The aerial deployment method enables Unmanned Aerial Vehicles(UAVs)to be directly positioned at the required altitude for their mission.This method typically employs folding technology to improve loading efficiency,wi...The aerial deployment method enables Unmanned Aerial Vehicles(UAVs)to be directly positioned at the required altitude for their mission.This method typically employs folding technology to improve loading efficiency,with applications such as the gravity-only aerial deployment of high-aspect-ratio solar-powered UAVs,and aerial takeoff of fixed-wing drones in Mars research.However,the significant morphological changes during deployment are accompanied by strong nonlinear dynamic aerodynamic forces,which result in multiple degrees of freedom and an unstable character.This hinders the description and analysis of unknown dynamic behaviors,further leading to difficulties in the design of deployment strategies and flight control.To address this issue,this paper proposes an analysis method for dynamic behaviors during aerial deployment based on the Variational Autoencoder(VAE).Focusing on the gravity-only deployment problem of highaspect-ratio foldable-wing UAVs,the method encodes the multi-degree-of-freedom unstable motion signals into a low-dimensional feature space through a data-driven approach.By clustering in the feature space,this paper identifies and studies several dynamic behaviors during aerial deployment.The research presented in this paper offers a new method and perspective for feature extraction and analysis of complex and difficult-to-describe extreme flight dynamics,guiding the research on aerial deployment drones design and control strategies.展开更多
We investigate dynamical quantum phase transitions(DQPTs)in Marko-vian open quantum systems using a variational quantum simulation(VQS)algorithm based on quantum state diffusion(QSD).This approach reformulates the Lin...We investigate dynamical quantum phase transitions(DQPTs)in Marko-vian open quantum systems using a variational quantum simulation(VQS)algorithm based on quantum state diffusion(QSD).This approach reformulates the Lindblad master equation as an ensemble of pure-state trajectories,enabling efficient simula-tion of dissipative quantum dynam-ics with effectively reduced quantum resources.Focusing on the one-di-mensional transverse-field Ising mod-el(TFIM),we simulate quench dynamics under both local and global Lindblad dissipation.The QSD-VQS algorithm accurately captures the nonanalytic cusps in the Loschmidt rate function,and reveals their modulation by dissipation strength and system size.Notably,DQPTs are gradually suppressed under strong local dissipation,while they persist under strong global dissipation due to collective environmental effects.Benchmarking against exact Lindblad solutions confirms the high accuracy and scalability of our method.展开更多
With the aid of remote sensing and geographical information system,and by selecting multiple landscape indices including NP,SHID,LSI,IJI and so on,the dynamic variation of landscape pattern of Shaoguan City in 1993 an...With the aid of remote sensing and geographical information system,and by selecting multiple landscape indices including NP,SHID,LSI,IJI and so on,the dynamic variation of landscape pattern of Shaoguan City in 1993 and 2004 was analyzed from the perspective of landscape type and level based on the value of 300 meters size. The result showed that forest landscape of Shaoguan City had been eroded and divided;water landscape was much more stable;farmland landscape enjoyed high import rate and export rate;the construction land was in the process of decentralized non-equilibrium,all of which indicated that the heterogeneity and fragmentation of the overall landscape had increased.展开更多
The ecosystem of the Tibetan Plateau is highly susceptible to climate change. Currently, there is little discussion on the temporal changes in the link between climatic factors and vegetation dynamics in this region u...The ecosystem of the Tibetan Plateau is highly susceptible to climate change. Currently, there is little discussion on the temporal changes in the link between climatic factors and vegetation dynamics in this region under the changing climate.By employing Normalized Difference Vegetation Index data, the Climatic Research Unit temperature and precipitation data,and the in-situ meteorological observations, we report the temporal and spatial variations in the relationships between the vegetation dynamics and climatic factors on the Plateau over the past three decades. The results show that from the early 1980s to the mid-1990s, vegetation dynamics in the central and southeastern part of the Plateau appears to show a closer relationship with precipitation prior to the growing season than that of temperature. From the mid-1990s, the temperature rise seems to be the key climatic factor correlating vegetation growth in this region. The effects of increasing temperature on vegetation are spatially variable across the Plateau: it has negative impacts on vegetation activity in the southwestern and northeastern part of the Plateau, and positive impacts in the central and southeastern Plateau. In the context of global warming, the changing climate condition(increasing precipitation and significant rising temperature) might be the potential contributor to the shift in the climatic controls on vegetation dynamics in the central and southeastern Plateau.展开更多
