The power grid,as the hub connecting the power supply and consumption sides,plays an important role in achieving carbon neutrality in China.In emerging carbon markets,assessing the investment benefits of power-grid en...The power grid,as the hub connecting the power supply and consumption sides,plays an important role in achieving carbon neutrality in China.In emerging carbon markets,assessing the investment benefits of power-grid enterprises is essential.Thus,studying the impact of the carbon market on the investment and operation of powergrid enterprises is key to ensuring their efficient operation.Notably,few studies have examined the interaction between the carbon and electricity markets using system dynamics models,highlighting a research gap in this area.This study investigates the impact of the carbon market on the investment of power-grid enterprises using a novel evaluation system based on a system dynamics model that considers carbon-emissions from an established carbon-emission accounting model.First,an index system for benefit evaluation was constructed from six aspects:financing ability,economic benefit,reliability,social responsibility,user satisfaction,and carbon-emissions.A system dynamics model was then developed to reflect the causal feedback relationship between the impact of the carbon market on the investment and operation of power-grid enterprises.The simulation results of a provincial power-grid enterprise analyze comprehensive investment evaluation benefits over a 10-year period and the impact of carbon emissions on the investment and operation of power-grid enterprises.This study provides guidelines for the benign development of power-grid enterprises within the context of the carbon market.展开更多
The analytical formulations of the velocity and the acceleration of a 2-DOF spherical parallel mechanism are derived by the screw theory. Based on building its dynamics model by the principle of virtual work and recip...The analytical formulations of the velocity and the acceleration of a 2-DOF spherical parallel mechanism are derived by the screw theory. Based on building its dynamics model by the principle of virtual work and reciprocal product of the screw, the equation of the motor moment is obtained. Through the transformation of dynamics model, the configuration space method of the dynamics equation and the corresponding coefficients are presented. Finally, the result of an example shows that the inertia moment and the gravity play a more important role than the coriolis and centrifugal moment, and the former is ten times of the latter in the magnitude. So, the latter can be neglected only when the velocity of mechanism is very slow.展开更多
The particularity and practicality of harmony operations of close-coupling multiple helicopters indicate that the researches on it are urgent and necessary, Using the model that describes two hovering helicopters carr...The particularity and practicality of harmony operations of close-coupling multiple helicopters indicate that the researches on it are urgent and necessary, Using the model that describes two hovering helicopters carrying one heavy load, an inertia coordinate system and body coordinate systems of each sub-system are established. A nonlinear force model is established too. The equilibrium computation results can be regarded as the reference control inputs of the flight control system under hovering or low-speed flight condition. After the establishment of a translation kinematics model and a posture kinematics model, a coupling dynamics model of the multiple helicopter system is set up. The results can also be regarded as the base to analyze stabilization and design a controller for a close-coupling multiple helicopters harmony operation system.展开更多
The Baiyun sag is a deep one developing on the slope of the Pearl River Mouth Basin. It occurs as a composite graben horizontally, and is composed of two sub-sags versus one low uplift. Vertically, the sedimentary arc...The Baiyun sag is a deep one developing on the slope of the Pearl River Mouth Basin. It occurs as a composite graben horizontally, and is composed of two sub-sags versus one low uplift. Vertically, the sedimentary architecture could be divided into three layers, i.e. the faulted layer on the bottom, the faulted-ductile stretching layer in the middle and the draping layer on the top. The main rifting stage of the sag is supposed to be characterized by ductile extension and thinning of the crust. The special deformation pattern is probably attributed to the fact that the Baiyun sag is located in the transfer zone of the pre-existing weak zone, which made the sag a strongly deformed area, characterized by the greatly thinned lithosphere and active magmatism. The highly rising mantle under the Baiyun sag should be an important mechanism responsible for the ductile deformation, which caused partial melting of the upper mantle. Upweiling to the upper crust and the sedimentary layers, the partial melting materials accommodated extensional strain and caused non-faulted vertical subsidence. Magma was collected under the transfer zone after the first stage of rifting, and transferred laterally in a direction perpendicular to the extension to the ENE and WSW parts of the sag and upwelled along the NW-trending basal faults, where WNW-trending shear faults developed in swarms. The faulting activity and sedimentation history of the Baiyun sag may have been affected by the ocean ridge jump around 24 Ma and the cessation of sea floor spreading around 16 Ma.展开更多
In this paper, the node movement analysis of the levers of band saw tightening system is developed. A group of theoretical displacement and distortion equations of levers are presented using the Lagrange’s equation. ...In this paper, the node movement analysis of the levers of band saw tightening system is developed. A group of theoretical displacement and distortion equations of levers are presented using the Lagrange’s equation. This could be the basis for the future research in the field of band saw’s tightening system dynamics analysis.展开更多
