The flows behind the base of a generic rocket, at both hypersonic and subsonic flow conditions, are numerically studied. The main concerns are addressed to the evaluation of turbulence models and the using of grid ada...The flows behind the base of a generic rocket, at both hypersonic and subsonic flow conditions, are numerically studied. The main concerns are addressed to the evaluation of turbulence models and the using of grid adaptation techniques. The investigation focuses on two configurations, related to hypersonic and subsonic experiments. The applicability tests of different turbu- lence models are conducted on the level of two-equation models calculating the steady state solution of the Reynolds-averaged Navier-Stokes（RANS） equations. All used models, the original Wilcox k-co, the Menter shear-stress transport （SST） and the ex- plicit algebraic Reynolds stress model（EARSM） formulation, predict an asymmetric base flow in both cases caused by the support of the models. A comparison with preliminary experimental results indicates a preference for the SST and EARSM results over the results from the older k-co model. Sensitivity studies show no significant influence of the grid topology or the location of the laminar to turbulent transition on the base flow field, but a strong influence of even small angles of attack is reported from the related experiments.展开更多
This paper presents a sensitivity analysis method for analyzing the key factors affecting the stability problem of the transonic compressors.The adjoint method is integrated into the meridional stability model,a linea...This paper presents a sensitivity analysis method for analyzing the key factors affecting the stability problem of the transonic compressors.The adjoint method is integrated into the meridional stability model,a linear stability prediction model utilized to analyze the flow stability problem of the compressor,and the sensitivity analysis method is further developed for the flow stability problem of the compressor.The study selects the NASA Rot or 37,a transonic compressor,as the research object to verify the proposed method and explore the sensitive factors leading to the stall inception.The results of sensitivity analysis to both the flow parameters and the external source terms reveal that the stall inception is sensitive to the base flow field at the rotor tip and the stability margin of the compressor can be enhanced by improving the flow field at this region.Physical explanations are presented and discussed to correlate the three-dimensional flow field to the results obtained via the employed analysis method,which shows that flow structures and characteristics near the end-wall region,especially the tip leakage flow or the tip leakage vortex and its interaction with the shock wave,contribute to the stall inception.展开更多
Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend an...Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend and short-term fluctuation of the dam seepage behavior, two monitoring models were developed, one for the base flow effect and one for daily variation of dam seepage elements. In the first model, to avoid the influence of the time lag effect on the evaluation of seepage variation with the time effect component of seepage elements, the base values of the seepage element and the reservoir water level were extracted using the wavelet multi-resolution analysis method, and the time effect component was separated by the established base flow effect monitoring model. For the development of the daily variation monitoring model for dam seepage elements, all the previous factors, of which the measured time series prior to the dam seepage element monitoring time may have certain influence on the monitored results, were considered. Those factors that were positively correlated with the analyzed seepage element were initially considered to be the support vector machine(SVM) model input factors, and then the SVM kernel function-based sensitivity analysis was performed to optimize the input factor set and establish the optimized daily variation SVM model. The efficiency and rationality of the two models were verified by case studies of the water level of two piezometric tubes buried under the slope of a concrete gravity dam.Sensitivity analysis of the optimized SVM model shows that the influences of the daily variation of the upstream reservoir water level and rainfall on the daily variation of piezometric tube water level are processes subject to normal distribution.展开更多
Automatic Digital Orthophoto Map(DOM)generation plays an important role in many downstream works such as land use and cover detection,urban planning,and disaster assessment.Existing DOM generation methods can generate...Automatic Digital Orthophoto Map(DOM)generation plays an important role in many downstream works such as land use and cover detection,urban planning,and disaster assessment.Existing DOM generation methods can generate promising results but always need ground object filtered DEM generation before otho-rectification;this can consume much time and produce building facade contained results.To address this problem,a pixel-by-pixel digital differential rectification-based automatic DOM generation method is proposed in this paper.Firstly,3D point clouds with texture are generated by dense image matching based on an optical flow field for a stereo pair of images,respectively.Then,the grayscale of the digital differential rectification image is extracted directly from the