Online-Computation Approach to Optimal Control of Noise-Affected Nonlinear Systems with Continuous State and Control Spaces

© 2007 EUCA.A novel online-computation approach to optimal control of nonlinear, noise-affected systems with continuous state and control spaces is presented. In the proposed algorithm, system noise is explicitly incorporated into the control decision. This leads to superior results compared to state-of-the-art nonlinear controllers that neglect this influence. The solution of an optimal nonlinear controller for a corresponding deterministic system is employed to find a meaningful state space restriction. This restriction is obtained by means of approximate state prediction using the noisy system equation. Within this constrained state space, an optimal closed-loop solution for a finite decision-making horizon (prediction horizon) is determined within an adaptively restricted optimization space. Interleaving stochastic dynamic programming and value function approximation yields a solution to the considered optimal control problem. The enhanced performance of the proposed discrete-time controller is illustrated by means of a scalar example system. Nonlinear model predictive control is applied to address approximate treatment of infinite-horizon problems by the finite-horizon controller

The Role of the Sibling Relationship During Stressful Life Events

Siblings play a major role in each other’s lives. If a child has a sibling, they experience life together often going through similar struggles, events, or joys. As siblings grow up, they often disclose information to each other and why or how they disclose life events to one another can depend on many factors. The disclosure levels will likely shift as siblings grow older and move through life. The current study focused on levels of disclosure between siblings and how disclosure is related to the gender of the siblings and the degree of warmth and emotional support in their relationships. College students (54 male, 140 female, 7 other) completed questionnaires about the relationship they have with the sibling closest in age to them. Participants were asked some general questions about their sibling relationship as well as with whom they would disclose information in three hypothetical situations. Based on previous studies, I hypothesized that siblings would be more likely to go to each other during stressful family events as compared to stressful personal events, and this hypothesis was supported. I also found, as hypothesized, that siblings with warm and emotionally supportive relationships, and who were closer in age, would be more likely to disclose to one another than other siblings. In terms of gender, I predicted that pairs of sisters would be more likely to disclose to each other than both sister-brother pairs and brother-brother pairs, which was supported. Lastly, I expected that siblings would be more likely to discuss a family-wide event with one another and would be more likely to discuss personal and positive events with a friend, which was also supported by my data. No difference was found in disclosure levels between older and younger siblings (in terms of birth order). Overall, I found that siblings were most likely to rely on one another during a stressful family-wide event and that the presence of warmth and emotional support facilitated the increased disclosure. In the future, it could be helpful to examine how disclosure levels between siblings differ later in life as people start new families or even move towards the end of their lives

Una alpargata en Barracas

A partir de los trabajos de investigación arqueológica en situaciones de rescate, se intervino en la obra de construcción del edificio Ombú, nueva sede de la empresa Metrogas, ubicada en la calle Lamadrid 1360 del barrio de Barracas. En esa localización funcionó el gasómetro que sirvió para el alumbrado barrial desde finales del siglo XIX. A pocos metros, se ubica la Fábrica de Alpargatas desde 1883. Posteriormente a la extracción del elemento de la excavación, se intervino para demostrar la necesidad del trabajo interdisciplinario acorde a la conservación preventiva de hallazgos que incrementan las “colecciones museológicas”. Se puntualizará la intervención sobre una alpargata. Para caracterizarla en detalle se la recuperó y estabilizó devolviéndole la unidad potencial necesaria para dejarla en condiciones óptimas para el almacenaje en la Reserva Técnica o el montaje en una exhibición. Para identificar el objeto se requirió de la selección y clasificación sistemática del material por parte del arqueólogo y del conocimiento del conservador para su individualización y recuperación. Gracias a este trabajo articulado se obtuvo un beneficio pleno del material de excavación optimizándose los resultados y logrando una correcta recuperación del objeto.Tópico 2: Conservación y restauración de pinturas, cueros, textiles y metales

