A number of contingencies simulated during dynamic security assessment do not generate unacceptable values of power system state variables, due to their small influence on system operation. Their exclusion from the se...A number of contingencies simulated during dynamic security assessment do not generate unacceptable values of power system state variables, due to their small influence on system operation. Their exclusion from the set of contingencies to be simulated in the security assessment would achieve a significant reduction in computation time. This paper defines a critical contingencies selection method for on-line dynamic security assessment. The selection method results from an off-line dynamical analysis, which covers typical scenarios and also covers various related aspects like frequency, voltage, and angle analyses among others. Indexes measured over these typical scenarios are used to train neural networks, capable of performing on-line estimation of a critical contingencies list according to the system state.展开更多
An optimal preventive-corrective control model for static voltage stability under multiple N-1 contingencies considering the wind power uncertainty is established in this paper.The objective is to minimize the control...An optimal preventive-corrective control model for static voltage stability under multiple N-1 contingencies considering the wind power uncertainty is established in this paper.The objective is to minimize the control variable adjustment cost including the load shedding cost of each contingency.The chance constraints of the static voltage stability margins(SvSMs)in the normal operation state and after each N-1 contingency are included.The approximate functions between the probability density functions(PDFs)of SVSMs and load shedding quantity with respect to preventive control variables are obtained to transform the expectation of load shedding quantity and the SvSM chance constraints into deterministic expressions.An approximate sequential convex quadratically constrained quadratic programming iteration method is proposed to solve the optimal control model.In each iteration,the approximate expressions and range are determined by the generated data samples.Moreover,a fast approximation calculation method of second-order matrices is proposed.By the naive Bayes classifier,the most severe N-1 contingencies are selected to replace all the contingencies to be added to the optimization model to improve the computational efficiency.Case studies on the IEEE-39 bus system and an actual provincial power grid demonstrate the effectiveness and efficiency of the proposed method.展开更多
Contingencies,such as behavior shifts of microgrid operators(MGOs)and abrupt weather fluctuations,significantly impact the economic operations of multi-microgrids(MMGs).To address these contingencies and enhance the e...Contingencies,such as behavior shifts of microgrid operators(MGOs)and abrupt weather fluctuations,significantly impact the economic operations of multi-microgrids(MMGs).To address these contingencies and enhance the economic and autonomous performance of MGOs,a self-organizing energy management modeling approach is proposed.A second-order stochastic dynamical equation(SDE)is developed to accurately characterize the self-organizing evolution of the operating cost of MGO incurred by contingencies.Firstly,an operating model of MMG relying on two random graph-driven information matrices is constructed and the order parameters are introduced to extract the probabilistic properties of variations in operating cost.Subsequently,these order parameters,which assist individuals in effectively capturing system correlations and updating state information,are incorporated as inputs into second-order SDE.The second-order SDE is then solved by using the finite difference method(FDM)within a loop-structured solution framework.Case studies conducted within a practical area in China validate that the proposed self-organizing energy management model(SEMM)demonstrates spontaneous improvements in economic performance compared with conventional models.展开更多
This paper discusses a security-constrained integrated coordination scheduling framework for an integrated electricity-natural gas system(IEGS),in which both tight interdependence between electricity and natural gas t...This paper discusses a security-constrained integrated coordination scheduling framework for an integrated electricity-natural gas system(IEGS),in which both tight interdependence between electricity and natural gas transmission networks and their distinct dynamic characteristics at different timescales are fully considered.The proposed framework includes two linear programming models.The first one focuses on hour-based steady-state coordinated economic scheduling on power outputs of electricity generators and mass flow rates of natural gas sources while considering electricity transmission N-1 contingencies.Using the steady-state mass flow rate solutions of gas sources as the initial value,the second one studies second-based slow gas dynamics and optimizes pressures of gas sources to ensure that inlet gas pressure of gas-fired generator is within the required pressure range at any time between two consecutive steady-state scheduling.The proposed framework is validated via an IEGS consisting of an IEEE 24-bus electricity network and a15-node 14-pipeline natural gas network coupled by gasfired generators.Numerical results illustrate the effectiveness of the proposed framework in coordinating electricity and natural gas systems as well as achieving economic and reliable operation of IEGS.展开更多
