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Computational fluid dynamics (CFD) modeling has emerged as a valuable tool for investigating complex processes like microencapsulation. This paper aims to validate the ability of CFD simulations to predict particle size distribution in a polymer microencapsulation process. The CFD modeling approach employed a Eulerian multiphase framework, incorporating a discrete population balance model to track the evolution of the droplet population. A realizable k-ε turbulence model and a multiple reference frame strategy were utilized to capture the system's flow dynamics. The results reveal that while the CFD simulations align well with experimental data at higher agitation speeds (>10,000 rpm), discrepancies arise at lower speeds (<7500 rpm), indicating a challenge in accurately capturing turbulent viscous regimes. Despite these challenges, the CFD model demonstrates robust predictive capabilities for droplet formation and distribution in microencapsulation processes, validated by error margins within the acceptable limits. The validated model can be used as a reliable tool to guide experimental efforts and optimize process parameters, contributing to an enhanced understanding and control of microencapsulation processes. [ABSTRACT FROM AUTHOR]

Exploiting the van der Waals model of liquids, it is possible to derive analytical formulas for the thermodynamic functions governing solvation, the transfer of a solute molecule from a fixed position in the ideal gas phase to a fixed position in the liquid phase. The solvation Gibbs free energy change consists of two contributions: (a) the high number density of all liquids and the repulsive interactions due to the basic fact that each molecule has its own body leading to the need to spend free energy to produce an appropriate cavity to contain the solute molecule; (b) the ubiquitous intermolecular attractive interactions lead to a gain in free energy for switching-on attractions between the solute molecule and neighboring liquid molecules. Also the solvation entropy change consists of two contributions: (a) there is an entropy loss in all liquids because the cavity presence limits the space accessible to liquid molecules during their continuous translations; (b) there is an entropy gain in all liquids, at room temperature, due to the liquid structural reorganization as a response to the perturbation represented by solute addition. The latter entropy contribution is balanced by a corresponding enthalpy term. The scenario that emerged from the van der Waals model is in qualitative agreement with experimental results. [ABSTRACT FROM AUTHOR]

This paper explores the fundamental cosmological principle, with a specific focus on the homogeneity and isotropy assumptions inherent in the Friedmann model that underpins the standard model. We propose a modified redshift model that is based on the spatial distribution of luminous matter, examining three key astronomical quantities: light intensity, number density, and the redshift of galaxies. Our analysis suggests that the model can account for cosmic accelerated expansion without the need for dark energy in the equations. Both simulations and analytical solutions reveal a unique pattern in the formation and evolution of cosmic structures, particularly in galaxy formation. This pattern shows a significant burst of activity between redshifts 0 < z < 0.4, which then progresses rapidly until approximately z ≈ 0.9, indicating that the majority of cosmic structures were formed during this period. Subsequently, the process slows down considerably, reaching a nearly constant rate until around z ≈ 1.6, after which a gradual decline begins. We also observe a distinctive redshift transition around z ≈ 0.9 before the onset of dark-matter-induced accelerated expansion. This transition is directly related to the matter density and is dependent on the geometry of the universe. The model’s ability to explain cosmic acceleration without requiring fine tuning of the cosmological constant highlights its novelty, providing a fresh perspective on the dynamic evolution of the universe.

This paper explores the fundamental cosmological principle, with a specific focus on the homogeneity and isotropy assumptions inherent in the Friedmann model that underpins the standard model. We propose a modified redshift model that is based on the spatial distribution of luminous matter, examining three key astronomical quantities: light intensity, number density, and the redshift of galaxies. Our analysis suggests that the model can account for cosmic accelerated expansion without the need for dark energy in the equations. Both simulations and analytical solutions reveal a unique pattern in the formation and evolution of cosmic structures, particularly in galaxy formation. This pattern shows a significant burst of activity between redshifts 0 < z < 0.4, which then progresses rapidly until approximately z ≈ 0.9, indicating that the majority of cosmic structures were formed during this period. Subsequently, the process slows down considerably, reaching a nearly constant rate until around z ≈ 1.6, after which a gradual decline begins. We also observe a distinctive redshift transition around z ≈ 0.9 before the onset of dark-matter-induced accelerated expansion. This transition is directly related to the matter density and is dependent on the geometry of the universe. The model's ability to explain cosmic acceleration without requiring fine tuning of the cosmological constant highlights its novelty, providing a fresh perspective on the dynamic evolution of the universe. [ABSTRACT FROM AUTHOR]

