The phenomenon of global fragmented production and associated trade in intermediate products,including intangible assets,has changed how economists study globalization and how new public policies are shaped.Understand...The phenomenon of global fragmented production and associated trade in intermediate products,including intangible assets,has changed how economists study globalization and how new public policies are shaped.Understanding cross-border flows of disembodied knowledge,often associated with intellectual property(IP),is essential for analyzing how modern economies operate.Available data to document these international IP-related knowledge flowsdnamely cross-border payments for IPdare distorted by various factors.Tax planning by multinational enterprises has seriously distorted the measurement of cross-border IP flows,affecting national measurements of imports,exports,GDP,and productivity.The tax-induced mismeasurement could be more than 35% of global charges for use of intellectual property,and greater for individual countries,particularly high-taxrate countries.International initiatives to address the effects of tax base erosion,profit shifting,and other statistical initiatives on global value chains will improve future measurements of cross-border IP flows,improving the understanding of both the creation and uses of IP.展开更多
The Fourth Industrial Revolution has endowed the concept of state sovereignty with new era-specific connotations,leading to the emergence of the theory of data sovereignty.While countries refine their domestic legisla...The Fourth Industrial Revolution has endowed the concept of state sovereignty with new era-specific connotations,leading to the emergence of the theory of data sovereignty.While countries refine their domestic legislation to establish their data sovereignty,they are also actively engaging in the negotiation of cross-border data flow rules within international trade agreements to construct data sovereignty.During these negotiations,countries express differing regulatory claims,with some focusing on safeguarding sovereignty and protecting human rights,some prioritizing economic promotion and security assurance,and others targeting traditional and innovative digital trade barriers.These varied approaches reflect the tension between three pairs of values:collectivism and individualism,freedom and security,and tradition and innovation.Based on their distinct value pursuits,three representative models of data sovereignty construction have emerged globally.At the current juncture,when international rules for digital trade are still in their nascent stages,China should timely establish its data sovereignty rules,actively participate in global data sovereignty competition,and balance its sovereignty interests with other interests.Specifically,China should explore the scope of system-acceptable digital trade barriers through free trade zones;integrate domestic and international legal frameworks to ensure the alignment of China’s data governance legislation with its obligations under international trade agreements;and use the development of the“Digital Silk Road”as a starting point to prioritize the formation of digital trade rules with countries participating in the Belt and Road Initiative,promoting the Chinese solutions internationally.展开更多
The digital development rights in developing countries are based on establishing a new international economic order and ensuring equal participation in the digital globalization process to achieve people's well-ro...The digital development rights in developing countries are based on establishing a new international economic order and ensuring equal participation in the digital globalization process to achieve people's well-rounded development in the digital society.The relationship between cross-border data flows and the realization of digital development rights in developing countries is quite complex.Currently,developing countries seek to safeguard their existing digital interests through unilateral regulation to protect data sovereignty and multilateral regulation for cross-border data cooperation.However,developing countries still have to face internal conflicts between national digital development rights and individual and corporate digital development rights during the process of realizing digital development rights.They also encounter external contradictions such as developed countries interfering with developing countries'data sovereignty,developed countries squeezing the policy space of developing countries through dominant rules,and developing countries having conflicts between domestic and international rules.This article argues that balancing openness and security on digital trade platforms is the optimal solution for developing countries to realize their digital development rights.The establishment of WTO digital trade rules should inherently reflect the fundamental demands of developing countries in cross-border data flows.At the same time,given China's dual role as a digital powerhouse and a developing country,it should actively promote the realization of digital development rights in developing countries.展开更多
Cross-border e-commerce,as a new form of international trade,has shown great development potential in the context of the“Belt and Road”initiative.Based on the cross-border e-commerce export data from 2015 to 2024,th...Cross-border e-commerce,as a new form of international trade,has shown great development potential in the context of the“Belt and Road”initiative.Based on the cross-border e-commerce export data from 2015 to 2024,this paper analyzes the influencing factors of China's cross-border e-commerce exports to countries along the“Belt and Road”by constructing an econometric model.The study found that factors such as the perfection of digital infrastructure,the efficiency of logistics and transportation,the convenience of payment and settlement,and the penetration rate of consumers online shopping significantly affect the export scale of cross-border e-commerce.Institutional factors such as the development level of e-commerce platforms in countries along the route,market access thresholds,and tariff policies also play an important role.Based on the research results,suggestions are put forward to strengthen the construction of cross-border payment system,optimize the logistics distribution network,promote customs clearance facilitation,and deepen cooperation in the field of e-commerce,to provide references for promoting the development of China's crossborder e-commerce exports to countries along the“Belt and Road.”展开更多
