1,226 research outputs found

    On the size of quadtrees generalized to d-dimensional binary pictures

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    AbstractSome results about the size of quadtrees and linear quadtrees, used to represent binary 2n × 2n digital pictures, are generalized to d-dimensional 2n × … × 2n pictures. Among these results are a comparison of the space-efficiency of linear vs regular trees, in terms of both the number of nodes of the tree and the number of bits needed to store each node, and an upper bound on the number of nodes as a function of n and the perimeter of the picture

    The birds of Perth\u27s urban parks : Factors influencing their distribution and community attitudes towards them

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    Knowledge of the general responses of bird populations to urbanisation and an understanding of their habitat requirements is necessary to ensure the continuation of bird life in urban areas. Most of the literature on urban birds around the world has concentrated on birds in streets and remnant patches. Urban parks provide much potential habitat for birds, although there are few publications addressing this issue. The aims of this project were to determine the terrestrial avifauna of Perth\u27s northern suburban parks, investigate physical factors that might influence the distribution of birds, and determine the attitudes of park users towards birds in suburban parks. Sixteen suburban recreational parks, ranging from 2.5 - 10 ha, were sampled for birds in the northern suburbs of the Perth metropolitan region. Twenty-six terrestrial bird species (including five introduced species) were recorded. This is only a small sample of the potential pool of species available and may be attributed to the isolation and relatively small size of all of Perth\u27s northern suburban parks. The feeding and foraging guilds of the birds of Perth\u27s parks were different to those documented in other urban studies around the world, which is a reflection of high proportion of native vegetation retained in Perth\u27s suburbs. Tree canopy height was the most influential factor on the birds of urban parks. Birds were also surveyed in streets adjacent to the park sites. The results revealed that urban birds use the individual components of the urban matrix differently. All facets of the urban matrix should be investigated in future studies which aim to determine the effects of urbanisation on birds. No park users mentioned watching birds as a reason to visit Perth\u27s suburban parks. The Galah, Kookaburra and Rainbow Lorikeet were identified by Perth\u27s park users as the most desirable urban bird species; the Raven and Magpie were considered the least desirable species. Bird song/call was identified as the most desirable bird characteristic and aggression the least desirable bird characteristic. Ninety-seven percent of park users thought that birds should be encouraged to inhabit suburban areas. The results suggest that while birds are not considered an important reason for visiting parks, most birds are liked by park users and there is a general consensus that birds should be encouraged in suburban areas. Methods to encourage birds into suburban areas include establishing habitat corridors between isolated parks and remnant bushlands, ensuring a diverse, native vegetation of differing strata levels, controlling cats and dogs, reducing lawn cover, retaining some large, old trees with suitable nesting holes and, narrowing the gap between the public\u27s interest and their knowledge regarding birds

    High Resolution Maps of the Vasculature of An Entire Organ

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    The structure of vascular networks represents a great, unsolved problem in anatomy. Network geometry and topology differ dramatically from left to right and person to person as evidenced by the superficial venation of the hands and the vasculature of the retinae. Mathematically, we may state that there is no conserved topology in vascular networks. Efficiency demands that these networks be regular on a statistical level and perhaps optimal. We have taken the first steps towards elucidating the principles underlying vascular organization, creating the rst map of the hierarchical vasculature (above the capillaries) of an entire organ. Using serial blockface microscopy and fluorescence imaging, we are able to identify vasculature at 5 ÎĽm resolution. We have designed image analysis software to segment, align, and skeletonize the resulting data, yielding a map of the individual vessels. We transformed these data into a mathematical graph, allowing computationally efficient storage and the calculation of geometric and topological statistics for the network. Our data revealed a complexity of structure unexpected by theory. We observe loops at all scales that complicate the assignment of hierarchy within the network and the existence of set length scales, implying a distinctly non-fractal structure of components within

    Multi Criteria Mapping Based on SVM and Clustering Methods

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    There are many more ways to automate the application process like using some commercial software’s that are used in big organizations to scan bills and forms, but this application is only for the static frames or formats. In our application, we are trying to automate the non-static frames as the study certificate we get are from different counties with different universities. Each and every university have there one format of certificates, so we try developing a very new application that can commonly work for all the frames or formats. As we observe many applicants are from same university which have a common format of the certificate, if we implement this type of tools, then we can analyze this sort of certificates in a simple way within very less time. To make this process more accurate we try implementing SVM and Clustering methods. With these methods we can accurately map courses in certificates to ASE study path if not to exclude list. A grade calculation is done for courses which are mapped to an ASE list by separating the data for both labs and courses in it. At the end, we try to award some points, which includes points from ASE related courses, work experience, specialization certificates and German language skills. Finally, these points are provided to the chair to select the applicant for master course ASE

