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In order to address the non-Fourier heat conduction phenomena for thermomass gas flow, the aim of the present contribution is to construct a new theory of generalized thermoelasticity for thermomass gas flow assimilating low velocity and linear resistance based on the generalized non-Fourier theory of heat conduction with memory responses. The effect of resistance has been included in the general heat conduction equation, which is based on the total derivative of the thermomass gas velocity. The constitutive equation has been formulated using the nonlocal theory proposed by Eringen. The governing equations have been solved for a thermoelastic rod, where both the boundary is free of traction and the left boundary is subjected to a thermal shock, while on the right boundary, there is no temperature. The problem is solved by means of the Laplace transform mechanism. In order to achieve the solutions in real space-time domain, a viable simulation has been carried out for the numerical inversion of the Laplace transform using the method of Zakian. The latest findings illustrate the contrasts between different kernel function of the heat transport process. The stability of the proposed model has been validated. The numerical results validate the superiority of the present revolutionary thermoelastic model over the existing one. The superiority of non-local behavior is also reported to accommodate the effect of thermomass within the medium. Finally, it may be said that it is beneficial to formulate the heat transport law involving various kernel as per the necessity of the physical situation. [ABSTRACT FROM AUTHOR]

Equatorial Plasma Bubbles (EPBs) are zones characterized by fluctuations in plasma densities which form in the low-latitude ionosphere primarily during the post-sunset. They subject radio signals to amplitude and phase variabilities, affecting the functioning of technological systems that utilize the Global Navigation Satellite Systems (GNSS) signals for navigation. Thus, understanding EPB occurrence patterns and morphological features is vital for mitigating their effects. In this work, we employed two GNSS receivers and an All-Sky Imager (ASI) to conduct simultaneous observations on the morphology of EPBs over Brazil. The main objectives of the study were (1) to develop a Random Forest (RF) machine-learning model to estimate and predict the zonal drift velocities of EPBs, and (2) to compare the model predictions with actual EPB drifts inferred from the two instruments, as well as zonal neutral wind speeds obtained from the Horizontal Wind Model (HWM-14). In the model development, we utilized reliable EPB drift measurements made during geomagnetically quiet days between 2013 and 2017 in Brazil. The model predicted the velocities based on parameters including the day of the year, universal time, critical frequency of the F2 layer (foF2), solar and interplanetary indices. The correlation coefficients of 0.98 and 0.96 and RMSE values of 10.61 m/s and 10.06 m/s were obtained upon training and validation correspondingly. We evaluated the accuracy of the model in predicting EPB drifts on two geomagnetically quiet nights where an average correlation coefficient of 0.89 and an RMSE of 15.74 m/s were obtained. The predicted drifts, the zonal neutral wind velocities, and the GNSS and ASI velocity measurements were put into context for validation purposes. Overall, the velocities were comparable and ranged between ∼100 m/s and ∼30 m/s from the hours of 00 UT to 05 UT. The results confirmed the accuracy and applicability of the model, revealing the ionosphere-thermosphere coupling influence on the nocturnal propagation of EPBs under the full activation of the F region dynamo. [ABSTRACT FROM AUTHOR]

In this paper, a new model of a nanobeam of silicon nitride based on thermomass motion and the generalized thermoviscoelasticity theory is used. Ramp-type heat conduction has thermally loaded a simply supported thermoviscoelastic nanobeam. The governing equations have been constructed and solved in the Laplace transform domain. The numerical results have been represented in figures to show the effects of the thermoviscoelastic, drift velocity, and ramp-time heat parameters. Mechanical relaxation time has a significant impact on the mechanical wave. Moreover, the drift velocity and ramp-time heat parameters significantly affect all the studied functions. [ABSTRACT FROM AUTHOR]

The recurring occurrence of green tides as an ecological disaster has been reported annually in the Yellow Sea. While remote sensing technology effectively tracks the scale, extent, and duration of green tide outbreaks, there is limited research on the underlying driving mechanisms of green tide drift transport and the determination of the leeway coefficient. This study investigates the green tide transport mechanism and evaluates the feasibility of estimating the leeway coefficient by analyzing green tide drift velocities obtained from Geostationary Ocean Color Imager-II (GOCI-II) images using the maximum cross-correlation (MCC) technique and leeway method across various time intervals alongside ocean current and wind speed data. The results reveal the following: (1) Significant spatial variations in green tide movement, with a distinct boundary at 34°40′N. (2) Short-term green tide transport is primarily influenced by tidal forces, while wind and ocean currents, especially the combined Ekman and geostrophic current component, predominantly govern net transport. (3) Compared to 1, 3, and 7 h intervals, estimating the leeway coefficient with a 25 h interval is feasible for moderate-resolution geostationary images, yielding values consistent with previous studies. This study offers new insights into exploring the transport mechanisms of green tides through remote sensing-driven velocity. [ABSTRACT FROM AUTHOR]

