Application of Convex Relaxation to Array Synthesis Problems

International audienceA general procedure to solve efficiently non convex array synthesis problems is presented. It is based on the SemiDefinite Relaxation (SDR) technique. The way to properly relax the constraints in order to formulate the synthesis of shaped beams, phase-only arrays and reconfigurable arrays as semidefinite programming problems is detailed. These so-approximated array synthesis problems are then convex, easy to implement and can be efficiently solved using off-the-shelf numerical routines. The conditions under which the relaxed problems provide the optimal solution to the original non convex synthesis problems are specified. Various representative numerical comparisons with arrays designed by other approaches show the validity of the proposed method and illustrate its potentialities

Polarization Synthesis of Arbitrary Arrays with Shaped Beam Pattern

International audienceThe joint synthesis of the spatial power pattern and polarization of arbitrary arrays is addressed. Specifically, the element excitations are determined such that the array radiates a shaped power pattern while its polarization is optimized in an angular region. Any state of polarization (elliptical, circular and linear) can be synthesized and there is no restriction regarding the array geometry and element patterns. The synthesis problem is rewritten as a convex optimization problem, that is efficiently solved using readily available software. Various numerical results are presented to validate the proposed method and illustrate its potentialities

Array synthesis problems via convex relaxation

International audienceA general procedure, based on the SemiDefinite Re-laxation (SDR) technique, is presented to solve efficiently a wide range of difficult (because non-convex) array synthesis problems. This powerful approximation technique is easy to implement and the so-approximated problem can then be efficiently solved using off-the-shelf numerical routines. Examples of shaped beam and reconfigurable array synthesis are shown to illustrate the potentialities of the proposed approach

Accurate array diagnosis from near-field measurements using ℓ1 reweighted minimization

International audienceIn this contribution the use of ℓ1 weighted minimization for the diagnosis of arrays from a reduced set of near-field data is investigated. Numerical results show that reweighed method gives a higher probability of an accurate estimation of the failures compared to the classic ℓ1 minimization proposed in the past literature

Neural Correlates of Social Behavior in Mushroom Body Extrinsic Neurons of the Honeybee Apis mellifera

The social behavior of honeybees (Apis mellifera) has been extensively investigated, but little is known about its neuronal correlates. We developed a method that allowed us to record extracellularly from mushroom body extrinsic neurons (MB ENs) in a freely moving bee within a small but functioning mini colony of approximately 1,000 bees. This study aimed to correlate the neuronal activity of multimodal high-order MB ENs with social behavior in a close to natural setting. The behavior of all bees in the colony was video recorded. The behavior of the recorded animal was compared with other hive mates and no significant differences were found. Changes in the spike rate appeared before, during or after social interactions. The time window of the strongest effect on spike rate changes ranged from 1 s to 2 s before and after the interaction, depending on the individual animal and recorded neuron. The highest spike rates occurred when the experimental animal was situated close to a hive mate. The variance of the spike rates was analyzed as a proxy for high order multi-unit processing. Comparing randomly selected time windows with those in which the recorded animal performed social interactions showed a significantly increased spike rate variance during social interactions. The experimental set-up employed for this study offers a powerful opportunity to correlate neuronal activity with intrinsically motivated behavior of socially interacting animals. We conclude that the recorded MB ENs are potentially involved in initiating and controlling social interactions in honeybees

Installing, Running and Maintaining Large Linux Clusters at CERN

Having built up Linux clusters to more than 1000 nodes over the past five years, we already have practical experience confronting some of the LHC scale computing challenges: scalability, automation, hardware diversity, security, and rolling OS upgrades. This paper describes the tools and processes we have implemented, working in close collaboration with the EDG project [1], especially with the WP4 subtask, to improve the manageability of our clusters, in particular in the areas of system installation, configuration, and monitoring. In addition to the purely technical issues, providing shared interactive and batch services which can adapt to meet the diverse and changing requirements of our users is a significant challenge. We describe the developments and tuning that we have introduced on our LSF based systems to maximise both responsiveness to users and overall system utilisation. Finally, this paper will describe the problems we are facing in enlarging our heterogeneous Linux clusters, the progress we have made in dealing with the current issues and the steps we are taking to gridify the clustersComment: 5 pages, Proceedings for the CHEP 2003 conference, La Jolla, California, March 24 - 28, 200

