Dear Editor,Despite substantial advances in neonatal medicine,retinopathy of prematurity(ROP)continues to be a serious therapeutic challenge⑴.Visual acuity loss in patients with ROP has been associated with structura...Dear Editor,Despite substantial advances in neonatal medicine,retinopathy of prematurity(ROP)continues to be a serious therapeutic challenge⑴.Visual acuity loss in patients with ROP has been associated with structural retinal abnormalities(including retinal detachment,retinal folds,and pigmentary retinopathy),cataract,glaucoma,and amblyopia due to refractive error or strabismus[2].展开更多
This paper extends the resource drag studies by empirically investigating how spatial factors affect the regional economic growth. Using spatial panel econometric models, this paper estimates the dragging effect of en...This paper extends the resource drag studies by empirically investigating how spatial factors affect the regional economic growth. Using spatial panel econometric models, this paper estimates the dragging effect of energy resources of the Yangtze River Delta metropolitan areas. We fi nd that the growth drag of energy in the Yangtze River Delta is about 6% on average, which means that energy constraints decrease the economic growth by 6% annually, higher than the national level that has been previously measured in the literature. This result has taken into account the impact of neighboring cities' economic development, so as to obtain a more accurate estimate. Based on these measurement results, we propose some policy recommendations.展开更多
The original mathematical treatment used in the analysis of the Fizeau experiment of 1851, which measured the relative speed of light in a moving medium, assumes that light travels through the water in a smooth contin...The original mathematical treatment used in the analysis of the Fizeau experiment of 1851, which measured the relative speed of light in a moving medium, assumes that light travels through the water in a smooth continuous flow, at a speed less than the speed of light in a vacuum (relative to the water). Thus, it assumes that the water’s velocity vector can simply be added to that of the light. However, light is transmitted through optical media, such as water, by a continuous process of charge excitation (semi-absorption) and re-emission by the water molecules;but travels between them at the full speed of light (in a vacuum). Thus, the mathematics describing the process of Fresnel dragging must be formulated differently and can then be explained by classical physics, allowing the entire process to be fully visualized.展开更多
A new scheme focusing on the surface plasmon polariton interferometry between the metal and dielectric interface is introduced. The phase shift is measured by using surface plasmon polariton wave, generated at the int...A new scheme focusing on the surface plasmon polariton interferometry between the metal and dielectric interface is introduced. The phase shift is measured by using surface plasmon polariton wave, generated at the interface of metallic and dielectric media. The phase shift of SPPs is modi?ed under phase and amplitude control of complex conductivity for interferometry. The control ?elds strongly in?uence the phase shift of SPPs for detection of molecular motion. The phase shift of SPPs is further modi?ed by Plasmon polariton Fizeaus dragging effect. We measure 20%–25%fractional change in delay and their phases shift between two left and right SPPs modes. Our results may have signi?cant applications in sensor interferometer technology.展开更多
In the light of Robinson and Wilczek's new idea,and motivated by Banerjee and Kulkarni's simplified method of using only the covariant anomaly to derive Hawking radiation from a black hole,we generally extend ...In the light of Robinson and Wilczek's new idea,and motivated by Banerjee and Kulkarni's simplified method of using only the covariant anomaly to derive Hawking radiation from a black hole,we generally extend the work to Kerr-Newman black hole in dragging coordinates frame.It is shown that the flows introduced to cancel the anomaly at the event horizon are equal to the corresponding Hawking radiation in dragging coordinates frame,which supports and extends Robinson and Wilczek's opinion.展开更多
The general relativistic frame dragging effect on the properties,such as the moments of inertia and the radiiof gyration of fast rotating neutron stars with a uniform strong magnetic field,is calculated accurate to th...The general relativistic frame dragging effect on the properties,such as the moments of inertia and the radiiof gyration of fast rotating neutron stars with a uniform strong magnetic field,is calculated accurate to the first orderin the uniform angular velocity.The results show that compared with the corresponding non-rotating static sphericalsymmetric neutron star with a weaker magnetic field,a fast rotating neutron star(millisecond pulsar)with a strongermagnetic field has a relative smaller moment of inertia and radius of gyration.展开更多
The interesting phenomenon of frame dragging which is associated with the rotation of the source in the field of Kerr family is discussed, and the angular velocity of an uncharged test particle is obtained with a stra...The interesting phenomenon of frame dragging which is associated with the rotation of the source in the field of Kerr family is discussed, and the angular velocity of an uncharged test particle is obtained with a straightforward mathematical method.展开更多
The classical theory of gravity, developed by Isaac Newton, predicts that the gravitational force between two masses is always colinear with the direction defined by the center of mass of both bodies. Some work done i...The classical theory of gravity, developed by Isaac Newton, predicts that the gravitational force between two masses is always colinear with the direction defined by the center of mass of both bodies. Some work done in the last 60 years has shown experimental evidence that the reality may be somehow more complex. That complexity was confirmed by the author of this paper and he goes farther announcing that the Sun is emitting particles with 44 m spatial periodicity that creates isotropic gravitational effects. Those effects are identical to the ones produced by dragging forces according to the General Theory of Relativity under the Kerr’s Metric. The purpose of this paper is to introduce experimental evidence confirming the author’s predictions that the Moon can modify the dragging force coming from the Sun’s core.展开更多
