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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]

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]

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]

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]

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]

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. [ABSTRACT FROM AUTHOR]

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 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]

A quasi in-situ investigation of the cell to dendrite transition (CDT) was carried out by preparing Ni-W single crystal alloy with an increasing withdrawal rate. It was shown that the solidification process occurred under the convex growth interface, which produced a gradient of the drift velocity along the interface and led to a coarsening effect on the microstructures. This coarsening effect, combined with the refining effect induced by the increasing withdrawal rate, resulted in the CDT and an inconstant primary spacing. The results showed that the cell to dendrite transition for hexagonal cell was nonuniformed, and the tip splitting and lateral branching for cellular and dendritic structures were controlled by the ratio of the neighbor spacing to the average primary spacing. Two models and a rule, which separately revealed the influence factor of the drift velocity, the transition process from cell to dendrite, and the law of tip splitting and lateral branching for cellular and dendritic structures, were proposed. It was hoped that the present work could provide ideas for in-situ studies of microstructural evolution. [Display omitted] • A quasi in-situ observation of cell to dendrite transition (CDT) was carried out. • A model revealing the influence factor of the drift velocity was proposed. • A nonuniformed CDT transition process for hexagonal cells was found. • A law guiding the adjustment of the primary spacing was proposed. [ABSTRACT FROM AUTHOR]

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]

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]

We investigate the axisymmetric slow viscous liquid flow around a spherical bubble located on the axis of a long circular tube analytically based on the Stokes approximation. The bubble translates along the axis of the tube with a constant velocity within Hagen–Poiseuille flow flowing far from the bubble. The translating velocity of the bubble and mean velocity of the Hagen–Poiseuille flow are given arbitrarily. To analyze Stokes equation, we use the method of complex eigenfunction expansions and the method of least squared error. As results, the streamline patterns and the pressure contour lines in the flow field are drawn for some radii of the bubble. The drag exerted on the bubble and the pressure change induced by the bubble are determined according to the radius of the bubble. For a small bubble radius in the tube, we compared results with previous asymptotic results. The drift velocity of the bubble due to the Hagen–Poiseuille flow in the circular tube is calculated according to the bubble radius. We show that extra pressure drop due to the drift bubble in the Hagen–Poiseuille flow becomes positive or negative depending on the radius of the bubble. When the bubble moves along a circular tube in the absence of the Hagen–Poiseuille flow, a series of viscous toroidal eddies appears in the anterior and posterior directions of the bubble. Moreover, we discuss the pressure and normal stress distributions on the bubble surface, which depend on the radius of the bubble. [ABSTRACT FROM AUTHOR]

In this paper, we present a collection of results focussing on the transport properties of doped direct-gap inverted-band highly polar III-nitride semiconductors (GaN, AlN, InN) and GaAs in the transient and steady state, calculated by using nonlinear quantum kinetic theory based on a non-equilibrium statistical ensemble formalism (NESEF). In the present paper, these results are compared with calculations using Monte Carlo modelling simulations and experimental measurements. Both n-type and p-type materials, in the presence of intermediate to high electric fields, are considered for several temperatures and carrier concentrations. The agreement between the results obtained using nonlinear quantum kinetic theory, with those of Monte Carlo calculations and experimental data is remarkably good, thus satisfactorily validating the NESEF. [ABSTRACT FROM AUTHOR]

Monte Carlo simulations (MCSs) of electron swarms in F2, Ar, and CF4 under ac (radio frequency) electric and dc magnetic fields ($\mathbf {E}(t)$ and $\mathbf {B}$ fields) crossed at a right angle are performed, and the periodic response of the electron drift velocity vector $\mathbf {W}(t)$ is depicted as an elliptic vector locus (EVL). The vector head of $\mathbf {W}(t)$ draws an ellipse synchronously to the alternation of the ac $\mathbf {E}(t)$ field. The tilt of the major axis of the EVL, which represents the Hall deflection, increases with $|\mathbf {B}|$ , and the ellipse drawn by $\mathbf {W}(t)$ takes its maximum around the $|\mathbf {B}|$ value resonant to the ac $\mathbf {E}(t)$ field. It is demonstrated that a theoretical approximation derived from a constant-collision-frequency (CCF) model predicts well the fundamental tendency of the $|\mathbf {B}|$ -dependent variation of the EVL of $\mathbf {W}(t)$ in the three real gases. The $\mathbf {W}(t)$ in F2 agrees well with the CCF model at low electric fields for its nature that the total collision frequency does not change significantly. On the other hand, those in Ar and CF4 deviate from the CCF model. This visual depiction using the EVL of $\mathbf {W}(t)$ is expected to be applicable to the estimation of the directional electron drift in inductively coupled magnetized plasmas and to the characterization of the $\mathbf {W}(t)$ response in real gases. [ABSTRACT FROM AUTHOR]

