2,324 research outputs found

    Correlation functions of small-scale fluctuations of the interplanetary magnetic field

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    The Interplanetary Magnetic Field shows complex spatial and temporal variations. Single spacecraft measurements reveal only a one dimensional section of this rich four dimensional phenomenon. Multi-point measurements of the four Cluster spacecraft provide a unique tool to study the spatiotemporal structure of the field. Using Cluster data we determined three dimensional correlation functions of the fluctuations. By means of the correlation function one can describe and measure field variations. Our results can be used to verify theoretical predictions, to understand the formation and nature of solar wind turbulence. We found that the correlation length varies over almost six orders of magnitude. The IMF turbulence shows significant anisotropy with two distinct populations. In certain time intervals the ratio of the three axes of the correlation ellipse is 1/2.2/6 while in the remaining time we found extremely high correlation along one axis. We found favoured directions in the orientation of the correlation ellipsoids.Comment: accepted to Solar Physics on June 14, 2010. 10 pages, 8 figure

    Comparative study ofthe computational fluid dynamics and fluid structure interaction analysis in human airways flow

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    Numerous studies have been done in order to get the most accurate result that represents the flow characteristics inside the human trachea. Numerical method was the most favorite type of study chosen to simulate the model due to the complexity of the geometry and difficulties to get the real trachea to do the experimental works. In this study, one actual healthy model of human trachea was reconstructed in order to compare, the different of the velocity and pressure distribution between two types of numerical modeling analysis: Computational Fluid Dynamics (CFD) and Fluid Structure Interaction (FSI) analysis. The model was extracted using the Computed Tomography (CT) scan images to maintain the realistic geometry. Velocity, 1.24 m/s was used at the inlet and the variations of the velocity and pressure distribution along the trachea were observed. The results shown that, the implementation of the FSI technique did produce different result and flexibility of the structure wall did influence the distribution of the velocity and pressure along the trachea

    Data mining techniques for the assessment of factors contributing to the damage of residential houses in Australia

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    This paper reports on the preparation and management processes of inconsistent data on damage on residential houses in Victoria, Australia. There are no existing specific and fully relevant databases readily available except for the incomplete paper-based and electronic-based reports. Therefore, the extracting of information from the reports is complicated and time consuming in order to extract and include all the necessary information needed for analysis of damage on residential houses founded on expansive soils. Data mining is adopted to develop a database. Statistical methods and Artificial Intelligence methods are used to quantify the quality of data. The paper concludes that the development of such database could enable BHC to evaluate the usefulness of the reports prepared on the reported damage properties for further analysis

    Practice implications of an antimicrobial stewardship intervention in a tertiary care teaching hospital, Qatar

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    Background: Antibiotic misuse is a worldwide public health problem and has been associated with increased morbidity, length of hospital stay, mortality, healthcare costs, and most importantly antibiotic resistance. Aims: We aimed to evaluate the compliance of antibiotic prescribing with national guidelines, assess how educational interventions can best be utilized to make impact and fill gaps for optimal antibiotic utilization, and to identify facilitators and barriers to implementing ASPs in Qatar. Methods: Six cross-sectional baseline audits of antibiotic prescribing were conducted over a two-week period at a tertiary care teaching hospital. A sub-analysis of prescriptions with follow up has followed. An educational intervention utilizing the PDSA (Plan-Do-Study-Act) tool was implemented to address gaps identified. A repeated audit was done to assess the impact of change. Lastly, interviews were conducted to recognize perceived facilitators and barriers for ASP implementation, identify strategies to overcome barriers, and evaluate the effectiveness of educational interventions. Results: The most common indication for antibiotic prescribing was febrile neutropenia (20.7%). The most frequently used class of antibiotics was carbapenems (21.4%). Sixty percent of prescriptions complied with guidelines. The rationale behind choosing not to adhere to guidelines was not documented in 37.2% of cases. Suboptimal documentation in records was targeted through our intervention. The audit post intervention showed slight improvement in documentation. Facilitators and barriers included: collaboration and communication among teams, compliance with guidelines, interventions documented by clinical pharmacists, and electronic system errors. Conclusions: Effective communication, continuous documentation in records, and repetitive education promote rational antibiotic prescribing and enhance ASPs.This report was made possible by a UREP award [UREP18-033-3-010] from the Qatar National Research Fund (a member of The Qatar Foundation)

    Suitable MLP Network Activation Functions For Breast Cancer And Thyroid Disease Detection.

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    This paper presents a comparison study of various MLP activation functions for detection and classification problems

    Targeting Low-arsenic Groundwater with Mobile-phone Technology in Araihazar, Bangladesh

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    The Bangladesh Arsenic Mitigation and Water Supply Program (BAMWSP) has compiled field-kit measurements of the arsenic content of groundwater for nearly five million wells. By comparing the spatial distribution of arsenic inferred from these field-kit measurements with geo-referenced laboratory data in a portion of Araihazar upazila, it is shown here that the BAMWSP data could be used for targeting safe aquifers for the installation of community wells in many villages of Bangladesh. Recent experiences with mobile-phone technology to access and update the BAMWSP data in the field are also described. It is shown that the technology, without guaranteeing success, could optimize interventions by guiding the choice of the drilling method that is likely to reach a safe aquifer and identifying those villages where exploratory drilling is needed

    Numerical simulation of concentration over-voltage in a polymer electrolyte fuel cell under low-hydrogen conditions

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    This article elucidates the effect of low hydrogen concentration fuel gas on polymer electrolyte fuel cell (PEFC) performance, with particular emphasis on the transport of chemical species in the anode separator channel and the electrochemical reactions. A numerical simulation model for PEFCs was developed; the model combined a computational fluid dynamics model for mass transfer in the anode separator and the gas diffusion layer(GDL)as well as a PEFC electrochemical reaction model takinginto account the activation, concentration, and resistance over-voltages. The emphasis in this study is placed on obtaining a basic understanding of how three-dimensional flow and low-hydrogen fuel transport phenomena in the anode separator channelimpactthe electrochemical processes occurring in PEFCs. Comparison of the numerical simulation results with experimental data indicates that the performance degradation in PEFCs is negligible for hydrogen concentrations over 30%, whereas it becomes significant for concentrations below 10%. Furthermore, the numerical simulationresults showthat controlling the fuel supply flow rate stimulates hydrogen transport inthe GDL and the catalyst layer, which consequently enhances PEFC performance under low-hydrogen conditions
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