In many Eastern and Western countries,falling birth rates have led to the gradual aging of society.Older adults are often left alone at home or live in a long-term care center,which results in them being susceptible t...In many Eastern and Western countries,falling birth rates have led to the gradual aging of society.Older adults are often left alone at home or live in a long-term care center,which results in them being susceptible to unsafe events(such as falls)that can have disastrous consequences.However,automatically detecting falls fromvideo data is challenging,and automatic fall detection methods usually require large volumes of training data,which can be difficult to acquire.To address this problem,video kinematic data can be used as training data,thereby avoiding the requirement of creating a large fall data set.This study integrated an improved particle swarm optimization method into a double interactively recurrent fuzzy cerebellar model articulation controller model to develop a costeffective and accurate fall detection system.First,it obtained an optical flow(OF)trajectory diagram from image sequences by using the OF method,and it solved problems related to focal length and object offset by employing the discrete Fourier transform(DFT)algorithm.Second,this study developed the D-IRFCMAC model,which combines spatial and temporal(recurrent)information.Third,it designed an IPSO(Improved Particle Swarm Optimization)algorithm that effectively strengthens the exploratory capabilities of the proposed D-IRFCMAC(Double-Interactively Recurrent Fuzzy Cerebellar Model Articulation Controller)model in the global search space.The proposed approach outperforms existing state-of-the-art methods in terms of action recognition accuracy on the UR-Fall,UP-Fall,and PRECIS HAR data sets.The UCF11 dataset had an average accuracy of 93.13%,whereas the UCF101 dataset had an average accuracy of 92.19%.The UR-Fall dataset had an accuracy of 100%,the UP-Fall dataset had an accuracy of 99.25%,and the PRECIS HAR dataset had an accuracy of 99.07%.展开更多
The generation of nonclassical photons via quantum light–matter interactions is of fundamental importance in quantum optics.Here we investigate steady-state two-photon correlation function and photon squeezing in an ...The generation of nonclassical photons via quantum light–matter interactions is of fundamental importance in quantum optics.Here we investigate steady-state two-photon correlation function and photon squeezing in an open anisotropic Rabi lattice by applying quantum dressed master equation embedded with the mean-field approximation.The expanded antibunching effect of photons due to anisotropic qubit–photon interaction,is strongly suppressed by including inter-site photon tunneling,whereas the giant photon bunching keeps robust with weak inter-site photon tunneling strength.The microscopic processes for photon antibunching and bunching effects are presented based on incoherent transitions between eigenstates.The photon squeezing is also analyzed under the influences of qubit–photon coupling and anisotropic factor.The quadrature squeezing shows persistency by tuning on the inter-site photon tunneling,and becomes dramatically pronounced at the small anisotropic factor.Moreover,the increasing number of qubits significantly enhances quadrature squeezing with strong qubit–photon interaction.We hope such results may provide physical insights into efficient generation and manipulation of nonclassical features of photons in quantum light–matter interacting lattice systems.展开更多
The new Austrian tunneling method （NATM） is widely applied in design and construction of underground engineering projects. When the type and distribution of unfavorable geological bodies （UGBs） associated with the...The new Austrian tunneling method （NATM） is widely applied in design and construction of underground engineering projects. When the type and distribution of unfavorable geological bodies （UGBs） associated with their influences on geoengineering are complicated or unfortunately are overlooked, we should pay more attentions to internal features of rocks grades IV and V （even in local but mostly controlling zones）. With increasing attentions to the characteristics, mechanism and influences of engineering construction-triggered geohazards, it is crucial to fully understand the disturbance of these geohazards on project construction. A reasonable determination method in construction procedure, i.e. the shape of working face, the type of engineering support and the choice of feasible procedure, should be considered in order to mitigate the construction-triggered geohazards. Due to their high sensitivity to groundwater and in-situ stress, various UGBs exhibit hysteretic nature and failure modes. To give a complete understanding on the internal causes, the emphasis on advanced comprehensive geological forecasting and overall reinforcement treatment is therefore of more practical significance. Compre- hensive evaluation of influential factors, identification of UGB, and measures of discontinuity dynamic controlling comprises the geoengineering condition evaluation and dynamic controlling method. In a case of a cut slope, the variations of UGBs and the impacts of key environmental factors are presented, where more severe construction-triggered geohazards emerged in construction stage than those predicted in design and field investigation stages. As a result, the weight ratios of different influential factors with respect to field investigation, design and construction are obtained.展开更多
For robot interaction control,the interaction force between the robot and the manipulated object or environment should be monitored.Impedance control is a type of interaction control.Specifically,in impedance control,...For robot interaction control,the interaction force between the robot and the manipulated object or environment should be monitored.Impedance control is a type of interaction control.Specifically,in impedance control,the dynamic relationship between the interaction force and the resulting motion is controlled.In order to control the impedance of a mechanical system,typically,the interaction force has to be sensed.Due to the inherent limitations of direct force sensing at the interaction site,in the present work,the interaction force is observed using robust observers.In particular,to enhance the accuracy of impedance control,a first order sliding mode impedance controller is designed and incorporated in the present paper.Its advantage over positionbased interaction control algorithms is demonstrated through experimentation.Experimental results are given to show the effectiveness of the proposed algorithms.展开更多