Dynamic variation of water quality in Meiliang Bay and part of West Taihu Lake has been analysed based on data from 1991 to 1992. Principal Component Analysis is used to reveal the mutual relationships of various fact...Dynamic variation of water quality in Meiliang Bay and part of West Taihu Lake has been analysed based on data from 1991 to 1992. Principal Component Analysis is used to reveal the mutual relationships of various factors. It is shown that there existis an obvious spatial and temporal variation in the main factors of water quality. Annual values of TP, CON, TN, Chl-a and conductivity decrease evidently from inner Meiliang Bay to the outer from north to south. TP and TN fluctuate seasonally with much higher value in winter. This is particularly true for the mouth of Liangxi River. In addition, the Chl-1 has a synchronous variation with water temperature, although being lagged a little, and closely relates to TP and TN. Finally, the results from Principal Component Analysis show that TP, TN, SS (or SD), water temperature and Chl-a are the most influential factors to water qualuty in this area, and both suspensions and algae can contribute to transparency to Taihu Lake.展开更多
A mathematical model is developed for numerical analysis of thermal process in TIG welding with a moving arc, which is considered the double-elliptic distribution for both arc heat flux and arc pressure. An adjusting ...A mathematical model is developed for numerical analysis of thermal process in TIG welding with a moving arc, which is considered the double-elliptic distribution for both arc heat flux and arc pressure. An adjusting factor is introduced into the expression of arc pressure. The domain within which the arc heat flux is distributed non-symmetrically due to arc moving is selected appropriately, and three conditions for the domain to meet are described. The latent heat is taken into consideration by liquid fraction method. The dynamic development of weld pool geometry during TIG welding is analyzed numerically, and the effect of arc moving on the weld pool geometry is discussed. The experimental results show that the numerical analysis accuracy is obviously improved through taking the above-mentioned measures.展开更多
This paper focuses on the dynamic variation of groundwater level in Lhasacity. According to the data, the obvious characteristic of the groundwater level of the city is thatit is changing seasonally. Lhasa is divided ...This paper focuses on the dynamic variation of groundwater level in Lhasacity. According to the data, the obvious characteristic of the groundwater level of the city is thatit is changing seasonally. Lhasa is divided into three districts according to hydrogeologicalconditions: the alluvial plain of the Lhasa-river, the alluvial plain of the Doilung-river, and thealluvial fan of inter mountain, which presents a downward trend, a slight upward trend and basicallystabilizing trend over the years individually. The analysis indicates that meteorological andhydrological factors lead to the obvious dynamic change of the groundwater level. However, more andmore human activities and over-exploitation of the groundwater cause the downward trend inthegroundwater level.展开更多
By analogue with the methods and processes in continuous mechanics, a Lagrangian formulation and a Hamiltonian formulation of discrete mechanics are obtained. The dynamical equations including Euler Lagrange equations...By analogue with the methods and processes in continuous mechanics, a Lagrangian formulation and a Hamiltonian formulation of discrete mechanics are obtained. The dynamical equations including Euler Lagrange equations and Hamilton＇s canonical equations of the discrete nonconservative holonomic systems are derived on a discrete variational principle. Some illustrative examples are also given.展开更多
This paper summarized the recent development on Herglotz’s generalized variational principle and its symmetries and conserved quantities for nonconservative dynamical systems.Taking Lagrangian mechanics,Hamiltonian m...This paper summarized the recent development on Herglotz’s generalized variational principle and its symmetries and conserved quantities for nonconservative dynamical systems.Taking Lagrangian mechanics,Hamiltonian mechanics and Birkhoffian mechanics as three research frames,we introduce Herglotz’s generalized variational principle,dynamical equations of Herglotz type,Noether symmetry and conserved quantities,and their generalization to time-delay dynamics,fractional dynamics and time-scale dynamics,and put forward some problems as suggestions for future research.展开更多
In terms of the coal reservoir permeability of effective stress, coal matrix shrinkage and gas slippage,we conduct the tests of gas permeability under constant confining pressure and effective stress, as well as illus...In terms of the coal reservoir permeability of effective stress, coal matrix shrinkage and gas slippage,we conduct the tests of gas permeability under constant confining pressure and effective stress, as well as illustrate the cumulating method of permeability increment caused by the effects of gas slippage and coal matrix shrinkage.The results show that under the constant confining pressure, gas slippage affecting coal permeability changes to effective stress affecting it mainly. The change point increases with the increase of the confining pressure. The gas slippage effect leads to high permeability under low confining pressure, but coal matrix expansion results in the low value as confining and gas pressures increase. Combined with the drainage process of coalbed methane(CBM)well, the permeability is divided into four change stages based on the above analysis about the three effects, which can improve the change regulation understanding. Four stages are the downward phase under effective stress,the conversion phase of effective stress-coal matrix contraction effect(mainly based on effective stress), the rising stage of the effective stress-coal matrix contraction effect(mainly based on coal matrix contraction effect) and the rising phase of coal matrix contraction-slippage effect(mainly based on slippage effect). Permeability of coal reservoir during the process of drainage and production goes through four stages.展开更多