Earthquake induced liquefaction is one of the main geo-disasters threating urban regions, which not only causes direct damages to buildings, but also delays both real-time disaster relief actions and reconstruction ac...Earthquake induced liquefaction is one of the main geo-disasters threating urban regions, which not only causes direct damages to buildings, but also delays both real-time disaster relief actions and reconstruction activities. It is thus important to assess liquefaction hazard of urban regions effectively and efficiently for disaster prevention and mitigation. Conventional assessment approaches rely on engineering indices such as the factor of safety(FS) against liquefaction, which cannot take into account directly the uncertainties of soils. In contrast, a physics simulation-based approach, by solving soil dynamics problems coupled with excess pore water pressure(EPWP) it is possible to model the uncertainties directly via Monte Carlo simulations. In this study, we demonstrate the capability of such an approach for assessing an urban region with over 10 000 sites. The permeability parameters are assumed to follow a base-10-lognormal distribution among 100 model analyses for each site. A dynamic simulation is conducted for each model analysis to obtain the EPWP results. Based on over 1 million EPWP analysis models, we obtained a probabilistic liquefaction assessment. Empowered by high performance computing, we present for the first time a probabilistic liquefaction hazard assessment for urban regions based on dynamics analysis, which consider soil uncertainties.展开更多
Swiss lever escapement is almost always used in all mechanical watches, which is one of the most critical com- ponents in a mechanical watch. However, its dynamics has not been fully studied. This paper presents a met...Swiss lever escapement is almost always used in all mechanical watches, which is one of the most critical com- ponents in a mechanical watch. However, its dynamics has not been fully studied. This paper presents a method for dy- namics analysis and simulation of the Swiss level escapement. First, the Swiss lever escapement mechanism is introduced and its motion in a half-period is divided into four sections. Then the dynamics model is developed using impulsive differ- ential equations and the simulation result is obtained by MATIAB. A watch called Seiko7OO9a is taken as an example. The simulation result shows the dynamic behavior in terms of the relationship among displacement, angle and time. The spring constant and balance wheel inertia that governed the timekeeping accuracy are also discussed.展开更多
The dynamic behavior of floating offshore wind turbine (FOWT) is crucial for its design and optimization. A novel dynamics analysis method for the spar-type FOWT system is proposed in this paper based on the theorem o...The dynamic behavior of floating offshore wind turbine (FOWT) is crucial for its design and optimization. A novel dynamics analysis method for the spar-type FOWT system is proposed in this paper based on the theorem of moment of momentum and the Newton’s second law. The full nonlinearity of the equations of motion (EOMs) and the full nonlinear coupling between external loads and the motions are preserved in this method. Compared with the conventional methods, this method is more transparent and it can be applied directly to the large-amplitude rotation cases. An in-house code is developed to implement this method. The capability of in-house code is verified by comparing its simulation results with those predicted by FAST. Based on the in-house code, the dynamic responses of a spar-type FOWT system are investigated under various conditions.展开更多
Accurate prediction of the offshore structure motion response and associate mooring line tension is important in both technical applications and scientific research. In our study, a truss spar platform, operated in Gu...Accurate prediction of the offshore structure motion response and associate mooring line tension is important in both technical applications and scientific research. In our study, a truss spar platform, operated in Gulf of Mexico, is numerically simulated and analyzed by an in-house numerical code ＇COUPLE＇. Both the platform motion responses and associated mooring line tension are calculated and investigated through a time domain nonlinear coupled dynamic analysis. Satisfactory agreement between the simulation and corresponding field measurements is in general reached, indicating that the numerical code can be used to conduct the time-domain analysis of a truss spar interacting with its mooting and riser system. Based on the comparison between linear and nonlinear results, the relative importance of nonlinearity in predicting the platform motion response and mooring line tensions is assessed and presented. Through the coupled and quasi-static analysis, the importance of the dynamic coupling effect between the platform hull and the mooting/riser system in predicting the mooting line tension and platform motions is quantified. These results may provide essential information pertaining to facilitate the numerical simulation and design of the large scale offshore structures.展开更多
The transverse cutting mechanism of the checkerboard paving robot, which directly affects the robot＇s operation, is regarded as the most important part in a transverse pavement system This research aims at designing ...The transverse cutting mechanism of the checkerboard paving robot, which directly affects the robot＇s operation, is regarded as the most important part in a transverse pavement system This research aims at designing a new system which is appropriate for desert wofidng en- vironments and finishing cutting the rope of straw. In this paper, computer emulating technology is applied, and with three-dimensional modeling by Pro/ENGINEER software, can observe whether or not interference exists. Also, the speed and displacement parameters of the main parts of the cutting system are given by the dynamic emulation by Automatic Dynamic Analysis of Mechanical System （ADAMS）, which theoretically assures the feasibility and appropriateness of the cutting mechanisrn~ Finally, results of the experinaent shows that the cutting mechanism can cut the straw strand as designed.展开更多
Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emp...Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emphasis on structural durability and monitoring is required.This study focuses on the mechanical vibrations that occur in rotary drilling systems,which have a substantial impact on the structural integrity of drilling equipment.The study specifically investigates axial,torsional,and lateral vibrations,which might lead to negative consequences such as bit-bounce,chaotic whirling,and high-frequency stick-slip.These events not only hinder the efficiency of drilling but also lead to exhaustion and harm to the system’s components since they are difficult to be detected and controlled in real time.The study investigates the dynamic interactions of these vibrations,specifically in their high-frequency modes,usingfield data obtained from measurement while drilling.Thefindings have demonstrated the effect of strong coupling between the high-frequency modes of these vibrations on drilling sys-tem performance.The obtained results highlight the importance of considering the interconnected impacts of these vibrations when designing and implementing robust control systems.Therefore,integrating these compo-nents can increase the durability of drill bits and drill strings,as well as improve the ability to monitor and detect damage.Moreover,by exploiting thesefindings,the assessment of structural resilience in rotary drilling systems can be enhanced.Furthermore,the study demonstrates the capacity of structural health monitoring to improve the quality,dependability,and efficiency of rotary drilling systems in the petroleum industry.展开更多
In this paper,a meshfree Jacobi point interpolation(MJPI)approach for the dynamic analysis of sandwich laminated conical and cylindrical shells with varying thickness is presented.The theoretical formulations for sand...In this paper,a meshfree Jacobi point interpolation(MJPI)approach for the dynamic analysis of sandwich laminated conical and cylindrical shells with varying thickness is presented.The theoretical formulations for sandwich laminated shells with varying thickness are established using the modified variational principle within the framework of first-order shear deformation theory(FSDT).The displacement components of the sandwich shell are expanded using the MJPI shape function and Fourier series in the meridional and circumferential directions,respectively.The accuracy and reliability of the proposed MJPI shape function are validated against numerical results from published literature and the commercial simulation tool Abaqus.Finally,the effects of different parameters such as thickness gradient,thickness power index and boundary condition on the free vibration and dynamic response of the sandwich laminated shell are investigated.展开更多
Current gas well decline analysis under boundary-dominated flow(BDF)is largely based on the Arps'empirical hyperbolic decline model and the analytical type curve tools associated with pseudo-functions.Due to the n...Current gas well decline analysis under boundary-dominated flow(BDF)is largely based on the Arps'empirical hyperbolic decline model and the analytical type curve tools associated with pseudo-functions.Due to the nonlinear flow behavior of natural gas,these analysis methods generally require iterative calculations.In this study,the dimensionless gas rate(qg/qgi)is introduced,and an explicit method to determine the average reservoir pressure and the original gas in place(OGIP)for a volumetric gas reservoir is proposed.We show that the dimensionless gas rate in the BDF is only the function of the gas PVT parameters and reservoir pressure.Step-by-step analysis procedures are presented that enable explicit and straightforward estimation of average reservoir pressure and OGIP by straight-line analysis.Compared with current techniques,this methodology avoids the iterative calculation of pseudo-time and pseudo-pressure functions,lowers the multiplicity of type curve analysis,and is applicable in different production situations(constant/variable gas flow rate,constant/variable bottom-hole pressure)with a broad range of applications and ease of use.Reservoir numerical simulation and field examples are thoroughly discussed to highlight the capabilities of the proposed approach.展开更多
The dynamics anMysis of recurrent neural networks （RNNs） is a first and necessary step for any practical applications of them. In the present paper, the easily verified theorem is found to ascertain the asymptotical...The dynamics anMysis of recurrent neural networks （RNNs） is a first and necessary step for any practical applications of them. In the present paper, the easily verified theorem is found to ascertain the asymptotical stability for generic RNN model with projection mapping under the critical condition that a discriminant matrix defined by the networks is semi-positive definite. The results given here not only improve deeply upon the existing relevant critical as well as non-critical dynamics conclusions in literature, but also can be used in the practical application of RNNs directly.展开更多
Lateral deformation of liquefiable soil is a cause of much damage during earthquakes, reportedly more than other forms of liquefaction-induced ground failures. Researchers have presented studies in which the liquefied...Lateral deformation of liquefiable soil is a cause of much damage during earthquakes, reportedly more than other forms of liquefaction-induced ground failures. Researchers have presented studies in which the liquefied soil is considered as viscous fluid. In this manner, the liquefied soil behaves as non-Newtonian fluid, whose viscosity decreases as the shear strain rate increases. The current study incorporates computational fluid dynamics to propose a simplified dynamic analysis for the liquefaction-induced lateral deformation of earth slopes. The numerical procedure involves a quasi-linear elastic model for small to moderate strains and a Bingham fluid model for large strain states during liquefaction. An iterative procedure is considered to estimate the strain-compatible shear stiffness of soil. The post-liquefaction residual strength of soil is considered as the initial Bingham viscosity. Performance of the numerical procedure is examined by using the results of centrifuge model and shaking table tests together with some field observations of lateral ground deformation. The results demonstrate that the proposed procedure predicts the time history of lateral ground deformation with a reasonable degree of precision.展开更多
