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Wyniki wyszukiwania dla: 3-UNIFORM HYPERGRAPH,SCHEDULING,EDGE-COLORING
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Edge-coloring of 3-uniform hypergraphs
PublikacjaWe consider edge-colorings of 3-uniform hypergraphs which is a natural generalization of the problem of edge-colorings of graphs. Various classes of hypergraphs are discussed and we make some initial steps to establish the border between polynomial and NP-complete cases. Unfortunately, the problem appears to be computationally difficult even for relatively simple classes of hypergraphs.
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Interval Edge Coloring of Bipartite Graphs with Small Vertex Degrees
PublikacjaAn edge coloring of a graph G is called interval edge coloring if for each v ∈ V(G) the set of colors on edges incident to v forms an interval of integers. A graph G is interval colorable if there is an interval coloring of G. For an interval colorable graph G, by the interval chromatic index of G, denoted by χ'_i(G), we mean the smallest number k such that G is interval colorable with k colors. A bipartite graph G is called (α,β)-biregular...
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Equitable and semi-equitable coloring of cubic graphs and its application in batch scheduling
PublikacjaIn the paper we consider the problems of equitable and semi-equitable coloring of vertices of cubic graphs. We show that in contrast to the equitable coloring, which is easy, the problem of semi-equitable coloring is NP- complete within a broad spectrum of graph parameters. This affects the complexity of batch scheduling of unit-length jobs with cubic incompatibility graph on three uniform processors to minimize...
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Better polynomial algorithms for scheduling unit-length jobs with bipartite incompatibility graphs on uniform machines
PublikacjaThe goal of this paper is to explore and to provide tools for the investigation of the problems of unit-length scheduling of incompatible jobs on uniform machines. We present two new algorithms that are a significant improvement over the known algorithms. The first one is Algorithm 2 which is 2-approximate for the problem Qm|p j = 1, G = bisubquartic|Cmax . The second one is Algorithm 3 which is 4-approximate for the problem Qm|p...
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Scheduling on Uniform and Unrelated Machines with Bipartite Incompatibility Graphs
PublikacjaThe problem of scheduling jobs on parallel machines under an incompatibility relation is considered in this paper. In this model, a binary relation between jobs is given and no two jobs that are in the relation can be scheduled on the same machine. We consider job scheduling under the incompatibility relation modeled by a bipartite graph, under the makespan optimality criterion, on uniform and unrelated machines. Unrelated machines...
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Optimal edge-coloring with edge rate constraints
PublikacjaWe consider the problem of covering the edges of a graph by a sequence of matchings subject to the constraint that each edge e appears in at least a given fraction r(e) of the matchings. Although it can be determined in polynomial time whether such a sequence of matchings exists or not [Grötschel et al., Combinatorica (1981), 169–197], we show that several questions about the length of the sequence are computationally intractable....
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Heuristic scheduling algorithms for uniform load of computer system
PublikacjaW pracy zaprezentowano opracowany heurystyczny algorytm szeregowania zadań UNILO (ang. UNIform LOad - jednakowe obciążenie), umożliwiający redukcję całkowitego zapotrzebowania na moc obliczeniową systemu komputerowego bez pogarszania jego wydajności. Algorytm ten realizuje takie przydzielenie zadań obliczeniowych do poszczególnych jednostek (procesorów), aby zapewnić ich jednakowe obciążenie. Opracowany algorytm został zweryfikowany...
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Scheduling of unit-length jobs with cubic incompatibility graphs on three uniform machines
PublikacjaWe consider the problem of scheduling n identical jobs on 3 uniform machines with speeds s1, s2, and s3 to minimize the schedule length. We assume that jobs are subject to some kind of mutual exclusion constraints, modeled by a cubic incompatibility graph. We how that if the graph is 2-chromatic then the problem can be solved in O(n^2) time. If the graph is 3-chromatic, the problem becomes NP-hard even if s1>s2=s3.
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Scheduling of identical jobs with bipartite incompatibility graphs on uniform machines. Computational experiments
PublikacjaWe consider the problem of scheduling unit-length jobs on three or four uniform parallel machines to minimize the schedule length or total completion time. We assume that the jobs are subject to some types of mutual exclusion constraints, modeled by a bipartite graph of a bounded degree. The edges of the graph correspond to the pairs of jobs that cannot be processed on the same machine. Although the problem is generally NP-hard,...
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Scheduling of unit-length jobs with bipartite incompatibility graphs on four uniform machines
PublikacjaThe problem of scheduling n identical jobs on 4 uniform machines with speeds s1>=s2>=s3>=s4 is considered.The aim is to find a schedule with minimum possible length. We assume that jobs are subject to mutual exclusion constraints modeled by a bipartite incompatibility graph of degree delta. We show that the general problem is NP-hard even if s1=s2=s3. If, however, delta<5 and s1>12s2 s2=s3=s4, then the problem can be solved to...
