Upset condition encountered by an aircraft in flight could pose great threat to flight safety, which is of chief importance in civil aviation. The causal factors have the nonlinear and multiple characteristics, and as...Upset condition encountered by an aircraft in flight could pose great threat to flight safety, which is of chief importance in civil aviation. The causal factors have the nonlinear and multiple characteristics, and as a result the conventional envelope protection system cannot successfully do with the condition. So dynamic envelope based on differential manifold theory, which can take more coupling factors into account, is proposed as a basis to design a novel envelope protection system. Then the relationship between the dynamic envelope and the control coefficient or pilot command is obtained, and the result shows that the dynamic envelope can be enlarged with the change of control coefficient. Furthermore, quantification of flight security is realized via defining relative distance between flight state and dynamic envelope, which can detect whether there is a risk for an aircraft in flight. Finally, an envelope protection system based on dynamic envelope enlargement is proposed on the basis. NASA＇s Generic Transport Model encountering hazard gust wind in climbing phase is taken as an example to verify the system＇s feasibility. The result shows that the system can give a better operation encountering upset condition and to a certain extent reduce the number of accidents or incidents.展开更多
High-speed vehicle dynamic envelope curve is defined as the maximum limit outline affected by a variety of adverse factors while the train is running. Considering the difficulties in the current measurement system suc...High-speed vehicle dynamic envelope curve is defined as the maximum limit outline affected by a variety of adverse factors while the train is running. Considering the difficulties in the current measurement system such as complicated calibration process,cumbersome aided-instruments,strict limitation of working distance, this paper carries out an optical method in which two high-speed cameras with variable-zoom lenses are adopted as binocular stereo sensors of measurement system and a high-ac-curacy 3D target with fast reconstruction is designed. The intrinsic parameters of the sensors and the relative positions between coordinate systems are solved by the method of colinearity constrained optimization algorithm. The calibration process is easy to operate and the device is also of portability. Most importantly, the severe working distance limitation between sensors and measured body is solved, enhancing the adaptability of measurement system to environment. Experimental results show that when the sensors are in the range of 8 -16 m away from the measured body, system accuracy can reach up to ±0. 5 mm, which meets the requirements to measure the dynamic envelope curve of high-speed vehicle.展开更多
Dynamic envelope curve is a significant parameter to assess the running safety of high-speed trains.Up to now the method based on binocular stereo vision is the only way available to measure the dynamic envelope curve...Dynamic envelope curve is a significant parameter to assess the running safety of high-speed trains.Up to now the method based on binocular stereo vision is the only way available to measure the dynamic envelope curve of a train,the speed of which is over200km/h.Nevertheless the method has two limitations,one is large field-〇f-view(FO V),the other is calibration time.Hence portable calibration equipment,easy-t〇-build target and rapid calibration algorithm are required to complete the calibration.In this paper,a new rapid on-site calibration method with large FOV based on binocular stereo vision is proposed.To address these issues,a light target has been designed,the rail coordinate system(RCS)is represented by40fixed retroreflective points on the target,and they are utilized to calibrate the parameters of two cameras.In addition,two cameras merely capture a single image of the target simultaneously,and the intrinsic and extrinsic parameters of the cameras can be calculated rapidly.To testify the proposed method,the experiments have been conducted and the results reveal that the accuracy can reach+1mm,which can meet the measurement requirement.展开更多
The central concept of strategic benchmarking is resource management efficiency,which ultimately results in profitability.However,little is known about performance measurement from resource-based perspectives.This stu...The central concept of strategic benchmarking is resource management efficiency,which ultimately results in profitability.However,little is known about performance measurement from resource-based perspectives.This study uses the data envelopment analysis(DEA)model with a dynamic network structure to measure the resource management and profitability efficiencies of 287 US commercial banks from 2010 to 2020.Furthermore,we provide frontier projections and incorporate five variables,namely capital adequacy,asset quality,management quality,earning ability,and liquidity(i.e.,the CAMEL ratings).The results revealed that the room for improvement in bank performance is 55.4%.In addition,we found that the CAMEL ratings of efficient banks are generally higher than those of inefficient banks,and management quality,earnings quality,and liquidity ratios positively contribute to bank performance.Moreover,big banks are generally more efficient than small banks.Overall,this study continues the current heated debate on performance measurement in the banking industry,with a particular focus on the DEA application to answer the fundamental question of why resource management efficiency reflects benchmark firms and provides insights into how efficient management of CAMEL ratings would help in improving their performance.展开更多
A new concept is presented for air-to-air missile which is dynamic attack zone after being launched in random wind field. This new concept can be used to obtain the 4-dimensional （4-D） information regarding the dyna...A new concept is presented for air-to-air missile which is dynamic attack zone after being launched in random wind field. This new concept can be used to obtain the 4-dimensional （4-D） information regarding the dynamic envelope of an air-to-air missile at any flight time airned at different flight targets considering influences of random wind, in the situation of flight fighters coop- crated with missiles fighting against each other. Based on an air-to-air missile model, some typical cases of dynamic attack zone after being launched in random wind field were numerically simulated. Compared with the simulation results of traditional dynamic envelope, the properties of dynamic attack zone after being launched are as follows. The 4-D dynamic attack zone after being launched is inside traditional maximum dynamic envelope, but its forane boundary is usually not inside traditional no-escape dynamic envelope; Traditional dynamic attack zone can just be reliably used at launch time, while dynamic envelope after being launched can be reliably and accurately used during any flight antagonism time. Traditional envelope is a special case of dynamic envelope after being launched when the dynamic envelope is calculated at the launch time： the dynamic envelope after being launched can be inflt, enced by the random wind field.展开更多