In an offshore wind farm connected with a high-voltage direct current(HVDC)transmission system based on modular multilevel converter(MMC),a symmetric fault on the outgoing line at the sending end(SFOLSE)exhibits compl...In an offshore wind farm connected with a high-voltage direct current(HVDC)transmission system based on modular multilevel converter(MMC),a symmetric fault on the outgoing line at the sending end(SFOLSE)exhibits complex controlled characteristics in the fault current,which can undermine the reliability of relay protection.Detailed analysis of the control interaction between the wind farm and the MMC sending station(MMCSS)is conducted to ascertain the fault current characteristics.Considering the constraints imposed by the existence of a stable operating point(SOP)during SFOLSE,the phase angle difference distribution law for short-circuit currents sourced from both the wind farm and MMCSS is analyzed.Furthermore,the influence of control interaction on the reliability of distance protection is discussed.The results show that the additional impedance exhibits specific distribution characteristics under the influence of control interaction.In addition,the setting ratio of the dq-axis current reference for wind farm distance protection is analyzed,and the impact of wind farm control on the adaptability of distance protection under the constraints of the grid-connected guideline is evaluated.The main risk scenarios of misoperation are clarified,and the correctness of the analytical results is validated through PSCAD time-domain simulations.展开更多
The maximum power transfer capability(MPTC)of phase-locked loop(PLL)-based grid-following inverters is often limited under weak-grid conditions due to passivity violations caused by operating-point-dependent control l...The maximum power transfer capability(MPTC)of phase-locked loop(PLL)-based grid-following inverters is often limited under weak-grid conditions due to passivity violations caused by operating-point-dependent control loops.This paper reveals and compares the mechanisms of these violations across different control strategies.Using admittance decomposition and full-order state-space models for eigenvalue analysis,MPTC limitations from control loops and their interactions are identified.The small-signal stabilities of different control loops are compared under varying grid strength,and both static and dynamic MPTCs for each control mode are examined.This paper also explores how control loop interactions impact the MPTC,offering insights for tuning control loops to enhance stability in weak grids.For example,fast power control improves the MPTC when paired with a slow PLL,while power control has minimal effect when the PLL is sufficiently fast.The findings are validated through frequency scanning,eigenvalue analysis,simulations,and experiments.展开更多
Light-matter interactions are frequently perceived as predominantly influenced by the electric field,with the magnetic component of light often overlooked.Nonetheless,the magnetic field plays a pivotal role in various...Light-matter interactions are frequently perceived as predominantly influenced by the electric field,with the magnetic component of light often overlooked.Nonetheless,the magnetic field plays a pivotal role in various optical processes,including chiral light-matter interactions,photon-avalanching,and forbidden photochemistry,underscoring the significance of manipulating magnetic processes in optical phenomena.Here,we explore the ability to control the magnetic light and matter interactions at the nanoscale.In particular,we demonstrate experimentally,using a plasmonic nanostructure,the transfer of energy from the magnetic nearfield to a nanoparticle,thanks to the subwavelength magnetic confinement allowed by our nano-antenna.This control is made possible by the particular design of our plasmonic nanostructure,which has been optimized to spatially decouple the electric and magnetic components of localized plasmonic fields.Furthermore,by studying the spontaneous emission from the Lanthanide-ions doped nanoparticle,we observe that the measured field distributions are not spatially correlated with the experimentally estimated electric and magnetic local densities of states of this antenna,in contradiction with what would be expected from reciprocity.We demonstrate that this counter-intuitive observation is,in fact,the result of the different optical paths followed by the excitation and emission of the ions,which forbids a direct application of the reciprocity theorem.展开更多
This paper introduced the application of the WebGIS and virtual reality technology in the tourism industry and analyzed the existing problems in the tourism information system.Taking Daqing Oil Field Scenic Sport as a...This paper introduced the application of the WebGIS and virtual reality technology in the tourism industry and analyzed the existing problems in the tourism information system.Taking Daqing Oil Field Scenic Sport as an example,it introduced a method of constructing the virtual simulation platform for tourism based on the combination of WebGIS and virtual reality technology.Through the virtual simulation platform of Daqing Tourism Scenic Spot,it verified the design idea,methods,and technical feasibility of the virtual tourism system,and built a specific,feasible,and practical virtual simulation platform for tourism.It showed the bright prospects of virtual tourism development based on WebGIS and virtual reality technology.展开更多
Basing on the DFT calculations we propose the new theoretical model which describes both the surface tension σ of the short chain n-alkanes at their normal boiling points and their reaction rate constants with hydrox...Basing on the DFT calculations we propose the new theoretical model which describes both the surface tension σ of the short chain n-alkanes at their normal boiling points and their reaction rate constants with hydroxyl radicals OH<span style="white-space:nowrap;">• (at 297 ± 2 K) on the basis of their molecular orbital electronic characteristics. It has been shown that intermolecular dispersion attraction within the surface liquid monolayer of these compounds, as well as their reaction rate constants k with OH<span style="white-space:nowrap;">• radicals are determined by the energies E<sub>orb</sub> of the specific occupied molecular orbitals which are the same in the determination of both the above physico-chemical characteristics of the studied n-alkanes. The received regression equations confirm the theoretically found dependences between the quantities of σ and k and the module |E<sub>orb</sub>|. For the compounds under study this fact indicates the key role of their electronic structure particularities in determination of both the physical (surface tension) and the chemical (reaction rate constants) properties.展开更多
