This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signa...This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signals and degrade positioning accuracy.Managed by the Indonesian Geospatial Information Agency(BIG),the Indonesia Continuously Operating Reference Station(Ina-CORS)network comprises over 300 GNSS receivers spanning equatorial to southern low-latitude regions.Ina-CORS is uniquely situated to monitor EPB generation,zonal drift,and dissipation across Southeast Asia.We provide a practical tool for EPB research,by sharing two-dimensional rate of Total Electron Content(TEC)change index(ROTI)derived from this network.We generate ROTI maps with a 10-minute resolution,and samples from May 2024 are publicly available for further scientific research.Two preliminary findings from the ROTI maps of Ina-CORS are noteworthy.First,the Ina-CORS ROTI maps reveal that the irregularities within a broader EPB structure persist longer,increasing the potential for these irregularities to migrate farther eastward.Second,we demonstrate that combined ROTI maps from Ina-CORS and GNSS receivers in East Asia and Australia can be used to monitor the development of ionospheric irregularities in Southeast and East Asia.We have demonstrated the combined ROTI maps to capture the development of ionospheric irregularities in the Southeast/East Asian sector during the G5 Geomagnetic Storm on May 11,2024.We observed simultaneous ionospheric irregularities in Japan and Australia,respectively propagating northwestward and southwestward,before midnight,whereas Southeast Asia’s equatorial and low-latitude regions exhibited irregularities post-midnight.By sharing ROTI maps from Indonesia and integrating them with regional GNSS networks,researchers can conduct comprehensive EPB studies,enhancing the understanding of EPB behavior across Southeast and East Asia and contributing significantly to ionospheric research.展开更多
To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software ...To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software integrated within the optical microscope,the diameter and number of the bubbles on the surface of three borosilicate glasses were quantified.From the hardness and crack initiation resistance(CR),we built the relationship between the porosity and the mechanical performance of these borosilicate glasses.展开更多
During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a rest...During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid slag.In contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive information.Therefore,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding times.The results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles increases.In addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually decreases.In one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the large.These findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.展开更多
In this paper,the failure caused by HRAM loads which were generated by high-speed projectile penetration,and protection technology of the fluid-filled structure were explored.A bubble was preset on the projectile traj...In this paper,the failure caused by HRAM loads which were generated by high-speed projectile penetration,and protection technology of the fluid-filled structure were explored.A bubble was preset on the projectile trajectory in a fluid-filled structure.Based on the reflection and transmission phenomena of pressure waves at the gas-liquid interface and the compressibility characteristics of gases,a numerical analysis was conducted on the influence of preset bubble on projectile penetration and structural failure characteristics.The results indicate that the secondary water-entry impact phenomenon occurs when a preset bubble exists on the projectile trajectory,leading to the secondary water entry impact loads.The rarefaction waves reflected on the surface of the preset bubble cause the attenuation ratio of the initial impact pressure peak to reach 68.8%and the total specific impulse attenuation ratio to reach 48.6%.Furthermore,the larger the bubble,the faster the projectile,and the more obvious the attenuation effect.Moreover,due to the compressibility of the bubble,the global deformation attenuation ratio of the front and rear walls can reach over 80%.However,the larger the bubble size,the faster the projectile velocity,the smaller the local deformation attenuation effect of the rear wall,and the more severe the failure at the perforation of the rear wall.展开更多
In nature,cavitation bubbles typically appear in clusters,engaging in interactions that create a variety of dynamicmotion patterns.To better understand the behavior ofmultiple bubble collapses and the mechanisms of in...In nature,cavitation bubbles typically appear in clusters,engaging in interactions that create a variety of dynamicmotion patterns.To better understand the behavior ofmultiple bubble collapses and the mechanisms of interbubble interaction,this study employs molecular dynamics simulation combined with a coarse-grained force field.By focusing on collapsemorphology,local density,and pressure,it elucidates how the number and arrangement of bubbles influence the collapse process.The mechanisms behind inter-bubble interactions are also considered.The findings indicate that the collapse speed of unbounded bubbles located in lateral regions is greater than that of the bubbles in the center.Moreover,it is shown that asymmetrical bubble distributions lead to a shorter collapse time overall.展开更多
The gas-liquid countercurrent flow pattern is complex and the bubble migration velocity is difficult to predict in the process of bullheading well killing.The experiment on bubble migration in gas-liquid countercurren...The gas-liquid countercurrent flow pattern is complex and the bubble migration velocity is difficult to predict in the process of bullheading well killing.The experiment on bubble migration in gas-liquid countercurrent flow in annulus is carried out under different working conditions to reveal how the wellbore inclination angle,liquid phase property and countercurrent liquid velocity affect the bubble deformation and bubble migration trajectory/velocity,and to establish a bubble migration velocity prediction model.The bubbles in the countercurrent flow mainly migrate in two modes:free rising of isolated bubbles,and interactive rising of multiple bubbles.The bubbles migrate by an S-shaped trajectory in the countercurrent flow.With the increase of countercurrent liquid velocity,the lateral oscillation of bubbles is intensified.The increases of wellbore inclination angle,liquid density and liquid viscosity make the bubble migration trajectory gradually to be linear.The bubble is generally ellipsoidal during its rising.The wellbore inclination angle has little effect on the degree of bubble deformation.The bubbles are ellipsoidal during rising,with little influence of wellbore inclination angle on bubble deformation.With the increase of liquid viscosity and density,the aspect ratio of the bubble decreases.As the wellbore inclination angle increases,the bubble migration velocity gradually decreases.As the liquid viscosity increases,the bubble migration velocity decreases.As the liquid density increases,the bubble migration velocity increases slightly.The established bubble migration velocity prediction model yields errors within±15%,and demonstrates broad applicability across a wide range of operating conditions.展开更多
