By building a composite index for measuring national digital economy development and sectoral digital intensities,this paper derives metrics of industry-level digital economy penetration under the framework of special...By building a composite index for measuring national digital economy development and sectoral digital intensities,this paper derives metrics of industry-level digital economy penetration under the framework of specialization within global value chains(GVCs),systematically analyzes the mechanisms through which digital economy development affects GVCs upstreamness,and examines the moderating effect of institutional quality.The study shows that different dimensions of digital economy development significantly boost GVCs upstreamness,a conclusion that holds even after accounting for endogeneity through dynamic panel models with instrumental variables based on past data.Further research shows that technological innovation capabilities and resource allocation efficiency have gradually become important channels for digital economy development to boost GVCs upstreamness.Adding indicators on institutional quality reveals that greater institutional quality not only directly promotes GVCs upstreamness but also reinforces the impact of digital economy development on higher GVCs positioning.展开更多
The distribution of flow discharge between the Tien and Hau Rivers in the Vietnamese Mekong Delta(VMD)plays an important role in Vietnam’s agricultural and aquaculture production activities.However,recent variations ...The distribution of flow discharge between the Tien and Hau Rivers in the Vietnamese Mekong Delta(VMD)plays an important role in Vietnam’s agricultural and aquaculture production activities.However,recent variations in water levels and flow patterns,driven by both human activities and climate change(CC),have posed significant challenges for water resource management.This study evaluates the impacts of unsustainable exploitation and CC on the hydrological regime of the Tien and Hau Rivers using non-parametric statistical methods.Long-term water level data(1978–2023)from Tan Chau,Chau Doc,and Vam Nao observation stations were analyzed using the Mann-Kendall test(MK),Sen’s Slope(SS)estimator,and Pettitt’s test to detect trends,quantify change magnitudes,and identify abrupt shifts.The results indicate a significant decline in flood-season water levels,with annual decrease rates ranging from 41.5 to 72.9 mm in September and November.Conversely,a slight increasing trend in water levels was observed in the dry season(DS)during the studied time.Additionally,findings reveal that the upstream Tien River exerts greater control over the hydrological regime in the Vam Nao River.These insights contribute to disaster risk assessment,sustainable water resource planning,and ecological risk evaluation.Furthermore,the results contribute to providing a foundation for applying hydrological and hydraulic models to forecast hydrodynamics,thereby supporting effective water management strategies and mitigating flood and dry risks in the VMD.展开更多
A pre-swirl system with a multi-chamber structure is crucial to the secondary air system of an aero engine.The airflow within the pre-swirl system(characterized by high-speed rotation and compressible flow)is complica...A pre-swirl system with a multi-chamber structure is crucial to the secondary air system of an aero engine.The airflow within the pre-swirl system(characterized by high-speed rotation and compressible flow)is complicated.During transient processes in aero engine operation,the pre-swirl system is subjected to upstream fluctuations,which is a less studied aspect.This paper delves into the unsteady flow characteristics within the pre-swirl system.We investigate the influence of different pressure-fluctuation boundary conditions,corresponding to step function,ramp function,and sine function,on the transient response characteristics of the pre-swirl system.The results indicate that the response characteristics are strongly affected by the upstream boundary conditions.An obvious overshoot phenomenon is observed in the actual temperature drop under the step and ramp function conditions.The peak time of the step function is 75%shorter compared to the ramp function.Furthermore,the flow parameters exhibit nonlinear growth during the transient process,emphasizing the need for consideration in future quasi-steady simulations.For the sine function condition,the pressure-fluctuation frequency minimally affects stable values of mass flow rate and actual temperature drop but exerts a substantial influence on the maximum deviation of actual temperature drop of the system.As the frequency increases from 100 Hz to 200 Hz,the maximum deviations for actual temperature drop change from around±13 K to±10 K.展开更多
Compared to discrete continental marginal basins,the mechanisms of hydrocarbon migration and enrichment in transform continental marginal basins are poorly understood.In this study,we conducted a comprehensive analysi...Compared to discrete continental marginal basins,the mechanisms of hydrocarbon migration and enrichment in transform continental marginal basins are poorly understood.In this study,we conducted a comprehensive analysis of the main source rocks,reservoirs,and vertical migration pathways within the Rovuma(RB)and Tanzania(TB)basins in East Africa utilizing drilling,logging,seismic,and geochemical data.The results indicate that the enhanced preservation conditions of the Lower Jurassic source rocks in the southwest could lead to the discovery of large natural gas fields in the southern TB and RB.The primary reservoir is a deep-water turbidite sandstone.Due to topographic differences,the expanse of the turbidite sandstones in the RB is significantly larger than those in Tanzania.The main vertical migration pathways are the western boundary fault zone of the Kerimbas Graben(WBFZ)and the Seagap fault zone(SFZ).In the RB,natural gas migrates vertically along the WBFZ and preferentially accumulates in the deep-water turbidite sandstones of the footwall under the control of the fluid potential.Conversely,in the southern TB,the deep natural gas first migrates upward along the SFZ,then moves along the shallow branch faults in the sandstones on both sides of the SFZ.展开更多