The Variable Series Reactors(VSRs)can efficiently control the power flow through the adjustment of the line reactance.When they are appropriately allocated in the power network,the transmission congestion and generati...The Variable Series Reactors(VSRs)can efficiently control the power flow through the adjustment of the line reactance.When they are appropriately allocated in the power network,the transmission congestion and generation cost can be reduced.This paper proposes a planning model to optimally allocate VSRs considering AC constraints and multi-scenarios including base case and contingencies.The planning model is originally a non-convex large scale mixed integer nonlinear program(MINLP),which is generally intractable.The proposed Benders approach decomposes the MINLP model into a mixed integer linear program(MILP)master problem and a number of nonlinear subproblems.Numerical case studies based on IEEE 118-bus demonstrate the high performance of the proposed approach.展开更多
Urban forest parks deliver a wide spectrum of ecosystem services that support biodiversity,climate regulation,and public well-being;however,their perceived value among local visitors remains underexplored in Southeast...Urban forest parks deliver a wide spectrum of ecosystem services that support biodiversity,climate regulation,and public well-being;however,their perceived value among local visitors remains underexplored in Southeast Asia.This study investigates visitor perceptions and economic valuation of ecosystem services at Mount Pulai Forest Eco Park in Johor,Malaysia.Grounded in the Total Economic Value(TEV)framework and ecosystem service theory,the research employed a structured on-site survey of 392 visitors and applied the Contingent Valuation Method(CVM)to assess awareness,appreciation,and willingness-to-pay(WTP)for forest conservation.Findings revealed that visitors highly valued regulating services,such as air purification and flood mitigation(mean≈4.3/5),and supporting services,like biodiversity(mean≈4.2/5),while provisioning services were rated lower(mean≈2.8/5).Despite limited familiarity with ecological terminology,only 33%understood the term“ecosystem services”.In contrast,a substantial majority(79.1%)expressed WTP for conservation efforts,proposing an average annual contribution of MYR 51.32.Additionally,65%of respondents supported an entry fee model,suggesting a mean payment of MYR 3.07 per visit.These results underscore the economic and non-economic value that urban residents assign to forest benefits,offering new insights into conservation finance and public engagement.The study’s innovation lies in its integration of ecosystem perception with economic valuation in an urban forest setting,providing a replicable framework for sustainable park management across Southeast Asia.展开更多
In this paper,the author follows the trail of C.Malabou,Q.Meillassoux,and G.Deleuze and tries to test three philosophical concepts that seem to be particularly threatened in the era of automatic digital reproduction.T...In this paper,the author follows the trail of C.Malabou,Q.Meillassoux,and G.Deleuze and tries to test three philosophical concepts that seem to be particularly threatened in the era of automatic digital reproduction.These three concepts are plasticity(defended for many years by C.Malabou),contingency(reconstructed by Q.Meillassoux),and virtuality(developed by G.Deleuze).The main task of the text will be to reflect on which of these three concepts better protects our thinking against automation and stays faithful to the ideal of creativity.In what sense are plasticity,contingency,and the possibility of virtualization the a priori condition of any transformation,physical or intellectual,affective or conceptual metamorphosis?In what sense are these three concepts the only conditions for the survival of every living being?Would a being without contingency,plasticity,and disposition to virtualization simply be a dead being?展开更多
Ensuring the reliability of power systems in microgrids is critical,particularly under contingency conditions that can disrupt power flow and system stability.This study investigates the application of Security-Constr...Ensuring the reliability of power systems in microgrids is critical,particularly under contingency conditions that can disrupt power flow and system stability.This study investigates the application of Security-Constrained Optimal Power Flow(SCOPF)using the Line Outage Distribution Factor(LODF)to enhance resilience in a renewable energy-integrated microgrid.The research examines a 30-bus system with 14 generators and an 8669 MW load demand,optimizing both single-objective and multi-objective scenarios.The single-objective opti-mization achieves a total generation cost of$47,738,while the multi-objective approach reduces costs to$47,614 and minimizes battery power output to 165.02 kW.Under contingency conditions,failures in transmission lines 1,22,and 35 lead to complete power loss in those lines,requiring a redistribution strategy.Implementing SCOPF mitigates these disruptions by adjusting power flows,ensuring no line exceeds its capacity.Specifically,in contingency 1,power in channel 4 is reduced from 59 to 32 kW,while overall load shedding is minimized to 0.278 MW.These results demonstrate the effectiveness of SCOPF in maintaining stability and reducing economic losses.Unlike prior studies,this work integrates LODF into SCOPF for large-scale microgrid applications,offering a computationally efficient contingency management framework that enhances grid resilience and supports renewable energy adoption.展开更多