Bubbles within an elastic shell,which undergo ultrasound-driven oscillation to treat tumors and soft tissues,are frequently treated as viscoelastic media.Therefore,studying the dynamic behavior of bubbles wrapped in a...Bubbles within an elastic shell,which undergo ultrasound-driven oscillation to treat tumors and soft tissues,are frequently treated as viscoelastic media.Therefore,studying the dynamic behavior of bubbles wrapped in a viscoelastic medium while considering an elastic shell can provide theoretical support for ultrasound biotherapy.Bubbles are always in the form of clusters.Therefore,a model of spherical bubble clusters in a liquid cavity wrapped by an elastic shell was constructed,the coupled oscillation equations of bubbles were obtained by taking into account the dynamic effects of the elastic shell and the viscoelastic media outside the cavity,and the oscillation behaviors of the bubbles were analyzed.Acoustic waves at 1.5 MHz could cause bubbles with a radius of 1μm to resonate.Increasing the number of bubbles increased the suppressing effect of bubble oscillation caused by bubble interaction.The bubble cluster oscillation caused the elastic shell to oscillate and be stressed,and the stress trend was the inverse of the bubble oscillation trend with maximal tensile and compressive stresses.Bubbles with an equilibrium radius of 2μm exhibited the lowest inertial cavitation threshold,making inertial cavitation more likely under high-frequency acoustic excitation.The inertial cavitation threshold of bubbles was heavily influenced by the acoustic wave frequency,bubble number density,and bubble cluster radius.The nonspherical oscillation stability of bubbles was primarily affected by the driving acoustic pressure amplitude and frequency,bubble initial radius,bubble number density,and bubble cluster radius.The acoustic frequency and amplitude exhibited a synergistic effect,with a minimum unstable driving acoustic pressure threshold of approximately 0.13 MPa.The initial radius within the elastic shell affected the minimum unstable driving acoustic pressure threshold.展开更多
Bubble column reactors fitted with tube bundles(BCR TB)belong to common heat transfer equipment in the field of chemical engineering,yet the complicated thermal-hydraulics performance of BCR TB has not been deeply rev...Bubble column reactors fitted with tube bundles(BCR TB)belong to common heat transfer equipment in the field of chemical engineering,yet the complicated thermal-hydraulics performance of BCR TB has not been deeply revealed.To fill this gap,the present study proposes a novel variable bubble size modeling approach based on the Euler-Euler two-fluid framework,which is coupled with the population balance model considering comprehensive interphase forces.On the basis of verifying numerical reliability using experimental data,the mechanism of bubble swarm flow around the tube bundle and the effects of gas sparger configurations on the thermal-hydraulics performance of BCR TB are investigated.Results indicate that the entire tube bundle can be divided into three distinct zones,namely the sparger effect zone,fully developed zone and interface effect zone in view of the local mixture-to-wall heat transfer coefficient.The maximum peak value of the mixture-to-wall heat transfer coefficient always appears at 210°of heat exchange tubes.When the orifice diameter is 4 mm,the axial gradient of gas holdup is relatively large due to more intense shearing and fragmentation effects.Interestingly,the fractions of medium-sized and large-sized bubbles are not sensitive to orifice angle.Both the mixture-to-wall heat transfer coefficient and the friction factor decrease initially and then increase when the installation height increases.Under the optimized gas sparger structure configuration,the mixture-to-wall heat transfer coefficient increases by 10.23%,accompanied by the reduction of pressure drop by 8.14%,ultimately attaining a system energy conversion efficiency of 97.88%and performance evaluation criterion of 1.087.Finally,a new dimensionless and semi-theoretical Nusselt correlation incorporating a structural correction factor with an average absolute deviation of 5.15%is developed.The findings can offer useful guidance for the optimal design of BCR TB.展开更多
The internal pressure within fission gas bubbles(FGBs)in irradiated nuclear fuels drives mechanical interactions with the surrounding fuel skeleton.To investigate the micromechanical stress fields in irradiated nuclea...The internal pressure within fission gas bubbles(FGBs)in irradiated nuclear fuels drives mechanical interactions with the surrounding fuel skeleton.To investigate the micromechanical stress fields in irradiated nuclear fuels containing pressurized FGBs,a mechanical constitutive model for the equivalent solid of FGBs was developed and validated.This model was based on the modified Van der Waals equation,incorporating the effects of surface tension.Using this model,the micromechanical fields in irradiated U-10Mo fuels with randomly distributed FGBs were calculated during uniaxial tensile testing via the finite element(FE)method.The macroscopic elastic constants of the irradiated U-10Mo fuels were then derived using homogenization theory,and the influences of bubble pressure,bubble size,and porosity on these constants were examined.Results show that adjacent FGBs exhibit mechanical interactions,which leads to distinct stress concentrations in the surrounding fuel skeleton.The macroscopic elastic constants of irradiated U-10Mo fuels decrease with increasing the macroscopic porosity,which can be quantitatively described by the Mori-Tanaka model.In contrast,bubble pressure and size have negligible effects on these constants.展开更多