In this study, the three-dimensional non-premixed two-phase kerosene/air rotating detonation engines with different isolator configurations and throat area ratios are simulated by the Eulerian-Lagrangian method. The e...In this study, the three-dimensional non-premixed two-phase kerosene/air rotating detonation engines with different isolator configurations and throat area ratios are simulated by the Eulerian-Lagrangian method. The effects of the divergence, straight, and convergence isolators on the rotating detonation wave dynamics and the upstream oblique shock wave propagation mechanism are analyzed. The differences in the rotating detonation wave behaviors between ground and flight operations are clarified.The results indicate that the propagation regimes of the upstream oblique shock wave depend on the isolator configurations and operation conditions. With a divergence isolator, the airflow is accelerated throughout the isolator and divergence section, leading to a maximum Mach number(~1.8) before the normal shock. The total pressure loss reaches the largest, and the detonation pressure drops. The upstream oblique shock wave can be suppressed within the divergence section with the divergence isolator.However, for the straight and convergence isolators, the airflow in the isolator with a larger ψ_(1)(0.3 and0.4) can suffer from the disturbance of the upstream oblique shock wave. The critical incident angle is around 39° at ground operation conditions. The upstream oblique shock wave tends to be suppressed when the engine operates under flight operation conditions. The critical pressure ratio β_(cr0) is found to be able to help in distinguishing the propagation regimes of the upstream oblique shock wave. Slightly below or above the β_(cr0) can obtain different marginal propagation results. The high-speed airflow in the divergence section affects the fuel droplet penetration distance, which deteriorates the reactant mixing and the detonation area. Significant detonation velocity deficits are observed and the maximum velocity deficit reaches 26%. The results indicate the engine channel design should adopt different isolator configurations based on the purpose of total pressure loss or disturbance suppression. This study can provide useful guidance for the channel design of a more complete two-phase rotating detonation engine.展开更多
The Penobscot Field,located within the Scotian Basin offshore Nova Scotia,Canada,represents an underexplored hydrocarbon field with potential for future development.Previous studies have been confined to specific rese...The Penobscot Field,located within the Scotian Basin offshore Nova Scotia,Canada,represents an underexplored hydrocarbon field with potential for future development.Previous studies have been confined to specific reservoir intervals without integrating multiple stratigraphic levels,and a comprehensive static reservoir characterization and volumetric assessment of the Penobscot Field has yet to be undertaken,constraining its full development evaluation.This study presents a comprehensive characte rization of the field by integrating geological,geophysical,and petrophysical datasets,leading to static hydrocarbon reserve estimation.The workflow involves seismic interpretation,structural modeling,petrophysical evaluation,and static volumetric calculations.Seismic analysis revealed a structu rally complex setting dominated by normal and inverted faults,with reservoir intervals primarily within the Missisauga Formation,which is subdivided into upper,middle,and lower units.Petro p hysical evaluation from well logs and core data identified key reservoir properties,including porosity ranging from 12 % to 28 %,permeability spanning from 1 to 1000 mD,and variable water saturations.Stochastic modeling of facies and petro p hysical attributes provided insights into lateral and ve rtical hete rogeneity.The Penobscot Field's original oil-in-place ranges from 41.6×10~6 m3 to 109.7×10~6 m3,with the Middle Missisauga sands presenting the highest reservoir potential.Fault seal analysis indicated predominantly sealing behavior in the shallow sections and semi-permeable conditions at greater depths,suggesting potential lateral migration pathways.The results underscore the field's hydrocarbon potential while emphasizing the significance of structural complexity,facies distribution,and petrophysical variability in reservoir quality,as well as its potential for future development or utilization of similar sand reservoirs for CO_(2) storage utilization.This work provides the first fully integrated static reservoir model of the Penobscot Field,offering critical insights for delineating the hydrocarbon reservoirs potential and future production strategies in the Scotian Basin.展开更多
The solar wind's interaction with the Moon has traditionally been understood through the Moon's absorption of solar wind particles and the formation of a plasma cavity on its nightside,known as the lunar wake....The solar wind's interaction with the Moon has traditionally been understood through the Moon's absorption of solar wind particles and the formation of a plasma cavity on its nightside,known as the lunar wake.This study reveals unexpected,large-scale perturbations in the solar wind upstream of the Moon,using 11 years of data from the OMNI and ARTEMIS(Acceleration,Reconnection,Turbulence and Electrodynamics of Moon's Interaction with the Sun)missions(2012-2023).We find systematic moonward deviations of~tens of km/s in a direction perpendicular to the solar wind(moonward),at altitudes of up to 1000 km,particularly when the interplanetary magnetic field(IMF)lines are oblique to the solar wind(30°<θ<60°)and connected to the lunar dayside.The longer the duration of the interaction,the greater the moonward deviation.These perturbations can be explained by neither solar wind pickup of the reflected ions,nor lunar wake dynamics.Instead,they appear to correlate with magnetic connectivity between the ARTEMIS probes and the lunar surface,suggesting a more complex solar wind interaction than previously thought.展开更多
This paper examines the impact of upstream merger and acquisition(M&A)activities driven by supply chain integration motives on firm energy performance.By developing a microlevel theoretical framework,we examine th...This paper examines the impact of upstream merger and acquisition(M&A)activities driven by supply chain integration motives on firm energy performance.By developing a microlevel theoretical framework,we examine the intricate relationship between firms’upstream M&A strategies geared toward supply chain integration and their energy efficiency.We examine the impact of upstream M&A activities on energy performance using data from Chinese listed companies from 2007 to 2021.Our findings reveal that upstream M&A initiatives can enhance firms’energy efficiency,although there are discernible variations in the effects observed for M&A activities targeted downstream or within the same industry.By examining mechanisms,we elucidate the pivotal roles of input substitution effects and productivity enhancements through which upstream M&As boost energy performance.Furthermore,our analysis underscores the catalyzing impact of M&A activities in fostering collaborative innovation in green technologies among firms and suppliers,thus improving productivity and energy efficiency.We provide new microlevel evidence of the relationship between M&A transactions and corporate energy efficiency from upstream and downstream perspectives.展开更多