The use of unmanned aerial system(UAS)in congested airspace and/or in the proximity of critical infrastructure poses several challenges as far as safe and secure operations are concerned.The paper provides a detailed ...The use of unmanned aerial system(UAS)in congested airspace and/or in the proximity of critical infrastructure poses several challenges as far as safe and secure operations are concerned.The paper provides a detailed description of the architecture and workflow of a platform for UAS traffic management(UTM),designed to pave the way for increased,improved and safer UAS operations in the civil airspace.In particular,access to low-altitude airspace for UAS operations is managed,while facilitating the implementation of beyond visual line-of-sight(BVLOS)operations,and ensuring a safe and efficient integration of UAS into both controlled and uncontrolled airspace.Detection and management of unidentified or uncooperative UAS’s is also taken care of.To this end,an architecture based on three interacting layers is proposed,with the air traffic control at the highest level,the UAS operator(s)at the bottom,and a UAS service supplier acting as an interface.The platform,with its physical and digital elements,guarantees the effective and efficient interaction among these three layers,including management of contingency scenarios,which require a variation of admissible flight volumes for UAS operations and/or fast trajectory re-planning.The platform,developed within a research project which involved several partners,was tested in a relevant operational scenario at the Grottaglie-Taranto airport in Italy.The operators involved in the tests provided positive feedback on the services provided by the platform and the usability of the interfaces,while also making suggestions for adding new features in future developments.展开更多
Aimed at the demand of contingency return at any time during the near-moon phase in the manned lunar landing missions,a fast calculation method for three-impulse contingency return trajectories is proposed.Firstly,a t...Aimed at the demand of contingency return at any time during the near-moon phase in the manned lunar landing missions,a fast calculation method for three-impulse contingency return trajectories is proposed.Firstly,a three-impulse contingency return trajectory scheme is presented by combining the Lambert transfer and maneuver at the special point.Secondly,a calculation model of three-impulse contingency return trajectories is established.Then,fast calculation methods are proposed by adopting the high-order Taylor expansion of differential algebra in the twobody trajectory dynamics model and perturbed trajectory dynamics model.Finally,the performance of the proposed methods is verified by numerical simulation.The results indicate that the fast calculation method of two-body trajectory has higher calculation efficiency compared to the semi-analytical calculation method under a certain accuracy condition.Due to its high efficiency,the characteristics of the three-impulse contingency return trajectories under different contingency scenarios are further analyzed expeditiously.These findings can be used for the design of contingency return trajectories in future manned lunar landing missions.展开更多
Objective:To estimate the willingness to pay(WTP)of Ho Chi Minh City residents for the hand,foot,and mouth disease(HFMD)vaccine and its associated factors using the contingent valuation method.Methods:This cross-secti...Objective:To estimate the willingness to pay(WTP)of Ho Chi Minh City residents for the hand,foot,and mouth disease(HFMD)vaccine and its associated factors using the contingent valuation method.Methods:This cross-sectional study was conducted in 2024,involved face-to-face interviews with 423 participants in Ho Chi Minh City.The participants were divided into two groups:parents of children under six and individuals without young children.WTP for the HFMD vaccine was assessed using the Krinsky and Robb procedure and the double-bound dichotomous choice technique.A probit regression model was used to analyze factors influencing WTP.Results:The participants had a mean age of(34.0±10.3)years,and the majority of them were female,resided in urban areas,and held a university degree.54.6%had children under six years of age,and 63.8%had never heard of the EV71 vaccine.The mean WTP for two doses of the HFMD vaccine was VND 1240000(USD 51.66).Parents of children under six years old had a mean WTP of USD 49.16,while individuals without young children had a mean WTP of USD 56.25.Significant factors that were positively associated with WTP included vaccine price,younger age,higher income,and greater knowledge about vaccines.Conclusions:The study indicates a relatively high willingness to pay for HFMD vaccination in Ho Chi Minh City,suggesting strong potential for vaccine implementation.It is recommended that the government disseminate vaccine-related information to enhance public awareness and understanding.展开更多
