Modeling and analysis of LOFAR scintillation data

2021 ◽  
Author(s):  
Marcin Grzesiak ◽  
Mariusz Pożoga ◽  
Barbara Matyjasiak ◽  
Dorota Przepiórka ◽  
Hanna Rothkaehl ◽  
...  
Keyword(s):  
Full Range ◽  
Cosmic Radio ◽  
Radio Emissions ◽  
Modeling And Analysis ◽  
Plasma Irregularities ◽  
Time Space ◽  
Cosmic Medium ◽  
Evolution Characteristics ◽  
Space Frequency ◽  
Good Coverage

<p>Scintillation of beacon satellite signals or distant cosmic radio emissions can provide interesting information on the cosmic medium itself, its internal spatial structure and basic evolution characteristics. LOFAR network gives consistent scintillation data with good coverage both in time and space and for the frequency range that goes down close to the local plasma frequency (LBA) being thus sensible to ionospheric plasma irregularities. LOFAR Scintillation measurements in the LBA range exhibit very interesting morphologies. Based on scintillation simulations using the phase screen method, including multiple scattering and refraction, we try to untangle the information contained in the full range (time, space, frequency) of LOFAR data and verify a number of hypotheses about the local structure of the ionosphere and its evolution.</p>

scholarly journals Optimal Time-Space Trade-Offs for Sorting

1998 ◽  
Vol 5 (10) ◽  
Author(s):  
Jakob Pagter ◽  
Theis Rauhe
Keyword(s):  
Lower Bound ◽  
Upper Bound ◽  
Fundamental Problem ◽  
Full Range ◽  
Optimal Time ◽  
Sorting Algorithm ◽  
Logarithmic Factor ◽  
Time Space ◽  
Trade Offs ◽  
Space Product

We study the fundamental problem of sorting in a sequential model of computation and in particular consider the time-space trade-off (product of time and space) for this problem.<br />Beame has shown a lower bound of  Omega(n^2) for this product leaving a gap of a logarithmic factor up to the previously best known upper bound of O(n^2 log n) due to Frederickson. Since then, no progress has been made towards tightening this gap.<br />The main contribution of this paper is a comparison based sorting algorithm which closes this gap by meeting the lower bound of Beame. The time-space product O(n^2) upper bound holds for the full range of space bounds between log n and n/log n. Hence in this range our algorithm is optimal for comparison based models as well as for the very powerful general models considered by Beame.

A Backend System for Registering Narrowband Cosmic Radio Emissions

2020 ◽  
Vol 63 (4) ◽  
pp. 561-566
Author(s):  
S. A. Grenkov ◽  
N. E. Kol’tsov
Keyword(s):  
Cosmic Radio ◽  
Radio Emissions

3D Wavelet Multiresolution of Multiphase Flow CT Images

2002 ◽  
Author(s):  
Masahiro Takei ◽  
Hui Li ◽  
Mitsuaki Ochi ◽  
Yoshifuru Saito ◽  
Kiyoshi Horii
Keyword(s):  
Cross Section ◽  
Density Fluctuation ◽  
Particle Density ◽  
Three Dimensional ◽  
Density Fluctuations ◽  
Time Space ◽  
Bent Pipe ◽  
Space Frequency ◽  
Pass Through ◽  
Discrete Wavelets

The extraction of dominant particle density fluctuation in various time-space frequency levels on a pipeline cross section was performed using capacitance-computed tomography and three-dimensional discrete wavelets transform. As a result, particle density fluctuation downstream of a bent pipe is decomposed into the time-space levels in a non-choking state and a pseudo-choking state. The proposed method enables realization of the time and position at which particle density fluctuations with respect to dominant time-space levels pass through the pipeline.

Underwater Acoustic Communication System Based on MC-MFSK

2014 ◽  
Vol 556-562 ◽  
pp. 4897-4900 ◽  
Author(s):  
Chun Xian Gao ◽  
Hong Xing Yang ◽  
Fei Yuan ◽  
En Cheng
Keyword(s):  
Frame Structure ◽  
Underwater Acoustic Communication ◽  
Water Pool ◽  
The Core ◽  
System A ◽  
Time Space ◽  
Class D ◽  
Space Frequency ◽  
Hardware Circuit ◽  
Information Frame

For the time-space-frequency varying shallow water acoustic channel, we designed a multi-carrier FH-MFSK system, so that it can be reliably transmitted over these channels. This paper also design of a wake-up signal, and synchronization obtain information frame structure, the simulation result of the algorithm is presented. In the core of DSPC6747 chip, with class D power amplifier, we designed a reasonable layout, stable and reliable hardware circuit. By simulation, adding noise experiments, and water pool experiments verify the good performance of the system, a very low bit error rate (BER) communications were archived.

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