[Objective] The aim was to study the dynamic variation characteristics of phosphorus in paddy field runoff in saline land and its potential environmental effect. [Method] Taking Qianguo irrigation district in soda-sal...[Objective] The aim was to study the dynamic variation characteristics of phosphorus in paddy field runoff in saline land and its potential environmental effect. [Method] Taking Qianguo irrigation district in soda-saline land in Songnen Plain as study object, the dynamic variation law of phosphorus in paddy field runoff under different irrigation conditions and its potential environmental effect were discussed. [Result] Surface water in paddy field was alkaline, and scattered soil had poor fertilizer conservation capacity. Phosphorus accumulated in soil surface, which could increase the risk of phosphorus loss. Phosphorus loss in paddy field mainly occurred in irrigation period and runoff period caused by rainstorm. The concentration of total phosphorus (TP), particulate phosphorus (PP), total dissolved phosphorus (TDP) and dissolved reactive phosphorus (DRP) in paddy field runoff decreased with time, especially PP. Phosphorus concentration exceeded critical value and resulted to eutrophication, which threatened the water quality security of Chagan Lake. Phosphorus concentration in water recession canal increased with time, and eutrophication with different degrees appeared under high temperature. TP concentration in surface water of paddy field was highly negatively correlated with that in water recession canal, and the correlation coefficients R2(α=0.05)in three paddy fields were 0.850 9, 0.896 4 and 0.915 3, respectively. The pollution load of phosphorus in paddy field with the best irrigation condition was higher, and its pollution risk was the highest. Thus, such fields should be monitored and controlled mainly as the critical source area of phosphorus loss. [Conclusion] The study could provide theoretical foundations for developing saline land rationally, establishing optimal management measure of phosphorus in saline land and controlling phosphorus loss from farmland to protect local water resources.展开更多
According to the basic idea of classical yin-yang complementarity and modern dual-complementarity, in a simple and unified way proposed by Luo（1987）, some uncon ventional Hamilton-type variational principles for dyn...According to the basic idea of classical yin-yang complementarity and modern dual-complementarity, in a simple and unified way proposed by Luo（1987）, some uncon ventional Hamilton-type variational principles for dynamics of Reissner sandwich plate can be established systematically. The unconventional Hamilton-type variation principle can fully characterize the initial boundary value problem of this dynamics. In this paper, an important integral relation is given, which can be considered as the generalized principle of virtual work in mechanics. Based on this relation, it is possible not only to obtain the principle of virtual work in dynamics of Reissner sandwich plate, but also to derive systematically the complementary functionals for fivefield, two-field and one-field unconventional Hamilton-type variational principles by the generalized Legender transformations. Furthermore, with this approach, the intrinsic relationship among the various principles can be explained clearly.展开更多
Prediction intervals(PIs)for industrial time series can provide useful guidance for workers.Given that the failure of industrial sensors may cause the missing point in inputs,the existing kernel dynamic Bayesian netwo...Prediction intervals(PIs)for industrial time series can provide useful guidance for workers.Given that the failure of industrial sensors may cause the missing point in inputs,the existing kernel dynamic Bayesian networks(KDBN),serving as an effective method for PIs construction,suffer from high computational load using the stochastic algorithm for inference.This study proposes a variational inference method for the KDBN for the purpose of fast inference,which avoids the timeconsuming stochastic sampling.The proposed algorithm contains two stages.The first stage involves the inference of the missing inputs by using a local linearization based variational inference,and based on the computed posterior distributions over the missing inputs the second stage sees a Gaussian approximation for probability over the nodes in future time slices.To verify the effectiveness of the proposed method,a synthetic dataset and a practical dataset of generation flow of blast furnace gas(BFG)are employed with different ratios of missing inputs.The experimental results indicate that the proposed method can provide reliable PIs for the generation flow of BFG and it exhibits shorter computing time than the stochastic based one.展开更多
Let(X,φ) be a nonautonomous dynamical system.In this paper,we introduce the notions of packing topological entropy and measure-theoretical upper entropy for nonautonomous dynamical systems.Moreover,we establish the v...Let(X,φ) be a nonautonomous dynamical system.In this paper,we introduce the notions of packing topological entropy and measure-theoretical upper entropy for nonautonomous dynamical systems.Moreover,we establish the variational principle between the packing topological entropy and the measure-theoretical upper entropy.展开更多