The study of solid/liquid interface is of great significance for understanding various phenomena such as the nanostructure of the interface, liquid wetting, crystal growth and nucleation. In this work, the nanostructure of the pyridinium ionic liquid [BPy]BF4 on different gold surfaces was studied by molecular dynamics simulation. The results indicate that the density of the ionic liquids near the gold surface is significantly higher than that in the bulk phase. Cation's tail (the alkyl chain) orients parallel to the surface under all studied conditions. Cation's head (the pyridine ring) orientation varies from parallel to perpendicular, which depends on the temperature and corrugation of the Au(hkl) surface. Interestingly, analysis of simulated mass and number densities revealed that surface corrugation randomizes the cations packing. On smooth Au(111) and Au(100) surfaces, parallel and perpendicular orientations are well distinguished for densely packed cations. While on corrugated Au(110), cations' packing density and order are decreased. Overall, this study explores the adsorption effect of the gold surface on ionic liquids, providing some valuable insights into their behavior on the solid/liquid interface.

Computational fluid dynamics (CFD) modeling has emerged as a valuable tool for investigating complex processes like microencapsulation. This paper aims to validate the ability of CFD simulations to predict particle size distribution in a polymer microencapsulation process. The CFD modeling approach employed a Eulerian multiphase framework, incorporating a discrete population balance model to track the evolution of the droplet population. A realizable k-ε turbulence model and a multiple reference frame strategy were utilized to capture the system’s flow dynamics. The results reveal that while the CFD simulations align well with experimental data at higher agitation speeds (>10,000 rpm), discrepancies arise at lower speeds (

Exploiting the van der Waals model of liquids, it is possible to derive analytical formulas for the thermodynamic functions governing solvation, the transfer of a solute molecule from a fixed position in the ideal gas phase to a fixed position in the liquid phase. The solvation Gibbs free energy change consists of two contributions: (a) the high number density of all liquids and the repulsive interactions due to the basic fact that each molecule has its own body leading to the need to spend free energy to produce an appropriate cavity to contain the solute molecule; (b) the ubiquitous intermolecular attractive interactions lead to a gain in free energy for switching-on attractions between the solute molecule and neighboring liquid molecules. Also the solvation entropy change consists of two contributions: (a) there is an entropy loss in all liquids because the cavity presence limits the space accessible to liquid molecules during their continuous translations; (b) there is an entropy gain in all liquids, at room temperature, due to the liquid structural reorganization as a response to the perturbation represented by solute addition. The latter entropy contribution is balanced by a corresponding enthalpy term. The scenario that emerged from the van der Waals model is in qualitative agreement with experimental results.

Recent eruptions of the Shinmoedake volcano, Japan, have provided a valuable opportunity to investigate the transition between explosive and effusive eruptions. In October 2017, phreatic/phreatomagmatic explosions occurred. They were followed in March 2018 by a phase of hybrid activity with simultaneous explosions and lava flows and then a transition to intermittent, Vulcanian-style explosions. Evolution of surface phenomena, temporal variations of whole-rock chemical compositions from representative eruptive material samples, and rock microtextural properties, such as the crystallinity and crystal size distribution of juvenile products, are analyzed to characterize the eruption style transition, the conduit location, and the shallow magma conditions of the volcanic edifice. The 2017–2018 eruptive event is also compared with the preceding 2011 explosive–effusive eruption. The chemical and textural properties of the 2018 products (two types of pumice, ballistically ejected lava blocks, and massive lava) are representative of distinct cooling and magma ascent processes. The initial pumice, erupted during lava dome formation, has a groundmass crystallinity of up to 45% and the highest plagioclase number density of all products (1.9 × 106/mm3). Conversely, pumice that erupted later has the lowest plagioclase number density (1.2 × 105/mm3) and the highest nucleation density (23/mm4 in natural logarithm). This 2018 pumice is similar to the 2011 subplinian pumice. Therefore, it was likely produced by undegassed magma with a high discharge rate. Ballistics and massive lava in 2018 are comparable to the 2011 Vulcanian ballistics. Conversely, the high plagioclase number density pumice that occurred in 2018 was not observed during the 2011 eruption. Thus, such pumice might be specific to hybrid eruptions defined by small-scale explosions and lava dome formation with low magma discharge. The observed transitions and temporal variations of the activities and eruption style during the 2017–2018 Shinmoedake eruptions were primarily influenced by the ascent rate of andesitic magma and the geological structure beneath the summit crater. [ABSTRACT FROM AUTHOR]

