Numerous irradiation-induced gas bubbles are created in the nuclear fuel during irradiation, leading to the change of microstructure and the degradation of mechanical and thermal properties. The grain size of fuel is ...Numerous irradiation-induced gas bubbles are created in the nuclear fuel during irradiation, leading to the change of microstructure and the degradation of mechanical and thermal properties. The grain size of fuel is one of the important factors affecting bubble evolution. In current study, we first predict the thermodynamic behaviors of point defects as well as the interplay between vacancy and gas atom in both UO_(2) and U_(3)Si_(2) according to ab initio approach. Then, we establish the irradiation-induced bubble phase-field model to investigate the formation and evolution of intra-and inter-granular gas bubbles. The effects of fission rate and temperature on the evolutions of bubble morphologies in UO_(2) and U_(3)Si_(2) have been revealed. Especially, a comparison of porosities under different grain sizes is examined and analyzed. To understand the thermal conductivity as functions of grain size and porosity, the heat transfer capability of U_(3)Si_(2) is evaluated.展开更多
In this study,the effect of rotating gas bubble stirring treatment on the microstructures of semi-solid AZ91-2Ca alloy was investigated.The semi-solid slurry was produced by injecting fine gas bubbles into the melt th...In this study,the effect of rotating gas bubble stirring treatment on the microstructures of semi-solid AZ91-2Ca alloy was investigated.The semi-solid slurry was produced by injecting fine gas bubbles into the melt through a rotating steel diffuser during solidification,and the samples of semi-solid slurry were taken by the rapid quenching method.The results show that fine and sphericalα-Mg particles can be obtained under rotating gas bubble stirring treatment.The process parameters such as gas flow rate,cooling rate and rotation speed have significant influence on the morphology of primary solid particles.After rotating gas bubble stirring treatment,the higher the particle density,the finer and rounder the primaryα-Mg particles.The formation of numerous solid particles is due to the combination mechanisms of copious nucleation and dendrite fragmentation.展开更多
AIM:To investigate the incidence and the predisposing factors of anterior chamber(AC)gas bubbles during femtosecond laser(FS)flap creation for laser in situ keratomileusis(LASIK).METHODS:All patients who underwent FS-...AIM:To investigate the incidence and the predisposing factors of anterior chamber(AC)gas bubbles during femtosecond laser(FS)flap creation for laser in situ keratomileusis(LASIK).METHODS:All patients who underwent FS-LASIK surgery at CMU LASIK Center between January 2013 and May 2016 were retrospective reviewed.Preoperative and intraoperative data including keratometry,white-towhite(WTW)corneal diameter,flap parameters(diameter,thickness,hinge position,and tunnel length)and pulse energy were reviewed and compared between incident group and control group.To determine the risk factors,univariate and multivariate conditional logistic regression were used;the eye was unit of analysis.RESULTS:The incidence of AC gas bubbles was 1.6%(22 out of 1378 eyes).The median WTW in the AC bubbles group was 11.5 mm(range 11.1-12.1),which was significantly different from the control group(11.7 mm,range 10.5-12.8,P=0.021).The result of the median WTW minus the flap diameter in the AC bubbles group was 2.5 mm(range 2.1-3.2),which was statistically different to the control group(2.7 mm,range 1.5-3.8,P=0.008).The logistic regression analysis showed that the result of the WTW minus the flap diameter in the AC bubbles group had an adjusted odds ratio of 0.204(95%CI;0.056-0.747,P=0.016).CONCLUSION:Development of AC gas bubbles during FS flap creation is not an uncommon event in Asian eyes which typically have a small WTW.The flap diameter when adjusted relatively to the WTW is a predisposing factor to the possibility of AC gas bubbles occurrence.展开更多
This paper presents an algorithm of automatic bubble image segmentation using the improved ant colony optimization methodology. The ant colony optimization method is a metaheuristic algorithm, and has been applied in ...This paper presents an algorithm of automatic bubble image segmentation using the improved ant colony optimization methodology. The ant colony optimization method is a metaheuristic algorithm, and has been applied in many fields. To reveal the versatility and appropriateness of automatic bubble image segmentation, the fuzzy clustering analysis method is employed in ant colony optimization algorithm. Compared with the well-known image feature extraction operators such as SUSAN and Canny, the proposed method can comparatively suitable to extract the gas bubbles image edge features. The experimental results show that the proposed method is effective and reliable, and can achieve satisfactory image edge extraction effect.展开更多
