To solve the problem of temperature rise caused by the high power density of high-speed permanent magnet synchronous traction motors,the temperature rise of various components in the motor is analyzed by coupling the ...To solve the problem of temperature rise caused by the high power density of high-speed permanent magnet synchronous traction motors,the temperature rise of various components in the motor is analyzed by coupling the equivalent thermal circuit method and computational fluid dynamics.Also,a cooling strategy is proposed to solve the problem of temperature rise,which is expected to prolong the service life of these devices.First,the theoretical bases of the approaches used to study heat transfer and fluid mechanics are discussed,then the fluid flow for the considered motor is analyzed,and the equivalent thermal circuit method is introduced for the calculation of the temperature rise.Finally,the stator,rotor loss,motor temperature rise,and the proposed cooling method are also explored through experiments.According to the results,the stator temperature at 50,000 r/min and 60,000 r/min at no-load operation is 68℃ and 76℃,respectively.By monitoring the temperature of the air outlets inside and outside the motor at different speeds,it is also found that the motor reaches a stable temperature rise after 65 min of operation.Coupling of the thermal circuit method and computational fluid dynamics is a strategy that can provide the average temperature rise of each component and can also comprehensively calculate the temperature of each local point.We conclude that a hybrid cooling strategy based on axial air cooling of the inner air duct of the motor and water cooling of the stator can meet the design requirements for the ventilation and cooling of this type of motors.展开更多
Cavitating jet is widely used in drilling,rock cutting and ocean re source exploitation because of its stro ng erosion ability.The analysis of the relationship between the flow characteristics and the structure of cav...Cavitating jet is widely used in drilling,rock cutting and ocean re source exploitation because of its stro ng erosion ability.The analysis of the relationship between the flow characteristics and the structure of cavitating jet nozzle is critical.Here,we utilized 3 D printed technology and high-speed photography to design visualization experime nts to analyse the impact of the variation of resonator and throat size of the organ-pipe self-resonating cavitating nozzles on the cavitation characteristics through image processing.The velocity field,pressure field and vapor volume fraction injected by the nozzle were taken as the objective functions to study the influence of different structural parameters on the cavitation effect based on FLUENT 19.0 software,and the results were compared with the experimental results.The results show that increasing the length and diameter of the resonator contributes to the occurrence of cavitation and the structure stability of the flow field.However,excessive size affects self-resonant of the nozzle and makes it difficult to form resonance effect.In this study,the optimal values of nozzle throat length and divergent angle are twice the throat diameter and 40°,respectively.This research provides an integrated research method to study the optimization of self-resonating nozzle and cavitating jet characteristics.展开更多
To study the influence of the pantograph fixing position on aerodynamic characteristics of high-speed trains, the aerodynamic models of high-speed trains with eight cars were established based on the theory of com- pu...To study the influence of the pantograph fixing position on aerodynamic characteristics of high-speed trains, the aerodynamic models of high-speed trains with eight cars were established based on the theory of com- putational fluid dynamics, and eight cases with pantographs fixed on different positions and in different operational orientations were considered. The pantographs were fixed on the front or the rear end of the first middle car or fixed on the front or the rear end of the last middle car. The external flow fields of the high-speed trains were numeri- cally simulated using the software STAR-CCM＋. The results show that the pantograph fixing position has little effect on the aerodynamic drag force of the head car and has a large effect on the aerodynamic drag force of the tail car. The influences of the pantograph fixing position on the aerodynamic lift forces of the head car, tail car and pan- tographs are obvious. Among the eight cases, considering the total aerodynamic drag force of the train and the aerodynamic lift force of the lifted pantograph, when the pantographs are fixed on the rear end of the last middle car and the lifted pantograph is in the knuckle-upstream ori- entation, the aerodynamic performance of the high-speed train is the best.展开更多
