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Search Results: 1 - 10 of 37651 matches for " Borut Lu?ar "
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Improved bound on facial parity edge coloring
Borut Luar,Riste ?krekovski
Mathematics , 2013, DOI: 10.1016/j.disc.2013.05.022
Abstract: A facial parity edge coloring of a 2-edge connected plane graph is an edge coloring where no two consecutive edges of a facial walk of any face receive the same color. Additionally, for every face f and every color c either no edge or an odd number of edges incident to f are colored by c. Czap, Jendrol', Kardo\v{s} and Sotak showed that every 2-edge connected plane graph admits a facial parity edge coloring with at most 20 colors. We improve this bound to 16 colors.
On incidence coloring of Cartesian products of graphs
Petr Gregor,Borut Luar
Mathematics , 2015,
Abstract: An incidence in a graph $G$ is a pair $(v,e)$ where $v$ is a vertex of $G$ and $e$ is an edge of $G$ incident to $v$. Two incidences $(v,e)$ and $(u,f)$ are \textit{adjacent} if at least one of the following holds: $(i)$ $v = u$, $(ii)$ $e = f$, or $(iii)$ $vu \in \{e,f\}$. An incidence coloring of $G$ is a coloring of its incidences assigning distinct colors to adjacent incidences. It was conjectured that at most $\Delta(G) + 2$ colors are needed for an incidence coloring of any graph $G$. The conjecture is false in general, but the bound holds for many classes of graphs. We prove it for a wide subclass of Cartesian products of graphs. As a corollary, we infer that it holds for hypercubes answering in affirmative a conjecture of Pai et al.\~(Pai et al., Incidence coloring of hypercubes, Theor. Comput. Sci. 557 (2014), 59--65).
Community Structure and the Evolution of Interdisciplinarity in Slovenia's Scientific Collaboration Network
Borut Luar, Zoran Levnaji?, Janez Povh, Matja? Perc
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0094429
Abstract: Interaction among the scientific disciplines is of vital importance in modern science. Focusing on the case of Slovenia, we study the dynamics of interdisciplinary sciences from to . Our approach relies on quantifying the interdisciplinarity of research communities detected in the coauthorship network of Slovenian scientists over time. Examining the evolution of the community structure, we find that the frequency of interdisciplinary research is only proportional with the overall growth of the network. Although marginal improvements in favor of interdisciplinarity are inferable during the 70s and 80s, the overall trends during the past 20 years are constant and indicative of stalemate. We conclude that the flow of knowledge between different fields of research in Slovenia is in need of further stimulation.
Strong edge coloring of planar graphs
Dávid Hudák,Borut Luar,Roman Soták,Riste ?krekovski
Mathematics , 2013, DOI: 10.1016/j.disc.2014.02.002
Abstract: A strong edge coloring of a graph is a proper edge coloring where the edges at distance at most two receive distinct colors. It is known that every planar graph with maximum degree D has a strong edge coloring with at most 4D + 4 colors. We show that 3D + 6 colors suffice if the graph has girth 6, and 3D colors suffice if the girth is at least 7. Moreover, we show that cubic planar graphs with girth at least 6 can be strongly edge colored with at most 9 colors.
l-facial edge colorings of graphs
Borut Luar,Martina Mockov?iaková,Roman Soták,Riste ?krekovski,Peter ?ugerek
Mathematics , 2013, DOI: 10.1016/j.dam.2014.10.009
Abstract: An l-facial edge coloring of a plane graph is a coloring of the edges such that any two edges at distance at most l on a boundary walk of some face receive distinct colors. It is conjectured that 3l + 1 colors suffice for an l-facial edge coloring of any plane graph. We prove that 7 colors suffice for a 2-facial edge coloring of any plane graph and therefore confirm the conjecture for l = 2.
