This study presents an emergency control method for sub-synchronous oscillations in wind power gridconnected systems based on transfer learning,addressing the issue of insufficient generalization ability of traditiona...This study presents an emergency control method for sub-synchronous oscillations in wind power gridconnected systems based on transfer learning,addressing the issue of insufficient generalization ability of traditional methods in complex real-world scenarios.By combining deep reinforcement learning with a transfer learning framework,cross-scenario knowledge transfer is achieved,significantly enhancing the adaptability of the control strategy.First,a sub-synchronous oscillation emergency control model for the wind power grid integration system is constructed under fixed scenarios based on deep reinforcement learning.A reward evaluation system based on the active power oscillation pattern of the system is proposed,introducing penalty functions for the number of machine-shedding rounds and the number of machines shed.This avoids the economic losses and grid security risks caused by the excessive one-time shedding of wind turbines.Furthermore,transfer learning is introduced into model training to enhance the model’s generalization capability in dealing with complex scenarios of actual wind power grid integration systems.By introducing the Maximum Mean Discrepancy(MMD)algorithm to calculate the distribution differences between source data and target data,the online decision-making reliability of the emergency control model is improved.Finally,the effectiveness of the proposed emergency control method for multi-scenario sub-synchronous oscillation in wind power grid integration systems based on transfer learning is analyzed using the New England 39-bus system.展开更多
Steady speed control of agricultural machinery can improve operating quality and efficiency.To address the impact of farmland slope variations on the speed stability of unmanned operation agricultural machinery,a hybr...Steady speed control of agricultural machinery can improve operating quality and efficiency.To address the impact of farmland slope variations on the speed stability of unmanned operation agricultural machinery,a hybrid control method was proposed.This method included a hybrid controller composed of a slope-based controller and a proportional-integral-derivative(PID)controller.The speed of agricultural machinery was influenced by longitudinal forces,which were divided into two parts:one part was slope-related forces and conventional resistance,and the other was hard-to-estimate forces,such as sliding friction.For the first part,a slope-based controller was designed;for the second part,a PID controller was implemented.By combining these two controllers,the system can dynamically adjust the throttle opening and the brake master cylinder pressure,ensuring steady speed travel on sloping farmland.Simulation tests at a target speed of 7 km/h demonstrated that the proposed controller maintained a stable speed,achieving a root mean square error of 0.13 km/h and a mean absolute percentage error of 1.6%.Field tests on a practical experimental platform validated the method’s effectiveness,with results showing consistent control performance across varying slope conditions.The proposed controller demonstrated superior control performance.Experimental data verified that this method can achieve precise control of the agricultural machinery’s movement speed,meeting the stability requirements for agricultural operations.展开更多
Inertial response control(IRC)makes variable-speed wind turbine generators(WTGs)provide short-term frequency support during contingencies by releasing the kinetic energy stored in wind turbine rotors.When frequency su...Inertial response control(IRC)makes variable-speed wind turbine generators(WTGs)provide short-term frequency support during contingencies by releasing the kinetic energy stored in wind turbine rotors.When frequency support is terminated,the rotor speed should be restored to optimum for maximum power point tracking(MPPT).Existing IRCs utilize rotor speed recovery(RSR)strategies with a consistent power reference function.However,under real turbulent wind with alternate gusts and lulls,the consistent power reference function may fail to restore rotor speed or cause unexpected secondary frequency drop(SFD).In this regard,this paper proposes a novel adaptive RSR strategy that not only restores rotor speed via the aerodynamic power enhanced by wind gusts,but also stabilizes the turbine at wind lulls by tracking a suboptimal power curve.Experiments on a wind power-integrated power system testbed validate the proposed RSR strategy can successfully restore rotor speed while attenuating SFD under turbulent wind.展开更多