Monte Carlo algorithms are developed to simulate the electron transport in semiconductors. In particular, the drift velocity in GaN semiconductors is calculated, and a comparison with experimental measurements is discussed. Explicit expressions for the scattering probabilities and distributions of the scattering angle of electrons on polar optical and intervalley phonons, and acoustic deformation potential as well are given. A good agreement of the simulation results and the experimental measurements reveals that the M-L valley is located at 0.7 eV higher than the Γ-valley. This value agrees with other experimental studies, while it is lower compared to ab initio calculations. [ABSTRACT FROM AUTHOR]

The possibility of intensifying the processes in gas-dispersed systems with coagulated particles of different dimensions and the efficiency of air purification depend on the characteristics of the field created by electrodepositing plants. This work was carried out with a view of optimizing the parameters of electrodepositing systems to increase the rate of aerosol cloud deposition in an air medium. The theoretical and experimental studies are oriented to improving the methods of removing harmful aerosol formations in the air space by exposure to external electrostatic fields. This paper describes experimental investigation of coagulation and deposition of aerosol particles by inducing external fields in a closed volume with account for different technical parameters of devices for trapping different kinds of finely divided particles. To obtain the dispersed and concentration characteristics of aerosol, use is made of the method of searching for the solution in the form of a multiparameter function of the size distribution of particles realized as part of a laser measuring complex. [ABSTRACT FROM AUTHOR]

• The all-sky airglow imager and Digisonde data were used to investigate plasma bubbles. • Optical image processing was performed to obtain image products with high resolution. • Plasma bubbles appeared like long stripe and bifurcated vertically. • The distance between adjacent plasma bubbles was in the range of 100–400 km. • Plasma bubbles generally drifted eastward and the average drift velocity was 90 m/s. Ionospheric plasma bubbles and scintillation phenomena often occur at low latitudes in China. The all-sky airglow imager located at Fuke station in Hainan (19.5°N, 109.2°E) is part of the Meridian project in China. In this work, we used mainly the observation data obtained by the imager and a digisonde to study plasma bubbles. Optical image processing—including image enhancement, azimuth correction and image projection—was performed on the original airglow observation images, and clear high-resolution images of the bubbles were obtained. Based on these, the morphological features, spatial and temporal variations, spatial scale, drift velocity of the plasma bubbles in the F region of the ionosphere were investigated and analyzed. The plasma bubbles appeared as long, dark stripes on the bright airglow emission background. Their large-scale structures often bifurcated vertically, and were usually tilted westward with north-south extension along the magnetic field lines. The east-west scale of the plasma bubbles was usually greater than 200 km and these increased gradually with time. Moreover, the distance between the adjacent plasma bubbles also increased over time, and was in the 100–400 km range. Plasma bubbles generally drifted eastward with an average drift velocity of approximately 90 m/s. The occurrence and duration of the plasma bubbles were compared with digisonde observations, and it was shown that plasma bubbles lasted for nearly four hours. Additionally, the main characteristics of the plasma bubbles were obtained using both optical and radio observations and the study of which can be beneficial for monitoring and predicting ionospheric scintillations. [ABSTRACT FROM AUTHOR]

The high-field carrier transport properties of 4H-SiC including the impact ionization coefficients are theoretically analyzed based on a full-band Monte Carlo simulation. The simulation reasonably reproduces the behaviors of the impact ionization coefficients experimentally reported, such as temperature dependence, anisotropy, and the difference between electrons and holes. The mechanisms behind these behaviors are then discussed based on the band structure of 4H-SiC. [ABSTRACT FROM AUTHOR]