point clouds element by element according to the nearest neighbor method for matched points.Subsequently,the elevation is repaired grid-by-grid using the multi-layer Locally Refined B-spline(LR-B)interpolation method with triangular mesh constraint for the point clouds void area,and the grayscale is obtained by the indirect scheme of digital differential rectification to generate the pixel-by-pixel digital differentially rectified image of a single image slice.Finally,a seamline network is automatically searched using a disparity map optimization algorithm,and DOM is smartly mosaicked.The qualitative and quantitative experimental results on three datasets were produced and evaluated,which confirmed the feasibility of the proposed method,and the DOM accuracy can reach 1 Ground Sample Distance(GSD)level.The comparison experiment with the state-of-the-art commercial softwares showed that the proposed method generated DOM has a better visual effect on building boundaries and roof completeness with comparable accuracy and computational efficiency.展开更多
In the present study,the base pressure variations induced by the presence of a cavity,known to have a strong influence of the behaviour of supersonic projectiles,are investigated through numerical solution of the bala...In the present study,the base pressure variations induced by the presence of a cavity,known to have a strong influence of the behaviour of supersonic projectiles,are investigated through numerical solution of the balance equations for mass,momentum,and energy.An area ratio of four is considered and numerical simulations are carried out at Mach M=1.2,1.4,1.6,and 1.8 assuming no cavity or cavity locations 0.5D,1D,1.5D,and 2D.The inlet pressure of the nozzle is considered as a flow variable.The Taguchi method is also used,and the considered cases are then analyzed using a full factorial experimental design.The results show that the cavity is effective in increasing the base pressure for the conditions examined.For other nozzle pressure ratios,cavities do not lead to passive control due the change in the reattachment length.The distribution of wall pressure reveals that,in general,a cavity used to implement passive control of the base pressure does not adversely influence the flow pattern in the domain.展开更多
The hybrid flow shop scheduling problem with unrelated parallel machine is a typical NP-hard combinatorial optimization problem, and it exists widely in chemical, manufacturing and pharmaceutical industry. In this wor...The hybrid flow shop scheduling problem with unrelated parallel machine is a typical NP-hard combinatorial optimization problem, and it exists widely in chemical, manufacturing and pharmaceutical industry. In this work, a novel mathematic model for the hybrid flow shop scheduling problem with unrelated parallel machine(HFSPUPM) was proposed. Additionally, an effective hybrid estimation of distribution algorithm was proposed to solve the HFSPUPM, taking advantage of the features in the mathematic model. In the optimization algorithm, a new individual representation method was adopted. The(EDA) structure was used for global search while the teaching learning based optimization(TLBO) strategy was used for local search. Based on the structure of the HFSPUPM, this work presents a series of discrete operations. Simulation results show the effectiveness of the proposed hybrid algorithm compared with other algorithms.展开更多
An analytical simulation based on a new model incorporating surface interaction is conducted to study the slip phenomenon in the Couette flow at different scales. The velocity profile is calculated by taking account o...An analytical simulation based on a new model incorporating surface interaction is conducted to study the slip phenomenon in the Couette flow at different scales. The velocity profile is calculated by taking account of the micro-force between molecules and macro-force from the viscous shearing effect, as they contribute to the achieve- ment of the slip length. The calculated results are compared with those obtained from the molecular dynamics simulation, showing an excellent agreement. Further, the effect of the shear rate on the slip is investigated. The results can well predict the fluid flow behaviors on a solid substrate, but has to be proved by experiment.展开更多
Metal organic chenlical vapor deposition （AIOCVD） growth systems arc one of the. main types of equipment used for growing single crystal materials, such as GaN. To obtain fihn epitaxial materials with uniform perfor...Metal organic chenlical vapor deposition （AIOCVD） growth systems arc one of the. main types of equipment used for growing single crystal materials, such as GaN. To obtain fihn epitaxial materials with uniform performanee, the flow field and ternperature field in a GaN-MOCVD reactor are investigated by modeling and simulating. To make the simulation results more consistent with the actual situation, the gases in the reactor are considered to be compressible, making it possible to investigate the distributions of gas density and pressure in the reactor. The computational fluid dynamics method is used to stud,v the effects of inlet gas flow velocity, pressure in the reactor, rotational speed of graphite susceptor, and gases used in the growth, which has great guiding~ significance for the growth of GaN fihn materials.展开更多