Spherical bubble oscillations are widely used to model cavitation phenomena in biomedical and naval hydrodynamic systems.During collapse,a sudden increase in surrounding pressure initiates the collapse of a cavitation...Spherical bubble oscillations are widely used to model cavitation phenomena in biomedical and naval hydrodynamic systems.During collapse,a sudden increase in surrounding pressure initiates the collapse of a cavitation bubble,followed by a rebound driven by the high internal gas pressure.While the ideal gas equation of state(EOS)is commonly used to describe the internal pressure and temperature of the bubble,it is limited in its capacity to capture molecular-level effects under highly compressed conditions.In the present study,we employ non-ideal EOS for the gas(the van der Waals EOS and its volume-limited case)to investigate bubble oscillations with a focus on energy redistribution.Bubble oscillation is modeled in two phases:collapse,described by the Keller−Miksis formulation,and rebound,where peak shock pressure is estimated using similitude-based relations.To assess the role of EOS in energy redistribution,we introduce a framework that quantifies energy components in the bubble−liquid system while conserving total energy,tailored to each EOS.Using this framework,we evaluate energy concentration,acoustic radiation,and shock propagation and statistically analyze their dependence on both the driving pressure and the EOS of gas.We statistically derive scaling relations of key bubble dynamics quantities,energy concentration and radiation,and shock pressure using the driving pressure ratio.This work provides a generalizable framework and set of scaling relations for predicting bubble dynamics and energy transfer,with potential applications in evaluating the impacts of cavitation phenomena in complex practical systems.展开更多
From the perspective of facilitating the design of fluidized hydrogen reduction reactors for iron ore powder and maintaining stable operation,the operational conditions and bubble behavior in stable state fluidization...From the perspective of facilitating the design of fluidized hydrogen reduction reactors for iron ore powder and maintaining stable operation,the operational conditions and bubble behavior in stable state fluidization of multi-particle size systems were investigated through cold-state experiments.To facilitate the identification of bubble behavior,a two-dimensional bubbling bed cold-state experiment was carried out using iron ore powder with a narrow particle size distribution and glass beads.Initially,the multi-stage fluidization characteristics of iron ore powder were examined.Then,using Geldart B-type glass beads to simulate a multi-particle size composition system,the particle size range and superficial gas velocity range for stable operation of the multi-particle composition system were explored.When the mass percentage of 150-μm glass beads was 15%,the stable fluidization operational gas velocity range was found to be(1.05-1.21)umf,where umf is the minimum fluidization velocity;when the content was 20%,the stable fluidized superficial gas velocity range was(1.09-1.26)umf.Under stable fluidization operating conditions,the dynamic behavior of bubbles(average equivalent diameter,rising velocity,and lateral migration velocity)was studied,and the quantitative relationship between the average equivalent diameter of bubbles and bed height in multi-particle size systems under stable fluidization conditions was also corrected.Additionally,the correlation between bubble rising velocity and bubble average equivalent diameter was established.展开更多
Bubble breakup at T-junction microchannels is the basis for the numbering-up of gas−liquid two-phase flow in parallelized microchannels. This article presents the bubble breakup in viscous liquids at a microfluidic T-...Bubble breakup at T-junction microchannels is the basis for the numbering-up of gas−liquid two-phase flow in parallelized microchannels. This article presents the bubble breakup in viscous liquids at a microfluidic T-junction. Nitrogen is used as the gas phase, and glycerol-water mixtures with different mass concentration of glycerol as the liquid phase. The evolution of the gas−liquid interface during bubble breakup at the microfluidic T-junction is explored. The thinning of the bubble neck includes the squeezing stage and the rapid pinch-off stage. In the squeezing stage, the power law relation is found between the minimum width of the bubble neck and the time, and the values of exponents α1 and α2 are influenced by the viscous force. The values of pre-factors m_(1) and m_(2) are negatively correlated with the capillary number. In the rapid pinch-off stage, the thinning of the bubble neck is predominated by the surface tension, and the minimum width of the bubble neck can be scaled with the remaining time as power-law. The propagation of the bubble tip can be characterized by the power law between the movement distance and the time, with decreasing exponent as increased liquid viscosity.展开更多
In recent years,the phenomenon of multistability has attracted wide attention.In this paper,a memristive chaotic system with extreme multistability is constructed by using a memristor.The dynamic behavior of the syste...In recent years,the phenomenon of multistability has attracted wide attention.In this paper,a memristive chaotic system with extreme multistability is constructed by using a memristor.The dynamic behavior of the system is analyzed by Poincar´e mapping,a time series diagram,and a bifurcation diagram.The results show that the new system has several significant characteristics.First,the new system has a constant Lyapunov exponent,transient chaos and one complete Feigenbaum tree.Second,the system has the phenomenon of bifurcation map shifts that depend on the initial conditions.In addition,we find periodic bursting oscillations,chaotic bursting oscillations,and the transition of chaotic bursting oscillations to periodic bursting oscillations.In particular,when the system parameters take different discrete values,the system generates a bubble phenomenon that varies with the initial conditions,and this bubble can be shifted with the initial values,which has rarely been seen in the previous literature.The implementation by field-programmable gate array(FPGA)and analog circuit simulation show close alignment with the MATLAB numerical simulation results,validating the system’s realizability.Additionally,the image encryption algorithm integrating DNA-based encoding and chaotic systems further demonstrates its practical applicability.展开更多
In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,whi...In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,which is consistent with previously reported experimental findings.Analysis of the flow in the annular film region indicates that the influence of tube wall oscillations is minimal.This suggests that the effect of tube oscillations is essentially equivalent to that of an oscillating piston above the bubble,leading to a similar mechanism for bubble deceleration.Using a theoretical formula from the literature,we demonstrate that at sufficiently high frequencies,the amplitude of the tube velocity oscillations becomes the sole control parameter affecting bubble deceleration.This study enhances our understanding of Taylor bubble behavior in mechanically oscillating environments and provides useful insights into the design of control strategies for Taylor bubble motion in vertical slug flows.展开更多
