In the realm of acoustic signal detection,the identification of weak signals,particularly in the presence of negative signal-to-noise ratios,poses a significant challenge.This challenge is further heightened when sign...In the realm of acoustic signal detection,the identification of weak signals,particularly in the presence of negative signal-to-noise ratios,poses a significant challenge.This challenge is further heightened when signals are acquired through fiber-optic hydrophones,as these signals often lack physical significance and resist clear systematic modeling.Conventional processing methods,e.g.,low-pass filter(LPF),require a thorough understanding of the effective signal bandwidth for noise reduction,and may introduce undesirable time lags.This paper introduces an innovative feedback control method with dual Kalman filters for the demodulation of phase signals with noises in fiber-optic hydrophones.A mathematical model of the closed-loop system is established to guide the design of the feedback control,aiming to achieve a balance with the input phase signal.The dual Kalman filters are instrumental in mitigating the effects of signal noise,observation noise,and control execution noise,thereby enabling precise estimation for the input phase signals.The effectiveness of this feedback control method is demonstrated through examples,showcasing the restoration of low-noise signals,negative signal-to-noise ratio signals,and multi-frequency signals.This research contributes to the technical advancement of high-performance devices,including fiber-optic hydrophones and phase-locked amplifiers.展开更多
Aiming at the time-optimal control problem of hypersonic vehicles(HSV)in ascending stage,a trigonometric regularization method(TRM)is introduced based on the indirect method of optimal control.This method avoids analy...Aiming at the time-optimal control problem of hypersonic vehicles(HSV)in ascending stage,a trigonometric regularization method(TRM)is introduced based on the indirect method of optimal control.This method avoids analyzing the switching function and distinguishing between singular control and bang-bang control,where the singular control problem is more complicated.While in bang-bang control,the costate variables are unsmooth due to the control jumping,resulting in difficulty in solving the two-point boundary value problem(TPBVP)induced by the indirect method.Aiming at the easy divergence when solving the TPBVP,the continuation method is introduced.This method uses the solution of the simplified problem as the initial value of the iteration.Then through solving a series of TPBVP,it approximates to the solution of the original complex problem.The calculation results show that through the above two methods,the time-optimal control problem of HSV in ascending stage under the complex model can be solved conveniently.展开更多
Compositional data, such as relative information, is a crucial aspect of machine learning and other related fields. It is typically recorded as closed data or sums to a constant, like 100%. The statistical linear mode...Compositional data, such as relative information, is a crucial aspect of machine learning and other related fields. It is typically recorded as closed data or sums to a constant, like 100%. The statistical linear model is the most used technique for identifying hidden relationships between underlying random variables of interest. However, data quality is a significant challenge in machine learning, especially when missing data is present. The linear regression model is a commonly used statistical modeling technique used in various applications to find relationships between variables of interest. When estimating linear regression parameters which are useful for things like future prediction and partial effects analysis of independent variables, maximum likelihood estimation (MLE) is the method of choice. However, many datasets contain missing observations, which can lead to costly and time-consuming data recovery. To address this issue, the expectation-maximization (EM) algorithm has been suggested as a solution for situations including missing data. The EM algorithm repeatedly finds the best estimates of parameters in statistical models that depend on variables or data that have not been observed. This is called maximum likelihood or maximum a posteriori (MAP). Using the present estimate as input, the expectation (E) step constructs a log-likelihood function. Finding the parameters that maximize the anticipated log-likelihood, as determined in the E step, is the job of the maximization (M) phase. This study looked at how well the EM algorithm worked on a made-up compositional dataset with missing observations. It used both the robust least square version and ordinary least square regression techniques. The efficacy of the EM algorithm was compared with two alternative imputation techniques, k-Nearest Neighbor (k-NN) and mean imputation (), in terms of Aitchison distances and covariance.展开更多
Based on the principle of transient perturbation analysis,in this paper,a method to objectively determine the weather pattern formed by sea fog is provided.On the basis of the classification results,the circulation si...Based on the principle of transient perturbation analysis,in this paper,a method to objectively determine the weather pattern formed by sea fog is provided.On the basis of the classification results,the circulation situation,divergence and vertical velocity field,and the vertical profile of temperature and humidity are synthesized and analyzed.The basic characteristics of the circulation and physical field of sea fog under low pressure control(L type sea fog)are obtained,and the results are compared with the sea fog under the control of high pressure(H type sea fog):a)L type sea fogs potential height anomaly disturbance is mainly manifested in the low layer,and its average value is-65.66 gpm,gradually weakening upward;b)L type sea fogs inversion structure is weaker than H type sea fogs when it occurs,the fog layer is thicker and the high relative humidity level is high over the fog layer,while the H type sea fogs fog layer has a relatively obvious dry layer;c)L sea fog has three layers of structure at the vertical direction.The first layer 1000-950 hPa is convergence accompanied by weak rise and subsidence,the second layer 950-850 hPa is divergence accompanied by weak subsidence,and the third layer 850 to 500hPa is gradually strengthened.While there are two layer structures of the H type sea fog.1000 hPa is divergence accompanied by weak rising and sinking movement,950-500 hPa is a uniform subsidence movement.d)Probability density statistical analysis further quantified the vertical movement of L and H type sea fog and the distribution of relative humidity in each layer.These conclusions provide an important reference for forecasting the sea fog in the northwest of the Yellow Sea under the condition of low pressure circulation in summer.展开更多
