scholarly journals Past, present and future of seismic metamaterials: experiments on soil dynamics, cloaking, large scale analogue computer and space–time modulations

2021 ◽  
Vol 21 (7-8) ◽  
pp. 767-785
Author(s):  
Stéphane Brûlé ◽  
Sébastien Guenneau
Keyword(s):  
Large Scale ◽  
Space Time ◽  
Soil Dynamics ◽  
Analogue Computer

scholarly journals Space–time reduced order model for large-scale linear dynamical systems with application to Boltzmann transport problems

2021 ◽  
Vol 424 ◽  
pp. 109845
Author(s):  
Youngsoo Choi ◽  
Peter Brown ◽  
William Arrighi ◽  
Robert Anderson ◽  
Kevin Huynh
Keyword(s):  
Dynamical Systems ◽  
Large Scale ◽  
Space Time ◽  
Reduced Order Model ◽  
Boltzmann Transport ◽  
Order Model ◽  
Linear Dynamical Systems ◽  
Reduced Order ◽  
Transport Problems

Новый критерий оптимальности пространственно-временных матриц

2020 ◽  
Author(s):  
A.A. Reznev ◽  
V.B. Kreyndelin
Keyword(s):  
Computational Complexity ◽  
Large Scale ◽  
Noise Immunity ◽  
Optimality Criterion ◽  
Mimo Systems ◽  
Optimality Criteria ◽  
Space Time ◽  
Space Time Codes ◽  
Golden Code ◽  
New Criterion

The application of optimality criteria for the study of space-time codes is considered. Known rank and determinant criteria are described. The computational complexity of determinant criteria is presented taking into account some estimation of the real CPUs specifications. An algorithm for calculating a new optimality criterion is described. The computational complexity of the new optimality criterion is evaluated. The new criterion is applied to the study of the space-time Golden matrix. The obtained criterion value is used to modify the Golden code. The modeling for Golden code demonstrates that criterion works and gives us better levels for noise immunity. The proposed optimality criterion is acceptable in terms of computational complexity even for a large number of antennas, which is typical for large-scale MIMO systems. Рассматривается применение критериев оптимальности для исследования пространственно-временных кодов.Описаны известные ранговый и детерминантный критерии. Для детерминантного критерия оценена вычислительная сложность с учетом определения специальных высокопроизводительных процессоров. Описан алгоритм расчета нового критерия оптимальности. Проведена оценка вычислительной сложности нового критерия оптимальности. Новый критерий применен для исследования пространственно-временной матрицы Голден. Полученное значение критерия использовано для модификациикода Голден. Продемонстрированы кривые помехоустойчивости для кода Голден и кода Голден с модифицированным параметром, получен энергетический выигрыш. Предложенный критерий оптимальности приемлем с точки зрения вычислительнойсложности даже при большом числе антенн, характерном для систем широкомасштабного MIMO.

On the structure of conformal singularities in classical general relativity. II Evolution equations and a conjecture of K. P. Tod

1993 ◽  
Vol 443 (1919) ◽  
pp. 493-515 ◽  
Keyword(s):  
Large Scale ◽  
Evolution Equations ◽  
Physical Space ◽  
Space Time ◽  
Symmetric Hyperbolic System ◽  
First Order ◽  
Initial Hypersurface ◽  
The Cauchy Problem ◽  
Data Subject ◽  
The Universe

Consideration is given to the Cauchy problem for perfect fluid space-times which evolve from an initial singularity of conformal type. The evolution equations for the conformally transformed, unphysical geometry are shown to be expressible as a first order symmetric hyperbolic system, albeit with a singular forcing term. It is concluded that the 3-metric on the initial hypersurface of the unphysical space-time constitutes the freely specifiable initial data. Subject to Penroses’s Weyl Curvature Hypothesis, according to which the Weyl tensor was initially zero, it follows that the physical space-time is Robertson–Walker. This may provide a basis for a new explanation for the large-scale isotropy of the universe.

