The identification of key nodes plays an important role in improving the robustness of the transportation network.For different types of transportation networks,the effect of the same identification method may be diff...The identification of key nodes plays an important role in improving the robustness of the transportation network.For different types of transportation networks,the effect of the same identification method may be different.It is of practical significance to study the key nodes identification methods corresponding to various types of transportation networks.Based on the knowledge of complex networks,the metro networks and the bus networks are selected as the objects,and the key nodes are identified by the node degree identification method,the neighbor node degree identification method,the weighted k-shell degree neighborhood identification method(KSD),the degree k-shell identification method(DKS),and the degree k-shell neighborhood identification method(DKSN).Take the network efficiency and the largest connected subgraph as the effective indicators.The results show that the KSD identification method that comprehensively considers the elements has the best recognition effect and has certain practical significance.展开更多
The single-line-to-ground faults with line breaks(SLGFs-LBs)occur more and more frequently in distribution networks and can cause major safety accidents.It is difficult to distinguish the single-line-to-ground faults(...The single-line-to-ground faults with line breaks(SLGFs-LBs)occur more and more frequently in distribution networks and can cause major safety accidents.It is difficult to distinguish the single-line-to-ground faults(SLGFs)in resonant grounding systems and ungrounding systems due to the same electrical characteristics on the source side and uncertain operation conditions of distribution networks.This paper proposes a method for distinguishing SLGFs-LBs and SLGFs.First,the source-side and load-side voltage characteristics of SLGFs and SLGFs-LBs are analyzed,and the phase difference between the voltages of the fault phase and non-fault phase on the load side is selected as the identification criterion.Phasor measurement units(PMUs)are selected as measuring devices.Then,the effects of operation conditions and external devices in distribution networks on the proposed method are discussed,and the phase errors caused by them are calculated to correct the identification method.Finally,the field testing and simulation experiments are conducted to verify the effectiveness and robustness of the proposed method.展开更多
The pre-gate suction vortex,gate-bottom-edge transverse vortex,gate-slot vertical vortex,and downstream-of-gate return vortex are important factors affecting the flow instability of flat gates,which may lead to fatigu...The pre-gate suction vortex,gate-bottom-edge transverse vortex,gate-slot vertical vortex,and downstream-of-gate return vortex are important factors affecting the flow instability of flat gates,which may lead to fatigue failure in severe cases.This study used the volume of fluid(VOF)model and large eddy simulation(LES)method to accurately capture the transient turbulence characteristics of flow under different water flow conditions and reveal the flow field and vortex structure.The Q—criterion,Omega(Ω)method,and latest third-generation Liutex vortex identification method were used to analyze and compare the pre-gate suction vortex,gate-slot vertical vortex,and downstream-of-gate return vortex,focusing on the ability of each vortex identification method to capture the flow field information and vortex characteristics.The results reveal that theΩmethod and Liutex method are less dependent on the threshold value,and the Liutex method captures a wide range of pre-gate vortices.Different flow conditions cause changes in the vortex structure of over-gate flow.When the relative opening of the gate is smaller,the intensity of the vortices in the flow field around the gate is greater,the return vortices downstream of the gate are more disordered,and the vortex changes are more violent,which in turn affects the efficient and stable operation of the gate.展开更多
This study aimed to investigate the task demand of intelligent unmanned fertilizer application in seedling stage of corn planted in full-film double-ditch seedbed,a film identification method based on improved DeepLab...This study aimed to investigate the task demand of intelligent unmanned fertilizer application in seedling stage of corn planted in full-film double-ditch seedbed,a film identification method based on improved DeepLabv3+ identification method for full-film double-ditch corn seedbed was proposed.The differences in performance indicators of the original Deeplabv3+ network taking Xception as the backbone network and the network model that replaced three lightweight backbone networks,MobileNetV2,MobileNetV3 and GhostNet were tested.At the same time,the network models,classical semantic segmentation was introduced to PSPNet and UNet for comparative test.The MIoU of DeepLabv3+ network model that replaced its backbone network increased by 5.01%,and FPS improved by 206%compared with original network,and the model size reduced by 90.3%.The three DeepLabv3+ models after replacing the backbone network were further compressed,and the two-layer expansion convolution with low expansion rate in ASPP was deleted,and the common convolution after feature fusion was replaced by the depthwise separable convolution to obtain a lightweight network model.After testing the improved network model,it was found that the average decline of precision indicators was only 0.17%,FPS raised to 66.5,with an average increase of 25.5%,and the size of the model was compressed to 10.53 MB.Test results showed that,the improved model showed excellent performance,and could provide important technology and method support for the research and development of intelligent topdressing and field management on full-film double-ditch corn seedbed during seedling stage.展开更多
Precise states estimation for the lithium-ion battery is one of the fundamental tasks in the battery management system(BMS),where building an accurate battery model is the first step in model-based estimation algorith...Precise states estimation for the lithium-ion battery is one of the fundamental tasks in the battery management system(BMS),where building an accurate battery model is the first step in model-based estimation algorithms.To date,although the comparative studies on different battery models have been performed intensively,little attention is paid to the comparison among different online parameters identification methods regarding model accuracy,robustness ability,adaptability to the different battery operating conditions and computation cost.In this paper,based on the Thevenin model,the three most widely used online parameters identification methods,including extended Kalman filter(EKF),particle swarm optimization(PSO),and recursive least square(RLS),are evaluated comprehensively under static and dynamic tests.It is worth noting that,although the built model’s terminal voltage may well follow a measured curve,these identified model parameters may significantly out of reasonable range,which means that the error between measured and predicted terminal voltage cannot be seen as a gist to determine which model is the most accurate.To evaluate model accuracy more rigorously,battery state-of-charge(SOC)is further estimated based on identified model parameters under static and dynamic tests.The SOC prediction results show that EKF and RLS algorithms are more suitable to be used for online model parameters identification under static and dynamic tests,respectively.Moreover,the random offset is added into originally measured data to verify the robustness ability of different methods,whose results indicate EKF and RLS have more satisfactory ability against imprecisely sampled data under static and dynamic tests,respectively.Considering model accuracy,robustness ability,adaptability to the different battery operating conditions and computation cost simultaneously,EKF is recommended to be adopted to establish battery model in real application among these three most widely used methods.展开更多
