Real-Time Coseismic Velocity and Displacements Retrieving and De-Noising Process by High-Rate GNSS

2013 ◽  
pp. 523-537 ◽  
Author(s):  
Rui Tu ◽  
Rongjiang Wang ◽  
Yong Zhang ◽  
Maorong Ge ◽  
Qin Zhang
Keyword(s):  
Real Time ◽  
High Rate

Content Repurposing for Small Devices

2011 ◽  
pp. 110-115
Author(s):  
Neil C. Rowe
Keyword(s):  
Real Time ◽  
Automated Planning ◽  
High Rate ◽  
Handheld Devices ◽  
Personal Digital Assistants ◽  
Web Page ◽  
Multimedia Delivery ◽  
Video And Audio ◽  
New Devices

Content repurposing is the reorganizing of data for presentation on different display hardware (Singh, 2004). It has been particularly important recently with the growth of handheld devices such as personal digital assistants (PDAs), sophisticated telephones, and other small specialized devices. Unfortunately, such devices pose serious problems for multimedia delivery. With their tiny screens (150 by 150 for a basic Palm PDA or 240 by 320 for a more modern one, vs. 640 by 480 for standard computer screens), one cannot display much information (i.e., most of a Web page); with their low bandwidths, one cannot display video and audio transmissions from a server (i.e., streaming) with much quality; and with their small storage capabilities, large media files cannot be stored for later playback. Furthermore, new devices and old ones with new characteristics have been appearing at a high rate, so software vendors are having difficulty keeping pace. So some real-time, systematic, and automated planning could be helpful in figuring how to show desired data, especially multimedia, on a broad range of devices.

scholarly journals Real-time inversions for finite fault slip models and rupture geometry based on high-rate GPS data

2014 ◽  
Vol 119 (4) ◽  
pp. 3201-3231 ◽  
Author(s):  
S. E. Minson ◽  
Jessica R. Murray ◽  
John O. Langbein ◽  
Joan S. Gomberg
Keyword(s):  
Real Time ◽  
Fault Slip ◽  
High Rate ◽  
Gps Data ◽  
Finite Fault

Optimization of Rapid State Estimation in Structures Subjected to High-Rate Boundary Change

2020 ◽  
Author(s):  
James Scheppegrell ◽  
Adriane G. Moura ◽  
Jacob Dodson ◽  
Austin Downey
Keyword(s):  
Frequency Response ◽  
State Estimation ◽  
Real Time ◽  
Performance Metrics ◽  
Numerical Models ◽  
Vertical Axis ◽  
High Rate ◽  
Position Measurement ◽  
Data Set ◽  
Variable Boundary

Abstract Many structures are subjected to varying forces, moving boundaries, and other dynamic conditions. Whether part of a vehicle, building, or active energy mitigation device, data on such changes can represent useful knowledge, but also presents challenges in its collection and analysis. In systems where changes occur rapidly, assessment of the system’s state within a useful time span is required to enable an appropriate response before the system’s state changes further. Rapid state estimation is especially important but poses unique difficulties. In determining the state of a structural system subjected to high-rate dynamic changes, measuring the frequency response is one method that can be used to draw inferences, provided the system is adequately understood and defined. The work presented here is the result of an investigation into methods to determine the frequency response, and thus state, of a structure subjected to high-rate boundary changes in real-time. In order to facilitate development, the Air Force Research Laboratory created the DROPBEAR, a testbed with an oscillating beam subjected to a continuously variable boundary condition. One end of the beam is held by a stationary fixed support, while a pinned support is able to move along the beam’s length. The free end of the beam structure is instrumented with acceleration, velocity, and position sensors measuring the beam’s vertical axis. Direct position measurement of the pin location is also taken to provide a reference for comparison with numerical models. This work presents a numerical investigation into methods for extracting the frequency response of a structure in real-time. An FFT based method with a rolling window is used to track the frequency of a data set generated to represent the range of the DROPBEAR, and is run with multiple window lengths. The frequency precision and latency of the FFT method is analyzed in each configuration. A specialized frequency extraction technique, Delayed Comparison Error Minimization, is implemented with parameters optimized for the frequency range of interest. The performance metrics of latency and precision are analyzed and compared to the baseline rolling FFT method results, and applicability is discussed.