Increasing velocity combined with decreasing mass of modern highspeed trains poses a question about the influence of strong crosswinds on its aerodynamics. Strong crosswinds may affect the running stability of high sp...Increasing velocity combined with decreasing mass of modern highspeed trains poses a question about the influence of strong crosswinds on its aerodynamics. Strong crosswinds may affect the running stability of high speed trains via the amplified aerodynamic forces and moments. In this study, a simulation of turbulent crosswind flows over the leading and end cars of ICE2 highspeed train was performed at different yaw angles in static and moving ground case scenarios. Since the train aerodynamic problems are closely associated with the flows occurring around train, the flow around the train was considered as incompressible and was obtained by solving the incom pressible form of the unsteady Reynoldsaveraged Navier Stokes （RANS） equations combined with the realizable kepsilon turbulence model. Important aerodynamic coef ficients such as the side force and rolling moment coeffi cients were calculated for yaw angles ranging from 30° to 60° and compared with the results obtained from wind tunnel test. The dependence of the flow structure on yaw angle was also presented. The nature of the flow field and its structure depicted by contours of velocity magnitude and streamline patterns along the train＇s crosssection were presented for different yaw angles. In addition, the pressure coefficient around the circumference of the train at dif ferent locations along its length was computed for yaw angles of 30° and 60°, The computed aerodynamic coef ficient outcomes using the realizable kepsilon turbulencemodel were in good agreement with the wind tunnel data. Both the side force coefficient and rolling moment coeffi cients increase steadily with yaw angle till about 50° before starting to exhibit an asymptotic behavior. Contours of velocity magnitude were also computed at different cross sections of the train along its length for different yaw angles. The result showed that magnitude of rotating vortex in the lee ward side increased with increasing yaw angle, which leads to the creation of a lowpressure region in the lee ward side of the train causing high side force and roll moment. Generally, this study shows that unsteady CFD RANS methods combined with an appropriate turbulence model can present an important means of assessing the crucial aerodynamic forces and moments of a highspeed train under strong crosswind conditions.展开更多
Fluid dynamics simulation is often repeated under varying conditions.This leads to a generation of large amounts of results,which are difficult to compare.To compare results under different conditions,it is effective ...Fluid dynamics simulation is often repeated under varying conditions.This leads to a generation of large amounts of results,which are difficult to compare.To compare results under different conditions,it is effective to overlap the streamlines generated from each condition in a single three-dimensional space.Streamline is a curved line,which represents a wind flow.This paper presents a technique to automatically select and visualize important streamlines that are suitable for the comparison of the simulation results.Additionally,we present an implementation to observe the flow fields in virtual reality spaces.展开更多
To find a better way to estimate the lift force induced by an interceptor on a high-speed mono-hull ship,a series of high-speed mono-hull ship models are designed and investigated under different conditions.Different ...To find a better way to estimate the lift force induced by an interceptor on a high-speed mono-hull ship,a series of high-speed mono-hull ship models are designed and investigated under different conditions.Different lift forces are obtained by numerical calculations and validated by a model test in a towing tank.The factors that influence the force are the interceptor height,velocity,draft,and deadrise angle.The relationship between each factor and the induced lift force is investigated and obtained.We found that the induced lift mainly depends on the interceptor height and advancing velocity,and is proportional to the square of the interceptor height and velocity.The results also showed that the effects of the draft and deadrise angle are relatively less important,and the relationship between the induced lift and these two factors is generally linear.Based on the results,a formula including the combined effect of all factors used to estimate the lift force induced by the interceptor is developed based on systematic analysis.The proposed formula could be used to estimate the lift force induced by interceptors,especially under high-speed condition.展开更多