Energy-absorbing rockbolts have been widely adopted in burst-prone excavation support, and their serviceability is closely related to the frequency and magnitude of seismic events. In this research, the splittube drop...Energy-absorbing rockbolts have been widely adopted in burst-prone excavation support, and their serviceability is closely related to the frequency and magnitude of seismic events. In this research, the splittube drop test with varying impact energy was conducted to reproduce the dynamic performance of MP1rockbolts under a wide range of seismic event magnitudes. The test results showed that the impact process could be subdivided into four distinct stages, i.e. mobilization, strain hardening, plastic flow(ductile), and rebound stage, of which strain hardening and plastic flow are the primary energy absorbing stages. As the impact energy per drop increases from 8.1 to 46.7 k J, the strain rate of the shank varies between 1.20 and 2.70 s^(-1), and the average impact load is between 240 and 270kN, which may be considered as constant. The MP1 rockbolt has a cumulative maximum energy absorption(CMEA) of 31.9–40.0 k J/m, with an average of 35.0 k J/m, and the elongation rate is 11.4%–14.7%, with an average of 12.7%, both of which are negatively correlated with the impact energy per drop. Regression analysis shows that energy absorption and shank elongation, as well as momentum input and impact duration,conform to the linear relationship. The complete dynamic capacity envelope of MP1 rockbolts is proposed, which reflects the dynamic bearing capacity, elongation, and distinct stages. This study is helpful to better understand the dynamic characteristics of energy-absorbing rockbolts and assist design engineers in robust reinforcement systems design to mitigate rockburst damage in seismically active underground excavations.展开更多
Dynamic operating envelopes(DOEs),as key enablers to facilitate distributed energy resource(DER)integration,have attracted increasing attention in the past years.However,uncertainties,which may come from load forecast...Dynamic operating envelopes(DOEs),as key enablers to facilitate distributed energy resource(DER)integration,have attracted increasing attention in the past years.However,uncertainties,which may come from load forecasting errors or inaccurate network parameters,have been rarely discussed in DOE calculation,leading to compromised quality of the hosting capacity allocation strategy.This letter studies how to calculate DOEs that are immune to such uncertainties based on a linearised unbalanced three-phase optimal power flow(UTOPF)model.With uncertain parameters constrained by norm balls,formulations for calculating robust DOEs(RDOEs)are presented along with discussions on their tractability.Two cases,including a 2-bus illustrative network and a representative Australian network,are tested to demonstrate the effectiveness and efficiency of the proposed approach.展开更多
Climate change can aff ect fi sh individuals or schools,and consequently the fi sheries.Studying future changes of fi sh distribution and abundance helps the scientifi c management of fi sheries.The dynamic bioclimate...Climate change can aff ect fi sh individuals or schools,and consequently the fi sheries.Studying future changes of fi sh distribution and abundance helps the scientifi c management of fi sheries.The dynamic bioclimate envelope model(DBEM)was used to identify the“environmental preference profi les”of the studied species based on outputs from three Earth system models(ESMs).Changes in ocean conditions in climate change scenarios could be transformed by the model into those in relative abundance and distribution of species.Therefore,the distributional response of 17 demersal fi shes to climate change in the Yellow Sea could be projected from 1970 to 2060.Indices of latitudinal centroid(LC)and mean temperature of relative abundance(MTRA)were used to represent the results conducted by model.Results present that 17 demersal fi sh species in the Yellow Sea show a trend of anti-poleward shift under both low-emission scenario(RCP 2.6)and high-emission scenario(RCP 8.5)from 1970 to 2060,with the projected average LC in three ESMs shifting at a rate of-1.17±4.55 and-2.76±3.82 km/decade,respectively,which is contrary to the previous projecting studies of fi shes suggesting that fi shes tend to move toward higher latitudes under increased temperature scenarios.The Yellow Sea Cold Water Mass could be the major driver resulting in the shift,which shows a potential signifi cance to fi shery resources management and marine conservation,and provides a new perspective in fi sh migration under climate change.展开更多
基金supported by the National Key Basic Research Program of China (No.2015CB755805)
文摘Upset condition encountered by an aircraft in flight could pose great threat to flight safety, which is of chief importance in civil aviation. The causal factors have the nonlinear and multiple characteristics, and as a result the conventional envelope protection system cannot successfully do with the condition. So dynamic envelope based on differential manifold theory, which can take more coupling factors into account, is proposed as a basis to design a novel envelope protection system. Then the relationship between the dynamic envelope and the control coefficient or pilot command is obtained, and the result shows that the dynamic envelope can be enlarged with the change of control coefficient. Furthermore, quantification of flight security is realized via defining relative distance between flight state and dynamic envelope, which can detect whether there is a risk for an aircraft in flight. Finally, an envelope protection system based on dynamic envelope enlargement is proposed on the basis. NASA＇s Generic Transport Model encountering hazard gust wind in climbing phase is taken as an example to verify the system＇s feasibility. The result shows that the system can give a better operation encountering upset condition and to a certain extent reduce the number of accidents or incidents.