Since 2011,America has maintained its position as the world’s largest natural gas producer.Since 2017,America has consistently experienced a surplus in natural gas supply,becoming a net exporter of natural gas.Americ...Since 2011,America has maintained its position as the world’s largest natural gas producer.Since 2017,America has consistently experienced a surplus in natural gas supply,becoming a net exporter of natural gas.America’s“natural gas independence”has reshaped the global natural gas market,creating a new pattern of“supply shifting westward and consumption shifting eastward”.展开更多
The analysis of ancient genomics provides opportunities to explore human population history across both temporal and geographic dimensions(Haak et al.,2015;Wang et al.,2021,2024)to enhance the accessibility and utilit...The analysis of ancient genomics provides opportunities to explore human population history across both temporal and geographic dimensions(Haak et al.,2015;Wang et al.,2021,2024)to enhance the accessibility and utility of these ancient genomic datasets,a range of databases and advanced statistical models have been developed,including the Allen Ancient DNA Resource(AADR)(Mallick et al.,2024)and AdmixTools(Patterson et al.,2012).While upstream processes such as sequencing and raw data processing have been streamlined by resources like the AADR,the downstream analysis of these datasets-encompassing population genetics inference and spatiotemporal interpretation-remains a significant challenge.The AADR provides a unified collection of published ancient DNA(aDNA)data,yet its file-based format and reliance on command-line tools,such as those in Admix-Tools(Patterson et al.,2012),require advanced computational expertise for effective exploration and analysis.These requirements can present significant challenges forresearchers lackingadvanced computational expertise,limiting the accessibility and broader application of these valuable genomic resources.展开更多
Wei River is an important river which affects the industrial and agricultural production,people's life in Guanzhong district of Shaanxi and the east of Gansu.To study the variation characteristics of main climate ...Wei River is an important river which affects the industrial and agricultural production,people's life in Guanzhong district of Shaanxi and the east of Gansu.To study the variation characteristics of main climate factors in recent 39 years in the upstream of Wei River,we analyzed the variation characteristics of climate factors by using the data in 11 meteorological stations in the upstream basin of Wei River during 1971-2009.The results showed that the precipitation presented the decline trend in the basin,and the temperature rose in 0.3 ℃/10 a trend.The temperature increase trend was 0.4 ℃/10 a in winter,spring and wasn't obvious in summer,autumn.The potential evapotranspiration presented the yearly increase trend in recent years.The precipitation decreased,and the temperature rose.Moreover,the potential evapotranspiration strengthened.It wasn't favorable for the healthy run of ecological system in the upstream,downstream basins and aggravated the shortage degree of water resources.展开更多
An upwind scheme based on the unstructured mesh is developed to solve ideal 2-D magnetohydrodynamics （MHD） equations. The inviscid fluxes are approximated by using the modified advection upstream splitting method （...An upwind scheme based on the unstructured mesh is developed to solve ideal 2-D magnetohydrodynamics （MHD） equations. The inviscid fluxes are approximated by using the modified advection upstream splitting method （AUSM） scheme, and a 5-stage explicit Runge-Kutta scheme is adopted in the time integration. To avoid the influence of the magnetic field divergence created during the simulation, the hyperbolic divergence cleaning method is introduced. The shock-capturing properties of the method are verified by solving the MHD shock-tube problem. Then the 2-D nozzle flow with the magnetic field is numerically simulated on the unstructured mesh. Computational results demonstrate the effects of the magnetic field and agree well with those from references.展开更多
In modern gas turbines, rim seal located between the stator-disc and rotor-disc is used to prevent hot-gas ingestion into the inner stage-gap of high pressure turbine. However, the purge flow supplied to the cavity th...In modern gas turbines, rim seal located between the stator-disc and rotor-disc is used to prevent hot-gas ingestion into the inner stage-gap of high pressure turbine. However, the purge flow supplied to the cavity through the rim seal interacts with the main flow, producing additional aerodynamic loss due to the mixing process which plays a significant role in the formation, development and evolution of downstream secondary flow. In this paper, a set of cascade representative of low aspect ratio turbine is selected to numerically investigate the influence of upstream cavity purge flow on the hub secondary flow structure and aerodynamic loss. Cascade with/without upstream cavity and four different purge mass flow rates are all taken into account in this simulation. Then, a deep insight into the loss mechanism of interaction between purge flow and main flow is gained. The results show that the presence of cavity and purge flow has a significant impact on the main flow which not only changes the vortex structure in both the passage and upstream cavity, but also alters the cascade exit flow angle distribution along the spanwise. Moreover, aerodynamic loss in the cascade rises with the increase of purge flow rate while the sealing effect is also enhanced. Therefore, the effect of upstream cavity purge flow must be considered in the process of turbine aerodynamic design. What is more, it is necessary to minimize the purge flow rate in order to reduce aerodynamic loss on the premise of satisfying cooling requirements.展开更多
We use the Wind Farm Parameterization(WFP) scheme coupled with the Weather Research and Forecasting model under multiple resolution regimes to simulate turbulent wake dynamics generated by a real onshore wind farm and...We use the Wind Farm Parameterization(WFP) scheme coupled with the Weather Research and Forecasting model under multiple resolution regimes to simulate turbulent wake dynamics generated by a real onshore wind farm and their influence at the local meteorological scale. The model outputs are compared with earlier modeling and observation studies. It is found that higher vertical and horizontal resolutions have great impacts on the simulated wake flow dynamics. The corresponding wind speed deficit and turbulent kinetic energy results match well with previous studies. In addition, the effect of horizontal resolution on near-surface meteorology is significantly higher than that of vertical resolution. The wake flow field extends from the start of the wind farm to downstream within 10 km, where the wind speed deficit may exceed 4%. For a height of 150 m or at a distance of about 25 km downstream, the wind speed deficit is around 2%. This indicates that, at a distance of more than 25 km downstream, the impact of the wind turbines can be ignored. Analysis of near-surface meteorology indicates a night and early morning warming near the surface, and increase in near-surface water vapor mixing ratio with decreasing surface sensible and latent heat fluxes. During daytime, a slight cooling near the surface and decrease in the near-surface water vapor mixing ratio with increasing surface sensible and latent heat fluxes is noticed over the wind farm area.展开更多