Aiming to mitigate the aerodynamic lift force imbalance between pantograph strips,which exacerbates wear and affects the current collection performance of the pantograph-catenary system,a study has been conducted to s...Aiming to mitigate the aerodynamic lift force imbalance between pantograph strips,which exacerbates wear and affects the current collection performance of the pantograph-catenary system,a study has been conducted to support the beam deflector optimization using a combination of experimental measurements and computational fluid dynamics(CFD)simulations.The results demonstrate that the size,position,and installation orientation of the wind deflectors significantly influence the amount of force compensation.They also indicate that the front strip deflectors should be installed downwards and the rear strip deflectors upwards,thereby forming a“π”shape.Moreover,the lift force compensation provided by the wind deflectors increases with the size of the deflector.Alternative wind compensation strategies,such as control circuits,are also discussed,putting emphasis on the pros and cons of various pantograph types and wind compensation approaches.展开更多
Taylor vortex flow between two concentric rotating cylinders with finite axial length includes various patterns of laminar and turbulent flows, and its behavior has attracted great interests. When mode bifurcation occ...Taylor vortex flow between two concentric rotating cylinders with finite axial length includes various patterns of laminar and turbulent flows, and its behavior has attracted great interests. When mode bifurcation occurs, quantitative parameters such as the volume-averaged energy change rapidly. It is important to visualize the behaviors of vortices. In this study, a three-dimensional visualization system with respect to time is devised. This system can change the viewpoint of flow visualization, and we can observe the track of a vortex from any point. The volume-averaged energy is projected to the track of the center of a vortex. The proposed system can help to investigate the relationship between the mode bifurcation process and the volume-averaged energy.展开更多
Dear Editor,We introduce a novel surgical instrument designed to overcome the challenges in draining fluid from the suprachoroidal space in patients with choroidal detachment.In the evolving landscape of ophthalmic su...Dear Editor,We introduce a novel surgical instrument designed to overcome the challenges in draining fluid from the suprachoroidal space in patients with choroidal detachment.In the evolving landscape of ophthalmic surgeries,procedures that were once considered complex,such as those for choroidal detachment,are becoming increasingly common.Drainage of subchoroidal fluid was derived from 1985[1]with indirect visualization during scleral buckle surgery[2-4].展开更多
In order to efficiently and realistically capture microscopic features of fluid surface,a fast and stable surface feature simulation approach for particle-based fluids is presented in this paper.This method employs a ...In order to efficiently and realistically capture microscopic features of fluid surface,a fast and stable surface feature simulation approach for particle-based fluids is presented in this paper.This method employs a steady tension and adhesion model to construct surface features with the consideration of the adsorption effect of fluid to solid.Molecular cohesion and surface area minimization are appended for surface tension,and adhesion is added to better show the microscopic characteristics of fluid surface.Besides,the model is integrated to an implicit incompressible smoothed particle hydrodynamics(SPH)method to improve the efficiency and stability of simulation.The experimental results demonstrate that the method can better simulates surface features in a variety of scenarios stably and efficiently.展开更多
AIM:To provide a detailed description of the natural history of persistent subretinal fluid(SRF)after successful repair of rhegmatogenous retinal detachment(RRD)and its association with visual outcome.METHODS:This was...AIM:To provide a detailed description of the natural history of persistent subretinal fluid(SRF)after successful repair of rhegmatogenous retinal detachment(RRD)and its association with visual outcome.METHODS:This was a prospective long-term follow-up for eyes undergoing scleral buckling(SB)surgery for maculaoff RRD.Examinations were carried out preoperatively and postoperatively at 1,3,6,9 and 12 mo,until persistent SRF had completely resolved.One month postoperatively,optical coherence tomography(OCT)was used to classify SRF into three patterns:bleb-like loculated(BL),shallow-diffused(SD),and multiple blebs(MB).Serial OCT imaging was used to evaluate morphological changes in SRF until its complete disappearance.Patients were divided into two groups depending on the presence or absence of persistent SRF.RESULTS:A total of 59 patients(59 eyes)were included.There were no