To address the mooring issues of floating photovoltaic systems in areas with large tidal variations,three mooring schemes were designed and compared in this paper:anchor chain,anchor chain with added weights,and ancho...To address the mooring issues of floating photovoltaic systems in areas with large tidal variations,three mooring schemes were designed and compared in this paper:anchor chain,anchor chain with added weights,and anchor chain with Superflex.The model was established via the numerical simulation tool Orcaflex,which considers the combined effects of wind,waves,and currents.A time-domain coupled dynamic analysis was conducted on the performance of the three mooring schemes under various tidal conditions to determine the mooring cable tension and platform motion response.Furthermore,the mooring system with an anchor chain and Superflex was optimized,with a focus on analyzing the effects of the Superflex length,the diameter of the anchor chains,and the mooring radius.The mooring system with the anchor chain and Superflex exhibits more controllable and stable mooring performance in areas with large tidal variations,so that it more effectively maintains the required mooring tension level.These findings not only provide a reference for the feasibility and optimization design of photovoltaic systems in areas with large tidal variations but also offer valuable experience for the sustainable application of clean energy under specific environmental conditions.展开更多
Three oceanographic investigations from 1994 to 1995 in the Taiwan Strait show that the dissolved organic carbon (DOC) in the euphotic layer has a large-scale diurnal variation [2 ~ 4 mg/dm3], and its amplitude range ...Three oceanographic investigations from 1994 to 1995 in the Taiwan Strait show that the dissolved organic carbon (DOC) in the euphotic layer has a large-scale diurnal variation [2 ~ 4 mg/dm3], and its amplitude range has spatial and seasonal changes. Generally, the DOC in the euphotic layer is higher at day than that at night. According to the diurnal variations, DOC can be divided into two parts: new DOC and old DOC. The content of new DOC varies rapidly every day but the content of old DOC does not. Though there is still not a good explanation for this diurnal variation of DOC, it may call attention to the study of organic carbon dynamics, especially the DOC primary production of phytoplankton, the DOC utilization of bacteria, and the flux of DOC in coastal sea water.展开更多
The spacecraft with multistage solar panels have nonlinear coupling between attitudes of central body and solar panels, especially the rotation of central body is considered in space. The dynamics model is based for d...The spacecraft with multistage solar panels have nonlinear coupling between attitudes of central body and solar panels, especially the rotation of central body is considered in space. The dynamics model is based for dynamics analysis and control, and the multistage solar panels means the dynamics modeling will be very complex. In this research, the Lie group variational integrator method is introduced, and the dynamics model of spacecraft with solar panels that connects together by flexible joints is built. The most obvious character of this method is that the attitudes of central body and solar panels are all described by three-dimensional attitude matrix. The dynamics models of spacecraft with one and three solar panels are established and simulated. The study shows Lie group variational integrator method avoids parameters coupling and effectively reduces difficulty of modeling. The obtained continuous dynamics model based on Lie group is a set of ordinary differential equations and equivalent with traditional dynamics model that offers a basis for the geometry control.展开更多
4 semi-analytical approach for the dynamic response of general thin plates whichemployes finite element discretization in space domain and a series of representation intime demain is developed on the basis of Curtin v...4 semi-analytical approach for the dynamic response of general thin plates whichemployes finite element discretization in space domain and a series of representation intime demain is developed on the basis of Curtin variational principles.The formulationof time series is also investigated so that the dynamic response of plates with arbitraryshape and boundary constraints can be achieved with adequate accuracy.展开更多
From the concept of four-dimensional space and under the four kinds of time limit conditions, some general theorems for elastodynamics are developed, such as the principle of possible work action, the virtual displace...From the concept of four-dimensional space and under the four kinds of time limit conditions, some general theorems for elastodynamics are developed, such as the principle of possible work action, the virtual displacement principle, the virtual stress-momentum principle, the reciprocal theorems and the related theorems of time terminal conditions derived from it. The variational principles of potential energy action and complementary energy action, the H-W principles, the H-R principles and the constitutive variational principles for elastodynamics are obtained. Hamilton's principle, Toupin's work and the formulations of Ref. [5], [17]-[24] may be regarded as some special cases of the general principles given in the paper. By considering three cases: piecewise space-time domain, piecewise space domain, piecewise time domain, the piecewise variational principles including the potential, the complementary and the mixed energy action fashions are given. Finally, the general formulation of piecewise variational principles is derived. If the time dimension is not considered, the formulations obtained in the paper will become the corresponding ones for elastostatics.展开更多
基金co-supported by the Natural Science Basic Research Program of Shaanxi,China(No.2023-JC-QN-0043)the ND Basic Research Funds,China(No.G2022WD).
