After the last flight of the Concorde in 2003,sonic boom has been one of the obstacles to the return of a supersonic transport aircraft to service.To reduce the sonic boom intensity to an acceptable level,it is of gre...After the last flight of the Concorde in 2003,sonic boom has been one of the obstacles to the return of a supersonic transport aircraft to service.To reduce the sonic boom intensity to an acceptable level,it is of great significance to study the effect of lift distribution on far-field sonic boom,since lift is one of the most important contributors to an intense sonic boom.Existing studies on the longitudinal lift distribution used low-fidelity methods,such as Whitham theory,and in turn,only preliminary conclusions were obtained,such as that extending the lift distribution can reduce sonic boom.This paper uses a newly developed high-fidelity prediction method to quantitatively study the effect of longitudinal lift distribution on the sonic boom of a Canard-Wing-Stabilator-Body(CWSB)configuration.This high-fidelity prediction method combines near-feld CFD simulation with far-field propagation by solving the augmented Burgers equation.A multipole analysis method is employed for the extraction of near-field waveform in order to reduce computational cost.Seven configurations with the same total lift but different distributions are studied,and the quantitative relationship between the longitudinal lift distribution and far-field sonic boom intensity is investigated.It is observed that a small lift generated by the stabilator can prevent aft-stabilator and aft-fuselage shocks from merging,while the balanced lift generated by the canard and wing can effectively keep the corresponding shocks further apart,which is beneficial for reducing both the on-track and off-track sonic boom.In turn,the acoustic level perceived at the ground can be reduced by 5.9 PLdB on-track and 5.4 PLdB off-track,on average.展开更多
Geographic visualization is essential for explaining and describing spatiotemporal geographical processes in flow fields.However,due to multi-scale structures and irregular spatial distribution of vortices in complex ...Geographic visualization is essential for explaining and describing spatiotemporal geographical processes in flow fields.However,due to multi-scale structures and irregular spatial distribution of vortices in complex geographic flow fields,existing two-dimensional visualization methods are susceptible to the effects of data accuracy and sampling resolution,resulting in incomplete and inaccurate vortex information.To address this,we propose an adaptive Line Integral Convolution(LIC)based geographic flow field visualization method by means of rotation distance.Our novel framework of rotation distance and its quantification allows for the effective identification and extraction of vortex features in flow fields effectively.We then improve the LIC algorithm using rotation distance by constructing high-frequency noise from it as input to the convolution,with the integration step size adjusted.This approach allows us to effectively distinguish between vortex and non-vortex fields and adaptively represent the details of vortex features in complex geographic flow fields.Our experimental results show that the proposed method leads to more accurate and effective visualization of the geographic flow fields.展开更多
Dynamic flood disaster simulation is an emerging and promising technology significantly useful in urban planning,risk assessment,and integrated decision support systems.It is still an important issue to integrate the ...Dynamic flood disaster simulation is an emerging and promising technology significantly useful in urban planning,risk assessment,and integrated decision support systems.It is still an important issue to integrate the large assets such as dynamic observational data,numerical flood simulation models,geographic information technologies,and computing resources into a unified framework.For the intended end user,it is also a holistic solution to create computer interpretable representations and gain insightful understanding of the dynamic disaster processes,the complex impacts,and interactions of disaster factors.In particular,it is still difficult to access and join harmonized data,processing algorithms,and models that are provided by different environmental information infrastructures.In this paper,we demonstrate a virtual geographic environments-based integrated environmental simulation framework for flood disaster management based on the notion of interlinked resources,which is capable of automated accumulating and manipulating of sensor data,creating dynamic geo-analysis and three-dimensional visualizations of ongoing geo-process,and updating the contents of simulation models representing the real environment.The prototype system is evaluated by applying it as a proof of concept to integrate in situ weather observations,numerical weather and flood disaster simulation models,visualization,and analysis of the real time flood event.Case applications indicate that the developed framework can be adopted for use by decision-makers for short-term planning and control since the resulting simulation and visualization are completely based on the latest status of environment.展开更多
The Chinese Government and citizens face enormous challenges of disaster management as widespread devastation,economic damages,and loss of human lives caused by increasing natural disasters.Disaster management require...The Chinese Government and citizens face enormous challenges of disaster management as widespread devastation,economic damages,and loss of human lives caused by increasing natural disasters.Disaster management requires a complicated iterative process that includes disaster monitoring,early detection,forecasting,loss assessment,and efficient analysis of disaster reduction.Each task typically involves the use of technologists and multiple geospatial information resources,including sensors,data sources,models,geo-tools,software packages,and computing resources.However,most existing disaster management systems operate in a typical passive data-centric mode,where resources cannot be fully utilized.This impediment is partially being addressed by the increasingly complex application requirements and the growing