Renewable energy sources(RES)have strong uncertainties,which significantly increase the risks of power imbalance and load shedding in composite power systems.It is thus necessary to evaluate the operational reliabilit...Renewable energy sources(RES)have strong uncertainties,which significantly increase the risks of power imbalance and load shedding in composite power systems.It is thus necessary to evaluate the operational reliability for guiding economic dispatch and reducing the risks.Current methods cannot meet the requirement for the operational timeliness of reliability evaluations due to the high computa-tional complexity of the optimal power flow(OPF)calculations of massive contingencies.This paper pro-poses a fully analytical approach to construct fast-to-run analytical functions of reliability indices and avoid reassessments when the load and RES change.The approach consists of uniform design(UD)-based contingency screening and a modified stochastic response surface method(mSRSM).The contin-gency screening method is used to select critical contingencies while considering the uncertainties.The mSRSM is used to construct the analytical functions of the load shedding to the load and RES gener-ation for the selected contingencies.An analytical function of a smooth virtual variable that maps to the load shedding is established in such a way that,when the load and RES vary,the reliability can be assessed within a very short time rather than using laborious OPF calculations.Case studies illustrate the excellent performance of the proposed method for real-time reliability evaluation.展开更多
[Objective] This study was to analyze the personal Willingness to Pay （WI-P） on the non-use value of Dianchi lake wetland and the influential factors. [Method] Questionnaire was designed according to the Contingent ...[Objective] This study was to analyze the personal Willingness to Pay （WI-P） on the non-use value of Dianchi lake wetland and the influential factors. [Method] Questionnaire was designed according to the Contingent Valuation Method （CVM） to investigate people of different occupations at different ages, based on which the evaluation on non-use value of Dianchi lake wetland was carried out. And the relationship between WTP and social characteristics were analyzed by using non- parametric estimation. [Result] The average WTP on Dianchi lake wetland is 150.03- 217.66 yuan per person every year, and the total WTP is 626-909 million yuan ev- ery year. Age, education and residence of the respondents have remarkable influ- ence on the VVTP. The influence of education level and residence on option value is significant; bequest value is significantly correlated with age; while there is no significant relationship between existence value and social characteristics. [Conclusion] The evaluation on the non-use value of Dianchi lake wetland is important for the scientific development and utilization of wetland resources.展开更多
文摘A number of contingencies simulated during dynamic security assessment do not generate unacceptable values of power system state variables, due to their small influence on system operation. Their exclusion from the set of contingencies to be simulated in the security assessment would achieve a significant reduction in computation time. This paper defines a critical contingencies selection method for on-line dynamic security assessment. The selection method results from an off-line dynamical analysis, which covers typical scenarios and also covers various related aspects like frequency, voltage, and angle analyses among others. Indexes measured over these typical scenarios are used to train neural networks, capable of performing on-line estimation of a critical contingencies list according to the system state.
基金supported by the National Natural Science Foundation of China under Grant 51977080the Natural Science Foundation of Guangdong Province(2023A1515240075).
文摘An optimal preventive-corrective control model for static voltage stability under multiple N-1 contingencies considering the wind power uncertainty is established in this paper.The objective is to minimize the control variable adjustment cost including the load shedding cost of each contingency.The chance constraints of the static voltage stability margins(SvSMs)in the normal operation state and after each N-1 contingency are included.The approximate functions between the probability density functions(PDFs)of SVSMs and load shedding quantity with respect to preventive control variables are obtained to transform the expectation of load shedding quantity and the SvSM chance constraints into deterministic expressions.An approximate sequential convex quadratically constrained quadratic programming iteration method is proposed to solve the optimal control model.In each iteration,the approximate expressions and range are determined by the generated data samples.Moreover,a fast approximation calculation method of second-order matrices is proposed.By the naive Bayes classifier,the most severe N-1 contingencies are selected to replace all the contingencies to be added to the optimization model to improve the computational efficiency.Case studies on the IEEE-39 bus system and an actual provincial power grid demonstrate the effectiveness and efficiency of the proposed method.
基金supported by the National Natural Science Foundation of China(No.52077035)the Liaoning Revitalization Talents Program of China(No.XLYC2007181).
