No Antitwins in Minimal Imperfect Graphs

It is customary to call vertices x and y twins if every vertex distinct from x and y is adjacent either to both of them or to neither of them. By analogy, we shall call vertices x and yantitwins if every vertex distinct from x and y is adjacent to precisely one of them. Lovász proved that no minimal imperfect graph has twins. The purpose of this note is to prove the analogous statement for antitwins

Weak Bipolarizable Graphs

We characterize a new class of perfectly orderable graphs and give a polynomial-time recognition algorithm, together with linear-time optimization algorithms for this class of graphs

The Morphology of Convex Polygons

A simple polygon P is said to be unimodal if for every vertex of P, the Euclidian distance function to the other vertices of P is unimodal. The study of unimodal polygons has emerged as a fruitful area of computational and discrete geometry. We study unimodality properties of a number of special convex polygons from the morphological point of view. In particular, we establish a hierarchy among three classes of convex polygons in terms of their unimodality properties

Wings and Perfect Graphs

An edge uv of a graph G is called a wing if there exists a chordless path with vertices u, v, x, y and edges uv, vx, xy. The wing-graph W(G) of a graph G is a graph having the same vertex set as G; uv is an edge in W(G) if and only if uv is a wing in G. A graph G is saturated if G is isomorphic to W(G). A star-cutset in a graph G is a non-empty set of vertices such that G — C is disconnected and some vertex in C is adjacent to all the remaining vertices in C. V. Chvátal proposed to call a graph unbreakable if neither G nor its complement contain a star-cutset. We establish several properties of unbreakable graphs using the notions of wings and saturation. In particular, we obtain seven equivalent versions of the Strong Perfect Graph Conjecture

Vehicular Crowdsourcing for Congestion Support in Smart Cities

Under present-day practices, the vehicles on our roadways and city streets are mere spectators that witness traffic-related events without being able to participate in the mitigation of their effect. This paper lays the theoretical foundations of a framework for harnessing the on-board computational resources in vehicles stuck in urban congestion in order to assist transportation agencies with preventing or dissipating congestion through large-scale signal re-timing. Our framework is called VACCS: Vehicular Crowdsourcing for Congestion Support in Smart Cities. What makes this framework unique is that we suggest that in such situations the vehicles have the potential to cooperate with various transportation authorities to solve problems that otherwise would either take an inordinate amount of time to solve or cannot be solved for lack for adequate municipal resources. VACCS offers direct benefits to both the driving public and the Smart City. By developing timing plans that respond to current traffic conditions, overall traffic flow will improve, carbon emissions will be reduced, and economic impacts of congestion on citizens and businesses will be lessened. It is expected that drivers will be willing to donate under-utilized on-board computing resources in their vehicles to develop improved signal timing plans in return for the direct benefits of time savings and reduced fuel consumption costs. VACCS allows the Smart City to dynamically respond to traffic conditions while simultaneously reducing investments in the computational resources that would be required for traditional adaptive traffic signal control systems

Some Aspects of the Semi-Perfect Elimination

Several efficient algorithms have been proposed to construct a perfect elimination ordering of the vertices of a chordal graph. We study the behaviour of two of these algorithms in relation to a new concept, namely the semi-perfect elimination ordering, which provides a natural generalization of chordal graphs

The Strong Perfect Graph Conjecture for Pan-Free Graphs

A graph G is perfect if for every induced subgraph F of G, the chromatic number χ(F) equals the largest number ω(F) of pairwise adjacent vertices in F. Berge\u27s famous Strong Perfect Graph Conjecture asserts that a graph G is perfect if and only if neither G nor its complement G contains an odd chordless cycle of length at least five. Its resolution has eluded researchers for more than twenty years. We prove that the conjecture is true for a class of graphs which strictly contains the claw-free graphs

On Sources in Comparability Graphs, With Applications

We characterize sources in comparability graphs and show that our result provides a unifying look at two recent results about interval graphs

A Survey of Enabling Technologies for Smart Communities

In 2016, the Japanese Government publicized an initiative and a call to action for the implementation of a Super Smart Society announced as Society 5.0. The stated goal of Society 5.0 is to meet the various needs of the members of society through the provisioning of goods and services to those who require them, when they are required and in the amount required, thus enabling the citizens to live an active and comfortable life. In spite of its genuine appeal, details of a feasible path to Society 5.0 are conspicuously missing. The first main goal of this survey is to suggest such an implementation path. Specifically, we define a Smart Community as a human-centric entity where technology is used to equip the citizenry with information and services that they can use to inform their decisions. The arbiter of this ecosystem of services is a Marketplace of Services that will reward services aligned with the wants and needs of the citizens, while discouraging the proliferation of those that are not. In the limit, the Smart Community we defined will morph into Society 5.0. At that point, the Marketplace of Services will become a platform for the co-creation of services by a close cooperation between the citizens and their government. The second objective and contribution of this survey paper is to review known technologies that, in our opinion, will play a significant role in the transition to Society 5.0. These technologies will be surveyed in chronological order, as newer technologies often extend old technologies while avoiding their limitations

High-Performance Bus-Based Architectures - Guest Editorial

(First paragrapg) This special issue of VLSI Design presents a collection of seven papers selected out of more than 35 submissions received following the Call for Papers. Each submission was sent to three referees, all of them experts in the area of bus-based architectures. The result is impressive. The papers featured in this Special Issue cover a wide range of topics from sorting to string matching, to load balancing, to simulation, matrix operations, to robotics, to the design of high-performance scalable architectures