Graphene nanoscroll introduced recently is another form of a graphene-based two-dimensional material, which is especially attractive in nanoelectronic applications. As carriers can travel ballistically or semi-ballistically, they can reach high-speed and energy if the channel length is enough. Therefore, they can collide and result in an excessive current called ionisation current. As a result, it is important to study this mechanism carefully. In this paper, we propose an analytical approach to calculate an ionisation coefficient. [ABSTRACT FROM AUTHOR]

This paper presents a computational comparison of the penetration capability of two shaped charges—with conical and hemispherical (degressive thickness) liners. It is shown that close values of the penetration capability of the charges are provided only in the ideal case of strictly axisymmetric motion of shaped-charge jets. [ABSTRACT FROM AUTHOR]

We investigate the axisymmetric slow viscous flow around a sphere located on the axis of a long circular cylinder analytically based on the Stokes approximation. The sphere translates along the centerline of the cylinder with a constant velocity within Hagen–Poiseuille flow flowing far from the sphere. The translating velocity of the sphere and mean velocity of the Hagen–Poiseuille flow are arbitrary constant. To analyze Stokes equation, we use the method of complex eigenfunction expansions and the method of least squared error. As results, the streamline patterns and the pressure contour lines in the flow field are drawn for some radii of the sphere. The drag exerted on the sphere and the pressure change by the sphere are determined as the radius of the sphere. For a small sphere radius and for a sphere fitted closely in the cylinder, we compared results with previous asymptotic results and lubrication theory results, respectively. The velocity of the drifting sphere by the Hagen–Poiseuille flow in the circular cylinder is determined as the sphere radius. The pressure change induced by the drifting sphere in the Hagen–Poiseuille flow is also obtained. When the sphere translates along the plugged circular cylinder, a series of viscous toroidal eddies appears each side of the cylinder expectably. Moreover, we discussed the pressure and shear stress on the sphere surface and showed some critical range of these stresses. [ABSTRACT FROM AUTHOR]

We consider the problem of a hopping ball excited by a travelling harmonic wave on an elastic surface. The ball, considered as a particle, is assumed to interact with the surface through inelastic collisions. The surface motion due to the wave induces a horizontal drift in the ball. The problem is treated analytically under certain approximations. The phase space of the hopping motion is captured by constructing a phasevelocity return map. The fixed points of the return map and its compositions represent periodic hopping solutions. The linear stability of the obtained periodic solution is studied in detail. The minimum frequency for the onset of periodic hops, and the subsequent loss of stability at the bifurcation frequency, have been determined analytically. Interestingly, for small values of wave amplitude, the analytical solutions reveal striking similarities with the results of the classical bouncing ball problem. [ABSTRACT FROM AUTHOR]

Abstract Filtered two-fluid model (fTFM) for gas-particle flows require closures for the sub-filter scale corrections to interphase drag force and stresses, the former being more significant. In this study, we have formulated a neural-network-based model to predict the sub-grid drift velocity, which is then used to estimate the drag correction. As a part of the neural network model development effort, we derived a transport equation for drift velocity and then performed a budget analysis to conclude that an algebraic model for drift velocity in terms of the filtered variables that are resolved in a fTFM simulation is adequate, and the model should include the filtered gas-phase pressure gradient as a marker in addition to the filtered particle volume fraction and the filtered gas-solid slip velocity. Both a priori and a posteriori analyses reveal that the present model for drift velocity when used in a fTFM simulation is able to capture the fine-grid simulation results quite well. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