This paper explores the methodology for compiling the torrent hazard and risk zonation map by means of GIS technique for the Red River Basin in Yunnan province of China, where is prone to torrent. Based on a 1：250,00...This paper explores the methodology for compiling the torrent hazard and risk zonation map by means of GIS technique for the Red River Basin in Yunnan province of China, where is prone to torrent. Based on a 1：250,000 scale digital map, six factors including slope angle, rainstorm days, buffer of river channels, maximum runoff discharge of standard area, debris flow distribution density and flood disaster history were analyzed and superimposed to create the torrent risk evaluation map. Population density, farmland percentage, house property, and GDP as indexes accounting for torrent hazards were analyzed in terms of vulnerability mapping. Torrent risk zonation by means of GIS was overlaid on the two data layers of hazard and vulnerability. Then each grid unit with a resolution of 500 m- 500 m was divided into four categories of the risk： extremely high, high, moderate and low. Finally the same level risk was combined into a confirmed zone, which represents torrent risk of the study area. The risk evaluation result in the upper Red River Basin shows that the extremely high risk area of 13,150 km^2 takes up 17.9% of the total inundated area, the high risk area of 33,783 km^2 is 45.9%, the moderate risk area of 18,563 km^2 is 25.2% and the low risk area of 8115 km^2 is 11.0%.展开更多
We present in this paper some new evidence for the change during the Quaternary in kinematics of faults cutting the eastern margin of the Tibetan Plateau. It shows that significant shortening deformation occurred duri...We present in this paper some new evidence for the change during the Quaternary in kinematics of faults cutting the eastern margin of the Tibetan Plateau. It shows that significant shortening deformation occurred during the Early Pleistocene, evidenced by eastward thrusting of Mesozoic carbonates on the Pliocene lacustrine deposits along the Minjiang upstream fault zone and by development of the transpressional ridges of basement rocks along the Anninghe river valley. The Middle Pleistocene seems to be a relaxant stage with local development of the intra-mountain basins particularly prominent along the Minjiang Upstream and along the southern segment of the Anninghe River Valley. This relaxation may have been duo to a local collapse of the thickened crust attained during the late Neogene to early Pleistocene across this marginal zone. Fault kinematics has been changed since the late Pleistocene, and was predominated by reverse sinistral strike-slip along the Minshan Uplift, reverse dextral strike-slip on the Longmenshan fault zone and pure sinistral strike-slip on the Anninghe fault. This change in fault kinematics during the Quaternary allows a better understanding of the mechanism by which the marginal ranges of the plateau has been built through episodic activities.展开更多
Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for...Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for high tailings dam was developed according to the results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailing dam 113.5 m high. The law of generation, diffusion and dissipation of seismic pore water pressure during and after earthquake was investigated, and the results of tailings dam’s acceleration, seismic dynamic stress and pore water pressure were obtained. The results show that the seismic stability and liquefaction resistance of high tailings dam are strengthened remarkably, and the scope and depth of liquefaction area at the top of dam are reduced greatly. The interior stress is compressive stress, the stress level of every element is less than 1.0 and the safety coefficient of every element is greater than 1.0. The safety coefficient against liquefaction of every element of tailing dam is greater than 1.5 according to the effective stress analysis of seismic response by finite element method. The calculated results prove that liquefaction is the main reason of seismic failure of high tailing dams, and the effect of seismic inertia forces on high tailing dams’ stability during earthquake is secondary reason.展开更多
The regenerative capacity of peripheral nerves is limited after nerve injury.A number of growth factors modulate many cellular behaviors,such as proliferation and migration,and may contribute to nerve repair and regen...The regenerative capacity of peripheral nerves is limited after nerve injury.A number of growth factors modulate many cellular behaviors,such as proliferation and migration,and may contribute to nerve repair and regeneration.Our previous study observed the dynamic changes of genes in L4–6 dorsal root ganglion after rat sciatic nerve crush using transcriptome sequencing.Our current study focused on upstream growth factors and found that a total of 19 upstream growth factors were dysregulated in dorsal root ganglions at 3,9 hours,1,4,or 7 days after nerve crush,compared with the 0 hour control.Thirty-six rat models of sciatic nerve crush injury were prepared as described previously.Then,they were divided into six groups to measure the expression changes of representative genes at 0,3,9 hours,1,4 or 7 days post crush.Our current study measured the expression levels of representative upstream growth factors,including nerve growth factor,brain-derived neurotrophic factor,fibroblast growth factor 2 and amphiregulin genes,and explored critical signaling pathways and biological process through bioinformatic analysis.Our data revealed that many of these dysregulated upstream growth factors,including nerve growth factor,brain-derived neurotrophic factor,fibroblast growth factor 2 and amphiregulin,participated in tissue remodeling and axon growth-related biological processes Therefore,the experiment described the expression pattern of upstream growth factors in the dorsal root ganglia after peripheral nerve injury.Bioinformatic analysis revealed growth factors that may promote repair and regeneration of damaged peripheral nerves.All animal surgery procedures were performed in accordance with Institutional Animal Care Guidelines of Nantong University and ethically approved by the Administration Committee of Experimental Animals,China(approval No.20170302-017)on March 2,2017.展开更多
基金This study is supported by the National Social Science Foundation(NSSF)Project“Impact of Services Liberalization in High-quality Development Stage on Chinese Industry Upgrading(No.18AJY012).”