This paper aims to numerically explore the characteristics of unsteady cavitating flow around a NACA0015 hydrofoil,with a focus on vorticity attributes.The simulation utilizes a homogeneous mixture model coupled with ...This paper aims to numerically explore the characteristics of unsteady cavitating flow around a NACA0015 hydrofoil,with a focus on vorticity attributes.The simulation utilizes a homogeneous mixture model coupled with a filter-based density correction turbulence model and a modified Zwart cavitation model.The study investigates the dynamic cavitation features of the thermal fluid around the hydrofoil at various incoming flow velocities.It systematically elucidates the evolution of cavitation and vortex dynamics corresponding to each velocity condition.The results indicate that with increasing incoming flow velocity,distinct cavitation processes take place in the flow field.展开更多
Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising techn...Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising technology to achieve high efficiency,because it has high machining flexibility and no machining tool wear.However,reports on the macro electrochemical jet machining of large size titanium alloy parts are very scarce,because it is difficult to achieve effective constraint of the flow field in macro electrochemical jet machining.In addition,titanium alloy is very sensitive to fluctuation of the flow field,and a turbulent flow field would lead to serious stray corrosion.This paper reports a series of investigations of the electrochemical jet machining of titanium alloy parts.Based on the flow analysis and experiments,the machining flow field was effectively constrained.TB6 titanium alloy part with a perimeter of one meter was machined.The machined surface was smooth with no obvious machining defects.The machining process was particularly stable with no obvious spark discharge.The research provides a reference for the application of electrochemical jet machining technology to achieve large allowance material removal in the machining of large titanium alloy parts.展开更多
Cross-border e-commerce has emerged as a new growth point in foreign trade.While the Dalian comprehensive pilot zone has made some progress,its development is constrained by issues such as the global economic slowdown...Cross-border e-commerce has emerged as a new growth point in foreign trade.While the Dalian comprehensive pilot zone has made some progress,its development is constrained by issues such as the global economic slowdown,the relatively small scale of cross-border e-commerce,a high concentration of export commodities,imperfect information mechanisms,and high overall costs.To address these challenges,this paper explores the importance of the construction of the Dalian comprehensive pilot zone for cross-border e-commerce to the transformation and upgrading of exports.Based on my research project,“Research on Path Optimization of Financial Support for the Development of Advanced Manufacturing Clusters in Dalian,”this paper analyzes the current challenges and limiting factors and proposes corresponding countermeasures and suggestions.展开更多
Based on the global asset portfolio model,this paper created a panel threshold model using EPFR fund data to empirically test the non-linear spillover effects of US economic policy uncertainties on cross-border capita...Based on the global asset portfolio model,this paper created a panel threshold model using EPFR fund data to empirically test the non-linear spillover effects of US economic policy uncertainties on cross-border capital flow for emerging economies.Our study led to the following findings:(1)When the level of global investor risk tolerance is high,rising US EPU will induce a capital inflow into emerging economies,as manifested in the“portfolio rebalancing effect.”When the level of global investor risk tolerance is below a critical threshold,this gives rise to risk aversion and emerging economies will experience net capital outflow,i.e.the“flight to quality effect”.(2)Equity fund investors have a lower risk tolerance threshold than bond fund investors.(3)According to our heterogeneity analysis,more attention should be paid to monitoring capital flow through actively managed funds,ETF funds,and retail investor funds.The economy should increase financial efficiency and economic resiliency to mitigate capital outflow pressures from the external environment.展开更多
The formation,evolution,and dynamics of flow structures in wall-bounded turbulence have long been central themes in fluid-mechanics research.Over the past three decades,Soliton-like Coherent Structures(SCSs)have emerg...The formation,evolution,and dynamics of flow structures in wall-bounded turbulence have long been central themes in fluid-mechanics research.Over the past three decades,Soliton-like Coherent Structures(SCSs)have emerged as a ubiquitous and unifying feature across a wide range of shear flows,including K-type,O-type,N-type,and bypass transitional boundary layers,as well as fully developed turbulent boundary layers,mixing layers,and pipe flows.This paper presents a systematic review of the fundamental properties of SCSs and highlights their fundamental role in multiple transition scenarios.The analysis further explores the connection between SCSs and low-speed streaks,offering insight into their coupled dynamics.The phenomenon of turbulent bursting is also examined within the context of SCS dynamics.Together,these studies underscore the potential of SCSs to serve as a coherent dynamical framework for understanding turbulence generation mechanisms in wall-bounded flows.Finally,the review extends to the manifestation of SCSs in other canonical flows,including mixing layers,stratified shear flows,and jets,confirming their universality and significance in fluid dynamics.These findings not only advance our understanding of turbulence generation but also offer a promising theoretical foundation for future research in transitional and turbulent flows.展开更多