A numerical technique to calculate real-space electron transport coefficients in gas under crossed electric and magnetic fields ($E \times B$ fields) by the propagator method (PM) was newly developed. Components of a centroid drift velocity vector of an electron swarm and its diffusion coefficients defined in the $E$ , $B$ , and $E \times B$ directions were calculated by applying the PM stepwise to the zeroth-, first-, and second-order $x$ , $y$ , and $z$ spatial moment equations derived from the Boltzmann equation. The results calculated for SF6 at $N = 10^{22}\,\,\text{m}^{-3}$ in $E/N$ and $B/N$ ranges of 100–1000 Td and 100–1000 Hx, respectively, agreed with those obtained by Monte Carlo simulations with discrepancies of a few percent. The Hall deflection of the drift velocity vector and the direction dependence of the diffusion coefficients were appropriately reproduced. A relaxation scheme developed for quick convergence of the electron velocity distribution function was effective also in the relaxations of the first- and second-order spatial moment distribution functions. A prototype of the PM as a calculation scheme to derive a set of electron transport coefficients necessary for fluid model simulations of magnetized plasmas was established. [ABSTRACT FROM AUTHOR]

The dispersal of drifting objects like plant propagule under wave action can provide important information for the restoration of the plant community in coastal areas. An improved motion equation of the drift under wave action is established by coordinate transformation under the premise that the buoyancy is always perpendicular to the free surface, considering the variation of submerged height and the pressure gradient. Its numerical solution obtained by the fourth order Runge-Kutta method was compared with the experimental results in the literature, and the rationality of the improved motion equation is then verified. Then the perturbation method and Lagrange tracking principle were used to obtain the average longitudinal drift velocity expressed by Stokes drift velocity. The effect of different forces in the motion equations to the longitudinal diffusive motion was analyzed. Finally, the hydrodynamic coefficients affecting the prediction were analyzed, and the results show that the effects of the added mass coefficient and the drag coefficient are mainly reflected in the region with higher wave heights. The findings may provide certain scientific guidance for the restoration of coastal vegetation ecology through natural colonization. • An improved motion equation of the drifting objects under wave-induced flow is established by considering the change of the submerged height. • The motion equation was numerally and analytically solved. • The effects of added mass coefficient and drag coefficient on drift velocity are analyzed based on the numerical solution. • The average longitudinal drift velocity was analytically obtained and the effect of different forces to motions was analyzed. [ABSTRACT FROM AUTHOR]

• Air-water bubble release experiments in upward inclinations from 3° to 89°. • Developed a new non-invasive method using computer vision to characterize Taylor bubbles. • Front velocity increases in pipe-to-annulus transition and tail velocity exhibits a transition behavior. • The Froude number characteristic dimension is better represented by the external ID for low inclinations and by the equi-periphery diameter for high inclinations. • Using the hydraulic diameter resulted in a 50% – 62% drift velocity underestimation in comparison with the experiments. The present study focuses on characterizing and modeling the Taylor bubble front and tail velocities in a pipe-to-annulus transition geometry. Air-water bubble release experiments in upward inclinations from 3° to 89° were performed in a 4-in (102-mm) ID pipe with a capped 3-in (76-mm) OD pipe inserted from downstream, forming a pipe-to-annulus transition. A new non-invasive method to measure liquid distribution using computer vision was developed. This method enables visualization of the liquid distribution and local measurements of Taylor bubble front and tail velocities. The Taylor bubble front velocity is dictated by drift, while the tail velocity is related to the liquid fallback rate and bubble coalescence. The drift velocity increased in the pipe-to-annulus transition, while the tail velocity exhibited a transition behavior. The Froude number characteristic dimension is better represented by the external ID for low inclinations and by the equi-periphery diameter for high inclinations. The typically reasonable approach of using the hydraulic diameter as the characteristic dimension resulted in a significant underestimation (50% – 62%) of drift velocity in the annulus for the experiments performed. The proposed model for drift velocity uses appropriate scales for the characteristic length and presented a mean average percentage error of 7.5%. [Display omitted] [ABSTRACT FROM AUTHOR]

An experimental study has been carried out for the velocity field characteristics of AlGaN on AlN/sapphire templates. A pulsed voltage input combination with a four-point measurement technique has been used to determine the drift velocity of electrons as a function of the applied field. Comparative data with earlier templates shows that a device performance depends on low-field mobility and saturated drift velocity. [ABSTRACT FROM AUTHOR]