In this paper, the optimal control problem of parabolic integro-differential equations is solved by gradient recovery based two-grid finite element method. Piecewise linear functions are used to approximate state and ...In this paper, the optimal control problem of parabolic integro-differential equations is solved by gradient recovery based two-grid finite element method. Piecewise linear functions are used to approximate state and co-state variables, and piecewise constant function is used to approximate control variables. Generally, the optimal conditions for the problem are solved iteratively until the control variable reaches error tolerance. In order to calculate all the variables individually and parallelly, we introduce a gradient recovery based two-grid method. First, we solve the small scaled optimal control problem on coarse grids. Next, we use the gradient recovery technique to recover the gradients of state and co-state variables. Finally, using the recovered variables, we solve the large scaled optimal control problem for all variables independently. Moreover, we estimate priori error for the proposed scheme, and use an example to validate the theoretical results.展开更多
With the rapid development of China’s civil aviation industry,the teaching method of operating knowledge of flight principles has changed greatly,which creates a good implementation environment to improve the safety ...With the rapid development of China’s civil aviation industry,the teaching method of operating knowledge of flight principles has changed greatly,which creates a good implementation environment to improve the safety of civil aviation in our country.At present,the main training content of air route transport pilots in China is basic aviation theory,initial flight training,airline modification,etc.The principles of flight control are an important part of basic aviation theoretical knowledge training,which will involve a large number of flight technology training content,instructors will also be based on the pilot type.Teaching flight control theory and practical knowledge requires relatively high theoretical learning ability of students,and the learning effect of this part of theoretical knowledge will directly affect the quality of subsequent learning,but also directly affect the effectiveness of flight training.This paper focuses on the analysis of the basic concepts of flight control,studies the existing problems in the teaching of flight control principles,summarizes the teaching measures of flight control principles,aiming to provide a reference to teaching personnel.展开更多
With ongoing economic,scientific,and technological developments,the electronic devices used in daily lives are developing toward precision and miniaturization,and so the demand for high-precision manufacturing machine...With ongoing economic,scientific,and technological developments,the electronic devices used in daily lives are developing toward precision and miniaturization,and so the demand for high-precision manufacturing machinery is expanding.The most important piece of equipment in modern high-precision manufacturing is the macro-micro motion platform(M3P),which offers high speed,precision,and efficiency and has macro-micro motion coupling characteristics due to its mechanical design and composition of its driving components.Therefore,the design of the control system is crucial for the overall precision of the platform;conventional proportional–integral–derivative control cannot meet the system requirements,and so M3Ps are the subject of a growing range of modern control strategies.This paper begins by describing the development history of M3Ps,followed by their platform structure and motion control system components,and then in-depth assessments of the macro,micro,and macro-micro control systems.In addition to examining the advantages and disadvantages of current macro-micro motion control,recent technological breakthroughs are noted.Finally,based on existing problems,future directions for M3P control systems are given,and the present conclusions offer guidelines for future work on M3Ps.展开更多
The utilization of thin plate systems based on acoustic vibration holds significant importance in micro-nano manipulation and the exploration of nonlinear science. This paper focuses on the analysis of an actual thin ...The utilization of thin plate systems based on acoustic vibration holds significant importance in micro-nano manipulation and the exploration of nonlinear science. This paper focuses on the analysis of an actual thin plate system driven by acoustic wave signals. By combining the mechanical analysis of thin plate microelements with the Bubnov–Galerkin integral method, the governing equation for the forced vibration of a square thin plate is derived. Notably,the reaction force of the thin plate vibration system is defined as f=α|w|, resembling Hooke’s law. The energy function and energy level curve of the system are also analyzed. Subsequently, the amplitude–frequency response function of the thin plate oscillator is solved using the harmonic balance method. Through numerical simulations, the amplitude–frequency curves are analyzed for different vibration modes under the influence of various parameters. Furthermore, the paper demonstrates the occurrence of conservative chaotic motions in the thin plate oscillator using theoretical and numerical methods. Dynamics maps illustrating the system’s states are presented to reveal the evolution laws of the system. By exploring the effects of force fields and system energy, the underlying mechanism of chaos is interpreted. Additionally, the phenomenon of chaos in the oscillator can be controlled through the method of velocity and displacement states feedback, which holds significance for engineering applications.展开更多
As a direct wide bandgap semiconductor,CsPbCl_(3)has great potential applications in the eld of near-ultraviolet photodetectors,lasers and higher-order multiphoton uores-cent detectors.In this work,we synthesized CsPb...As a direct wide bandgap semiconductor,CsPbCl_(3)has great potential applications in the eld of near-ultraviolet photodetectors,lasers and higher-order multiphoton uores-cent detectors.In this work,we synthesized CsPbCl_(3)micro/nanocrystals by vapor depo-sition method with CsCl and PbCl_(2)powders as the source materials.It was con rmed that the formation of CsPbCl_(3)perovskite through the chemical reaction of CsCl with PbCl_(2)occurred in the quartz boat before the source evaporation,not in vapor or on sub-strate surface.The evaporated CsPbCl_(3)can form micro/nanocrystals on substrate surfaces under appropriate conditions.Various morphologies including irregular polyhedrons,rods and pyramids could be observed at lower temperature,while stable and uniform CsPbCl_(3)single crystal microplatelets were controllably synthesized at 450℃.Prolonging the growth time could modulate the size and density of the microcrystals,but could not change the morphology.Substrate types made little di erence to the morphology of CsPbCl_(3)crystals.The photoluminescence spectra indicated that the crystallinity and morphology of CsPbCl_(3)micro/nanocrystals have signi cant e ects on their optical properties.The work is expected to be helpful to the development of optoelectronic devices based on individual CsPbCl_(3)microcrystal.展开更多