We derive analytical bright and dark solitons of the modified nonlinear Schroedinger equations with variable coefficients. Under constraint conditions between system parameters, the optical soliton transmission in the...We derive analytical bright and dark solitons of the modified nonlinear Schroedinger equations with variable coefficients. Under constraint conditions between system parameters, the optical soliton transmission in the dispersiondecreasing fibers can be exactly controlled by proper dispersion management. The analytical description of the interactions between the bright and dark solitons are first obtained.展开更多
In order to provide a simple and efficient approach to perform the real-time interactive motion control of virtual human in virtual maintenance environment(VME),the motion control method of virtual human based on limi...In order to provide a simple and efficient approach to perform the real-time interactive motion control of virtual human in virtual maintenance environment(VME),the motion control method of virtual human based on limited input information is proposed.With the space position tracking system with only one sensor the action sequences and motion models of virtual human,the human motions and hand actions in VME are driven by the sensor data in stages and in real time through the transmission condition control in the process of maintenance operation.And the input data and information is processed based on the method of Kalman filtering and wavelet transforming to improve the control effects.An experimental VME is also established to validate the control efficiency,and the experiment results show that the space motion control of virtual human in VME can be performed based on limited information with proposed control strategy.展开更多
There is always need for secure transmission of information and simultaneously compact-size photonic circuits. This can be achieved if surface plasmon-polaritons(SPPs) are used as source of information, and the reduce...There is always need for secure transmission of information and simultaneously compact-size photonic circuits. This can be achieved if surface plasmon-polaritons(SPPs) are used as source of information, and the reduced hacking as the transmission phenomenon. In this article, an SPP-based reduced hacking scheme is presented at interface between atomic medium and metallic conductor. The SPP propagation is manipulated with conductivity of the metal. The delay or advance of the SPP is found to create nanosecond time gap which can be used for storing and sending the information safely. The reduced hacking is further modified with conductivity of the metal and the control parameters of the atomic medium.展开更多
The feasibility of population transfer from a populated level via an intermediate state to the target level driven by few-cycle pulses is theoretically discussed. The processes of on- or far-resonance stimulated Raman...The feasibility of population transfer from a populated level via an intermediate state to the target level driven by few-cycle pulses is theoretically discussed. The processes of on- or far-resonance stimulated Raman scattering with sequential or simultaneous ultrashort pulses are investigated respectively. We find that the ultrashort pulses with about two optical cycles can be used to realize the population operation. This suggests that the population transfer can be completed in the femtosecond time scale. At the same time, our simulation shows that the signal of the carrier-envelope-phase-dependent effect can be enlarged due to quantum interference in some conditions. Our theoretic study may promote the research on the coherent control via ultrashort pulses in the related fields.展开更多
The new theoretical models describe both the solubility S of the shot chain n-alkanes in water at 298.15 K, and their reaction rate constants k with nitronium cation NO<sub>2</sub><sup>+ </sup>...The new theoretical models describe both the solubility S of the shot chain n-alkanes in water at 298.15 K, and their reaction rate constants k with nitronium cation NO<sub>2</sub><sup>+ </sup>at 293.15 K on the basis of their molecular orbital characteristics. It is shown that both the quantities S and k are determined by the energies E<sub>orb</sub> of the specific virtual (for S) and occupied (for k) molecular orbitals of these n-alkanes. The obtained regression equations confirm the theoretically found dependences of S and k on the absolute value of E<sub>orb</sub>. This fact demonstrates that the electronic structure particularities of the studied n-alkanes play a crucial role in both their above-mentioned physicochemical properties.展开更多
Conformable and breathable textile structures are ideal for flexible wearable pressure sensors,yet challenges remain in scalable fabrication,easy integration,and programmability.This study presents a cost-effective an...Conformable and breathable textile structures are ideal for flexible wearable pressure sensors,yet challenges remain in scalable fabrication,easy integration,and programmability.This study presents a cost-effective and customizable method to create fully textile-based pressure sensors using machine embroidery,enabling seamless integration into smart wearable systems.Two sensing configurations were developed:a single-layer satin block embroidered with conductive yarn,which exhibited high piezoresistivity,fast response(35 ms),quick recovery(16 ms),and robust durability over 5000 press-andrelease cycles,proven effective for monitoring activities such as plantar pressure and muscle contraction,and making it suitable for personalized health and fitness applications.The second configuration,a double-layer embroidery sensor with a conductive path and two parallel spacers anchored beneath a satin block,allows for array integration with minimal wiring,demonstrated by a 3×3 sensing array that,with the help of a convolutional neural network(CNN)machine learning model,accurately recognized handwritten numbers(0-9)with a 98.5%accuracy,showing its potential for user authentication and secure passcode entry.These findings underscore the potential of machine embroidery for developing scalable,integrated,and high-performance intelligent textile systems,paving the way for wearable technologies that are customizable,comfortable,and aesthetically appealing for a wide range of applications.展开更多
The controllers of wind parks that are connected to weak grids can induce unstable oscillations near the fundamental frequency.Such phenomenon can be studied with equivalent impedances of the wind generators,which dep...The controllers of wind parks that are connected to weak grids can induce unstable oscillations near the fundamental frequency.Such phenomenon can be studied with equivalent impedances of the wind generators,which depend on their operational setpoints at the fundamental frequency.The feasibility of such setpoint,i.e.,solution to the power flow,does not depend on the control parameters.However,oscillations from unfeasible setpoints and control instabilities both occur at weak grids and near the fundamental frequency.This letter presents an exploratory study to map the conditions where both phenomena occur,using sensitivity studies comprising multiple setpoints and control parameter tunings.The results are visually presented as the regions which inform the configurations leading to unfeasible setpoints,and unstable control interaction scenarios.Amongst the results,it can be observed that the trajectory of the eigenvalues in the Nyquist plots towards an unfeasible setpoint approaches a fundamental frequency instability.展开更多