Evidence from satellite altimetry for small-scale convection in the mantle

Small scale convection can be defined as that part of the mantle circulation in which upwellings and downwellings can occur beneath the lithosphere within the interiors of plates, in contrast to the large scale flow associated with plate motions where upwellings and downwellings occur at ridges and trenches. The two scales of convection will interact so that the form of the small scale convection will depend on how it arises within the large scale flow. Observations based on GEOS-3 and SEASAT altimetry suggest that small scale convection occurs in at least two different ways

Synthetic aperture radar (SAR)-based mapping of volcanic flows: Manam Island, Papua New Guinea

International audienceWe present new radar-based techniques for efficient identification of surface changes generated by lava and pyroclastic flows, and apply these to the 1996 eruption of Manam Volcano, Papua New Guinea. Polarimetric L- and P-band airborne synthetic aperture radar (SAR) data, along with a C-band DEM, were acquired over the volcano on 17 November 1996 during a major eruption sequence. The L-band data are analyzed for dominant scattering mechanisms on a per pixel basis using radar target decomposition techniques. A classification method is presented, and when applied to the L-band polarimetry, it readily distinguishes bare surfaces from forest cover over Manam volcano. In particular, the classification scheme identifies a post-1992 lava flow in NE Valley of Manam Island as a mainly bare surface and the underlying 1992 flow units as mainly vegetated surfaces. The Smithsonian's Global Volcanism Network reports allow us to speculate whether the bare surface is a flow dating from October or November in the early part of the late-1996 eruption sequence. This work shows that fully polarimetric SAR is sensitive to scattering mechanism changes caused by volcanic resurfacing processes such as lava and pyroclastic flows. By extension, this technique should also prove useful in mapping debris flows, ash deposits and volcanic landslides associated with major eruptions

La ley de la memoria : Formas y normas de la legalización del Patrimonio Cultural en Entre Ríos, Argentina

Actualmente hablar sobre las prácticas, las relaciones y los bienes muebles e inmuebles que componen el acervo cultural de cada territorio implica inmiscuirse en las corrientes internacionales y nacionales de teorización, patrimonialización y legalización donde lo `cultural´ -y sus referencias materiales e inmateriales- es fundamental para la protección, conservación y reproducción de las memorias e identidades sociales. En el siguiente trabajo realizamos un recorrido por los debates patrimoniales-normativos de la provincia de Entre Ríos, Argentina, contextualizando el campo legal de nuestro país y de la región específica. A lo largo del artículo tensionaremos las principales categorías que emergen con énfasis en las formas de comunicar de los textos legales, sus prescripciones y omisiones. Esperamos así ilustrar el estado de la cuestión de leyes, decretos y normas que rigen al Patrimonio Cultural Material en Entre Ríos visibilizando los matices bajo los cuales subyacen preconcepciones, compromisos y representaciones sociales.Currently speaking about the practices, relationships and movable and immovable goods that make up the cultural heritage of each territory implies submerging in international and national currents of theorization, patrimonialization and legalization where the `cultural´ aspect of life - and its material and immaterial references- is fundamental for the protection, conservation and reproduction of memories and social identities. In the following work we carry out a journey through the patrimonial-normative debates of the province of Entre Ríos, Argentina, contextualizing the legal field of our country and of the specific region. Throughout the article we will stress the main categories that emerge with emphasis on the forms of communication of legal texts, their prescriptions and omissions. We thus hope to illustrate the state of the matter of laws, decrees and regulations that govern the Material Cultural Heritage in Entre Ríos, making visible the nuances under which preconceptions, commitments and social representations underlie.Facultad de Periodismo y Comunicación Socia

Adaptive dynamic resource allocation in annual eusocial insects: Environmental variation will not necessarily promote graded control

