Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On ...Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On the other hand,the entry of ice crystal particles into the combustion chamber can cause a decrease in temperature or even flameout,leading to engine surge or shutdown.Therefore,it is necessary to conduct multiphase flow tests on ice crystals for aircraft components such as aircraft engines.Conducting ice crystal multiphase flow tests on aircraft is an effective research method,but it requires the construction of an ice crystal multiphase flow test platform that meets relevant technical requirements.The paper focuses on the relevant experimental requirements and combines wind tunnel test structures to conduct multiphase flow numerical simulations on various forms of jet pipelines,obtaining particle motion distribution results.After comparison,the optimal form of jet structure is obtained,providing the best selection scheme for the design of relevant wind tunnel structures.展开更多
In sediment transport on a mobile erodible bed,near-bed particles tend to preferentially locate under specific flow regions and form an uneven bedform.These moving and mobile particles can significantly modulate turbu...In sediment transport on a mobile erodible bed,near-bed particles tend to preferentially locate under specific flow regions and form an uneven bedform.These moving and mobile particles can significantly modulate turbulence at various scales,from inertial large-scale motions to small viscous motions.This study analyzes the particle-resolved direct numerical simulation data of particle-laden two-phase flow with multilayers of particles in turbulent flows over static and mobile beds.The double-average method is adopted for energy transfer analysis.The result shows that the alternative streaky bedform in the spanwise directions correlates with the streak structures in the near-wall turbulence in the mobile bed case.The energy redistribution and exchange,as well as the dissipation,are analyzed in detail,and an energy transfer diagram is given in the last to summarize the energy transfer processes.In both the static and mobile bed cases,flow energy is introduced into the system via the work performed by volume forces acting on the mean flow.The viscous dissipations in the double mean and form-induced fields are more pronounced in the static bed case,and the work done by the fluid-particle interfacial stress in the double mean and turbulent fields is more pronounced in the mobile bed case.The prominent energy contribution in the form-induced field is the production by the form-induced stress on the mean strain in the mobile bed case.In addition,sediment transport involving a limited number of mobile particles is insufficient to capture the energy transfer processes that occur over the troughs and may intertwine the energy transfer processes over the mobile particles and the fixed particle bed.展开更多
The deposition layer on the discharge channel wall of a Hall thruster after long-term operation occasionally detaches from the wall and interferes with the plasma inside the channel,resulting in current pulse and thre...The deposition layer on the discharge channel wall of a Hall thruster after long-term operation occasionally detaches from the wall and interferes with the plasma inside the channel,resulting in current pulse and threatening the power supply.To understand the generation mechanism of the current pulse,the interaction between the peeling material and the channel plasma was studied by the particle-in-cell and Monte Carlo collision(PIC/MCC)method.The plasma evolution and distribution in the Hall thruster channel when peeling material existed were simulated.Simulation results show that the peeling material changes the electron transportation and ionization,and the effects are related to the position of the peeling material.When the peeling material invades the zone where the ionization rate is originally the highest without peeling material,the ionization process is almost terminated.The ionization suppression by the peeling material will cause the propellant gas to refill the channel exit.As the peeling material moves away,gas discharge is induced near the channel exit,resulting in anode current pulse.展开更多
In recent years,rapid urbanization has had a profound impact on landscape stability.As a typical example of China's rapid urbanization,Hangzhou has also experienced significant landscape changes,which have profoun...In recent years,rapid urbanization has had a profound impact on landscape stability.As a typical example of China's rapid urbanization,Hangzhou has also experienced significant landscape changes,which have profoundly affected its ecological stability.Taking Hangzhou as an example,this study integrates land use change data from 1980 to 2020,combines dynamic simulation and ecological modeling techniques,and carries out a comprehensive analysis of historical trends and future predictions,to provide valuable insights into the complex interactions between urban expansion and landscape stability.The results indicate that:1)between 1980 and2020,Hangzhou experienced a significant increase in construction land at the expense of arable land,leading to a gradual decline in landscape stability,though the downward trend has slowed in recent years.2)The spatial distribution of landscape stability shows clear aggregation patterns,with lower stability concentrated in economically active flatlands and higher stability in the mountainous western regions.3)By 2040,further urban expansion is predicted to occur alongside increased landscape integration,reflecting the positive effects of ecological protection strategies.This study highlights the universal challenges of balancing economic growth with ecological stability in rapidly urbanizing regions.The combination of advanced simulation models and spatiotemporal analysis demonstrates a replicable framework for assessing urban expansion's ecological impacts.These findings underscore the importance of tailoring urban planning and ecological policies to address regional disparities,providing valuable insights for sustainable urban development and landscape management globally.展开更多
This study focuses on the thermal management of 4680-type cylindrical lithium-ion battery packs utilizing NCM811 chemistry.It establishes coupled multi-physics models for both immersion and serpentine cold plate cooli...This study focuses on the thermal management of 4680-type cylindrical lithium-ion battery packs utilizing NCM811 chemistry.It establishes coupled multi-physics models for both immersion and serpentine cold plate cooling systems.Through a combination of numerical simulation and experimental validation,the technical advantages and mechanisms of immersion cooling are systematically explored.Simulation results indicate that under a 3C fast-charging condition(inlet temperature 20℃,flow rate 36 L/min),the immersion cooling structure 3demonstrates a triple enhancement in thermal performance compared to the cold plate structure 1:a 13.06%reduction in peak temperature,a 31.67%decrease in overall maximum temperature difference,and a 47.62%decrease in single-cell temperature deviation,while also reducing flow resistance by 33.61%.Furthermore,based on the immersion cooling model,a small battery module comprising seven cylindrical cells was designed for thermal runaway testing via nail penetration.The results show that the peak temperature of the triggered cell was limited to 437.6℃,with a controllable temperature rise gradient of only 3.35℃/s and a rapid cooling rate of 0.6℃/s.The maximum temperature rise of adjacent cells was just 64.8℃,effectively inhibiting thermal propagation.Post-test disassembly revealed that the non-triggered cells retained>99.2%of their original voltage and>99%structural integrity,confirming the module’s ability to achieve“localized failure with global stability.”展开更多