To date,several off-the-shelf products such as artificial blood vessel grafts have been reported and clinically tested for small diameter vessel(SDV)replacement.However,conventional artificial blood vessel grafts lack...To date,several off-the-shelf products such as artificial blood vessel grafts have been reported and clinically tested for small diameter vessel(SDV)replacement.However,conventional artificial blood vessel grafts lack endothelium and,thus,are not ideal for SDV transplantation as they can cause thrombosis.In addition,a suc-cessful artificial blood vessel graft for SDV must have sufficient mechanical properties to withstand various external stresses.Here,we developed a spontaneous cellular assembly SDV(S-SDV)that develops without additional intervention.By improving the dragging 3D printing technique,SDV constructs with free-form,multilayers and controllable pore size can be fabricated at once.Then,The S-SDV filled in the natural poly-mer bioink containing human umbilical vein endothelial cells(HUVECs)and human aorta smooth muscle cells(HAoSMCs).The endothelium can be induced by migration and self-assembly of endothelial cells through pores of the SDV construct.The antiplatelet adhesion of the formed endothelium on the luminal surface was also confirmed.In addition,this S-SDV had sufficient mechanical properties(burst pressure,suture retention,leakage test)for transplantation.We believe that the S-SDV could address the challenges of conventional SDVs:notably,endothelial formation and mechanical properties.In particular,the S-SDV can be designed simply as a free-form structure with a desired pore size.Since endothelial formation through the pore is easy even in free-form con-structs,it is expected to be useful for endothelial formation in vascular structures with branch or curve shapes,and in other tubular tissues such as the esophagus.展开更多
Coulomb drag refers to the phenomenon in which a current driven through one conducting layer induces a voltage nearby,electrically isolated layer sorely through interlayer Coulomb interactions between charge carriers....Coulomb drag refers to the phenomenon in which a current driven through one conducting layer induces a voltage nearby,electrically isolated layer sorely through interlayer Coulomb interactions between charge carriers.It has been extensively studied in various systems,including parallel nanowires,double quantum wells,and double-layer graphene.Here,we report the observation of Coulomb drag in a novel system consisting of two graphene layers separated laterally by a 30 nm gap within the material plane,exhibiting behavior distinct from that in vertical graphene heterostructures.Our experiments reveal pronounced negative drag resistances under an out-of-plane magnetic field at the quantum Hall edges,reaching a maximum when the carrier densities in both graphene layers are tuned to the charge neutrality point via gate voltages.Our work establish two separate and spatially closed quantum Hall edge modes as a new platform to explore electronic interaction physics between one dimensional systems.展开更多
Races using kitefoil and windfoil surfboards have been in the Olympic Games for the first time in Paris 2024,signalling their relevance in sailing sports.However,the dynamics of these devices is yet not well understoo...Races using kitefoil and windfoil surfboards have been in the Olympic Games for the first time in Paris 2024,signalling their relevance in sailing sports.However,the dynamics of these devices is yet not well understood,in particular the influence on the hydrodynamic forces and moments of the distance of the foil to the free surface.Considering this,the present paper documents an experimental investigation in which forces and torque produced,under uniform flow,by a full-scale state-of-the-art hydrofoil(suitable both for kitesurf and windsurf)were measured.A range of velocities,angles of attack,and submergences were tested,leading to Froude numbers based on submergence with maximum values around five,a typical range in actual sailing conditions.From these tests,formulae for the hydrodynamic coefficients have been proposed.They can be used for developing Velocity Prediction Programs(VPP)for this kind of craft,a necessary tool to plan racing configurations and to analyze their racing performance.With the aim of making the experimental data useful for benchmarking numerical models and for future research on related topics such as foil ventilation and transition to turbulence,the specimen’s 3D file is provided as supplementary material to this paper.展开更多
Aerodynamic research on road cars was reviewed in this work under the thread of reducing drag,with the awareness that this may succeed in effectively decreasing the carbon footprint of transportation.First,a selection...Aerodynamic research on road cars was reviewed in this work under the thread of reducing drag,with the awareness that this may succeed in effectively decreasing the carbon footprint of transportation.First,a selection of studies was presented to focus on the most important aerodynamic features of the flow around realistic car body shapes.Then,the discussion was organized around three pillars related to passive flow control,active flow control and active aerodynamics.Both experimental and numerical investigations were included to provide a comprehensive overview.A clear distinction was made between simplified and realistic car models,as well as production vehicles(within the limits of restricted access information).Moreover,a short essay was dedicated to electric vehicles,for which aerodynamics matters,especially at highway speeds.Last,the impact of aerodynamic principles on the design of current and future vehicle fleet was assessed,honestly admitting that recent market trends must be reversed to turn decarbonization goals into reality and damp the effects of global warming.展开更多