This study investigates the air–water interaction dynamics in jet streams,with particular emphasis on the transition from the cavity to the far-field regions.A dual-tip conductivity phase-detection probe was employed...This study investigates the air–water interaction dynamics in jet streams,with particular emphasis on the transition from the cavity to the far-field regions.A dual-tip conductivity phase-detection probe was employed to analyze four distinct downstream water levels.Based on the development of the cross-sectional mean air concentration,the jet flow was divided into four distinct regions:the jet length region,impact region,splash region,and far-field region.The results demonstrate varying trends in the evolution of the mean air concentration and maximum bubble frequency.Downstream water levels exerted a significant influence on these parameters in the splash and far-field regions,whereas minimal variation was observed in the impact region.Additionally,notable differences were identified in the probability density function of water droplets between the cavity and downstream regions.Furthermore,downstream water depth was found to have a negligible effect on the proportion of small-sized droplets in both the impact and splash regions.展开更多
The variable salinity in stored reservoirs connected by a long channel attracts the attention of scientists worldwide,having applications in environmental and geophysical engineering.This study explores the impact of ...The variable salinity in stored reservoirs connected by a long channel attracts the attention of scientists worldwide,having applications in environmental and geophysical engineering.This study explores the impact of Navier slip conditions on exchange flows within a long channel connecting two large reservoirs of differing salinity.These horizontal density gradients drive the flow.We modify the recent one-dimensional theory,developed to avoid runaway stratification,to account for the presence of uniform slip walls.By adjusting the parameters of the horizontal density gradient based on the slip factor,we resolve analytically various flow regimes ranging from high diffusion to transitional high advection.These regimes are governed by physical parameters like channel aspect ratio,slip factor,Schmidt number,and gravitational Reynolds number.Our solutions align perfectly with ones in the no-slip limit.More importantly,under the conditions of no net flow across the channel and high Schmidt number(where stratification is concentrated near the channel’s mid-layer),we derive a closed-form solution for the slip parameter,aspect ratio,and gravitational Reynolds number that describes the interface’s behavior as a sharp interface separating two distinct zones.This interface,arising from hydrostatic wall gradients,ultimately detaches the low-and high-density regimes throughout the channel when the gravitational Reynolds number is inversely proportional to the aspect ratio for a fixed slip parameter.This phenomenon,observed previously in 2D numerical simulations with no-slip walls in the literature,is thus confirmed by our theoretical results.Our findings further demonstrate that wall slip leads to distinct and diverse flow regimes.展开更多
The increasing performance demands of modern aero engines necessitate the integrated design of compressor transition ducts with upstream components to reduce the axial length of the engine.However,this design approach...The increasing performance demands of modern aero engines necessitate the integrated design of compressor transition ducts with upstream components to reduce the axial length of the engine.However,this design approach narrows the spacing between the stator and the strut,making traditional research on transition ducts only with struts unsuitable.The numerical results and experimental oil flow visualization results were utilized to reconstruct the three-dimensional flow structures in the stator passages under various operating conditions.Additionally,numerical methods were employed to analyze the mechanisms of the strut's effect on the upstream stator in an aggressive transition duct.The results show that the strut potential field increases the load on the upstream stator,leading to severe blade surface separation and corner separation/stall,and redistributes the inflow angle of the upstream stators circumferentially,resulting in significant differences in the flow structures within the stator passages on both sides.The separation flows within the stator passages mainly manifest in five types:pressure surface separation vortex,suction surface concentrated shedding vortex,suction surface separation vortex,suction surface-corner stall separation vortex,and suction surface separation vortex pair.Under different operating conditions,the separation flows within the stator passages are always composed of a part of these five types or a transitional state between two of them.展开更多
Buoyancy-driven flows are prevalent in a wide range of geophysical and astrophysical systems. In this review, we focus on threepivotal effects that significantly influence the dynamics and transport properties of buoy...Buoyancy-driven flows are prevalent in a wide range of geophysical and astrophysical systems. In this review, we focus on threepivotal effects that significantly influence the dynamics and transport properties of buoyancy-driven flows and may have impli-cations for natural systems. These effects pertain to the role of boundary conditions, the impact of rotation, and the effect offinite size. Boundary conditions represent how the fluid flow interacts with different kinds of surfaces. Rotation, as the Earth’srotation in geophysical systems or the whirling of astrophysical systems, introduces Coriolis and centrifugal forces, leading tothe profound vortical structure and distinct transport property. Finite size, representing geometrical constraints, influences thebehavior of buoyancy-driven flows across varying geometrical settings. This review aims to provide a holistic understanding ofthe intricate interplay of these factors, offering insights into the complex natural phenomena from the perspectives of the threeeffects.展开更多
Bridge pier failures from granular flow impacts are common.Installing defense piles upstream is an effective mitigation strategy,yet their protective mechanisms and standardized design guidelines are unclear.This stud...Bridge pier failures from granular flow impacts are common.Installing defense piles upstream is an effective mitigation strategy,yet their protective mechanisms and standardized design guidelines are unclear.This study employed 3D discrete element method to analyze the influence of defense pile size and placement on its performance across 219 scenarios,providing a detailed examination of their protective mechanisms.Results show that optimizing these factors can reduce the maximum impact force on bridge piers by up to 94%.In terms of size,a critical height threshold is identified,beyond which increasing pile height does not enhance protection.This threshold depends on the movement height of granular particles at the slope base.Protection effectiveness varies with pile size:when H≤0.05 h(H is the height of defense piles,h is the height of bridge),protection marginally improves with increasing height and diameter;for 0.05 h<H<0.15 h,protection strongly correlates with both parameters;for H≥0.15 h,diameter becomes the dominant factor.In terms of placement,an optimal longitudinal distance exists between the defense pile and the bridge pier.The larger the diameter,the greater the optimal longitudinal distance.However,the transverse distance is inversely related to protection effectiveness.Mechanistic analysis shows that defense piles are more effective at redirecting particles to prevent direct collisions with the pier(contributing 100%impact energy reduction before the non-dimensional travel time t*=7.01 and 63%–100%afterward)than at reducing particle velocity.This study provides insights into the protective mechanisms of defense piles and informs strategies for optimizing bridge pier protection in granular flow-prone regions.展开更多