This paper introduces a Triangle Network‐Joint Slope (TN‐JS) approach to characterize the spatial and temporal dynamics of Equatorial Plasma Bubbles (EPBs) during geomagnetic storms. To collaboratively determine the EPB drift directions from multiple stations, a Delaunay triangle network is constructed, utilizing the distribution of Ionospheric Piercing Points (IPPs). The Time Difference of Arrival (TDOA) is extracted through cross‐correlating the Rate of Total Electron Content (ROT). The EPB drift direction can be approximately calculated by considering TDOA and IPP distances within each individual triangle of the network. This calculation is then refined through a joint statistical analysis. Using a reference station as the origin, the remaining stations within the network are projected along the estimated EPB drift direction. A spatial‐temporal color map illustrating regional ionospheric anomaly ROT observations is constructed. The EPB drift velocity among multiple stations can be collectively estimated by fitting the slope of this map, facilitating outlier exclusion. Accounting for satellite dynamic effects and the diverse orbit characteristics of GPS and BDS, corresponding IPP scan velocity compensation is performed and analyzed for EPB dynamic estimation. Using the geomagnetic storm event that occurred on September 8 as a case study, the spatial‐temporal kinetic properties of EPBs is characterized by analyzing Global Navigation Satellite System (GNSS) observations from 17 Hong Kong monitoring stations with the proposed TN‐JS approach. The results indicate during this magnetic event, that EPBs exhibit a westward drift trend with velocities ranging from a few tens to hundreds of meters per second in GPS and BDS observations. Plain Language Summary: Total Electron Content (TEC) is a path integrated electron density and its rate (ROT) of change reflect the ionospheric disturbance during magnetic storms. This article introduces a new method called Triangle Network‐Joint Slope (TN‐JS) to study the movement of Equatorial Plasma Bubbles (EPBs). TN‐JS uses a network of GNSS monitoring stations to determine the drift velocity of EPBs. By resampling ROT correlation using triangulation along the drift direction, TN‐JS transforms traditional EPB dynamic estimation into image processing of the color‐coded ROT maps. The TN‐JS algorithm is tested with data collected from 17 monitoring stations around Hong Kong during a geomagnetic storm on 8 September 2017 to show EPBs drifting westward at speeds ranging from tens to hundreds of meters per second. Key Points: A Delauny Triangle Network is built for statistically inferring EPB drift velocity by cross‐correlating and slope fitting multi‐sites' ROTThe orbit diversity offered by GPS MEO and BDS GEO/IGSO satellites provides measures of ionospheric irregularities inhomogeneityThe analysis unveiled a significant EPB westward drift event with a speed exceeding 500 m/s during the 2017 geomagnetic storm over Hong Kong [ABSTRACT FROM AUTHOR]

Studying the nature of the occurrence and propagation of microseismic tremors has not lost its relevance over the past few decades. Currently, the analysis of microseisms is the basis of some engineering and geological studies, including those aimed at the inspection of structures of various purposes. The procedure for preparing and conducting surveys is governed by a system of regulatory documents. However, the current codes and specifications represent a general guide for assessing the operational properties of building structures. Therefore, specific survey methods need to be clarified and detailed. Describes the experiment of examining the building regarding the dynamics of frequency characteristics within 24 hours. The observation system was implemented in the form of 16 points, evenly distributed over the volume of the building. Spectral analysis based on FFT was carried out to identify the time intervals within the 24-hour period with a pronounced maximum and minimum level of man-induced impact on the studied subject. During the hours of maximum exposure, the spectra were correlated according to records of different duration in terms of the correspondence of frequency components. The necessary and sufficient duration of registration of microseismic vibrations was derived to determine the frequency of natural vibration of a building when the observation points are located on the lower and upper floors.

Uranus is one of the least explored planets in our solar system, it exhibits a unique magnetic field structure which was observed by NASA's Voyager 2 mission nearly 50 years ago. Notably, Uranus displays extreme magnetic field asymmetry, a feature exclusive to the icy giants. We use the Boris algorithm to investigate how high energy protons behave within this unusual magnetic field, which is motivated by Voyager 2's observation of lower‐than‐expected high energy proton radiation belt intensities at Uranus. When considering full drift motions of high energy protons around Uranus, the azimuthal drift velocity can vary by as much as 15% around the planet. This results in areas around Uranus where particles will be more depleted (faster drift) and other regions where there is a surplus of particles (slower drift). This could provide a partial explanation for the "weak" proton radiation belts observed by Voyager 2. Plain Language Summary: In 1986, Voyager 2 made history as the first spacecraft to fly by Uranus, offering humanity unprecedented insights into the distant icy giant. This mission revealed to us the unique magnetic field of the planet. Typically, planets with strong magnetic fields can capture high energy charged particles from space and trap them around the planet. While being trapped within the magnetic field, the particles will slowly drift around the planet, forming what are known as "radiation belts". The radiation belts of Uranus are of particular interest to us as the Voyager 2 flyby indicated that they were much weaker than expected despite the strong magnetic field presence. We suggest that this could be explained by the unique magnetic field structure causing variations in the speed at which particles drift around the planet. This would create regions where particles are packed closer together and other regions where they are more spread‐out; we show Voyager 2 flew past a region where particles were more spread‐out. At the time of writing, a new mission to Uranus is being planned, and so this new idea could be one of many that will be tested by a future mission to the outer planets. Key Points: Asymmetry in Uranus' magnetic field causes variations in the azimuthal drift component which is most significant for high energy protonsThis drift velocity profile results in regions where there can be a surplus or depletion of protonsVoyager 2's measurement of weak proton radiation belts at Uranus could be partially explained by this phenomenon [ABSTRACT FROM AUTHOR]

Abstract Uranus is one of the least explored planets in our solar system, it exhibits a unique magnetic field structure which was observed by NASA's Voyager 2 mission nearly 50 years ago. Notably, Uranus displays extreme magnetic field asymmetry, a feature exclusive to the icy giants. We use the Boris algorithm to investigate how high energy protons behave within this unusual magnetic field, which is motivated by Voyager 2's observation of lower‐than‐expected high energy proton radiation belt intensities at Uranus. When considering full drift motions of high energy protons around Uranus, the azimuthal drift velocity can vary by as much as 15% around the planet. This results in areas around Uranus where particles will be more depleted (faster drift) and other regions where there is a surplus of particles (slower drift). This could provide a partial explanation for the “weak” proton radiation belts observed by Voyager 2.