Electrochemical gas evolution reactions are common but essential in many electrochemical processes including water electrolysis.During these processes,gas bubbles are constantly nucleating on reaction interfaces in el...Electrochemical gas evolution reactions are common but essential in many electrochemical processes including water electrolysis.During these processes,gas bubbles are constantly nucleating on reaction interfaces in electrolyte and consequently exert an impact on catalysts and the performance.In the past few decades,extensive studies have been conducted to characterize bubbles with emerging advanced technologies,manage behaviors of bubbles,and apply bubbles to various domains.In this review,we summarize representative discoveries as well as recent advancements in electrochemical gas evolution reactions from the perspective of gas bubbles.Finally,we end up this review with a profound outlook on future research topics from the combination of experiments and theoretical techniques,non-negligible bubble effects,gravity-free situation,and reactions under practical industrial conditions.展开更多
The parasitic hydrogen evolution reaction(HER)in the negative half-cell of vanadium redox flow batteries(VRFBs)causes severe efficiency losses.Thus,a deeper understanding of this process and the accompanying bubble fo...The parasitic hydrogen evolution reaction(HER)in the negative half-cell of vanadium redox flow batteries(VRFBs)causes severe efficiency losses.Thus,a deeper understanding of this process and the accompanying bubble formation is crucial.This benchmarking study locally analyzes the bubble distribution in thick,porous electrodes for the first time using deep learning-based image segmentation of synchrotron X-ray micro-tomograms.Each large three-dimensional data set was processed precisely in less than one minute while minimizing human errors and pointing out areas of increased HER activity in VRFBs.The study systematically varies the electrode potential and material,concluding that more negative electrode potentials of-200 m V vs.reversible hydrogen electrode(RHE)and lower cause more substantial bubble formation,resulting in bubble fractions of around 15%–20%in carbon felt electrodes.Contrarily,the bubble fractions stay only around 2%in an electrode combining carbon felt and carbon paper.The detected areas with high HER activity,such as the border subregion with more than 30%bubble fraction in carbon felt electrodes,the cutting edges,and preferential spots in the electrode bulk,are potential-independent and suggest that larger electrodes with a higher bulk-to-border ratio might reduce HER-related performance losses.The described combination of electrochemical measurements,local X-ray microtomography,AI-based segmentation,and 3D morphometric analysis is a powerful and novel approach for local bubble analysis in three-dimensional porous electrodes,providing an essential toolkit for a broad community working on bubble-generating electrochemical systems.展开更多
The amount of methane leaked from deep sea cold seeps is enormous and potentially affects the global warming,ocean acidification and global carbon cycle.It is of great significance to study the methane bubble movement...The amount of methane leaked from deep sea cold seeps is enormous and potentially affects the global warming,ocean acidification and global carbon cycle.It is of great significance to study the methane bubble movement and dissolution process in the water column and its output to the atmosphere.Methane bubbles produce strong acoustic impedance in water bodies,and bubble strings released from deep sea cold seeps are called"gas flares"which expressed as flame-like strong backscatter in the water column.We characterized the morphology and movement of methane bubbles released into the water using multibeam water column data at two cold seeps.The result shows that methane at site I reached 920 m water depth without passing through the top of the gas hydrate stability zone(GHSZ,850 m),while methane bubbles at site II passed through the top of the GHSZ(597 m)and entered the non-GHSZ(above 550 m).By applying two methods on the multibeam data,the bubble rising velocity in the water column at sites I and II were estimated to be 9.6 cm/s and 24 cm/s,respectively.Bubble velocity is positively associated with water depth which is inferred to be resulted from decrease of bubble size during methane ascending in the water.Combined with numerical