Bursting oscillations in a hydro-turbine governing system with two time scales

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.

Hopf Bifurcation Research of Hydraulic Turbine Governing System with a Saturation Nonlinearity

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.

Stability analysis of hydro-turbine governing system based on machine learning

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.

Terminal Sliding Mode Controllers for Hydraulic Turbine Governing System with Bifurcated Penstocks under Input Saturation

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.

Existence of hidden attractors in nonlinear hydro-turbine governing systems and its stability analysis

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.

Numerical Simulation on a Throttle Governing System with Hydraulic Butterfly Valves in a Marine Environment

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.

Fractional-Order Modeling and Dynamical Analysis of a Francis Hydro-Turbine Governing System with Complex Penstocks

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.

On-line Failure Diagnostics for Steam Turbine Hydraulic Governing System

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.

Data-Driven Modeling of Partially Observed Biological Systems

We present a numerical approach for modeling unknown dynamical systems using partially observed data,with a focus on biological systems with(relatively)complex dynamical behavior.As an extension of the recently developed deep neural network(DNN)learning methods,our approach is particularly suitable for practical situations when(i)measurement data are available for only a subset of the state variables,and(ii)the system parameters cannot be observed or measured at all.We demonstrate that,with a properly designed DNN structure with memory terms,effective DNN models can be learned from such partially observed data containing hidden parameters.The learned DNN model serves as an accurate predictive tool for system analysis.Through a few representative biological problems,we demonstrate that such DNN models can capture qualitative dynamical behavior changes in the system,such as bifurcations,even when the parameters controlling such behavior changes are completely unknown throughout not only the model learning process but also the system prediction process.The learned DNN model effectively creates a“closed”model involving only the observables when such a closed-form model does not exist mathematically.

Research on the Evolution of Country-Level BGP Network Ecosystems in 24 Years

The global Internet is composed of more than 70,000 autonomous domain networks interconnected through the Border Gateway Protocol(BGP).Studying the ecological evolution of BGP network is of great significance for analyzing the evolution trend of the global Internet.This paper focuses on the evolution of Country-Level BGP network ecosystems in 24 years,and innovatively studies the relationship between Country-Level BGP network and economy,breaking through the limitations of traditional research that only focuses on BGP network.The results revealed that the number of global BGP networks has increased by nearly 23 times and that network interconnection has increased nearly 80 times over in 24 years.It was found that the growth of the global BGP network ecosystem has slowed overall due to major global security events,although the BGP network ecosystem in some Southeast Asian countries is developing against the trend.At the same time,there is a significant positive correlation between the BGP network ecology and the national economy in the time dimension;there is a strong positive correlation in the spatial dimension,but the trend is weakening year by year.

Bias in Generative AI Systems:A 3-Layer Response and Liability Determination

The risk of bias is widely noticed in the entire process of generative artificial intelligence(generative AI)systems.To protect the rights of the public and improve the effectiveness of AI regulations,feasible measures to address the bias problem in the context of large data should be proposed as soon as possible.Since bias originates in every part and various aspects of AI product lifecycles,laws and technical measures should consider each of these layers and take different causes of bias into account,from data training,modeling,and application design.The Interim Measures for the Administration of Generative AI Service(the Interim Measures),formulated by the Office of the Central Cyberspace Affairs Commission(CAC)and other departments have taken the initiatives to govern AI.However,it lacks specific details on issues such as how to prevent the risk of bias and reduce the effect of bias in decision-making.The Interim Measures also fail to take causes of bias into account,and several principles must be further interpreted.Meanwhile,regulations on generative AI at the global level are still in their early stages.By forming a governance framework,this paper could provide the community with useful experiences and play a leading role.The framework includes at least three parts:first,determining the realm of governance and unifying related concepts;second,developing measures for different layers to identify the causes and specific aspects of bias;third,identifying parties with the skills to take responsibility for detecting bias intrusions and proposing a program for the allocation of liabilities among the large-scale platform developers.