The recurring occurrence of green tides as an ecological disaster has been reported annually in the Yellow Sea. While remote sensing technology effectively tracks the scale, extent, and duration of green tide outbreaks, there is limited research on the underlying driving mechanisms of green tide drift transport and the determination of the leeway coefficient. This study investigates the green tide transport mechanism and evaluates the feasibility of estimating the leeway coefficient by analyzing green tide drift velocities obtained from Geostationary Ocean Color Imager-II (GOCI-II) images using the maximum cross-correlation (MCC) technique and leeway method across various time intervals alongside ocean current and wind speed data. The results reveal the following: (1) Significant spatial variations in green tide movement, with a distinct boundary at 34°40′N. (2) Short-term green tide transport is primarily influenced by tidal forces, while wind and ocean currents, especially the combined Ekman and geostrophic current component, predominantly govern net transport. (3) Compared to 1, 3, and 7 h intervals, estimating the leeway coefficient with a 25 h interval is feasible for moderate-resolution geostationary images, yielding values consistent with previous studies. This study offers new insights into exploring the transport mechanisms of green tides through remote sensing-driven velocity.

The drift velocity of a particle under a driving force has its roots in the theory of electrical conduction. Although it has been studied for over 100 years, it still yields surprises. At the heart of a particle's drift velocity is an interplay of classical, quantum, and statistical mechanics. Irreversibility and energy loss have been assumed as essential features of drift velocities and very little effort has been made to isolate the aspects of particle transport that are due to elastic mechanisms alone. In this paper, we remove energy loss and quantum mechanics to investigate the classical and statistical factors that can produce a drift velocity using only elastic scattering. A Monte Carlo simulation is used to model a particle in a uniform force field, subject to randomly placed scatterers. Time-, space-, and energy-dependent scattering models, with varied ranges of scattering angles, are investigated. A constant drift velocity is achieved with the time scattering model, which has a constant average time between scattering events. A decreasing drift velocity is observed for space and energy-dependent models. The arrival of a constant drift velocity has to do with a balance of momentum gained between collisions and momentum lost after a collision. [ABSTRACT FROM AUTHOR]

An experimental study has been conducted on the effect of wind blowing on a wave induced by a wave generator in a direct channel. It is shown that with a small wave steepness and wind speed m/s, a drift current is generated on the water surface due to the action of viscous forces. A formula for calculating its velocity is proposed. It has been found that the phase velocity of the wave increases with the emergence of drift current and can be calculated by the formula obtained for linear waves in a flow with a constant velocity shear. With an increase in wave steepness and wind speed m/s, the formation of a vortex deforming the water surface over the wave crest was observed in the air flow over the wave crest. The vortex destroys the viscous layer, reducing the drift velocity. This also reduces the phase velocity and the length of the wave. A mechanism explaining this process has been proposed. [ABSTRACT FROM AUTHOR]

The influence of a water surface film composed of hydrophobic particles on the development of drift current under the effect of wind is investigated. In a uniform airflow on a flat water surface, the drift current is caused by viscous forces and increases along the fetch. The formation of stationary waves on the drift current has been observed when the drift velocity exceeds 0.23 m/s. In a decelerating airflow, in the presence of wind waves, the total component of the drift velocity cyclically increases and drops until it reaches the viscous component upon a steep wind wave breaking into longer linear waves. As the particle settling time increases, the maximum ratio of the wave component of the drift velocity to the total component decreases from 0.6 for clear water to 0.3 for days. [ABSTRACT FROM AUTHOR]

Motion of sediment particles in turbulent flows is usually a problem including multi-scale particle-turbulence interactions and is still far from being clearly understood. In this paper, an improved numerical method is proposed to describe the particle diffusion in inhomogeneous turbulent flows, in which the fluid motion is solved by the Reynolds-Averaged Navier–Stokes (RANS) equations while the particles are tracked with a Lagrange approach. For dilute problems, not only the inter-particle interactions but also the influence of particles on the fluid turbulence are all omitted. To simulate the stochastic motion of the sediment particles, a modified continuous random walk (CRW) model is employed, in which a highly effective correction to the particle drift is suggested to account for the effect of particle inertia. Enhancement of the particle velocity fluctuation due to vortex shedding in the particle wake is also taken into consideration. The model is then successfully verified through applying to the particle diffusion in steady turbulent pipe flows and to the suspension of neutrally buoyant as well as natural sediments in steady open-channel flows. The computational results are demonstrated to be in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

The influence of the external axial magnetic field on pinching plasma flows generated by a magnetoplasma compressor (MPC) has been studied using magnetic and electric probes. In the presence of an external magnetic field, temperature measurements show two groups of electrons with different temperatures near the plasma stream core. The external magnetic field leads to a noticeable increase in the electric current in the plasma stream, electron temperature, and the formation of the current-sheet-like structure observed in the MPC for the first time.

