical examination and serological evaluation. Individuals with severe anemia or hemoconcentration, prior traumas or major surgical intervention, smokers, and pregnant or lactating women were excluded from the study. The MAP/Hct association was positive and significant (P=0.04) for women and negative, albeit not significantly so, for men. The MAP/Hct association was also evaluated in subgroups of the same population with a progressive step-by-step exclusion of: individuals with cholesterol >200 mg/dL; triglycerides >200 mg/dL; body mass index >25 kg/m(2); and glucose >100 mg/dL. This consecutively reduced the strength of the positive MAP/Hct association in women, which became negative - although not significantly so - when all anomalously high factors were excluded. The same trend was found in men. Our study indicates that previously reported positive trends in the relationship between the MAP and Hct in the population are not present in a young, healthy population of men or women that excludes individuals with the confounding factors of above normal serological values and BMI

Torsional stick-slip vibrations and multistability in drill-strings

This is the final version. Available on open access from Elsevier via the DOI in this recordData accessibility: The datasets generated and analysed during the current study are available from the corresponding author on reasonable request.The generalized lumped-parameter model of the drill-string system is studied in this paper to provide a fundamental understanding of the torsional stick-slip vibrations in downhole drilling. Our investigation focuses on analysing the cause of three coexisting states: bit sticking, stick-slip vibration, and constant rotation. A critical region of multistability is identified based on the lumped-parameter model, and the conditions for switching between these multiple stable states are discussed. Special attention is given to the bifurcation structure of the considered drill-string model, which is obtained via path-following methods for nonsmooth dynamical systems. The bifurcation scenario is compared to the case when a longer drill-string is considered, which amounts to drilling deeper. It is found that the main features of the bifurcation picture persist under variation of the drill-string length, with certain numerical differences regarding for instance the window of multistability.Engineering and Physical Sciences Research Council (EPSRC)National Natural Science Foundation of ChinaChina Scholarship Counci

Dynamics of vibro-impact drilling with linear and nonlinear rock models

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordThis paper presents a comprehensive numerical study of a higher order drifting oscillator that has been used to model vibro-impact drilling dynamics in previous publications by our research group [1,2,3,4,5,6,7,8,9]. We focus on the study of the bit-rock interactions, for which both linear and nonlinear models of the drilled medium are considered. Our investigation employed a numerical approach based on direct numerical integration via a newly developed MATLAB-based computational tool, ABESPOL (Chong et al., 2017) [10], and based on path-following methods implemented via a software package for continuation and bifurcation analysis, COCO (Continuation Core) (Dankowicz and Schilder, 2013) [11]. The analysis considered the excitation frequency, amplitude of excitation and the static force as the main control parameters, while the rate of penetration (ROP) was chosen as the main system output so as to assess the performance of the system when linear and nonlinear bit-rock impact models are used. Furthermore, our numerical investigation reveals a rich system dynamics, owing to the presence of codimension-one bifurcations of limit cycles that influence the system behaviour dramatically, as well as multistability phenomenon and chaotic motion.This paper is supported by National Key Basic Research Program of China (973 Program) (Grant No. 2015CB251206), and the National Natural Science Foundation of China （No. 51775038