10,240 research outputs found

    Outbursts of Young Stellar Objects

    Full text link
    We argue that the outbursts of the FU Orionis stars occur on timescales which are much longer than expected from the standard disc instability model with \alpha_{c} \gtrsim 10^{-3}. The outburst, recurrence, and rise times are consistent with the idea that the accretion disc in these objects is truncated at a radius R_{i} \sim 40 \rsun. In agreement with a number of previous authors we suggest that the inner regions of the accretion discs in FU Ori objects are evacuated by the action of a magnetic propeller anchored on the central star. We develop an analytic solution for the steady state structure of an accretion disc in the presence of a central magnetic torque, and present numerical calculations to follow its time evolution. These calculations confirm that a recurrence time that is consistent with observations can be obtained by selecting appropriate values for viscosity and magnetic field strength.Comment: 13 pages, 7 figures, accepted by MNRA

    National Hospital Management Portal (NHMP): a framework for e-health implementation

    Get PDF
    Health information represents the main basis for health decisionmaking process and there have been some efforts to increase access to health information in developing countries. However, most of these efforts are based on the internet which has minimal penetration especially in the rural and sub-urban part of developing countries. In this work, a platform for medical record acquisition via the ubiquitous 2.5G/3G wireless communications technologies is presented. The National Hospital Management Portal (NHMP)platform has a central database at each specific country’s national hospita

    Estimating An Optimal Backpropagation Algorithm for Training An ANN with the EGFR Exon 19 Nucleotide Sequence: An Electronic Diagnostic Basis for Non–Small Cell Lung Cancer(NSCLC)

    Get PDF
    One of the most common forms of medical malpractices globally is an error in diagnosis. An improper diagnosis occurs when a doctor fails to identify a disease or report a disease when the patient is actually healthy. A disease that is commonly misdiagnosed is lung cancer. This cancer type is a major health problem internationally because it is responsible for 15% of all cancer diagnosis and 29% of all cancer deaths. The two major sub-types of lung cancer are; small cell lung cancer (about 13%) and non-small cell lung cancer (%SCLC- about 87%). The chance of surviving lung cancer depends on its correct diagnosis and/or the stage at the time it is diagnosed. However, recent studies have identified somatic mutations in the epidermal growth factor receptor (EGFR) gene in a subset of non-small cell lung cancer (%SCLC) tumors. These mutations occur in the tyrosine kinase domain of the gene. The most predominant of the mutations in all %SCLC patients examined is deletion mutation in exon 19 and it accounts for approximately 90% of the EGFR-activating mutations. This makes EGFR genomic sequence a good candidate for implementing an electronic diagnostic system for %SCLC. In this study aimed at estimating an optimum backpropagation training algorithm for a genomic based A%% system for %SCLC diagnosis, the nucleotide sequences of EGFR’s exon 19 of a noncancerous cell were used to train an artificial neural network (A%%). Several A%% back propagation training algorithms were tested in MATLAB R2008a to obtain an optimal algorithm for training the network. Of the nine different algorithms tested, we achieved the best performance (i.e. the least mean square error) with the minimum epoch (training iterations) and training time using the Levenberg-Marquardt algorithm

    Automatic Electrical Appliances Control Panel Based on Infrared and Wi-Fi: A Framework for Electrical Energy Conservation

    Get PDF
    -Today, proprietary home automation targets very specific applications which operate mostly on a cable based infrastructure. In contrast to that, our implementation builds on a wireless platform for the automatic control of house hold electrical appliances. The nodes gather sensor readings in a home and transmit them to a central automation server. There, the readings are matched against a list of script statements. When there is a match, a specific action is performed. An important property of the system is that the control of all home appliances is done by means of the ubiquitous Infrared and Wi-Fi wireless technologies. This way, the co-operation between manufacturers is not a necessity in order to connect devices to the home automation network

    The steady-state structure of accretion discs in central magnetic fields

    Full text link
    We develop a new analytic solution for the steady-state structure of a thin accretion disc under the influence of a magnetic field that is anchored to the central star. The solution takes a form similar to that of Shakura and Sunyaev and tends to their solution as the magnetic moment of the star tends to zero. As well as the Kramer's law case, we obtain a solution for a general opacity. The effects of varying the mass transfer rate, spin period and magnetic field of the star as well as the opacity model applied to the disc are explored for a range of objects. The solution depends on the position of the magnetic truncation radius. We propose a new approach for the identification of the truncation radius and present an analytic expression for its position.Comment: 11 pages, 7 figures, accepted by MNRA

    Nomadic Base Station (NBS): a Software Defined Radio (SDR) based Architecture for Capacity Enhancement in Mobile Communications Networks

    Get PDF
    In this research work, the problem of congestion that leads to dropped calls at GSM cell sites and drastic reduction in network capacity is addressed. We designed a novel GSM base station architecture named Nomadic Base Station (NBS) which is based on Software Defined Radio (SDR) architecture and simulated the LNA for its receiver front-end. The NBS receiver LNA selects and amplifies GSM signal bursts operating at 900MHz and 1800MHz Radio Frequency Band. The later stages translate the Radio Frequency (RF) signal to Intermediate Frequency (IF) signal. This implements the SDR technology by digitizing the IF signal into bit streams that can be processed on generic Central Processing Unit (CPU) using custom written signal processing software

    Development of a Solar Photovoltaic Vulcanizing Machine towards Extreme Poverty Eradication in Africa

    Get PDF
    The number of African families living in extreme poverty has continued to increase even though the proportion of the citizens in such situation in this region declined in recent years. This is traceable to unemployment, underemployment, and income inequalities that have generated social unrest as joblessness persist. However, entrepreneurship through small and medium-scale enterprises (SMEs) has the capacity to drive economic growth and national development through job creation, income empowerment, and poverty eradication. Roadside vulcanizing business in towns and cities of Africa is a viable job that can be run by any age group and it requires no formal training or long apprenticeship to develop expertise. Unfortunately, the cost of running the fossil fuel-powered vulcanizing machine will leave the technician with little or no profit due to the recent fuel subsidy removal by some countries like Nigeria. In addition, overdependence on fossil fuel as a primary source of energy promotes the negative effects of carbon dioxide and other global warming emissions on environment, climate, and public health. In this paper, considering the abundant solar energy potential across all the Sub-Saharan countries, we designed and constructed a solar photovoltaic vulcanizing machine as a practical means of eradicating extreme poverty in line with the 2030 Sustainable Development Goals (SDGs) agenda. The implementation of this project will create employment opportunities for millions of Africans, reduce social violence and crime, provide affordable and clean energy, and save our planet
    • …
    corecore