Scale Irregularities Research Articles

Study about the effects on range imaging for MEOSAR induced by ionospheric irregularity

Based on the mean arrival time and temporal broadening of pulsed waves propagating through turbulent media, this study investigates the ionospheric effects induced by irregularity on medium-earth-orbit synthetic aperture radar (MEOSAR) range imaging quality. Considering radar signal two-way propagating through ionosphere irregularity, an analysis model for ionospheric effects induced by irregularities on MEOSAR range imaging quality is established based on the system characteristics of MEOSAR and ionospheric irregularity parameters. The mode extends the application of pulsed waves propagating through turbulent media to the field of synthetic aperture radar (SAR), and it can be used to analyse the effects on MEOSAR induced by both background ionosphere and ionospheric irregularity. The degradation of range image quality, including deterioration of resolution and shift in the image, due to the ionospheric irregularities is analysed. It is found that the effects induced by ionospheric irregularities will be very serious when the inner and outer scales of ionospheric irregularities are small or the fluctuation is strong. Furthermore, the degradation of resolution and the shift of image will become more and more serious with the increase of SAR orbit height. The results can help to evaluate ionospheric irregularity effects on range imaging for MEOSAR and provide a foundation for the design of MEOSAR.

Dilatory and Downward Development of 3‐m Scale Irregularities in the Funnel‐Like Region of a Rapidly Rising Equatorial Plasma Bubble

AbstractThe equatorial plasma bubbles, once developed, grow nonlinearly into topside ionosphere, and simultaneous secondary instabilities lead to the development of shorter scale irregularities. The altitudinal growth and generation of smaller scale irregularities determine the spatio‐temporal occurrence and the intensity of ionospheric scintillations at wide spectrum of radio waves and have significant implications on the GNSS/Satellite Based Augmentation Systems. In this letter, we present a unique equatorial plasma bubble observation from equatorial atmosphere radar that provides hitherto undisclosed evidence for the smaller (3‐m) scale irregularities initially developing at higher altitudes and subsequently developing to lower altitudes in a narrow funnel‐like structure. The responsible mechanisms for early development of shorter scale irregularities in the topside and their subsequent development at lower altitudes are discussed in light of difference between the time scales of altitudinal growth and cascading rate of secondary instabilities through high‐resolution bubble model simulations.

Spatial and Temporal Evolution of Different‐Scale Ionospheric Irregularities in Central and East Siberia During the 27–28 May 2017 Geomagnetic Storm

AbstractWe present a multi‐instrumental study of ionospheric irregularities of different scales (from tens of centimeters to few kilometers) observed over the Central and East Siberia, Russia, during a moderate‐to‐strong geomagnetic storm on 27–28 May 2017. From high‐frequency (HF) and ultrahigh‐frequency (UHF) radar data, we observed an intense auroral backscatter developed right after the initial phase of the geomagnetic storm. Additionally, we examined variations of Global Positioning System (GPS)‐based ROT (rate of TEC changes, where TEC is total electron content) for available GPS receivers in the region. Ionosondes, HF, and UHF radar data exhibited a presence of intense multi‐scale ionospheric irregularities. We revealed a correlation between different‐scale Auroral/Farley‐Buneman ionospheric irregularities of the E layer during the geomagnetic storm. The combined analysis showed that an area of intense irregularities is well connected and located slightly equatorward to field‐aligned currents (FACs) and auroral oval at different stages of the geomagnetic storm. An increase and equatorward displacement of Region 1 (R1)/Region 2 (R2) FACs leads to appearance and equatorward expansion of ionospheric irregularities. During downward (upward) R1 FAC and upward (downward) R2 FAC, the eastward and upward (westward and downward) E × B drift of ionospheric irregularities occurred. Simultaneous disappearance of UHF/HF auroral backscatter and GPS ROT decrease occurred during a prolonged near noon reversal of R1 and R2 FAC directions that accompanied by R1/R2 FAC degradation and disappearance of high‐energy auroral precipitation.