In sonochemistry, acoustic bubbles are a population of microreactors where hydrogen and oxidants are produced. Optimizing the effectiveness of sonochemical processes and, as a result, designing ultrasonic reactors for diverse uses, including hydrogen generation, requires determining the number density of acoustic microreactors. The number density of micro-bubbles during water sonolysis was determined in this study using a novel semi-empirical method developed (for the first time) using hydrogen sono-production. The technique is based on relying on the overall molar production rate of hydrogen (i.e. resulted from the sonicated solution) to the amount of hydrogen produced per a single collapsing bubble, either from its internal gas phase reaction (pyrolysis) or from both the bubble inside and its liquid shell (via H•+H•→H 2). The retrieved number density of bubbles varied between ∼108 to ∼1013 L−1 s−1 (depending on empirical conditions), showing an excellent order with that reported in the literature. As the frequency increased, the number of active bubbles increased, regardless of whether the number density is calculated through the amount of hydrogen formed inside the bubble or the total single-bubble yield (gas phase + liquid shell). However, a reduced number density was obtained as it was calculated via the total single-bubble yield, where this decrease goes up with the rise of ultrasound frequency (from 210 to 724 kHz) and the decrease of the liquid temperature. It has been deduced that hydrogen is mainly formed at the bubble's liquid shell (via H•+H•→H 2), particularly at higher frequency and cold liquid. [Display omitted] • Hydrogen sonoproduction was quantified and used for determining the bubbles number. • A full cavitation-based model was applied for predicting the H 2 's single bubble yield. • The H 2 -based technique relies the overall and the single bubble yield during sonication. • The bubbles' number density was ∼108 to ∼1013 L−1 s−1, depending on circumstances. • The number density increased with frequency increase and liquid temperature decrease. [ABSTRACT FROM AUTHOR]

Foam, as a group of disconnected gas bubbles wrapped with liquid film, also exists in municipal solid waste (MSW) landfills. In this study, a foam flow model in MSW is established, in which the population balance equation is adopted to calculate the dynamic process of foam generation, bursting, and transport. The status of foam is characterized using the number density, which is defined as the number of bubbles per unit volume of pore. The relative permeability and viscosity of foam are corrected according to its number density. Then, the proposed model is verified through the foam displacement experiment conducted in an MSW column. The foam flow model can accurately simulate the transient change of pressure drop and liquid saturation during foam displacement. The values of coefficients of foam generation and bursting rates are fitted to be suitable for MSW. Finally, the foam flow model is applied to predict the gas pressure development in an MSW landfill. Foam is able to maintain the landfill gas pressure at a high value even for aged MSW with low gas generation rate. The S-shaped curve of gas pressure versus depth suggests that the foam flow model is capable of simulating the phenomenon of high gas pressure accumulated in the deep layer of landfills because it takes into account the nonuniform distribution of foam number density. The advantage of the foam flow model over the gas flow model is discussed with respect to landfill gas pressure prediction. [ABSTRACT FROM AUTHOR]

A computational tool for simulating the temporal evolution of the soot-particle size distribution function (SDF) in the internal combustion engine (ICE) and in the attached exhaust pipe is developed and tested against available experimental data on the soot-particle SDF at the outlet of the exhaust system. Firstly, a database of soot particle properties (particle mean diameter, dispersion, total particle number density vs. time for different fuels, fuel-to-air equivalence ratios, temperatures, pressures, and exhaust gas recirculation) is developed based on the thoroughly validated detailed model of soot formation under ICE conditions. The database is organized in the form of look-up tables. Secondly, the soot-particle SDF in the database is approximated using the log-normal SDF, which is directly used in the multidimensional calculations of the ICE operation process. Thirdly, the coagulation model of soot particles is developed, which includes three coagulation mechanisms: Brownian, turbulent–kinetic, and turbulent–diffusion. This model is applied for simulating the evolution of the soot-particle SDF in the exhaust pipe after opening the exhaust valve. Calculations show that the coagulation process of soot particles in the exhaust pipe has a significant effect on the mean size of particles at the outlet of the exhaust system (the mean particle diameter can increase by almost an order of magnitude), and the dominant mechanism of particle coagulation in the exhaust system of a diesel engine is the Brownian mechanism. The objective, approach, and obtained results are the novel features of the study. [ABSTRACT FROM AUTHOR]