The effect of local polymer injection on a flat-plate turbulent boundary layer was investigated experimentally,with a particular focus on the distinct mechanisms of drag reduction in the low-drag reduction(LDR)and hig...The effect of local polymer injection on a flat-plate turbulent boundary layer was investigated experimentally,with a particular focus on the distinct mechanisms of drag reduction in the low-drag reduction(LDR)and high-drag reduction(HDR)states.High-resolution measurements of the near-wall flow field were achieved using particle tracking velocimetry(PTV),while large-field measurements covering the entire boundary layer were obtained through particle image velocimetry(PIV).It is found that in the LDR state,the mean shear and turbulence intensity in the near-wall region are mildly suppressed.The influence of polymer solution is limited to the near-wall region and does not affect the self-sustaining cycle of wall-bounded turbulence.Conversely,in the HDR state,the polymer solution effectively disrupts the self-sustaining process of wall-bounded turbulence by suppressing the lifting of the low-speed streaks.Consequently,the turbulence production is attenuated.The buffer layer is extended,and the slope of the log-law region also becomes larger when polymer concentration or the Weissenberg number increases.展开更多
Environmental pollution,energy consumption,and greenhouse gas emissions are critical global issues.To address these challenges,optimizing skimmer coatings is a major step in commercializing cleaning oil stains.This re...Environmental pollution,energy consumption,and greenhouse gas emissions are critical global issues.To address these challenges,optimizing skimmer coatings is a major step in commercializing cleaning oil stains.This research presents a novel approach to creating and refining oil absorbent coatings,introducing a unique oil spill removal skimmer enhanced with a super hydrophobic polyaniline(PANI)nanofiber coating.The goal of this study was to improve oil absorption performance,increase the contact angle,lower drag,reduce energy consumption,achieve high desirability,and lower production costs.PANI treated with hydrochloric acid was a key focus as it resulted in higher porosity and smaller pore diameters,providing a larger surface area,which are crucial factors for boosting oil absorption and minimizing drag.To optimize optimal nanofiber morphology,PANI synthesized with methanesulfonic acid was first dedoped and then redoped with hydrochloric acid.After optimization,the most effective skimmer coating was achieved using a formulation consisting of 0.1%PANI,an ammonium persulfate/aniline ratio of 0.4,and an acid/aniline ratio of 9.689,along with redoped PANI nanofibers.The optimized skimmer exhibited a remarkable contact angle of 177.477°.The coating achieved drag reduction of 32%,oil absorption of 88.725%,a cost of$1.710,and a desirability rating of 78.5%.In this study,an optimized skimmer coat containing super hydrophobic coat-PANI nanofibers was fabricated.By enhancing contact angle and reducing drag,these coatings increased the skimmer performance by improving oil absorption and reducing fuel consumption.展开更多
The dynamic behaviors of supercooled large water droplets(SLDs)in airflow involving deformation,breakup,and splash affect the local water collection coefficient,leading to an increase in the complexity of aircraft ici...The dynamic behaviors of supercooled large water droplets(SLDs)in airflow involving deformation,breakup,and splash affect the local water collection coefficient,leading to an increase in the complexity of aircraft icing.A parametric study on the influence of deformed water droplets in shear flow is investigated experimentally and numerically.A horizontal refrigerated wind tunnel is used to create the background shear airflow.A high-speed camera records the evolution of cross-stream/streamwise diameters and the breakup process.The level set method is employed to capture the deformation of micrometer-sized supercooled water droplets in continuous airflow.The deformation modes are categorized into five regimes:stabilization,vibration,transition,bag breakup,and bag-stamen breakup.A dimensionless deformation factor L is defined to describe the droplet deformation,which increases with airflow speed,droplet volume,and temperature.Applying the scaling expression Oh~(4.39)We~(0.85),a normalized acceleration model of water droplets in shear airflow is established.Based on the experimental results,a drag coefficient model for disc-shaped droplets within the transient Reynolds number range of 420-10000 is obtained.As the initial Weber number exceeds 9.5 and the maximum deformation factor exceeds 3.5,the droplet enters the breakup regime.Furthermore,bag-stamen breakup occurs when the initial Weber number exceeds 17.5.展开更多
Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graph...Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graphene-based electronic double-layer structures, revealing giant yet reproducible drag fluctuations at cryogenic temperatures. These fluctuations' characteristics, including amplitude and peak/valley spacing, are mainly determined by the drag layer's carrier dynamics rather than the drive layer's, resulting in violation of the Onsager reciprocity relation. Notably, the drag fluctuations remain observable up to 35 K, far exceeding universal conductance fluctuations within individual layers. This suggests enhanced phase coherence in inter-layer drag compared to single-layer transport, as further confirmed by quantitative analysis of auto-correlation fields of fluctuations under magnetic fields. Our findings provide new insights into quantum interference effects and their interplay with Coulomb interactions in solids. The observations of significant drag fluctuations could potentially help address chaotic signals between nearby components in nanoscale devices.展开更多
Inspired by the aquatic-adapted pit structures of the Cybister beetles that enable high-speed swimming,this study employs warp-knitted technology to fabricate drag-reduction swimwear textiles.Eight distinct fabric mor...Inspired by the aquatic-adapted pit structures of the Cybister beetles that enable high-speed swimming,this study employs warp-knitted technology to fabricate drag-reduction swimwear textiles.Eight distinct fabric morphologies were produced,and a self-developed high-precision dynamic drag measurement device was used to systematically analyze the mechanisms underlying the drag-reduction performance of these biomimetic pit structures.The device incorporates a servomotor,ball screw linkage,and high-precision tension sensor,enabling real-time and accurate detection of fluid drag forces.It effectively overcomes the limitations of traditional indirect measurement methods,including dynamic response lag and insufficient accuracy.Experimental results demonstrate that the hydrophobic small-pit fabric(4^(#))achieves an 84% drag reduction at 400 mm/s,outperforming the control sample(warp-knitted fabric 7^(#)).This significant reduction is attributed to the Cassie state established on the hydrophobic surface,which substantially decreases viscous drag and the microvortices generated by the pit structures,which delay flow separation and effectively minimize pressure drag.Furthermore,small-pit fabrics demonstrate a drag reduction rate 26% to 50% higher than that of large-pit structures,highlighting the critical importance of matching the pit scale to the thickness of the near-wall viscous sublayer for optimal drag reduction.This study establishes a theoretical foundation for the biomimetic design of high-performance drag-reduction swimsuits.The developed drag-measuring device also provides a standardized experimental platform for hydrodynamic studies of flexible materials,supporting a shift from empirical design methodologies to theory-driven approaches in drag-reduction technology and exhibiting significant potential for future advancements.展开更多