statistical differences between two groups at baseline,except for the proportion of patients with high myopia and a younger age.One month after surgery,OCT detected persistent SRF in 49 eyes(83.1%).The 3 morphological patterns of SRF were observed in 27 eyes(55.1%)with BL,13 eyes(26.5%)with SD,and 9 eyes(18.4%)with MB.The mean time for complete absorption differed significantly across the three SRF patterns(F=8.097,P=0.001),which was 8.8±6.1,20.1±12.1,and 16.7±10.2 mo in BL,SD,and MB,respectively.In 9 of the 13 eyes with SD,the pattern transformed into MB type.In cases involving MB,the size and number of blebs decreased gradually until they had been completely absorbed.Eyes with persistent SRF were more likely to demonstrate disruption of the ellipsoid zone(49.0%vs 10%,P=0.034).The final best-corrected visual acuity of two groups was 0.37±0.11(with SRF)vs 0.34±0.12(without SRF)logMAR(P=0.499),respectively.CONCLUSION:High preoperative myopia and younger age are associated with persistent SRF.BL is the most commonly observed pattern with the shortest duration and gradually disappeared.Most cases involving SD SRF transform into MB type during resolution.The size and number of the MBs decrease gradually until they were completely absorbed.The absence of persistent SRF may contribute to slow visual recovery in the short-term but does not influence the final visual outcome.展开更多
AIM: To explore an improved procedure involving incomplete fluid-air exchange for idiopathic macular hole(IMH), and the closure rate, visual function, and the visual field of macular holes(MHs) were evaluated.METHODS:...AIM: To explore an improved procedure involving incomplete fluid-air exchange for idiopathic macular hole(IMH), and the closure rate, visual function, and the visual field of macular holes(MHs) were evaluated.METHODS: This prospective randomized controlled study, included 40 eyes of 40 patients with IMH who were treated with pars plana vitrectomy and peeling of the internal limiting membrane. They were grouped by random digital table. Twenty-one eyes underwent incomplete fluidair exchange(IFA) and 19 eyes underwent traditional complete fluid-air exchange(CFA) as the control group. Outcomes included best-corrected visual acuity(BCVA), intraocular pressure, and optical coherence tomography, light adaptive electroretinography, and visual field evaluations.RESULTS: All MHs <400 μm were successfully closed. BCVAs before and 6 mo after surgery were 0.82±0.41 logMAR and 0.28±0.17 logMAR in IFA group and 0.86±0.34 logMAR and 0.34±0.23 logMAR in CFA group, respectively. The electroretinogram analysis of patients in IFA group revealed increases in b-wave amplitudes at 1, 3, and 6 mo after surgery. Additionally, patients in IFA group showed an amplitude increase of 28.6% from baseline at 6 mo(P<0.05), while no obvious improvements were noted in CFA group. Although there were no statistically significant improvements in either group, the IFA group showed a slight increase in mean sensitivity(P>0.05).CONCLUSION: IFA is a reliable method that offers comparable closure rate to CFA and facilitates improvements in visual function.展开更多
Transparent flow field visualization techniques play a critical role in engineering and scientific applications.They provide a clear and intuitive means to understand fluid dynamics and its complex phenomena,such as l...Transparent flow field visualization techniques play a critical role in engineering and scientific applications.They provide a clear and intuitive means to understand fluid dynamics and its complex phenomena,such as laminar flow,turbulence,and vortices.However,achieving fully two-dimensional quantitative visualization of transparent flow fields under non-invasive conditions remains a significant challenge.Here,we present an approach for achieving flow field visualization by harnessing the synergistic effects of a dielectric metasurface array endowed with photonic spindecoupled capability.This approach enables the simultaneous acquisition of light-field images containing flow field information in two orthogonal dimensions,which allows for the real-time and quantitative derivation of multiple physical parameters.As a proof-of-concept,we experimentally demonstrate the applicability of the proposed visualization technique to various scenarios,including temperature field mapping,gas leak detection,visualization of various fluid physical phenomena,and 3D morphological reconstruction of transparent phase objects.This technique not only establishes an exceptional platform for advancing research in fluid physics,but also exhibits significant potential for broad applications in industrial design and vision.展开更多