simulation,we concluded that formation of gas hydrate shells plays an important role in helping methane bubbles entering the upper water bodies,while other factors,including water depth,bubble velocity,initial kinetic energy and bubble size,also influence the bubble residence time in the water and the possibility of methane entering the atmosphere.We estimate that methane gas flux at these two sites is 0.4×10~6–87.6×10~6 mol/a which is extremely small compared to the total amount of methane in the ocean body,however,methane leakage might exert significant impact on the ocean acidification considering the widespread distributed cold seeps.In addition,although methane entering the atmosphere is not observed,further research is still needed to understand its potential impact on increasing methane concentration in the surface seawater and gas-water interface methane exchange rate,which consequently increase the greenhouse effect.展开更多
Mass transfer at hydrogen evolving mercury electrode has been studied by determining mass transfer coefficients of indicator ions as the function of current density of hydrogen evolution for various kinds of indica to...Mass transfer at hydrogen evolving mercury electrode has been studied by determining mass transfer coefficients of indicator ions as the function of current density of hydrogen evolution for various kinds of indica tor ions in sulphuric acid solution.Mercury adhering to metal substrates of Ni,Cu or Ag is used as mercury electrode to overcome its trembling during the electrolysis.The effect of difTerent indicator ions,electrode character istic,substrate material,diameter of electrode and temperature is examined.It is found that the transfer coefficient is proportional to the mass square root of current density of hydrogen evolution.展开更多
The bubble migration in liquid titanium alloy melt during vertical centrifugal casting process has been predicted. The effects of different parameters, such as the initial bubble location, the mold rotational speed an...The bubble migration in liquid titanium alloy melt during vertical centrifugal casting process has been predicted. The effects of different parameters, such as the initial bubble location, the mold rotational speed and the mold rotational direction on the bubble in the migration process are investigated. The results show that the bubble migration can be divided into the radial movement to the mould rotation axis and the circular movement to the mould wall opposite to rotational direction of the casting mould. The casting mould wall has an impeditive effect on the circular movement of the bubble during its migration process. And the bubble finally migrates like a straight line along the mould wall located at the opposite direction of the rotational casting mould whether it rotates clockwise or anti-clockwise. The bubbles at the position near the mould wall located at the opposite direction of the rotational casting mould are much easier to migrate in a straight line. The instantaneous speed of the gas bubble increases with the increment of the mould rotational speed. However the mould rotational speed is high or low, the moving speed of the gas bubble increases slightly at the primary stage, and then decreases gradually like a ladder.展开更多
Mesoscale drag model is of crucial significance for the reliability and accuracy in coarse-grid EulerianEulerian two-fluid model(TFM)simulations of gas-solid flow hydrodynamics in fluidized bed reactors.Although numer...Mesoscale drag model is of crucial significance for the reliability and accuracy in coarse-grid EulerianEulerian two-fluid model(TFM)simulations of gas-solid flow hydrodynamics in fluidized bed reactors.Although numerous mesoscale drag models have been reported in the literature,a systematic comparison of their prediction capability from the perspective of heterogeneity analysis is still lacking.In this study,in order to investigate the effect of several typical drag models on the hydrodynamic behaviors,the nonuniformity analysis and the sensitivity to material properties,extensive coarse-grid TFM simulations of a bubbling pilot-scale fluidized bed reactor are carried out.The results demonstrate that the mesoscale drag models outperform the empirical drag model in terms of nonuniformity due to the consideration of the influence of the mesoscale structures on the drag force in the bubbling region.Furthermore,the results reveal that our previously developed three-marker gradient-based drag model considering the solid concentration gradient exhibits satisfactory performance in predicting the bubbling flow hydrodynamics.Besides,the material-property-dependent drag model considering the explicit effect of material properties on drag corrections is most sensitive to the particle diameter.This work provides guideline for possible future improvements of mesoscale models to simulate gas-solid flow more accurately and universally.展开更多