The 12 May 2008 Mw 7.9 Wenchuan, China earthquake triggered about 200,000 landslides, which were controlled by a number of factors. This study examines five factors： slope angle, slope aspect, lithology, peak ground ...The 12 May 2008 Mw 7.9 Wenchuan, China earthquake triggered about 200,000 landslides, which were controlled by a number of factors. This study examines five factors： slope angle, slope aspect, lithology, peak ground acceleration （PGA）, and fault side （relative position on the seismogenic fault, i.e., hanging wall or footwall）, to determine how these factors control the co-seismic land- slide occurrence and whether one or more factors, acting alone or in concert, are involved in promoting or suppressing landslides. We performed a multi-factor statistical analysis using data from the 2008 Wenchuan earthquake. The results show that in the areas characterized by steep topography or where strong ground shaking occurred during the earthquake, there is a closer relation- ship between slope aspect and landslide number density （LND） than other areas. The relationship between lithology and LND values depends on PGA. In turn, the relationship between LND values and PGA is also influenced by lithology. In addition, the controlling effect of lithology on co-seismic landslides on the hanging wall of the seismogenic fault is greater than that on the footwall. Examining interactions among these factors can improve understanding of the mechanisms of co-seismic landslide occurrence.展开更多
Compliant interaction control is a key technology for robots performing contact-rich manipulation tasks.The design of the compliant controller needs to consider the robot hardware because complex control algorithms ma...Compliant interaction control is a key technology for robots performing contact-rich manipulation tasks.The design of the compliant controller needs to consider the robot hardware because complex control algorithms may not be compatible with the hardware performance,especially for some industrial robots with low bandwidth sensors.This paper focuses on effective and easy-to-use compliant control algorithms for position/velocity-controlled robots.Inspired by human arm stiffness adaptation behavior,a novel variable target stiffness(NVTS)admittance control strategy is proposed for adaptive force tracking,in which a proportional integral derivative(PID)variable stiffness law is designed to update the stiffness coefficient of the admittance function by the force and position feedback.Meanwhile,its stability and force-tracking capability are theoretically proven.In addition,an impact compensator(Impc)is integrated into the NVTS controller to enhance its disturbance-suppression capability when the robot is subjected to strong vibration disturbances in complicated surface polishing tasks.The proposed controllers are validated through four groups of experimental tests using different robots and the corresponding results demonstrate that they have high-accuracy tracking capability and strong adaptability in unknown environments.展开更多
Two examples of the use of vortex control to reduce noise and enhance the stable operating range of a centrifugal compressor are presented in this paper.In the case of high-flow operation of a centrifugal compressor w...Two examples of the use of vortex control to reduce noise and enhance the stable operating range of a centrifugal compressor are presented in this paper.In the case of high-flow operation of a centrifugal compressor with a vaned diffuser,a discrete frequency noise induced by interaction between the impeller-discharge flow and the diffuser vane,which appears most notably in the power spectra of the radiated noise,can be reduced using a tapered diffuser vane(TDV) without affecting the performance of the compressor.Twin longitudinal vortices produced by leakage flow passing through the tapered portion of the diffuser vane induce secondary flow in the direction of the blade surface and prevent flow separation from the leading edge of the diffuser.The use of a TDV can effectively reduce both the discrete frequency noise generated by the interaction between the impeller-discharge flow and the diffuser surface and the broadband turbulent noise component.In the case of low-flow operation,a leading-edge vortex(LEV) that forms on the shroud side of the suction surface near the leading edge of the diffuser increases significantly in size and blocks flow in the diffuser passage.The formation of an LEV may adversely affect the performance of the compressor and may cause the diffuser to stall.Using a one-side tapered diffuser vane to suppress the evolution of an LEV,the stable operating range of the compressor can be increased by more than 12 percent,and the pressure-rise characteristics of the compressor can be improved.The results of a supplementary examination of the structure and unsteady behavior of LEVs,conducted by means of detailed numerical simulations,are also presented.展开更多
In recent years,subsynchronous control interaction(SSCI)has frequently taken place in renewable-connected power systems.To counter this issue,utilities have been seeking tools for fast and accurate identification of S...In recent years,subsynchronous control interaction(SSCI)has frequently taken place in renewable-connected power systems.To counter this issue,utilities have been seeking tools for fast and accurate identification of SSCI events.The main challenges of SSCI monitoring are the time-varying nature and uncertain modes of SSCI events.Accordingly,this paper presents a simple but effective method that takes advantage of intrinsic time-scale decomposition(ITD).The main purpose is to improve the accuracy and robustness of ITD by incorporating the least-squares method.Results show that the proposed method strikes a good balance between dynamic performance and estimation accuracy.More importantly,the method does not require any prior information,and its performance is therefore not affected by the frequency constitution of the SSCI.Comprehensive comparative studies are conducted to demonstrate the usefulness of the method through synthetic signals,electromagnetic temporary program(EMTP)simulations,and field-recorded SSCI data.Finally,real-time simulation tests are conducted to show the feasibility of the method for real-time monitoring.展开更多
基金supported by the National Science and Technology Council under grants NSTC 112-2221-E-320-002the Buddhist Tzu Chi Medical Foundation in Taiwan under Grant TCMMP 112-02-02.
