A fast-slow coupled model of the hydro-turbine governing system （HTGS） is established by introducing frequency disturbance in this paper. Based on the proposed model, the performances of two time scales for bursting...A fast-slow coupled model of the hydro-turbine governing system （HTGS） is established by introducing frequency disturbance in this paper. Based on the proposed model, the performances of two time scales for bursting oscillations in the HTGS are investigated and the effect of periodic excitation of frequency disturbance is analyzed by using the bifurcation diagrams, time waveforms and phase portraits. We find that stability and operational characteristics of the HTGS change with the value of system parameter kd. Furthermore, the comparative analyses for the effect of the bursting oscillations on the system with different amplitudes of the periodic excitation a are carried out. Meanwhile, we obtain that the relative deviation of the mechanical torque mt rises with the increase of a. These methods and results of the study, combined with the performance of two time scales and the fast-slow coupled engineering model, provide some theoretical bases for investigating interesting physical phenomena of the engineering system.展开更多
A nonlinear mathematical model for hydro turbine governing system with saturation nonlinearity in small perturbation has been proposed with all the essential components, i.e. turbine, PID t^^pe governor with saturatio...A nonlinear mathematical model for hydro turbine governing system with saturation nonlinearity in small perturbation has been proposed with all the essential components, i.e. turbine, PID t^^pe governor with saturation part and generator included in the model. Existence, stability and direction of Hopf bifurcation of an example HTGS are investigated in detail and presented in forms of bifurcation diagrams and time ＂wavefomis. The analysis show,that a supercritical Hopf bifurcation may exist in hydraulic turbine systems in some certain conditions. Moreover, the dynaiidc behavior of system with different parameters such as Tw, Tab, Ty and 尺 are studied extensively. An example with numerical simulations is presented to illustrate the theoretical results. The researches provide a reasonable explanation for the Hopf phenomenon happened in operation of hydroelectric generating unit.展开更多
Hydro-turbine governing system is a time-varying complex system with strong non-linearity,and its dynamic characteristics are jointly affected by hydraulic,mechanical,electrical,and other factors.Aiming at the stabili...Hydro-turbine governing system is a time-varying complex system with strong non-linearity,and its dynamic characteristics are jointly affected by hydraulic,mechanical,electrical,and other factors.Aiming at the stability of the hydroturbine governing system,this paper first builds a dynamic model of the hydro-turbine governing system through mechanism modeling,and introduces the transfer coefficient characteristics under different load conditions to obtain the stability category of the system.BP neural network is used to perform the machine study and the predictive analysis of the stability of the system under different working conditions is carried out by using the additional momentum method to optimize the algorithm.The test set results show that the method can accurately distinguish the stability category of the hydro-turbine governing system(HTGS),and the research results can provide a theoretical reference for the operation and management of smart hydropower stations in the future.展开更多
Terminal sliding mode controller method is introduced to enhance the regulation performance of the hydraulic turbine governing system(HTGS).For the purpose of describing the characteristics of controlled system and de...Terminal sliding mode controller method is introduced to enhance the regulation performance of the hydraulic turbine governing system(HTGS).For the purpose of describing the characteristics of controlled system and deducing the control rule,a nonlinear mathematic model of hydraulic turbine governing system with bifurcated penstocks(HTGSBF)under control input saturation is established,and the input/output state linearization feedback approach is used to obtain the relationship between turbine speed and controller output.To address the control input saturation problem,an adaptive assistant system is designed to compensate for controller truncation.Numerical simulations have been conducted under fixed point stabilization and periodic orbit tracking conditions to compare the dynamic performances of proposed terminal sliding mode controllers and conventional sliding mode controller.The results indicate that the proposed terminal sliding mode controllers not only have a faster response and accurate tracking results,but also own a stronger robustness to the system parameter variations.Moreover,the comparisons between the proposed terminal sliding mode controllers and current most often used proportional-integral-differential(PID)controller,as well its variant NPID controller,are discussed at the end of this paper,where the superiority of the terminal sliding mode controllers also have been verified.展开更多
This work studies the stability and hidden dynamics of the nonlinear hydro-turbine governing system with an output limiting link,and propose a new six-dimensional system,which exhibits some hidden attractors.The param...This work studies the stability and hidden dynamics of the nonlinear hydro-turbine governing system with an output limiting link,and propose a new six-dimensional system,which exhibits some hidden attractors.The parameter switching algorithm is used to numerically study the dynamic behaviors of the system.Moreover,it is investigated that for some parameters the system with a stable equilibrium point can generate strange hidden attractors.A self-excited attractor with the change of its parameters is also recognized.In addition,numerical simulations are carried out to analyze the dynamic behaviors of the proposed system by using the Lyapunov exponent spectra,Lyapunov dimensions,bifurcation diagrams,phase space orbits,and basins of attraction.Consequently,the findings in this work show that the basins of hidden attractors are tiny for which the standard computational procedure for localization is unavailable.These simulation results are conducive to better understanding of hidden chaotic attractors in higher-dimensional dynamical systems,and are also of great significance in revealing chaotic oscillations such as uncontrolled speed adjustment in the operation of hydropower station due to small changes of initial values.展开更多
Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems res...Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.展开更多
This paper investigates the stability of the Francis hydro-turbine governing system with complex penstocks in the grid-connected mode. Firstly, a novel fractional-order nonlinear mathematical model of a Francis hydro-...This paper investigates the stability of the Francis hydro-turbine governing system with complex penstocks in the grid-connected mode. Firstly, a novel fractional-order nonlinear mathematical model of a Francis hydro-turbine governing system with complex penstocks is built from an engineering application perspective. This model is described by state-space equations and is composed of the Francis hydro-turbine model, the fractional-order complex penstocks model, the third-order generator model, and the hydraulic speed governing system model. Based on stability theory for a fractional-order nonlinear system, this study discovers a basic law of the bifurcation points of the above system with a change in the fractional-order a. Secondly, the stable region of the governing system is investigated in detail,and nonlinear dynamical behaviors of the system are identified and studied exhaustively via bifurcation diagrams, time waveforms, phase orbits, Poincare maps, power spectrums and spectrograms. Results of these numerical experiments provide a theoretical reference for further studies of the stability of hydropower stations.展开更多
This paper presents an on-line failure diagnostic method for steam turbine hydraulic governing system. This method uses the estimated values of friction on sliding valves to calculuate the corresponding dead band. Und...This paper presents an on-line failure diagnostic method for steam turbine hydraulic governing system. This method uses the estimated values of friction on sliding valves to calculuate the corresponding dead band. Under load rejection, the steam turbine's additional overspeed caused by these dead bands are studied through computer simulation. This on-line detection of dead bands can realize the failure detection of blockage fault of sliding valves.展开更多
River ethics,a significant advancement inspired by Chinese President XI Jinping's ecological civilization thought,embodies the philosophical essence of river governance and represents a legacy of innovation by gen...River ethics,a significant advancement inspired by Chinese President XI Jinping's ecological civilization thought,embodies the philosophical essence of river governance and represents a legacy of innovation by generations of water resources professionals.Rooted in river ecology,it offers a framework for advancing modern water governance systems and capabilities.This paper examines eight dimensions of river ethics to provide actionable recommendations:enhancing knowledge systems on water,rivers,and lakes;addressing critical challenges in water governance to strengthen the foundational role of water authorities in ensuring water security,resource management,ecological sustainability and environmental protection;optimizing water project planning to mitigate ecological impacts;ensuring high standards in the lifecycle management of water projects;refining water diversion strategies for precise scheduling;utilizing ecosystem complexity for river and lake restoration;implementing tiered management of water-related disasters;and driving reforms to modernize water governance systems and mechanisms.展开更多
The global trade governance system is the institutional safeguard for maintaining the operation of world trade. It consists of governance entities, platforms and rules. Since the end of World War Ⅱ, the global trade ...The global trade governance system is the institutional safeguard for maintaining the operation of world trade. It consists of governance entities, platforms and rules. Since the end of World War Ⅱ, the global trade governance system has mainly referred to the multilateral trading system, with the General Agreement on Tariffs and Trade(GATT) and the World Trade Organization(WTO) serving as governance platforms.展开更多
This paper develops an economic growth model incorporating China’s Environmental Target Responsibility System(ETRS)to analyze its impact on both economic growth and social welfare.We find that the ETRS’s effect on e...This paper develops an economic growth model incorporating China’s Environmental Target Responsibility System(ETRS)to analyze its impact on both economic growth and social welfare.We find that the ETRS’s effect on economic growth is complex,resulting from the interplay of three key factors:its potential to improve environmental quality,its potential dampening effect on total factor productivity(TFP),and its influence on local government spending on environmental governance.A balanced ETRS can improve environmental quality,promote technological innovation,and enhance social welfare.However,excessively stringent targets and overly emphasized responsibility may lead to declines in both economic growth and social welfare.From the perspective of balancing economic growth and social welfare,we find that the ETRS that maximizes economic growth is less stringent than the ETRS that maximizes social welfare.Crucially,the economic growth cost of shifting from a growth-maximizing to a welfare-maximizing ETRS is minimal.In other words,significant improvements in environmental quality and public well-being can be achieved without substantially sacrificing economic dynamism.This paper attempts to model China’s unique environmental target assessment system within the framework of endogenous growth theory,offering a new perspective for understanding the dynamic relationship between economic growth and environmental quality in China.展开更多