This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix wi...This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix with nano-sized VCr precipitates.VCr is chemical-disordered and TiNi has a B2-ordered structure.The alloy was subjected to 400 keV He ion irradiation with a fluence of 1×10^(17)ions cm^(−2)at 450℃.The results show He bubbles within the chemical-disordered VCr matrix exhibit a near-spherical shape with a smaller size and higher density compared to that in chemical-ordered TiNi phase with a larger size,lower density,and faceted shape.This indicates the chemical-disordered VCr phase effectively suppresses He accumulation compared to the B2-ordered TiNi phase,emphasizing the dominance of chemical struc-tures in He bubble formation.The calculation of density functional theory(DFT)shows that Ti and Ni have lower vacancy formation energy than that of V and Cr,respectively,which results in the increased vacancy production in TiNi.Consequently,He bubbles in TiNi have a larger bubble size consistent with experimental observations of radiation-induced Ni segregation.These findings elucidate the roles of or-dered and disordered chemical structures in He bubble evolution,offering insights for the development of gas ion irradiation-resistant materials.展开更多
Using the recently proposed bubble equation,we study the vibration characteristics of a bubble close to a solid boundary.The results indicate that a rigid boundary has an important effect on large-amplitude bubble vib...Using the recently proposed bubble equation,we study the vibration characteristics of a bubble close to a solid boundary.The results indicate that a rigid boundary has an important effect on large-amplitude bubble vibration.Whether the bubble vibration is stable or unstable strongly depends on the distance between the initial bubble center and the solid boundary.Furthermore,it also depends on both the amplitude and the frequency of the external perturbation.It is found that the smaller the distance between the initial bubble center and the solid boundary,the larger the initial bubble radius and the larger both the amplitude and frequency of the external perturbation,the more easily the bubble vibration becomes unstable.It is shown that this unstable bubble vibration is possibly related to the production of a reentrant microjet for the bubble,which suggests a potential method for estimating bubble size and the distance between the bubble center and the solid boundary by exerting an external perturbation with controllable amplitude and frequency on the liquid.Furthermore,the dependence of the natural frequency of the bubble on the external pressure for small-amplitude vibration can reveal the bubble radius and the distance between the bubble center and the solid boundary.In addition,the vibration characteristics of a bubble close to a solid boundary under a periodic external perturbation are revealed.Several bubble vibration modes are identified;the strongest vibration modes are those with the natural frequency and the external vibration frequency.展开更多
Bubbles play crucial roles in various fields,including naval and ocean engineering,chemical engineering,and biochemical engineering.Numerous theoretical analyses,numerical simulations,and experimental studies have bee...Bubbles play crucial roles in various fields,including naval and ocean engineering,chemical engineering,and biochemical engineering.Numerous theoretical analyses,numerical simulations,and experimental studies have been conducted to reveal the mysteries of bubble motion and its mechanisms.These efforts have significantly advanced research in bubble dynamics,where theoretical study is an efficient method for bubble motion prediction.Since Lord Rayleigh introduced the theoretical model of single-bubble motion in incompressible fluid in 1917,theoretical studies have been pivotal in understanding bubble dynamics.This study provides a comprehensive review of the development and applicability of theoretical studies in bubble dynamics using typical theoretical bubble models across different periods as a focal point and an overview of bubble theory applications in underwater explosion,marine cavitation,and seismic exploration.This study aims to serve as a reference and catalyst for further advancements in theoretical analysis and practical applications of bubble theory across marine fields.展开更多
The effects of internals on liquid mixing and gas-liquid mass transfer have rarely been investigated in bubble columns,and the commonly used measurement method overestimates significantly overall gas holdup.Firstly,ga...The effects of internals on liquid mixing and gas-liquid mass transfer have rarely been investigated in bubble columns,and the commonly used measurement method overestimates significantly overall gas holdup.Firstly,gas holdup measurement method is improved by conducting multi-point liquid level measurement and using net fluid volume instead of bed volume to calculate gas holdup.Then,a stable conductivity method for liquid macromixing has been established by shielding large bubbles using#16nylon mesh.Subsequently,the influences of internal coverage(=12.6%,18.9% and 25.1%) on macroscopic fluid dynamics in a bubble column with a free wall area are systematically investigated.It is found that the presence of internals has a notable effect on macroscopic fluid dynamics.The overall gas holdup and gas-liquid volumetric mass transfer coefficient decrease,and the macromixing time decreases with the increase of internal cross-sectional area coverage.These are mainly caused by the uneven distribution of airflow due to the low resistance in the free wall area.This design makes maintenance easier,but in reality,the reactor performance has decreased.Further improvements will be made to the reactor performance based on such a configuration through flow guidance using baffles.展开更多
基金JSPS KAKENHI Grant Number16H06286 supports global GNSS ionospheric maps (TEC,ROTI,and detrended TEC maps) developed by the Institute for SpaceEarth Environmental Research (ISEE) of Nagoya Universitysupport of the 2024 JASSO Follow-up Research Fellowship Program for a 90-day visiting research at the Institute for Space-Earth Environmental Research (ISEE),Nagoya University+3 种基金the support received from Telkom University under the“Skema Penelitian Terapan Periode I Tahun Anggaran 2024”the Memorandum of Understanding for Research Collaboration on Regional Ionospheric Observation (No:092/SAM3/TE-DEK/2021)the National Institute of Information and Communications Technology (NICT) International Exchange Program 2024-2025(No.2024-007)support for a one-year visiting research at Hokkaido University