文摘Contingencies,such as behavior shifts of microgrid operators(MGOs)and abrupt weather fluctuations,significantly impact the economic operations of multi-microgrids(MMGs).To address these contingencies and enhance the economic and autonomous performance of MGOs,a self-organizing energy management modeling approach is proposed.A second-order stochastic dynamical equation(SDE)is developed to accurately characterize the self-organizing evolution of the operating cost of MGO incurred by contingencies.Firstly,an operating model of MMG relying on two random graph-driven information matrices is constructed and the order parameters are introduced to extract the probabilistic properties of variations in operating cost.Subsequently,these order parameters,which assist individuals in effectively capturing system correlations and updating state information,are incorporated as inputs into second-order SDE.The second-order SDE is then solved by using the finite difference method(FDM)within a loop-structured solution framework.Case studies conducted within a practical area in China validate that the proposed self-organizing energy management model(SEMM)demonstrates spontaneous improvements in economic performance compared with conventional models.
基金supported by National Natural Science Foundation of China(No.51777182)in part supported by the U.S.National Science Foundation(No.CMMI-1635339).
文摘This paper discusses a security-constrained integrated coordination scheduling framework for an integrated electricity-natural gas system(IEGS),in which both tight interdependence between electricity and natural gas transmission networks and their distinct dynamic characteristics at different timescales are fully considered.The proposed framework includes two linear programming models.The first one focuses on hour-based steady-state coordinated economic scheduling on power outputs of electricity generators and mass flow rates of natural gas sources while considering electricity transmission N-1 contingencies.Using the steady-state mass flow rate solutions of gas sources as the initial value,the second one studies second-based slow gas dynamics and optimizes pressures of gas sources to ensure that inlet gas pressure of gas-fired generator is within the required pressure range at any time between two consecutive steady-state scheduling.The proposed framework is validated via an IEGS consisting of an IEEE 24-bus electricity network and a15-node 14-pipeline natural gas network coupled by gasfired generators.Numerical results illustrate the effectiveness of the proposed framework in coordinating electricity and natural gas systems as well as achieving economic and reliable operation of IEGS.
基金This work was supported in part by the Advanced Research Projects Agency-Energy(ARPA-E)the Engineering Research Center Program of the National Science Foundation+2 种基金the Department of Energy under NSF Award Number EEC-1041877the CURENT Industry Partnership Programthe Science and Technology Project of State Grid Corporation of China(Project Analysis Techniques for Coordinated Development of New Energy,Distributed Generation,Energy Storage and Power Grid to Meet Global Energy Interconnection Demand).
文摘The Variable Series Reactors(VSRs)can efficiently control the power flow through the adjustment of the line reactance.When they are appropriately allocated in the power network,the transmission congestion and generation cost can be reduced.This paper proposes a planning model to optimally allocate VSRs considering AC constraints and multi-scenarios including base case and contingencies.The planning model is originally a non-convex large scale mixed integer nonlinear program(MINLP),which is generally intractable.The proposed Benders approach decomposes the MINLP model into a mixed integer linear program(MILP)master problem and a number of nonlinear subproblems.Numerical case studies based on IEEE 118-bus demonstrate the high performance of the proposed approach.
基金funded by Universiti Kebangsaan Malaysia through research grant(SK-2024-006).
文摘Urban forest parks deliver a wide spectrum of ecosystem services that support biodiversity,climate regulation,and public well-being;however,their perceived value among local visitors remains underexplored in Southeast Asia.This study investigates visitor perceptions and economic valuation of ecosystem services at Mount Pulai Forest Eco Park in Johor,Malaysia.Grounded in the Total Economic Value(TEV)framework and ecosystem service theory,the research employed a structured on-site survey of 392 visitors and applied the Contingent Valuation Method(CVM)to assess awareness,appreciation,and willingness-to-pay(WTP)for forest conservation.Findings revealed that visitors highly valued regulating services,such as air purification and flood mitigation(mean≈4.3/5),and supporting services,like biodiversity(mean≈4.2/5),while provisioning services were rated lower(mean≈2.8/5).Despite limited familiarity with ecological terminology,only 33%understood the term“ecosystem services”.In contrast,a substantial majority(79.1%)expressed WTP for conservation efforts,proposing an average annual contribution of MYR 51.32.Additionally,65%of respondents supported an entry fee model,suggesting a mean payment of MYR 3.07 per visit.These results underscore the economic and non-economic value that urban residents assign to forest benefits,offering new insights into conservation finance and public engagement.The study’s innovation lies in its integration of ecosystem perception with economic valuation in an urban forest setting,providing a replicable framework for sustainable park management across Southeast Asia.