This study analyzes the User Interface(UI)and User Experience(UX)of information systems that provide local government information.The systems analyzed are the Local Administrative Comprehensive Information Disclosure ...This study analyzes the User Interface(UI)and User Experience(UX)of information systems that provide local government information.The systems analyzed are the Local Administrative Comprehensive Information Disclosure System(Zheripan),the Integrated Local Financial Disclosure System(Qinching Online),and the Local Regulations Information System(12348 Zhejiang Legal Network).The Local Administrative Comprehensive Information Disclosure System offers public service and personnel information,while the Integrated Local Financial Disclosure System provides financial information,and the Local Regulations Information System offers legal information as its main content.The analysis framework utilized three elements:objective data,psychological factors,and heuristic evaluation.The results of the first objective data analysis show that approximately 70%of visits to Zheripan and Qinching Online are through search,and the time spent on the homepage is short.In contrast,about 70%of visits to the 12348 Zhejiang Legal Network are direct visits,with users browsing multiple pages with a clear purpose.In terms of data provision methods,Zheripan provides two types of data in three formats,Qinching Online offers 28 types of data in five formats,and 12348 Zhejiang Legal Network provides one type of information in a single format.The second psychological factor analysis found that all three websites had a number of menus suitable for short-term cognitive capacity.However,only one of the sites had a layout that considered the user’s eye movement.Finally,the heuristic evaluation revealed that most of the evaluation criteria were not met.While the design is relatively simple and follows standards,feedback for users,error prevention,and help options were lacking.Moreover,the user-specific usability was low,and the systems remained at the information-providing level.Based on these findings,both short-term and long-term improvement measures for creating an interactive system beyond simple information disclosure are proposed.展开更多
Background:Although there is growing evidence of the use of artificial intelligence(AI)techniques in sports,ethical issues surrounding AI use are being discussed at a minimal level.Thus,this systematic scoping review ...Background:Although there is growing evidence of the use of artificial intelligence(AI)techniques in sports,ethical issues surrounding AI use are being discussed at a minimal level.Thus,this systematic scoping review aimed to summarize the current ethical implications associated with using AI in sports.Methods:In this study,a total of 9 databases-MEDLINE/PubMed,Embase,Cochrane Library,ProQuest,EBSCOhost,IEEE Xplore,Web of Science,Scopus,and Google Scholar--were searched.The review protocol was registered(https://osfio/42a8q)before extracting data.The search yielded 397 studies,and 25 studies met the inclusion and exclusion criteria.Results:The 25 studies were categorized into 4 primary ethical concerns:fairness and bias,transparency and explainability,privacy and data ethics,and accountability in AI's application in sports.These categorizations were derived based on the systematic review ofethical issues highlighted across the selected studies.Fifteen studies delved into fairness and bias,focusing on how AI can perpetuate existing inequalities in sports.Thirteen studies addressed the lack of transparency,emphasizing the challenges in interpretability and trust in AI-driven decisions.Privacy and data ethics emerged as significant in22 studies,highlighting risks related to the misuse of athletes’sensitive data.Finally,account-ability was examined in 8 studies,stressing the ethical obligations of AI developers and users in sports contexts.The thematic analysis revealed overlapping concerns,as some studies addressed multiple issues simultaneously.Conclusion:Future research should focus on developing ethical frameworks tailored to underrepresented sports contexts and creating global standards for AI regulation in sports.This includes investigating the implications of AI applications in amateur sports,enhancing diversity in AI training datasets,and exploring the integration of ethical AI practices across various sports governance structures.展开更多
The Global Governance Initiative(GGI)is another important public good that China has contributed to the world,following the Global Development Initiative,the Global Security Initiative,and the Global Civilization Init...The Global Governance Initiative(GGI)is another important public good that China has contributed to the world,following the Global Development Initiative,the Global Security Initiative,and the Global Civilization Initiative.By systematically analyzing the historical evolution,core concepts,and contemporary value of the GGI,this article illuminates its role,as a Chinese proposal presented amidst the global changes unseen in a century,in building a more just and equitable global governance system and striving for a community with a shared future for humanity.The proposal of the GGI comes at a time when the deficit in global governance is continuing to grow,and the governance system is in desperate need of reform.The five core concepts of the GGI have significant theoretical and practical value,pointing the way forward for humanity as a whole.展开更多
On March 19,2025,the Premier of the State Council,Li Qiang,signed Order No.801,announcing the“Regulations of the State Council on Resolving Foreign-related Intellectual Property Disputes”(hereinafter referred to as ...On March 19,2025,the Premier of the State Council,Li Qiang,signed Order No.801,announcing the“Regulations of the State Council on Resolving Foreign-related Intellectual Property Disputes”(hereinafter referred to as the“regulations”).展开更多
Cultural ecosystem services(CES)provided by urban green infrastructure are essential for enhancing social well-being and resilience.Identifying and mapping CES at a local scale is crucial for informed land-use decisio...Cultural ecosystem services(CES)provided by urban green infrastructure are essential for enhancing social well-being and resilience.Identifying and mapping CES at a local scale is crucial for informed land-use decisions that align with citizens'perceptions.However,research on ecosystem services in Romania has been limited,with a notable gap in the assessment of CES provided by urban green spaces.This study is the first to focus on Băneasa Forest,the only urban forest in Bucharest,which serves as a vital recreational area for thousands of residents and visitors.For the first time in Romania,this research uses a web-based Participatory GIS survey to collect spatially referenced data.The survey,which combines questionnaires and mapping exercises,allows us to produce high-resolution CES maps based on 816 responses.The results reveal that the forest's natural characteristics are perceived as the primary contributors to CES.These findings are valuable for urban planners,as they highlight the needs and expectations of forest visitors,promote conservation efforts,and foster collaboration to prevent conflicts.Alongside factors frequently discussed in the literature,such as age and accessibility,the percentage of green space in residents'neighborhoods emerges as a significant factor influencing CES preferences.This insight presents a novel contribution to the literature,being of particular importance for urban planners and policymakers,as it underscores the need to consider not just the green space within parks and forests,but also the broader context of surrounding neighborhoods when planning for CES.Understanding that the availability of nearby green space influences residents'CES preferences can guide more effective strategies to enhance access to CES in urban areas,both in Bucharest and elsewhere.This is especially relevant in the face of climate change and other emerging challenges,which are likely to increase the demand for CES in the future.展开更多