Thousand-seed weight(TSW)is a critical target for genetic improvement in rapeseed(Brassica napus L.).However,phenotypic selection for this trait remains challenging due to its polygenic regulation by multiple quantita...Thousand-seed weight(TSW)is a critical target for genetic improvement in rapeseed(Brassica napus L.).However,phenotypic selection for this trait remains challenging due to its polygenic regulation by multiple quantitative trait loci(QTL).Here,six favorable TSW QTL alleles from two donor parents were introgress into an elite restorer line,621R,using an integrated strategy combining marker-assisted backcrossing and speed breeding protocols.Through six rounds of backcrossing and convergent crossing followed by two generations of selfing strategies,we developed 13 advanced lines with diverse TSW QTL combinations within 24 months.Field evaluations across three environments revealed that all lines exhibited significantly increased TSW in spring conditions(Minle,Gansu)and winter environments(Wuhan and Jiangling,Hubei)except for two lines which only showed increase in the spring environment.Hybridization assays using these lines as male parents crossed with two male-sterile lines(RG430A and 616A)demonstrated transgressive segregation for TSW:For RG430A-derived hybrids,all crosses significantly outperformed the original control(RG430A×621R)in Wuhan,with 8/13 and 9/13 crosses showing significant TSW increases in Minle and Jiangling,respectively.For 616A-derived hybrids,11/13 and 10/13 crosses exhibited significant TSW enhancement in Minle and Jiangling,compared to 3/13 in Wuhan.Notably,two top-performing hybrids achieved 13.0%and 6.8%higher plot yields,respectively.Our results demonstrate that strategic pyramiding of complementary TSW QTL alleles effectively enhances seed weight in rapeseed,and these improved lines represent valuable genetic resources for developing high-yield hybrids.展开更多
In this study,tropical cyclone(TC)translation speed was introduced as a new similarity factor within the generalized initial value(GIV)framework,enhancing the disaster preassessment capability of the dynamical statist...In this study,tropical cyclone(TC)translation speed was introduced as a new similarity factor within the generalized initial value(GIV)framework,enhancing the disaster preassessment capability of the dynamical statistical analog ensemble forecast model for landfalling TC disasters(DSAEF_LTD model).Three TC translation speed indicators most relevant to TC precipitation were incorporated:the maximum speed on Day 1(the first day of TC-induced precipitation and wind occurring on land)and the average and minimum speeds over All Days(all days of TC-induced precipitation and wind occurring on land),all classified using the Kmeans clustering algorithm.Simulation experiments showed that integrating TC translation speed enhanced the model's performance.The model provided a better optimal common scheme,with the TSS UM(sum of threat scores for severe and above and extremely severe and above disasters)increasing by 2.66%(from 0.5117 to 0.5253)compared with the original model.More importantly,its preassessment ability improved significantly,with the average TSS UM for independent samples increasing by 6.43%(from 0.6488 to0.6905).The modified model demonstrated greater accuracy in capturing disaster severity and distribution of TCs with significant speed characteristics or with regular tracks.This improvement stemmed from reduced false alarms due to the selection of analogs that are more similar to the target TC.The enhanced preassessment ability can be attributed to the key role of TC translation speed,which significantly influences TC precipitation patterns and improves TC precipitation forecasting.Since precipitation is one of the most crucial disaster-causing factors,better TC precipitation forecasting leads to improved disaster preassessment outcomes.These findings emphasize the promising potential of the DSAEF_LTD model for future TC disaster research and management,contributing to the achievement of the Sustainable Development Goals set by the United Nations 2030 Agenda by strengthening coastal resilience.展开更多
A high-speed single-mode vertical-cavity surface-emitting laser(VCSEL)is one of the most important light sources for optical interconnects in data centers.Single-mode VCSEL can improve the transmission distance.In thi...A high-speed single-mode vertical-cavity surface-emitting laser(VCSEL)is one of the most important light sources for optical interconnects in data centers.Single-mode VCSEL can improve the transmission distance.In this letter,we demonstrate a single-mode 850 nm VCSEL with a bit rate of 60 Gb/s under NRZ modulation and 104 Gb/s under PAM4 modulation across a 100 m length of OM5 fiber,without the need for equalization or a filter.In addition,by using optical injection locking,the 3 dB bandwidth is enhanced to 68.5 GHz.展开更多