5-amino-4-nitrobenzo[1,2-c:3,4-c']bis([1,2,5]oxadiazole)1,6-dioxide(CL-18)exhibits significant potential as an initiating explosive.However,its current synthesis process remains non-scalable due to low yields and ...5-amino-4-nitrobenzo[1,2-c:3,4-c']bis([1,2,5]oxadiazole)1,6-dioxide(CL-18)exhibits significant potential as an initiating explosive.However,its current synthesis process remains non-scalable due to low yields and safety risks.In this study,we have developed a simple and safe synthetic route for CL-18.It was synthesized from 3,5-dihaloanisole in a four-step reaction with an overall yield exceeding 60%,surpassing all reported yields in the literature.Subsequently,recrystallization of CL-18 was successfully achieved by carefully selecting appropriate solvents and antisolvents to reduce its mechanical sensitivity.Ultimately,when DMF-ethanol was employed as the recrystallization solvent system,satisfactory product yield(>90%)and reduced mechanical sensitivity(IS=15 J;FS=216 N)were obtained.Additionally,CL-18 is derived from the rearrangement of oxygen atoms on i-CL-18 furoxan,and a comparative analysis of their physicochemical properties was conducted.The thermal stability of both compounds is similar,with onset decomposition temperatures recorded at 186 and 182℃respectively.Similarly,they exhibit 5 s breaking point temperatures of 236 and 237℃.Additionally,we present novel insights into the positional-isomerization-laser-ignition performance of CL-18 and its isomer i-CL-18 using laser irradiation for the first time.Remarkably,our findings demonstrate that i-CL-18 exhibits enhanced laser sensitivity,as it can be directly ignited by a 1064 nm wavelength laser,whereas CL-18 lacks this characteristic.展开更多
With the ongoing advancements in sensor networks and data acquisition technologies across various systems like manufacturing,aviation,and healthcare,the data driven vibration control(DDVC)has attracted broad interests...With the ongoing advancements in sensor networks and data acquisition technologies across various systems like manufacturing,aviation,and healthcare,the data driven vibration control(DDVC)has attracted broad interests from both the industrial and academic communities.Input shaping(IS),as a simple and effective feedforward method,is greatly demanded in DDVC methods.It convolves the desired input command with impulse sequence without requiring parametric dynamics and the closed-loop system structure,thereby suppressing the residual vibration separately.Based on a thorough investigation into the state-of-the-art DDVC methods,this survey has made the following efforts:1)Introducing the IS theory and typical input shapers;2)Categorizing recent progress of DDVC methods;3)Summarizing commonly adopted metrics for DDVC;and 4)Discussing the engineering applications and future trends of DDVC.By doing so,this study provides a systematic and comprehensive overview of existing DDVC methods from designing to optimizing perspectives,aiming at promoting future research regarding this emerging and vital issue.展开更多
Due to high power density,high efficiency,and accurate control performance,permanent magnet synchronous motors(PMSMs)have been widely adopted in equipment manufacturing and energy transformation fields.To expand the s...Due to high power density,high efficiency,and accurate control performance,permanent magnet synchronous motors(PMSMs)have been widely adopted in equipment manufacturing and energy transformation fields.To expand the speed range under finite DC-bus voltage,extensive research on field weakening(FW)control strategies has been conducted.This paper summarizes the major FW control strategies of PMSMs,which are categorized into calculation-based methods,voltage closed-loop control methods,and model predictive control related methods.The existing strategies are analyzed and compared according to performance,robustness,and execution difficulty,which can facilitate the implementation of FW control.展开更多
This paper addresses the preassigned-time chaos control problem of memristor chaotic systems with time delays.Since the introduction of memristor,the presented models are nonlinear systems with chaotic dynamics.First,...This paper addresses the preassigned-time chaos control problem of memristor chaotic systems with time delays.Since the introduction of memristor,the presented models are nonlinear systems with chaotic dynamics.First,the TS fuzzy method is adopted to describe the chaotic systems.Then,a sliding-model-based control approach is proposed to achieve the preassigned-time stabilization of the presented models,where the upper bound of stabilization time can be arbitrarily specified in advance.Finally,simulation results demonstrate the validity of presented control approach and theoretic results.展开更多
This study investigates the aerodynamic performance of the NACA 633-421 airfoil and the effectiveness and feasibility of intermittent disturbance flow control methods on laminar separation bubbles(LSBs).It is found th...This study investigates the aerodynamic performance of the NACA 633-421 airfoil and the effectiveness and feasibility of intermittent disturbance flow control methods on laminar separation bubbles(LSBs).It is found that the average velocity and influence range of the synthetic jet actuator increase with the increasing of driving frequency and driving amplitude.LSB occurs at Re=1.0×10^(5),and ruptures atα=6°.But with intermittent disturbance control,the stall angle of attack(AoA)increases while significantly reducing drag.Research shows that although certain disturbance cannot fully recover from LSB stall,decreasing driving amplitude partially restores wing aerodynamic performance,more effectively than increasing driving amplitude.展开更多
This paper focuses on the stochastic analysis of a viscoelastic bistable energy harvesting system under colored noise and harmonic excitation, and adopts the time-delayed feedback control to improve its harvesting eff...This paper focuses on the stochastic analysis of a viscoelastic bistable energy harvesting system under colored noise and harmonic excitation, and adopts the time-delayed feedback control to improve its harvesting efficiency. Firstly, to obtain the dimensionless governing equation of the system, the original bistable system is approximated as a system without viscoelastic term by using the stochastic averaging method of energy envelope, and then is further decoupled to derive an equivalent system. The credibility of the proposed method is validated by contrasting the consistency between the numerical and the analytical results of the equivalent system under different noise conditions. The influence of system parameters on average output power is analyzed, and the control effect of the time-delayed feedback control on system performance is compared. The output performance of the system is improved with the occurrence of stochastic resonance(SR). Therefore, the signal-to-noise ratio expression for measuring SR is derived, and the dependence of its SR behavior on different parameters is explored.展开更多