In the present study, the influence of a 1.1 tesla Transverse Magnetic Field (TMF) on Laser-Induced Breakdown Spectroscopy (LIBS) of Mg-alloy plasma has been explored. The Mg plasma was produced using an Nd: YAG laser (1064 nm, 10 ns) at an intensity of 2 GW/cm2. Inert gases of Ar, Ne, and He were filled as environmental gases at pressures ranging from 1 to 100 Torr. Optical emission spectra from laser-produced plasma were detected with the help of a spectrometer, and plasma parameters such as excitation temperature (Texc) and electron number density (ne) were evaluated. Enhancement in the Mg plasma's Texc and ne in the presence of TMF was noticed under all experimental conditions, including different ambient gases with varying pressures and time delays (0.42 µs–9.58 µs). Plasma confinement by applied TMF was analytically evaluated through thermal beta (βt) values, which were <1 under all circumstances. The highest Texc and ne values (17,259 K and 11.5 × 1017 cm−3) for Mg-alloy plasma were obtained with ambient Ar in TMF, while the lowest values (8793 K and 1.0 × 1017 cm−3) were obtained in presence of He gas in the absence of TMF. SEM analysis was used to determine the surface structure of laser-ablated Mg alloy in the presence and absence of TMF. It revealed that the formation of cones, cavities, and non-uniform melting are characteristic features of ambient Ar, while spikes and cavities are prominent features in Ne gas environments. Conical spikes and dendrites are distinct features when ambient He is present. In comparison with the field-free condition, distinct and well-defined structures were observed in the presence of TMF. By controlling LPP parameters, the surface structuring of Mg alloy can be controlled. The optimization and enhancement of LPP parameters make it a highly useful tool for thin film deposition, coatings of multilayers, and ion implantation/doping. [ABSTRACT FROM AUTHOR]

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The number density of alkali atoms in vaper cell is an important parameter for atomic magnetometer. The vapor cell is usually heated to a high temperature for the number density exceed to 1018 m−3 to achieve the spin-exchange-relaxation-free (SERF) process. The optical rotation of multichannel atomic magnetometers is affected by the number density distribution. We present an effective method for monitoring and analyzing the spatial distribution homogeneity of the atomic number density in the alkali metal cell within the SERF magnetometer. The numerical results from researching the model of electric heating films and ovens show that the temperature gradient increases with an increase in the cell temperature. This causes an nonuniform number density distribution based on the saturated vapor pressure curve. We present a laser absorption spectroscopy method by using the high-resolution beam profiling camera to record the power of the beam before and after the cell. An optimized optical system of the atomic magnetometer has been established by measuring the the number density variation in the spatial distribution in mm scale. The number density variation coefficient, which is introduced to evaluate the distribution homogeneity, increases from 0.0257 to 0.0333 when the temperature of the oven wall rises from 140°C to 190 °C, showing the same trend as the simulation results. The optical rotation distribution is calculated according to the magnetometer output signal formula. This study is of great interest for optimizing the oven structure and improving the stability of atomic spin polarization and sensitivity of the multichannel magnetometer. [ABSTRACT FROM AUTHOR]

The present paper introduces a novel semi-empirical technique for the determination of active bubbles’ number in sonicated solutions. This method links the chemistry of a single bubble to that taking place over the whole sonochemical reactor (solution). The probe compound is CCl4, where its eliminated amount within a single bubble (though pyrolysis) is determined via a cavitation model which takes into account the non-equilibrium condensation/evaporation of water vapor and heat exchange across the bubble wall, reactions heats and liquid compressibility and viscosity, all along the bubble oscillation under the temporal perturbation of the ultrasonic wave. The CCl4 degradation data in aqueous solution (available in literature) are used to determine the number density through dividing the degradation yield of CCl4 to that predicted by a single bubble model (at the same experimental condition of the aqueous data). The impact of ultrasonic frequency on the number density of bubbles is shown and compared with data from the literature, where a high level of consistency is found.