This paper addresses the three-dimensional(3-D)approach angle constrained cooperative guidance problem for speed-varying missiles against maneuvering targets.First,the guidance problem is formulated in a relative refe...This paper addresses the three-dimensional(3-D)approach angle constrained cooperative guidance problem for speed-varying missiles against maneuvering targets.First,the guidance problem is formulated in a relative reference frame and a virtual control input is selected.Then,the cooperative guidance law is designed on the basis of a prediction-correction framework.The time-to-go under the baseline command is estimated by an efficient prediction method with a realistic aerodynamic model and a biased command is developed by utilizing the time-to-go predictions for synchronizing different missiles'impact times.The design of the biased command is decoupled into the individual design of its direction and magnitude.It is proved that the designed cooperative guidance law can make the time-to-go consensus error converge to zero before interception.Finally,the designed guidance law is validated through a series of numerical simulations.展开更多
This study aims to explore the impact of combined health education and dietary guidance on the speed of postoperative recovery in patients with gastrointestinal polyps.A specific number of patients who underwent gastr...This study aims to explore the impact of combined health education and dietary guidance on the speed of postoperative recovery in patients with gastrointestinal polyps.A specific number of patients who underwent gastrointestinal polyp resection were selected and randomly divided into a control group and an experimental group.The control group received routine nursing,while the experimental group implemented combined health education and dietary guidance on this basis.By comparing the recovery indicators of the two groups,it was found that the recovery speed of the experimental group was significantly faster than that of the control group,indicating that this combined intervention method can effectively promote patient recovery.展开更多
During the hoisting process of the offshore substation,changes in the hoisting speed can affect the hoisting system.Therefore,this study set four different speed conditions for the lifting and lowering stages of the i...During the hoisting process of the offshore substation,changes in the hoisting speed can affect the hoisting system.Therefore,this study set four different speed conditions for the lifting and lowering stages of the installation process,and studied the impact of different lifting and lowering speeds on the hoisting system under the same environmental conditions through numerical simulation.The results show that during the lifting operation,as the lifting speed increases,the swing motion of the substation and the installation vessel tends to decrease,and the faster the hoisting speed,the more obvious the swing suppression of the substation and the installation vessel,and the smaller the fluctuation in the tension amplitude of the slings and mooring lines.In contrast,during the lowering operation,as the lowering speed increases,the swing motion of the substation and the installation vessel tends to increase,and the faster the lowering speed,the more obvious the swing amplification effect of the substation and the installation vessel.Therefore,during hoisting operations,increasing the lifting speed and reducing the lowering speed can mitigate the motion performance of the hoisting coupling system,reduce the tension amplitude variation of the sling and mooring,and ensure the smooth progress of the hoisting operation.展开更多
Wind speed is a crucial parameter affecting wind energy utilization.However,its volatility leads to time-varying power output.Herein,a novel Seq2Seq model integrating deep learning,data denoising,and a shape-aware los...Wind speed is a crucial parameter affecting wind energy utilization.However,its volatility leads to time-varying power output.Herein,a novel Seq2Seq model integrating deep learning,data denoising,and a shape-aware loss function is proposed for accurate multistep wind speed forecasting.In this model,the wind speed data is first denoised using the maximal overlap discrete wavelet transform.Next,an encoder-decoder network based on a temporal convolutional network,bidirectional gated recurrent unit,and multihead self-attention is employed for forecasting.Additionally,to enhance the ability of the model to identify temporal dynamics,a shape-aware loss function,ITILDE-Q,is employed in the model.To verify the effectiveness of the proposed model,a comparative experiment and an ablation experiment were conducted using three datasets of measured wind speeds.Three error metrics and a similarity metric were adopted for comprehensive evaluation.The experimental results showed that the proposed model consistently outperforms benchmark models in all tested forecasting scenarios,with particularly pronounced differences in performance over longer forecast horizons.Furthermore,the synergistic interaction of the three key components contributes to the extraordinary performance of the proposed model.展开更多