The instability of slope blocks occurred frequently along traffic corridor in Southeastern Tibet(TCST),which was primarily controlled by the rock mass structures.A rapid method evaluating the control effects of rock m...The instability of slope blocks occurred frequently along traffic corridor in Southeastern Tibet(TCST),which was primarily controlled by the rock mass structures.A rapid method evaluating the control effects of rock mass structures was proposed through field statistics of the slopes and rock mass structures along TCST,which combined the stereographic projection method,modified M-JCS model,and limit equilibrium theory.The instabilities of slope blocks along TCST were then evaluated rapidly,and the different control factors of instability were analyzed.Results showed that the probabilities of toppling(5.31%),planar(16.15%),and wedge(35.37%)failure of slope blocks along TCST increased sequentially.These instability modes were respectively controlled by the anti-dip joint,the joint parallel to slope surface with a dip angle smaller than the slope angle(singlejoint),and two groups of joints inclined out of the slope(double-joints).Regarding the control effects on slope block instability,the stabilization ability of doublejoints(72.7%),anti-dip joint(67.4%),and single-joint(57.6%)decreased sequentially,resulting in different probabilities of slope block instability.Additionally,nearby regional faults significantly influenced the joints,leading to spatial heterogeneity and segmental clustering in the stabilization ability provided by joints to the slope blocks.Consequently,the stability of slope blocks gradually weakened as they approached the fault zones.This paper can provide guidance and assistance for investigating the development characteristics of rock mass structures and the stability of slope blocks.展开更多
Linear temporal logic(LTL)is an intuitive and expressive language to specify complex control tasks,and how to design an efficient control strategy for LTL specification is still a challenge.In this paper,we implement ...Linear temporal logic(LTL)is an intuitive and expressive language to specify complex control tasks,and how to design an efficient control strategy for LTL specification is still a challenge.In this paper,we implement the dynamic quantization technique to propose a novel hierarchical control strategy for nonlinear control systems under LTL specifications.Based on the regions of interest involved in the LTL formula,an accepting path is derived first to provide a high-level solution for the controller synthesis problem.Second,we develop a dynamic quantization based approach to verify the realization of the accepting path.The realization verification results in the necessity of the controller design and a sequence of quantization regions for the controller design.Third,the techniques of dynamic quantization and abstraction-based control are combined together to establish the local-to-global control strategy.Both abstraction construction and controller design are local and dynamic,thereby resulting in the potential reduction of the computational complexity.Since each quantization region can be considered locally and individually,the proposed hierarchical mechanism is more efficient and can solve much larger problems than many existing methods.Finally,the proposed control strategy is illustrated via two examples from the path planning and tracking problems of mobile robots.展开更多
Synthetic aperture radar(SAR)and wave spectrometers,crucial in microwave remote sensing,play an essential role in monitoring sea surface wind and wave conditions.However,they face inherent limitations in observing sea...Synthetic aperture radar(SAR)and wave spectrometers,crucial in microwave remote sensing,play an essential role in monitoring sea surface wind and wave conditions.However,they face inherent limitations in observing sea surface phenomena.SAR systems,for instance,are hindered by an azimuth cut-off phenomenon in sea surface wind field observation.Wave spectrometers,while unaffected by the azimuth cutoff phenomenon,struggle with low azimuth resolution,impacting the capture of detailed wave and wind field data.This study utilizes SAR and surface wave investigation and monitoring(SWIM)data to initially extract key feature parameters,which are then prioritized using the extreme gradient boosting(XGBoost)algorithm.The research further addresses feature collinearity through a combined analysis of feature importance and correlation,leading to the development of an inversion model for wave and wind parameters based on XGBoost.A comparative analysis of this model with ERA5 reanalysis and buoy data for of significant wave height,mean wave period,wind direction,and wind speed reveals root mean square errors of 0.212 m,0.525 s,27.446°,and 1.092 m/s,compared to 0.314 m,0.888 s,27.698°,and 1.315 m/s from buoy data,respectively.These results demonstrate the model’s effective retrieval of wave and wind parameters.Finally,the model,incorporating altimeter and scatterometer data,is evaluated against SAR/SWIM single and dual payload inversion methods across different wind speeds.This comparison highlights the model’s superior inversion accuracy over other methods.展开更多
Offshore carbon dioxide(CO_(2)) storage is an effective method for reducing greenhouse gas emissions. However, when using traditional seismic wave methods to monitor the migration of sequestration CO_(2) plumes, the c...Offshore carbon dioxide(CO_(2)) storage is an effective method for reducing greenhouse gas emissions. However, when using traditional seismic wave methods to monitor the migration of sequestration CO_(2) plumes, the characteristics of wave velocity changes tend to become insignificant beyond a certain limit. In contrast, the controllable source electromagnetic method(CSEM) remains highly sensitive to resistivity changes. By simulating different CO_(2) plume migration conditions, we established the relevant models and calculated the corresponding electric field response characteristic curves, allowing us to analyze the CSEM's ability to monitor CO_(2) plumes. We considered potential scenarios for the migration and diffusion of offshore CO_(2) storage, including various burial depths, vertical extension diffusion, lateral extension diffusion,multiple combinations of lateral intervals, and electric field components. We also obtained differences in resistivity inversion imaging obtained by CSEM to evaluate its feasibility in monitoring and to analyze all the electric field(Ex, Ey, and Ez) response characteristics. CSEM has great potential in monitoring CO_(2) plume migration in offshore saltwater reservoirs due to its high sensitivity and accuracy. Furthermore, changes in electromagnetic field response reflect the transport status of CO_(2) plumes, providing an important basis for monitoring and evaluating CO_(2)transport behavior during storage processes.展开更多
