386 research outputs found

    Self-Organizing Networks Prospects for Group Scheduling for Disaster Relief and Public Safety Communications in Cellular Networks

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    Title from PDF of title page, viewed on June 19, 2015Thesis advisor: Cory BeardVitaIncludes bibliographic references (pages 51-52)Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2014The demand for cellular communications is anticipated to continue its hasty growth in the forthcoming future, triggered by new bandwidth hungry applications such as voice over LTE, high-definition video streaming, and multimedia file sharing in mobile phones. This has placed enormous pressure on cellular communications in terms of demand for Quality of Service (QoS), capacity, and resource management. Henceforth, the apposite utilization of obtainable spectrum is required. Public Safety (PS) organizations’ capability to exchange information is crucial to meliorate the coordination in emergency junctures. Recent catastrophes have underlined the need to enhance broadband and seamless connectivity to the PS organizations. This thesis outlines the governing issues necessitated in this, and also additional requirements of the network are addressed regardless of dynamic channel conditions and locations. In this thesis, subscribers are divided into groups viz., PS groups and regular subscriber groups. A new scheme, beyond the type of services being used by subscribers, priorities and fairness, is developed. In order to abridge operational costs and efforts, SONs (Self Organizing Networks) are implemented in this thesis and the prospects have been discussed. Additionally, Group Scheduling is implemented to achieve better performance for PS and regular subscribers groups. An advanced scheduling algorithm for group scheduling is developed which provides better QoS for multi-services and a better trade-off between Quality of Service and radio resource management. This scheduling algorithm provides a better balance between multi-QoS purveying to support mixes of sensitive traffic and best effort traffic. This phenomenon is used to choose the best subscriber and the group. Several metrics have been devised and are used for this purpose. Extensive simulation results are shown for both the conditions viz., normal and emergency conditions.Introduction -- Background -- Our work -- MATLAB code implementation -- Results and analysis -- Conclusion

    Physiology and coronary artery disease: emerging insights from computed tomography imaging based computational modeling

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    Improvements in spatial and temporal resolution now permit robust high quality characterization of presence, morphology and composition of coronary atherosclerosis in computed tomography (CT). These characteristics include high risk features such as large plaque volume, low CT attenuation, napkin-ring sign, spotty calcification and positive remodeling. Because of the high image quality, principles of patient-specific computational fluid dynamics modeling of blood flow through the coronary arteries can now be applied to CT and allow the calculation of local lesion-specific hemodynamics such as endothelial shear stress, fractional flow reserve and axial plaque stress. This review examines recent advances in coronary CT image-based computational modeling and discusses the opportunity to identify lesions at risk for rupture much earlier than today through the combination of anatomic and hemodynamic information

    Five-year follow-up of underexpanded and overexpanded bioresorbable scaffolds: Self-correction and impact on shear stress

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    Underexpansion and overexpansion have been incriminated as causative factors of adverse cardiac events. However, dynamic biological interaction between vessel wall and scaffold may attenuate the adverse haemodynamic impact of overexpansion or underexpansion

    Endothelial shear stress 5 years after implantation of a coronary bioresorbable scaffold

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    Aims: As a sine qua non for arterial wall physiology, local hemodynamic forces such as endothelial shear stress (ESS) may influence long-term vessel changes as bioabsorbable scaffolds dissolve. The aim of this study was to perform serial computational fluid dynamic (CFD) simulations to examine immediate and long-term haemodynamic and vascular changes following bioresorbable scaffold placement. Methods and results: Coronary arterial models with long-term serial assessment (baseline and 5 years) were reconstructed through fusion of intravascular optical coherence tomography and angiography. Pulsatile non-Newtonian CFD simulations were performed to calculate the ESS and relative blood viscosity. Time-averaged, systolic, and diastolic results were compared between follow-ups. Seven patients (seven lesions) were included in this analysis. A marked heterogeneity in ESS and localised regions of high blood viscosity were observed post-implantation. Percent vessel area exposed to low averaged ESS (7 Pa) did not significantly change (moderate ESS: 76.93% vs. 80.7%, P = 0.546; high ESS: 7.15% vs. 14.31%, P = 0.281), leading to higher ESS at follow-up. A positive correlation was observed between baseline ESS and change in lumen area at 5 years (P < 0.0001). Maximum blood viscosity significantly decreased over 5 years (4.30 ± 1.54 vs. 3.21± 0.57, P = 0.028). Conclusion: Immediately after scaffold implantation, coronary arteries demonstrate an alternans of extremely low and high ESS values and localized areas of high blood viscosity. These initial local haemodynamic disturbances may trigger fibrin deposition and thrombosis. Also, low ESS can promote neointimal hyperplasia, but may also contribute to appropriate scaffold healing with normalisation of ESS and reduction in peak blood viscosity by 5 years

    Endothelial shear stress 5 years after implantation of a coronary bioresorbable scaffold

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    Aims As a sine qua non for arterial wall physiology, local hemodynamic forces such as endothelial shear stress (ESS) may influence long-term vessel changes as bioabsorbable scaffolds dissolve. The aim of this study was to perform serial computational fluid dynamic (CFD) simulations to examine immediate and long-term haemodynamic and vascular changes following bioresorbable scaffold placement. Methods and results Coronary arterial models with long-term serial assessment (baseline and 5 years) were reconstructed through fusion of intravascular optical coherence tomography and angiography. Pulsatile non-Newtonian CFD simulations were performed to ca

    First measurement of the Hubble Constant from a Dark Standard Siren using the Dark Energy Survey Galaxies and the LIGO/Virgo Binary–Black-hole Merger GW170814

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    International audienceWe present a multi-messenger measurement of the Hubble constant H 0 using the binary–black-hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object-by-object Hubble diagram. However, they are suitable for a statistical measurement, provided that a galaxy catalog of adequate depth and redshift completion is available. Here we present the first Hubble parameter measurement using a black hole merger. Our analysis results in , which is consistent with both SN Ia and cosmic microwave background measurements of the Hubble constant. The quoted 68% credible region comprises 60% of the uniform prior range [20, 140] km s−1 Mpc−1, and it depends on the assumed prior range. If we take a broader prior of [10, 220] km s−1 Mpc−1, we find (57% of the prior range). Although a weak constraint on the Hubble constant from a single event is expected using the dark siren method, a multifold increase in the LVC event rate is anticipated in the coming years and combinations of many sirens will lead to improved constraints on H 0

    Expert recommendations on the assessment of wall shear stress in human coronary arteries : existing methodologies, technical considerations, and clinical applications

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    The aim of this manuscript is to provide guidelines for appropriate use of CFD to obtain reproducible and reliable wall shear stress maps in native and instrumented human coronary arteries. The outcome of CFD heavily depends on the quality of the input data, which include vessel geometrical data, proper boundary conditions, and material models. Available methodologies to reconstruct coronary artery anatomy are discussed in ‘Imaging coronary arteries: a brief review’ section. Computational procedures implemented to simulate blood flow in native coronary arteries are presented in ‘Wall shear stress in native arteries’ section. The effect of including different geometrical scales due to the presence of stent struts in instrumented arteries is highlighted in ‘Wall shear stress in stents’ section. The clinical implications are discussed in ‘Clinical applications’ section, and concluding remarks are presented in ‘Concluding remarks’ section
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