Strong edge coloring of subcubic bipartite graphs
Borut Luar,Martina Mockov?iaková,Roman Soták,Riste ?krekovski
Mathematics , 2013,
Abstract: A strong edge coloring of a graph $G$ is a proper edge coloring in which each color class is an induced matching of $G$. In 1993, Brualdi and Quinn Massey proposed a conjecture that every bipartite graph without $4$-cycles and with the maximum degrees of the two partite sets $2$ and $\Delta$ admits a strong edge coloring with at most $\Delta+2$ colors. We prove that this conjecture holds for such graphs with $\Delta=3$. We also confirm the conjecture proposed by Faudree et al. for subcubic bipartite graphs.
Star edge coloring of some classes of graphs
?udmila Bezegová,Borut Luar,Martina Mockov?iaková,Roman Soták,Riste ?krekovski
Mathematics , 2013, DOI: 10.1002/jgt.21862
Abstract: \textit{A star edge coloring} of a graph is a proper edge coloring without bichromatic paths and cycles of length four. In this paper we establish tight upper bounds for trees and subcubic outerplanar graphs, and derive an upper bound for outerplanar graphs.
Analysis of impedance measurements of a suspension of microcapsules using a variable length impedance measurement cell
Dejan Krizaj,Borut Pe?ar
Journal of Electrical Bioimpedance , 2012, DOI: 10.5617/jeb.215
Abstract: Electrical impedance measurements of the suspensions have to take into account the double layer impedance that is due to a very thin charged layer formed at the electrode-electrolite interface. A dedicated measuring cell that enables variation of the distance between the electrodes was developed for investigation of electrical properties of suspensions using two electrode impedance measurements. By varying the distance between the electrodes it is possible to separate the double layer and the suspension impedance from the measured data. From measured and extracted impedances electrical lumped models have been developed. The error of non inclusion of the double layer impedance has been analyzed. The error depends on the frequency of the measurements as well as on the distance between the electrodes.
Simulation of Boiling Flow Experiments Close to CHF with the Neptune_CFD Code
Bo tjan Kon ar,Borut Mavko
Science and Technology of Nuclear Installations , 2008, DOI: 10.1155/2008/732158
Abstract: A three-dimensional two-fluid code Neptune_CFD has been validated against the Arizona State University (ASU) and DEBORA boiling flow experiments. Two-phase flow processes in the subcooled flow boiling regime have been studied on ASU experiments. Within this scope a new wall function has been implemented in the Neptune_CFD code aiming to improve the prediction of flow parameters in the near-wall region. The capability of the code to predict the boiling flow regime close to critical heat flux (CHF) conditions has been verified on selected DEBORA experiments. To predict the onset of CHF regime, a simplified model based on the near-wall values of gas volume fraction was used. The results have shown that the code is able to predict the wall temperature increase and the sharp void fraction peak near the heated wall, which are characteristic phenomena for CHF conditions.
A gastrointestinal stromal tumor: Case report
Till Viktor,?olai Matilda,Pilipovi? Borut,Seni?ar Slavica
Medicinski Pregled , 2002, DOI: 10.2298/mpns0210423t
Abstract: Introduction Gastrointestinal stromal tumors represent extremely rare tumors of the gastrointestinal system, especially when localized on the small intestine. Case report We report a case of a female patient, with recurrent gastrointestinal bleeding and severe anemia, caused by gastrointestinal stromal tumor of the small intestine. After negative endoscopic findings, she underwent radiological examination of the small intestine. Primary diagnostic radiological evaluation included: small intestine passage enteroclysis, computed tomography of the abdominal cavity and selective angiographic study of the three major aortic branches that supply the gastrointestinal tract in the abdomen (celiac axis, superior mesenteric artery and inferior mesenteric artery). Secondly, ultrasound of abdominal cavity was performed. Findings of small intestine passage and enteroclysis were negative. The tumor was visualized by computed tomography and ultrasound, but without distinctive anatomical localization in the abdominal cavity. Discussion The diagnostic dilemma has been resolved by using selective angiographic examination of celiac axis and superior mesenteric artery and thus a tumor formation was visualized in the mesenterium of the small intestine. Radiological findings were confirmed by surgery. Histopathological findings were positive for gastrointestinal stromal tumor. Conclusion Gastrointestinal stromal tumors of the small intestine rarely cause recurrent bleeding, but they should be included in differential diagnosis.
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