The path planning problem of complex wild environment with multiple elements still poses challenges.This paper designs an algorithm that integrates global and local planning to apply to the wild environmental path pla...The path planning problem of complex wild environment with multiple elements still poses challenges.This paper designs an algorithm that integrates global and local planning to apply to the wild environmental path planning.The modeling process of wild environment map is designed.Three optimization strategies are designed to improve the A-Star in overcoming the problems of touching the edge of obstacles,redundant nodes and twisting paths.A new weighted cost function is designed to achieve different planning modes.Furthermore,the improved dynamic window approach(DWA)is designed to avoid local optimality and improve time efficiency compared to traditional DWA.For the necessary path re-planning of wild environment,the improved A-Star is integrated with the improved DWA to solve re-planning problem of unknown and moving obstacles in wild environment with multiple elements.The improved fusion algorithm effectively solves problems and consumes less time,and the simulation results verify the effectiveness of improved algorithms above.展开更多
Based on the wave attack task planning method in static complex environment and the rolling optimization framework, an online task planning method in dynamic complex environment based on rolling optimization is propos...Based on the wave attack task planning method in static complex environment and the rolling optimization framework, an online task planning method in dynamic complex environment based on rolling optimization is proposed. In the process of online task planning in dynamic complex environment,online task planning is based on event triggering including target information update event, new target addition event, target failure event, weapon failure event, etc., and the methods include defense area reanalysis, parameter space update, and mission re-planning. Simulation is conducted for different events and the result shows that the index value of the attack scenario after re-planning is better than that before re-planning and according to the probability distribution of statistical simulation method, the index value distribution after re-planning is obviously in the region of high index value, and the index value gap before and after re-planning is related to the degree of posture change.展开更多
Purpose: To improve the accuracy in megavoltage photon beam dose calculation in CBCT-based radiation treatment (RT) plans, using a kilovoltage cone-beam computed tomography (CBCT)-to-density-step (CBCT-SF) function. M...Purpose: To improve the accuracy in megavoltage photon beam dose calculation in CBCT-based radiation treatment (RT) plans, using a kilovoltage cone-beam computed tomography (CBCT)-to-density-step (CBCT-SF) function. Materials and Methods: The CBCT-SF table is constructed from differential histograms of the voxel values of CBCT and Fan-beam CT (FBCT). From the CBCT histograms, frequency peaks representing air, lung, soft tissue and bone are observed and their widths in CT numbers are assigned to the lower and higher bounds of the steps in the CBCT-SF. The CBCT-SF is entered into a planning system as an alternative to the clinical CT-to-density table. The CT image sets studied in this work consist of FBCT and CBCT scans of three patients: a prostate cancer patient, a lung cancer patient and a head and neck patient;and of a humanoid phantom at sections of the pelvis, the thorax and the head. Deformable image registration is used to map the patient FBCT scans to the corresponding CBCT images to minimize anatomical variations. Three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) plans are made on the FBCT image sets of the patients and the phantom. The plans are recalculated on the CBCT scans using both the conventional CT-to-density table and the CBCT-SF. Dose calculations on the CBCT images and FBCT images are compared using dose differences, distance to agreement (DTA), Gamma analyses and dose volume histogram (DVH) analyses. Results: The results show that IMRT plans optimized using CBCT scans and FBCT scans agree dosimetrically within 1% when the CBCT-SF is used for the CBCT-based plans, including thoracic IMRT plan. In contrast, up to 5% dose difference is observed between IMRT plans optimized on FBCT scans and CBCT scans for thoracic cases if conventional CT-to-density table is used on CBCT images. Conclusions: The simple stepwise mapping of the CBCT numbers to density using the CBCT-SF resolves the inaccuracies in dose calculations previously reported in CBCT-based RT plans. CBCT-SF can be used in Image-Guided adaptive radiotherapy planning.展开更多
