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Polygons
Kinds of Polygons Terms modified by Polygons Selected AbstractsBarycentric Coordinates on SurfacesCOMPUTER GRAPHICS FORUM, Issue 5 2010Raif M. Rustamov This paper introduces a method for defining and efficiently computing barycentric coordinates with respect to polygons on general surfaces. Our construction is geared towards injective polygons (polygons that can be enclosed in a metric ball of an appropriate size) and is based on replacing the linear precision property of planar coordinates by a requirement in terms of center of mass, and generalizing this requirement to the surface setting. We show that the resulting surface barycentric coordinates can be computed using planar barycentric coordinates with respect to a polygon in the tangent plane. We prove theoretically that the surface coordinates properly generalize the planar coordinates and carry some of their useful properties such as unique reconstruction of a point given its coordinates, uniqueness for triangles, edge linearity, similarity invariance, and smoothness; in addition, these coordinates are insensitive to isometric deformations and can be used to reconstruct isometries. We show empirically that surface coordinates are shape-aware with consistent gross behavior across different surfaces, are well-behaved for different polygon types/locations on variety of surface forms, and that they are fast to compute. Finally, we demonstrate effectiveness of surface coordinates for interpolation, decal mapping, and correspondence refinement. [source] Moving Least Squares CoordinatesCOMPUTER GRAPHICS FORUM, Issue 5 2010Josiah Manson Abstract We propose a new family of barycentric coordinates that have closed-forms for arbitrary 2D polygons. These coordinates are easy to compute and have linear precision even for open polygons. Not only do these coordinates have linear precision, but we can create coordinates that reproduce polynomials of a set degree m as long as degree m polynomials are specified along the boundary of the polygon. We also show how to extend these coordinates to interpolate derivatives specified on the boundary. [source] Effect of caffeine on prospective and retrospective duration judgementsHUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 5 2003Ronald P. Gruber Abstract The effects of caffeine on prospective and retrospective duration judgements were evaluated in a double-blind placebo-controlled experiment. After taking either 200,mg caffeine or a placebo, participants touched a 17-sided polygon for 15,s. Then they verbally estimated the number of angles and the duration. Participants in the prospective group were told in advance they would be making a duration estimate, whereas those in the retrospective group were not told. Caffeine reduced duration estimates in the prospective condition but not in the retrospective condition. The effect of caffeine on very long duration comparisons (the past year compared with a year at one-half and one-quarter of one's age) was also evaluated, but none was found. The findings do not support the hypothesis that caffeine affects duration experience by increasing the internal clock rate as a result of its dopamine D2 agonist properties. The hypothesis that caffeine produces its effect by enhancing memory was considered and rejected. The most parsimonious explanation is that caffeine increased arousal level, which led to a narrowing of the focus of attention to the most salient task. Copyright © 2003 John Wiley & Sons, Ltd. [source] Experimental evidence that deer browsing reduces habitat suitability for breeding Common Nightingales Luscinia megarhynchosIBIS, Issue 2 2010CHAS A. HOLT The ecological impacts of increasing populations of deer (Cervidae) in Europe and North America are becoming more widespread and pronounced. Within Britain, it has been suggested that declines in several woodland bird species, particularly those dependent on dense understorey vegetation, may be at least partly due to these effects. Here we present experimental evidence of the effects of deer browsing on the fine-scale habitat selection and habitat use by a bird species in Europe. The study was conducted in a wood in eastern England where a decrease in Common Nightingale Luscinia megarhynchos numbers has coincided with a large increase in deer numbers. Eight woodland plots were cut to produce young coppice regrowth (a favoured habitat for Nightingales). Deer were excluded from half of each plot using steel fences, thus creating eight experimental pairs of exclosures (unbrowsed) and controls (browsed). Radiotelemetry and territory mapping of male Nightingales showed strong selection of exclosures. The density of territories was 15 times greater in the exclosures than in grazed controls. Selection for exclosures was significant for the minimum convex polygon, 95% kernel and 50% core home-ranges used by seven radiotracked males. Tracked birds spent 69% of their time in the 6% of the study area protected from deer. Intensified browsing by deer influenced local settlement patterns of Nightingales, supporting the conclusion that increased deer populations are likely to have contributed to declines of Nightingales in Britain, and potentially those of other bird species dependent on dense understorey. [source] Multi-linearity algorithm for wall slip in two-dimensional gap flowINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2007G. J. Ma Abstract Wall slip has been observed in a micro/nanometer gap during the past few years. It is difficult to