Gallium Nitride (GaN) High-Electron Mobility Transistors (HEMTs) actually represent one of the best candidates for medium-high power and radio frequency applications. As they operate at large bias and electric fields, a comprehensive analysis of the high-field transport properties is fundamentals, as hot electrons are expected to play a relevant role for the device reliability. In this perspective, Technology Computer-Aided Design (TCAD) simulations can be a very useful tool for the understanding of the phenomena dominating hot-electron degradation mechanisms. The most-accurate modeling approaches are based on the direct solution of the Boltzmann equation, which is not actually available for the GaN material. In this work, the deterministic solution of the Boltzmann transport equation via the spherical-harmonics expansion (SHE-BTE), as incorporated in a commercial TCAD tool, has been extended to the analysis of GaN electrons. To this purpose, the details of the full-band structure has been derived from DFT calculations as in state-of-art literature works, and the electron density of states, $g(E)$ , and group velocity $u_{g}(E)$ , have been calculated for the SHE-BTE for the first time. In addition to this, an accurate calibration of the total scattering rate accounting for nonpolar acoustic and optical carrier-phonon interaction, Coulomb scattering and impact ionization has been carried out against available Monte Carlo data and experiments. The proposed model is also shown to correctly predict the temperature dependence of the electron impact-ionization coefficient and current density up to breakdown.

The major goal of this research is to establish a new theory of generalized thermoelasticity for thermomass gas flow with low velocity and linear resistance based on the general non-Fourier law of heat conduction. The resistance effect has been included in the general heat conduction equation, which is based on the total derivative of the thermomass gas velocity. Using the governing equations of that unique model, two numerical applications of homogeneous, isotropic, and thermoelastic one-dimensional rods have been constructed. The two applications were solved using the Laplace transform and numerical inversion methods. In terms of thermal and mechanical wave distributions, the latest findings illustrate the contrasts between the Lord–Shulman model and the present revolutionary thermoelasticity model. The parameters of the current general non-Fourier equation of heat conduction have a major impact on thermomechanical waves. [ABSTRACT FROM AUTHOR]

Abstract Ionospheric irregularities have been studied since ~ 70 years ago. With the development of Global Navigation Satellite system (GNSS), networks of GNSS receivers have been used to obtain the characteristics of the irregularities, including the drift velocity, the structure, and the evolution. In this paper, keograms based on the Crustal Movement Observation Network of China (CMONOC) were used to characterize the irregularities over the area from longitude 85 to 125 °E and latitude 11 to 35 °N in 2014. Keograms were obtained for the rate of TEC index (ROTI) for every 0.5 degree longitude and 30 min universal time pixel. The results showed that the occurrence rate of irregularities in 2014 was high in the equinox months and December, and lowest in June. In equinox months the irregularities often appeared after sunset. In March the irregularities usually had long lifetime of ~ 5–7 h and ~ 5 degrees apparent longitudinal width. The long lifetime usually was accompanied by obvious eastward drift of ~ 100 m/s and large vertical ROTI (vROTI). In September the irregularities had weaker ROTI and shorter lifetime than those in March. The irregularities in the 2 equinox months should be related to the equatorial plasma bubbles (EPBs). In June, they appeared ~ 2–3 h later than those in equinoxes and drifted westward. The summer irregularities had weakest ROTI and their latitude was ~ 30 °N, much higher than those in equinoxes. In December, the irregularities were discrete patches with a longitudinal width of ~ 2 degrees and short lifetime of ~ 2 h. Unlike the equatorial irregularities in equinox months which are part of equatorial plasma bubbles, the solstice irregularities mainly appear to be a local phenomenon. Graphical Abstract

Equatorial plasma bubbles (EPBs) have long been studied and are becoming increasingly important because they cause severe scintillations in radio waves from Global Navigation Satellite System (GNSS) satellites. In this review paper EPBs and their characteristics like generation mechanism, initial perturbation, occurrence variability, zonal drift velocity, vertical rise velocity, coupling with zonal neutral winds and secondary instabilities are thoroughly reviewed, and future aspects are discussed. [ABSTRACT FROM AUTHOR]

Theoretical research on nonuniform sediment suspension is limited due to difficulties of elucidating nonuniform particle interaction. A new transport equation is generalized for nonuniform suspended sediment based on multi-dispersed two-phase flow theory, to account for nonuniform particle interaction and its effect on sediment suspension. Instead of implementing numerical discretization, constitutive relation of drift velocity is derived by solving the momentum equations with the aid of the Sherman–Morrison–Woodbury formula and the perturbation asymptotic technique. Applied to open channel flows, concentration profiles for each grain size of sediment are derived and a satisfactory consistency is obtained in comparison with both experimental and field data. Nonuniform sediment suspension is attributed to fluid turbulence, gravity, particle inertia and nonuniform particle interaction. The nonuniform effect plays an important role in the vicinity of the riverbed and is positively correlated to sediment concentration and grain size ratios, which helps bring insight into the suspension mechanics. [ABSTRACT FROM AUTHOR]