Essays on tackling economic inequalities

This thesis provides a differentiated picture of two interventions and one policy reform to alleviate economic inequality. In two chapters this dissertation examines whether out-of-school activities affect behavioral outcomes reflecting character, social and executive function skills. The first essay in this thesis analyzes the effect of performing sports on a regular basis on the formation of character and social skills. The findings confirm that sports is generally a social activity. For youths from less advantaged family backgrounds sports constitutes often the only quality pastime they engage in. Athletic involvement has beneficial effects on a broad range of character skills. These effects are largely driven by youths who do not engage in any other structured activity. Further, the effects can be interpreted as a broader effect of having access to an enriched social environment. The second essay examines the effect of working part-time while attending full-time schooling on the development of character skills and occupational choice strategies. Comparing adolescents who hold a job with adolescents who do not work, the former spend less time in front of a screen and invest more time in academic learning. Focusing on the time use of employed adolescents, working part-time has an ambivalent effect on time invested in other activities. It reduces their homework time as well as their nonproductive screen time. The results imply that holding a paid job while still in school reduces the uncertainty about own interests and talents and reduces the dependency on parents. A third essay evaluates the impact of the Tenancy Law Reform Act in 2001, a policy which targets to protect especially low-income households against rent increase. Germany is one of the European countries with the highest percentage of the population who lives in tenancies. This illustrates the importance of a functioning tenancy law, socially and economically. This essay analyzes the effect of the reform on the level of rents as well as on the residency discount. The two substantial parts of the reform were the reduction of the maximum rent increases for sitting tenants and the reduction of the minimum notice period until termination of a tenancy by the tenant. Estimating the effect over the distribution of rents, the reform shows a significant negative effect on rents that is stronger at higher quantiles. The annual residency discount increases with the reform during the first three years of a tenancy and vanishes thereafter. The evidence suggests that the reform was successful in curtailing rent increases especially for expensive apartments early in a tenancy. This thesis provides a differentiated picture on how economic inequalities can be alleviated. On the one side, this thesis focuses on the formation of character skills which are helpful for bringing especially unskilled people into employment and to better paid jobs. On the other side, this thesis focuses on a tenancy law reform that targeted to protect tenants against rent increases. While beneficial effects of structured leisure activities on the formation of character skills can be detected, one may be concerned that the tenancy law reform may not have been sufficiently targeted if considering the target of the reform to protect especially low-income households against rent increases.Diese Dissertation liefert ein differenziertes Bild zu zwei Interventionen und einer Politikreform um die ökonomische Ungleichheit zu mildern. In zwei Aufsätzen wird dabei auf die Rolle von außerschulischen Aktivitäten bei der Bildung von charakterlichen und sozialen Fähigkeiten eingegangen. Der erste Aufsatz in dieser Dissertation betrachtet den Einfluss einer regelmäßigen Ausübung von Sport auf die Entwicklung von charakterlichen und sozialen Fähigkeiten. Die Ergebnisse zeigen, dass Sport generell eine soziale Aktivität ist. Für Jugendliche aus sozial benachteiligten Schichten stellt Sport meistens die einzige qualitativ wertvolle Freizeitbeschäftigung dar. Sport hat einen förderlichen Einfluss auf ein breites Spektrum an Kompetenzen. Dieser Einfluss wird insbesondere durch Jugendliche, die keine anderen strukturierten Freizeitaktivitäten ausüben, getrieben. Zudem kann der Effekt von Sport als einen umfassenderen Einfluss des Zugangs zu einer bereichernden sozialen Umgebung interpretiert werden. Der zweite Aufsatz untersucht den Einfluss der Ausübung von Nebenjobs als Schüler auf die Entwicklung der Persönlichkeit und von Einstellungen und Strategien zur eigenen Berufswahl. Die Ergebnisse zeigen, dass Schüler, die neben der schulischen Ausbildung eine beruflichen Tätigkeit nachgehen, mehr Zeit in schulisches Lernen investieren und weniger Zeit vor einem Bildschirm verbringen. Jedoch verringert sich die Zeit die mit Hausaufgaben verbracht wird wie auch die nichtproduktive Zeit vor einem Bildschirm, wenn neben der Schule noch gejobbt wird. Insgesamt hat ein Nebenjob förderliche Effekte auf die eigene Unabhängigkeit gegenüber den Eltern und verringert die Unsicherheit über eigene Interessen und Fähigkeiten. Der dritte Aufsatz der Dissertation evaluiert den Einfluss der Mietrechtsreform in Deutschland im Jahr 2001. Diese Reform beabsichtigt u.a. geringverdienende Haushalte vor Mietanstiegen zu schützen. Im Vergleich zu anderen europäischen Staaten weist Deutschland den höchsten Anteilssatz an der Bevölkerung auf, die in Mietverhältnissen leben. Ein funktionierendes Mietgesetz ist somit aus sozialer und ökonomischer Sicht wichtig. Die Reform umfasst u.a. die Reduzierung der möglichen Mieterhöhungen seitens des Vermieters sowie eine Verkürzung der Kündigungsfrist seitens des Mieters. Die Ergebnisse zeigen, dass die Reform für die ersten Jahre eines Mietverhältnisses einen negativen Effekt auf die Miethöhe hat, der jedoch mit ansteigender Dauer des Mietverhältnisses verschwindet. Zudem finden sich stärkere Effekte bei hochpreisigen Mietwohnungen. Diese Dissertation liefert ein differenziertes Bild, wie die ökonomische Ungleichheit gemildert werden kann. Auf der einen Seite beschäftigt sich die Dissertation mit der Bildung von nichtkognitiven Kompetenzen, die hilfreich sind um insbesondere Geringqualifizierte in Beschäftigung und zu besser bezahlten Jobs zu bringen. Auf der anderen Seite wird der Effekt einer Mietrechtsreform evaluiert. Während ein förderlicher Effekt von strukturierten Aktivitäten auf die Bildung von charakterlichen Fähigkeiten festgestellt werden kann, zeigt sich bei der Evaluierung der Mietrechtsreform, dass geringverdienende Haushalte nicht im gleichen oder höheren Umfang von der Reform profitieren als finanziell besser gestellte Haushalte