文摘This paper highlights the crucial role of Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signals and degrade positioning accuracy.Managed by the Indonesian Geospatial Information Agency(BIG),the Indonesia Continuously Operating Reference Station(Ina-CORS)network comprises over 300 GNSS receivers spanning equatorial to southern low-latitude regions.Ina-CORS is uniquely situated to monitor EPB generation,zonal drift,and dissipation across Southeast Asia.We provide a practical tool for EPB research,by sharing two-dimensional rate of Total Electron Content(TEC)change index(ROTI)derived from this network.We generate ROTI maps with a 10-minute resolution,and samples from May 2024 are publicly available for further scientific research.Two preliminary findings from the ROTI maps of Ina-CORS are noteworthy.First,the Ina-CORS ROTI maps reveal that the irregularities within a broader EPB structure persist longer,increasing the potential for these irregularities to migrate farther eastward.Second,we demonstrate that combined ROTI maps from Ina-CORS and GNSS receivers in East Asia and Australia can be used to monitor the development of ionospheric irregularities in Southeast and East Asia.We have demonstrated the combined ROTI maps to capture the development of ionospheric irregularities in the Southeast/East Asian sector during the G5 Geomagnetic Storm on May 11,2024.We observed simultaneous ionospheric irregularities in Japan and Australia,respectively propagating northwestward and southwestward,before midnight,whereas Southeast Asia’s equatorial and low-latitude regions exhibited irregularities post-midnight.By sharing ROTI maps from Indonesia and integrating them with regional GNSS networks,researchers can conduct comprehensive EPB studies,enhancing the understanding of EPB behavior across Southeast and East Asia and contributing significantly to ionospheric research.
基金Funded by the National Natural Science Foundation of China(No.52172007)。
文摘To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software integrated within the optical microscope,the diameter and number of the bubbles on the surface of three borosilicate glasses were quantified.From the hardness and crack initiation resistance(CR),we built the relationship between the porosity and the mechanical performance of these borosilicate glasses.
基金financially supported by the National Natural Science Foundation of China(Nos.52274315 and 52374320)the Fundamental Research Funds for the Central Universities(Nos.FRF-TP-22-011A1 and FRF-DF22-16)。
文摘During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid slag.In contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive information.Therefore,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding times.The results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles increases.In addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually decreases.In one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the large.These findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.
文摘In this paper,the failure caused by HRAM loads which were generated by high-speed projectile penetration,and protection technology of the fluid-filled structure were explored.A bubble was preset on the projectile trajectory in a fluid-filled structure.Based on the reflection and transmission phenomena of pressure waves at the gas-liquid interface and the compressibility characteristics of gases,a numerical analysis was conducted on the influence of preset bubble on projectile penetration and structural failure characteristics.The results indicate that the secondary water-entry impact phenomenon occurs when a preset bubble exists on the projectile trajectory,leading to the secondary water entry impact loads.The rarefaction waves reflected on the surface of the preset bubble cause the attenuation ratio of the initial impact pressure peak to reach 68.8%and the total specific impulse attenuation ratio to reach 48.6%.Furthermore,the larger the bubble,the faster the projectile,and the more obvious the attenuation effect.Moreover,due to the compressibility of the bubble,the global deformation attenuation ratio of the front and rear walls can reach over 80%.However,the larger the bubble size,the faster the projectile velocity,the smaller the local deformation attenuation effect of the rear wall,and the more severe the failure at the perforation of the rear wall.
基金funded by the Natural Science Foundation of China[U20A20292]Shandong Province Science andTechnology SMES InnovationAbility Improvement Project[2023TSGC0005]China Postdoctoral Science Foundation[2024M752697].
文摘In nature,cavitation bubbles typically appear in clusters,engaging in interactions that create a variety of dynamicmotion patterns.To better understand the behavior ofmultiple bubble collapses and the mechanisms of interbubble interaction,this study employs molecular dynamics simulation combined with a coarse-grained force field.By focusing on collapsemorphology,local density,and pressure,it elucidates how the number and arrangement of bubbles influence the collapse process.The mechanisms behind inter-bubble interactions are also considered.The findings indicate that the collapse speed of unbounded bubbles located in lateral regions is greater than that of the bubbles in the center.Moreover,it is shown that asymmetrical bubble distributions lead to a shorter collapse time overall.
基金Supported by the National Natural Science Foundation of China(U21B2069,52274020,52288101,52274022)National Key Research and Development Program of China(2022YFC2806504)。
文摘The gas-liquid countercurrent flow pattern is complex and the bubble migration velocity is difficult to predict in the process of bullheading well killing.The experiment on bubble migration in gas-liquid countercurrent flow in annulus is carried out under different working conditions to reveal how the wellbore inclination angle,liquid phase property and countercurrent liquid velocity affect the bubble deformation and bubble migration trajectory/velocity,and to establish a bubble migration velocity prediction model.The bubbles in the countercurrent flow mainly migrate in two modes:free rising of isolated bubbles,and interactive rising of multiple bubbles.The bubbles migrate by an S-shaped trajectory in the countercurrent flow.With the increase of countercurrent liquid velocity,the lateral oscillation of bubbles is intensified.The increases of wellbore inclination angle,liquid density and liquid viscosity make the bubble migration trajectory gradually to be linear.The bubble is generally ellipsoidal during its rising.The wellbore inclination angle has little effect on the degree of bubble deformation.The bubbles are ellipsoidal during rising,with little influence of wellbore inclination angle on bubble deformation.With the increase of liquid viscosity and density,the aspect ratio of the bubble decreases.As the wellbore inclination angle increases,the bubble migration velocity gradually decreases.As the liquid viscosity increases,the bubble migration velocity decreases.As the liquid density increases,the bubble migration velocity increases slightly.The established bubble migration velocity prediction model yields errors within±15%,and demonstrates broad applicability across a wide range of operating conditions.
