Filters








316 Hits in 4.9 sec

Page 2248 of Mathematical Reviews Vol. , Issue 96d [page]

1996 Mathematical Reviews  
An F-graph is the visibility graph V (P) of a funnel-shaped poly- gon P.  ...  of a funnel-shaped polygon.  ... 

Computational Aspects of Problems on Visibility and Disk Graph Representations [article]

Onur Çağırıcı
2021 arXiv   pre-print
Besides, we have shown that the 5-colorability problem is NP-complete on visibility graphs of simple polygons, and 4-colorability is NP-complete on visibility graphs of polygons with holes.  ...  To model this property, we introduce unit disk visibility graphs, and show that the 3-colorability problem is NP-complete for unit disk visibility graphs of a set of line segments, and a polygon with holes  ...  Kára et al. characterized 3-colourable visibility graphs of point sets and described a super-polynomial lower bound on the chromatic number with respect to the clique number of visibility graphs of point  ... 
arXiv:2111.00609v1 fatcat:3xl2eklvfffevgpmriawnjynym

Unsolved Problems in Visibility Graphs of Points, Segments and Polygons [article]

Subir Kumar Ghosh, Partha Pratim Goswami
2012 arXiv   pre-print
In this survey paper, we present open problems and conjectures on visibility graphs of points, segments and polygons along with necessary backgrounds for understanding them.  ...  Choi, Shin and Chwa [19] characterized funnel-shaped polygons, also called towers, and gave an O(n) time recognition algorithm.  ...  Unlike bar visibility graphs, no characterization of rectangle visibility graphs are known, and moreover, Shermer [105] has shown that the problem of recognizing them is NP-complete.  ... 
arXiv:1012.5187v4 fatcat:bt6jihgqwrblnavyaoeju2udtu

Characterizing and recognizing weak visibility polygons

Subir Kumar Ghosh, Anil Maheshwari, Sudebkumar Prasant Pal, Sanjeev Saluja, C.E. Veni Madhavan
1993 Computational geometry  
In this paper we derive properties of shortest paths in weak visibility polygons and present a characterization of weak visibility polygons in terms of shortest paths between vertices.  ...  exists, where E is the size of the visibility graph of P and (ii) an O(n*) time algorithm for computing the maximum hidden vertex set in an n-sided polygon weakly visible from a convex edge.  ...  The visibility graph of P is the graph defined with the set of vertices of P as the vertex set and the set of visible pairs of vertices of P as the edge set.  ... 
doi:10.1016/0925-7721(93)90010-4 fatcat:khixzzmz2rdg7cqdvl3x6zkaly

An Improved Algorithm for Reconstructing a Simple Polygon from the Visibility Angles [article]

Danny Z. Chen, Haitao Wang
2010 arXiv   pre-print
In this paper, we study the following problem of reconstructing a simple polygon: Given a cyclically ordered vertex sequence of an unknown simple polygon P of n vertices and, for each vertex v of P, the  ...  sequence of angles defined by all the visible vertices of v in P, reconstruct the polygon P (up to similarity).  ...  Choi, Shin, and Chwa [4] , and Colley, Lubiw, and Spinrad [5] characterized and recognized the visibility graphs of funnel-shaped polygons.  ... 
arXiv:1009.2521v1 fatcat:cdv56ozffrgjxorj2k6rxw3s4u

First description of Skolithos burrows from the Cambrian–Ordovician boundary interval of the Central Anti-Atlas, Morocco

A Azizi, O Vinn, K El Hariri, A Hafid, K Kouraiss
2017 Proceedings of the Estonian Academy of Sciences. Geology = Teaduste Akadeemia toimetised  
The burrows of Skolithos linearis associated with that level are straight to slightly curved, 2-15 cm long and 2-4 mm wide.  ...  The first level occurs at the boundary between the Azlag Formation and Jbel Lmgaysmat Formation (Furongian), where the burrows are 5-80 cm long and 3-7 mm wide, straight to slightly curved, with mostly  ...  The funnel shape of the aperture may have resulted from the back-and forward movement of the worm-like organisms inhabiting the burrows.  ... 
doi:10.3176/earth.2017.13 fatcat:6kfuuxqzsbgzdc6zlkqyitcyse

Illustrated glossary of terms used in foraminiferal research

Lukas HOTTINGER
2006 Carnets de Géologie  
An illustrated glossary of terms used in the analysis of the shells of recent and fossil foraminifera supplemented by a rigorous selection of terms that facilitate an understanding of their biology and  ...  their use in ecology and biostratigraphy.  ...  network that expands at its blind end below the epiderm into a polygonal shape.  ... 
doi:10.4267/2042/5832 fatcat:fewflmszvrcljon62olmm36xsi

A VRML-based anatomical visualization tool for medical education

P.A. Warrick, W.R.J. Funnell
1998 IEEE Transactions on Information Technology in Biomedicine  
The 3-D mode1 is created by automated aligning of the source images (his tologicai sections), interactive segmentation, and 3-D surface reconstruction.  ...  The advent of the Vimial Reality Modeling Language (VRML) as a portable file format for describing the-dimensionai (3-D) scenes has created the ability for researchers, educaton and students to share anatomical  ...  . . . " 4 ) a spatial loiowledge buse descnbing shape and range of variation of structural objects. e.g., the average shape and range of variation of the lateral ventricles (inter-subject variation) and  ... 
doi:10.1109/4233.720523 pmid:10719514 fatcat:vlnceplmjramnb3jv7cbhwdxtm