基金National Science and Technology Major Project(No.2016ZX04003001)
文摘High-speed vehicle dynamic envelope curve is defined as the maximum limit outline affected by a variety of adverse factors while the train is running. Considering the difficulties in the current measurement system such as complicated calibration process,cumbersome aided-instruments,strict limitation of working distance, this paper carries out an optical method in which two high-speed cameras with variable-zoom lenses are adopted as binocular stereo sensors of measurement system and a high-ac-curacy 3D target with fast reconstruction is designed. The intrinsic parameters of the sensors and the relative positions between coordinate systems are solved by the method of colinearity constrained optimization algorithm. The calibration process is easy to operate and the device is also of portability. Most importantly, the severe working distance limitation between sensors and measured body is solved, enhancing the adaptability of measurement system to environment. Experimental results show that when the sensors are in the range of 8 -16 m away from the measured body, system accuracy can reach up to ±0. 5 mm, which meets the requirements to measure the dynamic envelope curve of high-speed vehicle.
基金National Science and Technology Major Project of China(No.2016ZX04003001)
文摘Dynamic envelope curve is a significant parameter to assess the running safety of high-speed trains.Up to now the method based on binocular stereo vision is the only way available to measure the dynamic envelope curve of a train,the speed of which is over200km/h.Nevertheless the method has two limitations,one is large field-〇f-view(FO V),the other is calibration time.Hence portable calibration equipment,easy-t〇-build target and rapid calibration algorithm are required to complete the calibration.In this paper,a new rapid on-site calibration method with large FOV based on binocular stereo vision is proposed.To address these issues,a light target has been designed,the rail coordinate system(RCS)is represented by40fixed retroreflective points on the target,and they are utilized to calibrate the parameters of two cameras.In addition,two cameras merely capture a single image of the target simultaneously,and the intrinsic and extrinsic parameters of the cameras can be calculated rapidly.To testify the proposed method,the experiments have been conducted and the results reveal that the accuracy can reach+1mm,which can meet the measurement requirement.
基金provided by Ministry of Science and Technology(Grant No.MOST 107-2410-H-034-056-MY3).
文摘The central concept of strategic benchmarking is resource management efficiency,which ultimately results in profitability.However,little is known about performance measurement from resource-based perspectives.This study uses the data envelopment analysis(DEA)model with a dynamic network structure to measure the resource management and profitability efficiencies of 287 US commercial banks from 2010 to 2020.Furthermore,we provide frontier projections and incorporate five variables,namely capital adequacy,asset quality,management quality,earning ability,and liquidity(i.e.,the CAMEL ratings).The results revealed that the room for improvement in bank performance is 55.4%.In addition,we found that the CAMEL ratings of efficient banks are generally higher than those of inefficient banks,and management quality,earnings quality,and liquidity ratios positively contribute to bank performance.Moreover,big banks are generally more efficient than small banks.Overall,this study continues the current heated debate on performance measurement in the banking industry,with a particular focus on the DEA application to answer the fundamental question of why resource management efficiency reflects benchmark firms and provides insights into how efficient management of CAMEL ratings would help in improving their performance.