Dynamic analysis of the tethered satellite system(TSS)can provide a fundamental guideline to the evaluation of performance and robust design of the system examined.Uncertainties inherited with the parameters would ind...Dynamic analysis of the tethered satellite system(TSS)can provide a fundamental guideline to the evaluation of performance and robust design of the system examined.Uncertainties inherited with the parameters would induce unexpected variation of the response and deteriorate the reliability of the system.In this work,the effect of uncertain mass of the satellites on the deployment and retrieval dynamics of the TSS is investigated.First the interval mode is employed to take the variation of mass of satellite into account in the processes of deployment and retrieval.Then,the Chebyshev interval method is used to obtain the lower and upper response bounds of the TSS.To achieve a smooth and reliable implementation of deployment and retrieval,the nonlinear programming based on the Gauss pseudospectral method is adopted to obtain optimal trajectory of tether velocity.Numerical results show that the uncertainties of mass of the satellites have a distinct influence on the response of tether tension in the processes of deployment and retrieval.展开更多
The clear identification and quantification of the factors affecting groundwater systems is crucial for protecting groundwater resources and ensuring safety in agricultural production.The Lower Yellow River(LYR)is a s...The clear identification and quantification of the factors affecting groundwater systems is crucial for protecting groundwater resources and ensuring safety in agricultural production.The Lower Yellow River(LYR)is a suspended river that replenishes groundwater continuously due to clear differences in the water head,especially in the Xinxiang section.Since its construction,the Xiaolangdi Reservoir has reversed the LYR’s deposition.To accurately determine the factors influencing the groundwater level(GWL),the study area was divided into five subzones based on hydrogeology.A dynamic factor model(DFM),variational mode decomposition(VMD),and a multiple linear regression model were used to identify and quantify the factors influencing the GWL.The impact of the suspended river on the groundwater before and after the construction of the Xiaolangdi Reservoir was examined.The results show that:(1)The rate of decrease in the GWL was 8.53×10^(–4)m/month,and the rate of decrease in the Yellow River water level(RWL)was 4.63×10^(–4)m/month.(2)Mountain front recharge(MFR)(scale=3 months)and precipitation(scale=9 months)were the dominant factors in subzones I and II,accounting for more than 40%of the fluctuation in the GWL.Subzone III was dominated by exploitation(scale=7 months)and precipitation(scale=12months),accounting for 28.43%,and 23.44%of changes in the GWL,respectively.In subzone IV,agricultural irrigation(scale=12 months)was the major factor,accounting for32.47%of GWL changes,while in subzone V,the RWL(scale=12 months)accounted for52.52%of these changes.(3)The Xiaolangdi Reservoir has increased the lateral seepage of the suspended river and altered the inter-annual distribution.The results of this study can provide a valuable reference for controlling groundwater overexploitation and ensuring water supply security.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
Electrodynamic tethered deorbit technology is a novel way to remove abandoned spacecrafts like upper stages or unusable satellites. This paper investigates and analyses the deorbit performance and mission applicabilit...Electrodynamic tethered deorbit technology is a novel way to remove abandoned spacecrafts like upper stages or unusable satellites. This paper investigates and analyses the deorbit performance and mission applicability of the electrodynamic tethered system. To do so, the electrodynamic tethered deorbit dynamics with multi-perturbation is firstly formulated, where the Earth magnetic field, the atmospheric drag, and the Earth oblateness effect are considered. Then, the key system parameters, including payload mass, tether length and tether type, are analyzed by numerical simulations to investigate their influences on the deorbit performance and to give the setting principles for choosing system parameters. Based on this and given an appropriate group of system parameters, numerical simulations are undertaken to study the impact of the mission parameters, including orbit height and orbit inclination, and thus to investigate the mission applicability of the electrodynamic tethered deorbit technology.展开更多
To find out and improve the flow characteristics inside the intake system of cylinder head,the application of computational fluid dynamics(CFD)in the evaluation and optimization of the reconstructed intake system base...To find out and improve the flow characteristics inside the intake system of cylinder head,the application of computational fluid dynamics(CFD)in the evaluation and optimization of the reconstructed intake system based on slicing reverse method was proposed.The flow characteristics were found out through CFD,and the velocity vector field,pressure field and turbulent kinetic energy field for different valve lifts were discussed,which were in good agreement with experimental data,and the quality of reconstruction was evaluated.In order to improve its flow characteristic,an optimization plan was proposed.The results show that the flow characteristics after optimization are obviously improved.The results can provide a reference for the design and optimization of the intake system of cylinder head.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52107087).