make a mathematical analysis for the hydrodynamics of the fluid flowing in a gap with wall slip because the fluid velocity at the liquid,solid interface is not known a priori. This difficulty is met especially in a two-dimensional slip flow due to the non-linearity of the slip control equation. In the present paper we developed a multi-linearity method to approach the non-linear control equation of the two-dimensional slip gap flow. We used an amended polygon to approximate the circle yield (slip) boundary of surface shear stress. The numerical solution does not need an iterative process and can simultaneously give rise to fluid pressure distribution, wall slip velocity and surface shear stress. We analysed the squeeze film flow between two parallel discs and the hydrodynamics of a finite slider gap with wall slip. Our numerical solutions show that wall slip is first developed in the large pressure gradient zone, where a high surface shear stress is easily generated, and then the slip zone is enlarged with the increase in the shear rate. Wall slip dramatically affects generation of the hydrodynamic pressure. Copyright © 2006 John Wiley & Sons, Ltd. [source] Description method for spatio-temporal regions in a video and its applicationINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 5 2003Toshimitsu Kaneko Abstract A new description method for spatio-temporal regions in a video is proposed. It is efficient in terms of description data size and computational complexity under the condition that the regions in each frame can be approximated by simple figures. It approximates the object region in a frame by a simple figure such as a rectangle, an ellipse, or a polygon, and describes the coordinates of its representative points (vertices). Then, the motions of the representative points are described by polynomial spline functions to express the regions in the following frames efficiently. The proposed method is adopted in the MPEG-7 standard to provide the functionality of spatio-temporal location description. Experimental results using synthesized and real videos are presented to show the efficiency. Also, movie-centric hypermedia, a typical application of this description method, is introduced in this article. © 2004 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 257,266, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10062 [source] Design of low-order controllers satisfying sensitivity constraints for unstructured uncertain plantsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 16 2004O. Yaniv Abstract This paper presents a simple analytically based algorithm for the design of reduced-order controllers satisfying frequency-dependent sensitivity specifications for SISO plants having unstructured uncertainty. The uncertainties can be additive as well as multiplicative, and can take the form of circles, polygons or sectors located around a nominal plant. Moreover, the circle radius and polygon and sector sizes may depend on the frequency. The proposed method is applicable to both continuous and discrete designs. Copyright © 2004 John Wiley & Sons, Ltd. [source] Solving the irregular strip packing problem via guided local search for overlap minimizationINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 6 2009Shunji Umetani Abstract The irregular strip-packing problem (ISP) requires a given set of non-convex polygons to be placed without overlap within a rectangular container having a fixed width and a variable length, which is to be minimized. As a core sub-problem to solve ISP, we consider an overlap minimization problem (OMP) whose objective is to place all polygons into a container with given width and length so that the total amount of overlap between polygons is made as small as possible. We propose to use directional penetration depths to measure the amount of overlap between a pair of polygons, and present an efficient algorithm to find a position with the minimum overlap for each polygon when it is translated in a specified direction. Based on this, we develop a local search algorithm for OMP that translates a polygon in horizontal and vertical directions alternately. Then we incorporate it in our algorithm for OMP, which is a variant of the guided local search algorithm. Computational results show that our algorithm improves the best-known values of some well-known benchmark instances. [source] Conservation strategy maps: a tool to facilitate biodiversity action planning illustrated using the heath fritillary butterflyJOURNAL OF APPLIED ECOLOGY, Issue 2 2003G. J. Holloway Summary 1.,The UK Biodiversity Action Plan (UKBAP) identifies invertebrate species in danger of national extinction. For many of these species, targets for recovery specify the number of populations that should exist by a specific future date but offer no procedure to plan strategically to achieve the target for any species. 2.,Here we describe techniques based upon geographic information systems (GIS) that produce conservation strategy maps (CSM) to assist with achieving recovery targets based on all available and relevant information. 3.,The heath fritillary Mellicta athalia is a UKBAP species used here to illustrate the use of CSM. A phase 1 habitat survey was used to identify habitat polygons across the county of Kent, UK. These were systematically filtered using relevant habitat, botanical and autecological data to identify seven types of polygon, including those with extant colonies or in the vicinity of extant colonies, areas managed for conservation but without colonies, and polygons that had the appropriate habitat structure and may therefore be suitable for reintroduction. 