文摘In this paper,the author follows the trail of C.Malabou,Q.Meillassoux,and G.Deleuze and tries to test three philosophical concepts that seem to be particularly threatened in the era of automatic digital reproduction.These three concepts are plasticity(defended for many years by C.Malabou),contingency(reconstructed by Q.Meillassoux),and virtuality(developed by G.Deleuze).The main task of the text will be to reflect on which of these three concepts better protects our thinking against automation and stays faithful to the ideal of creativity.In what sense are plasticity,contingency,and the possibility of virtualization the a priori condition of any transformation,physical or intellectual,affective or conceptual metamorphosis?In what sense are these three concepts the only conditions for the survival of every living being?Would a being without contingency,plasticity,and disposition to virtualization simply be a dead being?
文摘Ensuring the reliability of power systems in microgrids is critical,particularly under contingency conditions that can disrupt power flow and system stability.This study investigates the application of Security-Constrained Optimal Power Flow(SCOPF)using the Line Outage Distribution Factor(LODF)to enhance resilience in a renewable energy-integrated microgrid.The research examines a 30-bus system with 14 generators and an 8669 MW load demand,optimizing both single-objective and multi-objective scenarios.The single-objective opti-mization achieves a total generation cost of$47,738,while the multi-objective approach reduces costs to$47,614 and minimizes battery power output to 165.02 kW.Under contingency conditions,failures in transmission lines 1,22,and 35 lead to complete power loss in those lines,requiring a redistribution strategy.Implementing SCOPF mitigates these disruptions by adjusting power flows,ensuring no line exceeds its capacity.Specifically,in contingency 1,power in channel 4 is reduced from 59 to 32 kW,while overall load shedding is minimized to 0.278 MW.These results demonstrate the effectiveness of SCOPF in maintaining stability and reducing economic losses.Unlike prior studies,this work integrates LODF into SCOPF for large-scale microgrid applications,offering a computationally efficient contingency management framework that enhances grid resilience and supports renewable energy adoption.
基金supported by the European Union and Italian Ministry of University and Research through the call PON Research and Innovation 2014-2020,Axis Ⅱ,Action 2,project AcrOSS(Environment for Safe Operations of Remotely Piloted Aircraft),project number ARS01_00702-CUP:F36C18000210005.
文摘The use of unmanned aerial system(UAS)in congested airspace and/or in the proximity of critical infrastructure poses several challenges as far as safe and secure operations are concerned.The paper provides a detailed description of the architecture and workflow of a platform for UAS traffic management(UTM),designed to pave the way for increased,improved and safer UAS operations in the civil airspace.In particular,access to low-altitude airspace for UAS operations is managed,while facilitating the implementation of beyond visual line-of-sight(BVLOS)operations,and ensuring a safe and efficient integration of UAS into both controlled and uncontrolled airspace.Detection and management of unidentified or uncooperative UAS’s is also taken care of.To this end,an architecture based on three interacting layers is proposed,with the air traffic control at the highest level,the UAS operator(s)at the bottom,and a UAS service supplier acting as an interface.The platform,with its physical and digital elements,guarantees the effective and efficient interaction among these three layers,including management of contingency scenarios,which require a variation of admissible flight volumes for UAS operations and/or fast trajectory re-planning.The platform,developed within a research project which involved several partners,was tested in a relevant operational scenario at the Grottaglie-Taranto airport in Italy.The operators involved in the tests provided positive feedback on the services provided by the platform and the usability of the interfaces,while also making suggestions for adding new features in future developments.