文摘The power grid,as the hub connecting the power supply and consumption sides,plays an important role in achieving carbon neutrality in China.In emerging carbon markets,assessing the investment benefits of power-grid enterprises is essential.Thus,studying the impact of the carbon market on the investment and operation of powergrid enterprises is key to ensuring their efficient operation.Notably,few studies have examined the interaction between the carbon and electricity markets using system dynamics models,highlighting a research gap in this area.This study investigates the impact of the carbon market on the investment of power-grid enterprises using a novel evaluation system based on a system dynamics model that considers carbon-emissions from an established carbon-emission accounting model.First,an index system for benefit evaluation was constructed from six aspects:financing ability,economic benefit,reliability,social responsibility,user satisfaction,and carbon-emissions.A system dynamics model was then developed to reflect the causal feedback relationship between the impact of the carbon market on the investment and operation of power-grid enterprises.The simulation results of a provincial power-grid enterprise analyze comprehensive investment evaluation benefits over a 10-year period and the impact of carbon emissions on the investment and operation of power-grid enterprises.This study provides guidelines for the benign development of power-grid enterprises within the context of the carbon market.
基金Supported by the National Natural Science Foundation of China (50375071)the Jiangsu Province Key Lab on Digital Manufacture Project (HGDML-0604)~~
文摘The analytical formulations of the velocity and the acceleration of a 2-DOF spherical parallel mechanism are derived by the screw theory. Based on building its dynamics model by the principle of virtual work and reciprocal product of the screw, the equation of the motor moment is obtained. Through the transformation of dynamics model, the configuration space method of the dynamics equation and the corresponding coefficients are presented. Finally, the result of an example shows that the inertia moment and the gravity play a more important role than the coriolis and centrifugal moment, and the former is ten times of the latter in the magnitude. So, the latter can be neglected only when the velocity of mechanism is very slow.
基金National Natural Science Foundation of China(60475039)
文摘The particularity and practicality of harmony operations of close-coupling multiple helicopters indicate that the researches on it are urgent and necessary, Using the model that describes two hovering helicopters carrying one heavy load, an inertia coordinate system and body coordinate systems of each sub-system are established. A nonlinear force model is established too. The equilibrium computation results can be regarded as the reference control inputs of the flight control system under hovering or low-speed flight condition. After the establishment of a translation kinematics model and a posture kinematics model, a coupling dynamics model of the multiple helicopter system is set up. The results can also be regarded as the base to analyze stabilization and design a controller for a close-coupling multiple helicopters harmony operation system.
文摘The Baiyun sag is a deep one developing on the slope of the Pearl River Mouth Basin. It occurs as a composite graben horizontally, and is composed of two sub-sags versus one low uplift. Vertically, the sedimentary architecture could be divided into three layers, i.e. the faulted layer on the bottom, the faulted-ductile stretching layer in the middle and the draping layer on the top. The main rifting stage of the sag is supposed to be characterized by ductile extension and thinning of the crust. The special deformation pattern is probably attributed to the fact that the Baiyun sag is located in the transfer zone of the pre-existing weak zone, which made the sag a strongly deformed area, characterized by the greatly thinned lithosphere and active magmatism. The highly rising mantle under the Baiyun sag should be an important mechanism responsible for the ductile deformation, which caused partial melting of the upper mantle. Upweiling to the upper crust and the sedimentary layers, the partial melting materials accommodated extensional strain and caused non-faulted vertical subsidence. Magma was collected under the transfer zone after the first stage of rifting, and transferred laterally in a direction perpendicular to the extension to the ENE and WSW parts of the sag and upwelled along the NW-trending basal faults, where WNW-trending shear faults developed in swarms. The faulting activity and sedimentation history of the Baiyun sag may have been affected by the ocean ridge jump around 24 Ma and the cessation of sea floor spreading around 16 Ma.
文摘In this paper, the node movement analysis of the levers of band saw tightening system is developed. A group of theoretical displacement and distortion equations of levers are presented using the Lagrange’s equation. This could be the basis for the future research in the field of band saw’s tightening system dynamics analysis.