With the rapid development of generative artificial intelligence(AI)technology in the field of education,global educational systems are facing unprecedented opportunities and challenges,urgently requiring the establis...With the rapid development of generative artificial intelligence(AI)technology in the field of education,global educational systems are facing unprecedented opportunities and challenges,urgently requiring the establishment of comprehensive,flexible,and forward-looking governance solutions.The“Australian Framework for Generative AI in Schools”builds a multi-dimensional governance system covering aspects such as teaching and humanistic care,fairness and transparency,and accountability and security.Based on 22 specific principles and six core elements,it emphasizes a human-centered design concept,adopts a principle-based flexible structure,focuses on fairness and transparency,and stresses accountability and security.The framework provides valuable references for the use of generative AI in China’s education system and holds significant importance for promoting educational modernization and cultivating innovative talents adapted to the era of artificial intelligence.展开更多
The application of ecosystem services(ES)theories in land consolidation is a confusing issue that has long plagued scholars and government officials.As the upgraded version of traditional land consolidation,comprehens...The application of ecosystem services(ES)theories in land consolidation is a confusing issue that has long plagued scholars and government officials.As the upgraded version of traditional land consolidation,comprehensive land consolidation(CLC)emphasizes ecological benefits,but it does not achieve the expected effect during the pilot phase.This study first proposed a theoretical analysis framework based on ES knowledge to answer the three key questions of why,where,and how to implement CLC better.Taking mountainous counties as the study area,we found that ES trade-offs/synergies,bundles,and drivers were significantly affected by scale effects.ES knowledge can play a crucial role in designing multi-scale CLC strategies regarding the objective,zoning,intensity,and mode.Specifically,mitigating the significant trade-offs between recreational opportunities,food production,and other ES is the top priority of CLC.Land consolidation zoning based on the ES bundles analysis is more rational and can provide the scientific premise for designing locally adapted CLC measures.Land consolidation can be classified into high-intensity direct intervention and low-intensity indirect intervention modes,based on the major drivers of ES.These findings help narrow the gap between ES and CLC practices.展开更多
Forests all over the world have been dramatically impacted by climate change,which has contributed to an increase in the number of pathogen invasions and the rise in the prevalence of forest diseases.This article pres...Forests all over the world have been dramatically impacted by climate change,which has contributed to an increase in the number of pathogen invasions and the rise in the prevalence of forest diseases.This article presents a systematic review that investigates the intricate relationship between climate change and the prevalence of forest diseases.The study identifies climate-related factors that drive the rising incidence of these forest diseases.Following the PRISMA guidelines,73 studies were selected and analyzed from a pool of 3,510 articles,focusing on their spatial and temporal patterns,contextual drivers,and linkages to climate change.The findings underscore the critical role of extended drought periods and rising temperatures as key factors exacerbating forest disease outbreaks.Methodologically,only 3%of the studies utilized field sampling,indicating a predominance of laboratory analysis methods at 45%.Geographically,temperate forests accounted for 78%of the studies,forest plantations 20%,and boreal forests 2%.This review highlights the pressing need for sustainable forest management practices to counteract the adverse impacts of climate change on forest ecosystems.By identifying critical climate drivers and ecological vulnerabilities,this research provides a foundation for adaptive silviculture and pathogen management strategies.展开更多
基金Project supported by the Scientific Research Foundation of the National Natural Science Foundation of China–Outstanding Youth Foundation(Grant No.51622906)the National Natural Science Foundation of China(Grant No.51479173)+3 种基金the Fundamental Research Funds for the Central Universities,China(Grant No.201304030577)the Scientific Research Funds of Northwest A&F University,China(Grant No.2013BSJJ095)the Science Fund for Excellent Young Scholars from Northwest A&F University(Grant No.Z109021515)the Shaanxi Provincial Nova Program,China(Grant No.2016KJXX-55)
文摘A fast-slow coupled model of the hydro-turbine governing system （HTGS） is established by introducing frequency disturbance in this paper. Based on the proposed model, the performances of two time scales for bursting oscillations in the HTGS are investigated and the effect of periodic excitation of frequency disturbance is analyzed by using the bifurcation diagrams, time waveforms and phase portraits. We find that stability and operational characteristics of the HTGS change with the value of system parameter kd. Furthermore, the comparative analyses for the effect of the bursting oscillations on the system with different amplitudes of the periodic excitation a are carried out. Meanwhile, we obtain that the relative deviation of the mechanical torque mt rises with the increase of a. These methods and results of the study, combined with the performance of two time scales and the fast-slow coupled engineering model, provide some theoretical bases for investigating interesting physical phenomena of the engineering system.