Research on Policy Diffusion Path and Reproduction of River Chief System

The River Chief System (RCS) has evolved from local innovative practices to a national water governance strategy to address the current challenges in China’s water environmental management. In contrast to existing research that focuses on the strengths, weaknesses, and improvements of RCS, this study uses literature study to reveal the dynamic evolution of RCS through three phases, with RCS spreading from developed coastal areas to central and western inland regions. RCS’s diffusion path involves vertical diffusion between central and local levels and horizontal diffusion among local governments. Moreover, RCS has also achieved conceptual spillover, gradually expanding into other governance domains, such as the Lake Chief System, the Field Chief System, the Forestry Chief System, and the integration of multiple chief roles. However, it is essential to scrutinize the phenomenon of applying similar governance mechanisms to different areas, as it may result in challenges such as overburdening local governments, insufficient public participation, oversimplification of differences in natural resource endowments, and limited applicability. This study also provides suggestions on how to address these challenges. The study contributes theoretical insights and policy implications, providing a foundation for practical policy innovation.

“Systematic Rival”From the Perspective of Philosophy of Property System

At present,the world is undergoing accelerating changes unseen in a century.With the United States regarding China as a strategic competitor,China-EU relations have become the core of national and global governance.For this reason,we use the basic theory and tools of Philosophy of Property System to clarify the EU’s characterization of China and accordingly propose the method of judgment and the principle of response.From this,we can get three basic cognitions of“systematic rivalry”,namely mutual exclusion of common cognition(Model A),mutual exclusion and cooperation of personality cognition(Model B),and cooperation of historical cognition(Model C).In order to steadily grasp the nature of“systematic rival”and make it operable,three basic cognitive models(AB,AC,BC,ABC,etc.)are combined,and a comprehensive judgment(ABC+model)is made to adapt to the supranational sovereignty characteristics of the EU.It is believed that the nature of“systematic rivalry”in the“trinity”refers to the main aspects of competition between China and Europe.Therefore,there are three principles for the Philosophy of Property System of“systematic rival”:first,maintain the situation of competition and cooperation;second,there is no fixed mode of competition and cooperation;and third,temporary confrontation and complementarity will lead to new competition and cooperation.

Cooperative Production and Adaptive Momentum:The Constructive Logic of the New Rural Governance System in Ethnic Regions of China

The traditional governance model and hierarchical structure in China’s ethnic minority regions are inadequate for advancing farmers’income and modernizing rural governance.Moreover,these traditional structures have resulted in governance challenges including unequal allocation of rural resources,absence of villagers’agency,and lack of resource transparency.This study delves into the systematic structure of the“rural governance system in ethnic minority areas”.This study samples advanced ethnic minority township governance models from seven provinces,including Guangxi,Qinghai,and the Tibet Autonomous Region in China,and employs Grounded Theory to encode and analyze sub-elements within their governance systems.Subsequently,it investigates the construction logic of a novel rural governance system.(1)The research reveals that primary-level Party organization play a pivotal role in connecting bilateral delegated agency relationships,thereby establishing a mutually cooperative“chain-like”structure in village governance systems within ethnic minority areas.(2)The study identifies two cooperative production paths of the new rural governance in ethnic minority areas:top-down field-oriented party-government integrated governance and bottom-up legalized multi-subject collaborative governance.(3)By employing“integration means-bilateral mobilization”as the mechanism for momentum adjustment and relying on social autonomy,grassroots party organizations shape the momentum adjustment of the new rural governance system in ethnic minority areas.They do so by leveraging both formal and informal governance methods within this framework.Consequently,this study offers pertinent policy recommendations aimed at resolving the challenges of interest coordination and uneven development in ethnic minority areas amidst China’s governance modernization efforts.

Operation optimization mode for nozzle governing steam turbine unit

Based on tests and theoretical calculation an optimum steam admission mode is proposed which can effectively solve the steam-excited vibration.An operation mode jointly considering the valve point and operation load is proposed based on the analysis and study of a large number of unit operation optimization methods.According to the steam-excited vibration that occurs during the optimization process when the nozzle governing steam turbine switches from a single valve to multi-valves a steam admission optimization program is proposed.This comprehensive program considering the steam-excited vibration is applied to a 600 MW steam turbine unit to obtain the optimum sliding pressure curve and the optimum operation mode and the steam-excited vibration is solved successfully.