Accurate wind speed prediction is crucial for stabilizing power grids with high wind energy penetration.This study presents a novel machine learning model that integrates clustering,deep learning,and transfer learning...Accurate wind speed prediction is crucial for stabilizing power grids with high wind energy penetration.This study presents a novel machine learning model that integrates clustering,deep learning,and transfer learning to mitigate accuracy degradation in 24-h forecasting.Initially,an optimized DB-SCAN(Density-Based Spatial Clustering of Applications with Noise)algorithm clusters wind fields based on wind direction,probability density,and spectral features,enhancing physical interpretability and reducing training complexity.Subsequently,a ResNet(Residual Network)extracts multi-scale patterns from decomposed wind signals,while transfer learning adapts the backbone network across clusters,cutting training time by over 90%.Finally,a CBAM(Convolutional Block Attention Module)attention mechanism is employed to prioritize features for LSTM-based prediction.Tested on the 2015 Jena wind speed dataset,the model demonstrates superior accuracy and robustness compared to state-of-the-art baselines.Key innovations include:(a)Physics-informed clustering for interpretable wind regime classification;(b)Transfer learning with deep feature extraction,preserving accuracy while minimizing training time;and(c)On the 2016 Jena wind speed dataset,the model achieves MAPE(Mean Absolute Percentage Error)values of 16.82%and 18.02%for the Weibull-shaped and Gaussian-shaped wind speed clusters,respectively,demonstrating the model’s robust generalization capacity.This framework offers an efficient and effective solution for long-term wind forecasting.展开更多
Safer,smarter,faster...In China,people prefer high-speed trains to flights if the journey time is under five hours.High-speed train travel is set to become even more attractive with the addition of a new member to the...Safer,smarter,faster...In China,people prefer high-speed trains to flights if the journey time is under five hours.High-speed train travel is set to become even more attractive with the addition of a new member to the high-speed train family:the CR450,the world’s fastest electric multiple unit(EMU).展开更多
The dual challenges of critical speed prediction inaccuracies and ambiguous vibration behaviors are present in high-speed flexible rotors,particularly in free turbine rotors in turboshaft engine systems.The study begi...The dual challenges of critical speed prediction inaccuracies and ambiguous vibration behaviors are present in high-speed flexible rotors,particularly in free turbine rotors in turboshaft engine systems.The study begins with an examination of the rotor-bearing bidirectional coupling mechanism,with a primary focus on the nonlinear characteristics of the bearing.An investigation is carried out on the mechanical modeling methodologies for four-point contact ball bearings(FPCBBs)and cylindrical roller bearings(CRBs).To address the issue of excessive computational time in traditional bearing calculation methods,the sled dog optimization(SDO)algorithm is substituted for the conventional Newton-Raphson method.A rotor-bearing coupling dynamics model is developed by the finite element and lumped mass methods,with experimental validation achieved through a simulator test rig.The effects of three internal bearing parameters in FPCBBs(arching width and raceway groove curvature coefficient)and CRBs(initial radial clearance)on the critical speed characteristics and vibrational behavior of rotorbearing coupled systems are examined.The numerical simulation results show some interesting conclusions.展开更多
High Speed on/off Valve(HSV)is an essential component in Aerospace Digital Hydraulic Systems(ADHS),which impose stringent requirements on the dynamic performance and reliability of HSV due to the extreme application e...High Speed on/off Valve(HSV)is an essential component in Aerospace Digital Hydraulic Systems(ADHS),which impose stringent requirements on the dynamic performance and reliability of HSV due to the extreme application environments.However,the faster dynamic leads to increased impact between the spool and valve body,causing severe vibration and wear,which creates a conflict between rapid dynamic and high reliability.To address this problem,a Pre-Excitation Soft Switching Control(PESSC)with both pre-excitation and reverse deceleration functionalities is proposed.The initial current is optimized through pre-excitation to accelerate the opening time,while the application of reverse voltage hastens the decline of electromagnetic force,thereby reducing the spool velocity.The PESSC simultaneously achieves both faster dynamic performance and smaller impact velocity.Moreover,the optimal deceleration voltage parameters are obtained through multi-objective optimization.Experimental results demonstrate that the optimized PESSC shortens the opening time from 2.22 ms to 1.65 ms,reduces the impact velocity by 58.3%,and lowers wear by 55.4%.These findings underline the huge potential of PESSC in enhancing the dynamic performance and reliability of HSVs,offering promising applications in aerospace.展开更多