Late Aptian-Albian primitive Radiolitidae (bivalves, hippuritoidea) from Spain and SW France

J.P. Masse, M. Fenerci-Masse, L. Vilas, C. Arias
2007 Cretaceous research (Print)  
The Eoradiolites cantabricus group of species is mainly Clansayesian-early Albian in age and possesses an advanced evolutionary status, mainly regarding shell size and cellular structure.  ...  Our study shows that the names Sphaerulites and Praeradiolites cannot be applied to pre-Cenomanian Radiolitidae and that Eoradiolites was the foremost genus in Late Aptian-Albian times in terms of species  ...  of funnel plates) (Fig. 18A) .  ... 
doi:10.1016/j.cretres.2006.09.004 fatcat:tim4k3kegvgazjl3ne3gm2vvh4

Polygonal Patterned Ground [chapter]

Nicolas Mangold
2015 Encyclopedia of Planetary Landforms  
Individual pits are characterized by cuspate shapes and alcove-like features and have a typical depth of $20 m. Pits show no preferential orientation.  ...  The narrow crack of the polygon is visible inside the pit (Lefort et al. 2009). Scoria cone(Figs. 1, 2): parasitic cones on Mount Etna, Sicily(Fig. 1), and Parícutin, Mexico.  ...  Composition The undulations are visible during both spring and summer, i.e., both perennial and seasonal polar cap materials show this topography .  ... 
doi:10.1007/978-1-4614-3134-3_276 fatcat:3tkhxovtyjeopaoo2dgcz5eslm

Pāhoehoe [chapter]

2015 Encyclopedia of Planetary Landforms  
Individual pits are characterized by cuspate shapes and alcove-like features and have a typical depth of $20 m. Pits show no preferential orientation.  ...  The narrow crack of the polygon is visible inside the pit (Lefort et al. 2009). Scoria cone(Figs. 1, 2): parasitic cones on Mount Etna, Sicily(Fig. 1), and Parícutin, Mexico.  ...  Composition The undulations are visible during both spring and summer, i.e., both perennial and seasonal polar cap materials show this topography .  ... 
doi:10.1007/978-1-4614-3134-3_100282 fatcat:tyqrpd2h7bg5hioxfi6aoizpba

Submarine and Subaerial Morphological Changes Associated with the 2014 Eruption at Stromboli Island

Daniele Casalbore, Federico Di Traglia, Alessandro Bosman, Claudia Romagnoli, Nicola Casagli, Francesco Latino Chiocci
2021 Remote Sensing  
Differently, fan-shaped features were emplaced during the declining stage of the eruption or in relation to lava overflows and associated gravel flows, suggesting the prevalence of volcaniclastic breccias  ...  Well-defined and steep-sided ridges were created by lava flows during the early stages of the eruption, when effusion rates were high, favoring the penetration into the sea of lava flows as coherent bodies  ...  Acknowledgments: Crew of R/V Urania and Minerva1 are gratefully acknowledged along with the people who took part in the surveys.  ... 
doi:10.3390/rs13112043 fatcat:hilmh36qpfhljlyzovv3e47iia

Discharge Flow of Spherical Particles from a Cylindrical Bin: Experiment and DEM Simulations

Rafał Kobyłka, Joanna Wiącek, Piotr Parafiniuk, Józef Horabik, Maciej Bańda, Mateusz Stasiak, Marek Molenda
2021 Processes  
Numerical simulations of the discharge process were performed, and the micro-mechanics of the discharged particles were described.  ...  The effect of the sliding friction coefficient between particles, rolling friction coefficient, and modulus of elasticity of particles on the clogging process was investigated.  ...  Conflicts of Interest: The authors declare no conflict of interest.  ... 
doi:10.3390/pr9111860 fatcat:fsotjfma4rao7eajiow6xhle6u

Mechanisms of frustrated phagocytic spreading of human neutrophils on antibody-coated surfaces [article]

Emmet A Francis, Hugh Xiao, Lay Heng Teng, Volkmar Heinrich
2022 bioRxiv   pre-print
We visualize the cell-substrate contact region at high resolution and without labels using reflection interference contrast microscopy (RICM) and quantify how the area, shape, and position of the contact  ...  Complex motions of immune cells are an integral part of diapedesis, chemotaxis, phagocytosis, and other vital processes.  ...  Acknowledgements We thank Dr Soichiro Yamada for his help with confocal microscopy, Dr Daniel Kovari for providing MATLAB code for the analysis of the cell-substrate contact regions, and Dr Robert Guy  ... 
doi:10.1101/2022.02.18.481104 fatcat:id55wdd4bvgphhqc2hotwhvoty

Page 1523 of Mathematical Reviews Vol. 28, Issue Index [page]

Mathematical Reviews  
Russian summary) 96a:53020 Choi, Seung-Hak (with Shin, Sung Yong; Chwa, Kyung-Yong) Characterizing and recognizing the visibility graph of a funnel-shaped polygon.  ...  On differential invariants of planar curves and recognizing partially occluded planar shapes. (English summary) 96h:53006 Callahan, Paul B. (with Kosaraju, S.  ... 
« Previous Showing results 1 — 15 out of 316 results