Rapidly developing cities are under continuous physical and social changes which make sustainable urban growth concept a matured line of thinking. They are therefore, in need of restructuring to contain these changes....Rapidly developing cities are under continuous physical and social changes which make sustainable urban growth concept a matured line of thinking. They are therefore, in need of restructuring to contain these changes. Likewise, Khartoum is growing rapidly and is subjected to continual transformation. It started in Independence Day （1/1/1956） by 〈3% of Sudan population and reached 16.8% in 2010 while its physical block grew beyond imagination. The objective of this paper is to throw light on Khartoum rapid growth change effects which necessitated implementation of a revolutionary restructuring programme. At first, huge rural influxes were absorbed and later physical distortions were corrected. This included squatter settlements＇ treatment to strengthen urban fabric, reallocation of incompatible urban functions, revitalization of the CBD （central business district） and other urban renewal schemes. Transportation lines were extended to ease people mobility and higher population concentrations were diluted, particularly the filthy slums. Old neighbourhoods, traditional villages, etc. were re-planned and popular physical development was encouraged. The restructuring programme appropriated population distribution, administrative districts, new local markets＇ locations and urban activities＇ distribution. The programme attained social benefits, particularly availing shelter and essential social services. Difficulties from relocation processes were encountered but settlements＇ regularization achieved social justice and sustained urban growth.展开更多
Advanced countries around the world are spurring the development of Unmanned Surface Vehicles (USVs) that can operate autonomously at marine environment. The key enabling technology for such USVs is the mission planni...Advanced countries around the world are spurring the development of Unmanned Surface Vehicles (USVs) that can operate autonomously at marine environment. The key enabling technology for such USVs is the mission planning system (MPS) that can autonomously navigate through the harsh waters. The MPS not only has the functions for the navigation, but also has the capabilities, such as obstacle avoidance, malfunction corrections, dealing with unexpected events, return home functions, and many other eventualities that cannot be programmed in advance. The autonomy levels are increasingly moving higher and it is foreseeable that the trend will continue in the future. The main purpose of this paper is the analysis of the MPS onboard the USVs, in terms of the categories, functions, and technological details. Also, we analyze the case study of autonomous mission planning control systems in various fields and introduce the features that constitute the critical functionalities of the mission planning systems.展开更多
A growing interest in developing autonomous surface vehicles(ASVs)has been witnessed during the past two decades,including COLREGs-compliant navigation to ensure safe autonomy of ASVs operating in complex waterways.Th...A growing interest in developing autonomous surface vehicles(ASVs)has been witnessed during the past two decades,including COLREGs-compliant navigation to ensure safe autonomy of ASVs operating in complex waterways.This paper reviews the recent progress in COLREGs-compliant navigation of ASVs from traditional to learning-based approaches.It features a holistic viewpoint of ASV safe navigation,namely from collision detection to decision making and then to path replanning.The existing methods in all these three stages are classified according to various criteria.An in-time overview of the recently-developed learning-based methods in motion prediction and path replanning is provided,with a discussion on ASV navigation scenarios and tasks where learning-based methods may be needed.Finally,more general challenges and future directions of ASV navigation are highlighted.展开更多
Excess phosphorus(P)in water can lead to eutrophication and upset ecological balance.In this study,biochar with ultrathin two-dimensional nanosheets from the natural mesocarp of shaddock was chosen as the carrier.The ...Excess phosphorus(P)in water can lead to eutrophication and upset ecological balance.In this study,biochar with ultrathin two-dimensional nanosheets from the natural mesocarp of shaddock was chosen as the carrier.The highly dispersed and small particle size of La(OH)_(3) on the surface of the nanosheets(MSBL3)was successfully achieved using chemical impregnation for the adsorption of P in aqueous solution,and the maximum adsorption capacity was 260.0 mg P g^(−1)[La].The differences in surface crystallization of La(OH)_(3) on biochar at different La loadings were analyzed using the high-precision characterization methods.After six adsorption-desorption cycles,MSBL3 retained 76.7%of its initial performance in terms of the P adsorption capacity.The preparation of 1 g of MSBL3 costs about RMB 1,and it could reduce the P concentration in 2.6 ton of Laoyu River water to below the eutrophication threshold;and the inhibitory effect of MSBL3 on the eutrophication of water bodies was confirmed by the growth state of water hyacinth.Furthermore,0.1 M MSBL3 could inhibit Escherichia coli and Staphylococcus aureus up to 98.7%and 85.0%,respectively,which indicates that MSBL3 can be used to recover P from water and also to improve water quality.In addition,the growth of the maize seedlings verified that the P-absorbed MSBL3 waste is a good soil fertilizer and can solve the problem of post-treatment of the adsorbent.In conclusion,MSBL3 prepared in this study is a promising P sorbent for application.展开更多