4.,Five clusters of polygons of interest were found across the study area. The CSM of two of them are illustrated here: the Blean Wood complex, which contains the existing colonies of heath fritillary in Kent, and the Orlestone Forest complex, which offers opportunities for reintroduction. 5.,Synthesis and applications. Although the CSM concept is illustrated here for the UK, we suggest that CSM could be part of species conservation programmes throughout the world. CSM are dynamic and should be stored in electronic format, preferably on the world-wide web, so that they can be easily viewed and updated. CSM can be used to illustrate opportunities and to develop strategies with scientists and non-scientists, enabling the engagement of all communities in a conservation programme. CSM for different years can be presented to illustrate the progress of a plan or to provide continuous feedback on how a field scenario develops. [source] Formation of a geometric pattern with a mobile wireless sensor networkJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 10 2004Justin Lee Mobile wireless sensor networks (MWSNs) will enable information systems to gather detailed information about the environment on an unprecedented scale. These self-organizing, distributed networks of sensors, processors, and actuators that are capable of movement have a broad range of potential applications, including military reconnaissance, surveillance, planetary exploration, and geophysical mapping. In many of the foreseen applications, the MWSN will need to form a geometric pattern without assistance from the user. In military reconnaissance, for example, the nodes will be dropped onto the battlefield from a plane and land at random positions. The nodes will be expected to arrange themselves into a predetermined formation in order to perform a specific task. Thus, we present algorithms for forming a line, circle, and regular polygon from a given set of random positions. The algorithms are distributed and use no communication between the nodes to minimize energy consumption. Unlike past studies of geometric problems where algorithms are either tested in simulations where each node has global knowledge of all the other nodes or implemented on a small number of robots, the robustness of our algorithms has been studied with simulations that model the sensor system in detail. The simulations demonstrate that the algorithms are robust against random errors in the sensors and actuators. © 2004 Wiley Periodicals, Inc. [source] The Circumpolar Arctic vegetation mapJOURNAL OF VEGETATION SCIENCE, Issue 3 2005Donald A. Walker Abstract. Question: What are the major vegetation units in the Arctic, what is their composition, and how are they distributed among major bioclimate subzones and countries? Location: The Arctic tundra region, north of the tree line. Methods: A photo-interpretive approach was used to delineate the vegetation onto an Advanced Very High Resolution Radiometer (AVHRR) base image. Mapping experts within nine Arctic regions prepared draft maps using geographic information technology (ArcInfo) of their portion of the Arctic, and these were later synthesized to make the final map. Area analysis of the map was done according to bioclimate subzones, and country. The integrated mapping procedures resulted in other maps of vegetation, topography, soils, landscapes, lake cover, substrate pH, and above-ground biomass. Results: The final map was published at 1:7 500 000 scale map. Within the Arctic (total area = 7.11 × 106 km2), about 5.05 × 106 km2 is vegetated. The remainder is ice covered. The map legend generally portrays the zonal vegetation within each map polygon. About 26% of the vegetated area is erect shrublands, 18% peaty graminoid tundras, 13% mountain complexes, 12% barrens, 11% mineral graminoid tundras, 11% prostrate-shrub tundras, and 7% wetlands. Canada has by far the most terrain in the High Arctic mostly associated with abundant barren types and prostrate dwarf-shrub tundra, whereas Russia has the largest area in the Low Arctic, predominantly low-shrub tundra. Conclusions: The CAVM is the first vegetation map of an entire global biome at a comparable resolution. The consistent treatment of the vegetation across the circumpolar Arctic, abundant ancillary material, and digital database should promote the application to numerous land-use, and climate-change applications and will make updating the map relatively easy. [source] Flexibility of Steiner trees in uniform orientation metricsNETWORKS: AN INTERNATIONAL JOURNAL, Issue 3 2005M. Brazil Abstract We present some fundamental flexibility properties for minimum length networks (known as Steiner minimum trees) interconnecting a given set of points in an environment in which edge segments are restricted to , uniformly oriented directions. These networks are referred to as ,-SMTs. They promise to play an increasingly important role in the future of optimal wire routing in VLSI physical design, particularly for the next generation of VLSI circuits. In this article we develop the concept of a flexibility polygon for a ,-SMT, which is a region representing the union of all ,-SMTs with the same topology on a given set of points. We show that this polygon can be constructed, for a given point set and given topology, in linear time. We discuss some of the future applications of this polygon, which can be thought of as a geometric representation of the amount of flexibility inherent