基金supported by the National Natural Science Foundation of China(Grant No.12374441)。
文摘Bubbles within an elastic shell,which undergo ultrasound-driven oscillation to treat tumors and soft tissues,are frequently treated as viscoelastic media.Therefore,studying the dynamic behavior of bubbles wrapped in a viscoelastic medium while considering an elastic shell can provide theoretical support for ultrasound biotherapy.Bubbles are always in the form of clusters.Therefore,a model of spherical bubble clusters in a liquid cavity wrapped by an elastic shell was constructed,the coupled oscillation equations of bubbles were obtained by taking into account the dynamic effects of the elastic shell and the viscoelastic media outside the cavity,and the oscillation behaviors of the bubbles were analyzed.Acoustic waves at 1.5 MHz could cause bubbles with a radius of 1μm to resonate.Increasing the number of bubbles increased the suppressing effect of bubble oscillation caused by bubble interaction.The bubble cluster oscillation caused the elastic shell to oscillate and be stressed,and the stress trend was the inverse of the bubble oscillation trend with maximal tensile and compressive stresses.Bubbles with an equilibrium radius of 2μm exhibited the lowest inertial cavitation threshold,making inertial cavitation more likely under high-frequency acoustic excitation.The inertial cavitation threshold of bubbles was heavily influenced by the acoustic wave frequency,bubble number density,and bubble cluster radius.The nonspherical oscillation stability of bubbles was primarily affected by the driving acoustic pressure amplitude and frequency,bubble initial radius,bubble number density,and bubble cluster radius.The acoustic frequency and amplitude exhibited a synergistic effect,with a minimum unstable driving acoustic pressure threshold of approximately 0.13 MPa.The initial radius within the elastic shell affected the minimum unstable driving acoustic pressure threshold.
基金supported by the project 2024J01421supported by Fujian Provincial Natural Science Foundation.
文摘Bubble column reactors fitted with tube bundles(BCR TB)belong to common heat transfer equipment in the field of chemical engineering,yet the complicated thermal-hydraulics performance of BCR TB has not been deeply revealed.To fill this gap,the present study proposes a novel variable bubble size modeling approach based on the Euler-Euler two-fluid framework,which is coupled with the population balance model considering comprehensive interphase forces.On the basis of verifying numerical reliability using experimental data,the mechanism of bubble swarm flow around the tube bundle and the effects of gas sparger configurations on the thermal-hydraulics performance of BCR TB are investigated.Results indicate that the entire tube bundle can be divided into three distinct zones,namely the sparger effect zone,fully developed zone and interface effect zone in view of the local mixture-to-wall heat transfer coefficient.The maximum peak value of the mixture-to-wall heat transfer coefficient always appears at 210°of heat exchange tubes.When the orifice diameter is 4 mm,the axial gradient of gas holdup is relatively large due to more intense shearing and fragmentation effects.Interestingly,the fractions of medium-sized and large-sized bubbles are not sensitive to orifice angle.Both the mixture-to-wall heat transfer coefficient and the friction factor decrease initially and then increase when the installation height increases.Under the optimized gas sparger structure configuration,the mixture-to-wall heat transfer coefficient increases by 10.23%,accompanied by the reduction of pressure drop by 8.14%,ultimately attaining a system energy conversion efficiency of 97.88%and performance evaluation criterion of 1.087.Finally,a new dimensionless and semi-theoretical Nusselt correlation incorporating a structural correction factor with an average absolute deviation of 5.15%is developed.The findings can offer useful guidance for the optimal design of BCR TB.
基金National Natural Science Foundation of China(12135008,12132005)。
文摘The internal pressure within fission gas bubbles(FGBs)in irradiated nuclear fuels drives mechanical interactions with the surrounding fuel skeleton.To investigate the micromechanical stress fields in irradiated nuclear fuels containing pressurized FGBs,a mechanical constitutive model for the equivalent solid of FGBs was developed and validated.This model was based on the modified Van der Waals equation,incorporating the effects of surface tension.Using this model,the micromechanical fields in irradiated U-10Mo fuels with randomly distributed FGBs were calculated during uniaxial tensile testing via the finite element(FE)method.The macroscopic elastic constants of the irradiated U-10Mo fuels were then derived using homogenization theory,and the influences of bubble pressure,bubble size,and porosity on these constants were examined.Results show that adjacent FGBs exhibit mechanical interactions,which leads to distinct stress concentrations in the surrounding fuel skeleton.The macroscopic elastic constants of irradiated U-10Mo fuels decrease with increasing the macroscopic porosity,which can be quantitatively described by the Mori-Tanaka model.In contrast,bubble pressure and size have negligible effects on these constants.