Considered as the building blocks,vortex structures with variety of sizes and intensity are widely recognized in the viscous flow field around ship.In this paper,the computational fluid dynamics(CFD)solver,naoe-FOAM-S...Considered as the building blocks,vortex structures with variety of sizes and intensity are widely recognized in the viscous flow field around ship.In this paper,the computational fluid dynamics(CFD)solver,naoe-FOAM-SJTU,coupled with delayed detached-eddy simulation(DDES)is adopted to analyze the vortex structures around the benchmark model Yupeng Ship in dynamic pure yaw tests,which are captured by third generation of vortex identification method.The good agreement of the predicted force/moment by DDES method with the experimental data indicates that the present numerical schemes are reliable and robust.Three vortex identification methods,Q-criteria,Ω_(R) and Liutex,are used to capture the vortex structures around the hull.The large separated flow is able to be investigated by these three methods,in which more vortex structures are captured byΩ_(R) approach and Liutex method with scalar,vector and tensor form seems to be more suitable for analyzing the flow mechanism around the hull in dynamic pure yaw test.In general,each vortex structure corresponds to a dominant positive/negative axial Liutex and a bound vortex pair.The streamlines are spiral in the large separated flow,indicating that the flow in corresponding region is rotational.But the rotation of the flow is not directly related to the intensity of Liutex.展开更多
Urban functional area(UFA)is a core scientific issue affecting urban sustainability.The current knowledge gap is mainly reflected in the lack of multi-scale quantitative interpretation methods from the perspective of ...Urban functional area(UFA)is a core scientific issue affecting urban sustainability.The current knowledge gap is mainly reflected in the lack of multi-scale quantitative interpretation methods from the perspective of human-land interaction.In this paper,based on multi-source big data include 250 m×250 m resolution cell phone data,1.81×105 Points of Interest(POI)data and administrative boundary data,we built a UFA identification method and demonstrated empirically in Shenyang City,China.We argue that the method we built can effectively identify multi-scale multi-type UFAs based on human activity and further reveal the spatial correlation between urban facilities and human activity.The empirical study suggests that the employment functional zones in Shenyang City are more concentrated in central cities than other single functional zones.There are more mix functional areas in the central city areas,while the planned industrial new cities need to develop comprehensive functions in Shenyang.UFAs have scale effects and human-land interaction patterns.We suggest that city decision makers should apply multi-sources big data to measure urban functional service in a more refined manner from a supply-demand perspective.展开更多
For correct identification of vortices,this paper first analyzes the properties of the rigid vortex core and its induced flow field given by the Rankine vortex model,and it is concluded that the concentrated vortex st...For correct identification of vortices,this paper first analyzes the properties of the rigid vortex core and its induced flow field given by the Rankine vortex model,and it is concluded that the concentrated vortex structure should consist of the vortex core and the induced flow field(the potential flow region with a weak shear layer).Then the vortex structure is analyzed by using the Oseen vortex model.Compared with the Rankine vortex,the Oseen vortex is a concentrated vortex with a deformed vortex core.The vortex structure consists of the vortex core region,the transition region and the shear layer region(or the potential flow region).The transition region reflects the properties of the resultant vorticity of the same magnitude and the resultant deformation rate of the shear layer,and the transition region also determines the boundary of the vortex core.Finally,the evolution of leading-edge vortices of the double-delta wing is numerically simulated.And with different vortex identification methods,the shape and the properties of the leading-edge vortices identified by each method are analyzed and compared.It is found that in the vorticity concentration region,the vortices obtained by using ω,λ2,Ω criteria and Q criteria are basically identical when appropriate threshold values are adopted.However,in the region where the vorticity is dispersed,due to the influence of the flow viscous effect and the adverse pressure gradient,the results obtained by different vortex identification methods can be quite different,as well as the related physical properties,which need to be further studied.展开更多
To investigate to what extent economic policy uncertainty affects China’s macroeconomic fluctuations,we construct a mixed identification scheme that combines some regular sign restrictions with zero restriction in a ...To investigate to what extent economic policy uncertainty affects China’s macroeconomic fluctuations,we construct a mixed identification scheme that combines some regular sign restrictions with zero restriction in a SVAR model,aiming to simultaneously identify economic policy uncertainty shocks and the three conventional structural shocks of demand,supply and monetary policy.The research shows that(1)economic policy uncertainty shocks,though not the major factor for economic fluctuations in China,exhibit characteristics similar to those of negative demand shocks with inflation effect obviously stronger than output effect;(2)in the full sample period,demand shocks are the primary driving factor for China’s economic fluctuations,followed by supply shocks;(3)supply shocks are the most important driving force behind inflation and monetary policy adds fuel to the flame,while economic policy uncertainty shocks exert obvious inhibition on inflation.The academic contribution of this paper is showing some robust empirical facts of economic policy uncertainty’s effects on macroeconomic fluctuations from the biggest developing country,and the policy implication of our research is to provide academic support for the decision of“macroeconomic policies should remain stable”.展开更多