in a given ,-SMT. © 2005 Wiley Periodicals, Inc. NETWORKS, Vol. 46(3), 142,153 2005 [source] A method for quantifying rotational symmetryNEW PHYTOLOGIST, Issue 4 2007Frank M. Frey Summary ,,Here, a new approach for quantifying rotational symmetry based on vector analysis was described and compared with information obtained from a geometric morphometric analysis and a technique based on distance alone. ,,A new method was developed that generates a polygon from the length and angle data of a structure and then quantifies the minimum change necessary to convert that polygon into a regular polygon. This technique yielded an asymmetry score (s) that can range from 0 (perfect symmetry) to 1 (complete asymmetry). Using digital images of Geranium robertianum flowers, this new method was compared with a technique based on lengths alone and with established geometric morphometric methods used to quantify shape variation. ,,Asymmetry scores (s) more clearly described variation in symmetry and were more consistent with a visual assessment of the images than either comparative technique. ,,This procedure is the first to quantify the asymmetry of radial structures accurately, uses easily obtainable measures to calculate the asymmetry score and allows comparisons among individuals and species, even when the comparisons involve structures with different patterns of symmetry. This technique enables the rigorous analysis of polysymmetric structures and provides a foundation for a better understanding of symmetry in nature. [source] For the inf-sup condition on mesh-dependent norms on a nonconvex polygonNUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS, Issue 5 2008Sungkyu Choi Abstract It is shown that the inf-sup condition, called the Babuska,Brezzi condition, is valid for certain mesh-dependent norms on a nonconvex polygonal domain. A bilinear form that is derived by inserting the corner singularity expansion into the Laplace equation is considered. A mesh-dependent fractional norm related to the least order of the corner singularity at a concave vertex is considered. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008 [source] Ground thermal conditions in a frost-crack polygon, a palsa and a mineral palsa (lithalsa) in the discontinuous permafrost zone, northern SwedenPERMAFROST AND PERIGLACIAL PROCESSES, Issue 4 2001Bo Westin Abstract Ground temperature measurements were collected during 1997 to 1998 at three locations in the discontinuous permafrost zone in northern Sweden. Measurements were made in two frost-crack polygons, two palsas and a mineral palsa (lithalsa). Important for the formation of permafrost at all locations are (i) the absence of snow and, (ii) local soil properties. The seasonal variation in apparent thermal diffusivity,with higher diffusivities in summer than in winter in the mineral soil of the frost-crack polygon and relatively little seasonal variation in the peat of the palsas,is the main cause for the cooler conditions in the palsas in summer. Morphology adds to the temperature fluctuations as indicated by highly fluctuating ground temperatures in the dome-shaped mineral palsa as compared to the frost-crack polygon. Occasional ground temperature gradients of more than ,10 °C/m are probably sufficient for seasonal frost cracking. Copyright © 2001 John Wiley & Sons, Ltd. RÉSUMÉ En trois endroits de la zone du pergélisol discontinu, Staloluokta, Kisuris, et Laivadalen dans le nord de la Suède où les températures moyennes annuelles sont d'environ,0.9°C, des mesures de température du sol ont été réalisées jusqu'à des profondeurs de 125 cm dans deux polygones de fissures de gel, deux palses et une palse minérale (lithalse). Le facteur le plus important pour la formation du pergélisol en tous les sites étudiés paraît être l'absence de couverture neigeuse et secondairement les propriétés des sols. Le pergélisol a été trouvé dans les sols des polygones de fissures de gel, dans les palses et la palse minérale, en des endroits où probablement une faible couverture de neige existe en hiver. La variation saisonnière de la diffusivité thermique apparente,avec une plus grande diffusivité en été qu'en hiver dans le sol minéral du polygone de fissure de gel et relativement peu de variations saisonnières dans la tourbe des palses,a été la cause principale des conditions plus froides dans la palse en hiver. La morphologie des formes périglaciaires peut engendrer des fluctuations de température plus importantes comme l'indique la grande variation de la température du sol dans une palse minérale en forme de dôme par comparaison avec ce qui se produit dans un polygone de fissures de gel de la même région. En outre, des gradients de température de plus de 10°C/m dans le sol gelé de la majeure partie des formes étudiées ont été probablement suffisants pour permettre la fissuration par contraction thermique. Copyright © 2001 John Wiley & Sons, Ltd. [source] Starch source, screw configuration and injection of steam into the barrel affect the physical quality of extruded fish feedAQUACULTURE RESEARCH, Issue 3 2010Mette Sørensen Abstract This experiment investigated the physical qualities (,Holmen' durability; ,tumbling box' durability; and pellet strength, length and diameter) of extruded fishmeal-based feeds produced using different starch sources, screw configurations, with or without steam injected in the barrel. The starch sources tested were native or pre-gelatinized potato starch (PGS), wheat starch (WS), whole wheat (WW) or a combination of WS and WW. Screw configurations were a polygon