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Interval Edge-Coloring of Graphs
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Mixed graph edge coloring
PublikacjaW pracy rozważany jest problem kolorowania krawędzi grafu mieszanego, tj. grafu zawierającego zawiero skierowane, jak i nieskierowane krawędzie. Motywację do badań stanowią zagadnienia komunikacyjne z zakresu szeregowania zadań.
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Interval edge-coloring of graphs.
PublikacjaRozdział poświęcony prezentacji modelu zwartego kolorowania krawędziowego grafów i jego znanych własności. Szczególny nacisk położono na opis klas grafów dających się pokolorować zwarcie w czasie wielomianowym. Omówiono także stratność jako miarę niepodatności grafu na kolorowanie zwarte.
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Interval edge coloring of a graph with forbidden colors
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Self-stabilizing algorithm for edge-coloring of graphs
PublikacjaReferat ten poświęcony jest kolorowaniu grafów w modelu rozproszonym.Podano samostabilizujący się algorytm kolorowania krawędzi grafu wraz z dowodem poprawności oraz oszacowaniem jego czasu działania.
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A linear time algorithm for edge coloring of binomial trees
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Edge coloring of graphs of signed class 1 and 2
PublikacjaRecently, Behr (2020) introduced a notion of the chromatic index of signed graphs and proved that for every signed graph (G, σ) it holds that ∆(G) ≤ χ′(G,σ) ≤ ∆(G) + 1, where ∆(G) is the maximum degree of G and χ′ denotes its chromatic index. In general, the chromatic index of (G, σ) depends on both the underlying graph G and the signature σ. In the paper we study graphs G for which χ′(G, σ) does not depend on σ. To this aim we...
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Equitable 4-coloring of cacti and edge-cacti in polynomial time
PublikacjaRozważono problem wyznaczania sprawiedliwej liczby chromatycznej kaktusów i drzew wielokątowych bez trójkątów i krawędzi wiszących. Podano wielomianowy algorytm wyznaczający pokolorowanie optymalne, oparty na paradygmacie programowania dynamicznego. Tym samym znaleziona została kolejna klasa grafów planarnych, dla której kolorowanie sprawiedliwe jawi się jako zagadnienie obliczeniowo łatwe.
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Scheduling with precedence constraints: mixed graph coloring in series-parallel graphs.
PublikacjaW pracy rozważono problem kolorowania grafów mieszanych, opisujący zagadnienie szeregowania zadań, w którym zależności czasowe zadań mają charakter częściowego porządku lub wzajemnego wykluczania. Dla przypadku, w którym graf zależności jest szeregowo-równoległy, podano algorytm rozwiązujący problem optymalnie w czasie $O(n^3.376 * log n)$.
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Equitable and semi-equitable coloring of cubic graphs and its application in batch scheduling
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A graph coloring approach to scheduling of multiprocessor tasks on dedicated machines with availability constraints
PublikacjaWe address a generalization of the classical 1- and 2-processor unit execution time scheduling problem on dedicated machines. In our chromatic model of scheduling machines have non-simultaneous availability times and tasks have arbitrary release times and due dates. Also, the versatility of our approach makes it possible to generalize all known classical criteria of optimality. Under these stipulations we show that the problem...
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Approximating the maximum 2- and 3-edge-colorable subgraph problems
PublikacjaDla ustalonej wartości parametru k>=2, problem maksymalnego podgrafu krawędziowo k-kolorowalnego polega na wskazaniu k rozłącznych skojarzeń w grafie prostym, a kryterium optymalizacji jest maksymalizacja całkowitej liczby użytych krawędzi. W pracy podano algorytmy 5/6- i 4/5-przybliżone odpowiednio dla przypadków k=2 i k=3, poprawiając wyniki znane z literatury.
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Equitable coloring of hypergraphs
PublikacjaA hypergraph is equitablyk-colorable if its vertices can be partitioned into k sets/colorclasses in such a way that monochromatic edges are avoided and the number of verticesin any two color classes differs by at most one. We prove that the problem of equitable 2-coloring of hypergraphs is NP-complete even for 3-uniform hyperstars. Finally, we apply the method of dynamic programming for designing a polynomial-time algorithm to...