文摘The aerial deployment method enables Unmanned Aerial Vehicles(UAVs)to be directly positioned at the required altitude for their mission.This method typically employs folding technology to improve loading efficiency,with applications such as the gravity-only aerial deployment of high-aspect-ratio solar-powered UAVs,and aerial takeoff of fixed-wing drones in Mars research.However,the significant morphological changes during deployment are accompanied by strong nonlinear dynamic aerodynamic forces,which result in multiple degrees of freedom and an unstable character.This hinders the description and analysis of unknown dynamic behaviors,further leading to difficulties in the design of deployment strategies and flight control.To address this issue,this paper proposes an analysis method for dynamic behaviors during aerial deployment based on the Variational Autoencoder(VAE).Focusing on the gravity-only deployment problem of highaspect-ratio foldable-wing UAVs,the method encodes the multi-degree-of-freedom unstable motion signals into a low-dimensional feature space through a data-driven approach.By clustering in the feature space,this paper identifies and studies several dynamic behaviors during aerial deployment.The research presented in this paper offers a new method and perspective for feature extraction and analysis of complex and difficult-to-describe extreme flight dynamics,guiding the research on aerial deployment drones design and control strategies.
基金supported by the National Natural Science Foundation of China(Nos.22273122,T2350009)the Guangdong Provincial Natural Science Foundation(No.2024A1515011504)computational resources and services provided by the national supercomputer center in Guangzhou.
文摘We investigate dynamical quantum phase transitions(DQPTs)in Marko-vian open quantum systems using a variational quantum simulation(VQS)algorithm based on quantum state diffusion(QSD).This approach reformulates the Lindblad master equation as an ensemble of pure-state trajectories,enabling efficient simula-tion of dissipative quantum dynam-ics with effectively reduced quantum resources.Focusing on the one-di-mensional transverse-field Ising mod-el(TFIM),we simulate quench dynamics under both local and global Lindblad dissipation.The QSD-VQS algorithm accurately captures the nonanalytic cusps in the Loschmidt rate function,and reveals their modulation by dissipation strength and system size.Notably,DQPTs are gradually suppressed under strong local dissipation,while they persist under strong global dissipation due to collective environmental effects.Benchmarking against exact Lindblad solutions confirms the high accuracy and scalability of our method.
基金Supported by State Natural Sciences Foundation (40771002)~~
文摘With the aid of remote sensing and geographical information system,and by selecting multiple landscape indices including NP,SHID,LSI,IJI and so on,the dynamic variation of landscape pattern of Shaoguan City in 1993 and 2004 was analyzed from the perspective of landscape type and level based on the value of 300 meters size. The result showed that forest landscape of Shaoguan City had been eroded and divided;water landscape was much more stable;farmland landscape enjoyed high import rate and export rate;the construction land was in the process of decentralized non-equilibrium,all of which indicated that the heterogeneity and fragmentation of the overall landscape had increased.
