scholarly journals From high temporal resolution to synthetically enhanced radiometric resolution: insights from Night Thermal Gradient results

2021 ◽  
Vol 230 (1) ◽  
pp. 111-132 ◽  
Author(s):  
L. Piroddi
Keyword(s):  
Data Processing ◽  
Temporal Resolution ◽  
Seismic Activity ◽  
Thermal Gradient ◽  
Central Italy ◽  
Low Frequency ◽  
Thermal Infrared ◽  
High Temporal Resolution ◽  
Electromagnetic Emissions ◽  
Frequency Components

Abstract Electromagnetic emissions in thermal infrared bands are an important research topic on pre-earthquake studies. Satellite thermal data have been investigated by many independent research groups looking for their anomalous behaviour before main earthquake's occurrences. Among them, geosynchronous satellite data are reported as less prone to artefacts during data processing. In this work, the Night Thermal Gradient (NTG) algorithm is presented, which has been specifically proposed for geostationary thermal infrared data processing. NTG method relies on the exploitation of high temporal resolution data to find coherent low frequency components of a hypothetical precursory signal of seismic activity. In this paper, the method is presented by giving details about the applied procedures, steps, theoretical assumptions and results obtained during the studies of L'Aquila 2009 earthquake and the seismic activity of Central Italy and Sardinia.

scholarly journals Study of electromagnetic emissions associated with seismic activity in Kamchatka region

2001 ◽  
Vol 1 (3) ◽  
pp. 127-136 ◽  
Author(s):  
V. Gladychev ◽  
L. Baransky ◽  
A. Schekotov ◽  
E. Fedorov ◽  
O. Pokhotelov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Data Processing ◽  
Seismic Activity ◽  
Electromagnetic Emission ◽  
Kamchatka Peninsula ◽  
Kamchatka Region ◽  
Radio Transmitters ◽  
Electromagnetic Emissions ◽  
Telluric Currents ◽  
Elf Magnetic Field

Abstract. A review of data processing of electromagnetic emission observation collected at the Complex Geophysical Observatory Karimshino (Kamchatka peninsula) during the first 5 months (July–November, 2000) of its operation is given. The main goal of this study addresses the detection of the phenomena associated with Kamchatka seismic activity. The following observations have been conducted at CGO: variations of ULF/ELF magnetic field, geoelectric potentials (telluric currents), and VLF signals from navigation radio transmitters. The methods of data processing of these observations are discussed. The examples of the first experimental results are presented.

scholarly journals Small Unmanned Aircraft (sUAS)-Deployed Thermal Infrared (TIR) Imaging for Environmental Surveys with Implications in Submarine Groundwater Discharge (SGD): Methods, Challenges, and Novel Opportunities

2021 ◽  
Vol 13 (7) ◽  
pp. 1331
Author(s):  
Kyle S. R. Young ◽  
Soni M. Pradhanang
Keyword(s):  
Temporal Resolution ◽  
Submarine Groundwater Discharge ◽  
New Technology ◽  
Empirical Studies ◽  
Groundwater Discharge ◽  
Data Gathering ◽  
Thermal Infrared ◽  
Unmanned Aircraft ◽  
High Temporal Resolution ◽  
Submarine Groundwater

Submarine Groundwater Discharge (SGD) represents a significant mode of chemical transport to water bodies, making it an important flux to understand. Small Unmanned Aircraft Systems-deployed thermal infrared sensors (sUAS-TIR) provide a financially and logistically inexpensive means of identifying SGD source zones and quantifying SGD thermal infrared (TIR) plume areas over regional scales at high spatial resolutions. sUAS-TIR additionally offers the unique capability of high temporal resolution measurements of SGD. As a developing science application, the use of sUAS-TIR to image SGD requires substantial background knowledge. We present a proposed methodological construct for implementing a sUAS-TIR program for SGD-TIR data gathering, with applications extending to other research fields that can benefit from airborne TIR. Several studies have used airborne TIR in combination with empirical SGD flux measurements to quantify SGD, reporting a consistently strong regression between SGD flux and SGD TIR plume area. We additionally discuss novel research opportunities for sUAS-TIR technologies, as applied to SGD flux. The combination of high spatial and temporal resolution capabilities, at relatively low costs, make sUAS-TIR a promising new technology to overcome the scaling challenges presented by empirical studies and modeling of SGD fluxes, and advance our understanding of the controls on SGD fluxes.