随着城市环境问题的日益突出,通风廊道作为改善城市微气候的方法引起广泛关注,但缺乏系统性梳理研究。利用CiteSpace对Web of Science核心数据库中1997—2024年的487篇相关文献进行可视化处理,总结了研究进展和热点,为后续相关研究提供...随着城市环境问题的日益突出,通风廊道作为改善城市微气候的方法引起广泛关注,但缺乏系统性梳理研究。利用CiteSpace对Web of Science核心数据库中1997—2024年的487篇相关文献进行可视化处理,总结了研究进展和热点,为后续相关研究提供科学参考。结果表明,城市通风廊道研究合作薄弱;研究方法较为单一且缺少合理的方法组合;研究区存在分类问题;研究方向相对单一;研究与现实的关联相对薄弱且缺乏解决实际问题的具体策略。未来研究应突破技术层和策略层的界限,更注重在系统思维层面上构建多样化的城市通风廊道结构,深入挖掘电路理论、后向轨迹模拟、深度强化学习等新研究模式,并在逆向思维和健康、经济等新命题背景下,探寻新的研究方向。展开更多
文摘To solve the problem of temperature rise caused by the high power density of high-speed permanent magnet synchronous traction motors,the temperature rise of various components in the motor is analyzed by coupling the equivalent thermal circuit method and computational fluid dynamics.Also,a cooling strategy is proposed to solve the problem of temperature rise,which is expected to prolong the service life of these devices.First,the theoretical bases of the approaches used to study heat transfer and fluid mechanics are discussed,then the fluid flow for the considered motor is analyzed,and the equivalent thermal circuit method is introduced for the calculation of the temperature rise.Finally,the stator,rotor loss,motor temperature rise,and the proposed cooling method are also explored through experiments.According to the results,the stator temperature at 50,000 r/min and 60,000 r/min at no-load operation is 68℃ and 76℃,respectively.By monitoring the temperature of the air outlets inside and outside the motor at different speeds,it is also found that the motor reaches a stable temperature rise after 65 min of operation.Coupling of the thermal circuit method and computational fluid dynamics is a strategy that can provide the average temperature rise of each component and can also comprehensively calculate the temperature of each local point.We conclude that a hybrid cooling strategy based on axial air cooling of the inner air duct of the motor and water cooling of the stator can meet the design requirements for the ventilation and cooling of this type of motors.
基金financially supported by National Key Research and Development Program of China(No.2019YFB1504202)National Natural Science Foundation of China(No.52174009)State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing(No.PRP/open-1905)。
文摘Cavitating jet is widely used in drilling,rock cutting and ocean re source exploitation because of its stro ng erosion ability.The analysis of the relationship between the flow characteristics and the structure of cavitating jet nozzle is critical.Here,we utilized 3 D printed technology and high-speed photography to design visualization experime nts to analyse the impact of the variation of resonator and throat size of the organ-pipe self-resonating cavitating nozzles on the cavitation characteristics through image processing.The velocity field,pressure field and vapor volume fraction injected by the nozzle were taken as the objective functions to study the influence of different structural parameters on the cavitation effect based on FLUENT 19.0 software,and the results were compared with the experimental results.The results show that increasing the length and diameter of the resonator contributes to the occurrence of cavitation and the structure stability of the flow field.However,excessive size affects self-resonant of the nozzle and makes it difficult to form resonance effect.In this study,the optimal values of nozzle throat length and divergent angle are twice the throat diameter and 40°,respectively.This research provides an integrated research method to study the optimization of self-resonating nozzle and cavitating jet characteristics.
基金supported by the High-Speed Railway Basic Research Fund Key Project of China(Grant No.U1234208)the National Natural Science Foundation of China(Grant Nos.51475394 and 51605397)
文摘To study the influence of the pantograph fixing position on aerodynamic characteristics of high-speed trains, the aerodynamic models of high-speed trains with eight cars were established based on the theory of com- putational fluid dynamics, and eight cases with pantographs fixed on different positions and in different operational orientations were considered. The pantographs were fixed on the front or the rear end of the first middle car or fixed on the front or the rear end of the last middle car. The external flow fields of the high-speed trains were numeri- cally simulated using the software STAR-CCM＋. The results show that the pantograph fixing position has little effect on the aerodynamic drag force of the head car and has a large effect on the aerodynamic drag force of the tail car. The influences of the pantograph fixing position on the aerodynamic lift forces of the head car, tail car and pan- tographs are obvious. Among the eight cases, considering the total aerodynamic drag force of the train and the aerodynamic lift force of the lifted pantograph, when the pantographs are fixed on the rear end of the last middle car and the lifted pantograph is in the knuckle-upstream ori- entation, the aerodynamic performance of the high-speed train is the best.