[Objective]Precipitation events caused by Super Typhoon Doksuri in Fujian Province were simulated and evaluated based on the WRF model to provide a reference for typhoon precipitation simulation and forecasting in sou...[Objective]Precipitation events caused by Super Typhoon Doksuri in Fujian Province were simulated and evaluated based on the WRF model to provide a reference for typhoon precipitation simulation and forecasting in southeast coastal areas of China.[Methods]The next-generation mesoscale numerical weather prediction model WRF V4.3(The Weather Research and Forecasting Model)was used to simulate the precipitation caused by Typhoon Doksuri in Fujian Province in 2023.Observations from 86 meteorological stations with hourly rainfall records were used to evaluate the model’s performance.Six evaluation indices were used,including the correlation coefficient(R),root mean square error(RMSE),mean absolute error(MAE),equitable threat score(ETS),probability of detection(POD),and false alarm ratio(FAR).[Results](1)The temporal and spatial evolution of precipitation during Typhoon Doksuri was effectively captured by the WRF model.Precipitation intensity increased gradually from July 27 to 29,2023,with the heaviest rainfall concentrated in the northern and eastern coastal areas of Fujian Province.(2)Significant differences in model performance were observed in terms of R,RMSE,and MAE.The largest errors occurred in Putian City,while smaller errors were found in southwestern Fujian Province.The evaluation result of all six indices showed that the WRF model performed best in simulating daily precipitation compared to hourly,three-hourly,six-hourly,and twelve-hourly precipitation.(3)The R95p index indicated that the WRF model successfully captured the overall spatial distribution of extreme precipitation.However,extreme precipitation intensity was overestimated in certain coastal areas.(4)Despite accurately identifying the coastal regions of Fujian as being most affected,the WRF model failed to accurately simulate the spatial distribution and intensity of precipitation.The simulated precipitation centers showed discrepancies when compared with the observed centers.[Conclusion]Although the WRF model underestimated hourly precipitation,it successfully captured the temporal evolution and spatial distribution of rainfall caused by Typhoon Doksuri in Fujian Province.It reproduced the heavy rainfall centers in central Fujian Province,with daily precipitation peaks reaching up to 350 mm.This highlighted the severity of extreme rainfall caused by Typhoon Doksuri.展开更多
Tearing modes may play an important role in the density limit disruption.The Magnetohydrodynamic(MHD)code CLT with impurity modules is used to study the tearing mode excited and driven by impurity radiation.The impuri...Tearing modes may play an important role in the density limit disruption.The Magnetohydrodynamic(MHD)code CLT with impurity modules is used to study the tearing mode excited and driven by impurity radiation.The impurity radiation can lead to plasma contraction and local enhancement of the current density.When the locally enhanced region of the current density approaches to the resonance surface,the tearing mode can be excited,even if the tearing mode is stable in the initial equilibrium.Through a scan of the initial atomic number(Z)and impurity concentrations,it is found that impurities with different Z values exhibit similar behaviors in the radiation-driven tearing mode.The impurity radiation can drive tearing mode growth through temperature cooling near the resonance surface,and there exists a linear relationship between the temperature perturbation caused by impurity radiation and the linear growth rate of the tearing mode.Additionally,the impurity can promote the growth of magnetic islands through the radiation cooling inside the magnetic island,and there exists a correlation between the initial parameters of impurity and the width of the saturated magnetic island.展开更多
Stimuli-responsive polymers capable of rapidly altering their chain conformation in response to external stimuli exhibit broad applica-tion prospects.Experiments have shown that pressure plays a pivotal role in regula...Stimuli-responsive polymers capable of rapidly altering their chain conformation in response to external stimuli exhibit broad applica-tion prospects.Experiments have shown that pressure plays a pivotal role in regulating the microscopic chain conformation of polymers in mixed solvents,and one notable finding is that increasing the pressure can lead to the vanishing of the co-nonsolvency effect.However,the mecha-nisms underlying this phenomenon remain unclear.In this study,we systematically investigated the influence of pressure on the co-nonsolvency effect of single-chain and multi-chain homopolymers in binary mixed good-solvent systems using molecular dynamics simulations.Our results show that the co-nonsolvency-induced chain conformation transition and aggregation behavior significantly depend on pressure in allsingle-chain and multi-chain systems.In single-chain systems,at low pressures,the polymer chain maintains a collapsed state over a wide range of co-solvent fractions(x-range)owing to the co-nonsolvency effect.As the pressure increases,the x-range of the collapsed state gradually narrows,ac-companied by a progressive expansion of the chain.In multichain systems,polymer chains assemble into approximately spherical aggregates over a broad x-range at low pressures owing to the co-nonsolvency effect.Increasing the pressure reduces the x-range for forming aggregates and leads to the formation of loose aggregates or even to a state of dispersed chains at some x-range.These findings indicate that increasing the pressure can weaken or even offset the co-nonsolvency effect in some x-range,which is in good agreement with the experimental observations.Quantitative analysis of the radial density distributions and radial distribution functions reveals that,with increasing pressure,(1)the densities of both polymers and co-solvent molecules within aggregates decrease,while that of the solvent molecule increases;and(2)the effective interac-tions between the polymer and the co-solvent weaken,whereas those between the polymer and solvent strengthen.This enhances the incorpo-ration of solvent molecules within the chains,thereby weakening or even suppressing the chain aggregation.Our study not only elucidates the regulatory mechanism of pressure on the microscopic chain conformations and aggregation behaviors of polymers,but also may provide theo-retical guidance for designing smart polymericmaterials based on mixed solvents.展开更多
The emerging two-dimensional(2D)membranes offer a promising way to improve the water desalination performance of traditional membranes.MXene/graphene oxide(GO) composite membrane are known for their high separation pe...The emerging two-dimensional(2D)membranes offer a promising way to improve the water desalination performance of traditional membranes.MXene/graphene oxide(GO) composite membrane are known for their high separation performance and structural stability.In this study,molecular simulations are performed to investigate the desalination performance of the 2D MXene/GO membrane.The results reveal that the surface of the MXene nanosheet could induce the formation of ordered water structures,thereby accelerating the water transport in the 2D membrane.The higher rejection rate would be found in MXene/GO membrane with a larger GO oxidation degree owing to the sterichindrance effect induced by the functional groups on the GO surface.Overall,the MXene/GO(20) membrane with the interlayer spacing of 0.9 nm shows the highest water permeability(37.22×10^(-7)L·m^(-1)·h^(-1)·bar^(-1),1 bar=0.1 MPa)and a salt rejection of 100%.The results could provide theoretical insights for developing 2D membranes for water desalination.展开更多