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No-Wait & No-Idle Open Shop Minimum Makespan Scheduling with Bioperational Jobs
PublikacjaIn the open shop scheduling with bioperational jobs each job consists of two unit operations with a delay between the end of the first operation and the beginning of the second one. No-wait requirement enforces that the delay between operations is equal to 0. No-idle means that there is no idle time on any machine. We model this problem by the interval incidentor (1, 1)-coloring (IIR(1, 1)-coloring) of a graph with the minimum...
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Independence in uniform linear triangle-free hypergraphs
PublikacjaThe independence number a(H) of a hypergraph H is the maximum cardinality of a set of vertices of H that does not contain an edge of H. Generalizing Shearer’s classical lower bound on the independence number of triangle-free graphs Shearer (1991), and considerably improving recent results of Li and Zang (2006) and Chishti et al. (2014), we show a new lower bound for a(H) for an r-uniform linear triangle-free hypergraph H with r>=2.
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Towards the boundary between easy and hard control problems in multicast Clos networks
PublikacjaIn this article we study 3-stage Clos networks with multicast calls in general and 2-cast calls, in particular. We investigate various sizes of input and output switches and discuss some routing problems involved in blocking states. To express our results in a formal way we introduce a model of hypergraph edge-coloring. A new class of bipartite hypergraphs corresponding to Clos networks is studied. We identify some polynomially...
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A bound on the number of middle-stage crossbars in f-cast rearrangeable Clos networks
PublikacjaIn 2006 Chen and Hwang gave a necessary and sufficient condition under which a three-stage Clos network is rearrangeable for broadcast connections. Assuming that only crossbars of the first stage have no fan-out property, we give similar conditions for f-cast Clos networks, where f is an arbitrary but fixed invariant of the network. Such assumptions are valid for some practical switching systems, e.g. high-speed crossconnects....
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Scheduling of compatible jobs on parallel machines
PublikacjaThe dissertation discusses the problems of scheduling compatible jobs on parallel machines. Some jobs are incompatible, which is modeled as a binary relation on the set of jobs; the relation is often modeled by an incompatibility graph. We consider two models of machines. The first model, more emphasized in the thesis, is a classical model of scheduling, where each machine does one job at time. The second one is a model of p-batching...
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Optimal backbone coloring of split graphs with matching backbones
PublikacjaFor a graph G with a given subgraph H, the backbone coloring is defined as the mapping c: V(G) -> N+ such that |c(u)-c(v)| >= 2 for each edge uv \in E(H) and |c(u)-c(v)| >= 1 for each edge uv \in E(G). The backbone chromatic number BBC(G;H) is the smallest integer k such that there exists a backbone coloring with max c(V(G)) = k. In this paper, we present the algorithm for the backbone coloring of split graphs with matching backbone.
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Scheduling with Complete Multipartite Incompatibility Graph on Parallel Machines: Complexity and Algorithms
PublikacjaIn this paper, the problem of scheduling on parallel machines with a presence of incompatibilities between jobs is considered. The incompatibility relation can be modeled as a complete multipartite graph in which each edge denotes a pair of jobs that cannot be scheduled on the same machine. The paper provides several results concerning schedules, optimal or approximate with respect to the two most popular criteria of optimality:...
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Dynamic coloring of graphs
PublikacjaDynamics is an inherent feature of many real life systems so it is natural to define and investigate the properties of models that reflect their dynamic nature. Dynamic graph colorings can be naturally applied in system modeling, e.g. for scheduling threads of parallel programs, time sharing in wireless networks, session scheduling in high-speed LAN's, channel assignment in WDM optical networks as well as traffic scheduling. In...
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Approximation algorithms for job scheduling with block-type conflict graphs
PublikacjaThe problem of scheduling jobs on parallel machines (identical, uniform, or unrelated), under incompatibility relation modeled as a block graph, under the makespan optimality criterion, is considered in this paper. No two jobs that are in the relation (equivalently in the same block) may be scheduled on the same machine in this model. The presented model stems from a well-established line of research combining scheduling theory...
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Rearrangeability in multicast Clos networks is NP-complete
PublikacjaPrzestrajalność w polach Closa z połączeniami jeden do jeden jest problemem wielomianowym. W pracy pokazano, że w polach z połączeniami jeden do wiele problem ten jest NP zupełny.Three-stage elos networks are commutation networks with circuit switching. So far, graph theory has been very useful tool for solving issues related to these networks with unicast connections. This is so because if elos network is represented as a bipartite...
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The Backbone Coloring Problem for Bipartite Backbones
PublikacjaLet G be a simple graph, H be its spanning subgraph and λ≥2 be an integer. By a λ -backbone coloring of G with backbone H we mean any function c that assigns positive integers to vertices of G in such a way that |c(u)−c(v)|≥1 for each edge uv∈E(G) and |c(u)−c(v)|≥λ for each edge uv∈E(H) . The λ -backbone chromatic number BBCλ(G,H) is the smallest integer k such that there exists a λ -backbone coloring c of G with backbone H satisfying...