A computational tool for simulating the temporal evolution of the soot-particle size distribution function (SDF) in the internal combustion engine (ICE) and in the attached exhaust pipe is developed and tested against available experimental data on the soot-particle SDF at the outlet of the exhaust system. Firstly, a database of soot particle properties (particle mean diameter, dispersion, total particle number density vs. time for different fuels, fuel-to-air equivalence ratios, temperatures, pressures, and exhaust gas recirculation) is developed based on the thoroughly validated detailed model of soot formation under ICE conditions. The database is organized in the form of look-up tables. Secondly, the soot-particle SDF in the database is approximated using the log-normal SDF, which is directly used in the multidimensional calculations of the ICE operation process. Thirdly, the coagulation model of soot particles is developed, which includes three coagulation mechanisms: Brownian, turbulent–kinetic, and turbulent–diffusion. This model is applied for simulating the evolution of the soot-particle SDF in the exhaust pipe after opening the exhaust valve. Calculations show that the coagulation process of soot particles in the exhaust pipe has a significant effect on the mean size of particles at the outlet of the exhaust system (the mean particle diameter can increase by almost an order of magnitude), and the dominant mechanism of particle coagulation in the exhaust system of a diesel engine is the Brownian mechanism. The objective, approach, and obtained results are the novel features of the study.

Stirring based liquid metal processing is the widely explored process by researchers for the production of metal matrix composites (MMCs). The dispersion of reinforcement particles is the major challenge in the process. The stirring process parameters govern the dispersion of reinforcement particles in MMCs. The important stirring process parameters are stirring speed, stirrer geometry, stirrer position, and stirring time. In the literature, research works are reported, where the effect of such parameters on the dispersion of particles was investigated either by analyzing flow field using computational methods (assuming constant fluid properties) or by sectioning the casted samples. In cast condition, the dispersion of particles is also influenced by the solidification phenomena. The aim of the present work is to investigate the significance and the effect of stirrer geometry, stirrer position and stirring speed on the dispersion of reinforcement particles inside melting crucible, during the stirring. Aluminium alloy LM25 was used as the matrix material and silicon carbide (SiC) particles having mean size 37.58 microns (d50 value) were used as the reinforcement phases. Samples of the composite slurry during the stirring process were dragged using a quartz tube at three levels inside crucible and microstructure analysis was carried out. Number density (ND) and inter particle distance were evaluated for parameter combinations. The uniform dispersion of SiC particles was observed at 45° stirrer blade angle, 400 rpm stirring speed and 40 mm stirrer position. And, significance order of individual parameter was observed as stirring speed < stirrer position < stirrer blade angle. [ABSTRACT FROM AUTHOR]

Starting from a d − dimensional black hole (BH) in f (R) gravity, we analyzed the effect of modified gravity on critical point parameters, the difference in number densities, and configuration entropy during the BH phase transition phenomenon. From our investigations, consistent results with charged AdS BH are obtained that is holographic dual of van der Waal's fluid and hence the BH in modified gravity. The thermodynamic pressure, temperature, and free energy are affected by f (R) gravity. The difference in the number densities of molecules (small and large BHs) and configuration entropy are investigated as a function of reduced temperature (τ ̃). The difference in the number densities of BH molecules in f (R) gravity decreases with the increase in τ ̃ , whereas, S c o n increases monotonically and becomes a concave function with the increase in space–time dimensions. The relation between the difference in the number density of BH molecules and space–time dimensions (d) decreases with the increase in dimension d. Finally, using our results, the laws of BH Physics are also discussed. [ABSTRACT FROM AUTHOR]

The effect of the increase in the alkyl chain length of cation on the properties of deep eutectic solvents based on ethylene glycol has been investigated employing classical molecular dynamics simulations. The change in the structural and dynamic properties in both the bulk and liquid–vapor interface is explored through various analyses. The interaction between the anion and the ethylene glycol increases with an increase in the alkyl chain length of the cation, as observed in the increase of the lifetime of the hydrogen bond formed between the two. The terminal carbon atoms are found to be closer to each other when the cation changes from tetraethylammonium to tetrabutylammonium. The cations are located closer to the interface, and the association of the alkyl chains becomes more significant with increased alkyl chain length, decreasing the surface tension values. [Display omitted] • Molecular dynamic studies of DESs with cations of different alkyl chain length. • The surface tension of DESs decreases with an increase in cation alkyl chain length. • Cation chain length influences the interactions between anions and hydrogen bond donors. • Long-range ordering is more significant in case of cations with longer alkyl chain. [ABSTRACT FROM AUTHOR]