Landslides,collapses and cracks are the main types of geological hazards,which threaten the safety of human life and property at all times.In emergency surveying and mapping,it is timeconsuming and laborious to use th...Landslides,collapses and cracks are the main types of geological hazards,which threaten the safety of human life and property at all times.In emergency surveying and mapping,it is timeconsuming and laborious to use the method of field artificial investigation and recognition and using satellite image to identify ground hazards,there are some problems,such as time lag,low resolution,and difficult to select the map on demand.In this paper,a10 cm per pixel resolution photogrammetry of a geological hazard-prone area of Taohuagou,Shanxi Province,China is carried out by DJ 4 UAV.The digital orthophoto model(DOM),digital surface model(DSM) and three-dimensional point cloud model(3 DPCM) are generated in this region.The method of visual interpretation of cracks based on DOM(as main)-3 DPCM(as auxiliary) and landslide and collapse based on 3 DPCM(as main)-DOM and DSM(as auxiliary) are proposed.Based on the low altitude remote sensing image of UAV,the shape characteristics,geological characteristics and distribution of the identified hazards are analyzed.The results show that using UAV low altitude remote sensing image,the method of combination of main and auxiliary data can quickly and accurately identify landslide,collapse and crack,the accuracy of crack identification is 93%,and the accuracy of landslide and collapse identification is 100%.It mainly occurs in silty clay and mudstone geology and is greatly affected by slope foot excavation.This study can play a great role in the recognition of sudden hazards by low altitude remote sensing images of UAV.展开更多
The Internet of Things (IOT) is a recent technology originating from the field of sensor networks. It has received significant attention because it is involved in most aspects of our daily lives. The IOT vision makes ...The Internet of Things (IOT) is a recent technology originating from the field of sensor networks. It has received significant attention because it is involved in most aspects of our daily lives. The IOT vision makes objects of various kinds become part of the Internet by assigning each object a unique identifier, enabling objects to communicate with each other in the same or different environments. IOT can collect, process, and exchange data via a data communication network. There are many methods for identifying objects;some have existed since the beginning of IOT innovation, such as Radio Frequency Identification (RFID), Barcode/2D code, IP address, Electronic Product Codes (EPC), etc. Continuous development in IOT domain and the large number of objects connected to the Internet daily require an improved identification method to cope with the rapid development in this field. Many modern methods have been proposed recently, based on various technologies such as computer vision, fingerprinting, and machine learning. This paper introduces an overview of IOT and discusses its fundamental elements;it mainly focuses on identification of IOT which is considered the main part that the IOT systems rely on. The paper discusses the existing identification methods for IOT. Moreover, it provides a review of the modern identification methods proposed in recent literature.展开更多
With the continuous improvement of automation,industrial robots have become an indispensable part of automated production lines.They widely used in a number of industrial production activities,such as spraying,welding...With the continuous improvement of automation,industrial robots have become an indispensable part of automated production lines.They widely used in a number of industrial production activities,such as spraying,welding,handling,etc.,and have a great role in these sectors.Recently,the robotic technology is developing towards high precision,high intelligence.Robot calibration technology has a great significance to improve the accuracy of robot.However,it has much work to be done in the identification of robot parameters.The parameter identification work of existing serial and parallel robots is introduced.On the one hand,it summarizes the methods for parameter calibration and discusses their advantages and disadvantages.On the other hand,the application of parameter identification is introduced.This overview has a great reference value for robot manufacturers to choose proper identification method,points further research areas for researchers.Finally,this paper analyzes the existing problems in robot calibration,which may be worth researching in the future.展开更多
Time moments have been introduced in automatic control because of the analogy between the impulse response of a linear system and a probability function. Pasek described a testing procedure for determining the DC para...Time moments have been introduced in automatic control because of the analogy between the impulse response of a linear system and a probability function. Pasek described a testing procedure for determining the DC parameters from the current response to a step in the armature voltage motor. In this paper, two identification algorithms developed based on the moments and Pasek's methods are introduced and applied to the parameter identification of a DC motor. The simulation and experimental results are presented and compared, showing that the moments method makes the model closer to reality, especially in a transient regime.展开更多
In order to deepen the understanding of the spatial change images of upper mantle media for strain strength and polarization direction, anisotropy and shear wave splitting, anisotropy and strain, strain and the tecton...In order to deepen the understanding of the spatial change images of upper mantle media for strain strength and polarization direction, anisotropy and shear wave splitting, anisotropy and strain, strain and the tectonic process, based on the theory on the characteristics of shear wave splitting parameters in the presence of two weak azimuthal anisotropic layers and observations concerned, and using signal identification methods with high precision, the results for 136 earthquakes are obtained. The pictures of anisotropy strength and polarization direction beneath twenty stations are got. Combining the results existed previously, the characteristics and origin of the upper mantle anisotropy are discussed.展开更多
Software vulnerabilities pose significant risks to computer systems,impacting our daily lives,productivity,and even our health.Identifying and addressing security vulnerabilities in a timely manner is crucial to preve...Software vulnerabilities pose significant risks to computer systems,impacting our daily lives,productivity,and even our health.Identifying and addressing security vulnerabilities in a timely manner is crucial to prevent hacking and data breaches.Unfortunately,current vulnerability identification methods,including classical and deep learning-based approaches,exhibit critical drawbacks that prevent them from meeting the demands of the contemporary software industry.To tackle these issues,we present JFinder,a novel architecture for Java vulnerability identification that leverages quad self-attention and pre-training mechanisms to combine structural information and semantic representations.Experimental results demonstrate that JFinder outperforms all baseline methods,achieving an accuracy of 0.97 on the CWE dataset and an F1 score of 0.84 on the PROMISE dataset.Furthermore,a case study reveals that JFinder can accurately identify four cases of vulnerabilities after patching.展开更多