基金This research was supported by the FOCUS Establishing Supercomputing Center of Excellence。
文摘Earthquake induced liquefaction is one of the main geo-disasters threating urban regions, which not only causes direct damages to buildings, but also delays both real-time disaster relief actions and reconstruction activities. It is thus important to assess liquefaction hazard of urban regions effectively and efficiently for disaster prevention and mitigation. Conventional assessment approaches rely on engineering indices such as the factor of safety(FS) against liquefaction, which cannot take into account directly the uncertainties of soils. In contrast, a physics simulation-based approach, by solving soil dynamics problems coupled with excess pore water pressure(EPWP) it is possible to model the uncertainties directly via Monte Carlo simulations. In this study, we demonstrate the capability of such an approach for assessing an urban region with over 10 000 sites. The permeability parameters are assumed to follow a base-10-lognormal distribution among 100 model analyses for each site. A dynamic simulation is conducted for each model analysis to obtain the EPWP results. Based on over 1 million EPWP analysis models, we obtained a probabilistic liquefaction assessment. Empowered by high performance computing, we present for the first time a probabilistic liquefaction hazard assessment for urban regions based on dynamics analysis, which consider soil uncertainties.
文摘Swiss lever escapement is almost always used in all mechanical watches, which is one of the most critical com- ponents in a mechanical watch. However, its dynamics has not been fully studied. This paper presents a method for dy- namics analysis and simulation of the Swiss level escapement. First, the Swiss lever escapement mechanism is introduced and its motion in a half-period is divided into four sections. Then the dynamics model is developed using impulsive differ- ential equations and the simulation result is obtained by MATIAB. A watch called Seiko7OO9a is taken as an example. The simulation result shows the dynamic behavior in terms of the relationship among displacement, angle and time. The spring constant and balance wheel inertia that governed the timekeeping accuracy are also discussed.
基金financially supported by the National Natural Science Foundation of China(Grant No.11632011)
文摘The dynamic behavior of floating offshore wind turbine (FOWT) is crucial for its design and optimization. A novel dynamics analysis method for the spar-type FOWT system is proposed in this paper based on the theorem of moment of momentum and the Newton’s second law. The full nonlinearity of the equations of motion (EOMs) and the full nonlinear coupling between external loads and the motions are preserved in this method. Compared with the conventional methods, this method is more transparent and it can be applied directly to the large-amplitude rotation cases. An in-house code is developed to implement this method. The capability of in-house code is verified by comparing its simulation results with those predicted by FAST. Based on the in-house code, the dynamic responses of a spar-type FOWT system are investigated under various conditions.
文摘Accurate prediction of the offshore structure motion response and associate mooring line tension is important in both technical applications and scientific research. In our study, a truss spar platform, operated in Gulf of Mexico, is numerically simulated and analyzed by an in-house numerical code ＇COUPLE＇. Both the platform motion responses and associated mooring line tension are calculated and investigated through a time domain nonlinear coupled dynamic analysis. Satisfactory agreement between the simulation and corresponding field measurements is in general reached, indicating that the numerical code can be used to conduct the time-domain analysis of a truss spar interacting with its mooting and riser system. Based on the comparison between linear and nonlinear results, the relative importance of nonlinearity in predicting the platform motion response and mooring line tensions is assessed and presented. Through the coupled and quasi-static analysis, the importance of the dynamic coupling effect between the platform hull and the mooting/riser system in predicting the mooting line tension and platform motions is quantified. These results may provide essential information pertaining to facilitate the numerical simulation and design of the large scale offshore structures.
基金supported by National High Technology Research and Development Program 863(Grant No.2002AA422170)the grant of Educational Commission of Heilongjiang Province of China(Grant No.10541042)
文摘The transverse cutting mechanism of the checkerboard paving robot, which directly affects the robot＇s operation, is regarded as the most important part in a transverse pavement system This research aims at designing a new system which is appropriate for desert wofidng en- vironments and finishing cutting the rope of straw. In this paper, computer emulating technology is applied, and with three-dimensional modeling by Pro/ENGINEER software, can observe whether or not interference exists. Also, the speed and displacement parameters of the main parts of the cutting system are given by the dynamic emulation by Automatic Dynamic Analysis of Mechanical System （ADAMS）, which theoretically assures the feasibility and appropriateness of the cutting mechanisrn~ Finally, results of the experinaent shows that the cutting mechanism can cut the straw strand as designed.