scholarly journals The ultra low frequency electromagnetic radiation observed in the topside ionosphere above boundaries of tectonic plates

2015 ◽  
Vol 4 (1) ◽  
Author(s):  
Michael A. Athanasiou ◽  
Gergios C. Anagnostopoulos ◽  
Constantinos N. David ◽  
Gregorios G. Machairides
Keyword(s):  
Electromagnetic Radiation ◽  
Seismic Activity ◽  
Eastern Mediterranean ◽  
Singular Spectrum Analysis ◽  
Low Frequency ◽  
Topside Ionosphere ◽  
Tectonic Plates ◽  
Electromagnetic Emissions ◽  
Eastern Mediterranean Basin ◽  
Electric Field Instrument

In this paper we present results of a comparison between ultra low frequency (ULF) electromagnetic (EM) radiation, recorded by an electric field instrument onboard the satellite detection of electromagnetic emissions transmitted from earthquake regions in the topside ionosphere, and the seismicity of regions with high and low seismic activity. In particular, we evaluated the energy variations of the ULF Ezelectric field component during a period of four years (2006-2009), in order to examine the possible relation of ULF EM radiation with seismogenic regions located in Central America, Indonesia, the Eastern Mediterranean Basin and Greece. As a tool for evaluating the ULF Ez energy variations we used singular spectrum analysis techniques. The results of our analysis clearly show a significant increase of the ULF EM energy emitted from regions of highest seismic activity at the boundaries tectonic plates. Furthermore, we found that higher electromagnetic radiation was detected in a region above the northern- western Greek Arc (R1) than above the adjacent region including Athens and its urban area. We interpret these results of the present study as suggesting that: i) the seismogenic regions at the boundary of tectonic plates radiate ULF EM emissions observed by satellites in the topside ionosphere; and ii) that this EM radiation is not only related with the occurrence time of great (M≥5) earthquakes, but it is often present in intermediate times and it appears as a quasi-permanent phenomenon.

scholarly journals Modifying an Image Fusion Approach for High Spatiotemporal LST Retrieval in Surface Dryness and Evapotranspiration Estimations

2020 ◽  
Vol 12 (3) ◽  
pp. 498 ◽  
Author(s):  
Tri Wandi Januar ◽  
Tang-Huang Lin ◽  
Chih-Yuan Huang ◽  
Kuo-En Chang
Keyword(s):  
Spatial Resolution ◽  
Temporal Resolution ◽  
Air Temperature ◽  
Land Surface ◽  
Thermal Infrared ◽  
Satellite Observations ◽  
High Temporal Resolution ◽  
Landsat 8 ◽  
Fusion Model ◽  
Spatiotemporal Resolution

Thermal infrared (TIR) satellite images are generally employed to retrieve land surface temperature (LST) data in remote sensing. LST data have been widely used in evapotranspiration (ET) estimation based on satellite observations over broad regions, as well as the surface dryness associated with vegetation index. Landsat-8 Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) can provide LST data with a 30-m spatial resolution. However, rapid changes in environmental factors, such as temperature, humidity, wind speed, and soil moisture, will affect the dynamics of ET. Therefore, ET estimation needs a high temporal resolution as well as a high spatial resolution for daily, diurnal, or even hourly analysis. A challenge with satellite observations is that higher-spatial-resolution sensors have a lower temporal resolution, and vice versa. Previous studies solved this limitation by developing a spatial and temporal adaptive reflectance fusion model (STARFM) for visible images. In this study, with the primary mechanism (thermal emission) of TIRS, surface emissivity is used in the proposed spatial and temporal adaptive emissivity fusion model (STAEFM) as a modification of the original STARFM for fusing TIR images instead of reflectance. For high a temporal resolution, the advanced Himawari imager (AHI) onboard the Himawari-8 satellite is explored. Thus, Landsat-like TIR images with a 10-minute temporal resolution can be synthesized by fusing TIR images of Himawari-8 AHI and Landsat-8 TIRS. The performance of the STAEFM to retrieve LST was compared with the STARFM and enhanced STARFM (ESTARFM) based on the similarity to the observed Landsat image and differences with air temperature. The peak signal-to-noise ratio (PSNR) value of the STAEFM image is more than 42 dB, while the values for STARFM and ESTARFM images are around 31 and 38 dB, respectively. The differences of LST and air temperature data collected from five meteorological stations are 1.53 °C to 4.93 °C, which are smaller compared with STARFM’s and ESATRFM’s. The examination of the case study showed reasonable results of hourly LST, dryness index, and ET retrieval, indicating significant potential for the proposed STAEFM to provide very-high-spatiotemporal-resolution (30 m every 10 min) TIR images for surface dryness and ET monitoring.