文摘In many Eastern and Western countries,falling birth rates have led to the gradual aging of society.Older adults are often left alone at home or live in a long-term care center,which results in them being susceptible to unsafe events(such as falls)that can have disastrous consequences.However,automatically detecting falls fromvideo data is challenging,and automatic fall detection methods usually require large volumes of training data,which can be difficult to acquire.To address this problem,video kinematic data can be used as training data,thereby avoiding the requirement of creating a large fall data set.This study integrated an improved particle swarm optimization method into a double interactively recurrent fuzzy cerebellar model articulation controller model to develop a costeffective and accurate fall detection system.First,it obtained an optical flow(OF)trajectory diagram from image sequences by using the OF method,and it solved problems related to focal length and object offset by employing the discrete Fourier transform(DFT)algorithm.Second,this study developed the D-IRFCMAC model,which combines spatial and temporal(recurrent)information.Third,it designed an IPSO(Improved Particle Swarm Optimization)algorithm that effectively strengthens the exploratory capabilities of the proposed D-IRFCMAC(Double-Interactively Recurrent Fuzzy Cerebellar Model Articulation Controller)model in the global search space.The proposed approach outperforms existing state-of-the-art methods in terms of action recognition accuracy on the UR-Fall,UP-Fall,and PRECIS HAR data sets.The UCF11 dataset had an average accuracy of 93.13%,whereas the UCF101 dataset had an average accuracy of 92.19%.The UR-Fall dataset had an accuracy of 100%,the UP-Fall dataset had an accuracy of 99.25%,and the PRECIS HAR dataset had an accuracy of 99.07%.
基金Project supported by the National Natural Science Foundation of China(Grant No.11874011)the Opening Project of Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology.
文摘The generation of nonclassical photons via quantum light–matter interactions is of fundamental importance in quantum optics.Here we investigate steady-state two-photon correlation function and photon squeezing in an open anisotropic Rabi lattice by applying quantum dressed master equation embedded with the mean-field approximation.The expanded antibunching effect of photons due to anisotropic qubit–photon interaction,is strongly suppressed by including inter-site photon tunneling,whereas the giant photon bunching keeps robust with weak inter-site photon tunneling strength.The microscopic processes for photon antibunching and bunching effects are presented based on incoherent transitions between eigenstates.The photon squeezing is also analyzed under the influences of qubit–photon coupling and anisotropic factor.The quadrature squeezing shows persistency by tuning on the inter-site photon tunneling,and becomes dramatically pronounced at the small anisotropic factor.Moreover,the increasing number of qubits significantly enhances quadrature squeezing with strong qubit–photon interaction.We hope such results may provide physical insights into efficient generation and manipulation of nonclassical features of photons in quantum light–matter interacting lattice systems.
基金support by the National Natural Science Foundation of China (No. 41372324)support from the Chinese Special Funds for Major State Basic Research Project under Grant No. 2010CB732001
文摘The new Austrian tunneling method （NATM） is widely applied in design and construction of underground engineering projects. When the type and distribution of unfavorable geological bodies （UGBs） associated with their influences on geoengineering are complicated or unfortunately are overlooked, we should pay more attentions to internal features of rocks grades IV and V （even in local but mostly controlling zones）. With increasing attentions to the characteristics, mechanism and influences of engineering construction-triggered geohazards, it is crucial to fully understand the disturbance of these geohazards on project construction. A reasonable determination method in construction procedure, i.e. the shape of working face, the type of engineering support and the choice of feasible procedure, should be considered in order to mitigate the construction-triggered geohazards. Due to their high sensitivity to groundwater and in-situ stress, various UGBs exhibit hysteretic nature and failure modes. To give a complete understanding on the internal causes, the emphasis on advanced comprehensive geological forecasting and overall reinforcement treatment is therefore of more practical significance. Compre- hensive evaluation of influential factors, identification of UGB, and measures of discontinuity dynamic controlling comprises the geoengineering condition evaluation and dynamic controlling method. In a case of a cut slope, the variations of UGBs and the impacts of key environmental factors are presented, where more severe construction-triggered geohazards emerged in construction stage than those predicted in design and field investigation stages. As a result, the weight ratios of different influential factors with respect to field investigation, design and construction are obtained.
文摘For robot interaction control,the interaction force between the robot and the manipulated object or environment should be monitored.Impedance control is a type of interaction control.Specifically,in impedance control,the dynamic relationship between the interaction force and the resulting motion is controlled.In order to control the impedance of a mechanical system,typically,the interaction force has to be sensed.Due to the inherent limitations of direct force sensing at the interaction site,in the present work,the interaction force is observed using robust observers.In particular,to enhance the accuracy of impedance control,a first order sliding mode impedance controller is designed and incorporated in the present paper.Its advantage over positionbased interaction control algorithms is demonstrated through experimentation.Experimental results are given to show the effectiveness of the proposed algorithms.