文摘Increasing velocity combined with decreasing mass of modern highspeed trains poses a question about the influence of strong crosswinds on its aerodynamics. Strong crosswinds may affect the running stability of high speed trains via the amplified aerodynamic forces and moments. In this study, a simulation of turbulent crosswind flows over the leading and end cars of ICE2 highspeed train was performed at different yaw angles in static and moving ground case scenarios. Since the train aerodynamic problems are closely associated with the flows occurring around train, the flow around the train was considered as incompressible and was obtained by solving the incom pressible form of the unsteady Reynoldsaveraged Navier Stokes （RANS） equations combined with the realizable kepsilon turbulence model. Important aerodynamic coef ficients such as the side force and rolling moment coeffi cients were calculated for yaw angles ranging from 30° to 60° and compared with the results obtained from wind tunnel test. The dependence of the flow structure on yaw angle was also presented. The nature of the flow field and its structure depicted by contours of velocity magnitude and streamline patterns along the train＇s crosssection were presented for different yaw angles. In addition, the pressure coefficient around the circumference of the train at dif ferent locations along its length was computed for yaw angles of 30° and 60°, The computed aerodynamic coef ficient outcomes using the realizable kepsilon turbulencemodel were in good agreement with the wind tunnel data. Both the side force coefficient and rolling moment coeffi cients increase steadily with yaw angle till about 50° before starting to exhibit an asymptotic behavior. Contours of velocity magnitude were also computed at different cross sections of the train along its length for different yaw angles. The result showed that magnitude of rotating vortex in the lee ward side increased with increasing yaw angle, which leads to the creation of a lowpressure region in the lee ward side of the train causing high side force and roll moment. Generally, this study shows that unsteady CFD RANS methods combined with an appropriate turbulence model can present an important means of assessing the crucial aerodynamic forces and moments of a highspeed train under strong crosswind conditions.
文摘Fluid dynamics simulation is often repeated under varying conditions.This leads to a generation of large amounts of results,which are difficult to compare.To compare results under different conditions,it is effective to overlap the streamlines generated from each condition in a single three-dimensional space.Streamline is a curved line,which represents a wind flow.This paper presents a technique to automatically select and visualize important streamlines that are suitable for the comparison of the simulation results.Additionally,we present an implementation to observe the flow fields in virtual reality spaces.
基金financially supported by the National Key Research and Development Program of China(Grant No.2021YFC2800700)the National Natural Science Foundation of China(Grant Nos.52171330,52101379,52101380,51679053)+2 种基金the Project of Research and Development Plan in Key Areas of Guangdong Province(Grant No.2020B1111010002)the Foundation of Key Laboratory of Marine Environmental Survey Technology and Application,Ministry of Natural Resources(Grant No.MESTA-2021-B010)the Natural Science Foundation of Guangdong Province,China(Grant No.2021A1515012134)。
文摘To find a better way to estimate the lift force induced by an interceptor on a high-speed mono-hull ship,a series of high-speed mono-hull ship models are designed and investigated under different conditions.Different lift forces are obtained by numerical calculations and validated by a model test in a towing tank.The factors that influence the force are the interceptor height,velocity,draft,and deadrise angle.The relationship between each factor and the induced lift force is investigated and obtained.We found that the induced lift mainly depends on the interceptor height and advancing velocity,and is proportional to the square of the interceptor height and velocity.The results also showed that the effects of the draft and deadrise angle are relatively less important,and the relationship between the induced lift and these two factors is generally linear.Based on the results,a formula including the combined effect of all factors used to estimate the lift force induced by the interceptor is developed based on systematic analysis.The proposed formula could be used to estimate the lift force induced by interceptors,especially under high-speed condition.
文摘Aiming to mitigate the aerodynamic lift force imbalance between pantograph strips,which exacerbates wear and affects the current collection performance of the pantograph-catenary system,a study has been conducted to support the beam deflector optimization using a combination of experimental measurements and computational fluid dynamics(CFD)simulations.The results demonstrate that the size,position,and installation orientation of the wind deflectors significantly influence the amount of force compensation.They also indicate that the front strip deflectors should be installed downwards and the rear strip deflectors upwards,thereby forming a“π”shape.Moreover,the lift force compensation provided by the wind deflectors increases with the size of the deflector.Alternative wind compensation strategies,such as control circuits,are also discussed,putting emphasis on the pros and cons of various pantograph types and wind compensation approaches.
