Universality and Realistic Extensions to the Semi-Analytic Simulation Principle in GNSS Signal Processing

Semi-analytic simulation principle in GNSS signal processing bypasses the bit-true operations at high sampling frequency. Instead, signals at the output branches of the integrate&dump blocks are successfully modeled, thus making extensive Monte Carlo simulations feasible. Methods for simulations of code and carrier tracking loops with BPSK, BOC signals have been introduced in the literature. Matlab toolboxes were designed and published. In this paper, we further extend the applicability of the approach. Firstly, we describe any GNSS signal as a special instance of linear multi-dimensional modulation. Thereby, we state universal framework for classification of differently modulated signals. Using such description, we derive the semi-analytic models generally. Secondly, we extend the model for realistic scenarios including delay in the feed back, slowly fading multipath effects, finite bandwidth, phase noise, and a combination of these. Finally, a discussion on connection of this semi-analytic model and position-velocity-time estimator is delivered, as well as comparison of theoretical and simulated characteristics, produced by a prototype simulator developed at CTU in Prague

Adsorption volume and absolute adsorption: 2. Adsorption from liquid phase

A critical analysis of the isotherms of excess and absolute adsorption, as well as the adsorption space performed in the first part [1] is continued; however, as applied to the equilibrium physical adsorption from the liquid phase. The correct method is proposed for evaluating the adsorption volume of solid adsorbents with an arbitrary structure by the isotherm of excess adsorption of binary mixture of liquids. This method is successfully tested for nine different adsorption systems

Distributed Extended Kalman Filter for Position, Velocity, Time, Estimation in Satellite Navigation Receivers

Common techniques for position-velocity-time estimation in satellite navigation, iterative least squares and the extended Kalman filter, involve matrix operations. The matrix inversion and inclusion of a matrix library pose requirements on a computational power and operating platform of the navigation processor. In this paper, we introduce a novel distributed algorithm suitable for implementation in simple parallel processing units each for a tracked satellite. Such a unit performs only scalar sum, subtraction, multiplication, and division. The algorithm can be efficiently implemented in hardware logic. Given the fast position-velocity-time estimator, frequent estimates can foster dynamic performance of a vector tracking receiver. The algorithm has been designed from a factor graph representing the extended Kalman filter by splitting vector nodes into scalar ones resulting in a cyclic graph with few iterations needed. Monte Carlo simulations have been conducted to investigate convergence and accuracy. Simulation case studies for a vector tracking architecture and experimental measurements with a real-time software receiver developed at CTU in Prague were conducted. The algorithm offers compromises in stability, accuracy, and complexity depending on the number of iterations. In scenarios with a large number of tracked satellites, it can outperform the traditional methods at low complexity

The Witch Navigator - A Low Cost GNSS Software Receiver for Advanced Processing Techniques

The developement of advanced GNSS signal processing algorithms such as multi-constellation, multi-frequency and multi-antenna navigation requires an easily reprogrammable software defined radio solution. Various receiver architectures for this purpose have been introduced. RF front-end with FPGA universal correlators on ExpressCard connected directly to PC was selected and manufactured. Such a~unique hardware combination provides the GNSS researchers and engineers with a~great convenience of writing the signal processing algorithms including tracking, acquisition and positioning in the Linux application programming interface and enables them to reconfigure the RF front-end easily by the PC program. With more of these ExpressCards connected to the PC, the number of the RF channels, correlators or antennas can be increased to further boost the computational power. This paper reveals the implementation aspects of the receiver, named the Witch Navigator, and~gives the key test results

Theoretical insight of physical adsorption for a single component adsorbent + adsorbate system: II. The Henry region

10.1021/la900217tLangmuir25137359-7367LANG

Contemporary Presentation and Management of Valvular Heart Disease The EURObservational Research Programme Valvular Heart Disease II Survey

International audienceBackground: Valvular heart disease (VHD) is an important cause of mortality and morbidity and has been subject to important changes in management. The VHD II survey was designed by the EURObservational Research Programme of the European Society of Cardiology to analyze actual management of VHD and to compare practice with guidelines. Methods: Patients with severe native VHD or previous valvular intervention were enrolled prospectively across 28 countries over a 3-month period in 2017. Indications for intervention were considered concordant if the intervention was performed or scheduled in symptomatic patients, corresponding to Class I recommendations specified in the 2012 European Society of Cardiology and in the 2014 American Heart Association/American College of Cardiology VHD guidelines. Results: A total of 7247 patients (4483 hospitalized, 2764 outpatients) were included in 222 centers. Median age was 71 years (interquartile range, 62-80 years); 1917 patients (26.5%) were >= 80 years; and 3416 were female (47.1%). Severe native VHD was present in 5219 patients (72.0%): aortic stenosis in 2152 (41.2% of native VHD), aortic regurgitation in 279 (5.3%), mitral stenosis in 234 (4.5%), mitral regurgitation in 1114 (21.3%; primary in 746 and secondary in 368), multiple left-sided VHD in 1297 (24.9%), and right-sided VHD in 143 (2.7%). Two thousand twenty-eight patients (28.0%) had undergone previous valvular intervention. Intervention was performed in 37.0% and scheduled in 26.8% of patients with native VHD. The decision for intervention was concordant with Class I recommendations in symptomatic patients with severe single left-sided native VHD in 79.4% (95% CI, 77.1-81.6) for aortic stenosis, 77.6% (95% CI, 69.9-84.0) for aortic regurgitation, 68.5% (95% CI, 60.8-75.4) for mitral stenosis, and 71.0% (95% CI, 66.4-75.3) for primary mitral regurgitation. Valvular interventions were performed in 2150 patients during the survey; of them, 47.8% of patients with single left-sided native VHD were in New York Heart Association class III or IV. Transcatheter procedures were performed in 38.7% of patients with aortic stenosis and 16.7% of those with mitral regurgitation. Conclusions: Despite good concordance between Class I recommendations and practice in patients with aortic VHD, the suboptimal number in mitral VHD and late referral for valvular interventions suggest the need to improve further guideline implementation