Verifying the distributed real-time network protocol RTnet using Uppaal

RTnet is a distributed real-time network protocol for fully-connected local area networks with a broadcast capability. It supports streaming real-time and non-realtime traffic and on-the-fly addition and removal of network nodes. This paper presents a formal analysis of RTnet using the model checker Uppaal. Besides normal protocol behaviour, the analysis focuses on the fault-handling properties of RTnet, in particular recovery after packet loss. Both qualitative and quantitative properties are presented, together with the verification results and conclusions about the robustness of RTnet

Scheduling of Early Quantum Tasks

An Early Quantum Task (EQT) is a Quantum EDF task that has shrunk its first period into one quantum time slot. Its purpose is to be executed as soon as possible, without causing deadline overflow of other tasks. We will derive the conditions under which an EQT can be admitted and can have an immediate start. The advantage of scheduling EQTs is shown by its use in a buffered multi-media server. The EQT is associated with a multimedia stream and it will use its first invocation to fill the buffer, such that a client can start receiving data immediately

RTnet: a real-time protocol for broadcast-capable networks

This paper presents an overview of a real-time network protocol, meant to be used on fully-connected local area networks with a broadcast capability. The intended use of this protocol is an in-home digital network, with support for on-the-fly addition and removal of network nodes, for resource-lavish and resource-lean devices, and for multimedia, command and control and regular data traffic. Both the design and the operation are presented, together with results from measurements on a prototype of the protocol on top of Ethernet

Experimental implementation of a real-time token-based network protocol on a microcontroller

The real-time token-based RTnet network protocol has been implemented on a standard Ethernet network to investigate the possibility to use cheap components with strict resource limitations while preserving Quality of Service guarantees. It will be shown that the proposed implementation is feasible on a small network. For larger networks a different approach is necessary, using delegation by means of proxies. A delegation proposal will be discussed. For small networks it is possible to use a PIC microcontroller in combination with a standard Ethernet controller to run the RTnet network protocol. As more systems are added to the network the performance of this combination becomes insufficient. When this happens it is necessary for the microcontroller to delegate some tasks to a more powerful master and to organize a low-level communication protocol between master and slave

A high frequency optical trap for atoms using Hermite-Gaussian beams

We present an experimental method to create a single high frequency optical trap for atoms based on an elongated Hermite-Gaussian TEM01 mode beam. This trap results in confinement strength similar to that which may be obtained in an optical lattice. We discuss an optical setup to produce the trapping beam and then detail a method to load a Bose-Einstein Condensate (BEC) into a TEM01 trap. Using this method, we have succeeded in producing individual highly confined lower dimensional condensates.Comment: 9 pages, 5 figure

Fast Shocks From Magnetic Reconnection Outflows

Magnetic reconnection is commonly perceived to drive flow and particle acceleration in flares of solar, stellar, and astrophysical disk coronae but the relative roles of different acceleration mecha- nisms in a given reconnection environment are not well understood. We show via direct numerical simulations that reconnection outflows produce weak fast shocks, when conditions for fast recon- nection are met and the outflows encounter an obstacle. The associated compression ratios lead to a Fermi acceleration particle spectrum that is significantly steeper than the strong fast shocks commonly studied, but consistent with the demands of solar flares. While this is not the only acceleration mechanism operating in a reconnection environment, it is plausibly a ubiquitous one

Discontinuities without discontinuity: The Weakly-enforced Slip Method

Tectonic faults are commonly modelled as Volterra or Somigliana dislocations in an elastic medium. Various solution methods exist for this problem. However, the methods used in practice are often limiting, motivated by reasons of computational efficiency rather than geophysical accuracy. A typical geophysical application involves inverse problems for which many different fault configurations need to be examined, each adding to the computational load. In practice, this precludes conventional finite-element methods, which suffer a large computational overhead on account of geometric changes. This paper presents a new non-conforming finite-element method based on weak imposition of the displacement discontinuity. The weak imposition of the discontinuity enables the application of approximation spaces that are independent of the dislocation geometry, thus enabling optimal reuse of computational components. Such reuse of computational components renders finite-element modeling a viable option for inverse problems in geophysical applications. A detailed analysis of the approximation properties of the new formulation is provided. The analysis is supported by numerical experiments in 2D and 3D.Comment: Submitted for publication in CMAM

The Second Triennial Systematic Literature Review of European Nursing Research: Impact on Patient Outcomes and Implications for Evidence-Based Practice

This is the final version. Available from Wiley via the DOI in this record. Background: European research in nursing has been criticized as overwhelmingly descriptive, wasteful and with little relevance to clinical practice. This second triennial review follows our previous review of articles published in 2010, to determine whether the situation has changed. Objective: To identify, appraise, and synthesize reports of European nursing research published during 2013 in the top 20 nursing research journals. Methods: Systematic review with descriptive results synthesis. Results: We identified 2,220 reports, of which 254, from 19 European countries, were eligible for analysis; 215 (84.7%) were primary research, 36 (14.2%) secondary research, and three (1.2%) mixed primary and secondary. Forty-eight (18.9%) of studies were experimental: 24 (9.4%) randomized controlled trials, 11 (4.3%) experiments without randomization, and 13 (5.1%) experiments without control group. A total of 106 (41.7%) articles were observational: 85 (33.5%) qualitative research. The majority (158; 62.2%) were from outpatient and secondary care hospital settings. One hundred and sixty-five (65.0%) articles reported nursing intervention studies: 77 (30.3%) independent interventions, 77 (30.3%) interdependent, and 11 (4.3%) dependent. This represents a slight increase in experimental studies compared with our previous review (18.9% vs. 11.7%). The quality of reporting remained very poor. Linking Evidence to Action: European research in nursing remains overwhelmingly descriptive. We call on nursing researchers globally to raise the level of evidence and, therefore, the quality of care and patient outcomes. We urge them to replicate our study in their regions, diagnose reasons for the lack of appropriate research, identify solutions, and implement a deliberate, targeted, and systematic global effort to increase the number of experimental, high quality, and relevant studies into nursing interventions. We also call on journal editors to mandate an improvement in the standards of research reporting in nursing journals

Algorithmic Randomness and Capacity of Closed Sets

We investigate the connection between measure, capacity and algorithmic randomness for the space of closed sets. For any computable measure m, a computable capacity T may be defined by letting T(Q) be the measure of the family of closed sets K which have nonempty intersection with Q. We prove an effective version of Choquet's capacity theorem by showing that every computable capacity may be obtained from a computable measure in this way. We establish conditions on the measure m that characterize when the capacity of an m-random closed set equals zero. This includes new results in classical probability theory as well as results for algorithmic randomness. For certain computable measures, we construct effectively closed sets with positive capacity and with Lebesgue measure zero. We show that for computable measures, a real q is upper semi-computable if and only if there is an effectively closed set with capacity q