Well-controlled dynamic hydrocarbon reserves calculation of fracture\u2013cavity karst carbonate reservoirs based on production data analysis

Fracture–cavity karst carbonate reservoirs have multiple storage space with irregular geometry and various scales, and this caused strong heterogeneity and complex flow characteristics. Accurately calculating the well-controlled dynamic reserves of this kind reservoir effectively is the basis to optimize oil field development plan and making the transformation measures of production well. In order to solve the problem that conventional well-controlled dynamic hydrocarbon reserves calculation method is not suitable for such type reservoirs, we applied a method based on production data analysis. Classification standard of oil well types is established based on the fracture–cavity reservoirs geological static and production dynamic characteristics. Conceptual characteristics of geological model and fluid flow pattern for different types of production wells are assumed. Calculation workflow for well-controlled reserves of fracture–cavity reservoir is established. In the process, some technical key points are proposed to improve accuracy of curve fitting, such as converting the bottom hole pressure from wellhead pressure, correcting the well control range and converting the PVT parameters at the pseudo-steady state. We verified correctness of this method by comparing the calculated results with numerical simulation results of actual production well. This method is well used to Tahe Oil field of Tarim Basin in China. The result shows that the well-controlled reserves quantitative calculation results through this method are in conformity with oil field actual understanding, and the remaining dynamic reserves mainly exist in the drainage area of the wells that drilled different reservoir bodies with good connectivity, especially at the top of large karst caves, and that is the target of further adjusting.

Power Spectrum in the Conductive Terrestrial Ionosphere

Stochastic differential equation of the phase fluctuations is derived for the collision conductive magnetized plasma in the polar ionosphere applying the complex geometrical optics approximation. Calculating second order statistical moments it was shown that the contribution of the longitudinal conductivity substantially exceeds both Pedersen and Hall’s conductivities. Experimentally observing the broadening of the spatial power spectrum of scattered electromagnetic waves which equivalent to the brightness is analyzed for the elongated ionospheric irregularities. It was shown that the broadening of the spectrum and shift of its maximum in the plane of the location of an external magnetic field (main plane) less than in perpendicular plane for plasmonic structures having linear scale tenth of kilometer; and substantially depends on the penetration angle of an incident wave in the conductive collision turbulent magnetized ionospheric plasma. The angle-of-arrival (AOA) in the main plane has the asymmetric Gaussian form while in the perpendicular plane increases at small anisotropy factors and then tends to the saturation for the power-low spectrum characterizing electron density fluctuations. Longitudinal conductivity fluctuations increase the AOAs of scattered radiation than in magnetized plasma with permittivity fluctuations. Broadening of the temporal spectrum containing the drift velocity of elongated ionospheric irregularities in the polar ionosphere allows to solve the reverse problem restoring experimentally measured velocity of the plasma streams and characteristic linear scales of anisotropic irregularities in the terrestrial ionosphere.

IDEASSat: A 3U CubeSat mission for ionospheric science

The Ionospheric Dynamics Exploration and Attitude Subsystem Satellite (IDEASSat/ INSPIRESat-2) is a three-unit (U) CubeSat developed with the objective of providing in-situ measurements of the Earth’s ionosphere in order to quantify both global scale ionospheric variability and small scale irregularities. The science payload is the Compact Ionospheric Probe (CIP) - an all in one in-situ plasma sensor developed at Taiwan National Central University (NCU), which is the miniaturized version of the larger Advanced Ionospheric Probe (AIP) that is carried and operational aboard the 450 kg FORMOSAT-5 spacecraft. The spacecraft has been developed by NCU in partnership with the International Satellite Program in Research and Education (INSPIRE) consortium, and is funded by the Taiwan National Space Organization (NSPO), Ministry of Science and Technology, and Ministry of Education as part of the first national effort to encourage small satellite development at Taiwan universities. The development of IDEASSat offers students a hands-on opportunity to learn about space science and technology and will work in conjunction with FORMOSAT-5 and INSPIRESat-1 to provide ionospheric observations spanning different altitudes and local times. The IDEASSat spacecraft subsystems are a combination of commercial off the shelf (COTS) and self-developed components designed by NCU in partnership with other INSPIRE member universities. IDEASSat is expected to be launched in late 2020. In this report, we describe the IDEASSat mission and spacecraft design, as well as unique lessons learned as part of the development process.