Rice is the main grain crop in China. With global warming, drought and water shortage have become one of the important factors limiting rice production. Improving the drought resistance of rice can effectively allevia...Rice is the main grain crop in China. With global warming, drought and water shortage have become one of the important factors limiting rice production. Improving the drought resistance of rice can effectively alleviate the loss of rice yield caused by drought. In this paper, the research progress on rice drought resistance and its evaluation methods, mapping of QTLs for drought resistance-related traits, and mining for drought resistance genes were reviewed, and molecular breeding for drought resistance in rice was prospected.展开更多
The spatiotemporal evolution of hairpin vortex structures in a fully developed turbulent boundary layer is investigated qualitatively and quantitatively by using two image methods.In this paper,the moving single-frame...The spatiotemporal evolution of hairpin vortex structures in a fully developed turbulent boundary layer is investigated qualitatively and quantitatively by using two image methods.In this paper,the moving single-frame and long-exposure(MSFLE)image method is used to intuitively track the evolution process of a hairpin vortex,while the moving particle image velocimetry(moving-PIV)method is applied for obtaining a moving velocity field for quantitative analysis.According to the structural characteristics of the hairpin vortex,an inclined light sheet with an appropriate inclination of 53°is arranged to capture the complete hairpin vortex structure at Re_(θ)=97–194.In addition,the core size and the rotational strength of a hairpin vortex are further defined and quantified by the Liutex vector method.The evolution process of a complete hairpin vortex structure observed by MSFLE shows that the shear along the normal direction leads to an increasing strength of the hairpin vortex,accompanied by a lifting vortex head and a distance decrease between two vortex legs during the dissipation period.By combining moving-PIV with the Liutex identification,the spatiotemporal evolution of four typical regions of a hairpin vortex projecting into a 53°cross-section is obtained.The results show that the process from the generation to the dissipation of a single hairpin vortex can be well characterized and recorded by the Liutex based on the core size and rotational intensity,and the evolution process is consistent with the MSFLE result.According to the statistics of vortex core size and rotation intensity along time,the evolution of the hairpin vortex necks and legs can be described as a process of enhancement followed by dissipation.For the vortex head,its evolution maintains longer attributed to its far-from-wall position,which consists of an absolute enhancement process(stage 1)with an increasing rotation strength and a constant core size,and an absolute dissipation(stage 2)with a decreasing rotation strength and a constant core size.展开更多
A parameter estimation method based on an improved Whale Optimization Algorithm is proposed in this paper to identify the parameters of a static var compensator(SVC)model.First,a mathematical model of SVC is establish...A parameter estimation method based on an improved Whale Optimization Algorithm is proposed in this paper to identify the parameters of a static var compensator(SVC)model.First,a mathematical model of SVC is established.Then,the reverse learning strategy and Levy flight disturbance strategy are introduced to improve the whale optimization algorithm,and the improved whale optimization algorithm is applied to the parameter identification of the static var compensator model.Finally,a stepwise identification method,by analyzing the local sensitivities of parameters,is proposed which solves the problem of low accuracy caused by multi-parameter identification.This method provides a new estimation strategy for accurately identifying the parameters of the static var compensator model.Estimation results show that the parameter estimation method can be an effective tool to solve the problem of parameter identification for the SVC model.展开更多
Fishway research is important for mitigating the fragmentation of river habitats caused by hydraulic projects.The vertical slit fishway is a broadly used fishway type because of its high efficiency and adaptability to...Fishway research is important for mitigating the fragmentation of river habitats caused by hydraulic projects.The vertical slit fishway is a broadly used fishway type because of its high efficiency and adaptability to water levels.However,the resulting vortex current disrupts the fish passage hence directly affecting fish migration.This study aims to accurately capture the vortex structure in the fishway and analyze the effect of vortex elements(vortex structure,vortex intensity,etc.)on fish.We conducted an analysis of the 3-D current flow field in the fishway through the utilization of an experimental model and the large eddy simulation(LES)method.Moreover,we captured the vortex information in the fishway at different flow rates using the Liutex vortex identification method and investigated the effect of the vortex on fish migration.The results revealed that the structures inside the fishway pool occupy most of the room,however,the areas with higher vortex strength were primarily located in the vortex near the vertical seam and the mainstream,the vortex strength inside the fishway gradually increases with increasing flow,suppressing fish migration.Fish experienced significantly increased resistance when encountering strong vortices.This suggests that the vortex may act as a physical barrier to fish migration.These findings highlight the potential negative effects of vortex on fish movement and reiterate the importance of understanding vortex dynamics for aquatic environmental management.As an effective tool for identifying vortices in fluid flow,the Liutex method demonstrates features of vortex within the fishway,thereby providing important insights into the interaction between fluid dynamics and aquatic organisms.展开更多
Congestion is an economic phenomenon of overinvestment that occurs when excessive inputs decrease the maximally possible outputs.Although decision-makers are unlikely to decrease outputs by increasing inputs,congestio...Congestion is an economic phenomenon of overinvestment that occurs when excessive inputs decrease the maximally possible outputs.Although decision-makers are unlikely to decrease outputs by increasing inputs,congestion is widespread in reality.Identifying and measuring congestion can help decision-makers detect the problem of overinvestment.This paper reviews the development of the concept of congestion in the framework of data envelopment analysis(DEA),which is a widely accepted method for identifying and measuring congestion.In this paper,six main congestion identification and measurement methods are analysed through several numerical examples.We investigate the ideas of these methods,the contributions compared with the previous methods,and the existing shortcomings.Based on our analysis,we conclude that existing congestion identification and measurement methods are still inadequate.Three problems are anticipated for further study:maintaining the consistency between congestion and overinvestment,considering joint weak disposability assumption between desirable outputs and undesirable outputs,and quantifying the degree of congestion.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.61961019)the Youth Key Project of the Natural Science Foundation of Jiangxi Province of China(Grant No.20202ACBL212003).
