198 research outputs found

    End-to-End Joint Antenna Selection Strategy and Distributed Compress and Forward Strategy for Relay Channels

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    Multi-hop relay channels use multiple relay stages, each with multiple relay nodes, to facilitate communication between a source and destination. Previously, distributed space-time codes were proposed to maximize the achievable diversity-multiplexing tradeoff, however, they fail to achieve all the points of the optimal diversity-multiplexing tradeoff. In the presence of a low-rate feedback link from the destination to each relay stage and the source, this paper proposes an end-to-end antenna selection (EEAS) strategy as an alternative to distributed space-time codes. The EEAS strategy uses a subset of antennas of each relay stage for transmission of the source signal to the destination with amplify and forwarding at each relay stage. The subsets are chosen such that they maximize the end-to-end mutual information at the destination. The EEAS strategy achieves the corner points of the optimal diversity-multiplexing tradeoff (corresponding to maximum diversity gain and maximum multiplexing gain) and achieves better diversity gain at intermediate values of multiplexing gain, versus the best known distributed space-time coding strategies. A distributed compress and forward (CF) strategy is also proposed to achieve all points of the optimal diversity-multiplexing tradeoff for a two-hop relay channel with multiple relay nodes.Comment: Accepted for publication in the special issue on cooperative communication in the Eurasip Journal on Wireless Communication and Networkin

    Small business survey: linking 2006 and 2007 waves to the IDBR

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    This report describes work to link two waves of the Small Business Survey (SBS) to the Inter-Departmental Business Register (IDBR)1. The first is the Annual Small Business Survey 2006/07, hereafter SBS 2006; the second is the survey for 2007/8, hereafter SBS 2007. The linking work has been undertaken by Belmana and Middlesex University; IFF Research conducted both surveys and has overseen this work. The focus of this research was to understand the strengths and weaknesses of different methods of linking and then develop an approach for application to the 2006 and 2007 waves of the survey. A particular difficulty, as older waves of SBS are linked to the IDBR, is the changes to businesses that would have occurred since the survey. This work has taken steps to reduce the effect of the age of the survey on the quality of the data linking, by linking to historic vintages of the IDBR and the Companies House register. The report also reviews earlier work by the Office for National Statistics (ONS) linking the 2010 and 2012 SBS surveys to the IDBR. The project draws on insights from this, but introduces new linking methods that improve link rates. Various quality checks have been undertaken and, given the surveys were conducted almost a decade ago, the ability to link a higher proportion of respondents to the IDBR than achieved for the 2010 survey indicates the linking of SBS can be undertaken even for relatively old waves. Some preliminary analysis of the linked survey data suggests that there is potential for understanding the more long-term outcomes for businesses and correlating these with SBS responses

    Optimal WiFi Sensing via Dynamic Programming

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    The problem of finding an optimal sensing schedule for a mobile device that encounters an intermittent WiFi access opportunity is considered. At any given time, the WiFi is in any of the two modes, ON or OFF, and the mobile's incentive is to connect to the WiFi in the ON mode as soon as possible, while spending as little sensing energy. We introduce a dynamic programming framework which enables the characterization of an explicit solution for several models, particularly when the OFF periods are exponentially distributed. While the problem for non-exponential OFF periods is ill-posed in general, a usual workaround in literature is to make the mobile device aware if one ON period is completely missed. In this restricted setting, using the DP framework, the deterministic nature of the optimal sensing policy is established, and value iterations are shown to converge to the optimal solution. Finally, we address the blind situation where the distributions of ON and OFF periods are unknown. A continuous bandit based learning algorithm that has vanishing regret (loss compared to the optimal strategy with the knowledge of distributions) is presented, and comparisons with the optimal schemes are provided for exponential ON and OFF times

    Ayurvedic Management of Acute Cerebrovascular Accident – A Case Study

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    Cerebro vascular accident (CVA) is the third leading cause of death in developing countries. This disease has posed a great problem to the medical field as far as its treatment is concerned. Ayurveda can offer a lot in such conditions. This is a case study of an acute CVA. An acute CVA case was admitted on 23/05/2016 at 7.30 pm, with the complaints of loss of strength in the right side of the body, loss of speech, drowsiness since 2 days. On examination Glasgowcoma scale was 8/15 (E - 2, M- 1, V-2). Investigation i.e., Computed Tomography (CT) scan of head showed on 24/05/2016: Lacunar infarcts in the Right Frontal White matter and in the Pons at the Midline. It was diagnosed as Pitta Kapha Avruta Vataja Pakshaghata (Vaama). In this case various treatment procedures like cold water pouring over forehead, application of medicated paste on anterior frontanallae, application of Shathadhouta Ghrutha all over the body, nasal instillation etc. with oral medicines were adopted at various condition of the disease. There was a remarkable improvement in the subjective and objective clinical features

    Comparison of two-phase pipe flow in openFOAM with a mechanistic model

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    Two-phase pipe flow is a common occurrence in many industrial applications such as power generation and oil and gas transportation. Accurate prediction of liquid holdup and pressure drop is of vast importance to ensure effective design and operation of fluid transport systems. In this paper, a Computational Fluid Dynamics (CFD) study of a two-phase flow of air and water is performed using OpenFOAM. The two-phase solver, interFoam is used to identify flow patterns and generate values of liquid holdup and pressure drop, which are compared to results obtained from a two-phase mechanistic model developed by Petalas and Aziz (2002). A total of 60 simulations have been performed at three separate pipe inclinations of 0°, +10° and -10° respectively. A three dimensional, 0.052m diameter pipe of 4m length is used with the Shear Stress Transport (SST) k - turbulence model to solve the turbulent mixtures of air and water. Results show that the flow pattern behaviour and numerical values of liquid holdup and pressure drop compare reasonably well to the mechanistic model

    Histone methyltransferase Dot1 and Rad9 inhibit single-stranded DNA accumulation at DSBs and uncapped telomeres

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    Cells respond to DNA double-strand breaks (DSBs) and uncapped telomeres by recruiting checkpoint and repair factors to the site of lesions. Single-stranded DNA (ssDNA) is an important intermediate in the repair of DSBs and is produced also at uncapped telomeres. Here, we provide evidence that binding of the checkpoint protein Rad9, through its Tudor domain, to methylated histone H3-K79 inhibits resection at DSBs and uncapped telomeres. Loss of DOT1 or mutations in RAD9 influence a Rad50-dependent nuclease, leading to more rapid accumulation of ssDNA, and faster activation of the critical checkpoint kinase, Mec1. Moreover, deletion of RAD9 or DOT1 partially bypasses the requirement for CDK1 in DSB resection. Interestingly, Dot1 contributes to checkpoint activation in response to low levels of telomere uncapping but is not essential with high levels of uncapping. We suggest that both Rad9 and histone H3 methylation allow transmission of the damage signal to checkpoint kinases, and keep resection of damaged DNA under control influencing, both positively and negatively, checkpoint cascades and contributing to a tightly controlled response to DNA damage
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