Temporal variations of the ionospheric disturbances due to the seasonal variability over Turkey using IONOLAB-FFT algorithm

The ionosphere is exposed to forcing from below due to gravitational, geomagnetic and seismic activities, and above due to solar wind. These forces cause some medium and large scale irregularities and disturbances into the upper atmosphere and ionosphere. Some of these disturbances occur in the form of wave-like oscillations in the ionosphere which propagate at a certain frequency, duration and velocity. These disturbances can be detected by monitoring the ionosphere using Total Electron Content obtained from Global Positioning System (GPS-TEC). In this study, the temporal analysis of these disturbances due to the seasonal variability is carried out for a mid-latitude GPS network using Ionosphere Research Laboratory TEC (IONOLAB-TEC) over Turkey. The IONOLAB Fast Fourier Transform (FFT) algorithm is applied to GPS-TEC obtained from nine Turkish National Permanent GPS Network (TNPGN) active stations in Turkey for December (winter solstice), March (spring equinox), June (summer solstice), September (autumn equinox) months in 2010 (low solar activity), 2011 and 2012 (moderate solar activity). It is observed that the highest frequency accumulates around 0.2 mHz at morning and afternoon hours while it accumulates around 0.1 mHz at noon and night hours. The frequency increases from solar quiet year 2010 to solar quiet active year 2012. In all years, it is observed that most frequencies are grouped at higher frequencies for the equinox months. The lower frequencies are observed for the solstice months for all time intervals. The largest numbers of the durations accumulate around 100 min (1.66 h) for morning hours, 200 min (3.33 h) for noon hours, 200 min (3.33 h) for afternoon hours and 150 min (2.5 h) for night hours. After sunrise and sunset, the durations of the disturbances are shorter than those observed for noon and afternoon times. The duration shortens from solar quiet year 2010 to solar quiet active year 2012. The durations for equinox months are shorter than those for the solstice months.

Risk Assessment in the Transport of Hazardous Materials on the Example of the Greater Voivodeship

The main purpose of the paper is to assess the risk associated with the transport of hazardous materials. This goal was achieved by discussing theoretical information on this issue and the results of control of the transport of dangerous goods carried out by the Provincial Road Transport Inspectorate in Poznań in 2015-2017. The analysis showed that the scale of irregularities in the protection of dangerous goods transported, documentation and transport operations was very small. However, other violations were found relatively frequently. Nevertheless, both the total number of infringements found as well as their frequency were low. In relation to the above, it can be stated that the level of risk associated with the transport of hazardous materials in the Wielkopolskie Voivodship in the years 2015-2017 was very small, although the analysis allowed identification of certain areas requiring further improvement.

SAFETY AND QUALITY OF FOOD ON THE POLISH MARKET AFTER EUROPEAN UNION ACCESSION

The aim of this study is to investigate how the level of food safety and quality in Poland has changed after European Union accession. Poland’s accession to EU structures resulted in a number of economic, market and environmental changes. One of the most important areas of these changes is the food production and consumer supply sector. The conducted research is based on the results of controls performed by the main food control institutions in Poland. Research covers the areas of food quality and scale of irregularities revealed by control institutions, leading to changes in the level of food safety in terms of the health threats and economic security of consumers resulting from food falsification. Studies have shown that in the post-accession period, significant and multidirectional changes in the above-mentioned scope have taken place. Despite the proven presence of food with improper sanitary conditions, the Polish consumer is unlikely to be concerned about this. The situation is much worse in terms of economic security and food quality. The scale of irregularities in this respect is significant, and as the last years of the analyzed period show (after 2015), the phenomenon of decreasing food quality and even food falsification is growing.