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Interval incidence coloring of subcubic graphs
PublikacjaIn this paper we study the problem of interval incidence coloring of subcubic graphs. In [14] the authors proved that the interval incidence 4-coloring problem is polynomially solvable and the interval incidence 5-coloring problem is N P-complete, and they asked if χii(G) ≤ 2∆(G) holds for an arbitrary graph G. In this paper, we prove that an interval incidence 6-coloring always exists for any subcubic graph G with ∆(G) = 3.
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Tight bounds on the complexity of semi-equitable coloring of cubic and subcubic graphs
PublikacjaWe consider the complexity of semi-equitable k-coloring, k>3, of the vertices of a cubic or subcubic graph G. In particular, we show that, given a n-vertex subcubic graph G, it is NP-complete to obtain a semi-equitable k-coloring of G whose non-equitable color class is of size s if s>n/3, and it is polynomially solvable if s, n/3.
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Scheduling with Complete Multipartite Incompatibility Graph on Parallel Machines
PublikacjaIn this paper we consider a problem of job scheduling on parallel machines with a presence of incompatibilities between jobs. The incompatibility relation can be modeled as a complete multipartite graph in which each edge denotes a pair of jobs that cannot be scheduled on the same machine. Our research stems from the works of Bodlaender, Jansen, and Woeginger (1994) and Bodlaender and Jansen (1993). In particular, we pursue the...
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Minimum order of graphs with given coloring parameters
PublikacjaA complete k-coloring of a graph G=(V,E) is an assignment F: V -> {1,...,k} of colors to the vertices such that no two vertices of the same color are adjacent, and the union of any two color classes contains at least one edge. Three extensively investigated graph invariants related to complete colorings are the minimum and maximum number of colors in a complete coloring (chromatic number χ(G) and achromatic number ψ(G), respectively),...
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Equitable coloring of corona multiproducts of graphs
PublikacjaWe give some results regarding the equitable chromatic number for l-corona product of two graphs: G and H, where G is an equitably 3- or 4-colorable graph and H is an r-partite graph, a cycle or a complete graph. Our proofs lead to polynomial algorithms for equitable coloring of such graph products provided that there is given an equitable coloring of G.
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Dynamic F-free Coloring of Graphs
PublikacjaA problem of graph F-free coloring consists in partitioning the vertex set of a graph such that none of the resulting sets induces a graph containing a fixed graph F as an induced subgraph. In this paper we consider dynamic F-free coloring in which, similarly as in online coloring, the graph to be colored is not known in advance; it is gradually revealed to the coloring algorithm that has to color each vertex upon request as well...
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Bounds on the vertex-edge domination number of a tree
PublikacjaA vertex-edge dominating set of a graph $G$ is a set $D$ of vertices of $G$ such that every edge of $G$ is incident with a vertex of $D$ or a vertex adjacent to a vertex of $D$. The vertex-edge domination number of a graph $G$, denoted by $\gamma_{ve}(T)$, is the minimum cardinality of a vertex-edge dominating set of $G$. We prove that for every tree $T$ of order $n \ge 3$ with $l$ leaves and $s$ support vertices we have $(n-l-s+3)/4...
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Computational aspects of greedy partitioning of graphs
PublikacjaIn this paper we consider a variant of graph partitioning consisting in partitioning the vertex set of a graph into the minimum number of sets such that each of them induces a graph in hereditary class of graphs P (the problem is also known as P-coloring). We focus on the computational complexity of several problems related to greedy partitioning. In particular, we show that given a graph G and an integer k deciding if the greedy...
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Energy efficient indoor localisation for narrowband internet of things
PublikacjaThere are an increasing number of Narrow Band IoT devices being manufactured as the technology behind them develops quickly. The high co-channel interference and signal attenuation was seen in edge Narrow Band IoT devices make it challenging to guarantee the service quality of these devices. To maximize the data rate fairness of Narrow Band IoT devices, a multi-dimensional indoor localization model is devised, consisting of...
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T-colorings, divisibility and circular chromatic number
PublikacjaLet T be a T-set, i.e., a finite set of nonnegative integers satisfying 0 ∈ T, and G be a graph. In the paper we study relations between the T-edge spans espT (G) and espd⊙T (G), where d is a positive integer and d ⊙ T = {0 ≤ t ≤ d (max T + 1): d |t ⇒ t/d ∈ T} . We show that espd⊙T (G) = d espT (G) − r, where r, 0 ≤ r ≤ d − 1, is an integer that depends on T and G. Next we focus on the case T = {0} and show that espd⊙{0} (G) =...