The rapid advancement of technology and the increasing speed of vehicles have led to a substantial rise in energy consumption and growing concern over environmental pollution.Beyond the promotion of new energy vehicle...The rapid advancement of technology and the increasing speed of vehicles have led to a substantial rise in energy consumption and growing concern over environmental pollution.Beyond the promotion of new energy vehicles,reducing aerodynamic drag remains a critical strategy for improving energy efficiency and lowering emissions.This study investigates the influence of key geometric parameters on the aerodynamic drag of vehicles.A parametric vehicle model was developed,and computational fluid dynamics(CFD)simulations were conducted to analyse variations in the drag coefficient(C_(d))and pressure distribution across different design configurations.The results reveal that the optimal aerodynamic performance—characterized by a minimized drag coefficient—is achieved with the following parameter settings:engine hood angle(α)of 15°,windshield angle(β)of 25°,rear window angle(γ)of 40°,rear upwards tail lift angle(θ)of 10°,ground clearance(d)of 100 mm,and side edge angle(s)of 5°.These findings offer valuable guidance for the aerodynamic optimization of vehicle body design and contribute to strategies aimed at energy conservation and emission reduction in the automotive sector.展开更多
The cutaneous ridges on dolphin skin have long been believed to effectively reduce friction drag, thereby contributing to overall drag reduction. However, since these skin ridges are oriented perpendicular to the swim...The cutaneous ridges on dolphin skin have long been believed to effectively reduce friction drag, thereby contributing to overall drag reduction. However, since these skin ridges are oriented perpendicular to the swimming direction, they also generate additional pressure drag, raising questions about the impact of the shape-induced pressure forces on swimming. Inspired by the microvibrations observed on dolphin skin, we hypothesize that the microstructure on dolphin skin is not static but dynamically oscillates in the form of Longitudinal Micro-Ultrasonic Waves (LMUWs). To explore this, we carried out a series of Computational Fluid Dynamics (CFD) simulations based on Large Eddy Simulation (LES) model to investigate the impact of pressure drag on the total drag acting on an oscillating skin surface under realistic turbulent flow conditions. The results indicate that the dynamic skin oscillations induce a new dynamic Stokes boundary layer, which has the potential to convert pressure drag into a negative force, thereby reducing total drag under the influence of traveling LMUW excitations. Furthermore, a relative velocity ξ, defined as the difference between the wave speed c and the external flow speed U, is introduced to evaluate the drag-reduction effect dominated by pressure. The findings reveal that pressure drag remains negative when ξ > 0. As ξ increases, the thrust effect induced by negative pressure becomes increasingly significant, ultimately counteracting friction drag and eliminating total drag. This pressure-dominated drag reduction mechanism thus demonstrates a novel strategy for the drag reduction technology and the potential of unveiling the mysteries behind dolphin swimming.展开更多
Reducing the resistance of vehicles,ships,aircraft and other means of transport during movement can significantly improve the speed,save energy and reduce emissions.After billions of years of continuous evolution,orga...Reducing the resistance of vehicles,ships,aircraft and other means of transport during movement can significantly improve the speed,save energy and reduce emissions.After billions of years of continuous evolution,organisms in nature have gradually developed the ability to move at high speed to achieve better survival.These evolved organisms provide a perfect template for the human development of drag reduction materials.Revealing the unique physiological structural characteristics of organisms and their relationship with resistance during movement can provide a feasible approach tosolving the problem of reducing friction resistance.Whether flying in the sky,running on the ground,swimming in the water,or even living in the soil,many creatures in various environments have the ability to reduce resistance.Driven by these inspirations,researchers have done a lot of work to explore and imitate these biological epidermis structures to achieve drag reduction.In this paper,the biomimetic drag reduction materials is introduced in detail in the order of drag reduction mechanism,structural characteristics of biological epidermis(including marine animals,flying animals,soil animals and plants),biomimetic preparation methods,performance testing methods and application fields.Finally,the potential of various biomimetic drag reduction materials in engineering application and the problems to be overcome are summarized and prospected.This paper can help readers comprehensively understand the research progress of biomimetic drag reduction materials,and provide reference for further designing the next generation of drag reduction materials.展开更多
基金Supported in part by the National Institute of Health,Bethesda,Maryland(Grant P30-EY014801)an unrestricted grant to the University of Miami from Research to Prevent Blindness,New York,New York,USA
文摘Dear Editor,Despite substantial advances in neonatal medicine,retinopathy of prematurity(ROP)continues to be a serious therapeutic challenge⑴.Visual acuity loss in patients with ROP has been associated with structural retinal abnormalities(including retinal detachment,retinal folds,and pigmentary retinopathy),cataract,glaucoma,and amblyopia due to refractive error or strabismus[2].