基金supported by Institute of Information&Communications Technology Planning&Evaluation(IITP)grant funded by the Korea government(MSIT)(No.RS-2022-00155966Artificial Intelligence Convergence Innovation Human Resources Development(EwhaWomans University)).
文摘Spherical bubble oscillations are widely used to model cavitation phenomena in biomedical and naval hydrodynamic systems.During collapse,a sudden increase in surrounding pressure initiates the collapse of a cavitation bubble,followed by a rebound driven by the high internal gas pressure.While the ideal gas equation of state(EOS)is commonly used to describe the internal pressure and temperature of the bubble,it is limited in its capacity to capture molecular-level effects under highly compressed conditions.In the present study,we employ non-ideal EOS for the gas(the van der Waals EOS and its volume-limited case)to investigate bubble oscillations with a focus on energy redistribution.Bubble oscillation is modeled in two phases:collapse,described by the Keller−Miksis formulation,and rebound,where peak shock pressure is estimated using similitude-based relations.To assess the role of EOS in energy redistribution,we introduce a framework that quantifies energy components in the bubble−liquid system while conserving total energy,tailored to each EOS.Using this framework,we evaluate energy concentration,acoustic radiation,and shock propagation and statistically analyze their dependence on both the driving pressure and the EOS of gas.We statistically derive scaling relations of key bubble dynamics quantities,energy concentration and radiation,and shock pressure using the driving pressure ratio.This work provides a generalizable framework and set of scaling relations for predicting bubble dynamics and energy transfer,with potential applications in evaluating the impacts of cavitation phenomena in complex practical systems.
基金supported by the China Baowu Low Carbon Metallurgy Innovation Foundation(No.202114)National Natural Science Foundation of China(No.51874056)Sichuan Science and Technology Program(2025ZNSFSC0378).
文摘From the perspective of facilitating the design of fluidized hydrogen reduction reactors for iron ore powder and maintaining stable operation,the operational conditions and bubble behavior in stable state fluidization of multi-particle size systems were investigated through cold-state experiments.To facilitate the identification of bubble behavior,a two-dimensional bubbling bed cold-state experiment was carried out using iron ore powder with a narrow particle size distribution and glass beads.Initially,the multi-stage fluidization characteristics of iron ore powder were examined.Then,using Geldart B-type glass beads to simulate a multi-particle size composition system,the particle size range and superficial gas velocity range for stable operation of the multi-particle composition system were explored.When the mass percentage of 150-μm glass beads was 15%,the stable fluidization operational gas velocity range was found to be(1.05-1.21)umf,where umf is the minimum fluidization velocity;when the content was 20%,the stable fluidized superficial gas velocity range was(1.09-1.26)umf.Under stable fluidization operating conditions,the dynamic behavior of bubbles(average equivalent diameter,rising velocity,and lateral migration velocity)was studied,and the quantitative relationship between the average equivalent diameter of bubbles and bed height in multi-particle size systems under stable fluidization conditions was also corrected.Additionally,the correlation between bubble rising velocity and bubble average equivalent diameter was established.
基金supports for this project from State Key Laboratory of Chemical Safety(SKLCS–2024001)are gratefully acknowledged。
文摘Bubble breakup at T-junction microchannels is the basis for the numbering-up of gas−liquid two-phase flow in parallelized microchannels. This article presents the bubble breakup in viscous liquids at a microfluidic T-junction. Nitrogen is used as the gas phase, and glycerol-water mixtures with different mass concentration of glycerol as the liquid phase. The evolution of the gas−liquid interface during bubble breakup at the microfluidic T-junction is explored. The thinning of the bubble neck includes the squeezing stage and the rapid pinch-off stage. In the squeezing stage, the power law relation is found between the minimum width of the bubble neck and the time, and the values of exponents α1 and α2 are influenced by the viscous force. The values of pre-factors m_(1) and m_(2) are negatively correlated with the capillary number. In the rapid pinch-off stage, the thinning of the bubble neck is predominated by the surface tension, and the minimum width of the bubble neck can be scaled with the remaining time as power-law. The propagation of the bubble tip can be characterized by the power law between the movement distance and the time, with decreasing exponent as increased liquid viscosity.
基金Project supported by the Natural Science Foundation of Hubei Province(Grant No.2024AFD068).
文摘In recent years,the phenomenon of multistability has attracted wide attention.In this paper,a memristive chaotic system with extreme multistability is constructed by using a memristor.The dynamic behavior of the system is analyzed by Poincar´e mapping,a time series diagram,and a bifurcation diagram.The results show that the new system has several significant characteristics.First,the new system has a constant Lyapunov exponent,transient chaos and one complete Feigenbaum tree.Second,the system has the phenomenon of bifurcation map shifts that depend on the initial conditions.In addition,we find periodic bursting oscillations,chaotic bursting oscillations,and the transition of chaotic bursting oscillations to periodic bursting oscillations.In particular,when the system parameters take different discrete values,the system generates a bubble phenomenon that varies with the initial conditions,and this bubble can be shifted with the initial values,which has rarely been seen in the previous literature.The implementation by field-programmable gate array(FPGA)and analog circuit simulation show close alignment with the MATLAB numerical simulation results,validating the system’s realizability.Additionally,the image encryption algorithm integrating DNA-based encoding and chaotic systems further demonstrates its practical applicability.
基金supported by the National Natural Science Foundation of China(Grant No.12202441).