The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings.Natural boulders can be highly random and unpredictable.Consequently,boulder control...The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings.Natural boulders can be highly random and unpredictable.Consequently,boulder control during debris flows is crucial but difficult.Herein,an eco-friendly control system featuring anchoring natural boulders(NBs)with(negative Poisson's ratio)NPR anchor cables is proposed to form an NB-NPR baffle.A series of flume experiments are conducted to verify the effect of NB-NPR baffles on controlling debris flow impact.The deployment of NB-NPR baffles substantially influences the kinematic behavior of a debris flow,primarily in the form of changes in the depositional properties and impact intensities.The results show that the NB-NPR baffle matrix successfully controls boulder mobility and exhibits positive feedback on solid particle deposition.The NB-NPR baffle group exhibits a reduction in peak impact force ranging from 29%to 79%compared to that of the control group in the basic experiment.The NPR anchor cables play a significant role in the NB-NPR baffle by demonstrating particular characteristics,including consistent resistance,large deformation,and substantial energy absorption.The NB-NPR baffle innovatively utilizes the natural boulders in a debris flow gully by converting destructive boulders into constructive boulders.Overall,this research serves as a basis for future field experiments and applications.展开更多
International capital flows play a crucial role in the process of globalization,presenting both opportunities and challenges to the financial stability of emerging economies.This article sorts out the positive effects...International capital flows play a crucial role in the process of globalization,presenting both opportunities and challenges to the financial stability of emerging economies.This article sorts out the positive effects and potential risks of international capital flows on the financial stability of emerging economies.By combining case studies in recent years,it analyzes the complex relationship between cross-border capital flows and financial stability,and proposes policy paths for emerging economies to cope with the shock of capital flows,providing references for enhancing financial resilience and achieving sustainable development.展开更多
Ecosystem service flows(ESFs)can reveal the interrelationships and impacts between natural systems and human activities.We can improve the stability and sustainability of ecosystems,more effectively utilize natural re...Ecosystem service flows(ESFs)can reveal the interrelationships and impacts between natural systems and human activities.We can improve the stability and sustainability of ecosystems,more effectively utilize natural resources,protect the environment,and enhance the harmonious coexistence of humans and nature by comprehending ESFs.However,few studies have examined ESFs across scales and evaluated their sustainability;most have concentrated on regional scales.In order to quantify and analyze ESFs within the Jing River Basin(JRB)and between the JRB and the adjacent and distant regions from a water-food-energy perspective,this paper employs a meta-coupling framework.Additionally,it evaluates the sustainability of these flows using a techno-ecological synergy framework.The results show that the ESFs within the JRB was significant in 2020.Water production services were concentrated in the southern part of the JRB,while the distribution of food supply and carbon supply services was relatively even.Huan County emerged as the largest exporting county,providing 1.46×10^(8)kg of food to other counties and exporting 2.97×10^(6)kg of energy.The ESFs in the JRB primarily moved towards the neighboring and distant systems.Water production services flowed into the Guanzhong Plain Urban Agglomeration(GPUA),amounting to 5.8×10^(6)kg.Carbon supply services flowed out at 2.4×10^(5)kg,and food exports were the highest,reaching 5.0×10^(7)kg.The ecosystem service flows from the JRB to both the neighboring and distant systems enhanced food security and ecological resilience.The basin itself demonstrated good sustainability in food supply services,with an index value reaching 48.19.In crossscale calculations of food production sustainability with the adjacent GPUA,the index value increased from 48.19 to 52.99,indicating a significant improvement.These findings demonstrate that applying the meta-coupling framework provides an effective approach to quantify ESFs and assess their sustainability across scales.展开更多
文摘The phenomenon of global fragmented production and associated trade in intermediate products,including intangible assets,has changed how economists study globalization and how new public policies are shaped.Understanding cross-border flows of disembodied knowledge,often associated with intellectual property(IP),is essential for analyzing how modern economies operate.Available data to document these international IP-related knowledge flowsdnamely cross-border payments for IPdare distorted by various factors.Tax planning by multinational enterprises has seriously distorted the measurement of cross-border IP flows,affecting national measurements of imports,exports,GDP,and productivity.The tax-induced mismeasurement could be more than 35% of global charges for use of intellectual property,and greater for individual countries,particularly high-taxrate countries.International initiatives to address the effects of tax base erosion,profit shifting,and other statistical initiatives on global value chains will improve future measurements of cross-border IP flows,improving the understanding of both the creation and uses of IP.