Highlights • Pipe orientation effect on average void fraction is investigated. • The distribution parameter and drift velocity in an inclined pipe are studied. • A new void fraction correlation including the effect of pipe orientation is developed based on drift flux model. Abstract Experimental study on steam-water two phase vertical and inclined upward flow (15–90°) was performed in a rectangular channel with cross section of 17 mm × 10 mm under atmospheric pressure to investigate the phase distribution and the average void fraction in the cross section which were obtained from the local void fraction measurement by a conductivity probe. The inlet superficial velocities of the steam and water varied from 0.72 to 3.85 m/s and from 0.11 to 0.3 m/s respectively. A high speed camera was used to identify the flow patterns. Experimental results show that the phase distribution curves are significantly affected by channel orientation and the average void fraction first decreases and then increases with the increase of orientation. Based on the drift-flux model, two parameters, namely, the distribution parameter (C 0) and the drift velocity (U gm ) have been studied in detail. Both the distribution parameter and the drift velocity are found to be functions of orientation. The distribution parameter decreases with the increase of orientation while the drift velocity first increases and then decreases with the increase of orientation., Based on the experimental data, an improved drift-flux model is proposed especially for the slug and churn flow, which predicts the void fraction in an inclined channel with good accuracy. [ABSTRACT FROM AUTHOR]

Highlights • The sub-channel void fraction has been measured for all flow regimes. • 20 drift-flux models for rod bundles have been summarized, reviewed and evaluated. • The new distribution parameter correlation is proposed for sub-channel. • The L / D effect on distribution parameter has been analyzed. • The effect of different spacer grids on distribution parameter has been discussed. Abstract Drift-flux model has been one of the most popular models predicting two phase flow parameters in nuclear reactor and other industrial equipment since proposed. Most of researches are based on the void fraction measurement on the whole cross-section of the void fraction, which is under the influence of casing tube and might be unfit for sub-channel. Therefore, experiments have been performed to measure the void fraction in sub-channels with the newly designed impedance void meter, based on which the existing drift-flux correlations have been evaluated. However, few correlations have good performance in bubbly and cap bubbly flow. In order to improve the accuracy and consider the physical significance, the new correlation of distribution parameter is proposed by adopting Julia’s drift velocity correlation. The proposed correlation could predict the present data, Yang’s data and Clark’s data with the mean relative error of 13.96%, 16.23% and 24.9% respectively. Furthermore, the L / D effect on distribution parameter has been analyzed with different spacer grids. The mixing vane spacer grid (MVSG) results in a larger value of distribution parameter than simplified spacer grid in low void fraction region for the stronger recirculating flow. [ABSTRACT FROM AUTHOR]

Drift-flux model is a simple and reliable tool for void fraction prediction in two-phase flows. This work examines its performance in gas-liquid flow of small bubbles (<1 mm) at low void fractions (<10  −1 ) that resembles bubbly flow in human bloodstream during Decompression Sickness and can be also found in other two-phase applications such as flow boiling in macro-channels. Drift-flux model predictions are compared with experimental data measured in co-current upward bubbly flow for varying gas/liquid flow properties. Water and blood simulant are used as test liquids, while bubble size is controlled using prescribed surfactant (SDS) concentrations. Homogeneous flow model, which is a sub-case of drift-flux model, predicts adequately void fraction in water and blood simulant when the mean bubble size is lower than 200 μm. For larger bubbles in water (mean size up to 800 μm) and in blood simulant (mean size up to 350 μm), the performance of thirteen drift-flux models from literature is examined. Ten of them concern specifically bubbly flow, whereas three models are applicable to a wide range of flow conditions. To our knowledge, this is the first time that drift-flux models are tested at combined low void fractions (between ∼10 −3 and ∼10 −1 ) and sub-millimeter bubble sizes, so the determination of drift-flux parameters (distribution parameter, C 0 and drift velocity, U gm ) is elaborated. On this account, a bubble size dependent correlation is proposed for U gm determination. [ABSTRACT FROM AUTHOR]