Synthetic biology is a new frontier of life science,which aims to design,transform and even synthesize organisms with engineering design concept.Doing a good job in the teaching of"synthetic biology"is of gr...Synthetic biology is a new frontier of life science,which aims to design,transform and even synthesize organisms with engineering design concept.Doing a good job in the teaching of"synthetic biology"is of great significance to the cultivation and reserve of biotechnology professionals in China,and also has an important impact on students' employment competitiveness.Under the background of"new engineering",the course reform of"synthetic biology"was carried out in terms of the construction of teaching staff,teaching methods,students' participation and the innovation of course content,and specific reform suggestions were put forward,hoping to effectively promote the sustainable development of"synthetic biology"and effectively improve the quality of education.展开更多
基金Project supported by the National Key Research and Development Program of China(No.2022YFB3203600)the National Natural Science Foundation of China(Nos.12172323,12132013+1 种基金12332003)the Zhejiang Provincial Natural Science Foundation of China(No.LZ22A020003)。
文摘In the realm of acoustic signal detection,the identification of weak signals,particularly in the presence of negative signal-to-noise ratios,poses a significant challenge.This challenge is further heightened when signals are acquired through fiber-optic hydrophones,as these signals often lack physical significance and resist clear systematic modeling.Conventional processing methods,e.g.,low-pass filter(LPF),require a thorough understanding of the effective signal bandwidth for noise reduction,and may introduce undesirable time lags.This paper introduces an innovative feedback control method with dual Kalman filters for the demodulation of phase signals with noises in fiber-optic hydrophones.A mathematical model of the closed-loop system is established to guide the design of the feedback control,aiming to achieve a balance with the input phase signal.The dual Kalman filters are instrumental in mitigating the effects of signal noise,observation noise,and control execution noise,thereby enabling precise estimation for the input phase signals.The effectiveness of this feedback control method is demonstrated through examples,showcasing the restoration of low-noise signals,negative signal-to-noise ratio signals,and multi-frequency signals.This research contributes to the technical advancement of high-performance devices,including fiber-optic hydrophones and phase-locked amplifiers.
基金supported by the Na-tional Natural Science Foundation of China(No.52272369).
文摘Aiming at the time-optimal control problem of hypersonic vehicles(HSV)in ascending stage,a trigonometric regularization method(TRM)is introduced based on the indirect method of optimal control.This method avoids analyzing the switching function and distinguishing between singular control and bang-bang control,where the singular control problem is more complicated.While in bang-bang control,the costate variables are unsmooth due to the control jumping,resulting in difficulty in solving the two-point boundary value problem(TPBVP)induced by the indirect method.Aiming at the easy divergence when solving the TPBVP,the continuation method is introduced.This method uses the solution of the simplified problem as the initial value of the iteration.Then through solving a series of TPBVP,it approximates to the solution of the original complex problem.The calculation results show that through the above two methods,the time-optimal control problem of HSV in ascending stage under the complex model can be solved conveniently.
文摘Compositional data, such as relative information, is a crucial aspect of machine learning and other related fields. It is typically recorded as closed data or sums to a constant, like 100%. The statistical linear model is the most used technique for identifying hidden relationships between underlying random variables of interest. However, data quality is a significant challenge in machine learning, especially when missing data is present. The linear regression model is a commonly used statistical modeling technique used in various applications to find relationships between variables of interest. When estimating linear regression parameters which are useful for things like future prediction and partial effects analysis of independent variables, maximum likelihood estimation (MLE) is the method of choice. However, many datasets contain missing observations, which can lead to costly and time-consuming data recovery. To address this issue, the expectation-maximization (EM) algorithm has been suggested as a solution for situations including missing data. The EM algorithm repeatedly finds the best estimates of parameters in statistical models that depend on variables or data that have not been observed. This is called maximum likelihood or maximum a posteriori (MAP). Using the present estimate as input, the expectation (E) step constructs a log-likelihood function. Finding the parameters that maximize the anticipated log-likelihood, as determined in the E step, is the job of the maximization (M) phase. This study looked at how well the EM algorithm worked on a made-up compositional dataset with missing observations. It used both the robust least square version and ordinary least square regression techniques. The efficacy of the EM algorithm was compared with two alternative imputation techniques, k-Nearest Neighbor (k-NN) and mean imputation (), in terms of Aitchison distances and covariance.
基金supported by National Natural Science Foundation of China(No.41576108 and No.41605006)Natural Science Foundation project of Shandong Province(No.ZR2016DB26).
文摘Based on the principle of transient perturbation analysis,in this paper,a method to objectively determine the weather pattern formed by sea fog is provided.On the basis of the classification results,the circulation situation,divergence and vertical velocity field,and the vertical profile of temperature and humidity are synthesized and analyzed.The basic characteristics of the circulation and physical field of sea fog under low pressure control(L type sea fog)are obtained,and the results are compared with the sea fog under the control of high pressure(H type sea fog):a)L type sea fogs potential height anomaly disturbance is mainly manifested in the low layer,and its average value is-65.66 gpm,gradually weakening upward;b)L type sea fogs inversion structure is weaker than H type sea fogs when it occurs,the fog layer is thicker and the high relative humidity level is high over the fog layer,while the H type sea fogs fog layer has a relatively obvious dry layer;c)L sea fog has three layers of structure at the vertical direction.The first layer 1000-950 hPa is convergence accompanied by weak rise and subsidence,the second layer 950-850 hPa is divergence accompanied by weak subsidence,and the third layer 850 to 500hPa is gradually strengthened.While there are two layer structures of the H type sea fog.1000 hPa is divergence accompanied by weak rising and sinking movement,950-500 hPa is a uniform subsidence movement.d)Probability density statistical analysis further quantified the vertical movement of L and H type sea fog and the distribution of relative humidity in each layer.These conclusions provide an important reference for forecasting the sea fog in the northwest of the Yellow Sea under the condition of low pressure circulation in summer.