基金This paper is a phased result of the“Research on the Issue of China’s Data Export System”(24SFB3035)a research project of the Ministry of Justice of China on the construction of the rule of law and the study of legal theories at the ministerial level in 2024.
文摘The Fourth Industrial Revolution has endowed the concept of state sovereignty with new era-specific connotations,leading to the emergence of the theory of data sovereignty.While countries refine their domestic legislation to establish their data sovereignty,they are also actively engaging in the negotiation of cross-border data flow rules within international trade agreements to construct data sovereignty.During these negotiations,countries express differing regulatory claims,with some focusing on safeguarding sovereignty and protecting human rights,some prioritizing economic promotion and security assurance,and others targeting traditional and innovative digital trade barriers.These varied approaches reflect the tension between three pairs of values:collectivism and individualism,freedom and security,and tradition and innovation.Based on their distinct value pursuits,three representative models of data sovereignty construction have emerged globally.At the current juncture,when international rules for digital trade are still in their nascent stages,China should timely establish its data sovereignty rules,actively participate in global data sovereignty competition,and balance its sovereignty interests with other interests.Specifically,China should explore the scope of system-acceptable digital trade barriers through free trade zones;integrate domestic and international legal frameworks to ensure the alignment of China’s data governance legislation with its obligations under international trade agreements;and use the development of the“Digital Silk Road”as a starting point to prioritize the formation of digital trade rules with countries participating in the Belt and Road Initiative,promoting the Chinese solutions internationally.
基金a preliminary result of the Chinese Government Scholarship High-level Graduate Program sponsored by China Scholarship Council(Program No.CSC202206310052)。
文摘The digital development rights in developing countries are based on establishing a new international economic order and ensuring equal participation in the digital globalization process to achieve people's well-rounded development in the digital society.The relationship between cross-border data flows and the realization of digital development rights in developing countries is quite complex.Currently,developing countries seek to safeguard their existing digital interests through unilateral regulation to protect data sovereignty and multilateral regulation for cross-border data cooperation.However,developing countries still have to face internal conflicts between national digital development rights and individual and corporate digital development rights during the process of realizing digital development rights.They also encounter external contradictions such as developed countries interfering with developing countries'data sovereignty,developed countries squeezing the policy space of developing countries through dominant rules,and developing countries having conflicts between domestic and international rules.This article argues that balancing openness and security on digital trade platforms is the optimal solution for developing countries to realize their digital development rights.The establishment of WTO digital trade rules should inherently reflect the fundamental demands of developing countries in cross-border data flows.At the same time,given China's dual role as a digital powerhouse and a developing country,it should actively promote the realization of digital development rights in developing countries.
文摘Cross-border e-commerce,as a new form of international trade,has shown great development potential in the context of the“Belt and Road”initiative.Based on the cross-border e-commerce export data from 2015 to 2024,this paper analyzes the influencing factors of China's cross-border e-commerce exports to countries along the“Belt and Road”by constructing an econometric model.The study found that factors such as the perfection of digital infrastructure,the efficiency of logistics and transportation,the convenience of payment and settlement,and the penetration rate of consumers online shopping significantly affect the export scale of cross-border e-commerce.Institutional factors such as the development level of e-commerce platforms in countries along the route,market access thresholds,and tariff policies also play an important role.Based on the research results,suggestions are put forward to strengthen the construction of cross-border payment system,optimize the logistics distribution network,promote customs clearance facilitation,and deepen cooperation in the field of e-commerce,to provide references for promoting the development of China's crossborder e-commerce exports to countries along the“Belt and Road.”