This paper presents a numerical simulation of DC glow discharge at 2 Torr(1 Torr=1.33322×10~2 Pa)with a microhollow anode,using a two-dimensional(2D)PIC/MCC code to explore the impact of the hollow anode structur...This paper presents a numerical simulation of DC glow discharge at 2 Torr(1 Torr=1.33322×10~2 Pa)with a microhollow anode,using a two-dimensional(2D)PIC/MCC code to explore the impact of the hollow anode structure on discharge characteristics.Simulation results show that the plasma density in the anode channel decreases exponentially along the x-direction towards the outlet while the electric potential decreases linearly.The electron temperature,derived from the relationship between density and electric potential,shows a good agreement with the calculated temperature.The potential peak at the inlet,along with the grounded anode,forms a transverse potential well that draws electrons toward the center of the channel.The x-direction electric field,generated by the potential difference between the inlet and outlet of the anode,directs electrons toward the inlet of the anode.Low-energy electrons are confined within the potential well,while very few high-energy electrons outlet the channel.The hollow anode structure serves as a collimator for electrons,leading to an increment of moderate-velocity electron flux in the anode channel.Shortening the anode leads to a slower rate of density decrease,resulting in a higher density at the outlet.展开更多
Hypersonic magnetohydrodynamic(MHD)control effectively enhances the aerothermal environment of aerospace vehicles,demonstrating considerable potential in plasma flow regulation and aerodynamic optimiza-tion.As aerospa...Hypersonic magnetohydrodynamic(MHD)control effectively enhances the aerothermal environment of aerospace vehicles,demonstrating considerable potential in plasma flow regulation and aerodynamic optimiza-tion.As aerospace vehicles progress toward mid-low-altitude hypersonic regimes,their external aerothermal conditions become increasingly severe.This study addresses the challenges of complex aerodynamic force/heat environments and the difficulties in MHD control numerical simulations for hypersonic vehicles at mid-low al-titudes.On the basis of the perfect gas model and the low magnetic Reynolds number assumption,we conduct numerical simulations of MHD control under mid-low altitudes,high-Mach-number conditions.The findings reveal the following:(1)the low magnetic Reynolds number assumption is valid and computationally accurate,as corroborated by a comparative analysis with the literature;(2)in the mid-low altitude hypersonic regime,magnetic fields significantly suppress the shock standoffdistance and reduce the surface heat flux.Both the mag-netically controlled shock wave and the thermal protection exhibit nonlinear variations with the Mach number,increasing and then decreasing as the Mach number increases.The optimal Mach number for shock wave control is 13,whereas optimal thermal protection is achieved at Mach 15.At an altitude of 40 km,the optimal magne-tohydrodynamic Mach range spans 13-17,achieving a maximum heat flux attenuation of 28.81%.Additionally,the effects of magnetic shock wave control correlate approximately exponentially with altitude within certain parameters,whereas the efficacy of thermal protection behaves linearly with altitude variations.展开更多
Objectives This study aimed to compare the effectiveness of the semi-virtual simulation and traditional simulation teaching models based on the Standards of Best Practice(SOBP)according to the International Nursing As...Objectives This study aimed to compare the effectiveness of the semi-virtual simulation and traditional simulation teaching models based on the Standards of Best Practice(SOBP)according to the International Nursing Association for Clinical Simulation and Learning(INACSL)in the Adult Nursing course.Methods This study used a quasi-experimental design.A total of 94 third-year nursing students from a university in Beijing between November and December 2022 were recruited as participants.An innovative semi-virtual simulation teaching model was designed based on the SOBP established by the INACSL.In the Adult Nursing course,both the semi-virtual and traditional simulation teaching models were implemented.At the end of the simulation sessions,participants completed the Chinese version of the Simulation Effectiveness Tool-Modified(SET-M)to assess the effectiveness of the two teaching models.Results All nursing students completed the simulation sessions.There was no difference(t=−0.93,P=0.353)in the total scores between the semi-virtual simulation teaching model(50.87±5.30)and the traditional simulation teaching model(50.37±5.16).However,there was a statistically significant difference(t=−2.65,P=0.010)in the prebriefing section(semi-virtual simulation:5.60±0.71;traditional simulation:5.33±0.78).In contrast,no statistically significant differences were found for the scenario and debriefing sections(P>0.05).At the individual item level,statistical differences(P<0.05)between the two models were identified for items 1 and 9,but not for the remaining items(P>0.05).By analyzing the open-ended question,it was found that both simulation models were effective,and students’comments were similar.Conclusions The study demonstrated equivalent effectiveness between the semi-virtual and traditional simulation teaching models.Semi-virtual simulation teaching model could offer a more flexible and feasible approach to simulation teaching.展开更多
This paper introduces the experience and practice in constructing the practical teaching system for the course“Electric Machine and Drive.”In response to the current status of cultivating innovative practical abilit...This paper introduces the experience and practice in constructing the practical teaching system for the course“Electric Machine and Drive.”In response to the current status of cultivating innovative practical abilities among electrical engineering majors,based on the independently developed virtual simulation experimental teaching platform for Electric Machine and Drive,a stepped practical teaching process consisting of“classroom teaching-experimental teaching-comprehensive training-scientific inquiry”has been elaborately designed.A hierarchical practical teaching model for the second classroom has also been established.With teaching objectives as the optimization index,the teaching content,methods and means have been optimized;the teaching process has been organized and implemented in the form of team collaboration,thus constructing a comprehensive,stepped,hierarchical,and closed-loop innovative practical teaching system.This achievement provides references and assistance for the practical teaching of the same or similar majors in other colleges and universities.展开更多