基金supported by the National Natural Science Foundation of China(Grant No.71373079)
文摘This paper extends the resource drag studies by empirically investigating how spatial factors affect the regional economic growth. Using spatial panel econometric models, this paper estimates the dragging effect of energy resources of the Yangtze River Delta metropolitan areas. We fi nd that the growth drag of energy in the Yangtze River Delta is about 6% on average, which means that energy constraints decrease the economic growth by 6% annually, higher than the national level that has been previously measured in the literature. This result has taken into account the impact of neighboring cities' economic development, so as to obtain a more accurate estimate. Based on these measurement results, we propose some policy recommendations.
文摘The original mathematical treatment used in the analysis of the Fizeau experiment of 1851, which measured the relative speed of light in a moving medium, assumes that light travels through the water in a smooth continuous flow, at a speed less than the speed of light in a vacuum (relative to the water). Thus, it assumes that the water’s velocity vector can simply be added to that of the light. However, light is transmitted through optical media, such as water, by a continuous process of charge excitation (semi-absorption) and re-emission by the water molecules;but travels between them at the full speed of light (in a vacuum). Thus, the mathematics describing the process of Fresnel dragging must be formulated differently and can then be explained by classical physics, allowing the entire process to be fully visualized.
文摘A new scheme focusing on the surface plasmon polariton interferometry between the metal and dielectric interface is introduced. The phase shift is measured by using surface plasmon polariton wave, generated at the interface of metallic and dielectric media. The phase shift of SPPs is modi?ed under phase and amplitude control of complex conductivity for interferometry. The control ?elds strongly in?uence the phase shift of SPPs for detection of molecular motion. The phase shift of SPPs is further modi?ed by Plasmon polariton Fizeaus dragging effect. We measure 20%–25%fractional change in delay and their phases shift between two left and right SPPs modes. Our results may have signi?cant applications in sensor interferometer technology.
基金supported by National Natural Science Foundation of China under Grant No.10773008
文摘In the light of Robinson and Wilczek's new idea,and motivated by Banerjee and Kulkarni's simplified method of using only the covariant anomaly to derive Hawking radiation from a black hole,we generally extend the work to Kerr-Newman black hole in dragging coordinates frame.It is shown that the flows introduced to cancel the anomaly at the event horizon are equal to the corresponding Hawking radiation in dragging coordinates frame,which supports and extends Robinson and Wilczek's opinion.
基金National Natural Science Foundation of China under Grant Nos.10647116 and 10575140the China Postdoctoral Science Foundation under Grant No.2005037175
文摘The general relativistic frame dragging effect on the properties,such as the moments of inertia and the radiiof gyration of fast rotating neutron stars with a uniform strong magnetic field,is calculated accurate to the first orderin the uniform angular velocity.The results show that compared with the corresponding non-rotating static sphericalsymmetric neutron star with a weaker magnetic field,a fast rotating neutron star(millisecond pulsar)with a strongermagnetic field has a relative smaller moment of inertia and radius of gyration.
文摘The interesting phenomenon of frame dragging which is associated with the rotation of the source in the field of Kerr family is discussed, and the angular velocity of an uncharged test particle is obtained with a straightforward mathematical method.
文摘The classical theory of gravity, developed by Isaac Newton, predicts that the gravitational force between two masses is always colinear with the direction defined by the center of mass of both bodies. Some work done in the last 60 years has shown experimental evidence that the reality may be somehow more complex. That complexity was confirmed by the author of this paper and he goes farther announcing that the Sun is emitting particles with 44 m spatial periodicity that creates isotropic gravitational effects. Those effects are identical to the ones produced by dragging forces according to the General Theory of Relativity under the Kerr’s Metric. The purpose of this paper is to introduce experimental evidence confirming the author’s predictions that the Moon can modify the dragging force coming from the Sun’s core.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2022R1A2C2008149,2021R1C1C1008767)the Korean Fund for Regenerative Medicine funded by Ministry of Science and ICT,and Ministry of Health and Welfare(21A0104L1,Republic of Korea)+1 种基金Korea Health Technology R&D Project through the Korea Health In-dustry Development Institute(KHIDI),funded by the Ministry of Health&Welfare,Republic of Korea(HI21C1100000021)the Alchemist Project(20012378,Development of Meta Soft Organ Module Manufacturing Technology without Immunity Rejection and Module Assembly Robot System)funded By the Ministry of Trade,Industry&Energy(MOTIE,Korea).