文摘This paper aims to numerically explore the characteristics of unsteady cavitating flow around a NACA0015 hydrofoil,with a focus on vorticity attributes.The simulation utilizes a homogeneous mixture model coupled with a filter-based density correction turbulence model and a modified Zwart cavitation model.The study investigates the dynamic cavitation features of the thermal fluid around the hydrofoil at various incoming flow velocities.It systematically elucidates the evolution of cavitation and vortex dynamics corresponding to each velocity condition.The results indicate that with increasing incoming flow velocity,distinct cavitation processes take place in the flow field.
基金the National Natural Science Foundation of China(No.52205468)China Postdoctoral Science Foundation(No.2022M710061 and No.2023T160277)Natural Science Foundation of Jiangsu Province(No.BK20210755)。
文摘Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising technology to achieve high efficiency,because it has high machining flexibility and no machining tool wear.However,reports on the macro electrochemical jet machining of large size titanium alloy parts are very scarce,because it is difficult to achieve effective constraint of the flow field in macro electrochemical jet machining.In addition,titanium alloy is very sensitive to fluctuation of the flow field,and a turbulent flow field would lead to serious stray corrosion.This paper reports a series of investigations of the electrochemical jet machining of titanium alloy parts.Based on the flow analysis and experiments,the machining flow field was effectively constrained.TB6 titanium alloy part with a perimeter of one meter was machined.The machined surface was smooth with no obvious machining defects.The machining process was particularly stable with no obvious spark discharge.The research provides a reference for the application of electrochemical jet machining technology to achieve large allowance material removal in the machining of large titanium alloy parts.
文摘Cross-border e-commerce has emerged as a new growth point in foreign trade.While the Dalian comprehensive pilot zone has made some progress,its development is constrained by issues such as the global economic slowdown,the relatively small scale of cross-border e-commerce,a high concentration of export commodities,imperfect information mechanisms,and high overall costs.To address these challenges,this paper explores the importance of the construction of the Dalian comprehensive pilot zone for cross-border e-commerce to the transformation and upgrading of exports.Based on my research project,“Research on Path Optimization of Financial Support for the Development of Advanced Manufacturing Clusters in Dalian,”this paper analyzes the current challenges and limiting factors and proposes corresponding countermeasures and suggestions.
基金sponsored by the Natural Science Foundation of China(NSFC)2018 Emergency Management Project“Exchange Rate Market Variation,Cross-Border Capital Flow and Financial Risk Prevention”(Grant No.71850005)the NSFC Youth Program“Dynamic Estimation of Foreign Exchange Market Pressure in the Process of Capital Account Opening and Evaluation of the Central Bank’s Intervention Policy Effects”(Grant No.71803204).
文摘Based on the global asset portfolio model,this paper created a panel threshold model using EPFR fund data to empirically test the non-linear spillover effects of US economic policy uncertainties on cross-border capital flow for emerging economies.Our study led to the following findings:(1)When the level of global investor risk tolerance is high,rising US EPU will induce a capital inflow into emerging economies,as manifested in the“portfolio rebalancing effect.”When the level of global investor risk tolerance is below a critical threshold,this gives rise to risk aversion and emerging economies will experience net capital outflow,i.e.the“flight to quality effect”.(2)Equity fund investors have a lower risk tolerance threshold than bond fund investors.(3)According to our heterogeneity analysis,more attention should be paid to monitoring capital flow through actively managed funds,ETF funds,and retail investor funds.The economy should increase financial efficiency and economic resiliency to mitigate capital outflow pressures from the external environment.
基金supported by the National Key Project(GJXM92579).
文摘The formation,evolution,and dynamics of flow structures in wall-bounded turbulence have long been central themes in fluid-mechanics research.Over the past three decades,Soliton-like Coherent Structures(SCSs)have emerged as a ubiquitous and unifying feature across a wide range of shear flows,including K-type,O-type,N-type,and bypass transitional boundary layers,as well as fully developed turbulent boundary layers,mixing layers,and pipe flows.This paper presents a systematic review of the fundamental properties of SCSs and highlights their fundamental role in multiple transition scenarios.The analysis further explores the connection between SCSs and low-speed streaks,offering insight into their coupled dynamics.The phenomenon of turbulent bursting is also examined within the context of SCS dynamics.Together,these studies underscore the potential of SCSs to serve as a coherent dynamical framework for understanding turbulence generation mechanisms in wall-bounded flows.Finally,the review extends to the manifestation of SCSs in other canonical flows,including mixing layers,stratified shear flows,and jets,confirming their universality and significance in fluid dynamics.These findings not only advance our understanding of turbulence generation but also offer a promising theoretical foundation for future research in transitional and turbulent flows.
