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4. [Theta]graceful labelings of partial cubesBoštjan Brešar, Sandi Klavžar, 2006, izvirni znanstveni članek Opis: Delne kocke so grafi, ki dopuščajo izometrične vložitve v hiperkocke. V članku so vpeljane ▫$Theta$▫gracilne označitve delnih kock kot naravna razširitev gracilnih označitev dreves. Pokazano je, da so različni razredi delnih kock ▫$Theta$▫gracilni, na primer sodi cikli, Fibonaccijeve kocke in (na novo vpeljane) leksikografske podkocke. Kartezični produkt ▫$Theta$▫gracilnih delnih kock je spet tak in sprašujemo se, ali je morda vsaka delna kocka ▫$Theta$▫gracilna. Pokazana je povezava med ▫$Theta$▫gracilnimi označitvami in reprezentacijami celih števil v določenih številskih sistemih. Predlaganih je tudi nekaj smeri za nadaljnje raziskovanje. Ključne besede: matematika, teorija grafov, drevesa, RingelKotzigova domneva, delne kocke, Fibonaccijeve kocke, hiperkocke, mathematics, graph theory, graceful labelings, trees, RingelKotzig conjecture, partial cubes, Fibonacci cubes, hypercubes Objavljeno: 10.07.2015; Ogledov: 301; Prenosov: 17 Povezava na celotno besedilo 
5. Reconstructing 3D curves with euclidean minimal spanning treesSimon Kolmanič, Nikola Guid, 2006, izvirni znanstveni članek Opis: In this paper, we present a new efficient algorithm for reconstruction of nonintersecting 3D curves from a sufficiently den se sample. We use the Euclidean minimal spanning trees to identify line segments reconstructing curve shapes. To deal with more than one curve in a sample and to eliminate noisy data, we introduce chains of connected line segments. With the incremental growth based on heuristics, the chains contain finally curve shapes. The method is robust and fast for both 2D and 3D curves. Ključne besede: oblaki točk, rekonstrukcija krivulj, evklidska minimalna vpeta drevesa, point cloud, curve reconstruction, euclidean minimal spanning trees Objavljeno: 10.07.2015; Ogledov: 676; Prenosov: 14 Povezava na celotno besedilo 
6. Navzkrižno testiranje simboličnih in konektivističnih pristopov strojnemu učenju na specializiranih bazah akutnega vnetja slepičaMilan Zorman, Sandi Pohorec, Bojan Butolen, Bojan Žlahtič, Peter Kokol, 2012, izvirni znanstveni članek Ključne besede: acute appendicitis, decision trees, artificial neural networks, machine learning, crosstesting, medica informatics Objavljeno: 30.12.2015; Ogledov: 599; Prenosov: 10 Povezava na celotno besedilo 
7. Treelike isometric subgraphs of hypercubesBoštjan Brešar, Wilfried Imrich, Sandi Klavžar, 2003, izvirni znanstveni članek Opis: Treelike isometric subgraphs of hypercubes, or treelike partial cubes as we call them, are a generalization of median graphs. Just as median graphs they capture numerous properties of trees, but may contain larger classes of graphs that may be easier to recognize than the class of median graphs. We investigate the structure of treelike partial cubes, characterize them, and provide examples of similarities with trees and median graphs. For instance, we show that the cube graph of treelike partial cube is dismantlable. This in particular implies that every treelike partial cube ▫$G$▫ contains a cube that is invariant under every automorphism of ▫$G$▫. We also show that weak retractions preserve treelike partial cubes, which in turn implies that every contraction of a treelike partial cube fixes a cube. The paper ends with several Fruchttype results and a list of open problems. Ključne besede: mathematics, graph theory, Isometric embeddings, partial cubes, expansion procedures, trees, median graphs, graph automorphisms, automorphism groups, dismantlable graphs Objavljeno: 31.03.2017; Ogledov: 531; Prenosov: 203 Celotno besedilo (135,80 KB) Gradivo ima več datotek! Več...