文摘Taylor vortex flow between two concentric rotating cylinders with finite axial length includes various patterns of laminar and turbulent flows, and its behavior has attracted great interests. When mode bifurcation occurs, quantitative parameters such as the volume-averaged energy change rapidly. It is important to visualize the behaviors of vortices. In this study, a three-dimensional visualization system with respect to time is devised. This system can change the viewpoint of flow visualization, and we can observe the track of a vortex from any point. The volume-averaged energy is projected to the track of the center of a vortex. The proposed system can help to investigate the relationship between the mode bifurcation process and the volume-averaged energy.
基金Supported by Science and Technology Foundation of Tianjin Eye Hospital(No.YKPY2207)Tianjin Key Medical Discipline(Specialty)Construction Project(No.TJYXZDXK-016A).
文摘Dear Editor,We introduce a novel surgical instrument designed to overcome the challenges in draining fluid from the suprachoroidal space in patients with choroidal detachment.In the evolving landscape of ophthalmic surgeries,procedures that were once considered complex,such as those for choroidal detachment,are becoming increasingly common.Drainage of subchoroidal fluid was derived from 1985[1]with indirect visualization during scleral buckle surgery[2-4].
基金Supported by the National Natural Science Foundation of China(61873299,61702036,61572075)Fundamental Research Funds for the Central Universities of China(FRF-TP-17-012A1)China Postdoctoral Science Foundation(2017M620619)
文摘In order to efficiently and realistically capture microscopic features of fluid surface,a fast and stable surface feature simulation approach for particle-based fluids is presented in this paper.This method employs a steady tension and adhesion model to construct surface features with the consideration of the adsorption effect of fluid to solid.Molecular cohesion and surface area minimization are appended for surface tension,and adhesion is added to better show the microscopic characteristics of fluid surface.Besides,the model is integrated to an implicit incompressible smoothed particle hydrodynamics(SPH)method to improve the efficiency and stability of simulation.The experimental results demonstrate that the method can better simulates surface features in a variety of scenarios stably and efficiently.
文摘AIM:To provide a detailed description of the natural history of persistent subretinal fluid(SRF)after successful repair of rhegmatogenous retinal detachment(RRD)and its association with visual outcome.METHODS:This was a prospective long-term follow-up for eyes undergoing scleral buckling(SB)surgery for maculaoff RRD.Examinations were carried out preoperatively and postoperatively at 1,3,6,9 and 12 mo,until persistent SRF had completely resolved.One month postoperatively,optical coherence tomography(OCT)was used to classify SRF into three patterns:bleb-like loculated(BL),shallow-diffused(SD),and multiple blebs(MB).Serial OCT imaging was used to evaluate morphological changes in SRF until its complete disappearance.Patients were divided into two groups depending on the presence or absence of persistent SRF.RESULTS:A total of 59 patients(59 eyes)were included.There were no statistical differences between two groups at baseline,except for the proportion of patients with high myopia and a younger age.One month after surgery,OCT detected persistent SRF in 49 eyes(83.1%).The 3 morphological patterns of SRF were observed in 27 eyes(55.1%)with BL,13 eyes(26.5%)with SD,and 9 eyes(18.4%)with MB.The mean time for complete absorption differed significantly across the three SRF patterns(F=8.097,P=0.001),which was 8.8±6.1,20.1±12.1,and 16.7±10.2 mo in BL,SD,and MB,respectively.In 9 of the 13 eyes with SD,the pattern transformed into MB type.In cases involving MB,the size and number of blebs decreased gradually until they had been completely absorbed.Eyes with persistent SRF were more likely to demonstrate disruption of the ellipsoid zone(49.0%vs 10%,P=0.034).The final best-corrected visual acuity of two groups was 0.37±0.11(with SRF)vs 0.34±0.12(without SRF)logMAR(P=0.499),respectively.CONCLUSION:High preoperative myopia and younger age are associated with persistent SRF.BL is the most commonly observed pattern with the shortest duration and gradually disappeared.Most cases involving SD SRF transform into MB type during resolution.The size and number of the MBs decrease gradually until they were completely absorbed.The absence of persistent SRF may contribute to slow visual recovery in the short-term but does not influence the final visual outcome.