文摘A nonlinear mathematical model for hydro turbine governing system with saturation nonlinearity in small perturbation has been proposed with all the essential components, i.e. turbine, PID t^^pe governor with saturation part and generator included in the model. Existence, stability and direction of Hopf bifurcation of an example HTGS are investigated in detail and presented in forms of bifurcation diagrams and time ＂wavefomis. The analysis show,that a supercritical Hopf bifurcation may exist in hydraulic turbine systems in some certain conditions. Moreover, the dynaiidc behavior of system with different parameters such as Tw, Tab, Ty and 尺 are studied extensively. An example with numerical simulations is presented to illustrate the theoretical results. The researches provide a reasonable explanation for the Hopf phenomenon happened in operation of hydroelectric generating unit.
文摘Hydro-turbine governing system is a time-varying complex system with strong non-linearity,and its dynamic characteristics are jointly affected by hydraulic,mechanical,electrical,and other factors.Aiming at the stability of the hydroturbine governing system,this paper first builds a dynamic model of the hydro-turbine governing system through mechanism modeling,and introduces the transfer coefficient characteristics under different load conditions to obtain the stability category of the system.BP neural network is used to perform the machine study and the predictive analysis of the stability of the system under different working conditions is carried out by using the additional momentum method to optimize the algorithm.The test set results show that the method can accurately distinguish the stability category of the hydro-turbine governing system(HTGS),and the research results can provide a theoretical reference for the operation and management of smart hydropower stations in the future.
基金supported by Open Fund of Hubei Provincial Key Laboratory for Operation and Control of Cascaded Hydropower Station in China Three Gorges University(No.2019KJX02).
文摘Terminal sliding mode controller method is introduced to enhance the regulation performance of the hydraulic turbine governing system(HTGS).For the purpose of describing the characteristics of controlled system and deducing the control rule,a nonlinear mathematic model of hydraulic turbine governing system with bifurcated penstocks(HTGSBF)under control input saturation is established,and the input/output state linearization feedback approach is used to obtain the relationship between turbine speed and controller output.To address the control input saturation problem,an adaptive assistant system is designed to compensate for controller truncation.Numerical simulations have been conducted under fixed point stabilization and periodic orbit tracking conditions to compare the dynamic performances of proposed terminal sliding mode controllers and conventional sliding mode controller.The results indicate that the proposed terminal sliding mode controllers not only have a faster response and accurate tracking results,but also own a stronger robustness to the system parameter variations.Moreover,the comparisons between the proposed terminal sliding mode controllers and current most often used proportional-integral-differential(PID)controller,as well its variant NPID controller,are discussed at the end of this paper,where the superiority of the terminal sliding mode controllers also have been verified.
基金the Fundamental Research Funds for the Northwest A&F University(Grant No./Z1090220172)the Scientific Research Foundation of the Natural Science Foundation of Shaanxi Province,China(Grant No.2019JLP-24)+1 种基金the Shaanxi Province Innovation Talent Promotion PlanScience and Technology Innovation Team,China(Grant No.2020TD-025)the Water Conservancy Science and Technology Program of Shaanxi Province,China(Grant No.2018slkj-9)。
文摘This work studies the stability and hidden dynamics of the nonlinear hydro-turbine governing system with an output limiting link,and propose a new six-dimensional system,which exhibits some hidden attractors.The parameter switching algorithm is used to numerically study the dynamic behaviors of the system.Moreover,it is investigated that for some parameters the system with a stable equilibrium point can generate strange hidden attractors.A self-excited attractor with the change of its parameters is also recognized.In addition,numerical simulations are carried out to analyze the dynamic behaviors of the proposed system by using the Lyapunov exponent spectra,Lyapunov dimensions,bifurcation diagrams,phase space orbits,and basins of attraction.Consequently,the findings in this work show that the basins of hidden attractors are tiny for which the standard computational procedure for localization is unavailable.These simulation results are conducive to better understanding of hidden chaotic attractors in higher-dimensional dynamical systems,and are also of great significance in revealing chaotic oscillations such as uncontrolled speed adjustment in the operation of hydropower station due to small changes of initial values.