    Shape Representations Using Nested Descriptors

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    The problem of shape representation is a core problem in computer vision. It can be argued that shape representation is the most central representational problem for computer vision, since unlike texture or color, shape alone can be used for perceptual tasks such as image matching, object detection and object categorization. This dissertation introduces a new shape representation called the nested descriptor. A nested descriptor represents shape both globally and locally by pooling salient scaled and oriented complex gradients in a large nested support set. We show that this nesting property introduces a nested correlation structure that enables a new local distance function called the nesting distance, which provides a provably robust similarity function for image matching. Furthermore, the nesting property suggests an elegant flower like normalization strategy called a log-spiral difference. We show that this normalization enables a compact binary representation and is equivalent to a form a bottom up saliency. This suggests that the nested descriptor representational power is due to representing salient edges, which makes a fundamental connection between the saliency and local feature descriptor literature. In this dissertation, we introduce three examples of shape representation using nested descriptors: nested shape descriptors for imagery, nested motion descriptors for video and nested pooling for activities. We show evaluation results for these representations that demonstrate state-of-the-art performance for image matching, wide baseline stereo and activity recognition tasks

    The effect of diversified crop rotations with faba beans (Vicia faba L.) on pollinators and pollination services

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    Agricultural intensification and the loss of suitable habitats are drivers of insect declines. Besides the promotion of semi-natural habitats (SNH), the utilization of diversified crop rotations including flowering crops is an option to sustain pollinators. As flowering and nitrogen fixing crops, grain legumes provide several environmental benefits but are underrepresented in the EU. Since 2013 they are promoted within the greening reform of the Common Agricultural Policy (CAP). On-field biodiversity measures are often criticized, though their possible benefits for biodiversity are widely unknown. My PhD thesis aims at investigating the landscape-scale effect of conventional faba bean (Vicia faba L.) cultivation on wild bee communities, their resource utilization and their pollination services. Experiments were conducted in 1km x 1km study landscapes in Germany. For the first three chapters a paired study design was applied with one landscape of a pair comprising at least one faba bean field and the respective control landscape without grain legumes. In the first chapter we studied effects of faba bean cultivation on functional groups of wild bees. We conducted pollinator surveys at field margins of different crops in 30 study landscapes. Bumblebee densities were more than twice as high in faba bean compared to control landscapes, while non-Bombus wild bees were only driven by the amount of SNH. These results indicate that a combination of on- and off-field greening measures is necessary to conserve farmland biodiversity and we recommend that the CAP should furthermore promote both. In the second chapter we investigated the effect of two mass-flowering crops (MFC) on the functional trait composition of bee communities in SNH. Faba bean cultivation promoted bumblebees, especially long-tongued species, social bees and bees foraging on Fabaceae. High oilseed rape (OSR) covers changed wild bee community composition in favor for solitary bees. Local flower cover of SNH was the main driver of non-Bombus wild bees and wild bee species richness. Thus, different MFC promote specific functional bee groups adapted to the crop`s flower morphology. Concluding, the cultivation of functionally diverse crops, combined with a high local flower cover of SNH needs to be targeted by management practices to sustain diverse pollinator communities. In the third chapter we studied landscape and faba bean cultivation effects on the colony development and resource utilization of bumblebees (Bombus terrestris L.). The colonies` reproductive success was not influenced by landscape composition but enhanced by landscape diversity. Faba bean cultivation and pollen diversity interacted and resulted in more young queens with increasing pollen diversity in landscapes without faba bean. In addition, colonies that collected a higher pollen diversity had a reduced A. sociella depredation. Increased parasitism had a cascading negative effect on the reproductive success of bumblebees by limiting colony growth. Our study shows that high landscape diversity and diverse pollen diets can enhance the reproductive success of bumblebees. A diverse diet even mitigated depredation by wax moths. To sustain vital bumblebee populations and their pollination services, diverse and floral rich habitat types should be conserved or restored in agricultural landscapes. In the fourth chapter we investigated, how bee densities in OSR fields are affected by past and current MFC cultivation and how insect pollination affects OSR yield components. Bee densities were positively affected by past MFC covers and negatively affected by current OSR covers. Pollinator exclusion decreased seed number per pod and increased seed weight. Insect pollination interacted with the plants` pod number in shaping yields, while compensating for low pod numbers. In the fifth chapter we analyzed the effect of landscape composition on the densities of different functional bee groups and their foraging behavior in faba bean fields in 11 different landscapes. Moreover, the effect of insect pollination and of landscape composition was tested on faba bean yield components. Landscape composition affected the bees` foraging behavior in the crop. Increasing covers of faba bean and of semi-natural habitats in a landscape had a positive effect on bee densities and on faba bean yield, while oilseed rape cover had a negative effect. Our study emphasizes the importance of considering landscape management in order to maximize flowering crop yields. In conclusion, Vicia faba cultivation is an effective measure to promote wild bees, which are needed for high crop yields. Though, since benefits for pollinator groups depend on the crops` flower morphology, functional trait composition of wild bee communities can be changed in landscapes with a dominating mass-flowering crop species. Thus, landscape and local farm management should aim at increasing farmland plant diversity. The combination of a high cover and quality of semi-natural habitats as well as of diversified farming practices targeting a high spatial and temporal crop diversity is essential to conserve diverse pollinator communities and to sustain high crop yields.2021-12-0