文摘A new concept is presented for air-to-air missile which is dynamic attack zone after being launched in random wind field. This new concept can be used to obtain the 4-dimensional （4-D） information regarding the dynamic envelope of an air-to-air missile at any flight time airned at different flight targets considering influences of random wind, in the situation of flight fighters coop- crated with missiles fighting against each other. Based on an air-to-air missile model, some typical cases of dynamic attack zone after being launched in random wind field were numerically simulated. Compared with the simulation results of traditional dynamic envelope, the properties of dynamic attack zone after being launched are as follows. The 4-D dynamic attack zone after being launched is inside traditional maximum dynamic envelope, but its forane boundary is usually not inside traditional no-escape dynamic envelope; Traditional dynamic attack zone can just be reliably used at launch time, while dynamic envelope after being launched can be reliably and accurately used during any flight antagonism time. Traditional envelope is a special case of dynamic envelope after being launched when the dynamic envelope is calculated at the launch time： the dynamic envelope after being launched can be inflt, enced by the random wind field.
基金CCTEG Coal Mining Research Institute(No.TDKC-2022-MS-01)the National Natural Science Foundation of China(No.52274123)the Mining Education Australia(MEA),Collaborative Research Grant Scheme(No.RS-59041).
文摘Energy-absorbing rockbolts have been widely adopted in burst-prone excavation support, and their serviceability is closely related to the frequency and magnitude of seismic events. In this research, the splittube drop test with varying impact energy was conducted to reproduce the dynamic performance of MP1rockbolts under a wide range of seismic event magnitudes. The test results showed that the impact process could be subdivided into four distinct stages, i.e. mobilization, strain hardening, plastic flow(ductile), and rebound stage, of which strain hardening and plastic flow are the primary energy absorbing stages. As the impact energy per drop increases from 8.1 to 46.7 k J, the strain rate of the shank varies between 1.20 and 2.70 s^(-1), and the average impact load is between 240 and 270kN, which may be considered as constant. The MP1 rockbolt has a cumulative maximum energy absorption(CMEA) of 31.9–40.0 k J/m, with an average of 35.0 k J/m, and the elongation rate is 11.4%–14.7%, with an average of 12.7%, both of which are negatively correlated with the impact energy per drop. Regression analysis shows that energy absorption and shank elongation, as well as momentum input and impact duration,conform to the linear relationship. The complete dynamic capacity envelope of MP1 rockbolts is proposed, which reflects the dynamic bearing capacity, elongation, and distinct stages. This study is helpful to better understand the dynamic characteristics of energy-absorbing rockbolts and assist design engineers in robust reinforcement systems design to mitigate rockburst damage in seismically active underground excavations.
基金supported by the CSIRO Strategic Project on Network Optimisation&Decarbonisation(No.OD-107890).
文摘Dynamic operating envelopes(DOEs),as key enablers to facilitate distributed energy resource(DER)integration,have attracted increasing attention in the past years.However,uncertainties,which may come from load forecasting errors or inaccurate network parameters,have been rarely discussed in DOE calculation,leading to compromised quality of the hosting capacity allocation strategy.This letter studies how to calculate DOEs that are immune to such uncertainties based on a linearised unbalanced three-phase optimal power flow(UTOPF)model.With uncertain parameters constrained by norm balls,formulations for calculating robust DOEs(RDOEs)are presented along with discussions on their tractability.Two cases,including a 2-bus illustrative network and a representative Australian network,are tested to demonstrate the effectiveness and efficiency of the proposed approach.
基金Supported by the National Natural Science Foundation of China(No.42176234)the Chinese Arctic and Antarctic Creative Program(No.JDXT2018-01)the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0402)。
文摘Climate change can aff ect fi sh individuals or schools,and consequently the fi sheries.Studying future changes of fi sh distribution and abundance helps the scientifi c management of fi sheries.The dynamic bioclimate envelope model(DBEM)was used to identify the“environmental preference profi les”of the studied species based on outputs from three Earth system models(ESMs).Changes in ocean conditions in climate change scenarios could be transformed by the model into those in relative abundance and distribution of species.Therefore,the distributional response of 17 demersal fi shes to climate change in the Yellow Sea could be projected from 1970 to 2060.Indices of latitudinal centroid(LC)and mean temperature of relative abundance(MTRA)were used to represent the results conducted by model.Results present that 17 demersal fi sh species in the Yellow Sea show a trend of anti-poleward shift under both low-emission scenario(RCP 2.6)and high-emission scenario(RCP 8.5)from 1970 to 2060,with the projected average LC in three ESMs shifting at a rate of-1.17±4.55 and-2.76±3.82 km/decade,respectively,which is contrary to the previous projecting studies of fi shes suggesting that fi shes tend to move toward higher latitudes under increased temperature scenarios.The Yellow Sea Cold Water Mass could be the major driver resulting in the shift,which shows a potential signifi cance to fi shery resources management and marine conservation,and provides a new perspective in fi sh migration under climate change.
