Piecewise smooth systems near a co-dimension 2 discontinuity manifold: can one say what should happen?

We consider a piecewise smooth system in the neighborhood of a co-dimension 2 discontinuity manifold $\Sigma$. Within the class of Filippov solutions, if $\Sigma$ is attractive, one should expect solution trajectories to slide on $\Sigma$. It is well known, however, that the classical Filippov convexification methodology is ambiguous on $\Sigma$. The situation is further complicated by the possibility that, regardless of how sliding on $\Sigma$ is taking place, during sliding motion a trajectory encounters so-called generic first order exit points, where $\Sigma$ ceases to be attractive. In this work, we attempt to understand what behavior one should expect of a solution trajectory near $\Sigma$ when $\Sigma$ is attractive, what to expect when $\Sigma$ ceases to be attractive (at least, at generic exit points), and finally we also contrast and compare the behavior of some regularizations proposed in the literature. Through analysis and experiments we will confirm some known facts, and provide some important insight: (i) when $\Sigma$ is attractive, a solution trajectory indeed does remain near $\Sigma$, viz. sliding on $\Sigma$ is an appropriate idealization (of course, in general, one cannot predict which sliding vector field should be selected); (ii) when $\Sigma$ loses attractivity (at first order exit conditions), a typical solution trajectory leaves a neighborhood of $\Sigma$; (iii) there is no obvious way to regularize the system so that the regularized trajectory will remain near $\Sigma$ as long as $\Sigma$ is attractive, and so that it will be leaving (a neighborhood of) $\Sigma$ when $\Sigma$ looses attractivity. We reach the above conclusions by considering exclusively the given piecewise smooth system, without superimposing any assumption on what kind of dynamics near $\Sigma$ (or sliding motion on $\Sigma$) should have been taking place.Comment: 19 figure

Study of radiation effects on bipolar transistors

Abstract In this paper it was shown that the irradiation with neutrons and carbon ions leads to gain degradation in bipolar transistors due to generation of defects. The density of these generated defects is independent of the type of irradiation (neutrons or carbon ions). Thus, it is possible to evaluate Δ(1/β), once the expected Frenkel pair density is known. The dependence of the damage constant on collector current is a power law function, with the exception of the lateral pnp transistors, that shows a higher sensitivity to radiation and a different behaviour. Neutrons give a smaller density of Frenkel pairs (CF) than the two sorts of carbon ions of high energy (CHE) and medium energy (CME). It was found that CME causes a higher concentration of CF. The calculated ratio R=CF/Φ, where CF is the Frenkel pair density and Φ fluence does not depend on Φ, for a given type of radiation. However, it depends on the incoming particle type. Its smallest calculated value was obtained for neutrons (R=6.1×10), which increases to 1.25×103 for CHE and to 1.1×104 for CME

Delivering health knowledge and wisdom from the hills and hollows of Appalachia

There is knowledge in the pages of Appalachia’s hills. This journal is positioned to find and publish those translations. It grows from a need to provide an outlet for scholarship about Appalachia’s health so that knowledge, and occasionally wisdom, is shared with those who care about and are committed to improving the region’s health

Specimen-exchange device for an ultra-high vacuum atom-probe field-ion microscope

A specimen-exchange device is described for an ultra-high vacuum field-ion microscope (FIM). This device completely eliminates the long pump-down period that is required if the FIM chamber is brought back to atmospheric pressure. The pressure in an air-lock is reduced to 10/sup -6/ Torr before the exchange takes place and the pressure in the FIM chamber remains below 10/sup -7/ Torr during the exchange and it drops to less than 3 x 10/sup -9/ Torr within 15 minutes after the exchange

Reviewer Acknowledgments for 2019

The Editorial Team extends a heart-felt “thank you” to those who have given their time and expertise in the past year to participate in this process with the Journal of Appalachian Health. We know that you have many competing pressures on your time, and that you are not financially compensated for the time you spend reviewing manuscripts. We hope that there are other forms of compensation that make the sacrifice worth the effort

How should we measure psychological resilience in sport performers?

Psychological resilience is important in sport because athletes must constantly withstand a wide range of pressures to attain and sustain high performance. To advance psychologists’ understanding of this area, there exists an urgent need to develop a sport-specific measure of resilience. The purpose of this paper is to review psychometric issues in resilience research and to discuss the implications for sport psychology. Drawing on the wider general psychology literature to inform the discussion, the narrative is divided into three main sections relating to resilience and its assessment: adversity, positive adaptation, and protective factors. The first section reviews the different ways that adversity has been measured and considers the potential problems of using items with varying degrees of controllability and risk. The second section discusses the different approaches to assessing positive adaptation and examines the issue of circularity pervasive in resilience research. The final section explores the various issues related to the assessment of protective factors drawing directly from current measures of resilience in other psychology sub-disciplines. The commentary concludes with key recommendations for sport psychology researchers seeking to develop a measure of psychological resilience in athletes

A measure of individual role in collective dynamics

Identifying key players in collective dynamics remains a challenge in several research fields, from the efficient dissemination of ideas to drug target discovery in biomedical problems. The difficulty lies at several levels: how to single out the role of individual elements in such intermingled systems, or which is the best way to quantify their importance. Centrality measures describe a node's importance by its position in a network. The key issue obviated is that the contribution of a node to the collective behavior is not uniquely determined by the structure of the system but it is a result of the interplay between dynamics and network structure. We show that dynamical influence measures explicitly how strongly a node's dynamical state affects collective behavior. For critical spreading, dynamical influence targets nodes according to their spreading capabilities. For diffusive processes it quantifies how efficiently real systems may be controlled by manipulating a single node.Comment: accepted for publication in Scientific Report