element, followed by two left-pitched segments, Polygon_2L; a polygon, followed by one left-pitched and one right-pitched element, Polygon_LR; and no polygon section, alternating left- and right-pitched elements, LRLR. Starch source and screw configuration affected the physical quality the most. Pellets produced with LRLR had the highest ,Holmen' durability (76%), hardness (30 N) and the least diameter (5.3 mm). The lowest durability (37%) and hardness (22 N) were obtained with Polygon_LR. Potato starch yielded higher expansion than cereal starch. The highest ,Holmen' durability was seen for PGS (79%), while WS yielded the lowest value (44%). Injection of steam reduced hardness and ,Holmen' durability, but provided a minor overall contribution to physical quality compared with the starch source and screw configuration. ,Holmen' durability appeared to be suitable to unveil variation (37,79%) in physical quality, while ,Tumbling box' durability (98.4,98.8%) did not prove efficient. [source] Movement of sonically tagged bluespine unicornfish, Naso unicornis, in relation to marine reserve boundaries in Rodrigues, western Indian OceanAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2010Emily Hardman Abstract 1.The lagoon fishery of Rodrigues has considerable socio-economic importance; however, catches have declined by 50% in recent years. The bluespine unicornfish, Naso unicornis (Forsskål 1775) is an important component of the fishery. 2.To begin to assess whether marine reserves might benefit this species, sonic telemetry was used to track individual fish in one of Rodrigues' four marine reserves. Seven unicornfish were caught in the Grand Bassin reserve and tagged with abdominally implanted acoustic tags. 3.Over a period of 57 days their locations were determined up to 21 times using a hand held hydrophone and receiver. Individual minimum convex polygon (MCP) home ranges varied from ,10 000,m2 to ,274,000,m2 and were not correlated with fish size. Kernel estimates of core areas (50% utilization distribution) varied from ,5000,m2 to ,175,000,m2. All seven fish stayed within the marine reserve and the largest home range occupied less than ,2% of the area of the marine reserve. 4.Fish remained on the outside edge of the lagoon on the shallow reef slope and among coral patches. These findings suggest that bluespined unicornfish biomass and numbers should increase if the Grand Bassin marine reserve is closed to fishing. Long-term monitoring will, however, be required to demonstrate this outcome. Copyright © 2010 John Wiley & Sons, Ltd. [source] Geophysical study of a Pre-Hispanic lakeshore settlement, Chiconahuapan Lake, MexicoARCHAEOLOGICAL PROSPECTION, Issue 1 2010R. E. Chávez Abstract Results of a combined geophysical survey carried out along the northern shore of Lake Chiconahuapan in central Mexico are presented. The site contains a series of mounds found between the lakeshore and the ceremonial centre named La Campana-Tepozoco Hill. Those features are the remains of habitation complexes built by the lake residents about 1100 years ago. Archaeological excavations performed towards the northeastern margins of the lake uncovered rectangular clusters of basaltic rocks forming the foundations of ancient dwellings, surrounded by a barrier (,bordo'), built to prevent floods. A mound located close to the ceremonial centre was studied using the vertical magnetic gradient (VMG), ground-penetrating radar (GPR) and electric tomography (ET) methods. Interesting magnetic anomalies were found towards the central portion of the mound and one of these was modelled with a three-dimensional magnetic polygon. The GPR studies unveiled a circular feature in the central portion of the mound that could be associated with a bordo. A rectangular structure was also interpreted within the limits of that structure, which is probably the location of ancient dwelling foundations. Electric tomography profiles were collected in the area, around the VMG anomaly. The resistivity model computed shows the presence of a high-resistivity layer, which displays discontinuities within the area defined by the bordo. Presumably, the ancient settlers built their constructions on top of this horizon. The geophysical results reveal a rather complex habitat within the mound. The larger size of the bordo (ca. 30,m in diameter) compared with others already studied by archaeologists makes us believe that the purpose of the site was of administrative use or hosted a wealthy group of people. Dwelling foundations are found within the limits of the barrier. Copyright © 2009 John Wiley & Sons, Ltd. [source] Crystallographic model quality at a glanceACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2009Ludmila Urzhumtseva A crystallographic macromolecular model is typically characterized by a list of quality criteria, such as R factors, deviations from ideal stereochemistry and average B factors, which are usually provided as tables in publications or in structural databases. In order to facilitate a quick model-quality evaluation, a graphical representation is proposed. Each key parameter such as R factor or bond-length deviation from `ideal values' is shown graphically as a point on a `ruler'. These rulers are plotted as a set of lines with the same origin, forming a hub and spokes. Different parts of the rulers are coloured differently to reflect the frequency (red for a low frequency, blue for a high frequency) with which the corresponding values are observed in a reference set of structures determined previously. The points for a