The most controversial river in Thailand is the Yom River.It has not been modified by large dam because of several valuable natural resources.Therefore,the river is flooded in rainy season and very low flow in dry sea...The most controversial river in Thailand is the Yom River.It has not been modified by large dam because of several valuable natural resources.Therefore,the river is flooded in rainy season and very low flow in dry season.The low flow causes drought which is much more serious than flooding.The Yom River Basin management is only way to circumvent the low flow problem by studying base flow index(BFI).Base flow analyses for 8 gauging stations along the river were performed by 2 techniques i.e.graphical and modified U.K.Institute of Hydrology(MIH).The mean BFI results from graphical and MIH are 0.37(0.05)and 0.45(0.12).The result from graphical is more reasonable due to its lower standard deviation.BFI values from MIH vary with watershed area which may result from the using of fixing value of N-day at 10.Solution for this problem is ongoing in this study.展开更多
In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strai...In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strain rate range of 0.008-5 s^-1. Based on the true stress-true strain curves, a constitutive equation in hyperbolic sin function was established and a hot processing map was drawn. It was found that the flow stress of the Co-Cu alloy increased with the increase of the strain rate and decreased with the increase of the deforming temperature. The hot processing map indicated that there were two unstable regions and one well-processing region. The microstructure, the hardness distribution and the electro- chemical properties of the hot deformed sample were investigated in order to reveal the influence of the hot deformation. Microstructure observation indicated that the grain size increased with the increase of the deformation temperature but decreased with the increase of the strain rate. High temperature and low strain rate promoted the crystallization process but increased the grain size, which results in a reduction in the hardness. The hot deformation at high temperature （1100-1150 ℃） would reduce the corrosion resistance slightly. The final optimized deformation process was： a deformation temperature from 1050to 1100 ℃, and a strain rate from 0.008 to 0.2 s^-1, where a completely recrystallized and homogeneously distributed microstructure would be obtained.展开更多
The contribution of groundwater (GW) to the nitrate loads in surface waters (SW) was exemplarily studied for the river Augraben with a catchment area of 89.9 km2, located in north eastern Germany. The study uses avail...The contribution of groundwater (GW) to the nitrate loads in surface waters (SW) was exemplarily studied for the river Augraben with a catchment area of 89.9 km2, located in north eastern Germany. The study uses available GW and SW quality data in order to develop a relationship between SW and GW in the Augraben catchment. The calculated ratio of base flow varies from 40% to 80% using various filtering methods of hydrograph separation methods (without taking into account the drainage) in comparison to a calculated GW infiltration of 5% - 7% applying Darcy’s law (upper unconfined aquifer). Drainage was estimated as the difference in base flow obtained through filtering methods of hydrograph separation and the Darcy’s law. Results on the basis of monitoring data and hydrograph separation in quick flow and base flow showed that during winter periods, high concentration in SW has been found parallel to periods of higher GW flow with a strong correlation between SW and GW concentrations. These findings also coincided with the non-vegetation period, i.e. low nitrogen uptake by plants. Overall, nitrate-nitrogen loads at the SW monitoring point (Bei Lindenberg represents the 85% area of the catchment) were 193.5, 97.72, and 122 tons for the year 2010, 2011 and 2012 respectively. Measured GW concentrations in the catchment differ strongly, depending on land use, with elevated concentrations in agricultural areas compared to monitoring points in grass land and in forest areas. In one GW monitoring station, NO3 concentrations exceed the maximum permissible limits (MPL) according to EU water quality standards (MPL = 50 mg/l NO3), up to factor two. High ammonia concentrations at another station may be due to excessive application of manure. The contribution of the different sub-catchments to nitrate load in SW can be ranked in decreasing order in Zone B, D, A and C. Drainage and interflow proved to be a major contributor with 55% - 65% of total load in SW. With the applied method a robust estimation of GW contribution to nitrate loads is feasible using typically available monitoring data of German environmental authorities.展开更多
Based on the existing achievements in the basin comprehensive planning, water resources comprehensive planning, water resources protection planning, water allocation scheme, etc., the ecological flow assurance situati...Based on the existing achievements in the basin comprehensive planning, water resources comprehensive planning, water resources protection planning, water allocation scheme, etc., the ecological flow assurance situation is evaluated, and the degree of ecological flow assurance and the reasons for the deficiency are analyzed. On this basis, carry out theoretical calculation of ecological base flow, analyze the rationality and accessibility of theoretical calculation results, finally determine the ecological water volume of important rivers and their main control sections, form the recommended results, and study and put forward the ideas and countermeasures for ensuring the ecological water volume (flow) of important rivers.展开更多