Mobile robots have been used for many industrial scenarios which can realize automated manufacturing process instead of human workers. To improve the quality of the optimal rapidly-exploring random tree(RRT^(*)) for p...Mobile robots have been used for many industrial scenarios which can realize automated manufacturing process instead of human workers. To improve the quality of the optimal rapidly-exploring random tree(RRT^(*)) for planning path in dynamic environment, a high-quality dynamic rapidly-exploring random tree(HQD-RRT^(*)) algorithm is proposed in this paper, which generates a high-quality solution with optimal path length in dynamic environment. This method proceeds in two stages: initial path generation and path re-planning. Firstly, the initial path is generated by an improved smart rapidly-exploring random tree(RRT^(*)-SMART) algorithm, and the state tree information is stored as prior knowledge. During the process of path execution, a strategy of obstacle avoidance is proposed to avoid moving obstacles. The cost and smoothness of path are considered to re-plan the initial path to improve the path quality in this strategy. Compared with related work, a higher-quality path in dynamic environment can be achieved in this paper. HQD-RRT^(*) algorithm can obtain an optimal path with better stability. Simulations on the static and dynamic environment are conducted to clarify the efficiency of HQD-RRT^(*) in avoiding unknown obstacles.展开更多
Effective urban land-use re-planning and the strategic arrangement of drainage pipe networks can significantly enhance urban flood defense capacity.Aimed at reducing the potential risks of urban flooding,this paper pr...Effective urban land-use re-planning and the strategic arrangement of drainage pipe networks can significantly enhance urban flood defense capacity.Aimed at reducing the potential risks of urban flooding,this paper presents a straightforward and efficient approach to an urban distributed runoff model(UDRM).The model is developed to quantify the discharge and water depth within urban drainage pipe networks under varying rainfall intensities and land-use scenarios.The Nash efficiency coefficient of UDRM exceeds 0.9,which indicates its high computational efficiency and potential benefit in predicting urban flooding.The prediction of drainage conditions under both current and re-planned land-use types is achieved by adopting different flood recurrence intervals.The findings reveal that the re-planned land-use strategies could effectively diminish flood risk upstream of the drainage pipe network across 20-year and 50-year flood recurrence intervals.However,in the case of extreme rainfall events(a 100-year flood recurrence),the re-planned land-use approach fell short of fulfilling the requirements necessary for flood disaster mitigation.In these instances,the adoption of larger-diameter drainage pipes becomes an essential requisite to satisfy drainage needs.Accordingly,the proposed UDRM effectively combines land-use information with pipeline data to give practical suggestions for pipeline modification and land-use optimization to combat urban floods.Therefore,this methodology warrants further promotion in the field of urban re-planning.展开更多
基金Industry-University-Research Cooperation Fund Project of the Eighth Research Institute of China Aerospace Science and Technology Corporation(No.USCAST2022-11)。
文摘The path planning problem of complex wild environment with multiple elements still poses challenges.This paper designs an algorithm that integrates global and local planning to apply to the wild environmental path planning.The modeling process of wild environment map is designed.Three optimization strategies are designed to improve the A-Star in overcoming the problems of touching the edge of obstacles,redundant nodes and twisting paths.A new weighted cost function is designed to achieve different planning modes.Furthermore,the improved dynamic window approach(DWA)is designed to avoid local optimality and improve time efficiency compared to traditional DWA.For the necessary path re-planning of wild environment,the improved A-Star is integrated with the improved DWA to solve re-planning problem of unknown and moving obstacles in wild environment with multiple elements.The improved fusion algorithm effectively solves problems and consumes less time,and the simulation results verify the effectiveness of improved algorithms above.
文摘Based on the wave attack task planning method in static complex environment and the rolling optimization framework, an online task planning method in dynamic complex environment based on rolling optimization is proposed. In the process of online task planning in dynamic complex environment,online task planning is based on event triggering including target information update event, new target addition event, target failure event, weapon failure event, etc., and the methods include defense area reanalysis, parameter space update, and mission re-planning. Simulation is conducted for different events and the result shows that the index value of the attack scenario after re-planning is better than that before re-planning and according to the probability distribution of statistical simulation method, the index value distribution after re-planning is obviously in the region of high index value, and the index value gap before and after re-planning is related to the degree of posture change.