基金co-supported by the National Natural Science Foundation of China(No.12072365)the Technology Innovation Team of Manned Space Engineering,China。
文摘Aimed at the demand of contingency return at any time during the near-moon phase in the manned lunar landing missions,a fast calculation method for three-impulse contingency return trajectories is proposed.Firstly,a three-impulse contingency return trajectory scheme is presented by combining the Lambert transfer and maneuver at the special point.Secondly,a calculation model of three-impulse contingency return trajectories is established.Then,fast calculation methods are proposed by adopting the high-order Taylor expansion of differential algebra in the twobody trajectory dynamics model and perturbed trajectory dynamics model.Finally,the performance of the proposed methods is verified by numerical simulation.The results indicate that the fast calculation method of two-body trajectory has higher calculation efficiency compared to the semi-analytical calculation method under a certain accuracy condition.Due to its high efficiency,the characteristics of the three-impulse contingency return trajectories under different contingency scenarios are further analyzed expeditiously.These findings can be used for the design of contingency return trajectories in future manned lunar landing missions.
文摘Objective:To estimate the willingness to pay(WTP)of Ho Chi Minh City residents for the hand,foot,and mouth disease(HFMD)vaccine and its associated factors using the contingent valuation method.Methods:This cross-sectional study was conducted in 2024,involved face-to-face interviews with 423 participants in Ho Chi Minh City.The participants were divided into two groups:parents of children under six and individuals without young children.WTP for the HFMD vaccine was assessed using the Krinsky and Robb procedure and the double-bound dichotomous choice technique.A probit regression model was used to analyze factors influencing WTP.Results:The participants had a mean age of(34.0±10.3)years,and the majority of them were female,resided in urban areas,and held a university degree.54.6%had children under six years of age,and 63.8%had never heard of the EV71 vaccine.The mean WTP for two doses of the HFMD vaccine was VND 1240000(USD 51.66).Parents of children under six years old had a mean WTP of USD 49.16,while individuals without young children had a mean WTP of USD 56.25.Significant factors that were positively associated with WTP included vaccine price,younger age,higher income,and greater knowledge about vaccines.Conclusions:The study indicates a relatively high willingness to pay for HFMD vaccination in Ho Chi Minh City,suggesting strong potential for vaccine implementation.It is recommended that the government disseminate vaccine-related information to enhance public awareness and understanding.
基金supported by the Joint Research Fund in Smart Grid under cooperative agreement between the National Natural Science Foundation of China(NSFC)and the State Grid Cooperation of China(SGCC,U1966601)the Fundamental Research Funds for the Central Universities of China(2023CDJYXTD-004).
文摘Renewable energy sources(RES)have strong uncertainties,which significantly increase the risks of power imbalance and load shedding in composite power systems.It is thus necessary to evaluate the operational reliability for guiding economic dispatch and reducing the risks.Current methods cannot meet the requirement for the operational timeliness of reliability evaluations due to the high computa-tional complexity of the optimal power flow(OPF)calculations of massive contingencies.This paper pro-poses a fully analytical approach to construct fast-to-run analytical functions of reliability indices and avoid reassessments when the load and RES change.The approach consists of uniform design(UD)-based contingency screening and a modified stochastic response surface method(mSRSM).The contin-gency screening method is used to select critical contingencies while considering the uncertainties.The mSRSM is used to construct the analytical functions of the load shedding to the load and RES gener-ation for the selected contingencies.An analytical function of a smooth virtual variable that maps to the load shedding is established in such a way that,when the load and RES vary,the reliability can be assessed within a very short time rather than using laborious OPF calculations.Case studies illustrate the excellent performance of the proposed method for real-time reliability evaluation.
基金Supported by the "Research on Benefit Evaluation and Management Plan of Dianchi Lake Wetland" Project of Jiuhu Office,Yunnan Province,Chinathe Technology R&D Program for Social Development of Yunnan Province (2008ZC064M),China~~
文摘[Objective] This study was to analyze the personal Willingness to Pay （WI-P） on the non-use value of Dianchi lake wetland and the influential factors. [Method] Questionnaire was designed according to the Contingent Valuation Method （CVM） to investigate people of different occupations at different ages, based on which the evaluation on non-use value of Dianchi lake wetland was carried out. And the relationship between WTP and social characteristics were analyzed by using non- parametric estimation. [Result] The average WTP on Dianchi lake wetland is 150.03- 217.66 yuan per person every year, and the total WTP is 626-909 million yuan ev- ery year. Age, education and residence of the respondents have remarkable influ- ence on the VVTP. The influence of education level and residence on option value is significant; bequest value is significantly correlated with age; while there is no significant relationship between existence value and social characteristics. [Conclusion] The evaluation on the non-use value of Dianchi lake wetland is important for the scientific development and utilization of wetland resources.