文摘Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.
基金supported by the Scientific Research Foundation of the National Natural Science Foundation-Outstanding Youth Foundation(No.51622906)National Natural Science Foundation of China (No.51479173)+4 种基金Fundamental Research Funds for the Central Universities (201304030577)Scientific Research Funds of Northwest A&F University (2013BSJJ095)the Scientific Research Foundation for Water Engineering in Shaanxi Province (2013slkj-12)the Science Fund for Excellent Young Scholars from Northwest A&F University (Z109021515)the Shaanxi Nova Program (2016KJXX-55)
文摘This paper investigates the stability of the Francis hydro-turbine governing system with complex penstocks in the grid-connected mode. Firstly, a novel fractional-order nonlinear mathematical model of a Francis hydro-turbine governing system with complex penstocks is built from an engineering application perspective. This model is described by state-space equations and is composed of the Francis hydro-turbine model, the fractional-order complex penstocks model, the third-order generator model, and the hydraulic speed governing system model. Based on stability theory for a fractional-order nonlinear system, this study discovers a basic law of the bifurcation points of the above system with a change in the fractional-order a. Secondly, the stable region of the governing system is investigated in detail,and nonlinear dynamical behaviors of the system are identified and studied exhaustively via bifurcation diagrams, time waveforms, phase orbits, Poincare maps, power spectrums and spectrograms. Results of these numerical experiments provide a theoretical reference for further studies of the stability of hydropower stations.
文摘This paper presents an on-line failure diagnostic method for steam turbine hydraulic governing system. This method uses the estimated values of friction on sliding valves to calculuate the corresponding dead band. Under load rejection, the steam turbine's additional overspeed caused by these dead bands are studied through computer simulation. This on-line detection of dead bands can realize the failure detection of blockage fault of sliding valves.
基金Three Gorges Follow-up Work Fund,Grant/Award Number:WE0161A042024National Key Research Program of China,Grant/Award Number:2024YFC3210900。
文摘River ethics,a significant advancement inspired by Chinese President XI Jinping's ecological civilization thought,embodies the philosophical essence of river governance and represents a legacy of innovation by generations of water resources professionals.Rooted in river ecology,it offers a framework for advancing modern water governance systems and capabilities.This paper examines eight dimensions of river ethics to provide actionable recommendations:enhancing knowledge systems on water,rivers,and lakes;addressing critical challenges in water governance to strengthen the foundational role of water authorities in ensuring water security,resource management,ecological sustainability and environmental protection;optimizing water project planning to mitigate ecological impacts;ensuring high standards in the lifecycle management of water projects;refining water diversion strategies for precise scheduling;utilizing ecosystem complexity for river and lake restoration;implementing tiered management of water-related disasters;and driving reforms to modernize water governance systems and mechanisms.
文摘The global trade governance system is the institutional safeguard for maintaining the operation of world trade. It consists of governance entities, platforms and rules. Since the end of World War Ⅱ, the global trade governance system has mainly referred to the multilateral trading system, with the General Agreement on Tariffs and Trade(GATT) and the World Trade Organization(WTO) serving as governance platforms.
基金supported by the National Social Science Fund of China(NSSFC)Project“Research on Economic Growth Theory”(Grant No.22VRC176)the National Natural Science Foundation of China(NSFC)Project“Economic Dynamic Equilibrium and Optimal Regulation Policy Framework Design in the Process of Population Aging”(Grant No.72342033)+1 种基金NSFC Project“Research on the Macroeconomic Impact Mechanism of Local Government Land Allocation Behavior”(Grant No.72003211)the Central University of Finance and Economics Youth Research Innovation Team Support Program Project“Research on Data-Based Platform Anti-Monopoly Regulation”(Grant No.20230047).