given model marked on these lines are connected to form a polygon. A polygon that is strongly compressed or dilated along some axes reveals unusually low or high values of the corresponding characteristics. Polygon vertices in `red zones' indicate parameters which lie outside typical values. [source] Home range dynamics of the yellow-footed rock-wallaby (Petrogale xanthopus celeris) in central-western QueenslandAUSTRAL ECOLOGY, Issue 1 2009ANDY SHARP Abstract Analyses of the interspecific differences in macropod home range size suggest that habitat productivity exerts a greater influence on range size than does body mass. This relationship is also apparent within the rock-wallaby genus. Lim reported that yellow-footed rock-wallabies (Petrogale xanthopus xanthopus) inhabiting the semi-arid Flinders Ranges (South Australia) had a mean home range of 170 ha. While consistent with the hypothesis that species inhabiting less productive habitats will require larger ranges to fulfil their energetic requirements, the ranges reported by Lim were considerably larger than those observed for heavier sympatric macropods. The aim of the current study was to document the home range dynamics of P. x. celeris in central-western Queensland and undertake a comparison with those reported for their southern counterparts. Wallaby movements were monitored at Idalia National Park, between winter 1992 and winter 1994. Male foraging ranges (95% fixed kernel; 15.4 ha, SD = ±7.8 ha) were found to be significantly larger than those of female wallabies (11.3 ha, SD = ±4.9 ha). Because of varying distances to the wallabies' favoured foraging ground (i.e. an adjacent herb field), the direction in which the wallabies moved to forage also significantly affected range size. Mean home range size was estimated to be 23.5 ha (SD = ±15.2 ha; 95% fixed kernel) and 67.5 ha (SD = ±22.4 ha; 100% minimum convex polygon). The discrepancy between these two estimates resulted from the exclusion of locations, from the 95% kernel estimates, when the wallabies moved to a water source 1.5 km distant from the colony site. The observed foraging and home ranges approximated those that could be expected for a macropod inhabiting the semi-arid zone (i.e. 2.4 times larger-than-predicted from body mass alone). Possible reasons for the disparity between the current study and that of Lim are examined. [source] Home range and movements of male feral cats (Felis catus) in a semiarid woodland environment in central AustraliaAUSTRAL ECOLOGY, Issue 1 2001G. P. EDWARDS Abstract There is a paucity of data on the movement patterns of feral cats in Australia. Such data can be used to refine control strategies and improve track-based methods of monitoring populations of feral cats. In this study the home ranges and movements of male feral cats were examined over 3.5 years in a semiarid woodland environment in central Australia. Two home range estimators were used in the examination: (i) minimum convex polygon (MCP); and (ii) fixed kernel. The most widely used method of estimating home range in feral cats is MCP, while the fixed kernel method can be used to identify core areas within a home range. On the basis of the MCP method, the long-term home ranges of feral cats in central Australia were much larger than those recorded elsewhere (mean, 2210.5 ha). Twenty-four hour home ranges were much smaller (mean, 249.7 ha) and feral cats periodically shifted their 24 h ranges within the bounds of their long-term home ranges. Core area analysis indicated marked heterogeneity of space use by male feral cats. Several instances where feral cats moved large distances (up to 34 km) were recorded. These long distance movements may have been caused by nutritional stress. Using data from the literature, it is shown that prey availability is a primary determinant of long-term home range size in feral cats. The relevance of the results to the design of management strategies for feral cats in central Australia is also discussed. [source] Home range and movements of male feral cats (Felis catus) in a semiarid woodland environment in central AustraliaAUSTRAL ECOLOGY, Issue 1 2001G. P. Edwards Abstract There is a paucity of data on the movement patterns of feral cats in Australia. Such data can be used to refine control strategies and improve track-based methods of monitoring populations of feral cats. In this study the home ranges and movements of male feral cats were examined over 3.5 years in a semiarid woodland environment in central Australia. Two home range estimators were used in the examination: (i) minimum convex polygon (MCP); and (ii) fixed kernel. The most widely used method of estimating home range in feral cats is MCP, while the fixed kernel method can be used to identify core areas within a home range. On the basis of the MCP method, the long-term home ranges of feral cats in central Australia were much larger than those recorded elsewhere (mean, 2210.5 ha). Twenty-four hour home ranges were much smaller (mean, 249.7 ha) and feral cats periodically shifted their 24 h ranges within the bounds of their long-term home ranges. Core area analysis indicated marked heterogeneity of space use by male feral cats. Several instances where feral cats moved large distances (up to 34 km) were recorded. These long distance movements may have been caused by nutritional stress. Using data from the literature, it is shown that prey availability is a primary determinant of long-term home range size in feral cats. The relevance of the results to the design of management strategies for feral