availability of diverse resources.In this paper,we summarize and analyze the practical problems experienced by the National Disaster Reduction Application System of China.To address the issues of data-centric,centralized,isolated solutions,we propose a novel Focusing Service Mechanism,which is capable of scheduling and allocating for optimum utilization of multiple resources,to dynamically generate collaborative and on-demand disaster information services.We also demonstrate the design and implementation of the Integrated Disaster Information Service System(IDISS).Through the service strategies of Virtualizing,Wrapping,and Integrating,disasterrelated resources are constructed into services in the IDISS.These services are dynamically aggregated into focusing service chains,for diverse disaster management tasks.Actual applications illustrate that the proposed service system can significantly improve the capability of disaster management in China.展开更多
The real-time accurate description of all spatial features of railway and their spatiotemporal relationships is a crucial factor in realizing comprehensive management and related decision-making within the entire life...The real-time accurate description of all spatial features of railway and their spatiotemporal relationships is a crucial factor in realizing comprehensive management and related decision-making within the entire life cycle of railways.Nevertheless,available spatiotemporal data models mainly use static historical sequence data,which are insufficient to support multi-source heterogeneous real-time sensed data;they lack a systematic depiction of the interactive relationships among multiple feature entities,and are limited to low-level descriptive analysis.Therefore,this study proposes a data-model-knowledge integrated representation data model for a digital twin railway,which explicitly describes the spatiotemporal,and interaction relationships among railway features through a conceptual knowledge graph.This study first analyzes the characteristics of railway features from above ground to underground,and then constructs a conceptual model to clearly describe the complex relationships among railway features.Secondly,a logical model is developed to illustrate the basic data structure.Thirdly,an ontology model is constructed as a basic framework for further deepening the domain knowledge graph.Finally,considering the prevention of landslides as an example,it demonstrates the abundant spatiotemporal relationships among railway related features.The results of this study bring more clear understanding of the complex interactive relationships of railway entities.展开更多
The unified management and planning of national or provincial natural resources distributed both aboveground and underground have become increasingly important.Accurate depictions of natural resource elements and thei...The unified management and planning of national or provincial natural resources distributed both aboveground and underground have become increasingly important.Accurate depictions of natural resource elements and their interactions are key to achieving integrated and systematic management of natural resources.However,current spatiotemporal data models are based only on data descriptions,attribute records,and other model knowledge of a more general basis,without intuitively describing relationships between these elements and natural resources.This paper,therefore,proposes an integrated data-model-knowledge representation model to explicitly describe the time,space,and interaction of natural resource entities through an integrated knowledge graph.First,this study constructs a conceptual model using the aspects of semantics,scale,and data-model-knowledge,thereby explicitly describing the relationships of natural resources.Second,a logical model of natural resource representation is proposed,that is integrated with time,space,attributes,and relationships.Finally,taking the management of water resources as an example,this paper realizes the meticulous presentation of the levels of detail and rich semantic relations of natural resource entities.The findings of this study lay the foundation for a more efficient,precise,and lucid perception of the distribution laws and complicated interactional relationships of natural resources,both aboveground and underground.展开更多
Global change refers to changes in the relationship between humans and nature.It is desirable to actively integrate human social activities into the unified framework of global change so that their mutual relations an...Global change refers to changes in the relationship between humans and nature.It is desirable to actively integrate human social activities into the unified framework of global change so that their mutual relations and functional mechanisms can be understood.This complicated issue necessitates an appropriate method allowing domain experts to collaboratively contribute their knowledge to geoscientific research.Also,an efficient approach to optimize experimentation is of great importance.The reproducibility of research methods and results needs to be improved to boost the sharing of geographic knowledge and resources.This paper proposes a versioned geoscientific workflow and characterizes its full lifecycle using Virtual Geographic Environments,intending to facilitate and improve research related to the interactions between global change and human activities.The geoscientific workflow management is realized using the concept of version management,making geographic simulation methods and computational results easily reproducible and extendable.The sharing and reuse of geographic knowledge in various forms are archived through version management of geoscientific workflows.A versatile prototype system is implemented which enables the visual modeling of geoscientific workflows,the interactive optimization and collaborative evaluation of geoscientific workflows at runtime,the multi-dimensional dynamic visualization of geo-workflow outputs,and role-based access control for data security.展开更多
基金sponsored by the National Natural Science Foundation of China(Nos.12072285,U20B2007)the Shaanxi Science Fund for Distinguished Young Scholars,China(No.2020JC-13)the Natural Science Funding of Shaanxi Province,China(No.2020JM-127).