Adiabatic, boiling, and condensing two-phase flows occur in many heat and mass transfer devices. The drift-flux model is essential for predicting the gas or vapor fraction using one-dimensional codes based on the two-fluid model. The drift-flux model specifies the area-averaged relative velocity between two phases in the one-dimensional momentum equation of the two-fluid model. In this study, the influence of the inlet gas and liquid velocity profiles on the drift-flux model and the void fraction in a vertical large rectangular channel was investigated. The results showed that the extreme case of non-uniform inlet boundary (NUIB) conditions reduced the drift velocity by a maximum of 16.3 %. Both the channel center peak flow of gas (CPG) and single side wall peak flow of gas (SPG) conditions significantly increased the distribution parameter by more than 20 %. In addition, the CPG and SPG conditions significantly reduced the void fraction by more than 20 %. Finally, the void fraction was predicted for the test data with the six NUIB conditions using the extended drift-flux correlation. The correlation was able to predict the void fractions with an error of approximately ±20 % for all NUIB conditions except the CPG condition, which had a maximum error of 54 %. • Inlet boundary condition effect on the drift-flux model was investigated. • Inlet boundary condition effect on void fraction was investigated. • Some non-uniform inlet boundary (NUIB) conditions affected distribution parameter. • Some NUIB conditions affected void fraction development along axial locations. • Predictive capability of the drift-flux model deteriorated for some NUIB conditions. [ABSTRACT FROM AUTHOR]

The drift velocity of a particle under a driving force has its roots in the theory of electrical conduction. Although it has been studied for over 100 years, it still yields surprises. At the heart of a particle’s drift velocity is an interplay of classical, quantum, and statistical mechanics. Irreversibility and energy loss have been assumed as essential features of drift velocities and very little effort has been made to isolate the aspects of particle transport that are due to elastic mechanisms alone. In this paper, we remove energy loss and quantum mechanics to investigate the classical and statistical factors that can produce a drift velocity using only elastic scattering. A Monte Carlo simulation is used to model a particle in a uniform force field, subject to randomly placed scatterers. Time-, space-, and energy-dependent scattering models, with varied ranges of scattering angles, are investigated. A constant drift velocity is achieved with the time scattering model, which has a constant average time between scattering events. A decreasing drift velocity is observed for space and energy-dependent models. The arrival of a constant drift velocity has to do with a balance of momentum gained between collisions and momentum lost after a collision.

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The present work aims to develop an integrated heat transfer and hydrodynamic model for the study of boiler dynamics in fluctuating load conditions. A transient heat transfer model has been developed to estimate water side heat transfer and it is directly integrated with the hydrodynamic model. Two independent natural circulation circuits for furnace water wall and convection tube bank have been considered due to differences in heat transfer, dryness fraction, and void fraction. The transient heat transfer model calculates the heat transfer and water wall temperature of the various sections to calculate total gas side heat transfer, gas temperature profile, and waterside heat transfer in the furnace water wall and convection tube bank. Mass momentum and energy conservation equations are generated for both natural circulation circuits using the estimated value of waterside heat transfer of the transient heat transfer model. These equations are integrated with mass and energy conservation equations for the drum below water level and drum above water level to generate a system of equations to estimate drum pressure and water level fluctuation. This model has been extended for boiler feedback control systems, including the load management and the water level control system. [ABSTRACT FROM AUTHOR]

Ionospheric irregularities have been studied since ~ 70 years ago. With the development of Global Navigation Satellite system (GNSS), networks of GNSS receivers have been used to obtain the characteristics of the irregularities, including the drift velocity, the structure, and the evolution. In this paper, keograms based on the Crustal Movement Observation Network of China (CMONOC) were used to characterize the irregularities over the area from longitude 85 to 125 °E and latitude 11 to 35 °N in 2014. Keograms were obtained for the rate of TEC index (ROTI) for every 0.5 degree longitude and 30 min universal time pixel. The results showed that the occurrence rate of irregularities in 2014 was high in the equinox months and December, and lowest in June. In equinox months the irregularities often appeared after sunset. In March the irregularities usually had long lifetime of ~ 5–7 h and ~ 5 degrees apparent longitudinal width. The long lifetime usually was accompanied by obvious eastward drift of ~ 100 m/s and large vertical ROTI (vROTI). In September the irregularities had weaker ROTI and shorter lifetime than those in March. The irregularities in the 2 equinox months should be related to the equatorial plasma bubbles (EPBs). In June, they appeared ~ 2–3 h later than those in equinoxes and drifted westward. The summer irregularities had weakest ROTI and their latitude was ~ 30 °N, much higher than those in equinoxes. In December, the irregularities were discrete patches with a longitudinal width of ~ 2 degrees and short lifetime of ~ 2 h. Unlike the equatorial irregularities in equinox months which are part of equatorial plasma bubbles, the solstice irregularities mainly appear to be a local phenomenon. [ABSTRACT FROM AUTHOR]