We observe that carriers in graphene can be accelerated to the Fermi velocity without heating the lattice. At large Fermi energy |EF| > 110 meV, electrons excited by a high-power terahertz pulse ETHz relax by emitting optical phonons, resulting in heating of the graphene lattice and optical-phonon generation. This is owing to enhanced electron–phonon scattering at large Fermi energy, at which the large phase space is available for hot electrons. The emitted optical phonons cause carrier scattering, reducing the drift velocity or carrier mobility. However, for |EF| ≤ 110 meV, electron–phonon scattering rate is suppressed owing to the diminishing density of states near the Dirac point. Therefore, ETHz continues to accelerate carriers without them losing energy to optical phonons, allowing the carriers to travel at the Fermi velocity. The exotic carrier dynamics does not result from the massless nature, but the electron–optical-phonon scattering rate depends on Fermi level in the graphene. Our observations provide insight into the application of graphene for high-speed electronics without degrading carrier mobility. [ABSTRACT FROM AUTHOR]

The aim of this paper is an investigation of electric field-dependent drift velocity characteristics for Al0.3Ga0.7N/AlN/GaN heterostructures without and with in situ Si3N4 passivation. The nanosecond-pulsed current- voltage (I-V) measurements were performed using a 20-ns applied pulse. Electron drift velocity depending on the electric field was obtained from the I-V measurements. These measurements show that a reduction in peak electron velocity from 2.01 x 107 to 1.39 x 107 cm/s after in situ Si3N4 passivation. Also, negative differential resistance regime was observed which begins at lower fields with the implementation of in situ Si3N4 passivation. In our samples, the electric field dependence of drift velocity was measured over 400 kV/cm due to smaller sample lengths. Then, a well-known fitting model was fitted to our experimental results. This fitting model was improved in order to provide an adequate description of the field dependence of drift velocity. It gives reasonable agreement with the experimental drift velocity data up to 475 kV/cm of the electric field and could be used in the device simulators. [ABSTRACT FROM AUTHOR]

• Upward bubbly flow characteristics through flow development are experimentally studied in a large-size square channel. • Local void fraction, axial gas and liquid velocities, interfacial area concentration, and bubble diameter are measured. • Drift-flux parameters are determined directly by local measurement data and compared with existing correlations. • Interfacial area concentration correlations are compared with measurement data. Gas-liquid two-phase flows frequently occur in various flow channels in engineering systems with heat and mass transport processes. The channel geometry affects thermo-fluid behavior generally. Extensive research is done on gas-liquid two-phase flows in circular and annular channels with a wealth of local two-phase flow measurement data. Square channels are used in various engineering disciplines, but there has only been limited experimental research on two-phase flows in square channels with local flow parameter measurements. For two-phase flow analyses in square channels, knowledge of the flow characteristics and model validation against some key parameters, such as the drift-flux parameters and the interfacial area concentration, is crucial. An experiment for upward bubbly flows was conducted in a large square channel with an inside cross-section of 0.136 × 0.136 m. A four-sensor optical probe and a hot-film anemometer were used to measure local two-phase flow parameters at 66 points in an octant symmetric triangular cross-section at three axial locations. The measured two-phase flow parameters were the void fraction, axial gas velocity, axial liquid velocity, interfacial area concentration, and bubble Sauter mean diameter. The flow characteristics through flow development were investigated based on the local measurement data. The local measurement data directly determined the drift-flux parameters through their definitions. The distribution parameters determined through experimentation could be reproduced by the existing correlation for large circular pipes indicating that the flow characteristics in large square channels may be similar to those in large circular pipes. Based on existing drift-flux correlations for large circular pipes, the void fractions in the current experiment could be fairly predicted. Furthermore, the interfacial area concentrations could be predicted by existing correlations with reasonable accuracy. [ABSTRACT FROM AUTHOR]

The axisymmetric Stokes flow around a disk in a circular tube is investigated based on a Stokes approximation, where the radius of the disk, located coaxially with the circular tube, is arbitrary. The disk translates perpendicularly to its own plane along the centerline of the tube, and a Hagen–Poiseuille flow exists far upstream and downstream from the disk. The velocities of the translating disk and the Hagen–Poiseuille flow are given arbitrarily. The problem is investigated through an analysis of the Stokes equation using a complex eigenfunction expansion and the least squares method. The streamline patterns from the stream function, and the pressure distributions of the flow fields, are shown for some typical radii of the disk. The force exerted on the disk, and the pressure drop created by the disk itself, are both calculated as functions of the disk radius. For a small disk radius, the results of the force are coincident with previous asymptotic expressions. For a given velocity of the Hagen–Poiseuille flow in the tube, the translational drift velocity of the disk is determined as a function of the disk radius. The results show that this drift velocity is slightly lower than the mean velocity of the Hagen–Poiseuille flow component projected by the disk. The induced pressure drop from the disk drifting in the Hagen–Poiseuille flow is quite small. When the disk translates in a stagnant circular tube, a series of viscous toroidal eddies appears in the tube apart from the disk, as expected. [ABSTRACT FROM AUTHOR]