文摘In this paper, the optimal control problem of parabolic integro-differential equations is solved by gradient recovery based two-grid finite element method. Piecewise linear functions are used to approximate state and co-state variables, and piecewise constant function is used to approximate control variables. Generally, the optimal conditions for the problem are solved iteratively until the control variable reaches error tolerance. In order to calculate all the variables individually and parallelly, we introduce a gradient recovery based two-grid method. First, we solve the small scaled optimal control problem on coarse grids. Next, we use the gradient recovery technique to recover the gradients of state and co-state variables. Finally, using the recovered variables, we solve the large scaled optimal control problem for all variables independently. Moreover, we estimate priori error for the proposed scheme, and use an example to validate the theoretical results.
文摘With the rapid development of China’s civil aviation industry,the teaching method of operating knowledge of flight principles has changed greatly,which creates a good implementation environment to improve the safety of civil aviation in our country.At present,the main training content of air route transport pilots in China is basic aviation theory,initial flight training,airline modification,etc.The principles of flight control are an important part of basic aviation theoretical knowledge training,which will involve a large number of flight technology training content,instructors will also be based on the pilot type.Teaching flight control theory and practical knowledge requires relatively high theoretical learning ability of students,and the learning effect of this part of theoretical knowledge will directly affect the quality of subsequent learning,but also directly affect the effectiveness of flight training.This paper focuses on the analysis of the basic concepts of flight control,studies the existing problems in the teaching of flight control principles,summarizes the teaching measures of flight control principles,aiming to provide a reference to teaching personnel.
基金This research was supported financially by the China Postdoctoral Science Foundation,the National Natural Science Foundation of China(Grant No.51705132)the Young Backbone Teacher Training Program in Henan University of Technology,the Education Department of Henan Province Natural Science Project(Grant No.21A460006)the Natural Science Project of Henan Provincial Department of Science and Technology(Grant No.222102220088).
文摘With ongoing economic,scientific,and technological developments,the electronic devices used in daily lives are developing toward precision and miniaturization,and so the demand for high-precision manufacturing machinery is expanding.The most important piece of equipment in modern high-precision manufacturing is the macro-micro motion platform(M3P),which offers high speed,precision,and efficiency and has macro-micro motion coupling characteristics due to its mechanical design and composition of its driving components.Therefore,the design of the control system is crucial for the overall precision of the platform;conventional proportional–integral–derivative control cannot meet the system requirements,and so M3Ps are the subject of a growing range of modern control strategies.This paper begins by describing the development history of M3Ps,followed by their platform structure and motion control system components,and then in-depth assessments of the macro,micro,and macro-micro control systems.In addition to examining the advantages and disadvantages of current macro-micro motion control,recent technological breakthroughs are noted.Finally,based on existing problems,future directions for M3P control systems are given,and the present conclusions offer guidelines for future work on M3Ps.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61973172, 62003177, 62103204, 62003175, and 61973175)the Joint Fund of the Ministry of Education for Equipment Pre-research (Grant No. 8091B022133)General Terminal IC Interdisciplinary Science Center of Nankai University。
文摘The utilization of thin plate systems based on acoustic vibration holds significant importance in micro-nano manipulation and the exploration of nonlinear science. This paper focuses on the analysis of an actual thin plate system driven by acoustic wave signals. By combining the mechanical analysis of thin plate microelements with the Bubnov–Galerkin integral method, the governing equation for the forced vibration of a square thin plate is derived. Notably,the reaction force of the thin plate vibration system is defined as f=α|w|, resembling Hooke’s law. The energy function and energy level curve of the system are also analyzed. Subsequently, the amplitude–frequency response function of the thin plate oscillator is solved using the harmonic balance method. Through numerical simulations, the amplitude–frequency curves are analyzed for different vibration modes under the influence of various parameters. Furthermore, the paper demonstrates the occurrence of conservative chaotic motions in the thin plate oscillator using theoretical and numerical methods. Dynamics maps illustrating the system’s states are presented to reveal the evolution laws of the system. By exploring the effects of force fields and system energy, the underlying mechanism of chaos is interpreted. Additionally, the phenomenon of chaos in the oscillator can be controlled through the method of velocity and displacement states feedback, which holds significance for engineering applications.
基金supported by the National Natu-ral Science Foundation of China(No.11575187)the National Key Research and Development Program(No.2016YFB0700205).
文摘As a direct wide bandgap semiconductor,CsPbCl_(3)has great potential applications in the eld of near-ultraviolet photodetectors,lasers and higher-order multiphoton uores-cent detectors.In this work,we synthesized CsPbCl_(3)micro/nanocrystals by vapor depo-sition method with CsCl and PbCl_(2)powders as the source materials.It was con rmed that the formation of CsPbCl_(3)perovskite through the chemical reaction of CsCl with PbCl_(2)occurred in the quartz boat before the source evaporation,not in vapor or on sub-strate surface.The evaporated CsPbCl_(3)can form micro/nanocrystals on substrate surfaces under appropriate conditions.Various morphologies including irregular polyhedrons,rods and pyramids could be observed at lower temperature,while stable and uniform CsPbCl_(3)single crystal microplatelets were controllably synthesized at 450℃.Prolonging the growth time could modulate the size and density of the microcrystals,but could not change the morphology.Substrate types made little di erence to the morphology of CsPbCl_(3)crystals.The photoluminescence spectra indicated that the crystallinity and morphology of CsPbCl_(3)micro/nanocrystals have signi cant e ects on their optical properties.The work is expected to be helpful to the development of optoelectronic devices based on individual CsPbCl_(3)microcrystal.