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Integration of Services into Workflow Applications
PublikacjaDescribing state-of-the-art solutions in distributed system architectures, Integration of Services into Workflow Applications presents a concise approach to the integration of loosely coupled services into workflow applications. It discusses key challenges related to the integration of distributed systems and proposes solutions, both in terms of theoretical aspects such as models and workflow scheduling algorithms, and technical...
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The computational complexity of the backbone coloring problem for planar graphs with connected backbones
PublikacjaIn the paper we study the computational complexity of the backbone coloring problem for planar graphs with connected backbones. For every possible value of integer parameters λ≥2 and k≥1 we show that the following problem: Instance: A simple planar graph GG, its connected spanning subgraph (backbone) HH. Question: Is there a λ-backbone coloring c of G with backbone H such that maxc(V(G))≤k? is either NP-complete or polynomially...
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Equitable coloring of corona products of graphs
PublikacjaIn this paper we consider an equitable coloring of some corona products of graphs G and H in symbols, G o H). In particular, we show that deciding the colorability of G o H is NP-complete even if G is 4-regular and H is K_2. Next, we prove exact values or upper bounds on the equitable chromatic number of G o H, where G is an equitably 3- or 4-colorable graph and H is an r-partite graph, a path, a cycle or a complete graph.
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Domination subdivision and domination multisubdivision numbers of graphs
PublikacjaThe domination subdivision number sd(G) of a graph G is the minimum number of edges that must be subdivided (where an edge can be subdivided at most once) in order to increase the domination number of G. It has been shown [10] that sd(T)<=3 for any tree T. We prove that the decision problem of the domination subdivision number is NP-complete even for bipartite graphs. For this reason we define the domination multisubdivision number...
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Three-fast-searchable graphs
PublikacjaIn the edge searching problem, searchers move from vertex to vertex in a graph to capture an invisible, fast intruder that may occupy either vertices or edges. Fast searching is a monotonic internal model in which, at every move, a new edge of the graph G must be guaranteed to be free of the intruder. That is, once all searchers are placed the graph G is cleared in exactly |E(G)| moves. Such a restriction obviously necessitates...
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Linear game non-contextuality and Bell inequalities—a graph-theoretic approach
PublikacjaWe study the classical and quantum values of a class of one-and two-party unique games, that generalizes the well-known XOR games to the case of non-binary outcomes. In the bipartite case the generalized XOR(XOR-d) games we study are a subclass of the well-known linear games. We introduce a 'constraint graph' associated to such a game, with the constraints defining the game represented by an edge-coloring of the graph. We use the...
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On Symmetry of Uniform and Preferential Attachment Graphs
PublikacjaMotivated by the problem of graph structure compression under realistic source models, we study the symmetry behavior of preferential and uniform attachment graphs. These are two dynamic models of network growth in which new nodes attach to a constant number m of existing ones according to some attachment scheme. We prove symmetry results for m=1 and 2 , and we conjecture that for m≥3 , both models yield asymmetry with high...
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TOTAL DOMINATION MULTISUBDIVISION NUMBER OF A GRAPH
PublikacjaThe domination multisubdivision number of a nonempty graph G was defined in [3] as the minimum positive integer k such that there exists an edge which must be subdivided k times to increase the domination number of G. Similarly we define the total domination multisubdivision number msd_t (G) of a graph G and we show that for any connected graph G of order at least two, msd_t (G) ≤ 3. We show that for trees the total domination...
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Experimental study of the impact of notches and holes made in the front edge of adherends on the properties of static and fatigue strength of adhesive joints
PublikacjaThe paper presents the results of experimental studies aimed at determining the effect of holes and notches at the front edge of adherends on the strength of adhesive joints. Single-lap joints made of S235JR steel sheets joined with Araldite 2014-2 epoxy adhesive were tested. Comparative tests of static strength in the shear test as well as high-cycle fatigue strength tests were carried out. Joints with three holes with a diameter...
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Mobility Management Solutions for IP Networks Comparative Analysis of IP-based Mobility Protocols and Handover Algorithms Invited Paper
PublikacjaA rapid growth of IP-based networks and services hascreated a vast collection of resources and functionalities availableto users by means of a uniform method of access offered by the IPprotocol. At the same time, advances in the design of mobileelectronic devices allowed them to reach a utility levelcomparable to desktop computers, while still retaining theirmobility advantage. Unfortunately, the base IP protocol does notperform...
