6,974 research outputs found

    Testing approaches for global optimization of space trajectories

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    In this paper the procedures to test global search algorithms applied to space trajectory design problems are discussed. Furthermore, a number of performance indexes that can be used to evaluate the effectiveness of the tested algorithms are presented. The performance indexes are then compared and the actual significance of each one of them is highlighted. Three global optimization algorithms are tested on three typical space trajectory design problems

    Nanometers-thick self-organized Fe stripes: bridging the gap between surfaces and magnetic materials

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    We have fabricated 5nm-high Fe(110) stripes by self-organized (SO) growth on a slightly vicinal R(110)/Al2O3(11-20) surface, with R=Mo, W. Remanence, coercivity and domain patterns were observed at room temperature (RT). This contrasts with conventional SO epitaxial systems, that are superparamagnetic or even non-magnetic at RT due to their flatness. Our process should help to overcome superparamagnetism without compromise on the lateral size if SO systems are ever to be used in applications

    Sistemas Agroflorestais em Rondônia: uma alternativa de produção agrícola.

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    Publicação com orientações sobre a utilização de sistemas agroflorestais como alternativa de produção; destinada ao pequeno produtor, orienta-o sobre os ganhos econômicos, sem que haja necessidade de aguardar longos períodos de tempo para extração da madeira, através da combinação que envolve culturas temporárias de ciclo curto, ciclo médio, fruteiras perenes e espécies florestais madeireiras.bitstream/item/42733/1/sistemas-FD-20000001.pd

    No preference in female sika deer for conspecific over heterospecific male sexual calls in a mate choice context

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    Mating signals can be used both in contexts of species recognition and mate quality assessment. This study examines species recognition abilities in oestrous females presented with male mating calls from both conspecifics and closely related allopatric heterospecifics. Red deer and sika deer are naturally allopatric polygynous species capable of hybridization during sympatry. Male mating calls are sexually selected and differ greatly between species. Previous work indicated that most but not all oestrous red deer hinds prefer male mating calls from conspecifics over heterospecific sika deer. Using two-speaker playback experiments, we extend this examination by measuring the preference responses of oestrous sika deer hinds to these stimuli. We predicted that oestrous sika deer hinds will show little flexibility in behavioural responses and prefer conspecific calls over heterospecific calls, similar to those of red deer hinds. In contrast, sika deer hinds showed high levels of flexibility and no difference in overall preference behaviours, suggesting that vocal behaviour does not provide a solid barrier to hybridization in this species. The asymmetry in heterospecific preference responses between these species is discussed in relation to possible causation and hybridization patterns observed in free-ranging populations

    (Global) Optimization: Historical notes and recent developments

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    Recent developments in (Global) Optimization are surveyed in this paper. We collected and commented quite a large number of recent references which, in our opinion, well represent the vivacity, deepness, and width of scope of current computational approaches and theoretical results about nonconvex optimization problems. Before the presentation of the recent developments, which are subdivided into two parts related to heuristic and exact approaches, respectively, we briefly sketch the origin of the discipline and observe what, from the initial attempts, survived, what was not considered at all as well as a few approaches which have been recently rediscovered, mostly in connection with machine learning

    Estudo preliminar de sistemas agroflorestais no Distrito de Triunfo, Candeias do Jamari, Rondônia.

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    O presente estudo teve por objetivo conhecer/analisar experiências em sistemas agroflorestais no Distrito de Triunfo, Município de Candeias do Jamari, Rondônia, identificando os tipos de sistemas implantados, as perspectivas dos produtores quanto aos SAF, bem como evidenciar dados para estimular outros produtores a aderirem à prática de sistemas agroflorestais

    Do red deer hinds prefer stags that produce harsh roars in mate choice contexts?

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    Red deer stags give two types of roars during the breeding season, termed ‘common’ and ‘harsh’ roars. This study tested the hypothesis that the characteristic spectro-temporal structure of male harsh roars functions to directly attract females towards male callers during the breeding season. The results show that oestrous hinds look for longer towards speakers broadcasting sequences containing harsh roars, but do not preferentially approach or spend more time in close proximity to speakers broadcasting harsh roars over those broadcasting only common roars. While these observations confirm that the specific acoustic structure of male harsh roars functions to draw the attention of hinds, they are not consistent with the notion that these calls have an immediate impact on mate choice decisions by stimulating oestrous hinds to move towards male callers. Consequently, we suggest that intersexual selection through female mate choice is unlikely to be a major factor driving the evolution of male red deer harsh roars
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