For a single degree of freedom damped system with dynamic vibration absorbers (DVAs), a correct mobility matrix of the system on the basis of structure mobility theory is studied in this paper. In addition, analyzed a...For a single degree of freedom damped system with dynamic vibration absorbers (DVAs), a correct mobility matrix of the system on the basis of structure mobility theory is studied in this paper. In addition, analyzed are the expressions of the total power flow input from vibration source to the system, the net power flow transmitted to the main vibration system and the power flow absorbed by DVAs. Furthermore, the control mechanism of DVAs on the transmission characteristics of the power flow is revealed. Finally, an approach to the optimum design of DVAs is proposed in which the power flow is regarded as the control object, and the ordonnance relations among optimum parameters of DVAs dealt with.展开更多
Iron-based aqueous redox flow batteries(IBA-RFBs)represent a promising solution for long-duration energy storage,supporting the integration of intermittent renewable energy into the grid,thanks to their commendable sa...Iron-based aqueous redox flow batteries(IBA-RFBs)represent a promising solution for long-duration energy storage,supporting the integration of intermittent renewable energy into the grid,thanks to their commendable safety profile and cost-effectiveness.Membranes,serving as pivotal components in redox flow batteries(RFBs),play a crucial role in facilitating ion conduction for internal circuit formation while preventing the crossover of redox-active species.Given their direct impact on RFB performance and cost,membranes merit considerable attention.This review provides an overview of recent advancements in membranes tailored for IBA-RFBs.Initially,it delineates the operational mechanisms of various IBA-RFB configurations.Subsequently,it delves into key performance metrics for evaluating membrane efficacy,dissecting the intricate interplay between membrane performance and overall IBA-RFB efficiency.Building upon this foundation,the review spotlights recent breakthroughs in ion exchange membranes and porous membranes designed specifically for IBA-RFBs,showcasing their remarkable ability to bolster battery efficiency,cycling stability,and cost-effectiveness.Lastly,this review outlines future directions for membrane development,offering some insights to propel the widespread adoption of IBA-RFBs on a large scale.展开更多
Addressing the pressing demand for rapid and inexpensive coagulation testing in cardiovascular care,this study introduces a novel application of repurposed COVID-19 rapid antigen tests(RATs)as paper-based lateral flow...Addressing the pressing demand for rapid and inexpensive coagulation testing in cardiovascular care,this study introduces a novel application of repurposed COVID-19 rapid antigen tests(RATs)as paper-based lateral flow assays(LFAs)combined with machine learning for coagulation status evaluation.By further developing a mobile app prototype,we present a platform that enables clinicians to perform immediate and accurate anticoagulant dosing adjustments using existing post-pandemic resources.Our proof-of-concept employs a random forest machine learning classifier to interpret image feature variations on RAT NC membrane,correlating red blood cell(RBC)wicked diffusion distance in recalcified citrated whole blood with changes in coagulative viscosity,easily interpreted.Enhanced by confocal imaging studies of paper microfluidics,our approach provides insights into the mechanisms dissecting coagulation components,achieving high classification precision,recall,and F1-scores.The inverse relationship between RBC wicked diffusion distance and enoxaparin concentration paves the way for machine learning to inform real-time dose prescription adjustments,aligning with individual patient profiles to optimize therapeutic outcomes.This study not only demonstrates the potential of leveraging surplus RATs for coagulation management but also exemplifies a cost-effective,rapid,and smart strategy to enhance clinical decision-making in the post-pandemic era.展开更多
基金German Research Foundation (Deutsche Forschungs-gemeinschaft-DFG) Sonderforschungsbereich Transregio 40
文摘The flows behind the base of a generic rocket, at both hypersonic and subsonic flow conditions, are numerically studied. The main concerns are addressed to the evaluation of turbulence models and the using of grid adaptation techniques. The investigation focuses on two configurations, related to hypersonic and subsonic experiments. The applicability tests of different turbu- lence models are conducted on the level of two-equation models calculating the steady state solution of the Reynolds-averaged Navier-Stokes（RANS） equations. All used models, the original Wilcox k-co, the Menter shear-stress transport （SST） and the ex- plicit algebraic Reynolds stress model（EARSM） formulation, predict an asymmetric base flow in both cases caused by the support of the models. A comparison with preliminary experimental results indicates a preference for the SST and EARSM results over the results from the older k-co model. Sensitivity studies show no significant influence of the grid topology or the location of the laminar to turbulent transition on the base flow field, but a strong influence of even small angles of attack is reported from the related experiments.