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Axial capacity of steel built-up battened columns
PublikacjaThis paper deals with the numerical investigation aimed to study the axial capacity of pin-ended steel built-up columns. Three methods of calculating forces in chords and batten, taking into account the material and geometric imperfections specified in the Eurocode 3 are considered. The aim of this study was to compare different methods allowing the calculation of the column load capacity and determine a simpler and faster method...
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On-line Ramsey Numbers of Paths and Cycles
PublikacjaConsider a game played on the edge set of the infinite clique by two players, Builder and Painter. In each round, Builder chooses an edge and Painter colours it red or blue. Builder wins by creating either a red copy of $G$ or a blue copy of $H$ for some fixed graphs $G$ and $H$. The minimum number of rounds within which Builder can win, assuming both players play perfectly, is the \emph{on-line Ramsey number} $\tilde{r}(G,H)$. In...
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Mitigation of the Flow Maldistribution in Minichannel and Minigap Heat Exchangers by Introducing Threshold in the Manifolds
PublikacjaIn the present paper, a detailed numerical investigation has been carried out to analyze the flow maldistribution in 50 parallel rectangular cross-section (1 mm depth and 1 mm width) minichannels and minigap section (1 mm depth and 99 mm width) with rectangular/trapezoidal manifolds in Z-type flow configuration. The author carried out numerical investigation with various mass flowrates, namely 0.05 kg/s, 0.1 kg/s and 0.2 kg/s which...
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Service time distribution influence on end-to-end call setup delay calculation in networks with Session Initiation Protocol
PublikacjaThe most important GoS parameter for networks with SIP protocol is end-to-end call setup delay. So far there were no coherent models allowing calculation of these parameters for networks with SIP protocol. Few models were developed but they are insufficient. In the paper we propose model which allows end-to-end call setup delay calculation for networks with SIP protocol. The model is using chain of M/G/1/K models and is applicable...
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Graph Decomposition for Memoryless Periodic Exploration
PublikacjaWe consider a general framework in which a memoryless robot periodically explores all the nodes of a connected anonymous graph by following local information available at each vertex. For each vertex v, the endpoints of all edges adjacent to v are assigned unique labels within the range 1 to deg (v) (the degree of v). The generic exploration strategy is implemented using a right-hand-rule transition function: after entering vertex...
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Hybrid P3HT: PCBM/GaN nanowire/Si cascade heterojunction for photovoltaic application
PublikacjaPoly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) are commonly used for the fabrication of organic photovoltaics (OPV). Efficiency limitations of OPVs could be circumvented by incorporation of inorganic nanostructures into organic blends. Again, integration of organic solar cells with well-developed silicon photovoltaic technology is ultimately desirable. In present work, GaN nanowires with diameters...
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Comparative analysis of IP-based mobility protocols and fast handover algorithms in IEEE 802.11 based WLANs
PublikacjaA rapid growth of IP-based networks and services created the vast collection of resources and functionality available to users by means of an uniform method of access - an IP protocol. At the same time, advances in design of mobile electronic devices allowed them to reach utility level comparable to stationary, desktop computers, while still retaining their mobility advantage. Unfortunately, the base IP protocol does not perform...
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Flow Boiling in Minigap in the Reversed Two-Phase Thermosiphon Loop
PublikacjaThe paper presents the results of experimental investigations of a model of a heat exchanger featuring a minigap, which is perceived as an evaporator for an inverted thermosiphon. The system works with a single component test fluid. The tested evaporator generates pumping power in the test loop in a way similar to the mammoth pump. The tests regarded a module of the heat exchanger, consisting of a hot leg and a cold leg with the...
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Fabrication and photoactivity of ionic liquid–TiO2 structures for efficient visible-light-induced photocatalytic decomposition of organic pollutants in aqueous phase
PublikacjaTo investigate the effect of the ionic liquid (IL) chain length on the surface properties and photoactivity of TiO2, a series of TiO2 microspheres have been synthesized via a solvothermal method assisted by 1-methyl-3-octadecylimidazolium chloride ([ODMIM][Cl]) and 1-methyl-3-tetradecylimidazolium chloride ([TDMIM][Cl]). All as-prepared samples were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy...
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A NOTE ON ON-LINE RAMSEY NUMBERS FOR QUADRILATERALS
PublikacjaWe consider on-line Ramsey numbers defined by a game played between two players, Builder and Painter. In each round Builder draws an the edge and Painter colors it either red or blue, as it appears. Builder’s goal is to force Painter to create a monochromatic copy of a fixed graph H in as few rounds as possible. The minimum number of rounds (assuming both players play perfectly) is the on-line Ramsey number \widetilde{r}(H) of...