基金supported by the National Natural Science Foundation of China(52479068)Open Fund Research from the State Key Laboratory of Hydraulics and Mountain River Engineering(SKHL2323).
文摘This study investigates the air–water interaction dynamics in jet streams,with particular emphasis on the transition from the cavity to the far-field regions.A dual-tip conductivity phase-detection probe was employed to analyze four distinct downstream water levels.Based on the development of the cross-sectional mean air concentration,the jet flow was divided into four distinct regions:the jet length region,impact region,splash region,and far-field region.The results demonstrate varying trends in the evolution of the mean air concentration and maximum bubble frequency.Downstream water levels exerted a significant influence on these parameters in the splash and far-field regions,whereas minimal variation was observed in the impact region.Additionally,notable differences were identified in the probability density function of water droplets between the cavity and downstream regions.Furthermore,downstream water depth was found to have a negligible effect on the proportion of small-sized droplets in both the impact and splash regions.
文摘The variable salinity in stored reservoirs connected by a long channel attracts the attention of scientists worldwide,having applications in environmental and geophysical engineering.This study explores the impact of Navier slip conditions on exchange flows within a long channel connecting two large reservoirs of differing salinity.These horizontal density gradients drive the flow.We modify the recent one-dimensional theory,developed to avoid runaway stratification,to account for the presence of uniform slip walls.By adjusting the parameters of the horizontal density gradient based on the slip factor,we resolve analytically various flow regimes ranging from high diffusion to transitional high advection.These regimes are governed by physical parameters like channel aspect ratio,slip factor,Schmidt number,and gravitational Reynolds number.Our solutions align perfectly with ones in the no-slip limit.More importantly,under the conditions of no net flow across the channel and high Schmidt number(where stratification is concentrated near the channel’s mid-layer),we derive a closed-form solution for the slip parameter,aspect ratio,and gravitational Reynolds number that describes the interface’s behavior as a sharp interface separating two distinct zones.This interface,arising from hydrostatic wall gradients,ultimately detaches the low-and high-density regimes throughout the channel when the gravitational Reynolds number is inversely proportional to the aspect ratio for a fixed slip parameter.This phenomenon,observed previously in 2D numerical simulations with no-slip walls in the literature,is thus confirmed by our theoretical results.Our findings further demonstrate that wall slip leads to distinct and diverse flow regimes.
基金supported by the National Natural Science Foundation of China(No.52276025)the Science Center for Gas Turbine Project of China(Nos.P2022-A-Ⅱ-001-001,P2022-A-Ⅱ-002-001 and P2022-B-Ⅱ-002-001)。
文摘The increasing performance demands of modern aero engines necessitate the integrated design of compressor transition ducts with upstream components to reduce the axial length of the engine.However,this design approach narrows the spacing between the stator and the strut,making traditional research on transition ducts only with struts unsuitable.The numerical results and experimental oil flow visualization results were utilized to reconstruct the three-dimensional flow structures in the stator passages under various operating conditions.Additionally,numerical methods were employed to analyze the mechanisms of the strut's effect on the upstream stator in an aggressive transition duct.The results show that the strut potential field increases the load on the upstream stator,leading to severe blade surface separation and corner separation/stall,and redistributes the inflow angle of the upstream stators circumferentially,resulting in significant differences in the flow structures within the stator passages on both sides.The separation flows within the stator passages mainly manifest in five types:pressure surface separation vortex,suction surface concentrated shedding vortex,suction surface separation vortex,suction surface-corner stall separation vortex,and suction surface separation vortex pair.Under different operating conditions,the separation flows within the stator passages are always composed of a part of these five types or a transitional state between two of them.
基金supponted by the National Natural Science Foundation of China (Grant Nos 12202173,12072144,12232010,12372219,and 12302282).
文摘Buoyancy-driven flows are prevalent in a wide range of geophysical and astrophysical systems. In this review, we focus on threepivotal effects that significantly influence the dynamics and transport properties of buoyancy-driven flows and may have impli-cations for natural systems. These effects pertain to the role of boundary conditions, the impact of rotation, and the effect offinite size. Boundary conditions represent how the fluid flow interacts with different kinds of surfaces. Rotation, as the Earth’srotation in geophysical systems or the whirling of astrophysical systems, introduces Coriolis and centrifugal forces, leading tothe profound vortical structure and distinct transport property. Finite size, representing geometrical constraints, influences thebehavior of buoyancy-driven flows across varying geometrical settings. This review aims to provide a holistic understanding ofthe intricate interplay of these factors, offering insights into the complex natural phenomena from the perspectives of the threeeffects.