文摘To date,several off-the-shelf products such as artificial blood vessel grafts have been reported and clinically tested for small diameter vessel(SDV)replacement.However,conventional artificial blood vessel grafts lack endothelium and,thus,are not ideal for SDV transplantation as they can cause thrombosis.In addition,a suc-cessful artificial blood vessel graft for SDV must have sufficient mechanical properties to withstand various external stresses.Here,we developed a spontaneous cellular assembly SDV(S-SDV)that develops without additional intervention.By improving the dragging 3D printing technique,SDV constructs with free-form,multilayers and controllable pore size can be fabricated at once.Then,The S-SDV filled in the natural poly-mer bioink containing human umbilical vein endothelial cells(HUVECs)and human aorta smooth muscle cells(HAoSMCs).The endothelium can be induced by migration and self-assembly of endothelial cells through pores of the SDV construct.The antiplatelet adhesion of the formed endothelium on the luminal surface was also confirmed.In addition,this S-SDV had sufficient mechanical properties(burst pressure,suture retention,leakage test)for transplantation.We believe that the S-SDV could address the challenges of conventional SDVs:notably,endothelial formation and mechanical properties.In particular,the S-SDV can be designed simply as a free-form structure with a desired pore size.Since endothelial formation through the pore is easy even in free-form con-structs,it is expected to be useful for endothelial formation in vascular structures with branch or curve shapes,and in other tubular tissues such as the esophagus.
基金support from the National Key Projects for Research and Development of China(Grant Nos.2022YFA1204700,2021YFA1400400)National Natural Science Foundation of China(Grant No.12525403)+3 种基金Natural Science Foundation of Jiangsu Province(Grant Nos.BK20220066,BK20233001)Program for Innovative Talents and Entrepreneur in Jiangsu(Grant No.JSSCTD202101)support from the JSPS KAKENHI(Grant Numbers 21H05233 and 23H02052)World Premier International Research Center Initiative(WPI),MEXT,Japan.
文摘Coulomb drag refers to the phenomenon in which a current driven through one conducting layer induces a voltage nearby,electrically isolated layer sorely through interlayer Coulomb interactions between charge carriers.It has been extensively studied in various systems,including parallel nanowires,double quantum wells,and double-layer graphene.Here,we report the observation of Coulomb drag in a novel system consisting of two graphene layers separated laterally by a 30 nm gap within the material plane,exhibiting behavior distinct from that in vertical graphene heterostructures.Our experiments reveal pronounced negative drag resistances under an out-of-plane magnetic field at the quantum Hall edges,reaching a maximum when the carrier densities in both graphene layers are tuned to the charge neutrality point via gate voltages.Our work establish two separate and spatially closed quantum Hall edge modes as a new platform to explore electronic interaction physics between one dimensional systems.
文摘Races using kitefoil and windfoil surfboards have been in the Olympic Games for the first time in Paris 2024,signalling their relevance in sailing sports.However,the dynamics of these devices is yet not well understood,in particular the influence on the hydrodynamic forces and moments of the distance of the foil to the free surface.Considering this,the present paper documents an experimental investigation in which forces and torque produced,under uniform flow,by a full-scale state-of-the-art hydrofoil(suitable both for kitesurf and windsurf)were measured.A range of velocities,angles of attack,and submergences were tested,leading to Froude numbers based on submergence with maximum values around five,a typical range in actual sailing conditions.From these tests,formulae for the hydrodynamic coefficients have been proposed.They can be used for developing Velocity Prediction Programs(VPP)for this kind of craft,a necessary tool to plan racing configurations and to analyze their racing performance.With the aim of making the experimental data useful for benchmarking numerical models and for future research on related topics such as foil ventilation and transition to turbulence,the specimen’s 3D file is provided as supplementary material to this paper.
文摘Aerodynamic research on road cars was reviewed in this work under the thread of reducing drag,with the awareness that this may succeed in effectively decreasing the carbon footprint of transportation.First,a selection of studies was presented to focus on the most important aerodynamic features of the flow around realistic car body shapes.Then,the discussion was organized around three pillars related to passive flow control,active flow control and active aerodynamics.Both experimental and numerical investigations were included to provide a comprehensive overview.A clear distinction was made between simplified and realistic car models,as well as production vehicles(within the limits of restricted access information).Moreover,a short essay was dedicated to electric vehicles,for which aerodynamics matters,especially at highway speeds.Last,the impact of aerodynamic principles on the design of current and future vehicle fleet was assessed,honestly admitting that recent market trends must be reversed to turn decarbonization goals into reality and damp the effects of global warming.
基金supported by the National Natural Science Foundation of China(Grant Nos.12125204,12388101,12502257,12472227)the Project 111 of China(Grant No.B17037)。
文摘The effect of local polymer injection on a flat-plate turbulent boundary layer was investigated experimentally,with a particular focus on the distinct mechanisms of drag reduction in the low-drag reduction(LDR)and high-drag reduction(HDR)states.High-resolution measurements of the near-wall flow field were achieved using particle tracking velocimetry(PTV),while large-field measurements covering the entire boundary layer were obtained through particle image velocimetry(PIV).It is found that in the LDR state,the mean shear and turbulence intensity in the near-wall region are mildly suppressed.The influence of polymer solution is limited to the near-wall region and does not affect the self-sustaining cycle of wall-bounded turbulence.Conversely,in the HDR state,the polymer solution effectively disrupts the self-sustaining process of wall-bounded turbulence by suppressing the lifting of the low-speed streaks.Consequently,the turbulence production is attenuated.The buffer layer is extended,and the slope of the log-law region also becomes larger when polymer concentration or the Weissenberg number increases.