Complexity of low-frequency earthquakes activity in western Shikoku

2020 ◽  
Author(s):  
Natalia Poiata ◽  
Jean-Pierre Vilotte ◽  
Nikolai Shapiro ◽  
Mariano Supino ◽  
Kazushige Obara
Keyword(s):  
Subduction Zones ◽  
Large Scale ◽  
Active Faults ◽  
Low Frequency ◽  
Space Time ◽  
Interaction Patterns ◽  
Slow Slip Events ◽  
Time Activity ◽  
Tectonic Tremor ◽  
Slow Earthquakes

<p>Short-duration transient seismic events known as low-frequency earthquakes (LFEs) are a component of the slow earthquakes family observed in the transition zone, at the root of seismogenic regions of the subduction zones or active faults. LFEs are the signature of impulse seismic energy radiation associated to and often mixed within complex tectonic tremor signal. Detailed analysis and characterization of LFE space-time activity in relation to other slow earthquake phenomena can provide important information about the state and the processes of fault interface.</p><p>We derive a catalog of LFEs in western Shikoku (Japan) by applying a full waveform coherency-based detection and location method to the 4-year continuous data covering the period of 2013-2016 and recorded at Hi-net seismic stations of NIED. The obtained catalog of over 150,000 detected events allows looking into the details of LFE space-time activity during the tectonic tremor sequences and inter-sequence periods.</p><p>We use this catalogue of LFEs to perform a systematic statistical analysis of the event occurrence patterns by applying correlation and clustering analysis to infer the large-scale (long temporal ~ 1-2 day duration) space-time characteristics and interaction patterns of activity and its potential relation to the structural complexity of the subducting plate. We also analyze the correlation between the migration of clustered LFE activity during energetic tremor sequences and short-term slow slip events occurring in the area during the analyzed period.</p>

scholarly journals A Lane-Level LBS System for Vehicle Network with High-Precision BDS/GPS Positioning

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Chi Guo ◽  
Wenfei Guo ◽  
Guangyi Cao ◽  
Hongbo Dong
Keyword(s):  
High Precision ◽  
Traffic Safety ◽  
Large Scale ◽  
Space Time ◽  
Mobile Internet ◽  
Network Systems ◽  
Precise Positioning ◽  
Network Location ◽  
Location Service ◽  
Vehicle Network

In recent years, research on vehicle network location service has begun to focus on its intelligence and precision. The accuracy of space-time information has become a core factor for vehicle network systems in a mobile environment. However, difficulties persist in vehicle satellite positioning since deficiencies in the provision of high-quality space-time references greatly limit the development and application of vehicle networks. In this paper, we propose a high-precision-based vehicle network location service to solve this problem. The major components of this study include the following: (1) application of wide-area precise positioning technology to the vehicle network system. An adaptive correction message broadcast protocol is designed to satisfy the requirements for large-scale target precise positioning in the mobile Internet environment; (2) development of a concurrence service system with a flexible virtual expansion architecture to guarantee reliable data interaction between vehicles and the background; (3) verification of the positioning precision and service quality in the urban environment. Based on this high-precision positioning service platform, a lane-level location service is designed to solve a typical traffic safety problem.

Further space-time correlations of velocity in a turbulent boundary layer

1958 ◽  
Vol 3 (4) ◽  
pp. 344-356 ◽  
Author(s):  
A. J. Favre ◽  
J. J. Gaviglio ◽  
R. J. Dumas
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Large Scale ◽  
Flow Direction ◽  
Space Time ◽  
Mean Flow ◽  
Taylor’S Hypothesis ◽  
Time Correlations ◽  
The Mean ◽  
Hot Wires

This paper describes the results of further experimental investigation of the turbulent boundary layer with zero pressure gradient. Measurements of autocorrelation and of space-time double correlation have been made respectively with single hot-wires and with two hot-wires with the separation vector in any direction. Space-time correlations reach a maximum for some optimum delay. In the case of two points set on a line orthogonal to the plate, the optimum delay Ti is not zero. In the general case it is equal to the corresponding delay Ti, increased by compensating delay for translation with the mean flow. Taylor's hypothesis may be applied to the boundary layer at distances from the wall greater than 3% of the layer thickness. Space-time isocorrelation surfaces obtained with optimum delay have a large aspect ratio in the mean flow direction, even if they are relative to a point close to the wall (0·03δ); the correlations along the mean flow then retain high values on account of the large scale of the turbulence.

Variational space–time elements for large-scale systems

2017 ◽  
Vol 326 ◽  
pp. 541-572 ◽  
Author(s):  
C. Hesch ◽  
S. Schuß ◽  
M. Dittmann ◽  
S.R. Eugster ◽  
M. Favino ◽  
...  
Keyword(s):  
Large Scale ◽  
Space Time ◽  
Large Scale Systems
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