This study presents the results of a Monte Carlo simulation to compare the statistical power of Siegel-Tukey and Savage tests.The main purpose of the study is to evaluate the statistical power of both tests in scenari...This study presents the results of a Monte Carlo simulation to compare the statistical power of Siegel-Tukey and Savage tests.The main purpose of the study is to evaluate the statistical power of both tests in scenarios involving Normal,Platykurtic and Skewed distributions over different sample sizes and standard deviation values.In the study,standard deviation ratios were set as 2,3,4,1/2,1/3 and 1/4 and power comparisons were made between small and large sample sizes.For equal sample sizes,small sample sizes of 5,8,10,12,16 and 20 and large sample sizes of 25,50,75 and 100 were used.For different sample sizes,the combinations of(4,16),(8,16),(10,20),(16,4),(16,8)and(20,10)small sample sizes and(10,30),(30,10),(50,75),(50,100),(75,50),(75,100),(100,50)and(100,75)large sample sizes were examined in detail.According to the findings,the power analysis under variance heterogeneity conditions shows that the Siegel-Tukey test has a higher statistical power than the other nonparametric Savage test at small and large sample sizes.In particular,the Siegel-Tukey test was reported to offer higher precision and power under variance heterogeneity,regardless of having equal or different sample sizes.展开更多
As a renewable energy source,the thermal conversion of poultry manure,is a promising waste treatment solution that can generate circular economic outputs such as energy and reduce greenhouse gas emissions.Currently,pr...As a renewable energy source,the thermal conversion of poultry manure,is a promising waste treatment solution that can generate circular economic outputs such as energy and reduce greenhouse gas emissions.Currently,pressurized gasification of poultry manure is still a novel research field,especially when combined with a novel technological route of oxy-fuel gasification.Oxy-fuel gasification is a newly proposed and promising gasification technology for power generation that facilitates future carbon capture and storage.In this work,based on a commercially operated industrial-scale chicken manure gasification power plant in Singapore,we presented an interesting first exploration of the coupled pressurization technology for oxy-fuel gasification of poultry manure using CFD numerical simulation,analyzed the effects of pressure and oxygen enrichment concentration as well as the coupling mechanism between them,and discussed the conversion and emission of nitrogen-and sulfur-containing pollutants.The results indicate that under oxy-fuel gasification condition(Oxy-30,i.e.,30%O_(2)/70%CO_(2)),as the pressure increases from 0.1 to 0.5 MPa,the CO concentration in the syngas increases slightly,the H_(2)concentration increases to approximately 25%,and the CH4 concentration(less than 1%)decreases,resulting in an increase in the calorific value of syngas from 5.2 to 5.6 MJ·m^(-3).Compared to atmospheric pressure conditions,a relatively higher oxygen-enriched concentration interval(Oxy-40 to Oxy-50)under pressurized conditions is advantageous for autothermal gasification.Pressurization increases NO precursors production and also promotes homogeneous and heterogeneous reduction of NO,and provides favorable conditions for self-desulfurization.This work offers reference for the realization of a highly efficient and low-energy-consumption thermochemical treatment of livestock manure coupled with negative carbon emission technology.展开更多
The Trombe Wall(TW)is a low-cost,passive heating system known for its high thermal efficiency,particularly in cold and temperate climates.Recent research has explored its adaptability to warm-dry climates with high th...The Trombe Wall(TW)is a low-cost,passive heating system known for its high thermal efficiency,particularly in cold and temperate climates.Recent research has explored its adaptability to warm-dry climates with high thermal variability,such as those found in central Mexico.This study presents a dynamic simulation-based analysis of the TW’s thermal performance in a representative social housing unit located in Pachuca de Soto,Hidalgo.Two models were compared—one with a south-facing TW system and one without—to evaluate indoor thermal comfort throughout a full annual cycle.The simulations were conducted using OpenStudio and EnergyPlus,integrating detailed climate data and construction parameters.Results indicate significant improvements in interior temperature stability and comfort during winter,with temperature increases of up to 5.1℃ in living areas.The system’s implementation made it possible to attain a new level of average winter indoor temperature of 18.3℃ by using solar energy,up from 14.4℃ without mechanical heating.The introduction of the TW significantly reduces the interior thermal oscillation and enhances the habitability conditions during the winter,with an increase of 167%in the annual number of hours within the thermal comfort range of 18℃–24℃ vs.the base model.Currently,temperature fluctuations inside buildings due to climate change affect the health of users.The system presented in this study reduces these temperature fluctuations to improve quality of life.展开更多
In this study,the hydraulic behavior and sand transport efficiency of the siphon automatic sand discharge device were studied by software simulation tests.By simulating the actual situation,this study analyzed how fac...In this study,the hydraulic behavior and sand transport efficiency of the siphon automatic sand discharge device were studied by software simulation tests.By simulating the actual situation,this study analyzed how factors such as the difference in water level,sediment concentration,and pipeline layout affected the sediment discharge effect.The results show that the sediment discharge device can effectively discharge sediment under diverse operating conditions and show adaptability to different environmental conditions,which indicates that it is suitable for various types of reservoir environments.展开更多
The present paper analyses a case study of the application of dynamic energy simulation on the energy efficiency improvement process of an existing commercial building,the retrofit of a CHP machine for the combined ge...The present paper analyses a case study of the application of dynamic energy simulation on the energy efficiency improvement process of an existing commercial building,the retrofit of a CHP machine for the combined generation of heat and power is analysed.Great attention is dedicated to the correct sizing of the CHP/CCHP plant both in term of energy efficiency and economic viability.A detailed building model is developed and used,through dynamic building simulation,to identify the potential energy and economic savings achievable with the installation of a CHP/CCHP sized based on the results of the simulation itself.The work proves the usefulness of dynamic energy simulation as an evaluation tool for retrofits of CHP plants and provides suggestions on the correct sizing of CHP equipment.It is also meant to prove what could be achieved if those kinds of analysis were carried out during the design of the building.展开更多
文摘Ice crystal icing is an important cause of accidents in aircraft engines.Ice formation in aircraft engines can cause internal blades to freeze,affecting the quality of the air flow field and blocking the flow path.On the other hand,the entry of ice crystal particles into the combustion chamber can cause a decrease in temperature or even flameout,leading to engine surge or shutdown.Therefore,it is necessary to conduct multiphase flow tests on ice crystals for aircraft components such as aircraft engines.Conducting ice crystal multiphase flow tests on aircraft is an effective research method,but it requires the construction of an ice crystal multiphase flow test platform that meets relevant technical requirements.The paper focuses on the relevant experimental requirements and combines wind tunnel test structures to conduct multiphase flow numerical simulations on various forms of jet pipelines,obtaining particle motion distribution results.After comparison,the optimal form of jet structure is obtained,providing the best selection scheme for the design of relevant wind tunnel structures.