文摘Purpose: To improve the accuracy in megavoltage photon beam dose calculation in CBCT-based radiation treatment (RT) plans, using a kilovoltage cone-beam computed tomography (CBCT)-to-density-step (CBCT-SF) function. Materials and Methods: The CBCT-SF table is constructed from differential histograms of the voxel values of CBCT and Fan-beam CT (FBCT). From the CBCT histograms, frequency peaks representing air, lung, soft tissue and bone are observed and their widths in CT numbers are assigned to the lower and higher bounds of the steps in the CBCT-SF. The CBCT-SF is entered into a planning system as an alternative to the clinical CT-to-density table. The CT image sets studied in this work consist of FBCT and CBCT scans of three patients: a prostate cancer patient, a lung cancer patient and a head and neck patient;and of a humanoid phantom at sections of the pelvis, the thorax and the head. Deformable image registration is used to map the patient FBCT scans to the corresponding CBCT images to minimize anatomical variations. Three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) plans are made on the FBCT image sets of the patients and the phantom. The plans are recalculated on the CBCT scans using both the conventional CT-to-density table and the CBCT-SF. Dose calculations on the CBCT images and FBCT images are compared using dose differences, distance to agreement (DTA), Gamma analyses and dose volume histogram (DVH) analyses. Results: The results show that IMRT plans optimized using CBCT scans and FBCT scans agree dosimetrically within 1% when the CBCT-SF is used for the CBCT-based plans, including thoracic IMRT plan. In contrast, up to 5% dose difference is observed between IMRT plans optimized on FBCT scans and CBCT scans for thoracic cases if conventional CT-to-density table is used on CBCT images. Conclusions: The simple stepwise mapping of the CBCT numbers to density using the CBCT-SF resolves the inaccuracies in dose calculations previously reported in CBCT-based RT plans. CBCT-SF can be used in Image-Guided adaptive radiotherapy planning.
文摘Rapidly developing cities are under continuous physical and social changes which make sustainable urban growth concept a matured line of thinking. They are therefore, in need of restructuring to contain these changes. Likewise, Khartoum is growing rapidly and is subjected to continual transformation. It started in Independence Day （1/1/1956） by 〈3% of Sudan population and reached 16.8% in 2010 while its physical block grew beyond imagination. The objective of this paper is to throw light on Khartoum rapid growth change effects which necessitated implementation of a revolutionary restructuring programme. At first, huge rural influxes were absorbed and later physical distortions were corrected. This included squatter settlements＇ treatment to strengthen urban fabric, reallocation of incompatible urban functions, revitalization of the CBD （central business district） and other urban renewal schemes. Transportation lines were extended to ease people mobility and higher population concentrations were diluted, particularly the filthy slums. Old neighbourhoods, traditional villages, etc. were re-planned and popular physical development was encouraged. The restructuring programme appropriated population distribution, administrative districts, new local markets＇ locations and urban activities＇ distribution. The programme attained social benefits, particularly availing shelter and essential social services. Difficulties from relocation processes were encountered but settlements＇ regularization achieved social justice and sustained urban growth.
文摘Advanced countries around the world are spurring the development of Unmanned Surface Vehicles (USVs) that can operate autonomously at marine environment. The key enabling technology for such USVs is the mission planning system (MPS) that can autonomously navigate through the harsh waters. The MPS not only has the functions for the navigation, but also has the capabilities, such as obstacle avoidance, malfunction corrections, dealing with unexpected events, return home functions, and many other eventualities that cannot be programmed in advance. The autonomy levels are increasingly moving higher and it is foreseeable that the trend will continue in the future. The main purpose of this paper is the analysis of the MPS onboard the USVs, in terms of the categories, functions, and technological details. Also, we analyze the case study of autonomous mission planning control systems in various fields and introduce the features that constitute the critical functionalities of the mission planning systems.
基金This work was supported in part by the Engineering and Physical Sciences Research Council(EPSRC)of the U.K.,the Royal Society of the U.K.
文摘A growing interest in developing autonomous surface vehicles(ASVs)has been witnessed during the past two decades,including COLREGs-compliant navigation to ensure safe autonomy of ASVs operating in complex waterways.This paper reviews the recent progress in COLREGs-compliant navigation of ASVs from traditional to learning-based approaches.It features a holistic viewpoint of ASV safe navigation,namely from collision detection to decision making and then to path replanning.The existing methods in all these three stages are classified according to various criteria.An in-time overview of the recently-developed learning-based methods in motion prediction and path replanning is provided,with a discussion on ASV navigation scenarios and tasks where learning-based methods may be needed.Finally,more general challenges and future directions of ASV navigation are highlighted.