Subretinal hemorrhage is a vision threatening complication of exudative age related macular degeneration(AMD) and polypoidal choroidal vasculopathy(PCV). Timely removal or displacement of subretinal hemorrhage from th...Subretinal hemorrhage is a vision threatening complication of exudative age related macular degeneration(AMD) and polypoidal choroidal vasculopathy(PCV). Timely removal or displacement of subretinal hemorrhage from the central macula, ideally within 7 to 10 days after onset, is critical to allowing potential recovery of vision. Surgical techniques with the use of a bubble to displace the subretinal hemorrhage can now be performed with tissue plasminogen activator to lyze the blood and with or without vitrectomy.展开更多
In this paper,a modified Rayleigh-Lamb equation is derived that takes into account the radial vibrations of a gas bubble coated with a viscoelastic shell and located in an elastic medium.For small oscillations of incl...In this paper,a modified Rayleigh-Lamb equation is derived that takes into account the radial vibrations of a gas bubble coated with a viscoelastic shell and located in an elastic medium.For small oscillations of inclusion,the problem of heat exchange between a gas,a liquid phase,a viscoelastic shell,and an elastic medium is solved.The energy integral is determined.In the case of small disturbances,the dispersion relation is found from the Rayleigh-Lamb equations,energy,and the known wave equation for the bubbly medium.An analytical expression of the equilibrium speed of sound is written out and its dependence on the size of the viscoelastic shell and the disturbance frequency is established.An example of a mixture of polydimethylsiloxane with air bubbles coated with a rubber shell illustrates the influence of the elasticity of the carrier medium and the shell of the bubbles on the dependence of the phase velocity and attenuation coefficient on the perturbation frequency.For a mixture of water with air bubbles coated with a rubber shell,the influence of the dependences of the shear modulus and viscosity of butyl rubber on the frequency of disturbances at different temperature on the dispersion curves is shown.A comparison of the theory with experimental data is given.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos.U2167217,12205286,and 11905025)the National MCF Energy Research and Development Program of China (Grant No.2018YFE0308105)。
文摘Numerous irradiation-induced gas bubbles are created in the nuclear fuel during irradiation, leading to the change of microstructure and the degradation of mechanical and thermal properties. The grain size of fuel is one of the important factors affecting bubble evolution. In current study, we first predict the thermodynamic behaviors of point defects as well as the interplay between vacancy and gas atom in both UO_(2) and U_(3)Si_(2) according to ab initio approach. Then, we establish the irradiation-induced bubble phase-field model to investigate the formation and evolution of intra-and inter-granular gas bubbles. The effects of fission rate and temperature on the evolutions of bubble morphologies in UO_(2) and U_(3)Si_(2) have been revealed. Especially, a comparison of porosities under different grain sizes is examined and analyzed. To understand the thermal conductivity as functions of grain size and porosity, the heat transfer capability of U_(3)Si_(2) is evaluated.
基金This project is sponsored by National Natural Science Foundation of China(No.51275295)Funded Projects of SAST-SJTU Joint Research Centre of Advanced Aerospace Technology(No.USCAST2012-15)Research Fund for the Doctoral Program of Higher Education of China(No.20120073120011).
文摘In this study,the effect of rotating gas bubble stirring treatment on the microstructures of semi-solid AZ91-2Ca alloy was investigated.The semi-solid slurry was produced by injecting fine gas bubbles into the melt through a rotating steel diffuser during solidification,and the samples of semi-solid slurry were taken by the rapid quenching method.The results show that fine and sphericalα-Mg particles can be obtained under rotating gas bubble stirring treatment.The process parameters such as gas flow rate,cooling rate and rotation speed have significant influence on the morphology of primary solid particles.After rotating gas bubble stirring treatment,the higher the particle density,the finer and rounder the primaryα-Mg particles.The formation of numerous solid particles is due to the combination mechanisms of copious nucleation and dendrite fragmentation.