文摘After the last flight of the Concorde in 2003,sonic boom has been one of the obstacles to the return of a supersonic transport aircraft to service.To reduce the sonic boom intensity to an acceptable level,it is of great significance to study the effect of lift distribution on far-field sonic boom,since lift is one of the most important contributors to an intense sonic boom.Existing studies on the longitudinal lift distribution used low-fidelity methods,such as Whitham theory,and in turn,only preliminary conclusions were obtained,such as that extending the lift distribution can reduce sonic boom.This paper uses a newly developed high-fidelity prediction method to quantitatively study the effect of longitudinal lift distribution on the sonic boom of a Canard-Wing-Stabilator-Body(CWSB)configuration.This high-fidelity prediction method combines near-feld CFD simulation with far-field propagation by solving the augmented Burgers equation.A multipole analysis method is employed for the extraction of near-field waveform in order to reduce computational cost.Seven configurations with the same total lift but different distributions are studied,and the quantitative relationship between the longitudinal lift distribution and far-field sonic boom intensity is investigated.It is observed that a small lift generated by the stabilator can prevent aft-stabilator and aft-fuselage shocks from merging,while the balanced lift generated by the canard and wing can effectively keep the corresponding shocks further apart,which is beneficial for reducing both the on-track and off-track sonic boom.In turn,the acoustic level perceived at the ground can be reduced by 5.9 PLdB on-track and 5.4 PLdB off-track,on average.
文摘Geographic visualization is essential for explaining and describing spatiotemporal geographical processes in flow fields.However,due to multi-scale structures and irregular spatial distribution of vortices in complex geographic flow fields,existing two-dimensional visualization methods are susceptible to the effects of data accuracy and sampling resolution,resulting in incomplete and inaccurate vortex information.To address this,we propose an adaptive Line Integral Convolution(LIC)based geographic flow field visualization method by means of rotation distance.Our novel framework of rotation distance and its quantification allows for the effective identification and extraction of vortex features in flow fields effectively.We then improve the LIC algorithm using rotation distance by constructing high-frequency noise from it as input to the convolution,with the integration step size adjusted.This approach allows us to effectively distinguish between vortex and non-vortex fields and adaptively represent the details of vortex features in complex geographic flow fields.Our experimental results show that the proposed method leads to more accurate and effective visualization of the geographic flow fields.
基金This study is supported by the National High Technology Research and Development Program of China(863 Program)(Nos.2012AA121305 and 2013AA120701)the National Natural Science Foundation of China(Nos.41471320 and 41201440).
文摘Dynamic flood disaster simulation is an emerging and promising technology significantly useful in urban planning,risk assessment,and integrated decision support systems.It is still an important issue to integrate the large assets such as dynamic observational data,numerical flood simulation models,geographic information technologies,and computing resources into a unified framework.For the intended end user,it is also a holistic solution to create computer interpretable representations and gain insightful understanding of the dynamic disaster processes,the complex impacts,and interactions of disaster factors.In particular,it is still difficult to access and join harmonized data,processing algorithms,and models that are provided by different environmental information infrastructures.In this paper,we demonstrate a virtual geographic environments-based integrated environmental simulation framework for flood disaster management based on the notion of interlinked resources,which is capable of automated accumulating and manipulating of sensor data,creating dynamic geo-analysis and three-dimensional visualizations of ongoing geo-process,and updating the contents of simulation models representing the real environment.The prototype system is evaluated by applying it as a proof of concept to integrate in situ weather observations,numerical weather and flood disaster simulation models,visualization,and analysis of the real time flood event.Case applications indicate that the developed framework can be adopted for use by decision-makers for short-term planning and control since the resulting simulation and visualization are completely based on the latest status of environment.
基金This study was supported by the National Science and Technology Support Program of China[863 Program,grant number 03-Y30B06-9001-13/15,grant number 2012AA121305]the National Natural Science Foundation[grant number 41171311,grant number 41101354,grant number 41201440].