scholarly journals Relationship between Seismic Activity and Variations in the Earth’s Rotation Angular Velocity

2018 ◽  
Vol 10 (2) ◽  
pp. 43 ◽  
Author(s):  
Elena Sasorova ◽  
Boris Levin
Keyword(s):  
Angular Velocity ◽  
Seismic Activity ◽  
Low Frequency ◽  
Rotation Velocity ◽  
Seismic Events ◽  
Earth’S Rotation ◽  
Earth's Rotation ◽  
The Earth ◽  
Frequency Components ◽  
New Phase

The Earth's seismic activity (SA) demonstrates a distinct unevenness both in space and in time. The periods of intensification of seismic activity are followed by periods of its decline. In this work, an attempt was first made to determine the effect of low-frequency components of the variations in the angular velocity of the Earth's rotation (AVER) on the dynamics of its seismic activity (for 1720 – 2017). Analysis of the time series of the density of seismic events and variations in the Earth's rotation velocity of about 300 years shows that each stage of reducing the angular velocity of rotation (braking) is accompanied by an increase in the density of seismic events, and the stages of increasing the angular velocity of rotation (acceleration) are accompanied by a decrease in the density of events. At present, the Earth is entering a new phase of deceleration (since 2005), which in recent years has already led to an increase in the global seismic activity.

scholarly journals Investigate the Frequency Spectrum of Noise Signals Affecting Synchronous Signals of fMRI and fNIRS in Resting and Moving Wrists

2019 ◽  
Author(s):  
Yousef Naderi Khojasteh far ◽  
Nader Riahi Alam ◽  
Maziar Jalalvandi ◽  
Hasan Hashemi
Keyword(s):  
Temporal Resolution ◽  
Near Infrared ◽  
Cerebral Arteries ◽  
Low Frequency ◽  
High Temporal Resolution ◽  
Functional Near Infrared Spectroscopy ◽  
Low Frequencies ◽  
Temporal Features ◽  
Neurological Effects ◽  
Systemic Signals

Purpose: The nerve signals are often contaminated by the non-nerve signals in the same frequency range, i.e. low frequencies in the range of 0.1 Hz. Among the different medical imaging tools, Functional Magnetic Resonance Imaging (fMRI) has been widely used by scientists and scholars due to its high spatial resolution for brain mapping. Materials and Methods: Also, the use of Functional Near-Infrared Spectroscopy (NFIRS) has continued to rise and regarding its high temporal resolution, it is considered as the complement of FMRI. Results: However, the effect of non-nerve functions is observed in both methods. Specially, by showing that non-nervous Low Frequency Oscillations (LFOs) 1) are merely non-nervous, because they can be measured by the environmental NIRS; 2) their internal origin is close to the heart; 3) in comparison with the available LF models based on respiration and the merely non-nervous changes in heart, they are unique in their spatial and temporal features, it seems that the systemic signals are moving through the cerebral arteries. Conclusion: In this paper, LF Oscillations (LFOs) are compared with simultaneous NIRS/FMRI. Also, we discuss the non-neurological effects during simple motions of the wrist in FMRI showing that a significant portion of them, especially in motion state networks, are non-nerve and we measure the sensitivity of NIRS to non-neural LFOs through mapping of nerve and non-nerve LFOs with an extra high spatial and temporal resolution

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

Low-frequency radio recombination lines: observations and data processing

2017 ◽  
Vol 23 (1) ◽  
pp. 50-53
Author(s):  
A.A. Konovalenko ◽  
◽  
S.V. Stepkin ◽  
E.V. Vasilkovskiy ◽  
◽  
...  
Keyword(s):  
Data Processing ◽  
Low Frequency ◽  
Radio Recombination Lines
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