PACE: Simple Multi-hop Scheduling for Single-radio 802.11-based Stub Wireless Mesh Networks

IEEE 802.11-based Stub Wireless Mesh Networks (WMNs) are a cost-effective and flexible solution to extend wired network infrastructures. Yet, they suffer from two major problems: inefficiency and unfairness. A number of approaches have been proposed to tackle these problems, but they are too restrictive, highly complex, or require time synchronization and modifications to the IEEE 802.11 MAC. PACE is a simple multi-hop scheduling mechanism for Stub WMNs overlaid on the IEEE 802.11 MAC that jointly addresses the inefficiency and unfairness problems. It limits transmissions to a single mesh node at each time and ensures that each node has the opportunity to transmit a packet in each network-wide transmission round. Simulation results demonstrate that PACE can achieve optimal network capacity utilization and greatly outperforms state of the art CSMA/CA-based solutions as far as goodput, delay, and fairness are concerned

Multicast traffic aggregation in MPLS-based VPN networks

This article gives an overview of the current practical approaches under study for a scalable implementation of multicast in layer 2 and 3 VPNs over an IP-MPLS multiservice network. These proposals are based on a well-known technique: the aggregation of traffic into shared trees to manage the forwarding state vs. bandwidth saving trade-off. This sort of traffic engineering mechanism requires methods to estimate the resources needed to set up a multicast shared tree for a set of VPNs. The methodology proposed in this article consists of studying the effect of aggregation obtained by random shared tree allocation on a reference model of a representative network scenario.Publicad

Do Balance Demands Induce Shifts in Visual Proprioception in Crawling Infants?

The onset of hands-and-knees crawling during the latter half of the first year of life heralds pervasive changes in a range of psychological functions. Chief among these changes is a clear shift in visual proprioception, evident in the way infants use patterns of optic flow in the peripheral field of view to regulate their postural sway. This shift is thought to result from consistent exposure in the newly crawling infant to different patterns of optic flow in the central field of view and the periphery and the need to concurrently process information about self-movement, particularly postural sway, and the environmental layout during crawling. Researchers have hypothesized that the demands on the infant's visual system to concurrently process information about self-movement and the environment press the infant to differentiate and functionalize peripheral optic flow for the control of balance during locomotion so that the central field of view is freed to engage in steering and monitoring the surface and potentially other tasks. In the current experiment, we tested whether belly crawling, a mode of locomotion that places negligible demands on the control of balance, leads to the same changes in the functional utilization of peripheral optic flow for the control of postural sway as hands-and-knees crawling. We hypothesized that hands-and-knees crawlers (n = 15) would show significantly higher postural responsiveness to movements of the side walls and ceiling of a moving room than same-aged pre-crawlers (n = 19) and belly crawlers (n = 15) with an equivalent amount of crawling experience. Planned comparisons confirmed the hypothesis. Visual-postural coupling in the hands-and-knees crawlers was significantly higher than in the belly crawlers and pre-crawlers. These findings suggest that the balance demands associated with hands-and-knees crawling may be an important contributor to the changes in visual proprioception that have been demonstrated in several experiments to follow hands-and-knees crawling experience. However, we also consider that belly crawling may have less potent effects on visual proprioception because it is an effortful and attention-demanding mode of locomotion, thus leaving less attentional capacity available to notice changing relations between the self and the environment

Non-perturbative running of quark masses in three-flavour QCD

We present our preliminary results for the computation of the non-perturbative running of renormalized quark masses in $N_f = 3$ QCD, between the electroweak and hadronic scales, using standard finite-size scaling techniques. The computation is carried out to very high precision, using massless $\mathcal{O}(a)$-improved Wilson quarks. Following the strategy adopted by the ALPHA Collaboration for the running coupling, different schemes are used above and below a scale $\mu_0 \sim m_b$, which differ by using either the Schr\"odinger Functional or Gradient Flow renormalized coupling. We discuss our results for the running in both regions, and the procedure to match the two schemes.Comment: 7 pages, 3 figures, 34th annual International Symposium on Lattice Field Theor