文摘This paper develops an economic growth model incorporating China’s Environmental Target Responsibility System(ETRS)to analyze its impact on both economic growth and social welfare.We find that the ETRS’s effect on economic growth is complex,resulting from the interplay of three key factors:its potential to improve environmental quality,its potential dampening effect on total factor productivity(TFP),and its influence on local government spending on environmental governance.A balanced ETRS can improve environmental quality,promote technological innovation,and enhance social welfare.However,excessively stringent targets and overly emphasized responsibility may lead to declines in both economic growth and social welfare.From the perspective of balancing economic growth and social welfare,we find that the ETRS that maximizes economic growth is less stringent than the ETRS that maximizes social welfare.Crucially,the economic growth cost of shifting from a growth-maximizing to a welfare-maximizing ETRS is minimal.In other words,significant improvements in environmental quality and public well-being can be achieved without substantially sacrificing economic dynamism.This paper attempts to model China’s unique environmental target assessment system within the framework of endogenous growth theory,offering a new perspective for understanding the dynamic relationship between economic growth and environmental quality in China.
文摘This study analyzes the User Interface(UI)and User Experience(UX)of information systems that provide local government information.The systems analyzed are the Local Administrative Comprehensive Information Disclosure System(Zheripan),the Integrated Local Financial Disclosure System(Qinching Online),and the Local Regulations Information System(12348 Zhejiang Legal Network).The Local Administrative Comprehensive Information Disclosure System offers public service and personnel information,while the Integrated Local Financial Disclosure System provides financial information,and the Local Regulations Information System offers legal information as its main content.The analysis framework utilized three elements:objective data,psychological factors,and heuristic evaluation.The results of the first objective data analysis show that approximately 70%of visits to Zheripan and Qinching Online are through search,and the time spent on the homepage is short.In contrast,about 70%of visits to the 12348 Zhejiang Legal Network are direct visits,with users browsing multiple pages with a clear purpose.In terms of data provision methods,Zheripan provides two types of data in three formats,Qinching Online offers 28 types of data in five formats,and 12348 Zhejiang Legal Network provides one type of information in a single format.The second psychological factor analysis found that all three websites had a number of menus suitable for short-term cognitive capacity.However,only one of the sites had a layout that considered the user’s eye movement.Finally,the heuristic evaluation revealed that most of the evaluation criteria were not met.While the design is relatively simple and follows standards,feedback for users,error prevention,and help options were lacking.Moreover,the user-specific usability was low,and the systems remained at the information-providing level.Based on these findings,both short-term and long-term improvement measures for creating an interactive system beyond simple information disclosure are proposed.
文摘Background:Although there is growing evidence of the use of artificial intelligence(AI)techniques in sports,ethical issues surrounding AI use are being discussed at a minimal level.Thus,this systematic scoping review aimed to summarize the current ethical implications associated with using AI in sports.Methods:In this study,a total of 9 databases-MEDLINE/PubMed,Embase,Cochrane Library,ProQuest,EBSCOhost,IEEE Xplore,Web of Science,Scopus,and Google Scholar--were searched.The review protocol was registered(https://osfio/42a8q)before extracting data.The search yielded 397 studies,and 25 studies met the inclusion and exclusion criteria.Results:The 25 studies were categorized into 4 primary ethical concerns:fairness and bias,transparency and explainability,privacy and data ethics,and accountability in AI's application in sports.These categorizations were derived based on the systematic review ofethical issues highlighted across the selected studies.Fifteen studies delved into fairness and bias,focusing on how AI can perpetuate existing inequalities in sports.Thirteen studies addressed the lack of transparency,emphasizing the challenges in interpretability and trust in AI-driven decisions.Privacy and data ethics emerged as significant in22 studies,highlighting risks related to the misuse of athletes’sensitive data.Finally,account-ability was examined in 8 studies,stressing the ethical obligations of AI developers and users in sports contexts.The thematic analysis revealed overlapping concerns,as some studies addressed multiple issues simultaneously.Conclusion:Future research should focus on developing ethical frameworks tailored to underrepresented sports contexts and creating global standards for AI regulation in sports.This includes investigating the implications of AI applications in amateur sports,enhancing diversity in AI training datasets,and exploring the integration of ethical AI practices across various sports governance structures.
文摘The Global Governance Initiative(GGI)is another important public good that China has contributed to the world,following the Global Development Initiative,the Global Security Initiative,and the Global Civilization Initiative.By systematically analyzing the historical evolution,core concepts,and contemporary value of the GGI,this article illuminates its role,as a Chinese proposal presented amidst the global changes unseen in a century,in building a more just and equitable global governance system and striving for a community with a shared future for humanity.The proposal of the GGI comes at a time when the deficit in global governance is continuing to grow,and the governance system is in desperate need of reform.The five core concepts of the GGI have significant theoretical and practical value,pointing the way forward for humanity as a whole.
文摘On March 19,2025,the Premier of the State Council,Li Qiang,signed Order No.801,announcing the“Regulations of the State Council on Resolving Foreign-related Intellectual Property Disputes”(hereinafter referred to as the“regulations”).
基金supported by the University of Bucharest through the“People and trees”CIVIS project.