文摘The Chinese Government and citizens face enormous challenges of disaster management as widespread devastation,economic damages,and loss of human lives caused by increasing natural disasters.Disaster management requires a complicated iterative process that includes disaster monitoring,early detection,forecasting,loss assessment,and efficient analysis of disaster reduction.Each task typically involves the use of technologists and multiple geospatial information resources,including sensors,data sources,models,geo-tools,software packages,and computing resources.However,most existing disaster management systems operate in a typical passive data-centric mode,where resources cannot be fully utilized.This impediment is partially being addressed by the increasingly complex application requirements and the growing availability of diverse resources.In this paper,we summarize and analyze the practical problems experienced by the National Disaster Reduction Application System of China.To address the issues of data-centric,centralized,isolated solutions,we propose a novel Focusing Service Mechanism,which is capable of scheduling and allocating for optimum utilization of multiple resources,to dynamically generate collaborative and on-demand disaster information services.We also demonstrate the design and implementation of the Integrated Disaster Information Service System(IDISS).Through the service strategies of Virtualizing,Wrapping,and Integrating,disasterrelated resources are constructed into services in the IDISS.These services are dynamically aggregated into focusing service chains,for diverse disaster management tasks.Actual applications illustrate that the proposed service system can significantly improve the capability of disaster management in China.
基金supported by the Project of the National Natural Science Foundation of China under Grant Number 41941019supported by the Open Fund of Key Laboratory of Urban Land Resources Monitoring and Simulation,Ministry of Natural Resources under Grant Number KF-2021-06-033.
文摘The real-time accurate description of all spatial features of railway and their spatiotemporal relationships is a crucial factor in realizing comprehensive management and related decision-making within the entire life cycle of railways.Nevertheless,available spatiotemporal data models mainly use static historical sequence data,which are insufficient to support multi-source heterogeneous real-time sensed data;they lack a systematic depiction of the interactive relationships among multiple feature entities,and are limited to low-level descriptive analysis.Therefore,this study proposes a data-model-knowledge integrated representation data model for a digital twin railway,which explicitly describes the spatiotemporal,and interaction relationships among railway features through a conceptual knowledge graph.This study first analyzes the characteristics of railway features from above ground to underground,and then constructs a conceptual model to clearly describe the complex relationships among railway features.Secondly,a logical model is developed to illustrate the basic data structure.Thirdly,an ontology model is constructed as a basic framework for further deepening the domain knowledge graph.Finally,considering the prevention of landslides as an example,it demonstrates the abundant spatiotemporal relationships among railway related features.The results of this study bring more clear understanding of the complex interactive relationships of railway entities.
基金supported by the National Natural Science Foundation of China[Projects No.41871314,4187010232]the Program of the Department of Natural Resources of Sichuan Province[Grant Number KJ20206].
文摘The unified management and planning of national or provincial natural resources distributed both aboveground and underground have become increasingly important.Accurate depictions of natural resource elements and their interactions are key to achieving integrated and systematic management of natural resources.However,current spatiotemporal data models are based only on data descriptions,attribute records,and other model knowledge of a more general basis,without intuitively describing relationships between these elements and natural resources.This paper,therefore,proposes an integrated data-model-knowledge representation model to explicitly describe the time,space,and interaction of natural resource entities through an integrated knowledge graph.First,this study constructs a conceptual model using the aspects of semantics,scale,and data-model-knowledge,thereby explicitly describing the relationships of natural resources.Second,a logical model of natural resource representation is proposed,that is integrated with time,space,attributes,and relationships.Finally,taking the management of water resources as an example,this paper realizes the meticulous presentation of the levels of detail and rich semantic relations of natural resource entities.The findings of this study lay the foundation for a more efficient,precise,and lucid perception of the distribution laws and complicated interactional relationships of natural resources,both aboveground and underground.
基金supported by National Natural Science Foundation of China:[Grant Number U1811464,41971278,41671378]National Key Basic Research Program of China:[Grant Number 2015CB954103].
文摘Global change refers to changes in the relationship between humans and nature.It is desirable to actively integrate human social activities into the unified framework of global change so that their mutual relations and functional mechanisms can be understood.This complicated issue necessitates an appropriate method allowing domain experts to collaboratively contribute their knowledge to geoscientific research.Also,an efficient approach to optimize experimentation is of great importance.The reproducibility of research methods and results needs to be improved to boost the sharing of geographic knowledge and resources.This paper proposes a versioned geoscientific workflow and characterizes its full lifecycle using Virtual Geographic Environments,intending to facilitate and improve research related to the interactions between global change and human activities.The geoscientific workflow management is realized using the concept of version management,making geographic simulation methods and computational results easily reproducible and extendable.The sharing and reuse of geographic knowledge in various forms are archived through version management of geoscientific workflows.A versatile prototype system is implemented which enables the visual modeling of geoscientific workflows,the interactive optimization and collaborative evaluation of geoscientific workflows at runtime,the multi-dimensional dynamic visualization of geo-workflow outputs,and role-based access control for data security.