基金supported by the Key Frontier Program of the Chinese Academy of Sciences (Grant No. QYZDJ-SSW-DQC043)the National Natural Science Foundation of China (Grant Nos. 41501011 and 41771012)
文摘The ecosystem of the Tibetan Plateau is highly susceptible to climate change. Currently, there is little discussion on the temporal changes in the link between climatic factors and vegetation dynamics in this region under the changing climate.By employing Normalized Difference Vegetation Index data, the Climatic Research Unit temperature and precipitation data,and the in-situ meteorological observations, we report the temporal and spatial variations in the relationships between the vegetation dynamics and climatic factors on the Plateau over the past three decades. The results show that from the early 1980s to the mid-1990s, vegetation dynamics in the central and southeastern part of the Plateau appears to show a closer relationship with precipitation prior to the growing season than that of temperature. From the mid-1990s, the temperature rise seems to be the key climatic factor correlating vegetation growth in this region. The effects of increasing temperature on vegetation are spatially variable across the Plateau: it has negative impacts on vegetation activity in the southwestern and northeastern part of the Plateau, and positive impacts in the central and southeastern Plateau. In the context of global warming, the changing climate condition(increasing precipitation and significant rising temperature) might be the potential contributor to the shift in the climatic controls on vegetation dynamics in the central and southeastern Plateau.
文摘Dynamic variation of water quality in Meiliang Bay and part of West Taihu Lake has been analysed based on data from 1991 to 1992. Principal Component Analysis is used to reveal the mutual relationships of various factors. It is shown that there existis an obvious spatial and temporal variation in the main factors of water quality. Annual values of TP, CON, TN, Chl-a and conductivity decrease evidently from inner Meiliang Bay to the outer from north to south. TP and TN fluctuate seasonally with much higher value in winter. This is particularly true for the mouth of Liangxi River. In addition, the Chl-1 has a synchronous variation with water temperature, although being lagged a little, and closely relates to TP and TN. Finally, the results from Principal Component Analysis show that TP, TN, SS (or SD), water temperature and Chl-a are the most influential factors to water qualuty in this area, and both suspensions and algae can contribute to transparency to Taihu Lake.
基金the financial support for this project from the National Natural Science Foundation of China under Grant No.50475131.
文摘A mathematical model is developed for numerical analysis of thermal process in TIG welding with a moving arc, which is considered the double-elliptic distribution for both arc heat flux and arc pressure. An adjusting factor is introduced into the expression of arc pressure. The domain within which the arc heat flux is distributed non-symmetrically due to arc moving is selected appropriately, and three conditions for the domain to meet are described. The latent heat is taken into consideration by liquid fraction method. The dynamic development of weld pool geometry during TIG welding is analyzed numerically, and the effect of arc moving on the weld pool geometry is discussed. The experimental results show that the numerical analysis accuracy is obviously improved through taking the above-mentioned measures.
文摘This paper focuses on the dynamic variation of groundwater level in Lhasacity. According to the data, the obvious characteristic of the groundwater level of the city is thatit is changing seasonally. Lhasa is divided into three districts according to hydrogeologicalconditions: the alluvial plain of the Lhasa-river, the alluvial plain of the Doilung-river, and thealluvial fan of inter mountain, which presents a downward trend, a slight upward trend and basicallystabilizing trend over the years individually. The analysis indicates that meteorological andhydrological factors lead to the obvious dynamic change of the groundwater level. However, more andmore human activities and over-exploitation of the groundwater cause the downward trend inthegroundwater level.
基金Project supported by the National Natural Science Foundation of China （Grant No 19572018）.
文摘By analogue with the methods and processes in continuous mechanics, a Lagrangian formulation and a Hamiltonian formulation of discrete mechanics are obtained. The dynamical equations including Euler Lagrange equations and Hamilton＇s canonical equations of the discrete nonconservative holonomic systems are derived on a discrete variational principle. Some illustrative examples are also given.
基金supported by the National Natural Science Foundations of China (Nos. 11972241,11572212,11272227)the Natural Science Foundation of Jiangsu Province(No. BK20191454).
文摘This paper summarized the recent development on Herglotz’s generalized variational principle and its symmetries and conserved quantities for nonconservative dynamical systems.Taking Lagrangian mechanics,Hamiltonian mechanics and Birkhoffian mechanics as three research frames,we introduce Herglotz’s generalized variational principle,dynamical equations of Herglotz type,Noether symmetry and conserved quantities,and their generalization to time-delay dynamics,fractional dynamics and time-scale dynamics,and put forward some problems as suggestions for future research.