文摘AIM:To investigate the incidence and the predisposing factors of anterior chamber(AC)gas bubbles during femtosecond laser(FS)flap creation for laser in situ keratomileusis(LASIK).METHODS:All patients who underwent FS-LASIK surgery at CMU LASIK Center between January 2013 and May 2016 were retrospective reviewed.Preoperative and intraoperative data including keratometry,white-towhite(WTW)corneal diameter,flap parameters(diameter,thickness,hinge position,and tunnel length)and pulse energy were reviewed and compared between incident group and control group.To determine the risk factors,univariate and multivariate conditional logistic regression were used;the eye was unit of analysis.RESULTS:The incidence of AC gas bubbles was 1.6%(22 out of 1378 eyes).The median WTW in the AC bubbles group was 11.5 mm(range 11.1-12.1),which was significantly different from the control group(11.7 mm,range 10.5-12.8,P=0.021).The result of the median WTW minus the flap diameter in the AC bubbles group was 2.5 mm(range 2.1-3.2),which was statistically different to the control group(2.7 mm,range 1.5-3.8,P=0.008).The logistic regression analysis showed that the result of the WTW minus the flap diameter in the AC bubbles group had an adjusted odds ratio of 0.204(95%CI;0.056-0.747,P=0.016).CONCLUSION:Development of AC gas bubbles during FS flap creation is not an uncommon event in Asian eyes which typically have a small WTW.The flap diameter when adjusted relatively to the WTW is a predisposing factor to the possibility of AC gas bubbles occurrence.
基金Sponsored by the"Liaoning Bai Qian Wan"Talents Program (Grant No.2007-186-25)the Program of Scientific Research Project of Liaoning Province Education Commission (Grant No.LS2010046)the National Commonweal Industry Scientific Research Project (Grant No.201003024)
文摘This paper presents an algorithm of automatic bubble image segmentation using the improved ant colony optimization methodology. The ant colony optimization method is a metaheuristic algorithm, and has been applied in many fields. To reveal the versatility and appropriateness of automatic bubble image segmentation, the fuzzy clustering analysis method is employed in ant colony optimization algorithm. Compared with the well-known image feature extraction operators such as SUSAN and Canny, the proposed method can comparatively suitable to extract the gas bubbles image edge features. The experimental results show that the proposed method is effective and reliable, and can achieve satisfactory image edge extraction effect.
基金supported by the National Natural Science Foundation of China(No.51902101)the Youth Natural Science Foundation of Hunan Province(No.2021JJ40044)+2 种基金Natural Science Foundation of Jiangsu Province(No.BK20201381)Science Foundation of Nanjing University of Posts and Telecommunications(Nos.NY219144 and NY221046)the National College Student Innovation and Entrepreneurship Training Program(No.202210293171K).
文摘Electrochemical gas evolution reactions are common but essential in many electrochemical processes including water electrolysis.During these processes,gas bubbles are constantly nucleating on reaction interfaces in electrolyte and consequently exert an impact on catalysts and the performance.In the past few decades,extensive studies have been conducted to characterize bubbles with emerging advanced technologies,manage behaviors of bubbles,and apply bubbles to various domains.In this review,we summarize representative discoveries as well as recent advancements in electrochemical gas evolution reactions from the perspective of gas bubbles.Finally,we end up this review with a profound outlook on future research topics from the combination of experiments and theoretical techniques,non-negligible bubble effects,gravity-free situation,and reactions under practical industrial conditions.