Entropy-Based Local Irregularity Detection for High-Speed Railway Catenaries With Frequent Inspections

The condition-based maintenance of high-speed railway catenary is an important task to ensure the continuous availability of train power supply. To improve the condition monitoring of catenary, this paper presents a novel scheme to detect catenary local irregularities using pantograph head acceleration measurements. First, a series of experimental inspections is carried out in a section of the Beijing-Guangzhou high-speed line in China. The time intervals between the inspections are shortened from the traditional six months to about 40 days, which enables monitoring the short-term degradation of local irregularities. Then, based on the wavelet packet entropy, an approach is proposed to detect local irregularities with different scales in length. Criteria for identifying and verifying the local irregularities are established based on the gradient and repeatability of entropy from multiple measurements. Results from the experimental inspections show that different scales of local irregularities can be detected by the proposed scheme. By using frequent inspections, local irregularities can be effectively verified after about seven inspections. The spatial distribution of local irregularities is found to be closely related to the catenary structure. These findings provide valuable information to deploy the scheme for a railway network.

Statistical features of TEC and ionospheric scintillation over the low latitude of China

In this paper, a new index is established which is defined by the standard deviation of total electron content (TEC) fluctuation and denoted by the symbol σtec. It is demonstrated that the index σtec is equivalent to the phase scintillation index and can serve as an indicator of the strength of the phase scintillation. The receiver transiently loses lock on the signal, leading to cycle slips and jumps in the TEC time series. In order to obtain continuous TEC data in the situation of the disturbed ionosphere, a batch processing method is developed to detect and correct cycle slip. Based on the methods mentioned above, we investigate the statistical features of the phase scintillations and cycle slips by means of the data from a scintillation observation network in the south-central region of China during 2012–2015. The results show that the variations of phase scintillation occurrences with local time and season display very similar features to those of the cycle slip occurrences, implying that cycle slips are closely related to phase scintillations. Phase scintillations occur mainly during the night, most frequently before midnight and seldom in the daytime. It is found that phase scintillations occur mainly in equinox months but seldom in solstice months in the crest of the ionization equatorial anomaly and its adjacent regions, and an equinoctial asymmetry that phase scintillations occur more frequently in Spring than in Autumn is also found. Besides, a comparison of the TEC fluctuation index (σtec) and amplitude scintillation index (S4) indicates that there is close relation between the σtec and S4, indicating the co-existence of large and small scale irregularities in equatorial irregularity structures.

Scaling Fractal-Chuan Fractance Approximation Circuits of Arbitrary Order

The scaling fractal-chuan fractance approximation circuit (SFCFAC), which can realize the rational approximation of arbitrary-order fractances and has an excellent approximation performance, is presented in this paper. For an original SFCFAC, the progression ratios of resistance and capacitance are limited to the range 0–1. However, it is possible for the values of both progression ratios to be greater than one. The impedance function of an SFCFAC can be represented by an irregular scaling equation. By solving the scaling equation approximately, the operational order of an SFCFAC can be obtained using both progression ratios as $$\mu = -\lg \alpha /\lg (\alpha \beta )$$ . Therefore, the SFCFAC has fractional operational characteristics, which is explained in theory. Oscillation phenomena are inherent to the SFCFAC. It is necessary to learn about these oscillation characteristics. The approximation performance can be improved by adding a series resistor and a series capacitor to the SFCFAC. The corresponding resistance and capacitance are determined by both progression ratios. The optimization has the advantages of simple operation, evident influence, and good practicality, which will make the SFCFAC competitive in future studies. Moreover, the values of the operational order of SFCFACs are extended from $$-1<\mu <0$$ to $$0<|\mu |<2$$ without using inductors, which is feasible for practical applications.