基金supported by the National Natural Science Foundation of China(Nos.52306036,52325602 and U2441279)the National Science and Technology Major Project,China(Nos.Y2022-Ⅱ-0003-0006 and Y2022-Ⅱ-0002-0005)supported by the Project of National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics,China(Nos.6142702200101 and 2024-CXPT-GF-JJ-88-0103)。
文摘This paper presents a sensitivity analysis method for analyzing the key factors affecting the stability problem of the transonic compressors.The adjoint method is integrated into the meridional stability model,a linear stability prediction model utilized to analyze the flow stability problem of the compressor,and the sensitivity analysis method is further developed for the flow stability problem of the compressor.The study selects the NASA Rot or 37,a transonic compressor,as the research object to verify the proposed method and explore the sensitive factors leading to the stall inception.The results of sensitivity analysis to both the flow parameters and the external source terms reveal that the stall inception is sensitive to the base flow field at the rotor tip and the stability margin of the compressor can be enhanced by improving the flow field at this region.Physical explanations are presented and discussed to correlate the three-dimensional flow field to the results obtained via the employed analysis method,which shows that flow structures and characteristics near the end-wall region,especially the tip leakage flow or the tip leakage vortex and its interaction with the shock wave,contribute to the stall inception.
基金supported by the National Natural Science Foundation of China(Grant No.51709021)the Open Foundation of the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(Grant No.2016491111)
文摘Affected by external environmental factors and evolution of dam performance, dam seepage behavior shows nonlinear time-varying characteristics. In this study, to predict and evaluate the long-term development trend and short-term fluctuation of the dam seepage behavior, two monitoring models were developed, one for the base flow effect and one for daily variation of dam seepage elements. In the first model, to avoid the influence of the time lag effect on the evaluation of seepage variation with the time effect component of seepage elements, the base values of the seepage element and the reservoir water level were extracted using the wavelet multi-resolution analysis method, and the time effect component was separated by the established base flow effect monitoring model. For the development of the daily variation monitoring model for dam seepage elements, all the previous factors, of which the measured time series prior to the dam seepage element monitoring time may have certain influence on the monitored results, were considered. Those factors that were positively correlated with the analyzed seepage element were initially considered to be the support vector machine(SVM) model input factors, and then the SVM kernel function-based sensitivity analysis was performed to optimize the input factor set and establish the optimized daily variation SVM model. The efficiency and rationality of the two models were verified by case studies of the water level of two piezometric tubes buried under the slope of a concrete gravity dam.Sensitivity analysis of the optimized SVM model shows that the influences of the daily variation of the upstream reservoir water level and rainfall on the daily variation of piezometric tube water level are processes subject to normal distribution.
基金supported by the National Natural Science Foundation of China[Grant No.41771479]the National High-Resolution Earth Observation System(the Civil Part)[Grant No.50-H31D01-0508-13/15]the Japan Society for the Promotion of Science[Grant No.22H03573].
文摘Automatic Digital Orthophoto Map(DOM)generation plays an important role in many downstream works such as land use and cover detection,urban planning,and disaster assessment.Existing DOM generation methods can generate promising results but always need ground object filtered DEM generation before otho-rectification;this can consume much time and produce building facade contained results.To address this problem,a pixel-by-pixel digital differential rectification-based automatic DOM generation method is proposed in this paper.Firstly,3D point clouds with texture are generated by dense image matching based on an optical flow field for a stereo pair of images,respectively.Then,the grayscale of the digital differential rectification image is extracted directly from the point clouds element by element according to the nearest neighbor method for matched points.Subsequently,the elevation is repaired grid-by-grid using the multi-layer Locally Refined B-spline(LR-B)interpolation method with triangular mesh constraint for the point clouds void area,and the grayscale is obtained by the indirect scheme of digital differential rectification to generate the pixel-by-pixel digital differentially rectified image of a single image slice.Finally,a seamline network is automatically searched using a disparity map optimization algorithm,and DOM is smartly mosaicked.The qualitative and quantitative experimental results on three datasets were produced and evaluated,which confirmed the feasibility of the proposed method,and the DOM accuracy can reach 1 Ground Sample Distance(GSD)level.The comparison experiment with the state-of-the-art commercial softwares showed that the proposed method generated DOM has a better visual effect on building boundaries and roof completeness with comparable accuracy and computational efficiency.