文摘By building a composite index for measuring national digital economy development and sectoral digital intensities,this paper derives metrics of industry-level digital economy penetration under the framework of specialization within global value chains(GVCs),systematically analyzes the mechanisms through which digital economy development affects GVCs upstreamness,and examines the moderating effect of institutional quality.The study shows that different dimensions of digital economy development significantly boost GVCs upstreamness,a conclusion that holds even after accounting for endogeneity through dynamic panel models with instrumental variables based on past data.Further research shows that technological innovation capabilities and resource allocation efficiency have gradually become important channels for digital economy development to boost GVCs upstreamness.Adding indicators on institutional quality reveals that greater institutional quality not only directly promotes GVCs upstreamness but also reinforces the impact of digital economy development on higher GVCs positioning.
文摘The distribution of flow discharge between the Tien and Hau Rivers in the Vietnamese Mekong Delta(VMD)plays an important role in Vietnam’s agricultural and aquaculture production activities.However,recent variations in water levels and flow patterns,driven by both human activities and climate change(CC),have posed significant challenges for water resource management.This study evaluates the impacts of unsustainable exploitation and CC on the hydrological regime of the Tien and Hau Rivers using non-parametric statistical methods.Long-term water level data(1978–2023)from Tan Chau,Chau Doc,and Vam Nao observation stations were analyzed using the Mann-Kendall test(MK),Sen’s Slope(SS)estimator,and Pettitt’s test to detect trends,quantify change magnitudes,and identify abrupt shifts.The results indicate a significant decline in flood-season water levels,with annual decrease rates ranging from 41.5 to 72.9 mm in September and November.Conversely,a slight increasing trend in water levels was observed in the dry season(DS)during the studied time.Additionally,findings reveal that the upstream Tien River exerts greater control over the hydrological regime in the Vam Nao River.These insights contribute to disaster risk assessment,sustainable water resource planning,and ecological risk evaluation.Furthermore,the results contribute to providing a foundation for applying hydrological and hydraulic models to forecast hydrodynamics,thereby supporting effective water management strategies and mitigating flood and dry risks in the VMD.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDC0160000)the National Natural Science Foundation of China(No.52122603)+4 种基金the Excellence Research Group Program(No.52488101)the Shandong Provincial Natural Science Foundation of China(No.ZR2024JQ011)the Project of National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine(No.2023-JJ-Y04)the National Science and Technology Major Project of China(No.J2019-III-0003-0046)the Taishan Scholars Program of China.
文摘A pre-swirl system with a multi-chamber structure is crucial to the secondary air system of an aero engine.The airflow within the pre-swirl system(characterized by high-speed rotation and compressible flow)is complicated.During transient processes in aero engine operation,the pre-swirl system is subjected to upstream fluctuations,which is a less studied aspect.This paper delves into the unsteady flow characteristics within the pre-swirl system.We investigate the influence of different pressure-fluctuation boundary conditions,corresponding to step function,ramp function,and sine function,on the transient response characteristics of the pre-swirl system.The results indicate that the response characteristics are strongly affected by the upstream boundary conditions.An obvious overshoot phenomenon is observed in the actual temperature drop under the step and ramp function conditions.The peak time of the step function is 75%shorter compared to the ramp function.Furthermore,the flow parameters exhibit nonlinear growth during the transient process,emphasizing the need for consideration in future quasi-steady simulations.For the sine function condition,the pressure-fluctuation frequency minimally affects stable values of mass flow rate and actual temperature drop but exerts a substantial influence on the maximum deviation of actual temperature drop of the system.As the frequency increases from 100 Hz to 200 Hz,the maximum deviations for actual temperature drop change from around±13 K to±10 K.
基金financially supported by the National Natural Science Foundation of China(Grant No.42002150)the Open Foundation of Cooperative Innovation Center of Unconventional Oil and Gas,Yangtze University(Ministry of Education&Hubei Province,Grant No.UOG2024-12)+1 种基金the Open Foundation Project of the Key Laboratory of Polar Geology and Marine Mineral Resources(China University of Geosciences,Beijing,China),Ministry of Education(Grant No.PGMR-2023-201)the National Key Research Program of China(Grant No.2017ZX05032-002)。
文摘Compared to discrete continental marginal basins,the mechanisms of hydrocarbon migration and enrichment in transform continental marginal basins are poorly understood.In this study,we conducted a comprehensive analysis of the main source rocks,reservoirs,and vertical migration pathways within the Rovuma(RB)and Tanzania(TB)basins in East Africa utilizing drilling,logging,seismic,and geochemical data.The results indicate that the enhanced preservation conditions of the Lower Jurassic source rocks in the southwest could lead to the discovery of large natural gas fields in the southern TB and RB.The primary reservoir is a deep-water turbidite sandstone.Due to topographic differences,the expanse of the turbidite sandstones in the RB is significantly larger than those in Tanzania.The main vertical migration pathways are the western boundary fault zone of the Kerimbas Graben(WBFZ)and the Seagap fault zone(SFZ).In the RB,natural gas migrates vertically along the WBFZ and preferentially accumulates in the deep-water turbidite sandstones of the footwall under the control of the fluid potential.Conversely,in the southern TB,the deep natural gas first migrates upward along the SFZ,then moves along the shallow branch faults in the sandstones on both sides of the SFZ.