文摘Cultural ecosystem services(CES)provided by urban green infrastructure are essential for enhancing social well-being and resilience.Identifying and mapping CES at a local scale is crucial for informed land-use decisions that align with citizens'perceptions.However,research on ecosystem services in Romania has been limited,with a notable gap in the assessment of CES provided by urban green spaces.This study is the first to focus on Băneasa Forest,the only urban forest in Bucharest,which serves as a vital recreational area for thousands of residents and visitors.For the first time in Romania,this research uses a web-based Participatory GIS survey to collect spatially referenced data.The survey,which combines questionnaires and mapping exercises,allows us to produce high-resolution CES maps based on 816 responses.The results reveal that the forest's natural characteristics are perceived as the primary contributors to CES.These findings are valuable for urban planners,as they highlight the needs and expectations of forest visitors,promote conservation efforts,and foster collaboration to prevent conflicts.Alongside factors frequently discussed in the literature,such as age and accessibility,the percentage of green space in residents'neighborhoods emerges as a significant factor influencing CES preferences.This insight presents a novel contribution to the literature,being of particular importance for urban planners and policymakers,as it underscores the need to consider not just the green space within parks and forests,but also the broader context of surrounding neighborhoods when planning for CES.Understanding that the availability of nearby green space influences residents'CES preferences can guide more effective strategies to enhance access to CES in urban areas,both in Bucharest and elsewhere.This is especially relevant in the face of climate change and other emerging challenges,which are likely to increase the demand for CES in the future.
基金2024 Undergraduate Innovation Training Program Project“Research on the Current Situation,Impact and Management Countermeasures of Generative AI in College Students’Learning”(202410065153)。
文摘With the rapid development of generative artificial intelligence(AI)technology in the field of education,global educational systems are facing unprecedented opportunities and challenges,urgently requiring the establishment of comprehensive,flexible,and forward-looking governance solutions.The“Australian Framework for Generative AI in Schools”builds a multi-dimensional governance system covering aspects such as teaching and humanistic care,fairness and transparency,and accountability and security.Based on 22 specific principles and six core elements,it emphasizes a human-centered design concept,adopts a principle-based flexible structure,focuses on fairness and transparency,and stresses accountability and security.The framework provides valuable references for the use of generative AI in China’s education system and holds significant importance for promoting educational modernization and cultivating innovative talents adapted to the era of artificial intelligence.
基金National Natural Science Foundation of China,No.42171255,No.41971216。
文摘The application of ecosystem services(ES)theories in land consolidation is a confusing issue that has long plagued scholars and government officials.As the upgraded version of traditional land consolidation,comprehensive land consolidation(CLC)emphasizes ecological benefits,but it does not achieve the expected effect during the pilot phase.This study first proposed a theoretical analysis framework based on ES knowledge to answer the three key questions of why,where,and how to implement CLC better.Taking mountainous counties as the study area,we found that ES trade-offs/synergies,bundles,and drivers were significantly affected by scale effects.ES knowledge can play a crucial role in designing multi-scale CLC strategies regarding the objective,zoning,intensity,and mode.Specifically,mitigating the significant trade-offs between recreational opportunities,food production,and other ES is the top priority of CLC.Land consolidation zoning based on the ES bundles analysis is more rational and can provide the scientific premise for designing locally adapted CLC measures.Land consolidation can be classified into high-intensity direct intervention and low-intensity indirect intervention modes,based on the major drivers of ES.These findings help narrow the gap between ES and CLC practices.
基金supported by the UKM research grant no,SK-2022-015the Peninsular Malaysia Forestry Department through the research project titled‘Prediction of Bio-Climatic Habitat Adaptation of Diseases and Pests in Selected Forest Plantation Species in Peninsular Malaysia’,grant No.PHSB-08-2020.
文摘Forests all over the world have been dramatically impacted by climate change,which has contributed to an increase in the number of pathogen invasions and the rise in the prevalence of forest diseases.This article presents a systematic review that investigates the intricate relationship between climate change and the prevalence of forest diseases.The study identifies climate-related factors that drive the rising incidence of these forest diseases.Following the PRISMA guidelines,73 studies were selected and analyzed from a pool of 3,510 articles,focusing on their spatial and temporal patterns,contextual drivers,and linkages to climate change.The findings underscore the critical role of extended drought periods and rising temperatures as key factors exacerbating forest disease outbreaks.Methodologically,only 3%of the studies utilized field sampling,indicating a predominance of laboratory analysis methods at 45%.Geographically,temperate forests accounted for 78%of the studies,forest plantations 20%,and boreal forests 2%.This review highlights the pressing need for sustainable forest management practices to counteract the adverse impacts of climate change on forest ecosystems.By identifying critical climate drivers and ecological vulnerabilities,this research provides a foundation for adaptive silviculture and pathogen management strategies.