We demonstrate a high-speed rotating slit beam shaping method for femtosecond(fs)laser three-dimensional(3D)isotropic inscription in glass materials.By integrating fs laser direct writing with a real-time rotating sli...We demonstrate a high-speed rotating slit beam shaping method for femtosecond(fs)laser three-dimensional(3D)isotropic inscription in glass materials.By integrating fs laser direct writing with a real-time rotating slit mechanism,a 3D symmetric spherical focal field distribution is created in the laser-irradiated regions of transparent substrates.The corresponding focal field distribution is theoretically calculated and validated by examining the features of laser-inscribed lines in glass samples.Moreover,we investigate the influences of laser writing speed and slit rotational speed on the fabrication resolution in glass,and discuss the formation mechanism of the generated periodic microstructures.To showcase its powerful capability for3D isotropic fabrication,the high-speed rotating slit beam shaping method is applied to create straight optical waveguides,bending optical waveguides,and hollow microchannels in the glass.The proposed method holds great potential for the facile manufacture of diverse 3D isotropic microstructures and devices within transparent materials across various applications,including advanced photonics,microoptics,micro-electromechanical systems,and microfluidics.展开更多
WE observe that the response speed of a linear timeinvariant system to a step reference input depends not only on the system parameters but also on the magnitude of the step input.Based on this observation,we demonstr...WE observe that the response speed of a linear timeinvariant system to a step reference input depends not only on the system parameters but also on the magnitude of the step input.Based on this observation,we demonstrate a method to schedule the magnitude of the reference input to achieve a faster response.展开更多
The equivalent simplification of large wind farms is essential for evaluating the safety of power systems.However,sub-synchronous oscillations can significantly affect the stability of power systems.Although detailed ...The equivalent simplification of large wind farms is essential for evaluating the safety of power systems.However,sub-synchronous oscillations can significantly affect the stability of power systems.Although detailed mathematical models of wind farms can help accurately analyze the oscillation mechanism,the solution process is complicated and may lead to problems such as the“dimensional disaster.”Therefore,this paper proposes a sub-synchronous frequency domain-equivalent modeling method for wind farms based on the nature of the equivalent resistance of the rotor,in order to analyze sub-synchronous oscillations accurately.To this end,Matlab/Simulink is used to simulate a detailed model,a single-unit model,and an equivalent model,considering a wind farm as an example.A simulation analysis is then performed under the sub-synchronous frequency to prove that the model is effective and that the wind farm equivalence model method is valid.展开更多
Nowadays with the improvement in the degree of emphasis on new energy, the wind power system has developed more and more rapidly over the world. Usually the wind plants are located in the remote areas which are far fr...Nowadays with the improvement in the degree of emphasis on new energy, the wind power system has developed more and more rapidly over the world. Usually the wind plants are located in the remote areas which are far from the load centers. Generally series compensated AC transmission and high voltage DC transmission are made use of to improve the transmission capacity as two main effective ways which can solve the problem of large scale wind power transmission. The paper describes the three kinds of impact varieties and impact mechanisms in the sub-synchronous oscillation phenomena of wind power system based on doubly fed induction generator (DFIG) wind generators. At last, we point out the important problem that should be stressed in the wind power system.展开更多
With the rapid development of wind power, wind turbines are accompanied by a large quantity of power electronic converters connected to the grid, causing changes in the characteristics of the power system and leading ...With the rapid development of wind power, wind turbines are accompanied by a large quantity of power electronic converters connected to the grid, causing changes in the characteristics of the power system and leading to increasingly serious sub-synchronous oscillation (SSO) problems, which urgently require the generalized classification and characterization of the emerging oscillation problems. This paper classifies and characterizes the emerging types of SSO caused by grid-connected wind turbines to address these issues. Finally, the impact of the typical system parameters changes on the oscillation pattern is analyzed in depth to provide effective support for the subsequent suppression and prevention of SSO.展开更多
基金funded by Sponsorship of Science and Technology Project of State Grid Xinjiang Electric Power Co.,Ltd.,grant number SGXJ0000TKJS2400168.