文摘The identification of key nodes plays an important role in improving the robustness of the transportation network.For different types of transportation networks,the effect of the same identification method may be different.It is of practical significance to study the key nodes identification methods corresponding to various types of transportation networks.Based on the knowledge of complex networks,the metro networks and the bus networks are selected as the objects,and the key nodes are identified by the node degree identification method,the neighbor node degree identification method,the weighted k-shell degree neighborhood identification method(KSD),the degree k-shell identification method(DKS),and the degree k-shell neighborhood identification method(DKSN).Take the network efficiency and the largest connected subgraph as the effective indicators.The results show that the KSD identification method that comprehensively considers the elements has the best recognition effect and has certain practical significance.
基金supported in part by National Science Foundation of China(No.51707117)。
文摘The single-line-to-ground faults with line breaks(SLGFs-LBs)occur more and more frequently in distribution networks and can cause major safety accidents.It is difficult to distinguish the single-line-to-ground faults(SLGFs)in resonant grounding systems and ungrounding systems due to the same electrical characteristics on the source side and uncertain operation conditions of distribution networks.This paper proposes a method for distinguishing SLGFs-LBs and SLGFs.First,the source-side and load-side voltage characteristics of SLGFs and SLGFs-LBs are analyzed,and the phase difference between the voltages of the fault phase and non-fault phase on the load side is selected as the identification criterion.Phasor measurement units(PMUs)are selected as measuring devices.Then,the effects of operation conditions and external devices in distribution networks on the proposed method are discussed,and the phase errors caused by them are calculated to correct the identification method.Finally,the field testing and simulation experiments are conducted to verify the effectiveness and robustness of the proposed method.
基金supported by the National Natural Science Foundation of China(Grant Nos.52069009,51369013).
文摘The pre-gate suction vortex,gate-bottom-edge transverse vortex,gate-slot vertical vortex,and downstream-of-gate return vortex are important factors affecting the flow instability of flat gates,which may lead to fatigue failure in severe cases.This study used the volume of fluid(VOF)model and large eddy simulation(LES)method to accurately capture the transient turbulence characteristics of flow under different water flow conditions and reveal the flow field and vortex structure.The Q—criterion,Omega(Ω)method,and latest third-generation Liutex vortex identification method were used to analyze and compare the pre-gate suction vortex,gate-slot vertical vortex,and downstream-of-gate return vortex,focusing on the ability of each vortex identification method to capture the flow field information and vortex characteristics.The results reveal that theΩmethod and Liutex method are less dependent on the threshold value,and the Liutex method captures a wide range of pre-gate vortices.Different flow conditions cause changes in the vortex structure of over-gate flow.When the relative opening of the gate is smaller,the intensity of the vortices in the flow field around the gate is greater,the return vortices downstream of the gate are more disordered,and the vortex changes are more violent,which in turn affects the efficient and stable operation of the gate.
基金supported by the National Natural Science Foundation of China(Grant No.5206500552365029)Outstanding Youth Foundation of Gansu Province(Grant No.20JR10RA560),China Postdoctoral Science Foundation(Grant No.2021M700741).
文摘This study aimed to investigate the task demand of intelligent unmanned fertilizer application in seedling stage of corn planted in full-film double-ditch seedbed,a film identification method based on improved DeepLabv3+ identification method for full-film double-ditch corn seedbed was proposed.The differences in performance indicators of the original Deeplabv3+ network taking Xception as the backbone network and the network model that replaced three lightweight backbone networks,MobileNetV2,MobileNetV3 and GhostNet were tested.At the same time,the network models,classical semantic segmentation was introduced to PSPNet and UNet for comparative test.The MIoU of DeepLabv3+ network model that replaced its backbone network increased by 5.01%,and FPS improved by 206%compared with original network,and the model size reduced by 90.3%.The three DeepLabv3+ models after replacing the backbone network were further compressed,and the two-layer expansion convolution with low expansion rate in ASPP was deleted,and the common convolution after feature fusion was replaced by the depthwise separable convolution to obtain a lightweight network model.After testing the improved network model,it was found that the average decline of precision indicators was only 0.17%,FPS raised to 66.5,with an average increase of 25.5%,and the size of the model was compressed to 10.53 MB.Test results showed that,the improved model showed excellent performance,and could provide important technology and method support for the research and development of intelligent topdressing and field management on full-film double-ditch corn seedbed during seedling stage.
基金supported by the State Grid Company Science and Technology Project(Grant No.5230HQ19000J).