文摘In the present study,the base pressure variations induced by the presence of a cavity,known to have a strong influence of the behaviour of supersonic projectiles,are investigated through numerical solution of the balance equations for mass,momentum,and energy.An area ratio of four is considered and numerical simulations are carried out at Mach M=1.2,1.4,1.6,and 1.8 assuming no cavity or cavity locations 0.5D,1D,1.5D,and 2D.The inlet pressure of the nozzle is considered as a flow variable.The Taguchi method is also used,and the considered cases are then analyzed using a full factorial experimental design.The results show that the cavity is effective in increasing the base pressure for the conditions examined.For other nozzle pressure ratios,cavities do not lead to passive control due the change in the reattachment length.The distribution of wall pressure reveals that,in general,a cavity used to implement passive control of the base pressure does not adversely influence the flow pattern in the domain.
基金Projects(61573144,61773165,61673175,61174040)supported by the National Natural Science Foundation of ChinaProject(222201717006)supported by the Fundamental Research Funds for the Central Universities,China
文摘The hybrid flow shop scheduling problem with unrelated parallel machine is a typical NP-hard combinatorial optimization problem, and it exists widely in chemical, manufacturing and pharmaceutical industry. In this work, a novel mathematic model for the hybrid flow shop scheduling problem with unrelated parallel machine(HFSPUPM) was proposed. Additionally, an effective hybrid estimation of distribution algorithm was proposed to solve the HFSPUPM, taking advantage of the features in the mathematic model. In the optimization algorithm, a new individual representation method was adopted. The(EDA) structure was used for global search while the teaching learning based optimization(TLBO) strategy was used for local search. Based on the structure of the HFSPUPM, this work presents a series of discrete operations. Simulation results show the effectiveness of the proposed hybrid algorithm compared with other algorithms.
基金Supported by the National Natural Science Foundation of China under Grant No 51305033the Ministry of National Defense of China under Grant No 9140C340506
文摘An analytical simulation based on a new model incorporating surface interaction is conducted to study the slip phenomenon in the Couette flow at different scales. The velocity profile is calculated by taking account of the micro-force between molecules and macro-force from the viscous shearing effect, as they contribute to the achieve- ment of the slip length. The calculated results are compared with those obtained from the molecular dynamics simulation, showing an excellent agreement. Further, the effect of the shear rate on the slip is investigated. The results can well predict the fluid flow behaviors on a solid substrate, but has to be proved by experiment.
基金Supported by the National Key R&D Program of China under Grant No 2016YFB0400104
文摘Metal organic chenlical vapor deposition （AIOCVD） growth systems arc one of the. main types of equipment used for growing single crystal materials, such as GaN. To obtain fihn epitaxial materials with uniform performanee, the flow field and ternperature field in a GaN-MOCVD reactor are investigated by modeling and simulating. To make the simulation results more consistent with the actual situation, the gases in the reactor are considered to be compressible, making it possible to investigate the distributions of gas density and pressure in the reactor. The computational fluid dynamics method is used to stud,v the effects of inlet gas flow velocity, pressure in the reactor, rotational speed of graphite susceptor, and gases used in the growth, which has great guiding~ significance for the growth of GaN fihn materials.
文摘The most controversial river in Thailand is the Yom River.It has not been modified by large dam because of several valuable natural resources.Therefore,the river is flooded in rainy season and very low flow in dry season.The low flow causes drought which is much more serious than flooding.The Yom River Basin management is only way to circumvent the low flow problem by studying base flow index(BFI).Base flow analyses for 8 gauging stations along the river were performed by 2 techniques i.e.graphical and modified U.K.Institute of Hydrology(MIH).The mean BFI results from graphical and MIH are 0.37(0.05)and 0.45(0.12).The result from graphical is more reasonable due to its lower standard deviation.BFI values from MIH vary with watershed area which may result from the using of fixing value of N-day at 10.Solution for this problem is ongoing in this study.