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Independent Domination Subdivision in Graphs
PublikacjaA set $S$ of vertices in a graph $G$ is a dominating set if every vertex not in $S$ is adjacent to a vertex in~$S$. If, in addition, $S$ is an independent set, then $S$ is an independent dominating set. The independent domination number $i(G)$ of $G$ is the minimum cardinality of an independent dominating set in $G$. The independent domination subdivision number $\sdi(G)$ is the minimum number of edges that must be subdivided (each...
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Novel Coplanar-Strip-Based Excitation Technique for Design of Broadband Circularly Polarization Antennas with Wide 3-dB Axial Ratio Beamwidth
PublikacjaIn this paper, a novel excitation technique for design of a single-point-fed compact low-profile wide-slot antennas with broadband circular polarization (CP) and wide 3 dB axial ratio (AR) beamwidth is presented. Two inverted L-shape parasitic strips placed coplanar to the microstrip line of an asymmetric CPW, and a horizontal strip that protrudes from the vertical edge of the backside ground plane of the substrate are used for...
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Partial Admission Stages of High Efficiency for a Microturbine
PublikacjaThe paper presents the results of a design analysis of a microturbine for a cogeneration micro-power plant working in accordance with organic Rankine cycle. The heat power of the plant is assumed equal to 20kW and the corresponding available electric output is estimated to be about 3 kW. After the design analysis, the axial turbine with partial admission in all stages was built and tested experimentally. Special attentionwas paid...
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Chitosan-based electrospun nanofibers for encapsulating food bioactive ingredients: A review
PublikacjaToday, society has been more aware of healthy food products and related items containing bioactive compounds, which potentially contribute to human health. Unfortunately, the long-term stability and bioactivity of biologically active compounds against environmental factors compromise their target and effective action. In this way, lab-designed vehicles, such as nanoparticles and nanofibers, provide enough properties for their preservation...
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Additive Manufacturing as a Solution to Challenges Associated with Heat Pipe Production
PublikacjaThe aim of this review is to present the recent developments in heat pipe production, which respond to the current technical problems related to the wide implementation of this technology. A novel approach in HP manufacturing is to utilise hi-tech additive manufacturing techniques where the most complicated geometries are fabricated layer-by-layer directly from a digital file. This technology might be a solution to various challenges...
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Measurement report: Spatial variations in ionic chemistry and water-stable isotopes in the snowpack on glaciers across Svalbard during the 2015–2016 snow accumulation season
PublikacjaThe Svalbard archipelago, located at the Arctic sea-ice edge between 74 and 81∘ N, is ∼60 % covered by glaciers. The region experiences rapid variations in atmospheric flow during the snow season (from late September to May) and can be affected by air advected from both lower and higher latitudes, which likely impact the chemical composition of snowfall. While long-term changes in Svalbard snow chemistry have been documented in...
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Enhanced Photoelectrocatalytical Performance of Inorganic-Inorganic Hybrid Consisting BiVO4, V2O5, and Cobalt Hexacyanocobaltate as a Perspective Photoanode for Water Splitting
PublikacjaThin layers of BiVO4/V2O5 were prepared on FTO substrates using pulsed laser deposition technique. The method of cobalt hexacyanocobaltate (Cohcc) synthesis on the BiVO4/V2O5 photoanodes consists of cobalt deposition followed by electrochemical oxidation of metallic Co in K3[Co(CN)6] aqueous electrolyte. The modified electrodes were tested as photoanodes for water oxidation under simulated sunlight irradiation. Deposited films...
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Optical Sensor Based Gestures Inference Using Recurrent Neural Network in Mobile Conditions
PublikacjaIn this paper the implementation of recurrent neural network models for hand gesture recognition on edge devices was performed. The models were trained with 27 hand gestures recorded with the use of a linear optical sensor consisting of 8 photodiodes and 4 LEDs. Different models, trained off-line, were tested in terms of different network topologies (different number of neurons and layers) and different effective sampling frequency...
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Trust Management Method for Wireless Sensor Networks
PublikacjaA Wireless Sensor Network (WSN) is a network of spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. and to cooperatively pass their data to the main location. The first wireless network that bore any real resemblance to a modern WSN is the Sound Surveillance System (SOSUS), developed by the United States Military in the 1950s to detect and track Soviet...
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Biblioteka PG w strukturach ogólnokrajowej sieci bibliotecznej (OSB)
PublikacjaBiblioteka Politechniki Gdańskiej została włączona do ogólnokrajowej sieci bibliotecznej (OSB). Proces rozbudowy OSB opiera się na wdrażaniu działającego w chmurze (cloud computing) systemu bibliotecznego Alma (z wyszukiwarką Primo), używanego przez ponad 3 tysiące bibliotek na świecie. Jest to system biblioteczny nowej generacji działający w oparciu o usługę chmurową typu Multitenant SaaS. Oznacza to, że system biblioteczny...