文摘Precise states estimation for the lithium-ion battery is one of the fundamental tasks in the battery management system(BMS),where building an accurate battery model is the first step in model-based estimation algorithms.To date,although the comparative studies on different battery models have been performed intensively,little attention is paid to the comparison among different online parameters identification methods regarding model accuracy,robustness ability,adaptability to the different battery operating conditions and computation cost.In this paper,based on the Thevenin model,the three most widely used online parameters identification methods,including extended Kalman filter(EKF),particle swarm optimization(PSO),and recursive least square(RLS),are evaluated comprehensively under static and dynamic tests.It is worth noting that,although the built model’s terminal voltage may well follow a measured curve,these identified model parameters may significantly out of reasonable range,which means that the error between measured and predicted terminal voltage cannot be seen as a gist to determine which model is the most accurate.To evaluate model accuracy more rigorously,battery state-of-charge(SOC)is further estimated based on identified model parameters under static and dynamic tests.The SOC prediction results show that EKF and RLS algorithms are more suitable to be used for online model parameters identification under static and dynamic tests,respectively.Moreover,the random offset is added into originally measured data to verify the robustness ability of different methods,whose results indicate EKF and RLS have more satisfactory ability against imprecisely sampled data under static and dynamic tests,respectively.Considering model accuracy,robustness ability,adaptability to the different battery operating conditions and computation cost simultaneously,EKF is recommended to be adopted to establish battery model in real application among these three most widely used methods.
基金supported by the National Natural Science Foundation of China(Grant Nos.51909160,51879159,52131102)the National Key Research and Development Program of China(Grant No.2019YFB1704200).
文摘Considered as the building blocks,vortex structures with variety of sizes and intensity are widely recognized in the viscous flow field around ship.In this paper,the computational fluid dynamics(CFD)solver,naoe-FOAM-SJTU,coupled with delayed detached-eddy simulation(DDES)is adopted to analyze the vortex structures around the benchmark model Yupeng Ship in dynamic pure yaw tests,which are captured by third generation of vortex identification method.The good agreement of the predicted force/moment by DDES method with the experimental data indicates that the present numerical schemes are reliable and robust.Three vortex identification methods,Q-criteria,Ω_(R) and Liutex,are used to capture the vortex structures around the hull.The large separated flow is able to be investigated by these three methods,in which more vortex structures are captured byΩ_(R) approach and Liutex method with scalar,vector and tensor form seems to be more suitable for analyzing the flow mechanism around the hull in dynamic pure yaw test.In general,each vortex structure corresponds to a dominant positive/negative axial Liutex and a bound vortex pair.The streamlines are spiral in the large separated flow,indicating that the flow in corresponding region is rotational.But the rotation of the flow is not directly related to the intensity of Liutex.
基金Under the auspices of Natural Science Foundation of China(No.41971166)。
文摘Urban functional area(UFA)is a core scientific issue affecting urban sustainability.The current knowledge gap is mainly reflected in the lack of multi-scale quantitative interpretation methods from the perspective of human-land interaction.In this paper,based on multi-source big data include 250 m×250 m resolution cell phone data,1.81×105 Points of Interest(POI)data and administrative boundary data,we built a UFA identification method and demonstrated empirically in Shenyang City,China.We argue that the method we built can effectively identify multi-scale multi-type UFAs based on human activity and further reveal the spatial correlation between urban facilities and human activity.The empirical study suggests that the employment functional zones in Shenyang City are more concentrated in central cities than other single functional zones.There are more mix functional areas in the central city areas,while the planned industrial new cities need to develop comprehensive functions in Shenyang.UFAs have scale effects and human-land interaction patterns.We suggest that city decision makers should apply multi-sources big data to measure urban functional service in a more refined manner from a supply-demand perspective.
基金supported by the National Natural Science Foundation of China(Grant No.11772033).
文摘For correct identification of vortices,this paper first analyzes the properties of the rigid vortex core and its induced flow field given by the Rankine vortex model,and it is concluded that the concentrated vortex structure should consist of the vortex core and the induced flow field(the potential flow region with a weak shear layer).Then the vortex structure is analyzed by using the Oseen vortex model.Compared with the Rankine vortex,the Oseen vortex is a concentrated vortex with a deformed vortex core.The vortex structure consists of the vortex core region,the transition region and the shear layer region(or the potential flow region).The transition region reflects the properties of the resultant vorticity of the same magnitude and the resultant deformation rate of the shear layer,and the transition region also determines the boundary of the vortex core.Finally,the evolution of leading-edge vortices of the double-delta wing is numerically simulated.And with different vortex identification methods,the shape and the properties of the leading-edge vortices identified by each method are analyzed and compared.It is found that in the vorticity concentration region,the vortices obtained by using ω,λ2,Ω criteria and Q criteria are basically identical when appropriate threshold values are adopted.However,in the region where the vorticity is dispersed,due to the influence of the flow viscous effect and the adverse pressure gradient,the results obtained by different vortex identification methods can be quite different,as well as the related physical properties,which need to be further studied.
文摘To investigate to what extent economic policy uncertainty affects China’s macroeconomic fluctuations,we construct a mixed identification scheme that combines some regular sign restrictions with zero restriction in a SVAR model,aiming to simultaneously identify economic policy uncertainty shocks and the three conventional structural shocks of demand,supply and monetary policy.The research shows that(1)economic policy uncertainty shocks,though not the major factor for economic fluctuations in China,exhibit characteristics similar to those of negative demand shocks with inflation effect obviously stronger than output effect;(2)in the full sample period,demand shocks are the primary driving factor for China’s economic fluctuations,followed by supply shocks;(3)supply shocks are the most important driving force behind inflation and monetary policy adds fuel to the flame,while economic policy uncertainty shocks exert obvious inhibition on inflation.The academic contribution of this paper is showing some robust empirical facts of economic policy uncertainty’s effects on macroeconomic fluctuations from the biggest developing country,and the policy implication of our research is to provide academic support for the decision of“macroeconomic policies should remain stable”.