基金supported by the National Natural Science Foundation of China(No.51977019).
文摘In an offshore wind farm connected with a high-voltage direct current(HVDC)transmission system based on modular multilevel converter(MMC),a symmetric fault on the outgoing line at the sending end(SFOLSE)exhibits complex controlled characteristics in the fault current,which can undermine the reliability of relay protection.Detailed analysis of the control interaction between the wind farm and the MMC sending station(MMCSS)is conducted to ascertain the fault current characteristics.Considering the constraints imposed by the existence of a stable operating point(SOP)during SFOLSE,the phase angle difference distribution law for short-circuit currents sourced from both the wind farm and MMCSS is analyzed.Furthermore,the influence of control interaction on the reliability of distance protection is discussed.The results show that the additional impedance exhibits specific distribution characteristics under the influence of control interaction.In addition,the setting ratio of the dq-axis current reference for wind farm distance protection is analyzed,and the impact of wind farm control on the adaptability of distance protection under the constraints of the grid-connected guideline is evaluated.The main risk scenarios of misoperation are clarified,and the correctness of the analytical results is validated through PSCAD time-domain simulations.
基金funded by the Australian Renewable Energy Agency(No.2023/ARP010).
文摘The maximum power transfer capability(MPTC)of phase-locked loop(PLL)-based grid-following inverters is often limited under weak-grid conditions due to passivity violations caused by operating-point-dependent control loops.This paper reveals and compares the mechanisms of these violations across different control strategies.Using admittance decomposition and full-order state-space models for eigenvalue analysis,MPTC limitations from control loops and their interactions are identified.The small-signal stabilities of different control loops are compared under varying grid strength,and both static and dynamic MPTCs for each control mode are examined.This paper also explores how control loop interactions impact the MPTC,offering insights for tuning control loops to enhance stability in weak grids.For example,fast power control improves the MPTC when paired with a slow PLL,while power control has minimal effect when the PLL is sufficiently fast.The findings are validated through frequency scanning,eigenvalue analysis,simulations,and experiments.
基金supported by the ERC grant FemtoMagnet(grant no.101087709)the financial support from the Agence Nationale de la Recherche(ANR-20-CE09-0031-01,ANR-22-CE09-0027-04 and ANR-23-ERCC-0005)the Institut de Physique du CNRS(Tremplin@INP 2020).
文摘Light-matter interactions are frequently perceived as predominantly influenced by the electric field,with the magnetic component of light often overlooked.Nonetheless,the magnetic field plays a pivotal role in various optical processes,including chiral light-matter interactions,photon-avalanching,and forbidden photochemistry,underscoring the significance of manipulating magnetic processes in optical phenomena.Here,we explore the ability to control the magnetic light and matter interactions at the nanoscale.In particular,we demonstrate experimentally,using a plasmonic nanostructure,the transfer of energy from the magnetic nearfield to a nanoparticle,thanks to the subwavelength magnetic confinement allowed by our nano-antenna.This control is made possible by the particular design of our plasmonic nanostructure,which has been optimized to spatially decouple the electric and magnetic components of localized plasmonic fields.Furthermore,by studying the spontaneous emission from the Lanthanide-ions doped nanoparticle,we observe that the measured field distributions are not spatially correlated with the experimentally estimated electric and magnetic local densities of states of this antenna,in contradiction with what would be expected from reciprocity.We demonstrate that this counter-intuitive observation is,in fact,the result of the different optical paths followed by the excitation and emission of the ions,which forbids a direct application of the reciprocity theorem.
基金Supported by Student's Platform for Innovation and Entrepreneurship Training Program "Development of Campus Precise Navigation System Based on Mobile Terminal"(201610223065)Heilongjiang Provincial Level and Postgraduate Education Reform Research Project "Research on the Integration of Production,Study and Practice Training Mode of Agricultural Information Professional Master"(JGXM_HLJ_2014094)Heilongjiang Provincial Level and Postgraduate Education Teaching Reform Project "Training Model of Practical and Innovative Agricultural Information Professional Master"(JGXM_HLJ_2016126)
文摘This paper introduced the application of the WebGIS and virtual reality technology in the tourism industry and analyzed the existing problems in the tourism information system.Taking Daqing Oil Field Scenic Sport as an example,it introduced a method of constructing the virtual simulation platform for tourism based on the combination of WebGIS and virtual reality technology.Through the virtual simulation platform of Daqing Tourism Scenic Spot,it verified the design idea,methods,and technical feasibility of the virtual tourism system,and built a specific,feasible,and practical virtual simulation platform for tourism.It showed the bright prospects of virtual tourism development based on WebGIS and virtual reality technology.
文摘Basing on the DFT calculations we propose the new theoretical model which describes both the surface tension σ of the short chain n-alkanes at their normal boiling points and their reaction rate constants with hydroxyl radicals OH<span style="white-space:nowrap;">• (at 297 ± 2 K) on the basis of their molecular orbital electronic characteristics. It has been shown that intermolecular dispersion attraction within the surface liquid monolayer of these compounds, as well as their reaction rate constants k with OH<span style="white-space:nowrap;">• radicals are determined by the energies E<sub>orb</sub> of the specific occupied molecular orbitals which are the same in the determination of both the above physico-chemical characteristics of the studied n-alkanes. The received regression equations confirm the theoretically found dependences between the quantities of σ and k and the module |E<sub>orb</sub>|. For the compounds under study this fact indicates the key role of their electronic structure particularities in determination of both the physical (surface tension) and the chemical (reaction rate constants) properties.