cats in central Australia is also discussed. [source] Linkage Isomerism and Spin Frustration in Heterometallic Rings: Synthesis, Structural Characterization, and Magnetic and EPR Spectroscopic Studies of Cr7Ni, Cr6Ni2, and Cr7Ni2 Rings Templated About Imidazolium CationsCHEMISTRY - A EUROPEAN JOURNAL, Issue 47 2009Angelika Abstract The synthesis and structural characterization of three heterometallic rings templated about imidazolium cations is reported. The compounds are [2,4-DiMe-ImidH][Cr7NiIIF8(O2CtBu)16] 1 (2,4-DiMe-ImidH=the cation of 2,4-dimethylimidazole), [ImidH]2[Cr6NiII2F8(O2CCtBu)16] 2 (ImidH=the cation of imidazole), and [1-Bz-ImidH]2 [Cr7NiII2F9(O2CtBu)18] 3 (1-Bz-ImidH=the cation of 1-benzylimidazole). The structures show the formation of octagonal arrays of metals for 1 and 2 and a nonagon of metal centers for 3. In all cases the edges of the polygon are bridged by a single fluoride and two pivalate ligands, and the position of the divalent metal centers cannot be distinguished by X-ray diffraction. Magnetic studies combined with EPR spectroscopy allow the characterization of the magnetic states of the compounds. In each case the exchange is antiferromagnetic with a magnetic exchange parameter J,,5.8,cm,1, and it is not possible to differentiate the exchange between two CrIII centers (JCrCr) from the exchange between a CrIII and a NiII center (JCrNi). For 2 there is evidence for the presence of at least two, possibly four, linkage isomers of the heterometallic ring, caused by the presence of two divalent metal centers in the ring. The EPR spectroscopy of 3 suggests an S=1/2 ground state of the ring and that it is likely that only one linkage isomer is present. [source] Multi-resolution collision handling for cloth-like simulationsCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2005Nitin Jain Abstract We present a novel multi-resolution algorithm for simulation of complex cloth-like deforming meshes. Our algorithm precomputes a multi-resolution hierarchy by using a combination of ,chromatic decomposition'1 and polygonal simplification of the underlying mesh. At runtime we selectively refine or coarsen the mesh based on the collision proximity of the mesh primitives with non-adjacent primitives. Our algorithm handles all kind of contacts, including self collisions among mesh primitives. The multi-resolution hierarchy is used to compute simplification of contact manifolds and to accelerate collision detection and response computations. We have implemented our algorithm on a high-end PC and applied it to complex simulations with tens of thousands of polygons. In practice, our algorithm is able to achieve interactive performance, while maintaining good visual fidelity. Copyright © 2005 John Wiley & Sons, Ltd. [source] Accurate automatic visible speech synthesis of arbitrary 3D models based on concatenation of diviseme motion capture dataCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 5 2004Jiyong Ma Abstract We present a technique for accurate automatic visible speech synthesis from textual input. When provided with a speech waveform and the text of a spoken sentence, the system produces accurate visible speech synchronized with the audio signal. To develop the system, we collected motion capture data from a speaker's face during production of a set of words containing all diviseme sequences in English. The motion capture points from the speaker's face are retargeted to the vertices of the polygons of a 3D face model. When synthesizing a new utterance, the system locates the required sequence of divisemes, shrinks or expands each diviseme based on the desired phoneme segment durations in the target utterance, then moves the polygons in the regions of the lips and lower face to correspond to the spatial coordinates of the motion capture data. The motion mapping is realized by a key-shape mapping function learned by a set of viseme examples in the source and target faces. A well-posed numerical algorithm estimates the shape blending coefficients. Time warping and motion vector blending at the juncture of two divisemes and the algorithm to search the optimal concatenated visible speech are also developed to provide the final concatenative motion sequence. Copyright © 2004 John Wiley & Sons, Ltd. [source] Barycentric Coordinates on SurfacesCOMPUTER GRAPHICS FORUM, Issue 5 2010Raif M. Rustamov This paper introduces a method for defining and efficiently computing barycentric coordinates with respect to polygons on general surfaces. Our construction is geared towards injective polygons (polygons that can be enclosed in a metric ball of an appropriate size) and is based on replacing the linear precision property of planar coordinates by a requirement in terms of center of mass, and generalizing this requirement to the surface setting. We show that the resulting surface barycentric coordinates can be computed using planar barycentric coordinates with respect to a polygon in the tangent plane. We prove theoretically that the surface coordinates properly generalize the planar coordinates and carry some of their useful properties such as unique reconstruction of a point given its coordinates, uniqueness for triangles, edge linearity, similarity invariance, and smoothness; in addition, these coordinates are insensitive to isometric deformations and can be used to reconstruct isometries. We show empirically that surface coordinates are shape-aware with consistent gross behavior across different surfaces, are well-behaved for different polygon types/locations on variety of surface