文摘Environmental pollution,energy consumption,and greenhouse gas emissions are critical global issues.To address these challenges,optimizing skimmer coatings is a major step in commercializing cleaning oil stains.This research presents a novel approach to creating and refining oil absorbent coatings,introducing a unique oil spill removal skimmer enhanced with a super hydrophobic polyaniline(PANI)nanofiber coating.The goal of this study was to improve oil absorption performance,increase the contact angle,lower drag,reduce energy consumption,achieve high desirability,and lower production costs.PANI treated with hydrochloric acid was a key focus as it resulted in higher porosity and smaller pore diameters,providing a larger surface area,which are crucial factors for boosting oil absorption and minimizing drag.To optimize optimal nanofiber morphology,PANI synthesized with methanesulfonic acid was first dedoped and then redoped with hydrochloric acid.After optimization,the most effective skimmer coating was achieved using a formulation consisting of 0.1%PANI,an ammonium persulfate/aniline ratio of 0.4,and an acid/aniline ratio of 9.689,along with redoped PANI nanofibers.The optimized skimmer exhibited a remarkable contact angle of 177.477°.The coating achieved drag reduction of 32%,oil absorption of 88.725%,a cost of$1.710,and a desirability rating of 78.5%.In this study,an optimized skimmer coat containing super hydrophobic coat-PANI nanofibers was fabricated.By enhancing contact angle and reducing drag,these coatings increased the skimmer performance by improving oil absorption and reducing fuel consumption.
基金supported by the National Natural Science Foundation of China(Grant No.12227802)。
文摘The dynamic behaviors of supercooled large water droplets(SLDs)in airflow involving deformation,breakup,and splash affect the local water collection coefficient,leading to an increase in the complexity of aircraft icing.A parametric study on the influence of deformed water droplets in shear flow is investigated experimentally and numerically.A horizontal refrigerated wind tunnel is used to create the background shear airflow.A high-speed camera records the evolution of cross-stream/streamwise diameters and the breakup process.The level set method is employed to capture the deformation of micrometer-sized supercooled water droplets in continuous airflow.The deformation modes are categorized into five regimes:stabilization,vibration,transition,bag breakup,and bag-stamen breakup.A dimensionless deformation factor L is defined to describe the droplet deformation,which increases with airflow speed,droplet volume,and temperature.Applying the scaling expression Oh~(4.39)We~(0.85),a normalized acceleration model of water droplets in shear airflow is established.Based on the experimental results,a drag coefficient model for disc-shaped droplets within the transient Reynolds number range of 420-10000 is obtained.As the initial Weber number exceeds 9.5 and the maximum deformation factor exceeds 3.5,the droplet enters the breakup regime.Furthermore,bag-stamen breakup occurs when the initial Weber number exceeds 17.5.
基金supported by the National Natural Science Foundation of China (Grant Nos.12474051 and 92165201)the Chinese Academy of Sciences Project for Young Scientists in Basic Research (Grant No.YSBR-046)+1 种基金the National Key Research and Development Program of China (Grant No.2023YFA1406300)the Anhui Provincial Natural Science Foundation (Grant Nos.2308085J11 and2308085QA14)。
文摘Recent advances in two-dimensional layered systems have greatly enriched electronic transport studies, particularly in inter-layer Coulomb drag research. Here, systematic transport measurements were conducted in graphene-based electronic double-layer structures, revealing giant yet reproducible drag fluctuations at cryogenic temperatures. These fluctuations' characteristics, including amplitude and peak/valley spacing, are mainly determined by the drag layer's carrier dynamics rather than the drive layer's, resulting in violation of the Onsager reciprocity relation. Notably, the drag fluctuations remain observable up to 35 K, far exceeding universal conductance fluctuations within individual layers. This suggests enhanced phase coherence in inter-layer drag compared to single-layer transport, as further confirmed by quantitative analysis of auto-correlation fields of fluctuations under magnetic fields. Our findings provide new insights into quantum interference effects and their interplay with Coulomb interactions in solids. The observations of significant drag fluctuations could potentially help address chaotic signals between nearby components in nanoscale devices.
基金the financial support from the Fundamental Research Funds for the Central Universities(JUSRP122003)the fellowship of China Postdoctoral Science Foundation(2022TQ0123).