The phenomenon of drift motion of single-domain ferromagnetic particles induced by the Magnus force in a viscous fluid is studied analytically. We use a minimal set of equations to describe the translational and rotational motions of these particles subjected to a harmonic force and a non-uniformly rotating magnetic field. Assuming that the azimuthal angle of the magnetic field is a periodic triangular function, we analytically solve the rotational equation of motion in the steady state and calculate the drift velocity of particles. We study in detail the dependence of this velocity on the model parameters, discuss the applicability of the drift phenomenon for separation of particles in suspensions, and verify numerically the analytical predictions. [ABSTRACT FROM AUTHOR]

Based on the phenomenological consideration of the drift and carrier heating processes in the bulk of the А B type semiconductors in strong crossed electric and magnetic fields, a quasi-three-dimensional model describing main kinetic components of the current parameters is constructed. The behavior of the diffusion coefficient under these conditions is analyzed. It is found that the inequality of the longitudinal and transverse components of the effective mass and kinetic energy leads to strong differences in the components of the diffusion coefficient and drift velocity. The behavior of the drift and diffusion characteristics in magnetic fields with various induction intensities is analyzed. It is revealed that when the magnetic induction increases, the value of the longitudinal component of the velocity increases, and subsequently, falling sections appear on the drift transverse induction characteristic, which indicates the possibility of using this effect to create nonlinear inductive active elements. Anisotropy is observed on the transverse diffusion induction characteristic, which is manifested in the fact that for large values of B > 2 T, splitting of the maximum in two components occurs, which is also promising from the point of view of creating a new class of converter devices. [ABSTRACT FROM AUTHOR]

Wind causes migration and eventual removal (dispersal or beaching) of evaporation-suppressing monolayer on open-water storages. Hence, an autonomous system capable of adaptive re-application of monolayer according to the prevailing wind conditions is highly desirable. Key to the design and functioning of such a system is a fundamental understanding of the spatial movement/distribution characteristics of the monolayer material. To ‘bridge’ between centimeter-scale, clean room laboratory experimentation (e.g. Petri dish–scale in a wind tunnel) and field conditions (i.e. hectare-scale open-water storages), the drift velocity and spreading behavior of C18OH monolayer (in water-emulsion), applied continuously during constant wind stress, were investigated on a 6 m-diameter indoor water tank for wind speeds in the range 4–8 m/s. Monolayer was found to spread in a teardrop shape initially, which evolved into a wedge shape whose close-to-straight edges were detectable visually due to the wave-damping effect of the monolayer. The internal angle of the wedge decreased with increasing wind speed, consistent with the force equilibrium between the lateral force of the monolayer spreading outwards and the increasing shear imposed with increasing wind speed. The relationship between internal angle of the wedge and wind velocity was a power law. The widely-accepted spreading kinetics formula was used to derive an empirical relationship for the drift velocity that is a power law with respect to the wind speed. This model was compared with the experimental data, with a modest degree of agreement. [ABSTRACT FROM AUTHOR]

We have theoretically studied the generation rate of longitudinal optical (LO) phonons in mid-infrared quantum cascade laser so as to learn the effect of phonons on electron transmission characteristics. The LO phonon performance was analyzed by combining the Monte-Carlo simulation with kinetic equations. We have obtained the LO phonon number under different applied field to show that the generating rate and the saturating number of optical phonon increases with applied field. At last we propose the pulsed pumping to point out the importance of LO phonon decaying into two acoustic phonons in electron transmission. [ABSTRACT FROM AUTHOR]