基金financially supported by the National Natural Science Foundation of China (Nos. 81071262, 31271024 and 31470930)the Funding from Northeastern University ("985 program", Nos. N141008001 and LZ2014018), China
文摘In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strain rate range of 0.008-5 s^-1. Based on the true stress-true strain curves, a constitutive equation in hyperbolic sin function was established and a hot processing map was drawn. It was found that the flow stress of the Co-Cu alloy increased with the increase of the strain rate and decreased with the increase of the deforming temperature. The hot processing map indicated that there were two unstable regions and one well-processing region. The microstructure, the hardness distribution and the electro- chemical properties of the hot deformed sample were investigated in order to reveal the influence of the hot deformation. Microstructure observation indicated that the grain size increased with the increase of the deformation temperature but decreased with the increase of the strain rate. High temperature and low strain rate promoted the crystallization process but increased the grain size, which results in a reduction in the hardness. The hot deformation at high temperature （1100-1150 ℃） would reduce the corrosion resistance slightly. The final optimized deformation process was： a deformation temperature from 1050to 1100 ℃, and a strain rate from 0.008 to 0.2 s^-1, where a completely recrystallized and homogeneously distributed microstructure would be obtained.
基金a DAAD PhD grant in collaboration with the research project Bootmonitoring in the BMBF program REWAM(FKZ:033W039A-F).
文摘The contribution of groundwater (GW) to the nitrate loads in surface waters (SW) was exemplarily studied for the river Augraben with a catchment area of 89.9 km2, located in north eastern Germany. The study uses available GW and SW quality data in order to develop a relationship between SW and GW in the Augraben catchment. The calculated ratio of base flow varies from 40% to 80% using various filtering methods of hydrograph separation methods (without taking into account the drainage) in comparison to a calculated GW infiltration of 5% - 7% applying Darcy’s law (upper unconfined aquifer). Drainage was estimated as the difference in base flow obtained through filtering methods of hydrograph separation and the Darcy’s law. Results on the basis of monitoring data and hydrograph separation in quick flow and base flow showed that during winter periods, high concentration in SW has been found parallel to periods of higher GW flow with a strong correlation between SW and GW concentrations. These findings also coincided with the non-vegetation period, i.e. low nitrogen uptake by plants. Overall, nitrate-nitrogen loads at the SW monitoring point (Bei Lindenberg represents the 85% area of the catchment) were 193.5, 97.72, and 122 tons for the year 2010, 2011 and 2012 respectively. Measured GW concentrations in the catchment differ strongly, depending on land use, with elevated concentrations in agricultural areas compared to monitoring points in grass land and in forest areas. In one GW monitoring station, NO3 concentrations exceed the maximum permissible limits (MPL) according to EU water quality standards (MPL = 50 mg/l NO3), up to factor two. High ammonia concentrations at another station may be due to excessive application of manure. The contribution of the different sub-catchments to nitrate load in SW can be ranked in decreasing order in Zone B, D, A and C. Drainage and interflow proved to be a major contributor with 55% - 65% of total load in SW. With the applied method a robust estimation of GW contribution to nitrate loads is feasible using typically available monitoring data of German environmental authorities.
文摘Based on the existing achievements in the basin comprehensive planning, water resources comprehensive planning, water resources protection planning, water allocation scheme, etc., the ecological flow assurance situation is evaluated, and the degree of ecological flow assurance and the reasons for the deficiency are analyzed. On this basis, carry out theoretical calculation of ecological base flow, analyze the rationality and accessibility of theoretical calculation results, finally determine the ecological water volume of important rivers and their main control sections, form the recommended results, and study and put forward the ideas and countermeasures for ensuring the ecological water volume (flow) of important rivers.