scholarly journals A Decentralized Processing Schema for Efficient and Robust Real-time Multi-GNSS Satellite Clock Estimation

2019 ◽  
Vol 11 (21) ◽  
pp. 2595
Author(s):  
Jiang ◽  
Gu ◽  
Li ◽  
Ge ◽  
Schuh
Keyword(s):  
Real Time ◽  
High Frequency ◽  
Precise Point Positioning ◽  
High Rate ◽  
Reference Network ◽  
Satellite Clock ◽  
Navigation Data ◽  
Data Analyst ◽  
New Strategy ◽  
Clock Estimation

Real-time multi-GNSS precise point positioning (PPP) requires the support of high-rate satellite clock corrections. Due to the large number of ambiguity parameters, it is difficult to update clocks at high frequency in real-time for a large reference network. With the increasing number of satellites of multi-GNSS constellations and the number of stations, real-time high-rate clock estimation becomes a big challenge. In this contribution, we propose a decentralized clock estimation (DECE) strategy, in which both undifferenced (UD) and epoch-differenced (ED) mode are implemented but run separately in different computers, and their output clocks are combined in another process to generate a unique product. While redundant UD and/or ED processing lines can be run in offsite computers to improve the robustness, processing lines for different networks can also be included to improve the clock quality. The new strategy is realized based on the Position and Navigation Data Analyst (PANDA) software package and is experimentally validated with about 110 real-time stations for clock estimation by comparison of the estimated clocks and the PPP performance applying estimated clocks. The results of the real-time PPP experiment using 12 global stations show that with the greatly improved computational efficiency, 3.14 cm in horizontal and 5.51 cm in vertical can be achieved using the estimated DECE clock.

scholarly journals High-rate wireless data communications: An underwater acoustic communications framework at the physical layer

1996 ◽  
Vol 2 (6) ◽  
pp. 449-485 ◽  
Author(s):  
Anthony G. Bessios ◽  
Frank M. Caimi
Keyword(s):  
Real Time ◽  
High Speed ◽  
High Rate ◽  
Statistical Decision Theory ◽  
Data Communications ◽  
Acoustic Communications ◽  
Statistical Decision ◽  
Theoretical Formulation ◽  
Underwater Acoustic ◽  
Detection Techniques

A variety of signal processing functions are performed by Underwater Acoustic Systems. These include: 1) detection to determine presence or absence of information signals in the presence of noise, or an attempt to describe which of a predetermined finite set of possible messages{mi,i,...,M}the signal represents; 2) estimation of some parameterθˆassociated with the received signal (i.e. range, depth, bearing angle, etc.); 3) classification and source identification; 4) dynamics tracking; 5) navigation (collision avoidance and terminal guidance); 6) countermeasures; and 7) communications. The focus of this paper is acoustic communications.There is a global current need to develop reliable wireless digital communications for the underwater environment, with sufficient performance and efficiency to substitute for costly wired systems. One possible goal is a wireless system implementation that insures underwater terminal mobility. There is also a vital need to improve the performance of the existing systems in terms of data-rate, noise immunity, operational range, and power consumption, since, in practice, portable high-speed, long range, compact, low-power systems are desired.We concede the difficulties associated with acoustic systems and concentrate on the development of robust data transmission methods anticipating the eventual need for real time or near real time video transmission. An overview of the various detection techniques and the general statistical digital communication problem is given based on a statistical decision theory framework. The theoretical formulation of the underwater acoustic data communications problem includes modeling of the stochastic channel to incorporate a variety of impairments and environmental uncertainties, and proposal of new compensation strategies for an efficient and robust receiver design.