基金the National Basic Research Program(973)of China(No.2009cb219605)
文摘In terms of the coal reservoir permeability of effective stress, coal matrix shrinkage and gas slippage,we conduct the tests of gas permeability under constant confining pressure and effective stress, as well as illustrate the cumulating method of permeability increment caused by the effects of gas slippage and coal matrix shrinkage.The results show that under the constant confining pressure, gas slippage affecting coal permeability changes to effective stress affecting it mainly. The change point increases with the increase of the confining pressure. The gas slippage effect leads to high permeability under low confining pressure, but coal matrix expansion results in the low value as confining and gas pressures increase. Combined with the drainage process of coalbed methane(CBM)well, the permeability is divided into four change stages based on the above analysis about the three effects, which can improve the change regulation understanding. Four stages are the downward phase under effective stress,the conversion phase of effective stress-coal matrix contraction effect(mainly based on effective stress), the rising stage of the effective stress-coal matrix contraction effect(mainly based on coal matrix contraction effect) and the rising phase of coal matrix contraction-slippage effect(mainly based on slippage effect). Permeability of coal reservoir during the process of drainage and production goes through four stages.
基金Supported by National Water Pollution Control and Management Science & Technology Specific Projects of China(2008ZX07207-006-04)Innovation Foundation Projects for Doctoral Students of Donghua University in 2011(11D11311)
文摘[Objective] The aim was to study the dynamic variation characteristics of phosphorus in paddy field runoff in saline land and its potential environmental effect. [Method] Taking Qianguo irrigation district in soda-saline land in Songnen Plain as study object, the dynamic variation law of phosphorus in paddy field runoff under different irrigation conditions and its potential environmental effect were discussed. [Result] Surface water in paddy field was alkaline, and scattered soil had poor fertilizer conservation capacity. Phosphorus accumulated in soil surface, which could increase the risk of phosphorus loss. Phosphorus loss in paddy field mainly occurred in irrigation period and runoff period caused by rainstorm. The concentration of total phosphorus (TP), particulate phosphorus (PP), total dissolved phosphorus (TDP) and dissolved reactive phosphorus (DRP) in paddy field runoff decreased with time, especially PP. Phosphorus concentration exceeded critical value and resulted to eutrophication, which threatened the water quality security of Chagan Lake. Phosphorus concentration in water recession canal increased with time, and eutrophication with different degrees appeared under high temperature. TP concentration in surface water of paddy field was highly negatively correlated with that in water recession canal, and the correlation coefficients R2(α=0.05)in three paddy fields were 0.850 9, 0.896 4 and 0.915 3, respectively. The pollution load of phosphorus in paddy field with the best irrigation condition was higher, and its pollution risk was the highest. Thus, such fields should be monitored and controlled mainly as the critical source area of phosphorus loss. [Conclusion] The study could provide theoretical foundations for developing saline land rationally, establishing optimal management measure of phosphorus in saline land and controlling phosphorus loss from farmland to protect local water resources.
基金Project supported by the National Natural Science Foundation of China(No.10172097)the Doctoral Foundation of Ministry of Education of China(No.20030558025)
文摘According to the basic idea of classical yin-yang complementarity and modern dual-complementarity, in a simple and unified way proposed by Luo（1987）, some uncon ventional Hamilton-type variational principles for dynamics of Reissner sandwich plate can be established systematically. The unconventional Hamilton-type variation principle can fully characterize the initial boundary value problem of this dynamics. In this paper, an important integral relation is given, which can be considered as the generalized principle of virtual work in mechanics. Based on this relation, it is possible not only to obtain the principle of virtual work in dynamics of Reissner sandwich plate, but also to derive systematically the complementary functionals for fivefield, two-field and one-field unconventional Hamilton-type variational principles by the generalized Legender transformations. Furthermore, with this approach, the intrinsic relationship among the various principles can be explained clearly.
基金supported by the National Key Research andDevelopment Program of China(2017YFA0700300)the National Natural Sciences Foundation of China(61533005,61703071,61603069)。
文摘Prediction intervals(PIs)for industrial time series can provide useful guidance for workers.Given that the failure of industrial sensors may cause the missing point in inputs,the existing kernel dynamic Bayesian networks(KDBN),serving as an effective method for PIs construction,suffer from high computational load using the stochastic algorithm for inference.This study proposes a variational inference method for the KDBN for the purpose of fast inference,which avoids the timeconsuming stochastic sampling.The proposed algorithm contains two stages.The first stage involves the inference of the missing inputs by using a local linearization based variational inference,and based on the computed posterior distributions over the missing inputs the second stage sees a Gaussian approximation for probability over the nodes in future time slices.To verify the effectiveness of the proposed method,a synthetic dataset and a practical dataset of generation flow of blast furnace gas(BFG)are employed with different ratios of missing inputs.The experimental results indicate that the proposed method can provide reliable PIs for the generation flow of BFG and it exhibits shorter computing time than the stochastic based one.