    Cooperative breeding and delayed dispersal in the Pale chanting goshawk, Melierax canorus

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    Bibliography: pages 251-265.A population of Pale Chanting Goshawks Melierax canorus, some of which live in families, was studied during 1988-1992 for a total of 117 group-years near Calitzdorp, South Africa. The aims of the study were to identify ecological and social factors that might predispose individuals in the population to delay dispersal and become non-breeding or co-breeding members of Pale Chanting Goshawk families, and to determine why cobreeders breed cooperatively in polyandrous trios. In all vegetation types within the study area, non-breeders, as juvenile and adult offspring, delayed dispersal from their natal territories. However, co-breeding males occurred only in one vegetation type, Karroid Broken Veld. Co-breeding males participated in all reproductive activities, including copulation. Karroid Broken Veld also supported the largest known groups of Pale Chanting Goshawks and the highest frequency of groups with non-breeders, which resulted in some of the highest recorded single species raptor densities in the Afrotropics. Pale Chanting Goshawks in Karroid Broken Veld preyed primarily on two otomyinid rodents, Otomys unisulcatus (42-48 % of prey biomass) and Parotomys brantsii (18-32 % ). The habitat quality of Karroid Broken Veld for Pale Chanting Goshawks was high since, compared with other vegetation types, it incorporated: (1) optimal habitat for otomyinid prey, (2) a very high estimated biomass of otomyinids, almost twice that of other vegetation types, and (3) a hunting habitat with an optimum combination of prey visibility and perch availability that facilitated hunting efficiency. Territorial space was limited throughout the study area, constraining the number of nonbreeders per group to two and inhibiting new breeders from establishing territories. Juvenile non-breeders probably delayed dispersal to increase their probability of survival, and dispersed later as sexually mature adults, since they could not increase their fitness further by becoming helpers at the nest. During the nestling period, co-breeding beta males provided prey at an equal rate to dominant males, that enabled polyandrous trios to undertake more frequent and successful breeding attempts in years of high prey abundance. The help provided by co-breeders contributed more to this success than did density of dominant prey and territory size. In Karroid Broken Veld co-breeders delayed dispersal since their fitness as subordinate sibling males was probably higher than fitness achieved due from dispersing to a breeding vacancy in habitat of lower quality. I suggest that those ecological factors which contribute to habitat quality provided the proximate impetus, and the resulting saturation of the habitat the ultimate impetus, in promoting the establishment of Pale Chanting Goshawk family units. Once Pale Chanting Goshawk formed families, a range of secondary benefits evolved as birds adjusted their behaviour to benefit from the presence of other group members. For example, although breeders in high-quality habitat produced the highest number of offspring, the lack of territorial space probably forced more offspring to disperse. To increase offspring survival, breeders may have adjusted their reproductive strategy and allow non-breeders to partake and share in returns of cooperative hunts. Other secondary benefits included the possibility of inheriting a natal territory, budding-off onto territorial borders or helping close relatives as an experienced co-breeder
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