forms, and that they are fast to compute. Finally, we demonstrate effectiveness of surface coordinates for interpolation, decal mapping, and correspondence refinement. [source] Moving Least Squares CoordinatesCOMPUTER GRAPHICS FORUM, Issue 5 2010Josiah Manson Abstract We propose a new family of barycentric coordinates that have closed-forms for arbitrary 2D polygons. These coordinates are easy to compute and have linear precision even for open polygons. Not only do these coordinates have linear precision, but we can create coordinates that reproduce polynomials of a set degree m as long as degree m polynomials are specified along the boundary of the polygon. We also show how to extend these coordinates to interpolate derivatives specified on the boundary. [source] A framework for quad/triangle subdivision surface fitting: Application to mechanical objectsCOMPUTER GRAPHICS FORUM, Issue 1 2007Guillaume Lavoué Abstract In this paper we present a new framework for subdivision surface approximation of three-dimensional models represented by polygonal meshes. Our approach, particularly suited for mechanical or Computer Aided Design (CAD) parts, produces a mixed quadrangle-triangle control mesh, optimized in terms of face and vertex numbers while remaining independent of the connectivity of the input mesh. Our algorithm begins with a decomposition of the object into surface patches. The main idea is to approximate the region boundaries first and then the interior data. Thus, for each patch, a first step approximates the boundaries with subdivision curves (associated with control polygons) and creates an initial subdivision surface by linking the boundary control points with respect to the lines of curvature of the target surface. Then, a second step optimizes the initial subdivision surface by iteratively moving control points and enriching regions according to the error distribution. The final control mesh defining the whole model is then created assembling every local subdivision control meshes. This control polyhedron is much more compact than the original mesh and visually represents the same shape after several subdivision steps, hence it is particularly suitable for compression and visualization tasks. Experiments conducted on several mechanical models have proven the coherency and the efficiency of our algorithm, compared with existing methods. [source] Hierarchical Higher Order Face Cluster Radiosity for Global Illumination Walkthroughs of Complex Non-Diffuse EnvironmentsCOMPUTER GRAPHICS FORUM, Issue 3 2003Enrico Gobbetti We present an algorithm for simulating global illumination in scenes composed of highly tessellated objects withdiffuse or moderately glossy reflectance. The solution method is a higher order extension of the face cluster radiositytechnique. It combines face clustering, multiresolution visibility, vector radiosity, and higher order baseswith a modified progressive shooting iteration to rapidly produce visually continuous solutions with limited memoryrequirements. The output of the method is a vector irradiance map that partitions input models into areaswhere global illumination is well approximated using the selected basis. The programming capabilities of moderncommodity graphics architectures are exploited to render illuminated models directly from the vector irradiancemap, exploiting hardware acceleration for approximating view dependent illumination during interactive walkthroughs.Using this algorithm, visually compelling global illumination solutions for scenes of over one millioninput polygons can be computed in minutes and examined interactively on common graphics personal computers. Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Picture and Image Generation; I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism. [source] Automatic Creation of Object Hierarchies for Radiosity ClusteringCOMPUTER GRAPHICS FORUM, Issue 4 2000Gordon Müller Using object clusters for hierarchical radiosity greatly improves the efficiency and thus usability of radiosity computations. By eliminating the quadratic starting phase very large scenes containing about 100k polygons can be handled efficiently. Although the main algorithm extends rather easily to using object clusters, the creation of ,good' object hierarchies is a difficult task both in terms of construction time and in the way how surfaces or objects are grouped to clusters. The quality of an object hierarchy for clustering depends on its ability to accurately simulate the hierarchy of the energy flow in a given scene. Additionally it should support visibility computations by providing efficient ray acceleration techniques. In this paper we will present a new approach of building hierarchies of object clusters. Our hybrid structuring algorithm provides accuracy and speed by combining a highly optimized bounding volume hierarchy together with uniform spatial subdivisions for nodes with regular object densities. The algorithm works without user intervention and is well suited for a wide variety of scenes. First results of using these hierarchies in a radiosity clustering environment are very promising and will be presented here. The combination of very deep hierarchies (we use a binary tree) together with an efficient ray acceleration structure shifts the computational effort away from form factor and visibility calculation towards accurately propagating the energy through the hierarchy. We will show how an efficient single pass gathering can be used to minimize traversal costs. [source] | |||||||||||||||||||||||||||||||