Using a 2D shallow water model to assess Large-Scale Particle Image Velocimetry (LSPIV) and Structure from Motion (SfM) techniques in a street-scale urban drainage physical model

Physically-based numerical modelling of surface processes in urban drainage, such as pollutant wash-off or the assessment of flood risks, requires appropriate calibration and terrain elevation data to properly simulate the overland flows and thus to achieve useful results. Accordingly, this study aims to obtain an accurate representation of the runoff generated by three different rain intensities, 30, 50 and 80 mm/h, in a full-scale urban drainage physical model of 36 m2. The study focuses firstly on applying the Structure from Motion (SfM) photogrammetric technique to carry out a high-resolution and accurate topographic survey. This topography was implemented in a 2D shallow water model and the results were compared with those obtained using traditional data point measured topography. Negligible differences were found when comparing the two models with measured discharges at the physical model gully pots. However, significant differences were obtained in the velocity distributions, especially in the shallowest flow areas where drainage channels of a few millimeters’ depth appeared in the high resolution topographic survey. Results from the numerical model were compared with overland flow velocities, determined by applying a modified Large Scale Particle Image Velocimetry (LSPIV) methodology using fluorescent particles. With the SfM topography, the 2D model was able to obtain a better representation of the experimental data, since small scale irregularities of the pavement surface could be represented in the model domain. At the same time, LSPIV was presented as a very suitable tool for the accurate measurement of runoff velocities in urban drainage models, avoiding the interference of raindrop features in the recorded images and with overland water depths in the order of few millimeters.

Rayleigh-Taylor Instability Development in the Equatorial Ionosphere and a Geometry of an Initial Irregularity

In this paper, we performed a numerical simulation for the conditions of the equatorial F‑region of the Earth’s ionosphere using the two-dimensional electrodynamically consistent mathematical MI2 model. The development time of ionospheric bubbles is shown to depend sufficiently strongly on the vertical scale and less strongly on the horizontal scale of the initial irregularity. Ionospheric bubbles developed more slowly at the generation of instability by increasing the plasma concentration than by depleting a plasma. On increasing the initial irregularity scale, three metric thresholds are experimentally found.

An intelligent monitoring system for indoor safety of individuals suffering from Autism Spectrum Disorder (ASD)

Autism Spectrum Disorder (ASD) is distinguished by a variety of behavioral and social deficits. One of the most prominent problems in an autistic child is their aggressive nature that can cause physical injuries. In order to address the following behavioral deficits, this paper is an attempt to present a novel monitoring framework to predict irregularities from the physical activities of an autistic child. The primary motive behind this study is to improve the safety measures for the child in an indoor environment by generating time sensitive-alerts for caretakers and doctors. In this study, a deep 3D CNN and LSTM based activity prediction methodology are proposed to recognize physical irregularities. The 3D CNN model extracts the spatio-temporal features from the video templates for stance prediction with subject position. The LSTM model calculates the temporal relationship in the feature maps to analyze the scale of irregularity. Moreover, in order to deal with such irregularities, a time-sensitive alert-based decision process is proposed in the present work to generate early warnings to the doctor and caretaker. The proficiency of the system is increased by storing the performed activity scores in the local database of the system which can be further utilized to provide medicinal or therapeutic assistance. In addition, the measured experimental results are validated with state-of-the-art methodologies. Hence, the calculated statistical measures justify the utility of the proposed study in the healthcare and assistive-care domain.

Effect of Magnetic Storm Related Thermospheric Changes on the Evolution of Equatorial Plasma Bubbles