Drift detection is one of the important detection modes in a digital ionosonde system. In this paper, a new data processing method is presented for boosting the automatic and high-quality drift measurement, which is helpful for long-term ionospheric observation, and has been successfully applied to the Chinese Academy of Sciences, Digital Ionosonde (CAS-DIS). Based on Doppler interferometry principle, this method can be successively divided into four constraint steps: extracting the stable echo data; restricting the ionospheric detection region; extracting the reliable reflection cluster, including Doppler filtering and coarse clustering analysis; and calculating the drift velocity. Ordinary wave (O-wave) data extraction, complementary code pulse compression and other data preprocessing techniques are used to improve the signal-to-noise ratio (SNR) of echo data. For the purpose of eliminating multiple echoes, the ionospheric region is determined by combining the optimal height range and detection frequencies obtained from the ionogram. Successively, Doppler filtering and coarse clustering analysis extract reliable reflection clusters. Finally, the weighting factor is brought in, and then weighted least-squares (WLS) is used to fit the drift velocity. The entire data processing process can be implemented automatically without constantly changing parameter settings due to changes in external conditions. This is the first time coarse clustering analysis has been used to extract the paracentral reflection cluster to eliminate scattered reflection points and outer reflection clusters, which further reduces the impacts of external conditions on parameter settings and improves the ability of automatic drift measurement. Compared with the previous method possessed by Digisonde Protable Sounder 4D (DPS4D), the new method can achieve comparable drift detection precision and results even with fewer reflection points. In 2021–2022, several experiments on F region drift detection were carried out in Hainan, China. Results indicate that drift velocities fitted by the new method have diurnal variation and change more gently; the trends of drift velocities fitted by the new method and the previous method are semblable; and this new method can be widely applied to digital ionosondes. [ABSTRACT FROM AUTHOR]

A two-phase thermo-fluid model is required to design safe and efficient thermal-hydraulic systems. The two-fluid model is a mechanistic two-phase flow model in which the interfacial area concentration directly connects the heat and mass transfers between two phases. An approach is classifying various bubbles into two groups based on their drag coefficients. The two-group two-fluid model coupling with the two-group interfacial area transport equation can potentially provide the most accurate analysis of two-phase flows. However, the two-group approach increases the number of transport equations, inducing numerical convergence and instability problems. To mitigate the drawbacks, the two-group drift-flux model needs to be established as a constitutive equation to simplify the two-group two-fluid model by combining two gas momentum conservation equations for respective groups into a total one. The drift-flux model for large square channels has seldom been investigated, even though such channels exist in engineering systems. This study developed the two-group drift-flux model for large square channels based on existing experimental databases in such channels. The distribution parameters and drift velocities for group-one and group-two were modeled from two-group measurement data. The developed group-one and group-two distribution parameter models were consistent with the one-group distribution parameter. The experimental drift-flux plots validated the newly developed two-group drift-flux model for the respective groups, confirming its good prediction performance with -2 % and -4 % errors for group-one and group-two gas velocities, respectively. [ABSTRACT FROM AUTHOR]

The present work develops a model of Thomson scattering (TS) for z-pinch plasmas. Sustained on the phenomenology observed in dynamical-pinch discharges of interest in fusion studies, the plasma dynamics is modeled by axisymmetric bi-Maxwellian velocity distribution with axial and radial drift velocities. Expressions for TS form factor and screening integrals are deduced, and TS spectra are reconstructed. A characteristic temperature of the spectrum is identified, which is determined by a weighted-sum of the axial and radial temperatures, whose coefficients are given by the square of the respective axial and radial components of k→ over the square of the magnitude of k→. It is shown that it is not possible to determine the velocity distribution function of the plasma from just one direction of measurement. Additionally, an experimental setup, which requires two complementary observation directions for a complete determination of the proposed distribution function, is analyzed and its capacity to measure thermal anisotropy and drift velocities is studied for plasma conditions expected in the pinch phase of a plasma focus discharge.

In light of the substantial importance of accurate void fraction predictions for the engineering design and safety evaluation of two-phase systems utilized in space-related applications, this study is dedicated to the investigation of the drift-flux correlation specifically for microgravity conditions. The present study has collected 458 experimental void fraction data taken in microgravity bubbly to annular flows. The analysis of the collected experimental data evident that (1) the distribution parameters vary with the flow conditions, and (2) the drift velocities under microgravity conditions are exceedingly small. However, the distribution parameter models of the reviewed existing drift-flux correlations fail to accurately capture the variation of distribution parameters with flow conditions under microgravity conditions. Moreover, there is a lack of a simple yet effective way to model the drift velocity of microgravity two-phase flow. To overcome the above weaknesses, a new drift-flux correlation has been proposed by (1) taking the flow condition effect on the variation of asymptotic distribution parameters into consideration, and (2) employing the concept of effective body acceleration and considering the decay of drift velocity in annular flow. The newly proposed drift-flux correlation has been evaluated by checking against the collected data and shows good predictive ability. • 458 experimental void fraction data taken in microgravity bubbly to annular flows are collected. • 10 existing drift-flux correlations for microgravity two-phase flow are reviewed and evaluated. • A new drift-flux correlation for microgravity two-phase flow is proposed. • The newly proposed drift-flux correlation shows good predictive ability. [ABSTRACT FROM AUTHOR]