基金supported by the National Natural Science Foundation of China(Grant Nos.12388101 and 12472221)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2024-oy10).
文摘In sediment transport on a mobile erodible bed,near-bed particles tend to preferentially locate under specific flow regions and form an uneven bedform.These moving and mobile particles can significantly modulate turbulence at various scales,from inertial large-scale motions to small viscous motions.This study analyzes the particle-resolved direct numerical simulation data of particle-laden two-phase flow with multilayers of particles in turbulent flows over static and mobile beds.The double-average method is adopted for energy transfer analysis.The result shows that the alternative streaky bedform in the spanwise directions correlates with the streak structures in the near-wall turbulence in the mobile bed case.The energy redistribution and exchange,as well as the dissipation,are analyzed in detail,and an energy transfer diagram is given in the last to summarize the energy transfer processes.In both the static and mobile bed cases,flow energy is introduced into the system via the work performed by volume forces acting on the mean flow.The viscous dissipations in the double mean and form-induced fields are more pronounced in the static bed case,and the work done by the fluid-particle interfacial stress in the double mean and turbulent fields is more pronounced in the mobile bed case.The prominent energy contribution in the form-induced field is the production by the form-induced stress on the mean strain in the mobile bed case.In addition,sediment transport involving a limited number of mobile particles is insufficient to capture the energy transfer processes that occur over the troughs and may intertwine the energy transfer processes over the mobile particles and the fixed particle bed.
基金supported by National Natural Science Foundation of China(No.U23B20152).
文摘The deposition layer on the discharge channel wall of a Hall thruster after long-term operation occasionally detaches from the wall and interferes with the plasma inside the channel,resulting in current pulse and threatening the power supply.To understand the generation mechanism of the current pulse,the interaction between the peeling material and the channel plasma was studied by the particle-in-cell and Monte Carlo collision(PIC/MCC)method.The plasma evolution and distribution in the Hall thruster channel when peeling material existed were simulated.Simulation results show that the peeling material changes the electron transportation and ionization,and the effects are related to the position of the peeling material.When the peeling material invades the zone where the ionization rate is originally the highest without peeling material,the ionization process is almost terminated.The ionization suppression by the peeling material will cause the propellant gas to refill the channel exit.As the peeling material moves away,gas discharge is induced near the channel exit,resulting in anode current pulse.
基金Under the auspices of Zhejiang Provincial Natural Science Foundation of China(No.LY19C160007)。
文摘In recent years,rapid urbanization has had a profound impact on landscape stability.As a typical example of China's rapid urbanization,Hangzhou has also experienced significant landscape changes,which have profoundly affected its ecological stability.Taking Hangzhou as an example,this study integrates land use change data from 1980 to 2020,combines dynamic simulation and ecological modeling techniques,and carries out a comprehensive analysis of historical trends and future predictions,to provide valuable insights into the complex interactions between urban expansion and landscape stability.The results indicate that:1)between 1980 and2020,Hangzhou experienced a significant increase in construction land at the expense of arable land,leading to a gradual decline in landscape stability,though the downward trend has slowed in recent years.2)The spatial distribution of landscape stability shows clear aggregation patterns,with lower stability concentrated in economically active flatlands and higher stability in the mountainous western regions.3)By 2040,further urban expansion is predicted to occur alongside increased landscape integration,reflecting the positive effects of ecological protection strategies.This study highlights the universal challenges of balancing economic growth with ecological stability in rapidly urbanizing regions.The combination of advanced simulation models and spatiotemporal analysis demonstrates a replicable framework for assessing urban expansion's ecological impacts.These findings underscore the importance of tailoring urban planning and ecological policies to address regional disparities,providing valuable insights for sustainable urban development and landscape management globally.
文摘This study focuses on the thermal management of 4680-type cylindrical lithium-ion battery packs utilizing NCM811 chemistry.It establishes coupled multi-physics models for both immersion and serpentine cold plate cooling systems.Through a combination of numerical simulation and experimental validation,the technical advantages and mechanisms of immersion cooling are systematically explored.Simulation results indicate that under a 3C fast-charging condition(inlet temperature 20℃,flow rate 36 L/min),the immersion cooling structure 3demonstrates a triple enhancement in thermal performance compared to the cold plate structure 1:a 13.06%reduction in peak temperature,a 31.67%decrease in overall maximum temperature difference,and a 47.62%decrease in single-cell temperature deviation,while also reducing flow resistance by 33.61%.Furthermore,based on the immersion cooling model,a small battery module comprising seven cylindrical cells was designed for thermal runaway testing via nail penetration.The results show that the peak temperature of the triggered cell was limited to 437.6℃,with a controllable temperature rise gradient of only 3.35℃/s and a rapid cooling rate of 0.6℃/s.The maximum temperature rise of adjacent cells was just 64.8℃,effectively inhibiting thermal propagation.Post-test disassembly revealed that the non-triggered cells retained>99.2%of their original voltage and>99%structural integrity,confirming the module’s ability to achieve“localized failure with global stability.”