8. Domination game critical graphsCsilla Bujtás, Sandi Klavžar, Gašper Košmrlj, izvirni znanstveni članek Opis: The domination game is played on a graph ▫$G$▫ by two players who alternately take turns by choosing a vertex such that in each turn at least one previously undominated vertex is dominated. The game is over when each vertex becomes dominated. One of the players, namely Dominator, wants to finish the game as soon as possible, while the other one wants to delay the end. The number of turns when Dominator starts the game on ▫$G$▫ and both players play optimally is the graph invariant ▫$\gamma_g(G)$▫, named the game domination number. Here we study the ▫$\gamma_g$▫critical graphs which are critical with respect to vertex predomination. Besides proving some general properties, we characterize ▫$\gamma_g$▫critical graphs with ▫$\gamma_g =2$▫ and with ▫$\gamma_g =3$▫, moreover for each ▫$n$▫ we identify the (infinite) class of all ▫$\gamma_g$▫critical ones among the ▫$n$▫th powers ▫$C_N^n$▫ of cycles. Along the way we determine ▫$\gamma_g(C_N^n)$▫ for all ▫$n$▫ and ▫$N$▫. Results of a computer search for ▫$\gamma_g$▫critical trees are presented and several problems and research directions are also listed. Ključne besede: domination game, domination game critical graphs, powers of cycles, trees Objavljeno: 31.03.2017; Ogledov: 485; Prenosov: 222 Celotno besedilo (194,74 KB) Gradivo ima več datotek! Več...

9. Coopetition effect determinantsJoanna Cygler, Katarzyna Dębkowska, 2015, izvirni znanstveni članek Opis: Background and Goal: The article is aimed at conducting an empirical analysis of the value and significance of coopetitors’ attributes thanks to which coopetition, which is a combination of cooperation and competition between competitors, generates a substantial corporate profit. Four major competitors’ attributes have been analysed: its size, geographical scope, market and technological position. The research also includes the Porter’s value chain.
Design/ Methodology/Approach: The survey has been conducted on a sample of 235 high tech companies operating in Poland and involved in coopetition. The sample is representative. The data have been collected at interviews with company top executives or owners. The research applies the method of classification trees, which, thanks to diagrams, sequentially divides the examined data space into classes (spaces) of similar properties. The assessment of the effect of coopetition, including its variants, made by the examined company served as a dependent qualitative variable. Four coopetitor’s attributes and their variants were assumed as explanatory variables (predictors) affecting the assessment of cooperation.
Results: The results of research indicated the necessity for an accurate competitor’s profile selection. The significance of each of the four attributes may be different depending on the undertaken areas of cooperation with a competitor. The value of all the attributes of competitors is also diverse depending on the area of cooperation. A selected competitor’s profile with regard to the four analysed attributes may become a stimulant to generate benefits in one area, while in another area it may become an inhibitor.
Conclusions: So far, the selection of a coopetition partner has been treated universally, without scrutinizing on some specific needs in relation to the area of cooperation. The selection of an appropriate coopetitor’s profile will allow for the cost reduction in search of appropriate candidates for cooperation and in relations management. Ključne besede: coopetition, effects, competitor’s attributes, classification trees Objavljeno: 29.11.2017; Ogledov: 210; Prenosov: 68 Celotno besedilo (1,04 MB) Gradivo ima več datotek! Več...

10. Radon anomalies in soil gas caused by seismic activityBoris Zmazek, Mladen Živčić, Ljupčo Todorovski, Sašo Džeroski, Janja Vaupotič, Ivan Kobal, 2004, izvirni znanstveni članek Opis: At the Orlica fault in the Krško basin, combined barasol detectors were buried in six boreholes, two along the fault itself and four on either side of it, to measure and record radon activity, temperature and pressure in soil gas every 60 minutes for four years. Data collected have been analysed in a manner aimed at distinguishing radon anomalies resulting from environmental parameters (air and soil temperature, barometric pressure, rainfall) from those caused solely by seismic events. The following approaches have been used to identify anomalies: (i) ± 2σ deviation of radon concentration from the seasonal average, (ii) correlation between time gradients of radon concentration and barometric pressure, and (iii) prediction with regression trees within a machine learning program. In this paper results obtained with regression trees are presented. A model has been built in which the program was taught to predict radon concentration from the data collected during the seismically inactive periods when radon is presumably influenced only by environmental parameters. A correlation coefficient of 0.83 between measured and predicted values was obtained. Then, the whole data time series was included and a significantly lowered correlation was observed during the seismically active periods. This reduced correlation is thus an indicator of seismic effect. Ključne besede: radon in soil gas, environmental parameters, earthquakes, correlation, regression trees, forecasting Objavljeno: 15.05.2018; Ogledov: 342; Prenosov: 23 Celotno besedilo (271,01 KB) Gradivo ima več datotek! Več...