基金Project supported by the National Natural Science Foundations of China (Grant No. 11005092)the Program for Innovative Research Team of Young Teachers (Grant No. 2009RC01)the Scientific Research and Developed Fund of Zhejiang Agricultural and Forestry University (Grant No. 2009FK42).
文摘We derive analytical bright and dark solitons of the modified nonlinear Schroedinger equations with variable coefficients. Under constraint conditions between system parameters, the optical soliton transmission in the dispersiondecreasing fibers can be exactly controlled by proper dispersion management. The analytical description of the interactions between the bright and dark solitons are first obtained.
文摘In order to provide a simple and efficient approach to perform the real-time interactive motion control of virtual human in virtual maintenance environment(VME),the motion control method of virtual human based on limited input information is proposed.With the space position tracking system with only one sensor the action sequences and motion models of virtual human,the human motions and hand actions in VME are driven by the sensor data in stages and in real time through the transmission condition control in the process of maintenance operation.And the input data and information is processed based on the method of Kalman filtering and wavelet transforming to improve the control effects.An experimental VME is also established to validate the control efficiency,and the experiment results show that the space motion control of virtual human in VME can be performed based on limited information with proposed control strategy.
文摘There is always need for secure transmission of information and simultaneously compact-size photonic circuits. This can be achieved if surface plasmon-polaritons(SPPs) are used as source of information, and the reduced hacking as the transmission phenomenon. In this article, an SPP-based reduced hacking scheme is presented at interface between atomic medium and metallic conductor. The SPP propagation is manipulated with conductivity of the metal. The delay or advance of the SPP is found to create nanosecond time gap which can be used for storing and sending the information safely. The reduced hacking is further modified with conductivity of the metal and the control parameters of the atomic medium.
基金Project supported by the National Natural Science Foundation of China(Grant No.61008016)the Natural Science Foundation in Shaanxi Province,China(Grant No.2010JQ1002)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20106101120020)
文摘The feasibility of population transfer from a populated level via an intermediate state to the target level driven by few-cycle pulses is theoretically discussed. The processes of on- or far-resonance stimulated Raman scattering with sequential or simultaneous ultrashort pulses are investigated respectively. We find that the ultrashort pulses with about two optical cycles can be used to realize the population operation. This suggests that the population transfer can be completed in the femtosecond time scale. At the same time, our simulation shows that the signal of the carrier-envelope-phase-dependent effect can be enlarged due to quantum interference in some conditions. Our theoretic study may promote the research on the coherent control via ultrashort pulses in the related fields.
文摘The new theoretical models describe both the solubility S of the shot chain n-alkanes in water at 298.15 K, and their reaction rate constants k with nitronium cation NO<sub>2</sub><sup>+ </sup>at 293.15 K on the basis of their molecular orbital characteristics. It is shown that both the quantities S and k are determined by the energies E<sub>orb</sub> of the specific virtual (for S) and occupied (for k) molecular orbitals of these n-alkanes. The obtained regression equations confirm the theoretically found dependences of S and k on the absolute value of E<sub>orb</sub>. This fact demonstrates that the electronic structure particularities of the studied n-alkanes play a crucial role in both their above-mentioned physicochemical properties.
文摘Conformable and breathable textile structures are ideal for flexible wearable pressure sensors,yet challenges remain in scalable fabrication,easy integration,and programmability.This study presents a cost-effective and customizable method to create fully textile-based pressure sensors using machine embroidery,enabling seamless integration into smart wearable systems.Two sensing configurations were developed:a single-layer satin block embroidered with conductive yarn,which exhibited high piezoresistivity,fast response(35 ms),quick recovery(16 ms),and robust durability over 5000 press-andrelease cycles,proven effective for monitoring activities such as plantar pressure and muscle contraction,and making it suitable for personalized health and fitness applications.The second configuration,a double-layer embroidery sensor with a conductive path and two parallel spacers anchored beneath a satin block,allows for array integration with minimal wiring,demonstrated by a 3×3 sensing array that,with the help of a convolutional neural network(CNN)machine learning model,accurately recognized handwritten numbers(0-9)with a 98.5%accuracy,showing its potential for user authentication and secure passcode entry.These findings underscore the potential of machine embroidery for developing scalable,integrated,and high-performance intelligent textile systems,paving the way for wearable technologies that are customizable,comfortable,and aesthetically appealing for a wide range of applications.
基金supported by the Office of International Affairs and External Cooperation of the University of Costa Rica(OAICE-UCR)(No.OAICE-CAB-165-2016).