Based on the formalism of the Bethe-Salpeter equation, we present here a new approach to deal with the temperature (T)- and the applied magnetic field (H)-dependent critical current densities (jcs) of superconductors (SCs). Saliently, it employs (i) the premise that the chemical potential μ (T, H) subsumes most of the factors to which the widely varying empirical values of jc (T, H) of an SC are conventionally attributed, (ii) the basic equation that defines jc as a product of the electronic charge, the number density of superconducting electrons (ns) and their critical velocity (vc), (iii) a recently derived equation for ns (T, H), and (iv) the empirical values of jc (T, H)—which it is meant to explain—as inputs into one of its equations which, paradoxical though it may seem, is shown to have the virtue of shedding light on several parameters related to jc (T, H), such as μ, ns, vc, m*, nL, and λm, where m* is the effective mass of an electron, nL the number of occupied Landau levels, and λm the magnetic interaction parameter. Remarkably, the approach is found to lead to two branches of μ-dependent solutions with distinctly different values of the parameters corresponding to the same value of jc (T, H). This is reminiscent of the behavior of the chemical potential in SCs with a low density of charge carriers that was reported by Marel [Physica C 165, 35 (1990)] and described as anomalous. Finally, we show that our approach suggests the exciting possibility of fabricating an SC that has a bespoke value of jc at suitably chosen values of T and H. For the sake of concreteness, we employ here some of the available empirical data on the jc (T, H) values of Bi-2212. [ABSTRACT FROM AUTHOR]

The study of solid/liquid interface is of great significance for understanding various phenomena such as the nanostructure of the interface, liquid wetting, crystal growth and nucleation. In this work, the nanostructure of the pyridinium ionic liquid [BPy]BF 4 on different gold surfaces was studied by molecular dynamics simulation. The results indicate that the density of the ionic liquids near the gold surface is significantly higher than that in the bulk phase. Cation's tail (the alkyl chain) orients parallel to the surface under all studied conditions. Cation's head (the pyridine ring) orientation varies from parallel to perpendicular, which depends on the temperature and corrugation of the Au(hkl) surface. Interestingly, analysis of simulated mass and number densities revealed that surface corrugation randomizes the cations packing. On smooth Au(111) and Au(100) surfaces, parallel and perpendicular orientations are well distinguished for densely packed cations. While on corrugated Au(110), cations' packing density and order are decreased. Overall, this study explores the adsorption effect of the gold surface on ionic liquids, providing some valuable insights into their behavior on the solid/liquid interface., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

To investigate experimentally how ultra-fine bubbles (UFBs) may promote hydrate formation, we examined the formation of propane (C3H8) hydrate from UFB-infused water solution using two preparation methods. In one method, we used C3H8-hydrate dissociated water, and in the other, C3H8-UFB-included water prepared with a generator. In both solutions, the initial conditions had a UFB number density of up to 109 mL−1. This number density decreased by only about a half when stored at room temperature for 2 days, indicating that enough amount of UFBs were stably present at least during the formation experiments. Compared to the case without UFBs, the nucleation probabilities within 50 h were ~1.3 times higher with the UFBs, and the induction times, the time period required for the bulk hydrate formation, were significantly shortened. These results confirmed that UFB-containing water promotes C3H8-hydrate formation. Combined with the UFB-stability experiments, we conclude that a high number density of UFBs in water contributes to the hydrate promoting effect. Also, consistent with previous research, the present study on C3H8 hydrates showed that the promoting effect would occur even in water that had not experienced any hydrate structures. Applying these findings to the debate over the promoting (or “memory”) effect of gas hydrates, we argue that the gas dissolution hypothesis is the more likely explanation for the effect.

