19,804 research outputs found

    Link layer multi-priority frame forwarding

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    With increasing demand for multimedia and real-time applications, local area network (LAN) technologies are rapidly being upgraded to support Quality-of-Service (QoS). Many QoS-enabled LANs are making use of resource allocation mechanisms that can discriminate among traffic classes of different priorities. When such LANs are interconnected by bridges to form an extended LAN, it is necessary to upgrade the bridges so that they are QoS-enabled as well. For example, the IEEE 802.1p standard defines a framework for priority queuing in bridges. Alternatively, frame forwarding decisions at the link layer may be modified to recognize frame priorities and alternate paths may be used for differentiating QoS. In this paper, we describe a novel bridge protocol that can forward frames of different priorities using different paths. Our protocol ensures that the forwarding path of a higher priority frame is never longer than the forwarding path of a lower priority frame.published_or_final_versio

    The effect of alkali niobate addition on the phase stability and dielectric properties of Pb (Zn13 Nb23) O3 based ceramic

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    While Pb (Zn13 Nb23) O3 -PbTi O3 (PZN-PT) single crystals have shown superior ferroelectric properties, less scientific and technical interests have been placed on PZN-PT polycrystalline ceramics due to their poor thermodynamic stability and the difficult processing conditions. Here, we stabilized the PZN-PT based ceramics by adding alkali niobates such as NaNb O3 (NN) and KNb O3 (KN) and investigated their structure and dielectric properties. Two stabilization mechanisms are suggested in alkali niobate added PZN-PT ceramics, increased tolerance factor and enhanced electronegativity difference. KN stabilized the perovskite structure of PZN-PT based ceramics more effectively than NN. Both PZN-PT-KN and PZN-PT-NN ceramics showed the typical behavior of relaxor ferroelectrics. The temperature of maximum dielectric constant of PZN-PT-NN was slightly higher than that of the PZN-PT-KN, which was explained by the difference in ionic size and B -site ordering. © 2007 American Institute of Physics

    Perception and Reaction to Floor Impact Noise in Apartment Buildings: A Qualitative Approach

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    This study used grounded theory to understand how apartment building residents perceive and react to floor impact noise from upstairs. In-depth interviews with a heterogeneous group of 14 participants were conducted, and the acquired data were analysed to develop a conceptual model for describing perception and reaction to floor impact noise. It was found that floor impact noise had diverse sources, with the majority originating from footsteps. The participants negatively perceived the noise as annoying and disturbing, and sleep disturbance was reported the most frequently. Cognitive and avoidant coping strategies were initially adopted, and complaints were only thereafter registered if the noise persisted. It was also observed that exposure to the noise led to self-reported health problems and concerns. The developed conceptual model highlights potential intervention measures for controlling noise perception and reactions to floor impact noise

    Spectroscopic Confirmation of a Protocluster at z=3.786

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    We present new observations of the field containing the z=3.786 protocluster, PC217.96+32.3. We confirm that it is one of the largest and most overdense high-redshift structures known. Such structures are rare even in the largest cosmological simulations. We used the Mayall/MOSAIC1.1 imaging camera to image a 1.2x0.6 deg area (~150x75 comoving Mpc) surrounding the protocluster's core and discovered 165 candidate Lyman Alpha emitting galaxies (LAEs) and 788 candidate Lyman Break galaxies (LBGs). There are at least 2 overdense regions traced by the LAEs, the largest of which shows an areal overdensity in its core (i.e., within a radius of 2.5 comoving Mpc) of 14+/-7 relative to the average LAE spatial density in the imaged field. Further, the average LAE spatial density in the imaged field is twice that derived by other field LAE surveys. Spectroscopy with Keck/DEIMOS yielded redshifts for 164 galaxies (79 LAEs and 85 LBGs); 65 lie at a redshift of 3.785+/-0.010. The velocity dispersion of galaxies near the core is 350+/-40 km/s, a value robust to selection effects. The overdensities are likely to collapse into systems with present-day masses of >10^{15} solar masses and >6x10^{14} solar masses. The low velocity dispersion may suggest a dynamically young protocluster. We find a weak trend between narrow-band (Lyman Alpha) luminosity and environmental density: the Lyman Alpha luminosity is enhanced on average by 1.35X within the protocluster core. There is no evidence that the Lyman Alpha equivalent width depends on environment. These suggest that star-formation and/or AGN activity is enhanced in the higher density regions of the structure. PC217.96+32.3 is a Coma cluster analog, witnessed in the process of formation.Comment: Accepted for publication in the Astrophysical Journal (March 27, 2016