AbstractPast efforts to predict scintillations on VHF and L‐band radio signals recorded at equatorial and low‐latitude stations have been mostly based on a theoretical linear growth rate of Rayleigh‐Taylor instability on the bottomside of the post‐sunset equatorial F layer, which is responsible for the generation of an equatorial plasma bubble (EPB). However, it is the maximum height that an EPB reaches above the dip equator and development of intermediate scale irregularities within the EPB, in its nonlinear phase of evolution that determines the latitudinal distribution of scintillations. Amplitude scintillations recorded by a network of VHF and L‐band receivers on a quiet day, 13 March 2015 and on 20 March 2015, a few days after the 17 March 2015 magnetic storm, show that latitudinal extent of scintillations caused by EPB irregularities is lesser on 20 March than on 13 March. Geomagnetic and ionosonde data from an equatorial station, and vertical total electron content distributions obtained from Global Navigation Satellite Systems observations, indicate that the equatorial ionospheric conditions are approximately same on these 2 days. Simulation of thermospheric conditions for these 2 days is carried out using the Coupled Thermosphere, Ionosphere, Plasmasphere, and Electrodynamics model. It is found that thermospheric atomic oxygen density is enhanced in the aftermath of the major magnetic storm of 17 March 2015, resulting in enhanced ion‐neutral collision frequencies over the dip equator on 20 March. This limits the height to which an EPB rises over the dip equator on this day, and thus impacts the latitudinal distribution of scintillations.

Complete-closed time scales under shifts and related functions

In this paper, we introduce the concept of complete-closed time scales under translational and non-translational shifts and propose new definitions of special functions arising from dynamic equations on time scales including the concepts of almost periodic functions, almost automorphic functions and Stepanov almost automorphic functions. All the functions introduced in the paper are not only effective on periodic time scales under translations but are also valid on irregular time scales like overline{q^{mathbb{Z}}}, overline{(-q)^{mathbb{Z}}} and mathbb{N}^{frac{1}{2}}_{pm }, etc.

Density disturbance of small-scale field-aligned irregularities in the ionosphere heating experiments

A theoretical model which describes the small-scale irregularities excited by powerful high frequency (3–30 MHz) electromagnetic wave in ionosphere heating is investigated quantitatively in this paper. The model is based on the transport equation in magnetic plasma and mode conversion from electromagnetic wave to electrostatic wave in ionospheric modification. Threshold electric field for exciting small-scale (meter scale) irregularities and spatial spectra of irregularities are analytically calculated by this model. The results indicate that background electron density and geomagnetic field play an important role for the threshold electric field and the spatial scale of the electron density irregularities. The results demonstrate that the electric field threshold increases with the decrease of the spatial scale of the irregularities. For exciting meter scale irregularities, the threshold electric field is about tens of mV m−1. The theoretical results are consistent with those of the experiments.

Growth of L-band scintillation at anomaly crest station in association with strong TEC gradient: A study covering wide solar activity period

The paper aims at to study the sources associated with growth of L band scintillation over Guwahati, an Appleton anomaly region. Starting with the analysis of diurnal and seasonal characteristic features of scintillation from a minimum sunspot number (Rz) of 10 to a maximum of 140, the paper shows that scintillations are more likely to develop during high solar activity period. It also highlights the explosive increase in occurrence of scintillation from post sunset to pre midnight hours in vernal equinoctial months when the background TEC is 50% more than on a normal day, accompanied by enhanced TEC decay rate. The role of equatorial anomaly effects through EXB drift processes are brought into discussion as possible sources on the growth of small scale irregularities leading to such scintillations.

Multi-scale flow simulation in fracture-vuggy reservoirs based on pseudo-particle method

Fracture-vuggy reservoirs have multiple storage space with irregular geometry and various scales, the scales ranges from a few microns to tens of meters. There are many flow states in the reservoir, such as fluid flow in porous medium, free flow in cave and fractures. Physical simulation and conventional numerical simulation methods difficult to accurately describe the flow characteristics of such reservoirs. In this paper, we use two phase flow multi-scale pseudo-particle discrete calculation model for flow simulation of such reservoirs. This model characterised the surface tension through introducing a repulsion between two phase interfaces, simulated wettability by introducing the force of Lennard-Jones form. The results shows that this method can simulate fluid flow of such reservoir well, determined the types and distribution of macroscopic remaining oil with different fracture-cave combination, supplied basis for further development remaining oil of this kind of reservoirs. [Received: January 29, 2016; Accepted: June 7, 2017]