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Can architecture be 11-dimensional? The nature of space in the architecture of the digital world era
PublikacjaThis research aims to explore the development of architectural theories about ‘architectural dimensions’ and look at architecture as a multidimensional space. It is important to understand that with today's development of virtual reality technology and through the combination of theories of physics and architecture, a new possibility of creating space has emerged. The arguments are made through inductive reasoning and grounded...
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Broadband/Dual-band Metal-Mountable UHF RFID Tag Antennas: A Systematic Review. Taxonomy Analysis, Standards of Seamless RFID System Operation, Supporting IoT implementations, Recommendations and Future Directions
PublikacjaThe employment of broadband/dual-band ultra-high frequency (UHF) radio frequency identification (RFID) tag antennas contributes to the growth of RFID technology, with many potential implications, such as the increase of international trade, and reducing costs thereof. This study presents all reported articles on RFID tags for metal objects that can work seamlessly across different countries. Moreover, it addresses all available...
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Thermal-Resistant Polyurethane/Nanoclay Powder Coatings: Degradation Kinetics Study
PublikacjaIn the present study, thermal degradation kinetics of polyurethane (PU) powder coatings reinforced with organo-modified montmorillonite (OMMT) was investigated. PU nanocomposites were prepared in different concentrations of 1, 3, and 5 wt.% of OMMT via the extrusion method. The microstructure of the nanocomposites was observed by scanning electron microscope (SEM) illustrating uniform dispersion of OMMT nano-clay platelets in the...
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Polyurethanes Crosslinked with Poly(vinyl alcohol) as a Slowly-Degradable and Hydrophilic Materials of Potential Use in Regenerative Medicine
PublikacjaNovel, slowly-degradable and hydrophilic materials with proper mechanical properties and surface characteristics are in great demand within the biomedical field. In this paper, the design, synthesis, and characterization of polyurethanes (PUR) crosslinked with poly(vinyl alcohol) (PVA) as a new proposition for regenerative medicine is described. PVA-crosslinked PURs were synthesized by a two-step polymerization performed in a solvent...
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Global defensive secure structures
PublikacjaLet S ⊂ V (G) for a given simple non-empty graph G. We define for any nonempty subset X of S the predicate SECG,S(X) = true iff |NG[X]∩S| ≥ |NG[X]\S|. Let H be a non-empty family of graphs such that for each vertex v ∈ V (G) there is a subgraph H of G containing v and isomorphic to a member of H. We introduce the concept of H-alliance extending the concept of global defensive secure structures. By an H-alliance in a graph G we...
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Comparative analysis of three‐phase dual active bridge converter with different transformer topology and modern universal control for DC microgrids
PublikacjaThe presented work discusses issues related to the use of modern multiphase topologies of Dual Active Bridge (DAB)-type converters. Converters of this type are widely used in most DC microgrid applications. The introduction emphasizes a comparative analysis between single-phase and multi-phase DAB topologies within high-power DC microgrids, delving into their respective advantages, drawbacks, design procedures, and considerations...
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Computer-Aided Diagnosis of COVID-19 from Chest X-ray Images Using Hybrid-Features and Random Forest Classifier
PublikacjaIn recent years, a lot of attention has been paid to using radiology imaging to automatically find COVID-19. (1) Background: There are now a number of computer-aided diagnostic schemes that help radiologists and doctors perform diagnostic COVID-19 tests quickly, accurately, and consistently. (2) Methods: Using chest X-ray images, this study proposed a cutting-edge scheme for the automatic recognition of COVID-19 and pneumonia....
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Petrophysical analyses of rock construction materials from the Roman rural settlement in Podšilo bay on Rab island (NE Adriatic, Croatia)
PublikacjaThis article presents the results of petrophysical analyses of limestones and sandstones used for the construction of the wall structures of a Roman rural settlement located in Podšilo Bay on Rab Island (Croatia). An on-site analysis of the walls indicated the use of different lithotypes, which is an uncommon case in the area. So far, no petrophysical properties of the applied materials have been tested, and their provenance...
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Highly crystalline colloidal nickel oxide hole transport layer for low-temperature processable perovskite solar cell
PublikacjaHighly crystalline NiOX usually requires high annealing temperature (>300 °C) which is incompatible with flexible substrate and might consume high amount of energy. Herein, we demonstrate a facile emulsion process to synthesize highly crystalline, low temperature deposition (<150 °C) and solution processable NiOx nanoparticles (NPs) as a hole transport layer for the perovskite solar cells (PVSCs)....