文摘[Objective]Precipitation events caused by Super Typhoon Doksuri in Fujian Province were simulated and evaluated based on the WRF model to provide a reference for typhoon precipitation simulation and forecasting in southeast coastal areas of China.[Methods]The next-generation mesoscale numerical weather prediction model WRF V4.3(The Weather Research and Forecasting Model)was used to simulate the precipitation caused by Typhoon Doksuri in Fujian Province in 2023.Observations from 86 meteorological stations with hourly rainfall records were used to evaluate the model’s performance.Six evaluation indices were used,including the correlation coefficient(R),root mean square error(RMSE),mean absolute error(MAE),equitable threat score(ETS),probability of detection(POD),and false alarm ratio(FAR).[Results](1)The temporal and spatial evolution of precipitation during Typhoon Doksuri was effectively captured by the WRF model.Precipitation intensity increased gradually from July 27 to 29,2023,with the heaviest rainfall concentrated in the northern and eastern coastal areas of Fujian Province.(2)Significant differences in model performance were observed in terms of R,RMSE,and MAE.The largest errors occurred in Putian City,while smaller errors were found in southwestern Fujian Province.The evaluation result of all six indices showed that the WRF model performed best in simulating daily precipitation compared to hourly,three-hourly,six-hourly,and twelve-hourly precipitation.(3)The R95p index indicated that the WRF model successfully captured the overall spatial distribution of extreme precipitation.However,extreme precipitation intensity was overestimated in certain coastal areas.(4)Despite accurately identifying the coastal regions of Fujian as being most affected,the WRF model failed to accurately simulate the spatial distribution and intensity of precipitation.The simulated precipitation centers showed discrepancies when compared with the observed centers.[Conclusion]Although the WRF model underestimated hourly precipitation,it successfully captured the temporal evolution and spatial distribution of rainfall caused by Typhoon Doksuri in Fujian Province.It reproduced the heavy rainfall centers in central Fujian Province,with daily precipitation peaks reaching up to 350 mm.This highlighted the severity of extreme rainfall caused by Typhoon Doksuri.
基金supported by the National Magnetic Confinement Fusion Energy R&D Program of China (Nos.2019YFE03030004 and 2022YFE03100001)。
文摘Tearing modes may play an important role in the density limit disruption.The Magnetohydrodynamic(MHD)code CLT with impurity modules is used to study the tearing mode excited and driven by impurity radiation.The impurity radiation can lead to plasma contraction and local enhancement of the current density.When the locally enhanced region of the current density approaches to the resonance surface,the tearing mode can be excited,even if the tearing mode is stable in the initial equilibrium.Through a scan of the initial atomic number(Z)and impurity concentrations,it is found that impurities with different Z values exhibit similar behaviors in the radiation-driven tearing mode.The impurity radiation can drive tearing mode growth through temperature cooling near the resonance surface,and there exists a linear relationship between the temperature perturbation caused by impurity radiation and the linear growth rate of the tearing mode.Additionally,the impurity can promote the growth of magnetic islands through the radiation cooling inside the magnetic island,and there exists a correlation between the initial parameters of impurity and the width of the saturated magnetic island.
基金support provided by the National Natural Science Foundation of China(Nos.22173051,21829301,21774066),PCSIRT(IRT1257)the College Discipline Innovation and Intelligence Introduction Program(111 Project(B16027)+2 种基金the International Cooperation Base(No.2016D01025)Tianjin International Joint Research and Development Center)P.Zhang acknowledges the financial support provided by NSFC(No.22473024).
文摘Stimuli-responsive polymers capable of rapidly altering their chain conformation in response to external stimuli exhibit broad applica-tion prospects.Experiments have shown that pressure plays a pivotal role in regulating the microscopic chain conformation of polymers in mixed solvents,and one notable finding is that increasing the pressure can lead to the vanishing of the co-nonsolvency effect.However,the mecha-nisms underlying this phenomenon remain unclear.In this study,we systematically investigated the influence of pressure on the co-nonsolvency effect of single-chain and multi-chain homopolymers in binary mixed good-solvent systems using molecular dynamics simulations.Our results show that the co-nonsolvency-induced chain conformation transition and aggregation behavior significantly depend on pressure in allsingle-chain and multi-chain systems.In single-chain systems,at low pressures,the polymer chain maintains a collapsed state over a wide range of co-solvent fractions(x-range)owing to the co-nonsolvency effect.As the pressure increases,the x-range of the collapsed state gradually narrows,ac-companied by a progressive expansion of the chain.In multichain systems,polymer chains assemble into approximately spherical aggregates over a broad x-range at low pressures owing to the co-nonsolvency effect.Increasing the pressure reduces the x-range for forming aggregates and leads to the formation of loose aggregates or even to a state of dispersed chains at some x-range.These findings indicate that increasing the pressure can weaken or even offset the co-nonsolvency effect in some x-range,which is in good agreement with the experimental observations.Quantitative analysis of the radial density distributions and radial distribution functions reveals that,with increasing pressure,(1)the densities of both polymers and co-solvent molecules within aggregates decrease,while that of the solvent molecule increases;and(2)the effective interac-tions between the polymer and the co-solvent weaken,whereas those between the polymer and solvent strengthen.This enhances the incorpo-ration of solvent molecules within the chains,thereby weakening or even suppressing the chain aggregation.Our study not only elucidates the regulatory mechanism of pressure on the microscopic chain conformations and aggregation behaviors of polymers,but also may provide theo-retical guidance for designing smart polymericmaterials based on mixed solvents.