The effect of teenage employment on character skills, expectationsand occupational choice strategies

A growing body of research suggests that, even after controlling for cognitive abilities, personality predicts economic success in later life. The learning environment at school focuses on knowledge and cognitive skills. The transmission of character skills, however, is not at the center of attention. Leisure activities as informal learning activities outside of school may affect the formation of skills. By providing valuable opportunities, working part-time while attending full-time secondary schooling can be seen as a stepping stone toward independence and adulthood. The channel of the positive influence, however has not been identified empirically. I suggest that employment during adolescence promotes the formation of character skills that are known to have a positive effect on labor market outcomes and educational achievement. Employing a exible strategy combining propensity score matching and regression techniques to account for self-selection, I find beneficial e ects on character skills. Further, it improves future expectations, the knowledge on which skills and talents school students have and reduces the importance of parents advice with respect to their childs future career. The results are robust to several model specifications and varying samples and robust to including family-fixed effects

Responses to larval herbivory in the phenylpropanoid pathway of Ulmus minor are boosted by prior insect egg deposition

Main conclusion Elms, which have received insect eggs as a ‘warning’ of larval herbivory, enhance their anti-herbivore defences by accumulating salicylic acid and amplifying phenylpropanoid-related transcriptional and metabolic responses to hatching larvae. Abstract Plant responses to insect eggs can result in intensified defences against hatching larvae. In annual plants, this egg-mediated effect is known to be associated with changes in leaf phenylpropanoid levels. However, little is known about how trees—long-living, perennial plants—improve their egg-mediated, anti-herbivore defences. The role of phytohormones and the phenylpropanoid pathway in egg-primed anti-herbivore defences of a tree species has until now been left unexplored. Using targeted and untargeted metabolome analyses we studied how the phenylpropanoid pathway of Ulmus minor responds to egg-laying by the elm leaf beetle and subsequent larval feeding. We found that when compared to untreated leaves, kaempferol and quercetin concentrations increased in feeding-damaged leaves with prior egg deposition, but not in feeding-damaged leaves without eggs. PCR analyses revealed that prior insect egg deposition intensified feeding-induced expression of phenylalanine ammonia lyase (PAL), encoding the gateway enzyme of the phenylpropanoid pathway. Salicylic acid (SA) concentrations were higher in egg-treated, feeding-damaged leaves than in egg-free, feeding-damaged leaves, but SA levels did not increase in response to egg deposition alone—in contrast to observations made of Arabidopsis thaliana. Our results indicate that prior egg deposition induces a SA-mediated response in elms to feeding damage. Furthermore, egg deposition boosts phenylpropanoid biosynthesis in subsequently feeding-damaged leaves by enhanced PAL expression, which results in the accumulation of phenylpropanoid derivatives. As such, the elm tree shows similar, yet distinct, responses to insect eggs and larval feeding as the annual model plant A. thaliana