文摘This study presents an emergency control method for sub-synchronous oscillations in wind power gridconnected systems based on transfer learning,addressing the issue of insufficient generalization ability of traditional methods in complex real-world scenarios.By combining deep reinforcement learning with a transfer learning framework,cross-scenario knowledge transfer is achieved,significantly enhancing the adaptability of the control strategy.First,a sub-synchronous oscillation emergency control model for the wind power grid integration system is constructed under fixed scenarios based on deep reinforcement learning.A reward evaluation system based on the active power oscillation pattern of the system is proposed,introducing penalty functions for the number of machine-shedding rounds and the number of machines shed.This avoids the economic losses and grid security risks caused by the excessive one-time shedding of wind turbines.Furthermore,transfer learning is introduced into model training to enhance the model’s generalization capability in dealing with complex scenarios of actual wind power grid integration systems.By introducing the Maximum Mean Discrepancy(MMD)algorithm to calculate the distribution differences between source data and target data,the online decision-making reliability of the emergency control model is improved.Finally,the effectiveness of the proposed emergency control method for multi-scenario sub-synchronous oscillation in wind power grid integration systems based on transfer learning is analyzed using the New England 39-bus system.
文摘Steady speed control of agricultural machinery can improve operating quality and efficiency.To address the impact of farmland slope variations on the speed stability of unmanned operation agricultural machinery,a hybrid control method was proposed.This method included a hybrid controller composed of a slope-based controller and a proportional-integral-derivative(PID)controller.The speed of agricultural machinery was influenced by longitudinal forces,which were divided into two parts:one part was slope-related forces and conventional resistance,and the other was hard-to-estimate forces,such as sliding friction.For the first part,a slope-based controller was designed;for the second part,a PID controller was implemented.By combining these two controllers,the system can dynamically adjust the throttle opening and the brake master cylinder pressure,ensuring steady speed travel on sloping farmland.Simulation tests at a target speed of 7 km/h demonstrated that the proposed controller maintained a stable speed,achieving a root mean square error of 0.13 km/h and a mean absolute percentage error of 1.6%.Field tests on a practical experimental platform validated the method’s effectiveness,with results showing consistent control performance across varying slope conditions.The proposed controller demonstrated superior control performance.Experimental data verified that this method can achieve precise control of the agricultural machinery’s movement speed,meeting the stability requirements for agricultural operations.
基金supported by National Natural Science Foundation of China(51977111)the Six Talent Peaks High-level Talent Project in Jiangsu Province(XNY-025)the Special Fund of Jiangsu Province for Transformation of Scientific and Technological Achievements(BA2019045).
文摘Inertial response control(IRC)makes variable-speed wind turbine generators(WTGs)provide short-term frequency support during contingencies by releasing the kinetic energy stored in wind turbine rotors.When frequency support is terminated,the rotor speed should be restored to optimum for maximum power point tracking(MPPT).Existing IRCs utilize rotor speed recovery(RSR)strategies with a consistent power reference function.However,under real turbulent wind with alternate gusts and lulls,the consistent power reference function may fail to restore rotor speed or cause unexpected secondary frequency drop(SFD).In this regard,this paper proposes a novel adaptive RSR strategy that not only restores rotor speed via the aerodynamic power enhanced by wind gusts,but also stabilizes the turbine at wind lulls by tracking a suboptimal power curve.Experiments on a wind power-integrated power system testbed validate the proposed RSR strategy can successfully restore rotor speed while attenuating SFD under turbulent wind.