基金Supported by National Natural Science Foundation of Xinjiang Autonomous Region, China (No.81460089)
文摘AIM: To explore an improved procedure involving incomplete fluid-air exchange for idiopathic macular hole(IMH), and the closure rate, visual function, and the visual field of macular holes(MHs) were evaluated.METHODS: This prospective randomized controlled study, included 40 eyes of 40 patients with IMH who were treated with pars plana vitrectomy and peeling of the internal limiting membrane. They were grouped by random digital table. Twenty-one eyes underwent incomplete fluidair exchange(IFA) and 19 eyes underwent traditional complete fluid-air exchange(CFA) as the control group. Outcomes included best-corrected visual acuity(BCVA), intraocular pressure, and optical coherence tomography, light adaptive electroretinography, and visual field evaluations.RESULTS: All MHs <400 μm were successfully closed. BCVAs before and 6 mo after surgery were 0.82±0.41 logMAR and 0.28±0.17 logMAR in IFA group and 0.86±0.34 logMAR and 0.34±0.23 logMAR in CFA group, respectively. The electroretinogram analysis of patients in IFA group revealed increases in b-wave amplitudes at 1, 3, and 6 mo after surgery. Additionally, patients in IFA group showed an amplitude increase of 28.6% from baseline at 6 mo(P<0.05), while no obvious improvements were noted in CFA group. Although there were no statistically significant improvements in either group, the IFA group showed a slight increase in mean sensitivity(P>0.05).CONCLUSION: IFA is a reliable method that offers comparable closure rate to CFA and facilitates improvements in visual function.
基金support from the Key Research and Development Program of the Ministry of Science and Technology of China(2022YFA1205000)the National Natural Science Foundation of China(12274217,12104225)+2 种基金the Natural Science Foundation of Jiangsu Province(BK20220068)Fundamental Research Funds for the Central UniversitiesThe authors acknowledge the technique support from the microfabrication center of the National Laboratory of Solid-State Microstructures.
文摘Transparent flow field visualization techniques play a critical role in engineering and scientific applications.They provide a clear and intuitive means to understand fluid dynamics and its complex phenomena,such as laminar flow,turbulence,and vortices.However,achieving fully two-dimensional quantitative visualization of transparent flow fields under non-invasive conditions remains a significant challenge.Here,we present an approach for achieving flow field visualization by harnessing the synergistic effects of a dielectric metasurface array endowed with photonic spindecoupled capability.This approach enables the simultaneous acquisition of light-field images containing flow field information in two orthogonal dimensions,which allows for the real-time and quantitative derivation of multiple physical parameters.As a proof-of-concept,we experimentally demonstrate the applicability of the proposed visualization technique to various scenarios,including temperature field mapping,gas leak detection,visualization of various fluid physical phenomena,and 3D morphological reconstruction of transparent phase objects.This technique not only establishes an exceptional platform for advancing research in fluid physics,but also exhibits significant potential for broad applications in industrial design and vision.
文摘随着城市环境问题的日益突出,通风廊道作为改善城市微气候的方法引起广泛关注,但缺乏系统性梳理研究。利用CiteSpace对Web of Science核心数据库中1997—2024年的487篇相关文献进行可视化处理,总结了研究进展和热点,为后续相关研究提供科学参考。结果表明,城市通风廊道研究合作薄弱;研究方法较为单一且缺少合理的方法组合;研究区存在分类问题;研究方向相对单一;研究与现实的关联相对薄弱且缺乏解决实际问题的具体策略。未来研究应突破技术层和策略层的界限,更注重在系统思维层面上构建多样化的城市通风廊道结构,深入挖掘电路理论、后向轨迹模拟、深度强化学习等新研究模式,并在逆向思维和健康、经济等新命题背景下,探寻新的研究方向。