基金support from the National Natural Science Foundation of China(Grant No.22175160)the Science Challenge Project(Grant No.TZ2018004)。
文摘5-amino-4-nitrobenzo[1,2-c:3,4-c']bis([1,2,5]oxadiazole)1,6-dioxide(CL-18)exhibits significant potential as an initiating explosive.However,its current synthesis process remains non-scalable due to low yields and safety risks.In this study,we have developed a simple and safe synthetic route for CL-18.It was synthesized from 3,5-dihaloanisole in a four-step reaction with an overall yield exceeding 60%,surpassing all reported yields in the literature.Subsequently,recrystallization of CL-18 was successfully achieved by carefully selecting appropriate solvents and antisolvents to reduce its mechanical sensitivity.Ultimately,when DMF-ethanol was employed as the recrystallization solvent system,satisfactory product yield(>90%)and reduced mechanical sensitivity(IS=15 J;FS=216 N)were obtained.Additionally,CL-18 is derived from the rearrangement of oxygen atoms on i-CL-18 furoxan,and a comparative analysis of their physicochemical properties was conducted.The thermal stability of both compounds is similar,with onset decomposition temperatures recorded at 186 and 182℃respectively.Similarly,they exhibit 5 s breaking point temperatures of 236 and 237℃.Additionally,we present novel insights into the positional-isomerization-laser-ignition performance of CL-18 and its isomer i-CL-18 using laser irradiation for the first time.Remarkably,our findings demonstrate that i-CL-18 exhibits enhanced laser sensitivity,as it can be directly ignited by a 1064 nm wavelength laser,whereas CL-18 lacks this characteristic.
基金supported by the National Natural Science Foundation of China (62272078)。
文摘With the ongoing advancements in sensor networks and data acquisition technologies across various systems like manufacturing,aviation,and healthcare,the data driven vibration control(DDVC)has attracted broad interests from both the industrial and academic communities.Input shaping(IS),as a simple and effective feedforward method,is greatly demanded in DDVC methods.It convolves the desired input command with impulse sequence without requiring parametric dynamics and the closed-loop system structure,thereby suppressing the residual vibration separately.Based on a thorough investigation into the state-of-the-art DDVC methods,this survey has made the following efforts:1)Introducing the IS theory and typical input shapers;2)Categorizing recent progress of DDVC methods;3)Summarizing commonly adopted metrics for DDVC;and 4)Discussing the engineering applications and future trends of DDVC.By doing so,this study provides a systematic and comprehensive overview of existing DDVC methods from designing to optimizing perspectives,aiming at promoting future research regarding this emerging and vital issue.
基金supported by the Research Fund for the National Natural Science Foundation of China(52125701).
文摘Due to high power density,high efficiency,and accurate control performance,permanent magnet synchronous motors(PMSMs)have been widely adopted in equipment manufacturing and energy transformation fields.To expand the speed range under finite DC-bus voltage,extensive research on field weakening(FW)control strategies has been conducted.This paper summarizes the major FW control strategies of PMSMs,which are categorized into calculation-based methods,voltage closed-loop control methods,and model predictive control related methods.The existing strategies are analyzed and compared according to performance,robustness,and execution difficulty,which can facilitate the implementation of FW control.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62473348 and 62076229)the Knowledge Innovation Program of Wuhan-Basic Research(Grant No.2023010201010101).
文摘This paper addresses the preassigned-time chaos control problem of memristor chaotic systems with time delays.Since the introduction of memristor,the presented models are nonlinear systems with chaotic dynamics.First,the TS fuzzy method is adopted to describe the chaotic systems.Then,a sliding-model-based control approach is proposed to achieve the preassigned-time stabilization of the presented models,where the upper bound of stabilization time can be arbitrarily specified in advance.Finally,simulation results demonstrate the validity of presented control approach and theoretic results.
文摘This study investigates the aerodynamic performance of the NACA 633-421 airfoil and the effectiveness and feasibility of intermittent disturbance flow control methods on laminar separation bubbles(LSBs).It is found that the average velocity and influence range of the synthetic jet actuator increase with the increasing of driving frequency and driving amplitude.LSB occurs at Re=1.0×10^(5),and ruptures atα=6°.But with intermittent disturbance control,the stall angle of attack(AoA)increases while significantly reducing drag.Research shows that although certain disturbance cannot fully recover from LSB stall,decreasing driving amplitude partially restores wing aerodynamic performance,more effectively than increasing driving amplitude.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11902081)the Science and Technology Projects of Guangzhou (Grant No. 202201010326)the Guangdong Provincial Basic and Applied Basic Research Foundation (Grant No. 2023A1515010833)。
文摘This paper focuses on the stochastic analysis of a viscoelastic bistable energy harvesting system under colored noise and harmonic excitation, and adopts the time-delayed feedback control to improve its harvesting efficiency. Firstly, to obtain the dimensionless governing equation of the system, the original bistable system is approximated as a system without viscoelastic term by using the stochastic averaging method of energy envelope, and then is further decoupled to derive an equivalent system. The credibility of the proposed method is validated by contrasting the consistency between the numerical and the analytical results of the equivalent system under different noise conditions. The influence of system parameters on average output power is analyzed, and the control effect of the time-delayed feedback control on system performance is compared. The output performance of the system is improved with the occurrence of stochastic resonance(SR). Therefore, the signal-to-noise ratio expression for measuring SR is derived, and the dependence of its SR behavior on different parameters is explored.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41941019,42177142)the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(Grant NO.2019QZKK0904)the Fundamental Research Funds for the Central Universities,CHD(Grant No.300102212213).