文摘In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,which is consistent with previously reported experimental findings.Analysis of the flow in the annular film region indicates that the influence of tube wall oscillations is minimal.This suggests that the effect of tube oscillations is essentially equivalent to that of an oscillating piston above the bubble,leading to a similar mechanism for bubble deceleration.Using a theoretical formula from the literature,we demonstrate that at sufficiently high frequencies,the amplitude of the tube velocity oscillations becomes the sole control parameter affecting bubble deceleration.This study enhances our understanding of Taylor bubble behavior in mechanically oscillating environments and provides useful insights into the design of control strategies for Taylor bubble motion in vertical slug flows.
基金supported by the National Magnetic Con-finement Fusion Energy Research Project from the Ministry of Science and Technology of China(No.2022YFE03030004 and 2019YFE03120003)the National Natural Science Foundation of China(No.12275010,12275176,12275001,12335017,11921006,U21B2082,U22B2064 and U20B2025)+3 种基金the Beijing Municipal Natural Science Foundation(No.1222023)the Shenzhen Science and Technology Program(No.RCYX20210609103904028)Engang Fu acknowledges the support from the Science Fund or Creative Research Groups of NSFC,the Ion Beam Materials Laboratory(IBML)and Electron Microscopy Laboratory(EML)the High-performance Computing Platform(HPC)at Peking University.Xing Liu acknowledges the discussion with Prof.Ning Gao and Dr.Yifan Zhang.
文摘This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix with nano-sized VCr precipitates.VCr is chemical-disordered and TiNi has a B2-ordered structure.The alloy was subjected to 400 keV He ion irradiation with a fluence of 1×10^(17)ions cm^(−2)at 450℃.The results show He bubbles within the chemical-disordered VCr matrix exhibit a near-spherical shape with a smaller size and higher density compared to that in chemical-ordered TiNi phase with a larger size,lower density,and faceted shape.This indicates the chemical-disordered VCr phase effectively suppresses He accumulation compared to the B2-ordered TiNi phase,emphasizing the dominance of chemical struc-tures in He bubble formation.The calculation of density functional theory(DFT)shows that Ti and Ni have lower vacancy formation energy than that of V and Cr,respectively,which results in the increased vacancy production in TiNi.Consequently,He bubbles in TiNi have a larger bubble size consistent with experimental observations of radiation-induced Ni segregation.These findings elucidate the roles of or-dered and disordered chemical structures in He bubble evolution,offering insights for the development of gas ion irradiation-resistant materials.
基金supported by the National Natural Science Foundation of China(Grant No.12275223).
文摘Using the recently proposed bubble equation,we study the vibration characteristics of a bubble close to a solid boundary.The results indicate that a rigid boundary has an important effect on large-amplitude bubble vibration.Whether the bubble vibration is stable or unstable strongly depends on the distance between the initial bubble center and the solid boundary.Furthermore,it also depends on both the amplitude and the frequency of the external perturbation.It is found that the smaller the distance between the initial bubble center and the solid boundary,the larger the initial bubble radius and the larger both the amplitude and frequency of the external perturbation,the more easily the bubble vibration becomes unstable.It is shown that this unstable bubble vibration is possibly related to the production of a reentrant microjet for the bubble,which suggests a potential method for estimating bubble size and the distance between the bubble center and the solid boundary by exerting an external perturbation with controllable amplitude and frequency on the liquid.Furthermore,the dependence of the natural frequency of the bubble on the external pressure for small-amplitude vibration can reveal the bubble radius and the distance between the bubble center and the solid boundary.In addition,the vibration characteristics of a bubble close to a solid boundary under a periodic external perturbation are revealed.Several bubble vibration modes are identified;the strongest vibration modes are those with the natural frequency and the external vibration frequency.
文摘Bubbles play crucial roles in various fields,including naval and ocean engineering,chemical engineering,and biochemical engineering.Numerous theoretical analyses,numerical simulations,and experimental studies have been conducted to reveal the mysteries of bubble motion and its mechanisms.These efforts have significantly advanced research in bubble dynamics,where theoretical study is an efficient method for bubble motion prediction.Since Lord Rayleigh introduced the theoretical model of single-bubble motion in incompressible fluid in 1917,theoretical studies have been pivotal in understanding bubble dynamics.This study provides a comprehensive review of the development and applicability of theoretical studies in bubble dynamics using typical theoretical bubble models across different periods as a focal point and an overview of bubble theory applications in underwater explosion,marine cavitation,and seismic exploration.This study aims to serve as a reference and catalyst for further advancements in theoretical analysis and practical applications of bubble theory across marine fields.
基金National Natural Science Foundation of China(22178228,22378271)are gratefully acknowledged。
文摘The effects of internals on liquid mixing and gas-liquid mass transfer have rarely been investigated in bubble columns,and the commonly used measurement method overestimates significantly overall gas holdup.Firstly,gas holdup measurement method is improved by conducting multi-point liquid level measurement and using net fluid volume instead of bed volume to calculate gas holdup.Then,a stable conductivity method for liquid macromixing has been established by shielding large bubbles using#16nylon mesh.Subsequently,the influences of internal coverage(=12.6%,18.9% and 25.1%) on macroscopic fluid dynamics in a bubble column with a free wall area are systematically investigated.It is found that the presence of internals has a notable effect on macroscopic fluid dynamics.The overall gas holdup and gas-liquid volumetric mass transfer coefficient decrease,and the macromixing time decreases with the increase of internal cross-sectional area coverage.These are mainly caused by the uneven distribution of airflow due to the low resistance in the free wall area.This design makes maintenance easier,but in reality,the reactor performance has decreased.Further improvements will be made to the reactor performance based on such a configuration through flow guidance using baffles.
