RTXP : A Localized Real-Time Mac-Routing Protocol for Wireless Sensor Networks

Protocols developed during the last years for Wireless Sensor Networks (WSNs) are mainly focused on energy efficiency and autonomous mechanisms (e.g. self-organization, self-configuration, etc). Nevertheless, with new WSN applications, appear new QoS requirements such as time constraints. Real-time applications require the packets to be delivered before a known time bound which depends on the application requirements. We particularly focus on applications which consist in alarms sent to the sink node. We propose Real-Time X-layer Protocol (RTXP), a real-time communication protocol. To the best of our knowledge, RTXP is the first MAC and routing real-time communication protocol that is not centralized, but instead relies only on local information. The solution is cross-layer (X-layer) because it allows to control the delays due to MAC and Routing layers interactions. RTXP uses a suited hop-count-based Virtual Coordinate System which allows deterministic medium access and forwarder selection. In this paper we describe the protocol mechanisms. We give theoretical bound on the end-to-end delay and the capacity of the protocol. Intensive simulation results confirm the theoretical predictions and allow to compare with a real-time centralized solution. RTXP is also simulated under harsh radio channel, in this case the radio link introduces probabilistic behavior. Nevertheless, we show that RTXP it performs better than a non-deterministic solution. It thus advocates for the usefulness of designing real-time (deterministic) protocols even for highly unreliable networks such as WSNs

Négation, interrogation et accord spécificateur-tête

Dans cet article, je propose, dans un premier temps, des explications concernant certaines asymétries entre constructions négatives et constructions interrogatives qui paraissent problématiques pour les différentes analyses qui préconiseraient le déplacement des quantificateurs négatifs en Forme Logique, réaffermissant ainsi la proposition de plusieurs chercheurs à l’effet qu’il existe un parallèle étroit entre constructions interrogatives et constructions négatives. Ceci m’amènera, dans un deuxième temps, à traiter des phrases négatives à interprétation écho. Nous verrons que ces constructions ont des propriétés syntaxiques et distributionnelles semblables à celles des questions écho, parmi lesquelles on compte la propriété de pouvoir contenir le quantificateur dans des positions qui sont généralement réfractaires au déplacement.In this article, I begin by proposing an account of some apparent asymmetries between interrogative and negative constructions which appear, at first sight, problematic for movement analyses of sentence negation, therefore allowing us to retain the widely accepted view that there is a parallel between the two types of constructions. This will lead me to discuss a lesser known variety of negative sentences, i.e. echo negative sentences. It will be shown that these constructions share a number of syntactic and distributional properties with echo wh-questions, among which the ability to allow quantifiers to appear in contexts which generally block overt movement

Life Satisfaction: Measurement Invariance and Correlations with Adolescent Adjustment

Background Low life satisfaction during adolescence has been associated with adjustment problems. There are few well-validated measures available to assess adolescents’ life-satisfaction. The purpose of this study was to investigate the structure of the Life Satisfaction Scale, evaluate its measurement invariance across sex and race/ethnicity, and investigate its associations with related constructs. Methods Participants were 3,340 adolescents from rural middle schools in Florida. Half the participants were female, 51% were White, 15% were Black, and 22% were Latinx. Adolescents completed the Life Satisfaction Scale, the Children’s Report of Exposure to Violence scale, and the Problem Behavior Frequency Scale. Results Confirmatory factor analysis found support for a single factor representing overall life satisfaction, and strong measurement invariance across race, but not across sex. There were significant differences in item thresholds such that girls at the same level of life satisfaction as boys, were more likely to endorse higher responses to items assessing satisfaction with school, with themselves, and with their friendships. Life satisfaction had significant negative correlations with violence exposure, problem behavior, and peer pressure for drug use. Conclusion Findings suggest that the Life Satisfaction Scale may be suitable for assessing life satisfaction across different groups of adolescents. Examining sex differences must be done cautiously as life satisfaction may have different meanings to boys and girls. The inverse correlations between life satisfaction, violence exposure and problem behavior across groups highlights the importance of developing sound measures to assess this important construct and determine how it relates to youth adjustment.https://scholarscompass.vcu.edu/gradposters/1076/thumbnail.jp