文摘The instability of slope blocks occurred frequently along traffic corridor in Southeastern Tibet(TCST),which was primarily controlled by the rock mass structures.A rapid method evaluating the control effects of rock mass structures was proposed through field statistics of the slopes and rock mass structures along TCST,which combined the stereographic projection method,modified M-JCS model,and limit equilibrium theory.The instabilities of slope blocks along TCST were then evaluated rapidly,and the different control factors of instability were analyzed.Results showed that the probabilities of toppling(5.31%),planar(16.15%),and wedge(35.37%)failure of slope blocks along TCST increased sequentially.These instability modes were respectively controlled by the anti-dip joint,the joint parallel to slope surface with a dip angle smaller than the slope angle(singlejoint),and two groups of joints inclined out of the slope(double-joints).Regarding the control effects on slope block instability,the stabilization ability of doublejoints(72.7%),anti-dip joint(67.4%),and single-joint(57.6%)decreased sequentially,resulting in different probabilities of slope block instability.Additionally,nearby regional faults significantly influenced the joints,leading to spatial heterogeneity and segmental clustering in the stabilization ability provided by joints to the slope blocks.Consequently,the stability of slope blocks gradually weakened as they approached the fault zones.This paper can provide guidance and assistance for investigating the development characteristics of rock mass structures and the stability of slope blocks.
基金supported by the Fundamental Research Funds for the Central Universities(DUT22RT(3)090)the National Natural Science Foundation of China(61890920,61890921,62122016,08120003)Liaoning Science and Technology Program(2023JH2/101700361).
文摘Linear temporal logic(LTL)is an intuitive and expressive language to specify complex control tasks,and how to design an efficient control strategy for LTL specification is still a challenge.In this paper,we implement the dynamic quantization technique to propose a novel hierarchical control strategy for nonlinear control systems under LTL specifications.Based on the regions of interest involved in the LTL formula,an accepting path is derived first to provide a high-level solution for the controller synthesis problem.Second,we develop a dynamic quantization based approach to verify the realization of the accepting path.The realization verification results in the necessity of the controller design and a sequence of quantization regions for the controller design.Third,the techniques of dynamic quantization and abstraction-based control are combined together to establish the local-to-global control strategy.Both abstraction construction and controller design are local and dynamic,thereby resulting in the potential reduction of the computational complexity.Since each quantization region can be considered locally and individually,the proposed hierarchical mechanism is more efficient and can solve much larger problems than many existing methods.Finally,the proposed control strategy is illustrated via two examples from the path planning and tracking problems of mobile robots.
基金The project supported by Key Laboratory of Space Ocean Remote Sensing and Application,Ministry of Natural Resources under contract No.2023CFO016the National Natural Science Foundation of China under contract No.61931025+1 种基金the Innovation Fund Project for Graduate Student of China University of Petroleum(East China)the Fundamental Research Funds for the Central Universities under contract No.23CX04042A.
文摘Synthetic aperture radar(SAR)and wave spectrometers,crucial in microwave remote sensing,play an essential role in monitoring sea surface wind and wave conditions.However,they face inherent limitations in observing sea surface phenomena.SAR systems,for instance,are hindered by an azimuth cut-off phenomenon in sea surface wind field observation.Wave spectrometers,while unaffected by the azimuth cutoff phenomenon,struggle with low azimuth resolution,impacting the capture of detailed wave and wind field data.This study utilizes SAR and surface wave investigation and monitoring(SWIM)data to initially extract key feature parameters,which are then prioritized using the extreme gradient boosting(XGBoost)algorithm.The research further addresses feature collinearity through a combined analysis of feature importance and correlation,leading to the development of an inversion model for wave and wind parameters based on XGBoost.A comparative analysis of this model with ERA5 reanalysis and buoy data for of significant wave height,mean wave period,wind direction,and wind speed reveals root mean square errors of 0.212 m,0.525 s,27.446°,and 1.092 m/s,compared to 0.314 m,0.888 s,27.698°,and 1.315 m/s from buoy data,respectively.These results demonstrate the model’s effective retrieval of wave and wind parameters.Finally,the model,incorporating altimeter and scatterometer data,is evaluated against SAR/SWIM single and dual payload inversion methods across different wind speeds.This comparison highlights the model’s superior inversion accuracy over other methods.
基金Supported by Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (2019BT02H594)Sanya Technology Innovation Special Project (2022KJCX08)。
文摘Offshore carbon dioxide(CO_(2)) storage is an effective method for reducing greenhouse gas emissions. However, when using traditional seismic wave methods to monitor the migration of sequestration CO_(2) plumes, the characteristics of wave velocity changes tend to become insignificant beyond a certain limit. In contrast, the controllable source electromagnetic method(CSEM) remains highly sensitive to resistivity changes. By simulating different CO_(2) plume migration conditions, we established the relevant models and calculated the corresponding electric field response characteristic curves, allowing us to analyze the CSEM's ability to monitor CO_(2) plumes. We considered potential scenarios for the migration and diffusion of offshore CO_(2) storage, including various burial depths, vertical extension diffusion, lateral extension diffusion,multiple combinations of lateral intervals, and electric field components. We also obtained differences in resistivity inversion imaging obtained by CSEM to evaluate its feasibility in monitoring and to analyze all the electric field(Ex, Ey, and Ez) response characteristics. CSEM has great potential in monitoring CO_(2) plume migration in offshore saltwater reservoirs due to its high sensitivity and accuracy. Furthermore, changes in electromagnetic field response reflect the transport status of CO_(2) plumes, providing an important basis for monitoring and evaluating CO_(2)transport behavior during storage processes.
基金Supported by The Innovative Experimental Project of Provincial Higher Education Institutions by Sichuan Provincial Department of Education in 2023(90).
文摘Synthetic biology is a new frontier of life science,which aims to design,transform and even synthesize organisms with engineering design concept.Doing a good job in the teaching of"synthetic biology"is of great significance to the cultivation and reserve of biotechnology professionals in China,and also has an important impact on students' employment competitiveness.Under the background of"new engineering",the course reform of"synthetic biology"was carried out in terms of the construction of teaching staff,teaching methods,students' participation and the innovation of course content,and specific reform suggestions were put forward,hoping to effectively promote the sustainable development of"synthetic biology"and effectively improve the quality of education.