基金financial support through a KekuléPh.D.fellowship by the Fonds der Chemischen Industrie(FCI)support from the China Scholarship Council(No.202106950013)。
文摘The parasitic hydrogen evolution reaction(HER)in the negative half-cell of vanadium redox flow batteries(VRFBs)causes severe efficiency losses.Thus,a deeper understanding of this process and the accompanying bubble formation is crucial.This benchmarking study locally analyzes the bubble distribution in thick,porous electrodes for the first time using deep learning-based image segmentation of synchrotron X-ray micro-tomograms.Each large three-dimensional data set was processed precisely in less than one minute while minimizing human errors and pointing out areas of increased HER activity in VRFBs.The study systematically varies the electrode potential and material,concluding that more negative electrode potentials of-200 m V vs.reversible hydrogen electrode(RHE)and lower cause more substantial bubble formation,resulting in bubble fractions of around 15%–20%in carbon felt electrodes.Contrarily,the bubble fractions stay only around 2%in an electrode combining carbon felt and carbon paper.The detected areas with high HER activity,such as the border subregion with more than 30%bubble fraction in carbon felt electrodes,the cutting edges,and preferential spots in the electrode bulk,are potential-independent and suggest that larger electrodes with a higher bulk-to-border ratio might reduce HER-related performance losses.The described combination of electrochemical measurements,local X-ray microtomography,AI-based segmentation,and 3D morphometric analysis is a powerful and novel approach for local bubble analysis in three-dimensional porous electrodes,providing an essential toolkit for a broad community working on bubble-generating electrochemical systems.
基金The National Key Research and Development Plan under contract Nos 2018YFC0310000 and 2016YFC0304905-03the National Natural Science Foundation of China under contract No.41602149China Geological Survey Project under contract Nos DD20190582,DD20191009 and DD20160214。
文摘The amount of methane leaked from deep sea cold seeps is enormous and potentially affects the global warming,ocean acidification and global carbon cycle.It is of great significance to study the methane bubble movement and dissolution process in the water column and its output to the atmosphere.Methane bubbles produce strong acoustic impedance in water bodies,and bubble strings released from deep sea cold seeps are called"gas flares"which expressed as flame-like strong backscatter in the water column.We characterized the morphology and movement of methane bubbles released into the water using multibeam water column data at two cold seeps.The result shows that methane at site I reached 920 m water depth without passing through the top of the gas hydrate stability zone(GHSZ,850 m),while methane bubbles at site II passed through the top of the GHSZ(597 m)and entered the non-GHSZ(above 550 m).By applying two methods on the multibeam data,the bubble rising velocity in the water column at sites I and II were estimated to be 9.6 cm/s and 24 cm/s,respectively.Bubble velocity is positively associated with water depth which is inferred to be resulted from decrease of bubble size during methane ascending in the water.Combined with numerical simulation,we concluded that formation of gas hydrate shells plays an important role in helping methane bubbles entering the upper water bodies,while other factors,including water depth,bubble velocity,initial kinetic energy and bubble size,also influence the bubble residence time in the water and the possibility of methane entering the atmosphere.We estimate that methane gas flux at these two sites is 0.4×10~6–87.6×10~6 mol/a which is extremely small compared to the total amount of methane in the ocean body,however,methane leakage might exert significant impact on the ocean acidification considering the widespread distributed cold seeps.In addition,although methane entering the atmosphere is not observed,further research is still needed to understand its potential impact on increasing methane concentration in the surface seawater and gas-water interface methane exchange rate,which consequently increase the greenhouse effect.
基金supported by the Foundation of the State Education Commission for doctoral students
文摘Mass transfer at hydrogen evolving mercury electrode has been studied by determining mass transfer coefficients of indicator ions as the function of current density of hydrogen evolution for various kinds of indica tor ions in sulphuric acid solution.Mercury adhering to metal substrates of Ni,Cu or Ag is used as mercury electrode to overcome its trembling during the electrolysis.The effect of difTerent indicator ions,electrode character istic,substrate material,diameter of electrode and temperature is examined.It is found that the transfer coefficient is proportional to the mass square root of current density of hydrogen evolution.