Non-perturbative quark mass renormalisation and running in Nf=3N_f=3 QCD

We determine from first principles the quark mass anomalous dimension in Nf=3 QCD between the electroweak and hadronic scales. This allows for a fully non-perturbative connection of the perturbative and non-perturbative regimes of the Standard Model in the hadronic sector. The computation is carried out to high accuracy, employing massless O(a)-improved Wilson quarks and finite-size scaling techniques. We also provide the matching factors required in the renormalisation of light quark masses from lattice computations with O(a)-improved Wilson fermions and a tree-level Symanzik improved gauge action. The total uncertainty due to renormalisation and running in the determination of light quark masses in the SM is thus reduced to about 1%.Comment: 41 pages, 10 tables, 7 figures, published version (minimal text improvements

Convergence: How Five Trends Will Reshape the Social Sector

This report highlights five key trends and how their coming together will shape the social sector of the future. Based on extensive review of existing research and in-depth interviews with thought leaders and nonprofit leaders and activists, it explores the trends (Demographic Shifts; Technological Advances; Networks Enabling Work to be Organized in New Ways; Rising Interest in Civic Engagement and Volunteerism; and Blurring of Sector Boundaries) and looks at the ways nonprofits can successfully navigate the changes. The monograph is by La Piana Consulting, a national firm dedicated to strengthening nonprofits and foundations

Signalling in voice over IP Networks

Voice signalling protocols have evolved, keeping with the prevalent move from circuit to packet switched networks. Standardization bodies have provided solutions for carrying voice traffic over packet networks while the main manufacturers are already providing products in workgroup, enterprise, or operator portfolio. This trend will accrue in next years due to the evolution of UMTS mobile networks to an “all-IP” environment. In this paper we present the various architectures that are proposed for signalling in VoIP, mainly: H.323, SIP and MGCP. We also include a brief summary about signalling in classical telephone networks and, at the end, we give some ideas about the proposed “all-IP” architectures in UMTS 3G mobile networks.Publicad

Dades preliminars sobre la població de Mauremys leprosa (Testudines: Geoemydidae) d'Alcoi (Alacant)

Es proporcionen dades sobre les característiques morfomètriques i l'estructura d'una població detortuga d'aigua ibèrica (Mauremys leprosa) del riu Serpis al seu pas per Alcoi, SE d'Espanya, una zonaon pràcticament no consta informació prèvia sobre l'espècie. Entre setembre i octubre de 2014 escapturaren 18 individus. La raó de sexes no era equilibrada, en estar molt esbiaixada vers els mascles(4.5:1). El percentatge d'individus juvenils és menor que el d'adults. Les femelles assolixen una midamitjana més gran que els mascles. Es calcula que la població pot estar formada per 64 exemplars.Preliminary data on the Mauremys leprosa (Testudines: Geoemydidae) populationfrom Alcoi (Alacant)We provide data on the morphometric characteristics and structure of a population of the stripeneckedterrapin (Mauremys leprosa) from the Serpis river (Alcoi, SE Spain), an area where barely anyprevious information for the species exists. 18 individuals were captured between September 2014 andOctober 2014. The ratio of sexes was not even and males outnumbered females (4.5:1). The percentageof juveniles was less than that of adults. Females reached a greater average size than males. We calculatethat the total population is made up of 64 individuals

Determinació experimental del camp magnètic terrestre

La majoria de la gent -i els nostres alumnes també- sap que una brúixola s'orienta vers el nord o que els pols iguals dels imants es repel·leixen i els distints s'atrauen, però sovint poca cosa més. Amb les experiències que mostrem es pretén aprofundir en aquests fenòmens per comprendre un poc millor quina és la física que s'hi amaga darrere

Actitud de docentes de matemática de secundaria hacia estudiantes talentosos en matemática

El presente trabajo se centra en el estudio de las actitudes de los docentes de matemática de secundaria de los cantones de Barva, Heredia y Santo Domingo de Heredia hacia estudiantes talentosos en matemática. La investigación realizada fue de tipo cuantitativa con un alcance descriptivo. A los datos obtenidos por medio de un instrumento de medición de actitudes hacia estudiantes talentosos en matemática, se les aplicó el test de Mann Whitney U para el contraste de las hipótesis. Se concluyó que, en general, los docentes de los cantones mencionados no tienen una posición definida en su actitud hacia estudiantes talentosos en matemática, sin embargo mostraron actitudes muy favorables hacia la identificación y atención de estos alumnos