文摘Maintaining the integrity and longevity of structures is essential in many industries,such as aerospace,nuclear,and petroleum.To achieve the cost-effectiveness of large-scale systems in petroleum drilling,a strong emphasis on structural durability and monitoring is required.This study focuses on the mechanical vibrations that occur in rotary drilling systems,which have a substantial impact on the structural integrity of drilling equipment.The study specifically investigates axial,torsional,and lateral vibrations,which might lead to negative consequences such as bit-bounce,chaotic whirling,and high-frequency stick-slip.These events not only hinder the efficiency of drilling but also lead to exhaustion and harm to the system’s components since they are difficult to be detected and controlled in real time.The study investigates the dynamic interactions of these vibrations,specifically in their high-frequency modes,usingfield data obtained from measurement while drilling.Thefindings have demonstrated the effect of strong coupling between the high-frequency modes of these vibrations on drilling sys-tem performance.The obtained results highlight the importance of considering the interconnected impacts of these vibrations when designing and implementing robust control systems.Therefore,integrating these compo-nents can increase the durability of drill bits and drill strings,as well as improve the ability to monitor and detect damage.Moreover,by exploiting thesefindings,the assessment of structural resilience in rotary drilling systems can be enhanced.Furthermore,the study demonstrates the capacity of structural health monitoring to improve the quality,dependability,and efficiency of rotary drilling systems in the petroleum industry.
文摘In this paper,a meshfree Jacobi point interpolation(MJPI)approach for the dynamic analysis of sandwich laminated conical and cylindrical shells with varying thickness is presented.The theoretical formulations for sandwich laminated shells with varying thickness are established using the modified variational principle within the framework of first-order shear deformation theory(FSDT).The displacement components of the sandwich shell are expanded using the MJPI shape function and Fourier series in the meridional and circumferential directions,respectively.The accuracy and reliability of the proposed MJPI shape function are validated against numerical results from published literature and the commercial simulation tool Abaqus.Finally,the effects of different parameters such as thickness gradient,thickness power index and boundary condition on the free vibration and dynamic response of the sandwich laminated shell are investigated.
基金supported by the Young Elite Scientist Sponsorship Program by Beijing Association for Science and Technology,China(No.BYESS2023262)the Science Foundation of China University of Petroleum(Beijing),China(No.2462022BJRC004).
文摘Current gas well decline analysis under boundary-dominated flow(BDF)is largely based on the Arps'empirical hyperbolic decline model and the analytical type curve tools associated with pseudo-functions.Due to the nonlinear flow behavior of natural gas,these analysis methods generally require iterative calculations.In this study,the dimensionless gas rate(qg/qgi)is introduced,and an explicit method to determine the average reservoir pressure and the original gas in place(OGIP)for a volumetric gas reservoir is proposed.We show that the dimensionless gas rate in the BDF is only the function of the gas PVT parameters and reservoir pressure.Step-by-step analysis procedures are presented that enable explicit and straightforward estimation of average reservoir pressure and OGIP by straight-line analysis.Compared with current techniques,this methodology avoids the iterative calculation of pseudo-time and pseudo-pressure functions,lowers the multiplicity of type curve analysis,and is applicable in different production situations(constant/variable gas flow rate,constant/variable bottom-hole pressure)with a broad range of applications and ease of use.Reservoir numerical simulation and field examples are thoroughly discussed to highlight the capabilities of the proposed approach.
基金supported by the National Nature Science Foundation of China under Grant Nos.11101327,11471006,and 11171270the National Basic Research Program of China(973 Program)under Grant No.2013C13329406the Fundamental Research Funds for the Central Universities under Grant Nos.xjj20100087 and 2011jdhz30
文摘The dynamics anMysis of recurrent neural networks （RNNs） is a first and necessary step for any practical applications of them. In the present paper, the easily verified theorem is found to ascertain the asymptotical stability for generic RNN model with projection mapping under the critical condition that a discriminant matrix defined by the networks is semi-positive definite. The results given here not only improve deeply upon the existing relevant critical as well as non-critical dynamics conclusions in literature, but also can be used in the practical application of RNNs directly.
基金International Institute of Earthquake Engineering and Seismology(IIEES)under Grant No.AM-7/507-6 723-545
文摘Lateral deformation of liquefiable soil is a cause of much damage during earthquakes, reportedly more than other forms of liquefaction-induced ground failures. Researchers have presented studies in which the liquefied soil is considered as viscous fluid. In this manner, the liquefied soil behaves as non-Newtonian fluid, whose viscosity decreases as the shear strain rate increases. The current study incorporates computational fluid dynamics to propose a simplified dynamic analysis for the liquefaction-induced lateral deformation of earth slopes. The numerical procedure involves a quasi-linear elastic model for small to moderate strains and a Bingham fluid model for large strain states during liquefaction. An iterative procedure is considered to estimate the strain-compatible shear stiffness of soil. The post-liquefaction residual strength of soil is considered as the initial Bingham viscosity. Performance of the numerical procedure is examined by using the results of centrifuge model and shaking table tests together with some field observations of lateral ground deformation. The results demonstrate that the proposed procedure predicts the time history of lateral ground deformation with a reasonable degree of precision.