Background: According to the classical model of Macevicz and Oster, annual eusocial insects should show a clear dichotomous "bang-bang" strategy of resource allocation; colony fitness is maximised when a period of pure colony growth (exclusive production of workers) is followed by a single reproductive period characterised by the exclusive production of sexuals. However, in several species graded investment strategies with a simultaneous production of workers and sexuals have been observed. Such deviations from the "bang-bang" strategy are usually interpreted as an adaptive (bet-hedging) response to environmental fluctuations such as variation in season length or food availability. To generate predictions about the optimal investment pattern of insect colonies in fluctuating environments, we slightly modified Macevicz and Oster's classical model of annual colony dynamics and used a dynamic programming approach nested into a recurrence procedure for the solution of the stochastic optimal control problem. Results: 1) The optimal switching time between pure colony growth and the exclusive production of sexuals decreases with increasing environmental variance. 2) Yet, for reasonable levels of environmental fluctuations no deviation from the typical bang-bang strategy is predicted. 3) Model calculations for the halictid bee Lasioglossum malachurum reveal that bet-hedging is not likely to be the reason for the graded allocation into sexuals versus workers observed in this species. 4) When environmental variance reaches a critical level our model predicts an abrupt change from dichotomous behaviour to graded allocation strategies, but the transition between colony growth and production of sexuals is not necessarily monotonic. Both, the critical level of environmental variance as well as the characteristic pattern of resource allocation strongly depend on the type of function used to describe environmental fluctuations. Conclusion: Up to now bet-hedging as an evolutionary response to variation in season length has been the main argument to explain field observations of graded resource allocation in annual eusocial insect species. However, our model shows that the effect of moderate fluctuations of environmental conditions does not select for deviation from the classical bang-bang strategy and that the evolution of graded allocation strategies can be triggered only by extreme fluctuations. Detailed quantitative observations on resource allocation in eusocial insects are needed to analyse the relevance of alternative explanations, e.g. logistic colony growth or reproductive conflict between queen and workers, for the evolution of graded allocation strategies

Die politischen Beziehungen zwischen den USA und Großbritannien von 1898 bis 1903

Diese Diplomarbeit handelt von den politischen Beziehungen zwischen den USA und Großbritannien von 1898 bis 1903. Es sind dies Jahre des Wandels in der bilateralen Beziehung beider Länder. 1898 fand der spanisch-amerikanische Krieg statt, der die beiden Länder einander näher brachte und der die Vorteile einer Verbesserung der bilateralen Beziehung zwischen den Vereinigten Staaten und dem Vereinigten Königreich aufzeigte. Die USA stiegen durch dieses Ereignis zur Großmacht auf. Die Briten erkannten vor allem durch den aufwändigen Burenkrieg, dass sie ihre unangefochtene Weltmachtstellung nicht mehr aufrechterhalten konnten. Somit war eine Annäherung an die USA für das Vereinigte Königreich optimal, da es sich politisch und militärisch auf andere, für sie wichtigere, Gebiete als die Amerikas konzentrieren konnte. Den Vereinigten Staaten war es durch diese neue Situation möglich, Vorteile in den noch offenen Konflikten (Isthmuskanal, Grenze zwischen Alaska und Kanada, Venezuela-Affäre) mit den Briten zu nutzen. Mit 1903 sind die genannten und ausführlich in dieser Arbeit dargelegten großen politischen Streitpunkte in der westlichen Hemisphäre zwischen den zwei Nationen aus dem Weg geräumt. Exemplarisch wurde zum besseren Verständnis der angloamerikanischen Beziehung der Briefwechsel Theodore Roosevelts mit zwei mit ihm befreundeten britischen Persönlichkeiten, Sir Cecil Arthur Spring Rice und Viscount Arthur Hamilton Lee, zu diesen Konflikten zur Analyse ausgewählt. Manche sonst schwierig nachvollziehbaren politischen Aktionen Roosevelts sind so leichter verständlich. Vor allem kann man aber aus den Briefen Roosevelts an seine Freunde die Grenzen des Einflusses persönlicher Freundschaften auf internationale politische Entscheidungen gut erkennen