基金supported by the National Natural Science Foundation of China (Grant No. 12202204)the Natural Science Foundation of Jiangsu Province (Grant No. BK20220953)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Science and Technology Association's Young Talent Nurturing Program of Jiangsu Province (Grant No. JSTJ-2024-004)
文摘In this study, the three-dimensional non-premixed two-phase kerosene/air rotating detonation engines with different isolator configurations and throat area ratios are simulated by the Eulerian-Lagrangian method. The effects of the divergence, straight, and convergence isolators on the rotating detonation wave dynamics and the upstream oblique shock wave propagation mechanism are analyzed. The differences in the rotating detonation wave behaviors between ground and flight operations are clarified.The results indicate that the propagation regimes of the upstream oblique shock wave depend on the isolator configurations and operation conditions. With a divergence isolator, the airflow is accelerated throughout the isolator and divergence section, leading to a maximum Mach number(~1.8) before the normal shock. The total pressure loss reaches the largest, and the detonation pressure drops. The upstream oblique shock wave can be suppressed within the divergence section with the divergence isolator.However, for the straight and convergence isolators, the airflow in the isolator with a larger ψ_(1)(0.3 and0.4) can suffer from the disturbance of the upstream oblique shock wave. The critical incident angle is around 39° at ground operation conditions. The upstream oblique shock wave tends to be suppressed when the engine operates under flight operation conditions. The critical pressure ratio β_(cr0) is found to be able to help in distinguishing the propagation regimes of the upstream oblique shock wave. Slightly below or above the β_(cr0) can obtain different marginal propagation results. The high-speed airflow in the divergence section affects the fuel droplet penetration distance, which deteriorates the reactant mixing and the detonation area. Significant detonation velocity deficits are observed and the maximum velocity deficit reaches 26%. The results indicate the engine channel design should adopt different isolator configurations based on the purpose of total pressure loss or disturbance suppression. This study can provide useful guidance for the channel design of a more complete two-phase rotating detonation engine.
文摘The Penobscot Field,located within the Scotian Basin offshore Nova Scotia,Canada,represents an underexplored hydrocarbon field with potential for future development.Previous studies have been confined to specific reservoir intervals without integrating multiple stratigraphic levels,and a comprehensive static reservoir characterization and volumetric assessment of the Penobscot Field has yet to be undertaken,constraining its full development evaluation.This study presents a comprehensive characte rization of the field by integrating geological,geophysical,and petrophysical datasets,leading to static hydrocarbon reserve estimation.The workflow involves seismic interpretation,structural modeling,petrophysical evaluation,and static volumetric calculations.Seismic analysis revealed a structu rally complex setting dominated by normal and inverted faults,with reservoir intervals primarily within the Missisauga Formation,which is subdivided into upper,middle,and lower units.Petro p hysical evaluation from well logs and core data identified key reservoir properties,including porosity ranging from 12 % to 28 %,permeability spanning from 1 to 1000 mD,and variable water saturations.Stochastic modeling of facies and petro p hysical attributes provided insights into lateral and ve rtical hete rogeneity.The Penobscot Field's original oil-in-place ranges from 41.6×10~6 m3 to 109.7×10~6 m3,with the Middle Missisauga sands presenting the highest reservoir potential.Fault seal analysis indicated predominantly sealing behavior in the shallow sections and semi-permeable conditions at greater depths,suggesting potential lateral migration pathways.The results underscore the field's hydrocarbon potential while emphasizing the significance of structural complexity,facies distribution,and petrophysical variability in reservoir quality,as well as its potential for future development or utilization of similar sand reservoirs for CO_(2) storage utilization.This work provides the first fully integrated static reservoir model of the Penobscot Field,offering critical insights for delineating the hydrocarbon reservoirs potential and future production strategies in the Scotian Basin.
基金supported by the National Natural Science Foundation of China(Grant No.42474227,42241106,42388101)financial support through the German Ministry for Economy and Technology and the German Center for Aviation and Space(DLR)under contract 50 OC 0302
文摘The solar wind's interaction with the Moon has traditionally been understood through the Moon's absorption of solar wind particles and the formation of a plasma cavity on its nightside,known as the lunar wake.This study reveals unexpected,large-scale perturbations in the solar wind upstream of the Moon,using 11 years of data from the OMNI and ARTEMIS(Acceleration,Reconnection,Turbulence and Electrodynamics of Moon's Interaction with the Sun)missions(2012-2023).We find systematic moonward deviations of~tens of km/s in a direction perpendicular to the solar wind(moonward),at altitudes of up to 1000 km,particularly when the interplanetary magnetic field(IMF)lines are oblique to the solar wind(30°<θ<60°)and connected to the lunar dayside.The longer the duration of the interaction,the greater the moonward deviation.These perturbations can be explained by neither solar wind pickup of the reflected ions,nor lunar wake dynamics.Instead,they appear to correlate with magnetic connectivity between the ARTEMIS probes and the lunar surface,suggesting a more complex solar wind interaction than previously thought.
基金supported by the following:the Fundamental Research Funds for the Central Universities of China[Grant No.JBK2406055]the 2024 Annual General Project of Humanities and Social Sciences Research by the Ministry of Education[Grant No.24XJA790005]the Cultivation Program of High-level Scholarly Representative Achievements for Graduate Students of Southwestern University of Finance and Economics[Grant No.JGS2024055].
文摘This paper examines the impact of upstream merger and acquisition(M&A)activities driven by supply chain integration motives on firm energy performance.By developing a microlevel theoretical framework,we examine the intricate relationship between firms’upstream M&A strategies geared toward supply chain integration and their energy efficiency.We examine the impact of upstream M&A activities on energy performance using data from Chinese listed companies from 2007 to 2021.Our findings reveal that upstream M&A initiatives can enhance firms’energy efficiency,although there are discernible variations in the effects observed for M&A activities targeted downstream or within the same industry.By examining mechanisms,we elucidate the pivotal roles of input substitution effects and productivity enhancements through which upstream M&As boost energy performance.Furthermore,our analysis underscores the catalyzing impact of M&A activities in fostering collaborative innovation in green technologies among firms and suppliers,thus improving productivity and energy efficiency.We provide new microlevel evidence of the relationship between M&A transactions and corporate energy efficiency from upstream and downstream perspectives.