基金supported by Biological Breeding-National Science and Technology Major Project(2022ZD04008)National Natural Science Foundation of China(32201854)。
文摘Thousand-seed weight(TSW)is a critical target for genetic improvement in rapeseed(Brassica napus L.).However,phenotypic selection for this trait remains challenging due to its polygenic regulation by multiple quantitative trait loci(QTL).Here,six favorable TSW QTL alleles from two donor parents were introgress into an elite restorer line,621R,using an integrated strategy combining marker-assisted backcrossing and speed breeding protocols.Through six rounds of backcrossing and convergent crossing followed by two generations of selfing strategies,we developed 13 advanced lines with diverse TSW QTL combinations within 24 months.Field evaluations across three environments revealed that all lines exhibited significantly increased TSW in spring conditions(Minle,Gansu)and winter environments(Wuhan and Jiangling,Hubei)except for two lines which only showed increase in the spring environment.Hybridization assays using these lines as male parents crossed with two male-sterile lines(RG430A and 616A)demonstrated transgressive segregation for TSW:For RG430A-derived hybrids,all crosses significantly outperformed the original control(RG430A×621R)in Wuhan,with 8/13 and 9/13 crosses showing significant TSW increases in Minle and Jiangling,respectively.For 616A-derived hybrids,11/13 and 10/13 crosses exhibited significant TSW enhancement in Minle and Jiangling,compared to 3/13 in Wuhan.Notably,two top-performing hybrids achieved 13.0%and 6.8%higher plot yields,respectively.Our results demonstrate that strategic pyramiding of complementary TSW QTL alleles effectively enhances seed weight in rapeseed,and these improved lines represent valuable genetic resources for developing high-yield hybrids.
基金supported by the Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province(No.SCSF202307)the Basic Research Fund of CAMS(No.2023Z016)+1 种基金the National Natural Scientific Foundation of China(No.42275037)the Jiangsu Collaborative Innovation Center for Climate Change。
文摘In this study,tropical cyclone(TC)translation speed was introduced as a new similarity factor within the generalized initial value(GIV)framework,enhancing the disaster preassessment capability of the dynamical statistical analog ensemble forecast model for landfalling TC disasters(DSAEF_LTD model).Three TC translation speed indicators most relevant to TC precipitation were incorporated:the maximum speed on Day 1(the first day of TC-induced precipitation and wind occurring on land)and the average and minimum speeds over All Days(all days of TC-induced precipitation and wind occurring on land),all classified using the Kmeans clustering algorithm.Simulation experiments showed that integrating TC translation speed enhanced the model's performance.The model provided a better optimal common scheme,with the TSS UM(sum of threat scores for severe and above and extremely severe and above disasters)increasing by 2.66%(from 0.5117 to 0.5253)compared with the original model.More importantly,its preassessment ability improved significantly,with the average TSS UM for independent samples increasing by 6.43%(from 0.6488 to0.6905).The modified model demonstrated greater accuracy in capturing disaster severity and distribution of TCs with significant speed characteristics or with regular tracks.This improvement stemmed from reduced false alarms due to the selection of analogs that are more similar to the target TC.The enhanced preassessment ability can be attributed to the key role of TC translation speed,which significantly influences TC precipitation patterns and improves TC precipitation forecasting.Since precipitation is one of the most crucial disaster-causing factors,better TC precipitation forecasting leads to improved disaster preassessment outcomes.These findings emphasize the promising potential of the DSAEF_LTD model for future TC disaster research and management,contributing to the achievement of the Sustainable Development Goals set by the United Nations 2030 Agenda by strengthening coastal resilience.
基金supported by the National Key R&D Program of China(2021YFB2801000).
文摘A high-speed single-mode vertical-cavity surface-emitting laser(VCSEL)is one of the most important light sources for optical interconnects in data centers.Single-mode VCSEL can improve the transmission distance.In this letter,we demonstrate a single-mode 850 nm VCSEL with a bit rate of 60 Gb/s under NRZ modulation and 104 Gb/s under PAM4 modulation across a 100 m length of OM5 fiber,without the need for equalization or a filter.In addition,by using optical injection locking,the 3 dB bandwidth is enhanced to 68.5 GHz.