Guided by recent studies that point to the pivotal role played by the Fermi energy (EF) in determining the properties of high-temperature superconductors, we have been following a course where the critical temperature, gap(s), and the temperature T- and the applied magnetic field H-dependent critical current density jc (T, H) are addressed in a unified, EF-incorporated framework. Needed in such an approach is an equation for the number density ns (T, H) which is a constituent of jc (T, H). This equation is derived here by applying the field-theoretic Landau quantization prescription to ns (T, H = 0). As an application of the new equation, we also deal herein with a few empirical values of jc (T, H) of MgB2 and show that the corresponding ns (T, H) values lead to bounds on the effective mass of the charge carriers, the Fermi velocity, and the critical velocity. [ABSTRACT FROM AUTHOR]

Guided by recent studies that point to the pivotal role played by the Fermi energy (EF) in determining the properties of high-temperature superconductors, we have been following a course where the critical temperature, gap(s), and the temperature T- and the applied magnetic field H-dependent critical current density jc (T, H) are addressed in a unified, EF-incorporated framework. Needed in such an approach is an equation for the number density ns (T, H) which is a constituent of jc (T, H). This equation is derived here by applying the field-theoretic Landau quantization prescription to ns (T, H = 0). As an application of the new equation, we also deal herein with a few empirical values of jc (T, H) of MgB2 and show that the corresponding ns (T, H) values lead to bounds on the effective mass of the charge carriers, the Fermi velocity, and the critical velocity. [ABSTRACT FROM AUTHOR]

To investigate the ablation process of a carbon steel model, emission spectroscopy was applied in a 20 MW arc-heater. 21 frames of spectral data were captured in the 4-seconds test, which consists of the radiation from Oxygen, Nitrogen, Copper, Iron, Potassium, Sodium, Chromium, and Calcium. Atom species, gas temperature and number density at 2.7 s after ignition (start power supply) were determined, the gas temperature is finally determined as 6700 ± 400 Kelvin. The temperature and number density evolution during the test was given based on the time series spectral data, which show us that the temperature results calculated by atom spectral lines of Copper (510.5/515.3), Iron (527.3/537.3) and Nitrogen (862.9/871.1) were reliable, the constant value of temperature and number density also confirm the stability of the test condition. [ABSTRACT FROM AUTHOR]

This study is an attempt to estimate the radiative characteristics of aerosols, namely, the scattering coefficient (βsc), absorption coefficient (βab), extinction coefficient (βex), single scattering albedo (ω) and the phase function P(θ), on a seasonal basis, incorporating the concurrent measurements of aerosol mass loading, size distribution and chemical composition at the tropical coastal site, Thiruvananthapuram. The software package Optical Properties of Aerosols and Clouds (OPAC) has been made use for the estimation of the radiative parameters. This paper presents the seasonal features of aerosol chemical composition and their source characteristics also. Along with this, the association between size-resolved number density of aerosols and their chemical characteristics were also investigated through correlation analysis. The location is significantly influenced by human activities as seen from the dominance of the anthropogenic component which is highest in winter (22%) with comparable values in pre-monsoon and post-monsoon and minimum in monsoon (13%). The sea-salt contribution is found to peak in monsoon (~40%) and attain a minimum in winter. The source characterization using principal component analysis along with back-trajectory analysis showed the seasonally changing mixed aerosol sources over the region. Accordingly, the radiative properties of aerosols also exhibit significant seasonal variations. βsc varied from 0.04 to 0.14 km−1 and βab between 0.01 and 0.05 km−1 over a year. The single-scattering albedo exhibited significant seasonal differences being ~0.71 for winter and ~0.89 (0.55 μm) for monsoon season, indicating the presence of more absorbing aerosols in winter. [ABSTRACT FROM AUTHOR]

To investigate the impact of interfacial layer effects on the thermal conductivity of nanofluids and the microscopic mechanisms of enhanced thermal conductivity, this study employed non-equilibrium molecular dynamics to compute the thermal conductivity, number density, radial distribution function, and mean square displacement distribution of SiC nanofluids. The impact of nanoparticle volume fraction and particle size parameters on the thermal conductivity of nanofluids and the structure of interfacial adsorption layers was discussed. The simulation calculation results show that the coefficient of thermal conductivity of nanofluid is positively related to the volume fraction of nanoparticles, increasing from 0.6529 W/(m·K) to 0.8159 W/(m·K), and the enhancement of thermal conductivity by the volume fraction can be up to 33.97 %. The thermal conductivity is inversely correlated with the change in particle size, and the maximum improvement in thermal conductivity by particle size can reach up to 12.05 %. The simulated results of the thermal conductivity of nanofluid are almost consistent with the predicted results of the Yu&Choi model, and the error is controlled within 5 %. Simultaneously, the thickness of the interfacial adsorption layer decreases with an increase in particle size. This reduction arises due to larger particles having a smaller specific surface area, resulting in fewer particle surfaces covered by the interface layer. Moreover, the impact of particle size on the arrangement and affinity of molecules within the interface layer contributes to this decrease. Overall, interface layer effects exhibit a dual impact on the thermal conduction of nanofluids. The structured formation and high-density distribution of the adsorption layer contribute to enhanced heat transfer, while thermal resistance between nanoparticle surfaces and the fluid restricts heat transmission. [Display omitted] • The variation of thermal conductivity of SiC water-based nanofluids under different factors is studied. • The microscopic mechanism of the interfacial layer effect enhancing the thermal conductivity of nanofluids is revealed. • The quantitative conclusion of the adsorption layer thickness of SiC water-based nanofluid system is obtained. • The theoretical verification results are in good agreement with the simulation data, and error is controlled within 5 %. [ABSTRACT FROM AUTHOR]