文摘For a single degree of freedom damped system with dynamic vibration absorbers (DVAs), a correct mobility matrix of the system on the basis of structure mobility theory is studied in this paper. In addition, analyzed are the expressions of the total power flow input from vibration source to the system, the net power flow transmitted to the main vibration system and the power flow absorbed by DVAs. Furthermore, the control mechanism of DVAs on the transmission characteristics of the power flow is revealed. Finally, an approach to the optimum design of DVAs is proposed in which the power flow is regarded as the control object, and the ordonnance relations among optimum parameters of DVAs dealt with.
基金supported by the National Natural Science Foundation of China(22022813)the Zhejiang Provincial Natural Science Foundation of China(LQ24B030002)+1 种基金the China Postdoctoral Science Foundation(2022M722729 and 2023T160571)the technology project of Institute of Wenzhou(XMGL-CX-202204 and XMGL-KJZX-202208).
文摘Iron-based aqueous redox flow batteries(IBA-RFBs)represent a promising solution for long-duration energy storage,supporting the integration of intermittent renewable energy into the grid,thanks to their commendable safety profile and cost-effectiveness.Membranes,serving as pivotal components in redox flow batteries(RFBs),play a crucial role in facilitating ion conduction for internal circuit formation while preventing the crossover of redox-active species.Given their direct impact on RFB performance and cost,membranes merit considerable attention.This review provides an overview of recent advancements in membranes tailored for IBA-RFBs.Initially,it delineates the operational mechanisms of various IBA-RFB configurations.Subsequently,it delves into key performance metrics for evaluating membrane efficacy,dissecting the intricate interplay between membrane performance and overall IBA-RFB efficiency.Building upon this foundation,the review spotlights recent breakthroughs in ion exchange membranes and porous membranes designed specifically for IBA-RFBs,showcasing their remarkable ability to bolster battery efficiency,cycling stability,and cost-effectiveness.Lastly,this review outlines future directions for membrane development,offering some insights to propel the widespread adoption of IBA-RFBs on a large scale.
基金supported by the National Health and Medical Research Council(NHMRC)of Australia(APP2003904-L.A.J.)NSW Cardiovascular Capacity Building Program(Early-Mid Career Researcher Grant-L.A.J.,P.Q.and Z.W.)+12 种基金MRFF Cardiovascular Health Mission Grants(MRF2016165-L.A.J.)MRF2023977-L.A.J.,and MRFF Early-to-Mid Career Researchers Grant(MRF2028865-L.A.J.)NSW Government Boosting Business Innovation Program(BBIP)International Stream(L.A.J.)National Heart Foundation Vanguard Grant(106979-L.A.J.)University of Sydney External Research Collaboration Seed Fund(L.A.J.and Z.W.)Lining Arnold Ju is a Snow Medical Research Foundation Fellow(2022SF176)a National Heart Foundation Future Leader Fellow Level 2(105863)Y.C.Z.is a NHMRC PhD Scholar(GNT2022247-Y.C.Z)a National Heart Foundation PhD Scholar(106879)National Health and Medical Research Council(Australia)Investigator Emerging Leadership 1 grant(GNT2018376)Heart foundation future leader fellowship with Paul Korner Award(106780)McCusker Charitable Foundation.
文摘Addressing the pressing demand for rapid and inexpensive coagulation testing in cardiovascular care,this study introduces a novel application of repurposed COVID-19 rapid antigen tests(RATs)as paper-based lateral flow assays(LFAs)combined with machine learning for coagulation status evaluation.By further developing a mobile app prototype,we present a platform that enables clinicians to perform immediate and accurate anticoagulant dosing adjustments using existing post-pandemic resources.Our proof-of-concept employs a random forest machine learning classifier to interpret image feature variations on RAT NC membrane,correlating red blood cell(RBC)wicked diffusion distance in recalcified citrated whole blood with changes in coagulative viscosity,easily interpreted.Enhanced by confocal imaging studies of paper microfluidics,our approach provides insights into the mechanisms dissecting coagulation components,achieving high classification precision,recall,and F1-scores.The inverse relationship between RBC wicked diffusion distance and enoxaparin concentration paves the way for machine learning to inform real-time dose prescription adjustments,aligning with individual patient profiles to optimize therapeutic outcomes.This study not only demonstrates the potential of leveraging surplus RATs for coagulation management but also exemplifies a cost-effective,rapid,and smart strategy to enhance clinical decision-making in the post-pandemic era.