文摘Since 2011,America has maintained its position as the world’s largest natural gas producer.Since 2017,America has consistently experienced a surplus in natural gas supply,becoming a net exporter of natural gas.America’s“natural gas independence”has reshaped the global natural gas market,creating a new pattern of“supply shifting westward and consumption shifting eastward”.
基金by the National Key Research and Development Program of China(2023YFC3303701-02 and 2024YFC3306701)the National Natural Science Foundation of China(T2425014 and 32270667)+3 种基金the Natural Science Foundation of Fujian Province of China(2023J06013)the Major Project of the National Social Science Foundation of China granted to Chuan-Chao Wang(21&ZD285)Open Research Fund of State Key Laboratory of Genetic Engineering at Fudan University(SKLGE-2310)Open Research Fund of Forensic Genetics Key Laboratory of the Ministry of Public Security(2023FGKFKT07).
文摘The analysis of ancient genomics provides opportunities to explore human population history across both temporal and geographic dimensions(Haak et al.,2015;Wang et al.,2021,2024)to enhance the accessibility and utility of these ancient genomic datasets,a range of databases and advanced statistical models have been developed,including the Allen Ancient DNA Resource(AADR)(Mallick et al.,2024)and AdmixTools(Patterson et al.,2012).While upstream processes such as sequencing and raw data processing have been streamlined by resources like the AADR,the downstream analysis of these datasets-encompassing population genetics inference and spatiotemporal interpretation-remains a significant challenge.The AADR provides a unified collection of published ancient DNA(aDNA)data,yet its file-based format and reliance on command-line tools,such as those in Admix-Tools(Patterson et al.,2012),require advanced computational expertise for effective exploration and analysis.These requirements can present significant challenges forresearchers lackingadvanced computational expertise,limiting the accessibility and broader application of these valuable genomic resources.
基金Supported by "Ten People Plan" of Gansu Meteorological BureauPublic Welfare Industry Special Item of National Science Technology Department (GYHY200806021)
文摘Wei River is an important river which affects the industrial and agricultural production,people's life in Guanzhong district of Shaanxi and the east of Gansu.To study the variation characteristics of main climate factors in recent 39 years in the upstream of Wei River,we analyzed the variation characteristics of climate factors by using the data in 11 meteorological stations in the upstream basin of Wei River during 1971-2009.The results showed that the precipitation presented the decline trend in the basin,and the temperature rose in 0.3 ℃/10 a trend.The temperature increase trend was 0.4 ℃/10 a in winter,spring and wasn't obvious in summer,autumn.The potential evapotranspiration presented the yearly increase trend in recent years.The precipitation decreased,and the temperature rose.Moreover,the potential evapotranspiration strengthened.It wasn't favorable for the healthy run of ecological system in the upstream,downstream basins and aggravated the shortage degree of water resources.
文摘An upwind scheme based on the unstructured mesh is developed to solve ideal 2-D magnetohydrodynamics （MHD） equations. The inviscid fluxes are approximated by using the modified advection upstream splitting method （AUSM） scheme, and a 5-stage explicit Runge-Kutta scheme is adopted in the time integration. To avoid the influence of the magnetic field divergence created during the simulation, the hyperbolic divergence cleaning method is introduced. The shock-capturing properties of the method are verified by solving the MHD shock-tube problem. Then the 2-D nozzle flow with the magnetic field is numerically simulated on the unstructured mesh. Computational results demonstrate the effects of the magnetic field and agree well with those from references.
基金Key Laboratory Foundation (9140C4103091003C) for funding this work
文摘In modern gas turbines, rim seal located between the stator-disc and rotor-disc is used to prevent hot-gas ingestion into the inner stage-gap of high pressure turbine. However, the purge flow supplied to the cavity through the rim seal interacts with the main flow, producing additional aerodynamic loss due to the mixing process which plays a significant role in the formation, development and evolution of downstream secondary flow. In this paper, a set of cascade representative of low aspect ratio turbine is selected to numerically investigate the influence of upstream cavity purge flow on the hub secondary flow structure and aerodynamic loss. Cascade with/without upstream cavity and four different purge mass flow rates are all taken into account in this simulation. Then, a deep insight into the loss mechanism of interaction between purge flow and main flow is gained. The results show that the presence of cavity and purge flow has a significant impact on the main flow which not only changes the vortex structure in both the passage and upstream cavity, but also alters the cascade exit flow angle distribution along the spanwise. Moreover, aerodynamic loss in the cascade rises with the increase of purge flow rate while the sealing effect is also enhanced. Therefore, the effect of upstream cavity purge flow must be considered in the process of turbine aerodynamic design. What is more, it is necessary to minimize the purge flow rate in order to reduce aerodynamic loss on the premise of satisfying cooling requirements.
基金the National Key Research and Development Program of China (Grant No.2017YFA0604501)the National Natural Science Foundation of China (Grant No.41475013) for the funding support
文摘We use the Wind Farm Parameterization(WFP) scheme coupled with the Weather Research and Forecasting model under multiple resolution regimes to simulate turbulent wake dynamics generated by a real onshore wind farm and their influence at the local meteorological scale. The model outputs are compared with earlier modeling and observation studies. It is found that higher vertical and horizontal resolutions have great impacts on the simulated wake flow dynamics. The corresponding wind speed deficit and turbulent kinetic energy results match well with previous studies. In addition, the effect of horizontal resolution on near-surface meteorology is significantly higher than that of vertical resolution. The wake flow field extends from the start of the wind farm to downstream within 10 km, where the wind speed deficit may exceed 4%. For a height of 150 m or at a distance of about 25 km downstream, the wind speed deficit is around 2%. This indicates that, at a distance of more than 25 km downstream, the impact of the wind turbines can be ignored. Analysis of near-surface meteorology indicates a night and early morning warming near the surface, and increase in near-surface water vapor mixing ratio with decreasing surface sensible and latent heat fluxes. During daytime, a slight cooling near the surface and decrease in the near-surface water vapor mixing ratio with increasing surface sensible and latent heat fluxes is noticed over the wind farm area.