基金Sponsored by the National Natural Science Foundation of China(Grant No.U1604254)the Initial Scientific Research Fund of Young Teachers in Henan University of Technology(Grant No.2013BS050)
文摘The bubble migration in liquid titanium alloy melt during vertical centrifugal casting process has been predicted. The effects of different parameters, such as the initial bubble location, the mold rotational speed and the mold rotational direction on the bubble in the migration process are investigated. The results show that the bubble migration can be divided into the radial movement to the mould rotation axis and the circular movement to the mould wall opposite to rotational direction of the casting mould. The casting mould wall has an impeditive effect on the circular movement of the bubble during its migration process. And the bubble finally migrates like a straight line along the mould wall located at the opposite direction of the rotational casting mould whether it rotates clockwise or anti-clockwise. The bubbles at the position near the mould wall located at the opposite direction of the rotational casting mould are much easier to migrate in a straight line. The instantaneous speed of the gas bubble increases with the increment of the mould rotational speed. However the mould rotational speed is high or low, the moving speed of the gas bubble increases slightly at the primary stage, and then decreases gradually like a ladder.
文摘Mesoscale drag model is of crucial significance for the reliability and accuracy in coarse-grid EulerianEulerian two-fluid model(TFM)simulations of gas-solid flow hydrodynamics in fluidized bed reactors.Although numerous mesoscale drag models have been reported in the literature,a systematic comparison of their prediction capability from the perspective of heterogeneity analysis is still lacking.In this study,in order to investigate the effect of several typical drag models on the hydrodynamic behaviors,the nonuniformity analysis and the sensitivity to material properties,extensive coarse-grid TFM simulations of a bubbling pilot-scale fluidized bed reactor are carried out.The results demonstrate that the mesoscale drag models outperform the empirical drag model in terms of nonuniformity due to the consideration of the influence of the mesoscale structures on the drag force in the bubbling region.Furthermore,the results reveal that our previously developed three-marker gradient-based drag model considering the solid concentration gradient exhibits satisfactory performance in predicting the bubbling flow hydrodynamics.Besides,the material-property-dependent drag model considering the explicit effect of material properties on drag corrections is most sensitive to the particle diameter.This work provides guideline for possible future improvements of mesoscale models to simulate gas-solid flow more accurately and universally.
文摘Subretinal hemorrhage is a vision threatening complication of exudative age related macular degeneration(AMD) and polypoidal choroidal vasculopathy(PCV). Timely removal or displacement of subretinal hemorrhage from the central macula, ideally within 7 to 10 days after onset, is critical to allowing potential recovery of vision. Surgical techniques with the use of a bubble to displace the subretinal hemorrhage can now be performed with tissue plasminogen activator to lyze the blood and with or without vitrectomy.
文摘In this paper,a modified Rayleigh-Lamb equation is derived that takes into account the radial vibrations of a gas bubble coated with a viscoelastic shell and located in an elastic medium.For small oscillations of inclusion,the problem of heat exchange between a gas,a liquid phase,a viscoelastic shell,and an elastic medium is solved.The energy integral is determined.In the case of small disturbances,the dispersion relation is found from the Rayleigh-Lamb equations,energy,and the known wave equation for the bubbly medium.An analytical expression of the equilibrium speed of sound is written out and its dependence on the size of the viscoelastic shell and the disturbance frequency is established.An example of a mixture of polydimethylsiloxane with air bubbles coated with a rubber shell illustrates the influence of the elasticity of the carrier medium and the shell of the bubbles on the dependence of the phase velocity and attenuation coefficient on the perturbation frequency.For a mixture of water with air bubbles coated with a rubber shell,the influence of the dependences of the shear modulus and viscosity of butyl rubber on the frequency of disturbances at different temperature on the dispersion curves is shown.A comparison of the theory with experimental data is given.