基金supported by the National Natural Science Foundation of China(Grant numbers 41977233)。
文摘Bridge pier failures from granular flow impacts are common.Installing defense piles upstream is an effective mitigation strategy,yet their protective mechanisms and standardized design guidelines are unclear.This study employed 3D discrete element method to analyze the influence of defense pile size and placement on its performance across 219 scenarios,providing a detailed examination of their protective mechanisms.Results show that optimizing these factors can reduce the maximum impact force on bridge piers by up to 94%.In terms of size,a critical height threshold is identified,beyond which increasing pile height does not enhance protection.This threshold depends on the movement height of granular particles at the slope base.Protection effectiveness varies with pile size:when H≤0.05 h(H is the height of defense piles,h is the height of bridge),protection marginally improves with increasing height and diameter;for 0.05 h<H<0.15 h,protection strongly correlates with both parameters;for H≥0.15 h,diameter becomes the dominant factor.In terms of placement,an optimal longitudinal distance exists between the defense pile and the bridge pier.The larger the diameter,the greater the optimal longitudinal distance.However,the transverse distance is inversely related to protection effectiveness.Mechanistic analysis shows that defense piles are more effective at redirecting particles to prevent direct collisions with the pier(contributing 100%impact energy reduction before the non-dimensional travel time t*=7.01 and 63%–100%afterward)than at reducing particle velocity.This study provides insights into the protective mechanisms of defense piles and informs strategies for optimizing bridge pier protection in granular flow-prone regions.
基金financial support from the National Natural Science Foundation of China(Grant No.41941018).
文摘The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings.Natural boulders can be highly random and unpredictable.Consequently,boulder control during debris flows is crucial but difficult.Herein,an eco-friendly control system featuring anchoring natural boulders(NBs)with(negative Poisson's ratio)NPR anchor cables is proposed to form an NB-NPR baffle.A series of flume experiments are conducted to verify the effect of NB-NPR baffles on controlling debris flow impact.The deployment of NB-NPR baffles substantially influences the kinematic behavior of a debris flow,primarily in the form of changes in the depositional properties and impact intensities.The results show that the NB-NPR baffle matrix successfully controls boulder mobility and exhibits positive feedback on solid particle deposition.The NB-NPR baffle group exhibits a reduction in peak impact force ranging from 29%to 79%compared to that of the control group in the basic experiment.The NPR anchor cables play a significant role in the NB-NPR baffle by demonstrating particular characteristics,including consistent resistance,large deformation,and substantial energy absorption.The NB-NPR baffle innovatively utilizes the natural boulders in a debris flow gully by converting destructive boulders into constructive boulders.Overall,this research serves as a basis for future field experiments and applications.
文摘International capital flows play a crucial role in the process of globalization,presenting both opportunities and challenges to the financial stability of emerging economies.This article sorts out the positive effects and potential risks of international capital flows on the financial stability of emerging economies.By combining case studies in recent years,it analyzes the complex relationship between cross-border capital flows and financial stability,and proposes policy paths for emerging economies to cope with the shock of capital flows,providing references for enhancing financial resilience and achieving sustainable development.
基金supported by the National Natural Science Foundation of China[Grant NO.42361040]。
文摘Ecosystem service flows(ESFs)can reveal the interrelationships and impacts between natural systems and human activities.We can improve the stability and sustainability of ecosystems,more effectively utilize natural resources,protect the environment,and enhance the harmonious coexistence of humans and nature by comprehending ESFs.However,few studies have examined ESFs across scales and evaluated their sustainability;most have concentrated on regional scales.In order to quantify and analyze ESFs within the Jing River Basin(JRB)and between the JRB and the adjacent and distant regions from a water-food-energy perspective,this paper employs a meta-coupling framework.Additionally,it evaluates the sustainability of these flows using a techno-ecological synergy framework.The results show that the ESFs within the JRB was significant in 2020.Water production services were concentrated in the southern part of the JRB,while the distribution of food supply and carbon supply services was relatively even.Huan County emerged as the largest exporting county,providing 1.46×10^(8)kg of food to other counties and exporting 2.97×10^(6)kg of energy.The ESFs in the JRB primarily moved towards the neighboring and distant systems.Water production services flowed into the Guanzhong Plain Urban Agglomeration(GPUA),amounting to 5.8×10^(6)kg.Carbon supply services flowed out at 2.4×10^(5)kg,and food exports were the highest,reaching 5.0×10^(7)kg.The ecosystem service flows from the JRB to both the neighboring and distant systems enhanced food security and ecological resilience.The basin itself demonstrated good sustainability in food supply services,with an index value reaching 48.19.In crossscale calculations of food production sustainability with the adjacent GPUA,the index value increased from 48.19 to 52.99,indicating a significant improvement.These findings demonstrate that applying the meta-coupling framework provides an effective approach to quantify ESFs and assess their sustainability across scales.