文摘The controllers of wind parks that are connected to weak grids can induce unstable oscillations near the fundamental frequency.Such phenomenon can be studied with equivalent impedances of the wind generators,which depend on their operational setpoints at the fundamental frequency.The feasibility of such setpoint,i.e.,solution to the power flow,does not depend on the control parameters.However,oscillations from unfeasible setpoints and control instabilities both occur at weak grids and near the fundamental frequency.This letter presents an exploratory study to map the conditions where both phenomena occur,using sensitivity studies comprising multiple setpoints and control parameter tunings.The results are visually presented as the regions which inform the configurations leading to unfeasible setpoints,and unstable control interaction scenarios.Amongst the results,it can be observed that the trajectory of the eigenvalues in the Nyquist plots towards an unfeasible setpoint approaches a fundamental frequency instability.
基金This research was supported by the National Natural Science Foundation of China （Grant Nos. 41472202 and 41202235） and the National Basic Research Program of China （No. 2012BAK10B03）. Comments from three anonymous reviewers significantly improved this manuscript.
文摘The 12 May 2008 Mw 7.9 Wenchuan, China earthquake triggered about 200,000 landslides, which were controlled by a number of factors. This study examines five factors： slope angle, slope aspect, lithology, peak ground acceleration （PGA）, and fault side （relative position on the seismogenic fault, i.e., hanging wall or footwall）, to determine how these factors control the co-seismic land- slide occurrence and whether one or more factors, acting alone or in concert, are involved in promoting or suppressing landslides. We performed a multi-factor statistical analysis using data from the 2008 Wenchuan earthquake. The results show that in the areas characterized by steep topography or where strong ground shaking occurred during the earthquake, there is a closer relation- ship between slope aspect and landslide number density （LND） than other areas. The relationship between lithology and LND values depends on PGA. In turn, the relationship between LND values and PGA is also influenced by lithology. In addition, the controlling effect of lithology on co-seismic landslides on the hanging wall of the seismogenic fault is greater than that on the footwall. Examining interactions among these factors can improve understanding of the mechanisms of co-seismic landslide occurrence.
基金the National Natural Science Foundation of China(Grant Nos.62103407,52075530,and 52175272)the State Key Laboratory of Robotics Foundation(Grant No.Y91Z0303)。
文摘Compliant interaction control is a key technology for robots performing contact-rich manipulation tasks.The design of the compliant controller needs to consider the robot hardware because complex control algorithms may not be compatible with the hardware performance,especially for some industrial robots with low bandwidth sensors.This paper focuses on effective and easy-to-use compliant control algorithms for position/velocity-controlled robots.Inspired by human arm stiffness adaptation behavior,a novel variable target stiffness(NVTS)admittance control strategy is proposed for adaptive force tracking,in which a proportional integral derivative(PID)variable stiffness law is designed to update the stiffness coefficient of the admittance function by the force and position feedback.Meanwhile,its stability and force-tracking capability are theoretically proven.In addition,an impact compensator(Impc)is integrated into the NVTS controller to enhance its disturbance-suppression capability when the robot is subjected to strong vibration disturbances in complicated surface polishing tasks.The proposed controllers are validated through four groups of experimental tests using different robots and the corresponding results demonstrate that they have high-accuracy tracking capability and strong adaptability in unknown environments.
文摘Two examples of the use of vortex control to reduce noise and enhance the stable operating range of a centrifugal compressor are presented in this paper.In the case of high-flow operation of a centrifugal compressor with a vaned diffuser,a discrete frequency noise induced by interaction between the impeller-discharge flow and the diffuser vane,which appears most notably in the power spectra of the radiated noise,can be reduced using a tapered diffuser vane(TDV) without affecting the performance of the compressor.Twin longitudinal vortices produced by leakage flow passing through the tapered portion of the diffuser vane induce secondary flow in the direction of the blade surface and prevent flow separation from the leading edge of the diffuser.The use of a TDV can effectively reduce both the discrete frequency noise generated by the interaction between the impeller-discharge flow and the diffuser surface and the broadband turbulent noise component.In the case of low-flow operation,a leading-edge vortex(LEV) that forms on the shroud side of the suction surface near the leading edge of the diffuser increases significantly in size and blocks flow in the diffuser passage.The formation of an LEV may adversely affect the performance of the compressor and may cause the diffuser to stall.Using a one-side tapered diffuser vane to suppress the evolution of an LEV,the stable operating range of the compressor can be increased by more than 12 percent,and the pressure-rise characteristics of the compressor can be improved.The results of a supplementary examination of the structure and unsteady behavior of LEVs,conducted by means of detailed numerical simulations,are also presented.
基金supported in part by the National Natural Science Foundation of China(No.51907133)in part by the Fundamental Research Funds for the Central Universities(No.YJ201911).
文摘In recent years,subsynchronous control interaction(SSCI)has frequently taken place in renewable-connected power systems.To counter this issue,utilities have been seeking tools for fast and accurate identification of SSCI events.The main challenges of SSCI monitoring are the time-varying nature and uncertain modes of SSCI events.Accordingly,this paper presents a simple but effective method that takes advantage of intrinsic time-scale decomposition(ITD).The main purpose is to improve the accuracy and robustness of ITD by incorporating the least-squares method.Results show that the proposed method strikes a good balance between dynamic performance and estimation accuracy.More importantly,the method does not require any prior information,and its performance is therefore not affected by the frequency constitution of the SSCI.Comprehensive comparative studies are conducted to demonstrate the usefulness of the method through synthetic signals,electromagnetic temporary program(EMTP)simulations,and field-recorded SSCI data.Finally,real-time simulation tests are conducted to show the feasibility of the method for real-time monitoring.