基金supported by the National Natural Science Foundation of China(22078251,21706197)the Open Project of Hubei Key Laboratory of Novel Reactor and Green Chemical Technology(NRG202407)+1 种基金the Ministry-of-Education,Key Laboratory for the Synthesis and Application of Organic Functional Molecules(KLSAOFM2511)the Graduate Innovative Fund of Wuhan Institute of Technology(CX2023024)。
文摘The emerging two-dimensional(2D)membranes offer a promising way to improve the water desalination performance of traditional membranes.MXene/graphene oxide(GO) composite membrane are known for their high separation performance and structural stability.In this study,molecular simulations are performed to investigate the desalination performance of the 2D MXene/GO membrane.The results reveal that the surface of the MXene nanosheet could induce the formation of ordered water structures,thereby accelerating the water transport in the 2D membrane.The higher rejection rate would be found in MXene/GO membrane with a larger GO oxidation degree owing to the sterichindrance effect induced by the functional groups on the GO surface.Overall,the MXene/GO(20) membrane with the interlayer spacing of 0.9 nm shows the highest water permeability(37.22×10^(-7)L·m^(-1)·h^(-1)·bar^(-1),1 bar=0.1 MPa)and a salt rejection of 100%.The results could provide theoretical insights for developing 2D membranes for water desalination.
基金Project partially supported by the National Natural Science Foundation of China(Grant Nos.12275060 and12075223)the Fund from Frontier Science Center for Interaction between Space Environment and Matter(Grant No.5740401024)。
文摘This paper presents a numerical simulation of DC glow discharge at 2 Torr(1 Torr=1.33322×10~2 Pa)with a microhollow anode,using a two-dimensional(2D)PIC/MCC code to explore the impact of the hollow anode structure on discharge characteristics.Simulation results show that the plasma density in the anode channel decreases exponentially along the x-direction towards the outlet while the electric potential decreases linearly.The electron temperature,derived from the relationship between density and electric potential,shows a good agreement with the calculated temperature.The potential peak at the inlet,along with the grounded anode,forms a transverse potential well that draws electrons toward the center of the channel.The x-direction electric field,generated by the potential difference between the inlet and outlet of the anode,directs electrons toward the inlet of the anode.Low-energy electrons are confined within the potential well,while very few high-energy electrons outlet the channel.The hollow anode structure serves as a collimator for electrons,leading to an increment of moderate-velocity electron flux in the anode channel.Shortening the anode leads to a slower rate of density decrease,resulting in a higher density at the outlet.
基金the results of the research project funded by National Numerical Wind Tunnel Project of China.
文摘Hypersonic magnetohydrodynamic(MHD)control effectively enhances the aerothermal environment of aerospace vehicles,demonstrating considerable potential in plasma flow regulation and aerodynamic optimiza-tion.As aerospace vehicles progress toward mid-low-altitude hypersonic regimes,their external aerothermal conditions become increasingly severe.This study addresses the challenges of complex aerodynamic force/heat environments and the difficulties in MHD control numerical simulations for hypersonic vehicles at mid-low al-titudes.On the basis of the perfect gas model and the low magnetic Reynolds number assumption,we conduct numerical simulations of MHD control under mid-low altitudes,high-Mach-number conditions.The findings reveal the following:(1)the low magnetic Reynolds number assumption is valid and computationally accurate,as corroborated by a comparative analysis with the literature;(2)in the mid-low altitude hypersonic regime,magnetic fields significantly suppress the shock standoffdistance and reduce the surface heat flux.Both the mag-netically controlled shock wave and the thermal protection exhibit nonlinear variations with the Mach number,increasing and then decreasing as the Mach number increases.The optimal Mach number for shock wave control is 13,whereas optimal thermal protection is achieved at Mach 15.At an altitude of 40 km,the optimal magne-tohydrodynamic Mach range spans 13-17,achieving a maximum heat flux attenuation of 28.81%.Additionally,the effects of magnetic shock wave control correlate approximately exponentially with altitude within certain parameters,whereas the efficacy of thermal protection behaves linearly with altitude variations.
文摘Objectives This study aimed to compare the effectiveness of the semi-virtual simulation and traditional simulation teaching models based on the Standards of Best Practice(SOBP)according to the International Nursing Association for Clinical Simulation and Learning(INACSL)in the Adult Nursing course.Methods This study used a quasi-experimental design.A total of 94 third-year nursing students from a university in Beijing between November and December 2022 were recruited as participants.An innovative semi-virtual simulation teaching model was designed based on the SOBP established by the INACSL.In the Adult Nursing course,both the semi-virtual and traditional simulation teaching models were implemented.At the end of the simulation sessions,participants completed the Chinese version of the Simulation Effectiveness Tool-Modified(SET-M)to assess the effectiveness of the two teaching models.Results All nursing students completed the simulation sessions.There was no difference(t=−0.93,P=0.353)in the total scores between the semi-virtual simulation teaching model(50.87±5.30)and the traditional simulation teaching model(50.37±5.16).However,there was a statistically significant difference(t=−2.65,P=0.010)in the prebriefing section(semi-virtual simulation:5.60±0.71;traditional simulation:5.33±0.78).In contrast,no statistically significant differences were found for the scenario and debriefing sections(P>0.05).At the individual item level,statistical differences(P<0.05)between the two models were identified for items 1 and 9,but not for the remaining items(P>0.05).By analyzing the open-ended question,it was found that both simulation models were effective,and students’comments were similar.Conclusions The study demonstrated equivalent effectiveness between the semi-virtual and traditional simulation teaching models.Semi-virtual simulation teaching model could offer a more flexible and feasible approach to simulation teaching.
基金Project of the 14th Five-Year Plan for Educational Science in Liaoning Province(JG24DB234)Project of Graduate Education and Teaching Reform Research in Liaoning Province(LNYJG2023115)。
文摘This paper introduces the experience and practice in constructing the practical teaching system for the course“Electric Machine and Drive.”In response to the current status of cultivating innovative practical abilities among electrical engineering majors,based on the independently developed virtual simulation experimental teaching platform for Electric Machine and Drive,a stepped practical teaching process consisting of“classroom teaching-experimental teaching-comprehensive training-scientific inquiry”has been elaborately designed.A hierarchical practical teaching model for the second classroom has also been established.With teaching objectives as the optimization index,the teaching content,methods and means have been optimized;the teaching process has been organized and implemented in the form of team collaboration,thus constructing a comprehensive,stepped,hierarchical,and closed-loop innovative practical teaching system.This achievement provides references and assistance for the practical teaching of the same or similar majors in other colleges and universities.