基金the National Natural Science Foundation of China (11871188, 12031019)。
文摘Let(X,φ) be a nonautonomous dynamical system.In this paper,we introduce the notions of packing topological entropy and measure-theoretical upper entropy for nonautonomous dynamical systems.Moreover,we establish the variational principle between the packing topological entropy and the measure-theoretical upper entropy.
基金financially supported by the National Key R&D Program of China(Grant No.2022YFB4200700).
文摘To address the mooring issues of floating photovoltaic systems in areas with large tidal variations,three mooring schemes were designed and compared in this paper:anchor chain,anchor chain with added weights,and anchor chain with Superflex.The model was established via the numerical simulation tool Orcaflex,which considers the combined effects of wind,waves,and currents.A time-domain coupled dynamic analysis was conducted on the performance of the three mooring schemes under various tidal conditions to determine the mooring cable tension and platform motion response.Furthermore,the mooring system with an anchor chain and Superflex was optimized,with a focus on analyzing the effects of the Superflex length,the diameter of the anchor chains,and the mooring radius.The mooring system with the anchor chain and Superflex exhibits more controllable and stable mooring performance in areas with large tidal variations,so that it more effectively maintains the required mooring tension level.These findings not only provide a reference for the feasibility and optimization design of photovoltaic systems in areas with large tidal variations but also offer valuable experience for the sustainable application of clean energy under specific environmental conditions.
文摘Three oceanographic investigations from 1994 to 1995 in the Taiwan Strait show that the dissolved organic carbon (DOC) in the euphotic layer has a large-scale diurnal variation [2 ~ 4 mg/dm3], and its amplitude range has spatial and seasonal changes. Generally, the DOC in the euphotic layer is higher at day than that at night. According to the diurnal variations, DOC can be divided into two parts: new DOC and old DOC. The content of new DOC varies rapidly every day but the content of old DOC does not. Though there is still not a good explanation for this diurnal variation of DOC, it may call attention to the study of organic carbon dynamics, especially the DOC primary production of phytoplankton, the DOC utilization of bacteria, and the flux of DOC in coastal sea water.
基金the financial support from the National Natural Science Foundation of China (Grants 11732005 and 11472058)
文摘The spacecraft with multistage solar panels have nonlinear coupling between attitudes of central body and solar panels, especially the rotation of central body is considered in space. The dynamics model is based for dynamics analysis and control, and the multistage solar panels means the dynamics modeling will be very complex. In this research, the Lie group variational integrator method is introduced, and the dynamics model of spacecraft with solar panels that connects together by flexible joints is built. The most obvious character of this method is that the attitudes of central body and solar panels are all described by three-dimensional attitude matrix. The dynamics models of spacecraft with one and three solar panels are established and simulated. The study shows Lie group variational integrator method avoids parameters coupling and effectively reduces difficulty of modeling. The obtained continuous dynamics model based on Lie group is a set of ordinary differential equations and equivalent with traditional dynamics model that offers a basis for the geometry control.
文摘4 semi-analytical approach for the dynamic response of general thin plates whichemployes finite element discretization in space domain and a series of representation intime demain is developed on the basis of Curtin variational principles.The formulationof time series is also investigated so that the dynamic response of plates with arbitraryshape and boundary constraints can be achieved with adequate accuracy.
基金Doctorate Training Fund of National Education Commission of China
文摘From the concept of four-dimensional space and under the four kinds of time limit conditions, some general theorems for elastodynamics are developed, such as the principle of possible work action, the virtual displacement principle, the virtual stress-momentum principle, the reciprocal theorems and the related theorems of time terminal conditions derived from it. The variational principles of potential energy action and complementary energy action, the H-W principles, the H-R principles and the constitutive variational principles for elastodynamics are obtained. Hamilton's principle, Toupin's work and the formulations of Ref. [5], [17]-[24] may be regarded as some special cases of the general principles given in the paper. By considering three cases: piecewise space-time domain, piecewise space domain, piecewise time domain, the piecewise variational principles including the potential, the complementary and the mixed energy action fashions are given. Finally, the general formulation of piecewise variational principles is derived. If the time dimension is not considered, the formulations obtained in the paper will become the corresponding ones for elastostatics.