    Early developing syntactic knowledge influences sequential statistical learning in infancy

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    Adults\u2019 linguistic background influences their sequential statistical learning of an artificial language characterized by conflicting forward-going and backward-going transitional probabilities. English-speaking adults favor backward-going transitional probabilities, consistent with the head-initial structure of English. Korean-speaking adults favor forward-going transitional probabilities, consistent with the head-final structure of Korean. These experiments assess when infants develop this directional bias. In the experiments, 7-month-old infants showed no bias for forward-going or backward-going regularities. By 13 \u202fmonths, however, English-learning infants favored backward-going transitional probabilities over forward-going transitional probabilities, consistent with English-speaking adults. This indicates that statistical learning rapidly adapts to the predominant syntactic structure of the native language. Such adaptation may facilitate subsequent learning by highlighting statistical structures that are likely to be informative in the native linguistic environment

    Neurosurgery Education in the Medical School Curriculum: A Scoping Review

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    Objective: Despite a high burden of neurosurgical disease that is often assessed, investigated and managed by generalists, to our knowledge, there is no specific medical school curriculum in neurosurgery. This scoping review was carried out to map available evidence pertaining to the provision of neurosurgery education in the medical school curriculum across the world. / Method: This review was conducted in accordance to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis extension for Scoping Reviews. Inclusion criteria were full-text articles published from 1999 onwards, that reported on neurosurgery education in the medical curriculum. / Results: Ten studies were included. Six were from the United Kingdom, two from the United States, and one each from Canada and Ireland. Seven studies reported perceptions of medical students and five reported perceptions of clinicians. Three main themes were identified. Neurosurgery was perceived as an important part of the general medical student curriculum by students and neurosurgeons but less so by medical school deans. Exposure to neurosurgery teaching was varied but when received, deemed useful and students were keen to receive more. Interest in a neurosurgical career amongst surveyed medical students was high. / Conclusions: The limited evidence has demonstrated variability of perceptions about the importance of neurosurgery amongst stakeholders and medical students’ exposure to neurosurgery teaching. Our findings highlight the need to systematically assess specialty-specific teaching and determine adequacy. Stakeholders should include neurosurgeons, medical educators, general practitioners and the variety of specialists that play a crucial role in the management of patients with neurosurgical conditions

    On wireless sensors communication for overhead transmission line monitoring in power delivery systems

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    The transmission of energy is monitored in the smart grid through deploying sensors in all the components, including the overhead transmission lines. There are many poles/towers supporting a long overhead transmission line. Naturally, sensors are deployed on the location close to the poles/towers on each span. Due to the limited transmission range of the wireless transceiver module of a sensor, researchers generally assume that data generated by a sensor have to be delivered to the substation through a set of sensors in-between. This results in a linear network model. In this paper, we first analyze the performance of this model in handling the traffics extracted from an existing testbed. We realize that the linear network model may not be sufficient to support future smart grid applications which may have diversified requirements on data delivery. We then study a new network model in which sensor/relay nodes can also communicate with other nodes using a wide area network such as the cellular network. In this new model, the network formed can be reconfigured based on the application requirements to deliver information to the substations efficiently and effectively.published_or_final_versionThe 1st IEEE International Conference on Smart Grid Communications (SmartGridComm 2010), Gaithersburg, MD., 4-6 October 2010. In Proceedings of the 1st SmartGridComm, 2010, p. 309-31

    DIFFERENCES BETWEEN RADIO-LOUD AND RADIO-QUIET Îł-RAY PULSARS AS REVEALED BY <i>FERMI</i>

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