Establishment of the Agricultural Knowledge Management System in the Knowledge-oriented Government

In order to optimizing the process of the government agricultural decision-making, based on the theories and technologies of the knowledge management, the meaning of the knowledge-based government is firstly analyzed. Combining with the detailed requirements of government for agricultural knowledge management, an agricultural knowledge management system including the agricultural knowledge sharing system, the agricultural Web data-mining system and the agricultural expert decision system is established in the paper.

Looking for a Chinese solution to global problems:The situation and countermeasures of marine plastic waste and microplastics pollution governance system in China

As one of the top ten environmental problems to be solved in the world,marine plastic waste and microplastic pollution seriously affect the health of marine ecosystems and the sustainable development of Marine economies.It is necessary to promote the establishment of a scientific and systematic Marine plastic waste and microplastic pollution control system and take strong measures to fundamentally curb and reverse the trend of marine pollution intensification in China.This paper first explains the practical significance of marine plastic waste and microplastic pollution control from three aspects:the sustainable development of the blue economy,the structural upgrading of the pan-plastic industry,and the improvement of public health awareness.Secondly,the particularity of marine plastic waste and microplastic pollution control system is summarized from three aspects of formation mechanism,migration path and damage performance.Then,it identifies domestic and international governance strategies and action plans from the perspectives of mechanism,subject,object,and measures,summarizes existing problems in the existing marine plastic waste and microplastic pollution control system,and gives directions for future improvement.Finally,some countermeasures and suggestions are put forward to accelerate the construction of China’s marine plastic waste and microplastic pollution control system,including the formation of a cross sectoral integrated land and sea control system,a full life cycle waste management process,a multi-participation model for marine ecological and environmental governance,and a global marine pollution prevention and control system.

ON THE LAGRANGIAN RESIDUAL CURRENT AND RESIDUAL TRANSPORT IN A MULTIPLE TIME SCALE SYSTEM OF SHALLOW SEAS

A multiple time scale perturbation method is used to discuss the Lagrangian residual current and residual transport on the basis of a weakly nonlinear dynamic model of shallow seas. The governing equations for the long-term variation of zero order " apparent concentration " (which is a linear combination of salinity , temperature of seawater and the concentration of any tracer which is conservative and passive ) and its mean value over tidal cycles are obtained for the system with single tidal constituent . and for the one with multi-constituents, winds and thermohaline. The equations for the two cases are in the same form and show this long-term variation resulted from the cumulative effect of residual convection and turbulent diffusion .The multiple time scale variation of current is caused by tides, winds, and the thermohaline and the nonlinear effects of the system. The derived set of governing field equations of the Lagrangian current for this multiple time scale system is also in the same form

Governing the gold rush into emerging markets: a case study of Indonesia’s regulatory responses to the expansion of Chinese-backed online P2P lending

Peer-to-peer(P2P)lending has the potential to boost financial inclusion in emerging markets.This paper contributes to the literature on fintech governance in emerging Asian markets.It examines the case of the Indonesian government’s approach in regulating the P2P lending sector using both primary interviews and secondary firmlevel data.Driven by regulation tightening in China and regulatory gaps in Indonesia,Chinese investments became the largest in this sector contributing,however,to growing risks from illegal business practices.The Indonesian government responded by creating new regulations and institutions,mitigating risks without stifling the potential for financial inclusion.We conclude a proactive approach towards monitoring and regulating emerging high-tech industries should be sought by strengthening links with industry and civil society,and through international cooperation for policy and knowledge sharing.

Payment for ecosystem services:emerging lessons

Market based initiatives for management of degrading ecosystems and their services have received the added attention as one of the innovative responses in the reent years. Those initiatives such as direct and indirect payment for ecosystem services like premium for rain forest honey, payment by the people at the lower reach to those at the upper reach for the watershed services etc. have drawn the attention of the decision makers as they have proved to be far more cost effective.This paper wynthesizes the key messages from some of the paper are carbon, watershed services and biodiversity, We find that while credible valuation of ecosystem services for all services remain a critical concern behind setting up the payment mechanism, absent of necessary institutional framework may seriously undermine this innovative response for management of ecosystems. In the paper, necessary institutional mechanisms enabling the market for those services have been sketched out, Key messages from those cases have been synthesized.