Using Battery Level as Metric for Graph Planarization

International audienceTopology control in wireless sensor networks is an important issue for scalability and energy efficiency. It is often based on graph reduction performed through the use of Gabriel Graph or Relative Neighborhood Graph. This graph reduction is usually based on geometric values. In this paper we tackle the problem of possible connectivity loss in the reduced graph by applying a battery level based reduction graph. Experiments are conducted to evaluate our proposition. Results are compared with RNG reduction which takes into account only the strength of the received signal (RSSI). Results show that our algorithm maintains network connectivity longer than solutions from the literature and balances the energy consumption over nodes

Points of Interest Coverage with Connectivity Constraints using Wireless Mobile Sensors

Part 7: Network Topology ConfigurationInternational audienceThe coverage of Points of Interest (PoI) is a classical requirement in mobile wireless sensor applications. Optimizing the sensors self-deployment over a PoI while maintaining the connectivity between the sensors and the sink is thus a fundamental issue. This article addresses the problem of autonomous deployment o f mobile sensors that need to cover a predefined PoI with a connectivity constraints and provides the solution to it using Relative Neighborhood Graphs (RNG). Our deployment scheme minimizes the number of sensors used for connectivity thus increasing the number of monitoring sensors. Analytical results, simulation results and real implementation are provided to show the efficiency of our algorithm

Planar subgraphs without low-degree nodes

We study the following problem: given a geometric graph G and an integer k, determine if G has a planar spanning subgraph (with the original embedding and straight-line edges) such that all nodes have degree at least k. If G is a unit disk graph, the problem is trivial to solve for k = 1. We show that even the slightest deviation from the trivial case (e.g., quasi unit disk graphs or k = 1) leads to NP-hard problems.Peer reviewe

Quadratic-time, linear-space algorithms for generating orthogonal polygons with a given number of vertices

Programa de Financiamento Plurianual, Fundação para a Ciéncia e TecnologiaPrograma POSIPrograma POCTI, FCTFondo Europeo de Desarrollo Regiona

Reaction Front in an A+B -> C Reaction-Subdiffusion Process

We study the reaction front for the process A+B -> C in which the reagents move subdiffusively. Our theoretical description is based on a fractional reaction-subdiffusion equation in which both the motion and the reaction terms are affected by the subdiffusive character of the process. We design numerical simulations to check our theoretical results, describing the simulations in some detail because the rules necessarily differ in important respects from those used in diffusive processes. Comparisons between theory and simulations are on the whole favorable, with the most difficult quantities to capture being those that involve very small numbers of particles. In particular, we analyze the total number of product particles, the width of the depletion zone, the production profile of product and its width, as well as the reactant concentrations at the center of the reaction zone, all as a function of time. We also analyze the shape of the product profile as a function of time, in particular its unusual behavior at the center of the reaction zone

Trust within illegal online trading. A case study of the Silk Road marketplace

Den kriminella världen har sedan länge använt internet som plattform för att bedriva illegal verksamhet. På detta dark web huserar illegala sidor som med hjälp av robusta tekniska skyddsbarriärer fått ett allt större fotfäste och utgör en svår utmaning för samhället. Silk Road är det mest omtalade exemplet, en framgångsrik droghandel som bedriver sin verksamhet enligt konventionella e-handelskoncept. Denna uppsats kartlägger vilka mekanismer som underbygger verksamheter av den här typen genom att främst fokusera på användarna och deras beteenden. Uppsatsen utgår från tillit som kritisk faktor och applicerar befintlig teori om e-handel och virtual community på dark web. En netnografisk studie genomfördes av Silk Roads diskussionsforum för att identifiera gemensamma nämnare för tillit. Studien genomfördes som en icke-deltagande observation med en explorativ ansats. De tematiska beskrivningarna gemenskap, integritet, mellanhänder, betalning och transport används för att kartlägga de viktigaste tillitssituationerna och visar på att hög kontroll och låg ovisshet är de avgörande determinanter för en fungerade tillit. Tidigare forskning av illegal näthandel fokuserar i stor grad på teknik, varför det behövs fler användarfokuserade studier av denna typ.Since the beginning of the internet the criminal world has used the medium as a platform for operation. This dark web is a domain where illegal sites are flourishing due to the possibilities offered by new technology. Net-based criminal activity is a challenge for society as it uses hard proof technological safety measures to avoid the law. Silk Road is the most prominent example, an online illicit marketplace where drugs and illegal substances are being traded based on conventional e-commerce concepts. This paper argues for trust as an important factor for the survival of illicit online trade and applies existing theories on e-commerce and virtual communities. To identify patterns of trust and common trust-based issues among Silk Road users, a netnographic study was conducted on the site’s discussion forum. This explorative examination focuses on recurring topics and presents its findings through trust-specific themes. The study describes solidarity, integrity, intermediaries, payment and transport as important trust dependent situations and concludes that high control and low uncertainty are the common denominators. Previous studies on online illicit trade focuses mainly on the technical aspects, more user-centered research of this type is therefore needed. This paper is written in Swedish. Keywords: Trust, virtual communities, e-commerce, dark web, Silk Roa