Real-time earthquake hazard assessment based on high-rate GNSS PPPAR

2020 ◽  
Author(s):  
Yang Jiang ◽  
Yang Gao ◽  
Michael Sideris
Keyword(s):  
Real Time ◽  
Hazard Assessment ◽  
Seismic Waves ◽  
Seismic Hazard Assessment ◽  
Earthquake Hazard ◽  
High Rate ◽  
Peak Ground Velocity ◽  
International Gnss Service ◽  
Time Service ◽  
Earthquake Hazard Assessment

<p>To provide hazard assessment in rapid or real-time mode, accelerations due to seismic waves have traditionally been recorded by seismometers. Another approach, based on the Global Navigation Satellite System (GNSS), known as GNSS seismology, has become increasingly accurate and reliable. In the past decade, significant improvements have been made in high-rate GNSS using precise point positioning and its ambiguity resolution (PPPAR). To reach cm-level accuracy, however, PPPAR requires specific products, including satellite orbit/clock corrections and phase/code biases generated by large GNSS networks. Therefore, the use of PPPAR in real-time seismology applications has been inhibited by the limitations in product accessibility, latency, and accuracy. To minimize the implementation barrier for ordinary global users, the Centre National D’Etudes Spatiales (CNES) in France has launched a public PPPAR correction service via real-time internet streams. Broadcasting via the real-time service (RTS) of the international GNSS service (IGS), the correction stream is freely provided. Therefore, in our work, a new approach using PPPAR assisted with the CNES product to process high-rate in-field GNSS measurements is proposed for real-time earthquake hazard assessment. A case study is presented for the Ridgecrest, California earthquake sequence in 2019. The general performance of our approach is evaluated by assessing the quality of the resulting waveforms against publicly available post-processing GNSS results from a previous study by Melgar et al. (2019), Seismol. Res. Lett. XX, 1–9, doi: 10.1785/ 0220190223. Even though the derived real-time displacements are noisy due to the accuracy limitation of the CNES product, the results show a cm-level agreement with the provided post-processed control values in terms of root-mean-square (RMS) values in time and frequency domain, as well as seismic features of peak-ground-displacement (PGD) and peak-ground-velocity (PGV). Overall, we have shown that high-rate GNSS processing based on PPPAR via a freely accessible service like CNES is a reliable approach that can be utilized for real-time seismic hazard assessment.</p>

scholarly journals Conception of a New Recoil Proton Telescope for Real-Time Neutron Spectrometry in Proton-Therapy

2018 ◽  
Vol 170 ◽  
pp. 09001 ◽  
Author(s):  
Rodolphe Combe ◽  
Nicolas Arbor ◽  
Ziad el Bitar ◽  
Stéphane Higueret ◽  
Daniel Husson
Keyword(s):  
Real Time ◽  
Neutron Spectrum ◽  
Proton Therapy ◽  
Recoil Proton ◽  
Reference Method ◽  
Weighting Factor ◽  
High Rate ◽  
Neutron Spectrometry ◽  
Neutron Spectrometer ◽  
Integrated Sensor

Neutrons are the main type of secondary particles emitted in proton-therapy. Because of the risk of secondary cancer and other late occurring effects, the neutron dose should be included in the out-of-field dose calculations. A neutron spectrometer has to be used to take into account the energy dependence of the neutron radiological weighting factor. Due to its high dependence on various parameters of the irradiation (beam, accelerator, patient), the neutron spectrum should be measured independently for each treatment. The current reference method for the measurement of the neutron energy, the Bonner Sphere System, consists of several homogeneous polyethylene spheres with increasing diameters equipped with a proportional counter. It provides a highresolution reconstruction of the neutron spectrum but requires a time-consuming work of signal deconvolution. New neutron spectrometers are being developed, but the main experimental limitation remains the high neutron flux in proton therapy treatment rooms. A new model of a real-time neutron spectrometer, based on a Recoil Proton Telescope technology, has been developed at the IPHC. It enables a real-time high-rate reconstruction of the neutron spectrum from the measurement of the recoil proton trajectory and energy. A new fast-readout microelectronic integrated sensor, called FastPixN, has been developed for this specific purpose.A first prototype, able to detect neutrons between 5 and 20 MeV, has already been validated for metrology with the AMANDE facility at Cadarache. The geometry of the new Recoil Proton Telescope has been optimized via extensive Geant4 Monte Carlo simulations. Uncertainty sources have been carefully studied in order to improve simultaneously efficiency and energy resolution, and solutions have been found to suppress the various expected backgrounds. We are currently upgrading the prototype for secondary neutron detection in proton therapy applications.

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