基金Special Project for Social Development of Yunnan Province(202103AC100001)Double-First Class University Plan(C176220100042)+1 种基金Scientific Research Fund Project of Yunnan Provincial Department of Education(2023Y0210)Graduate Student Funding of School of Ecology and Environmental Science,Yunnan University(Y2000229).
文摘Excess phosphorus(P)in water can lead to eutrophication and upset ecological balance.In this study,biochar with ultrathin two-dimensional nanosheets from the natural mesocarp of shaddock was chosen as the carrier.The highly dispersed and small particle size of La(OH)_(3) on the surface of the nanosheets(MSBL3)was successfully achieved using chemical impregnation for the adsorption of P in aqueous solution,and the maximum adsorption capacity was 260.0 mg P g^(−1)[La].The differences in surface crystallization of La(OH)_(3) on biochar at different La loadings were analyzed using the high-precision characterization methods.After six adsorption-desorption cycles,MSBL3 retained 76.7%of its initial performance in terms of the P adsorption capacity.The preparation of 1 g of MSBL3 costs about RMB 1,and it could reduce the P concentration in 2.6 ton of Laoyu River water to below the eutrophication threshold;and the inhibitory effect of MSBL3 on the eutrophication of water bodies was confirmed by the growth state of water hyacinth.Furthermore,0.1 M MSBL3 could inhibit Escherichia coli and Staphylococcus aureus up to 98.7%and 85.0%,respectively,which indicates that MSBL3 can be used to recover P from water and also to improve water quality.In addition,the growth of the maize seedlings verified that the P-absorbed MSBL3 waste is a good soil fertilizer and can solve the problem of post-treatment of the adsorbent.In conclusion,MSBL3 prepared in this study is a promising P sorbent for application.
基金supported by the Program for Youth Innovative Research Team in the University of Shandong Province in China(2019KJN010)。
文摘Mobile robots have been used for many industrial scenarios which can realize automated manufacturing process instead of human workers. To improve the quality of the optimal rapidly-exploring random tree(RRT^(*)) for planning path in dynamic environment, a high-quality dynamic rapidly-exploring random tree(HQD-RRT^(*)) algorithm is proposed in this paper, which generates a high-quality solution with optimal path length in dynamic environment. This method proceeds in two stages: initial path generation and path re-planning. Firstly, the initial path is generated by an improved smart rapidly-exploring random tree(RRT^(*)-SMART) algorithm, and the state tree information is stored as prior knowledge. During the process of path execution, a strategy of obstacle avoidance is proposed to avoid moving obstacles. The cost and smoothness of path are considered to re-plan the initial path to improve the path quality in this strategy. Compared with related work, a higher-quality path in dynamic environment can be achieved in this paper. HQD-RRT^(*) algorithm can obtain an optimal path with better stability. Simulations on the static and dynamic environment are conducted to clarify the efficiency of HQD-RRT^(*) in avoiding unknown obstacles.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3202002)the National Natural Science Foundation of China(Grant Nos.52025092,52209087 and 52379065).
文摘Effective urban land-use re-planning and the strategic arrangement of drainage pipe networks can significantly enhance urban flood defense capacity.Aimed at reducing the potential risks of urban flooding,this paper presents a straightforward and efficient approach to an urban distributed runoff model(UDRM).The model is developed to quantify the discharge and water depth within urban drainage pipe networks under varying rainfall intensities and land-use scenarios.The Nash efficiency coefficient of UDRM exceeds 0.9,which indicates its high computational efficiency and potential benefit in predicting urban flooding.The prediction of drainage conditions under both current and re-planned land-use types is achieved by adopting different flood recurrence intervals.The findings reveal that the re-planned land-use strategies could effectively diminish flood risk upstream of the drainage pipe network across 20-year and 50-year flood recurrence intervals.However,in the case of extreme rainfall events(a 100-year flood recurrence),the re-planned land-use approach fell short of fulfilling the requirements necessary for flood disaster mitigation.In these instances,the adoption of larger-diameter drainage pipes becomes an essential requisite to satisfy drainage needs.Accordingly,the proposed UDRM effectively combines land-use information with pipeline data to give practical suggestions for pipeline modification and land-use optimization to combat urban floods.Therefore,this methodology warrants further promotion in the field of urban re-planning.