基金supported by the National Natural Science Foundation of China (Award Number: 51704205)Key R & D Plan projects in Shanxi Province of China (Award Number: 201803D31044)+1 种基金Education Department Natural Science Foundation in Guizhou of China (Award Number: KY (2017) 097)the High-Level Talents Fund of Guizhou University of Engineering Science (Award Number: G2015005)。
文摘Landslides,collapses and cracks are the main types of geological hazards,which threaten the safety of human life and property at all times.In emergency surveying and mapping,it is timeconsuming and laborious to use the method of field artificial investigation and recognition and using satellite image to identify ground hazards,there are some problems,such as time lag,low resolution,and difficult to select the map on demand.In this paper,a10 cm per pixel resolution photogrammetry of a geological hazard-prone area of Taohuagou,Shanxi Province,China is carried out by DJ 4 UAV.The digital orthophoto model(DOM),digital surface model(DSM) and three-dimensional point cloud model(3 DPCM) are generated in this region.The method of visual interpretation of cracks based on DOM(as main)-3 DPCM(as auxiliary) and landslide and collapse based on 3 DPCM(as main)-DOM and DSM(as auxiliary) are proposed.Based on the low altitude remote sensing image of UAV,the shape characteristics,geological characteristics and distribution of the identified hazards are analyzed.The results show that using UAV low altitude remote sensing image,the method of combination of main and auxiliary data can quickly and accurately identify landslide,collapse and crack,the accuracy of crack identification is 93%,and the accuracy of landslide and collapse identification is 100%.It mainly occurs in silty clay and mudstone geology and is greatly affected by slope foot excavation.This study can play a great role in the recognition of sudden hazards by low altitude remote sensing images of UAV.
文摘The Internet of Things (IOT) is a recent technology originating from the field of sensor networks. It has received significant attention because it is involved in most aspects of our daily lives. The IOT vision makes objects of various kinds become part of the Internet by assigning each object a unique identifier, enabling objects to communicate with each other in the same or different environments. IOT can collect, process, and exchange data via a data communication network. There are many methods for identifying objects;some have existed since the beginning of IOT innovation, such as Radio Frequency Identification (RFID), Barcode/2D code, IP address, Electronic Product Codes (EPC), etc. Continuous development in IOT domain and the large number of objects connected to the Internet daily require an improved identification method to cope with the rapid development in this field. Many modern methods have been proposed recently, based on various technologies such as computer vision, fingerprinting, and machine learning. This paper introduces an overview of IOT and discusses its fundamental elements;it mainly focuses on identification of IOT which is considered the main part that the IOT systems rely on. The paper discusses the existing identification methods for IOT. Moreover, it provides a review of the modern identification methods proposed in recent literature.
基金supported in part by the National Natural Science Foundation of China(61772493)in part by the Guangdong Province Universities and College Pearl River Scholar Funded Scheme(2019)in part by the Natural Science Foundation of Chongqing(cstc2019jcyjjq X0013)。
文摘With the continuous improvement of automation,industrial robots have become an indispensable part of automated production lines.They widely used in a number of industrial production activities,such as spraying,welding,handling,etc.,and have a great role in these sectors.Recently,the robotic technology is developing towards high precision,high intelligence.Robot calibration technology has a great significance to improve the accuracy of robot.However,it has much work to be done in the identification of robot parameters.The parameter identification work of existing serial and parallel robots is introduced.On the one hand,it summarizes the methods for parameter calibration and discusses their advantages and disadvantages.On the other hand,the application of parameter identification is introduced.This overview has a great reference value for robot manufacturers to choose proper identification method,points further research areas for researchers.Finally,this paper analyzes the existing problems in robot calibration,which may be worth researching in the future.
文摘Time moments have been introduced in automatic control because of the analogy between the impulse response of a linear system and a probability function. Pasek described a testing procedure for determining the DC parameters from the current response to a step in the armature voltage motor. In this paper, two identification algorithms developed based on the moments and Pasek's methods are introduced and applied to the parameter identification of a DC motor. The simulation and experimental results are presented and compared, showing that the moments method makes the model closer to reality, especially in a transient regime.
基金State Natural Science Foundation of China (49734150) the Chinese Joint Seismological Science Foundation (198061).
文摘In order to deepen the understanding of the spatial change images of upper mantle media for strain strength and polarization direction, anisotropy and shear wave splitting, anisotropy and strain, strain and the tectonic process, based on the theory on the characteristics of shear wave splitting parameters in the presence of two weak azimuthal anisotropic layers and observations concerned, and using signal identification methods with high precision, the results for 136 earthquakes are obtained. The pictures of anisotropy strength and polarization direction beneath twenty stations are got. Combining the results existed previously, the characteristics and origin of the upper mantle anisotropy are discussed.
基金supported by the National Key R&D Program of China(2019YFB2102600)the National Natural Science Foundation of China(62002067)+1 种基金the Guangzhou Youth Talent of Science(QT20220101174)the Project of Philosophy and Social Science Planning of GuangDong(GD21YGL16).
文摘Software vulnerabilities pose significant risks to computer systems,impacting our daily lives,productivity,and even our health.Identifying and addressing security vulnerabilities in a timely manner is crucial to prevent hacking and data breaches.Unfortunately,current vulnerability identification methods,including classical and deep learning-based approaches,exhibit critical drawbacks that prevent them from meeting the demands of the contemporary software industry.To tackle these issues,we present JFinder,a novel architecture for Java vulnerability identification that leverages quad self-attention and pre-training mechanisms to combine structural information and semantic representations.Experimental results demonstrate that JFinder outperforms all baseline methods,achieving an accuracy of 0.97 on the CWE dataset and an F1 score of 0.84 on the PROMISE dataset.Furthermore,a case study reveals that JFinder can accurately identify four cases of vulnerabilities after patching.