Highlights • Droplet clusters in air-assisted sprays are experimentally characterized. • Size of the largest clusters scales with large eddies of the turbulent air flow around droplets. • Degree of clustering is higher towards the spray edge and for higher local liquid mass fraction. • Droplet clustering contributes to local fluctuations of liquid mass flux in sprays. • The turbulent number flux is always negative and higher towards the spray edge. Abstract The clustering of droplets in air-assisted water sprays operating under ambient atmospheric conditions is experimentally studied with the aim to characterize the droplet clusters and study the consequence of clustering on local turbulent mass flux of droplets. Planar measurements of droplet number density and velocity were achieved by application of the PIV technique, while the ILIDS technique was used for sizing individual droplets. Experiments were performed for four different injector operating conditions corresponding to different liquid mass fractions at the radial measurement stations far downstream of the injector exit. The droplet clusters were statistically characterized by the measurement of the D parameter. The clustering of droplets occurs over a range of length scales, however, the largest length scale of droplet clusters ( L c ) was found to scale with large eddies of the turbulent air flow around droplets. For higher local liquid mass fraction, the D parameter was also higher, while L c was smaller, indicating intense clustering. The local turbulent number flux of droplets, which is essentially the correlation between fluctuations of the droplet number density and the droplet velocity ( nu ‾ ), was found to be non-negligible relative to the steady flux especially towards the edge of the spray, where the tendency of the droplets for clustering was found to be higher. Also, the correlation nu ‾ was always negative suggesting that locally higher droplet number density due to passage of the clusters of droplets leads to smaller droplet velocity fluctuations. [ABSTRACT FROM AUTHOR]

A method is proposed for measuring the size of particles in a dynamic light scattering analyzer along with a determination of their number density in suspension. It is shown that this method can be used to measure the parameters of various nanoparticles, including nonspherical ones. An experimental prototype of a dynamic light scattering analyzer for measuring the number density of nanoparticles along with their sizes is described. [ABSTRACT FROM AUTHOR]

In the current work, the N-phase compressible algebraic slip model (ASM) framework is presented. The framework is implemented in TransAT© which is a commercial finite-volume CFD solver specialized in the modeling of multiphase flows. It is applied to bubbly flows in vertical pipes where compressibility of the gas phase is important. Effects of compressibility of the gas phase namely, the change in volume of the individual bubbles, the reduction in the liquid volume fraction, and the change in bubble size due to almost constant number density are identified and illustrated with the help of an analytical one-dimensional model. It was shown that the volume effect was the strongest, although the effect of the change in the bubble radius is also important though to a lesser extent. The framework implemented in TransAT© does not solve for the gas number density and assumes a fixed radius for the bubbles. In the first step the implementation is verified with the help of the one-dimensional model. In the next step, the implementation is tested against the selected test cases from the TOPFLOW database for different types of bubbly flow namely the wall-peaked, the transition and the central-peaked. The simulation results are able to predict the overall behavior of the different types of bubbly flow. The radial gas velocity profiles for all the test cases showed a good match with the experimental data. Unrealistic accumulation of small bubbles close to the walls is observed for the wall-peaked test cases. The results showed that the unrealistic behaviour could be removed tuning the wall lubrication force model. The results highlight the inadequacy of the current wall lubrication force models and show that the wall lubrication force should depend on the velocity of the continuous phase probably in an analogous way to the lift force. [ABSTRACT FROM AUTHOR]