This study has reviewed the past research for adiabatic and boiling GLTP (gas-liquid two-phase) flows in VNR (vertical narrow rectangular) flow channels. 1758 void fraction experimental data have been collected from 13 available databases of various researchers. The underlying distribution parameter and drift velocity features have been obtained by analyzing the experimentally-measured data in the classical Zuber-Findlay plots. Existing seven DF (drift-flux) correlations for the VNR flow channels have been examined with the obtained distribution parameter and drift velocity features from Zuber-Findlay plots and the collected 1758 void fraction data and their predictions are found to be unsatisfactory. So, this study has analyzed the dependencies of the distribution parameter and drift velocity on two-phase density ratio, flow channel separation and width, and local flow conditions, and developed new flow-regime-independent full-flow-range distribution parameter and the drift velocity correlations for the VNR flow channels. These newly-developed correlations have been examined with the obtained distribution parameter and drift velocity features from Zuber-Findlay plots and their agreement has been confirmed. The DF model closed by the newly-developed distribution parameter and the drift velocity correlations has also been verified by the collected 1758 void fraction data, and their relative error is 13.1 %. • Past experimental & theoretical studies on narrow rectangular channels are reviewed. • Existing drift-flux correlations are assessed with the collected experimental data. • Dependencies of drift-flux parameters on local flow conditions, etc. are modelled. • A new full-flow-range drift-flux correlation is developed and benchmarked. [ABSTRACT FROM AUTHOR]

Chorus waves, discovered as a series of repetitive coherent emissions, are well known for producing hazard radiation environments in Earth's magnetosphere. Its repetitive nature directly causes the rapid modulation of pulsating aurora in the upper atmosphere and microburst in the ionosphere, but its origin remains a decades‐old puzzle. Recent simulation suggested the energetic electrons, injected from the magnetotail and drifting eastward around the Earth, are critical to form the repetitive pattern. Based on a survey of 1.5 year data from Van Allen Probes, we provide the first observational evidence for the origin of repetitive chorus emissions. We find there exists universally an inverse correlation between the repetitive period and drift velocity of energetic electrons, uncovering how the drifting energetic electrons tune the repetitive period of chorus emissions, which is also supported by kinetic simulations. Our finding may apply to understand the generation of repetitive emissions in planetary magnetospheres and laboratory plasmas. Plain Language Summary: Whistler‐mode chorus waves pervasively exist in the Earth's and other planetary outer space, which are the major contributor to hazard radiative environment near Earth and specular diffuse aurora in the upper atmosphere. They are characterized by a series of repetitive coherent emissions with the frequency chirping. Scientists have widely believed chorus waves are generated by electron injections during active periods. Although the great progress has been made on the formation of frequency chirping, the origin of its repetitive nature still challenges the community since the early space age. Here, we present a thorough analysis of 1.5 year high‐resolution data from advanced NASA Van Allen Probes, and find there universally exists an inverse correlation between the repetitive period of chorus emissions and drift velocity of electrons. This result firstly uncovers how the rate of energy supplies tunes the repetitive period of chorus waves. This mechanism can also explain the well‐known day‐night asymmetry of the repetitive period of chorus waves. Our finding may help scientists better understand the generation of repetitive waves in an open system, such as other planetary magnetospheres and laboratory plasmas. Key Points: Using Van Allen Probes data, we provide the first observational evidence for the origin of repetitive chorus emissionsThere universally exists an inverse correlation between the repetitive period of chorus emissions and drift velocity of electronsWe propose that the day‐night asymmetry of the repetitive period of chorus emissions is caused by the asymmetry of drift velocity [ABSTRACT FROM AUTHOR]

Gas electron multiplier (GEM) has been installed in the high η region of the Compact Muon Solenoid experiment (CMS) because as example of its high-rate capability. The operational gas of the GEM plays an important role in providing an efficient detection of muon. This work aims to search for a safe and a high-performance gas mixture through a numerical study of the transport properties of ternary gas mixtures. The gas mixtures consists of a noble gas (Ar-Ne-Xe-He) mixed with CO2 and a third gas (N2-C5H12 -CH4 - iC4H10) with different proportions. The gain of single and triple GEM for the mixtures, which show optimal properties, is calculated to estimate their performance in the detector. It is found that the N2 included mixture is giving a high drift velocity while the C5H12 based mixture has the highest Townsend coefficient, which results in higher gain in both single and triple GEM. [ABSTRACT FROM AUTHOR]

Pressure and air to fuel ratio control are extremely difficult in coal-fired grate boilers due to a significant lag in combustion. This leads to suboptimal operation of the boiler and poor efficiency of the plant. This also leads to higher level fluctuation. Fluctuation in pressure, water level and oxygen level are quite evident in the operation of coal-fired grate boilers in fluctuating load conditions. The present work aims to develop a predictive and dynamic simulation model of a coal-fired grate boiler for the prediction of pressure, and water level in fluctuating load conditions and its extension for the prediction of oxygen level. A data-driven approach has been used for the prediction of heat release, distribution of heat transfer, circulation analysis and airflow through the various dampers. This model has been integrated with the boiler dynamics model of a hybrid boiler. Errors in pressure and water level are measured for training data and the multi-objective optimisation method is used for the minimisation of errors. The Batch Gradient Descent method has been used for the minimisation of errors. The proposed integrated model is used for the estimation of heat release and the rate of combustion. Stochiometric combustion calculation is used to predict oxygen level by using the predicted value of airflow and rate of combustion. Root mean squared error is calculated for oxygen level and minimised by the Batch Gradient Descent algorithm. The model has good accuracy in the prediction of boiler pressure and water level and can be extended to improve the boiler controls of a solid fuel fired reciprocating grate boiler in extremely fluctuating load conditions. [ABSTRACT FROM AUTHOR]

Using the state of valley-polarization of electrons in solids is a promising new paradigm for information storage and processing. The central challenge in utilizing valley-polarization for this purpose is to develop methods for manipulating and reading out the final valley state. Here, we demonstrate optical detection of valley-polarized electrons in diamond. It is achieved by capturing images of electroluminescence from nitrogen-vacancy centers at the surface of a diamond sample that are excited by electrons drifting and diffusing through the sample. Monte Carlo simulations are performed to interpret the resulting experimental diffusion patterns. Our results give insight into the drift-diffusion of valley-polarized electrons in diamond and yield a way of analyzing the valley-polarization of ensembles of electrons.