文摘Inspired by the aquatic-adapted pit structures of the Cybister beetles that enable high-speed swimming,this study employs warp-knitted technology to fabricate drag-reduction swimwear textiles.Eight distinct fabric morphologies were produced,and a self-developed high-precision dynamic drag measurement device was used to systematically analyze the mechanisms underlying the drag-reduction performance of these biomimetic pit structures.The device incorporates a servomotor,ball screw linkage,and high-precision tension sensor,enabling real-time and accurate detection of fluid drag forces.It effectively overcomes the limitations of traditional indirect measurement methods,including dynamic response lag and insufficient accuracy.Experimental results demonstrate that the hydrophobic small-pit fabric(4^(#))achieves an 84% drag reduction at 400 mm/s,outperforming the control sample(warp-knitted fabric 7^(#)).This significant reduction is attributed to the Cassie state established on the hydrophobic surface,which substantially decreases viscous drag and the microvortices generated by the pit structures,which delay flow separation and effectively minimize pressure drag.Furthermore,small-pit fabrics demonstrate a drag reduction rate 26% to 50% higher than that of large-pit structures,highlighting the critical importance of matching the pit scale to the thickness of the near-wall viscous sublayer for optimal drag reduction.This study establishes a theoretical foundation for the biomimetic design of high-performance drag-reduction swimsuits.The developed drag-measuring device also provides a standardized experimental platform for hydrodynamic studies of flexible materials,supporting a shift from empirical design methodologies to theory-driven approaches in drag-reduction technology and exhibiting significant potential for future advancements.
基金funded by the“Hundred Outstanding Talents”Support Program of Jining University,a provincial-level key project in the field of natural sciences,grant number 2023ZYRC23Jining Key R&D Program(Soft Science)Project,No.2024JNZC010Shandong Province Key Research and Development Program(Technology-Based Small and Medium-sized Enterprises Innovation Capability Improvement)Project No.2025TSGCCZZB0679.
文摘The rapid advancement of technology and the increasing speed of vehicles have led to a substantial rise in energy consumption and growing concern over environmental pollution.Beyond the promotion of new energy vehicles,reducing aerodynamic drag remains a critical strategy for improving energy efficiency and lowering emissions.This study investigates the influence of key geometric parameters on the aerodynamic drag of vehicles.A parametric vehicle model was developed,and computational fluid dynamics(CFD)simulations were conducted to analyse variations in the drag coefficient(C_(d))and pressure distribution across different design configurations.The results reveal that the optimal aerodynamic performance—characterized by a minimized drag coefficient—is achieved with the following parameter settings:engine hood angle(α)of 15°,windshield angle(β)of 25°,rear window angle(γ)of 40°,rear upwards tail lift angle(θ)of 10°,ground clearance(d)of 100 mm,and side edge angle(s)of 5°.These findings offer valuable guidance for the aerodynamic optimization of vehicle body design and contribute to strategies aimed at energy conservation and emission reduction in the automotive sector.
基金supported by the Japan Society for the Promotion of Science(JSPS KAKENHI No.23H01373).
文摘The cutaneous ridges on dolphin skin have long been believed to effectively reduce friction drag, thereby contributing to overall drag reduction. However, since these skin ridges are oriented perpendicular to the swimming direction, they also generate additional pressure drag, raising questions about the impact of the shape-induced pressure forces on swimming. Inspired by the microvibrations observed on dolphin skin, we hypothesize that the microstructure on dolphin skin is not static but dynamically oscillates in the form of Longitudinal Micro-Ultrasonic Waves (LMUWs). To explore this, we carried out a series of Computational Fluid Dynamics (CFD) simulations based on Large Eddy Simulation (LES) model to investigate the impact of pressure drag on the total drag acting on an oscillating skin surface under realistic turbulent flow conditions. The results indicate that the dynamic skin oscillations induce a new dynamic Stokes boundary layer, which has the potential to convert pressure drag into a negative force, thereby reducing total drag under the influence of traveling LMUW excitations. Furthermore, a relative velocity ξ, defined as the difference between the wave speed c and the external flow speed U, is introduced to evaluate the drag-reduction effect dominated by pressure. The findings reveal that pressure drag remains negative when ξ > 0. As ξ increases, the thrust effect induced by negative pressure becomes increasingly significant, ultimately counteracting friction drag and eliminating total drag. This pressure-dominated drag reduction mechanism thus demonstrates a novel strategy for the drag reduction technology and the potential of unveiling the mysteries behind dolphin swimming.
基金the National Natural Science Foundation of China(No.52305236)supported by National Natural Science Foundation of China.
文摘Reducing the resistance of vehicles,ships,aircraft and other means of transport during movement can significantly improve the speed,save energy and reduce emissions.After billions of years of continuous evolution,organisms in nature have gradually developed the ability to move at high speed to achieve better survival.These evolved organisms provide a perfect template for the human development of drag reduction materials.Revealing the unique physiological structural characteristics of organisms and their relationship with resistance during movement can provide a feasible approach tosolving the problem of reducing friction resistance.Whether flying in the sky,running on the ground,swimming in the water,or even living in the soil,many creatures in various environments have the ability to reduce resistance.Driven by these inspirations,researchers have done a lot of work to explore and imitate these biological epidermis structures to achieve drag reduction.In this paper,the biomimetic drag reduction materials is introduced in detail in the order of drag reduction mechanism,structural characteristics of biological epidermis(including marine animals,flying animals,soil animals and plants),biomimetic preparation methods,performance testing methods and application fields.Finally,the potential of various biomimetic drag reduction materials in engineering application and the problems to be overcome are summarized and prospected.This paper can help readers comprehensively understand the research progress of biomimetic drag reduction materials,and provide reference for further designing the next generation of drag reduction materials.