基金supported by the National Natural Science Foundation of China(Grant No.U21B2075)。
文摘Dynamic analysis of the tethered satellite system(TSS)can provide a fundamental guideline to the evaluation of performance and robust design of the system examined.Uncertainties inherited with the parameters would induce unexpected variation of the response and deteriorate the reliability of the system.In this work,the effect of uncertain mass of the satellites on the deployment and retrieval dynamics of the TSS is investigated.First the interval mode is employed to take the variation of mass of satellite into account in the processes of deployment and retrieval.Then,the Chebyshev interval method is used to obtain the lower and upper response bounds of the TSS.To achieve a smooth and reliable implementation of deployment and retrieval,the nonlinear programming based on the Gauss pseudospectral method is adopted to obtain optimal trajectory of tether velocity.Numerical results show that the uncertainties of mass of the satellites have a distinct influence on the response of tether tension in the processes of deployment and retrieval.
基金The Foundation of High-level Talents of Zhengzhou University,No.13432340370,No.134-32340364,No.135-32340122Project of the Ecological Environment Monitoring and Safety Center of Henan Province,No.SJCAQ-HT-2023-036。
文摘The clear identification and quantification of the factors affecting groundwater systems is crucial for protecting groundwater resources and ensuring safety in agricultural production.The Lower Yellow River(LYR)is a suspended river that replenishes groundwater continuously due to clear differences in the water head,especially in the Xinxiang section.Since its construction,the Xiaolangdi Reservoir has reversed the LYR’s deposition.To accurately determine the factors influencing the groundwater level(GWL),the study area was divided into five subzones based on hydrogeology.A dynamic factor model(DFM),variational mode decomposition(VMD),and a multiple linear regression model were used to identify and quantify the factors influencing the GWL.The impact of the suspended river on the groundwater before and after the construction of the Xiaolangdi Reservoir was examined.The results show that:(1)The rate of decrease in the GWL was 8.53×10^(–4)m/month,and the rate of decrease in the Yellow River water level(RWL)was 4.63×10^(–4)m/month.(2)Mountain front recharge(MFR)(scale=3 months)and precipitation(scale=9 months)were the dominant factors in subzones I and II,accounting for more than 40%of the fluctuation in the GWL.Subzone III was dominated by exploitation(scale=7 months)and precipitation(scale=12months),accounting for 28.43%,and 23.44%of changes in the GWL,respectively.In subzone IV,agricultural irrigation(scale=12 months)was the major factor,accounting for32.47%of GWL changes,while in subzone V,the RWL(scale=12 months)accounted for52.52%of these changes.(3)The Xiaolangdi Reservoir has increased the lateral seepage of the suspended river and altered the inter-annual distribution.The results of this study can provide a valuable reference for controlling groundwater overexploitation and ensuring water supply security.
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Electrodynamic tethered deorbit technology is a novel way to remove abandoned spacecrafts like upper stages or unusable satellites. This paper investigates and analyses the deorbit performance and mission applicability of the electrodynamic tethered system. To do so, the electrodynamic tethered deorbit dynamics with multi-perturbation is firstly formulated, where the Earth magnetic field, the atmospheric drag, and the Earth oblateness effect are considered. Then, the key system parameters, including payload mass, tether length and tether type, are analyzed by numerical simulations to investigate their influences on the deorbit performance and to give the setting principles for choosing system parameters. Based on this and given an appropriate group of system parameters, numerical simulations are undertaken to study the impact of the mission parameters, including orbit height and orbit inclination, and thus to investigate the mission applicability of the electrodynamic tethered deorbit technology.
基金“Strategic Cooperation of Science and Technology between Nanchong City and Southwest Petroleum University 2018” Special Fund Project,China(Nos.18SXHZ0030,18SXHZ0054)
文摘To find out and improve the flow characteristics inside the intake system of cylinder head,the application of computational fluid dynamics(CFD)in the evaluation and optimization of the reconstructed intake system based on slicing reverse method was proposed.The flow characteristics were found out through CFD,and the velocity vector field,pressure field and turbulent kinetic energy field for different valve lifts were discussed,which were in good agreement with experimental data,and the quality of reconstruction was evaluated.In order to improve its flow characteristic,an optimization plan was proposed.The results show that the flow characteristics after optimization are obviously improved.The results can provide a reference for the design and optimization of the intake system of cylinder head.