The effect of Bi incorporation into In x Ga 1-x As lattice on the nanosecond pulsed electric field dependence of the drift velocity of electrons in n-type In x Ga 1-x As 1-y Bi y alloys with various doping densities is investigated at room temperature. The electronic band structure of the alloys is calculated by Finite Element Methods (FEM). The electron temperature is determined from analytical modeling of the power dissipation mechanism. The drift velocity of the electrons (v drift) does not saturate up to 5.4 kV/cm electric field for the lowest doping density sample. The sample is burned out at a higher electric field due to the impact ionization mechanism. However, the v drift saturates at a high electric field region in the samples with higher doping densities, and the saturation of electric field values of v drift depends on the doping density for these samples. The highest electron drift mobility (μ drift) is obtained as 6236 cm2/Vs for the sample with the lowest electron density. The heating of the only electrons through the applied electric field is not enough to initiate inter-valley transfer because of scatterings during transport. Hence, the electric field dependence on electron transport occurs only in the central valley. The effect of the scatterings on the electron transport is identified by considering ionized impurity and phonon scatterings. [ABSTRACT FROM AUTHOR]

• Channel aspect ratio affected the distribution parameter in the drift-flux model. • Asymptotic distribution parameter was approximated at 1.2 for square channels. • Hydraulic diameter was used as characteristic length in a drift velocity correlation. • Drift-flux correlation predicted void fractions within ±13.9 % for adiabatic flow data. • Drift-flux correlation predicted void fractions within ±8.72 % for boiling flow data. Numerous industrial components and production processes encounter two-phase flows in rectangular channels. The drift-flux model, mathematically expressed in terms of the drift-flux parameters, such as the drift velocity and distribution parameter, is often utilized to solve two-phase flow problems. The constitutive equations of the drift-flux parameters have been limitedly developed and assessed for dispersed two-phase flows in rectangular channels. This study discusses the effects of geometrical parameters, such as the characteristic length and aspect ratio of a rectangular channel, on dispersed two-phase flow parameters. For the flow conditions of collected data in rectangular channels, it was observed that the hydraulic diameter was appropriate as the characteristic length scale for the drift velocity calculation since the drift flux correlation using the hydraulic diameter correlated better with experimental data. The asymptotic distribution parameters in the constitutive equation of the distribution parameter were approximated to be 1.35 and 1.20 for rectangular channel aspect ratios less than 0.25 and greater than 0.33, respectively. Due to the lack of data, the asymptotic distribution parameters were tentatively determined based on a linear interpolation scheme between 1.35 and 1.20 for the aspect ratios between 0.25 and 0.33. The constitutive equations of the drift-flux model were assessed using the collected data with various fluids, pressures, and flow conditions. The constitutive equations of the drift-flux model could predict the void fractions with negligible bias and random uncertainty of ±0.0358 and ±0.0434 (absolute value measure) and ±13.9 % and ±8.72 % (relative value measure) for adiabatic and boiling two-phase flows in rectangular channels, respectively. [ABSTRACT FROM AUTHOR]

Drift detection is one of the important detection modes in a digital ionosonde system. In this paper, a new data processing method is presented for boosting the automatic and high-quality drift measurement, which is helpful for long-term ionospheric observation, and has been successfully applied to the Chinese Academy of Sciences, Digital Ionosonde (CAS-DIS). Based on Doppler interferometry principle, this method can be successively divided into four constraint steps: extracting the stable echo data; restricting the ionospheric detection region; extracting the reliable reflection cluster, including Doppler filtering and coarse clustering analysis; and calculating the drift velocity. Ordinary wave (O-wave) data extraction, complementary code pulse compression and other data preprocessing techniques are used to improve the signal-to-noise ratio (SNR) of echo data. For the purpose of eliminating multiple echoes, the ionospheric region is determined by combining the optimal height range and detection frequencies obtained from the ionogram. Successively, Doppler filtering and coarse clustering analysis extract reliable reflection clusters. Finally, the weighting factor is brought in, and then weighted least-squares (WLS) is used to fit the drift velocity. The entire data processing process can be implemented automatically without constantly changing parameter settings due to changes in external conditions. This is the first time coarse clustering analysis has been used to extract the paracentral reflection cluster to eliminate scattered reflection points and outer reflection clusters, which further reduces the impacts of external conditions on parameter settings and improves the ability of automatic drift measurement. Compared with the previous method possessed by Digisonde Protable Sounder 4D (DPS4D), the new method can achieve comparable drift detection precision and results even with fewer reflection points. In 2021–2022, several experiments on F region drift detection were carried out in Hainan, China. Results indicate that drift velocities fitted by the new method have diurnal variation and change more gently; the trends of drift velocities fitted by the new method and the previous method are semblable; and this new method can be widely applied to digital ionosondes.