文摘This study presents the results of a Monte Carlo simulation to compare the statistical power of Siegel-Tukey and Savage tests.The main purpose of the study is to evaluate the statistical power of both tests in scenarios involving Normal,Platykurtic and Skewed distributions over different sample sizes and standard deviation values.In the study,standard deviation ratios were set as 2,3,4,1/2,1/3 and 1/4 and power comparisons were made between small and large sample sizes.For equal sample sizes,small sample sizes of 5,8,10,12,16 and 20 and large sample sizes of 25,50,75 and 100 were used.For different sample sizes,the combinations of(4,16),(8,16),(10,20),(16,4),(16,8)and(20,10)small sample sizes and(10,30),(30,10),(50,75),(50,100),(75,50),(75,100),(100,50)and(100,75)large sample sizes were examined in detail.According to the findings,the power analysis under variance heterogeneity conditions shows that the Siegel-Tukey test has a higher statistical power than the other nonparametric Savage test at small and large sample sizes.In particular,the Siegel-Tukey test was reported to offer higher precision and power under variance heterogeneity,regardless of having equal or different sample sizes.
基金supported by the National Natural Science Foundation of China(52306131)the Natural Science Foundation of Jiangsu Province(BK20230847)+2 种基金the Key Project of the National Natural Science Foundation of China(52336005)the Fundamental Research Funds for the Central Universities(2242024RCB0036)the Open Project Program of State Key Laboratory of Low-carbon Smart Coal-fired Power Generation and Ultra-clean Emission(D2024FK156).
文摘As a renewable energy source,the thermal conversion of poultry manure,is a promising waste treatment solution that can generate circular economic outputs such as energy and reduce greenhouse gas emissions.Currently,pressurized gasification of poultry manure is still a novel research field,especially when combined with a novel technological route of oxy-fuel gasification.Oxy-fuel gasification is a newly proposed and promising gasification technology for power generation that facilitates future carbon capture and storage.In this work,based on a commercially operated industrial-scale chicken manure gasification power plant in Singapore,we presented an interesting first exploration of the coupled pressurization technology for oxy-fuel gasification of poultry manure using CFD numerical simulation,analyzed the effects of pressure and oxygen enrichment concentration as well as the coupling mechanism between them,and discussed the conversion and emission of nitrogen-and sulfur-containing pollutants.The results indicate that under oxy-fuel gasification condition(Oxy-30,i.e.,30%O_(2)/70%CO_(2)),as the pressure increases from 0.1 to 0.5 MPa,the CO concentration in the syngas increases slightly,the H_(2)concentration increases to approximately 25%,and the CH4 concentration(less than 1%)decreases,resulting in an increase in the calorific value of syngas from 5.2 to 5.6 MJ·m^(-3).Compared to atmospheric pressure conditions,a relatively higher oxygen-enriched concentration interval(Oxy-40 to Oxy-50)under pressurized conditions is advantageous for autothermal gasification.Pressurization increases NO precursors production and also promotes homogeneous and heterogeneous reduction of NO,and provides favorable conditions for self-desulfurization.This work offers reference for the realization of a highly efficient and low-energy-consumption thermochemical treatment of livestock manure coupled with negative carbon emission technology.
文摘The Trombe Wall(TW)is a low-cost,passive heating system known for its high thermal efficiency,particularly in cold and temperate climates.Recent research has explored its adaptability to warm-dry climates with high thermal variability,such as those found in central Mexico.This study presents a dynamic simulation-based analysis of the TW’s thermal performance in a representative social housing unit located in Pachuca de Soto,Hidalgo.Two models were compared—one with a south-facing TW system and one without—to evaluate indoor thermal comfort throughout a full annual cycle.The simulations were conducted using OpenStudio and EnergyPlus,integrating detailed climate data and construction parameters.Results indicate significant improvements in interior temperature stability and comfort during winter,with temperature increases of up to 5.1℃ in living areas.The system’s implementation made it possible to attain a new level of average winter indoor temperature of 18.3℃ by using solar energy,up from 14.4℃ without mechanical heating.The introduction of the TW significantly reduces the interior thermal oscillation and enhances the habitability conditions during the winter,with an increase of 167%in the annual number of hours within the thermal comfort range of 18℃–24℃ vs.the base model.Currently,temperature fluctuations inside buildings due to climate change affect the health of users.The system presented in this study reduces these temperature fluctuations to improve quality of life.
基金Supported by the National Undergraduate Innovation Training Program(Project No.202211437036).
文摘In this study,the hydraulic behavior and sand transport efficiency of the siphon automatic sand discharge device were studied by software simulation tests.By simulating the actual situation,this study analyzed how factors such as the difference in water level,sediment concentration,and pipeline layout affected the sediment discharge effect.The results show that the sediment discharge device can effectively discharge sediment under diverse operating conditions and show adaptability to different environmental conditions,which indicates that it is suitable for various types of reservoir environments.
文摘The present paper analyses a case study of the application of dynamic energy simulation on the energy efficiency improvement process of an existing commercial building,the retrofit of a CHP machine for the combined generation of heat and power is analysed.Great attention is dedicated to the correct sizing of the CHP/CCHP plant both in term of energy efficiency and economic viability.A detailed building model is developed and used,through dynamic building simulation,to identify the potential energy and economic savings achievable with the installation of a CHP/CCHP sized based on the results of the simulation itself.The work proves the usefulness of dynamic energy simulation as an evaluation tool for retrofits of CHP plants and provides suggestions on the correct sizing of CHP equipment.It is also meant to prove what could be achieved if those kinds of analysis were carried out during the design of the building.