基金Supported by Natural Science Foundation of Anhui Province (1908085MC93)Major Science and Technology Project of Anhui Province (2021d06050002)Anhui Province Joint Research on Improved Crop Varieties (Rice)。
文摘Rice is the main grain crop in China. With global warming, drought and water shortage have become one of the important factors limiting rice production. Improving the drought resistance of rice can effectively alleviate the loss of rice yield caused by drought. In this paper, the research progress on rice drought resistance and its evaluation methods, mapping of QTLs for drought resistance-related traits, and mining for drought resistance genes were reviewed, and molecular breeding for drought resistance in rice was prospected.
基金Projects supported by the National Natural Science Foundation of China(Grant No.51906154)the National Science and Technology Major Project(Grant No.2017-V-0016-0069)the Natural Science Foundation of Shanghai(Grant No.21ZR1443700).
文摘The spatiotemporal evolution of hairpin vortex structures in a fully developed turbulent boundary layer is investigated qualitatively and quantitatively by using two image methods.In this paper,the moving single-frame and long-exposure(MSFLE)image method is used to intuitively track the evolution process of a hairpin vortex,while the moving particle image velocimetry(moving-PIV)method is applied for obtaining a moving velocity field for quantitative analysis.According to the structural characteristics of the hairpin vortex,an inclined light sheet with an appropriate inclination of 53°is arranged to capture the complete hairpin vortex structure at Re_(θ)=97–194.In addition,the core size and the rotational strength of a hairpin vortex are further defined and quantified by the Liutex vector method.The evolution process of a complete hairpin vortex structure observed by MSFLE shows that the shear along the normal direction leads to an increasing strength of the hairpin vortex,accompanied by a lifting vortex head and a distance decrease between two vortex legs during the dissipation period.By combining moving-PIV with the Liutex identification,the spatiotemporal evolution of four typical regions of a hairpin vortex projecting into a 53°cross-section is obtained.The results show that the process from the generation to the dissipation of a single hairpin vortex can be well characterized and recorded by the Liutex based on the core size and rotational intensity,and the evolution process is consistent with the MSFLE result.According to the statistics of vortex core size and rotation intensity along time,the evolution of the hairpin vortex necks and legs can be described as a process of enhancement followed by dissipation.For the vortex head,its evolution maintains longer attributed to its far-from-wall position,which consists of an absolute enhancement process(stage 1)with an increasing rotation strength and a constant core size,and an absolute dissipation(stage 2)with a decreasing rotation strength and a constant core size.
文摘A parameter estimation method based on an improved Whale Optimization Algorithm is proposed in this paper to identify the parameters of a static var compensator(SVC)model.First,a mathematical model of SVC is established.Then,the reverse learning strategy and Levy flight disturbance strategy are introduced to improve the whale optimization algorithm,and the improved whale optimization algorithm is applied to the parameter identification of the static var compensator model.Finally,a stepwise identification method,by analyzing the local sensitivities of parameters,is proposed which solves the problem of low accuracy caused by multi-parameter identification.This method provides a new estimation strategy for accurately identifying the parameters of the static var compensator model.Estimation results show that the parameter estimation method can be an effective tool to solve the problem of parameter identification for the SVC model.
基金supported by the National Natural Science Foundation of China(Grant Nos.52069009,51369013).
文摘Fishway research is important for mitigating the fragmentation of river habitats caused by hydraulic projects.The vertical slit fishway is a broadly used fishway type because of its high efficiency and adaptability to water levels.However,the resulting vortex current disrupts the fish passage hence directly affecting fish migration.This study aims to accurately capture the vortex structure in the fishway and analyze the effect of vortex elements(vortex structure,vortex intensity,etc.)on fish.We conducted an analysis of the 3-D current flow field in the fishway through the utilization of an experimental model and the large eddy simulation(LES)method.Moreover,we captured the vortex information in the fishway at different flow rates using the Liutex vortex identification method and investigated the effect of the vortex on fish migration.The results revealed that the structures inside the fishway pool occupy most of the room,however,the areas with higher vortex strength were primarily located in the vortex near the vertical seam and the mainstream,the vortex strength inside the fishway gradually increases with increasing flow,suppressing fish migration.Fish experienced significantly increased resistance when encountering strong vortices.This suggests that the vortex may act as a physical barrier to fish migration.These findings highlight the potential negative effects of vortex on fish movement and reiterate the importance of understanding vortex dynamics for aquatic environmental management.As an effective tool for identifying vortices in fluid flow,the Liutex method demonstrates features of vortex within the fishway,thereby providing important insights into the interaction between fluid dynamics and aquatic organisms.
基金the support from National Natural Science Foundation of China(No.71671181,72071196).
文摘Congestion is an economic phenomenon of overinvestment that occurs when excessive inputs decrease the maximally possible outputs.Although decision-makers are unlikely to decrease outputs by increasing inputs,congestion is widespread in reality.Identifying and measuring congestion can help decision-makers detect the problem of overinvestment.This paper reviews the development of the concept of congestion in the framework of data envelopment analysis(DEA),which is a widely accepted method for identifying and measuring congestion.In this paper,six main congestion identification and measurement methods are analysed through several numerical examples.We investigate the ideas of these methods,the contributions compared with the previous methods,and the existing shortcomings.Based on our analysis,we conclude that existing congestion identification and measurement methods are still inadequate.Three problems are anticipated for further study:maintaining the consistency between congestion and overinvestment,considering joint weak disposability assumption between desirable outputs and undesirable outputs,and quantifying the degree of congestion.