基金National Natural Science Foundation of China, No.40371018
文摘This paper explores the methodology for compiling the torrent hazard and risk zonation map by means of GIS technique for the Red River Basin in Yunnan province of China, where is prone to torrent. Based on a 1：250,000 scale digital map, six factors including slope angle, rainstorm days, buffer of river channels, maximum runoff discharge of standard area, debris flow distribution density and flood disaster history were analyzed and superimposed to create the torrent risk evaluation map. Population density, farmland percentage, house property, and GDP as indexes accounting for torrent hazards were analyzed in terms of vulnerability mapping. Torrent risk zonation by means of GIS was overlaid on the two data layers of hazard and vulnerability. Then each grid unit with a resolution of 500 m- 500 m was divided into four categories of the risk： extremely high, high, moderate and low. Finally the same level risk was combined into a confirmed zone, which represents torrent risk of the study area. The risk evaluation result in the upper Red River Basin shows that the extremely high risk area of 13,150 km^2 takes up 17.9% of the total inundated area, the high risk area of 33,783 km^2 is 45.9%, the moderate risk area of 18,563 km^2 is 25.2% and the low risk area of 8115 km^2 is 11.0%.
基金supported jointly by the China Geological Survey project(grant number:1212011120167,12120114002201)China National Natural Science Foundation(grant number 41472178)
文摘We present in this paper some new evidence for the change during the Quaternary in kinematics of faults cutting the eastern margin of the Tibetan Plateau. It shows that significant shortening deformation occurred during the Early Pleistocene, evidenced by eastward thrusting of Mesozoic carbonates on the Pliocene lacustrine deposits along the Minjiang upstream fault zone and by development of the transpressional ridges of basement rocks along the Anninghe river valley. The Middle Pleistocene seems to be a relaxant stage with local development of the intra-mountain basins particularly prominent along the Minjiang Upstream and along the southern segment of the Anninghe River Valley. This relaxation may have been duo to a local collapse of the thickened crust attained during the late Neogene to early Pleistocene across this marginal zone. Fault kinematics has been changed since the late Pleistocene, and was predominated by reverse sinistral strike-slip along the Minshan Uplift, reverse dextral strike-slip on the Longmenshan fault zone and pure sinistral strike-slip on the Anninghe fault. This change in fault kinematics during the Quaternary allows a better understanding of the mechanism by which the marginal ranges of the plateau has been built through episodic activities.
基金Projects(03JJY3078, 04JJ40032) supported by the Natural Science Foundation of Hunan Province, China project(03A006) supported by Scientific Research Fund of Hunan Provincial Education Department, China
文摘Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for high tailings dam was developed according to the results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailing dam 113.5 m high. The law of generation, diffusion and dissipation of seismic pore water pressure during and after earthquake was investigated, and the results of tailings dam’s acceleration, seismic dynamic stress and pore water pressure were obtained. The results show that the seismic stability and liquefaction resistance of high tailings dam are strengthened remarkably, and the scope and depth of liquefaction area at the top of dam are reduced greatly. The interior stress is compressive stress, the stress level of every element is less than 1.0 and the safety coefficient of every element is greater than 1.0. The safety coefficient against liquefaction of every element of tailing dam is greater than 1.5 according to the effective stress analysis of seismic response by finite element method. The calculated results prove that liquefaction is the main reason of seismic failure of high tailing dams, and the effect of seismic inertia forces on high tailing dams’ stability during earthquake is secondary reason.
基金supported by the Natural Science Foundation of Jiangsu Higher Education Institutions of China(Major Program),No.16KJA310005(to SYL)the Natural Science Foundation of Nantong City of China,No.JC2018058(to TMQ)the Priority Academic Program Development of Jiangsu Higher Education Institutions of China
文摘The regenerative capacity of peripheral nerves is limited after nerve injury.A number of growth factors modulate many cellular behaviors,such as proliferation and migration,and may contribute to nerve repair and regeneration.Our previous study observed the dynamic changes of genes in L4–6 dorsal root ganglion after rat sciatic nerve crush using transcriptome sequencing.Our current study focused on upstream growth factors and found that a total of 19 upstream growth factors were dysregulated in dorsal root ganglions at 3,9 hours,1,4,or 7 days after nerve crush,compared with the 0 hour control.Thirty-six rat models of sciatic nerve crush injury were prepared as described previously.Then,they were divided into six groups to measure the expression changes of representative genes at 0,3,9 hours,1,4 or 7 days post crush.Our current study measured the expression levels of representative upstream growth factors,including nerve growth factor,brain-derived neurotrophic factor,fibroblast growth factor 2 and amphiregulin genes,and explored critical signaling pathways and biological process through bioinformatic analysis.Our data revealed that many of these dysregulated upstream growth factors,including nerve growth factor,brain-derived neurotrophic factor,fibroblast growth factor 2 and amphiregulin,participated in tissue remodeling and axon growth-related biological processes Therefore,the experiment described the expression pattern of upstream growth factors in the dorsal root ganglia after peripheral nerve injury.Bioinformatic analysis revealed growth factors that may promote repair and regeneration of damaged peripheral nerves.All animal surgery procedures were performed in accordance with Institutional Animal Care Guidelines of Nantong University and ethically approved by the Administration Committee of Experimental Animals,China(approval No.20170302-017)on March 2,2017.