基金supported by Key R&D Program(Soft Science Project)of Shandong Province,China(No.2020CXGC011502)National Natural Science Foundation of China(Nos.62273043 and 62103049).
文摘This paper addresses the three-dimensional(3-D)approach angle constrained cooperative guidance problem for speed-varying missiles against maneuvering targets.First,the guidance problem is formulated in a relative reference frame and a virtual control input is selected.Then,the cooperative guidance law is designed on the basis of a prediction-correction framework.The time-to-go under the baseline command is estimated by an efficient prediction method with a realistic aerodynamic model and a biased command is developed by utilizing the time-to-go predictions for synchronizing different missiles'impact times.The design of the biased command is decoupled into the individual design of its direction and magnitude.It is proved that the designed cooperative guidance law can make the time-to-go consensus error converge to zero before interception.Finally,the designed guidance law is validated through a series of numerical simulations.
文摘This study aims to explore the impact of combined health education and dietary guidance on the speed of postoperative recovery in patients with gastrointestinal polyps.A specific number of patients who underwent gastrointestinal polyp resection were selected and randomly divided into a control group and an experimental group.The control group received routine nursing,while the experimental group implemented combined health education and dietary guidance on this basis.By comparing the recovery indicators of the two groups,it was found that the recovery speed of the experimental group was significantly faster than that of the control group,indicating that this combined intervention method can effectively promote patient recovery.
基金support from the National Natural Science Foundation of China(No.52271287)funding from the State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation,Tianjin University。
文摘During the hoisting process of the offshore substation,changes in the hoisting speed can affect the hoisting system.Therefore,this study set four different speed conditions for the lifting and lowering stages of the installation process,and studied the impact of different lifting and lowering speeds on the hoisting system under the same environmental conditions through numerical simulation.The results show that during the lifting operation,as the lifting speed increases,the swing motion of the substation and the installation vessel tends to decrease,and the faster the hoisting speed,the more obvious the swing suppression of the substation and the installation vessel,and the smaller the fluctuation in the tension amplitude of the slings and mooring lines.In contrast,during the lowering operation,as the lowering speed increases,the swing motion of the substation and the installation vessel tends to increase,and the faster the lowering speed,the more obvious the swing amplification effect of the substation and the installation vessel.Therefore,during hoisting operations,increasing the lifting speed and reducing the lowering speed can mitigate the motion performance of the hoisting coupling system,reduce the tension amplitude variation of the sling and mooring,and ensure the smooth progress of the hoisting operation.
基金supported by the National Natural Science Foundation of China(No.52171284)。
文摘Wind speed is a crucial parameter affecting wind energy utilization.However,its volatility leads to time-varying power output.Herein,a novel Seq2Seq model integrating deep learning,data denoising,and a shape-aware loss function is proposed for accurate multistep wind speed forecasting.In this model,the wind speed data is first denoised using the maximal overlap discrete wavelet transform.Next,an encoder-decoder network based on a temporal convolutional network,bidirectional gated recurrent unit,and multihead self-attention is employed for forecasting.Additionally,to enhance the ability of the model to identify temporal dynamics,a shape-aware loss function,ITILDE-Q,is employed in the model.To verify the effectiveness of the proposed model,a comparative experiment and an ablation experiment were conducted using three datasets of measured wind speeds.Three error metrics and a similarity metric were adopted for comprehensive evaluation.The experimental results showed that the proposed model consistently outperforms benchmark models in all tested forecasting scenarios,with particularly pronounced differences in performance over longer forecast horizons.Furthermore,the synergistic interaction of the three key components contributes to the extraordinary performance of the proposed model.
基金funded by Science and Technology Research and Development Program Project of China Railway Group Limited(No.2023-Major-02)National Natural Science Foundation of China(Grant No.52378200)Sichuan Science and Technology Program(Grant No.2024NSFSC0017).
文摘Accurate wind speed prediction is crucial for stabilizing power grids with high wind energy penetration.This study presents a novel machine learning model that integrates clustering,deep learning,and transfer learning to mitigate accuracy degradation in 24-h forecasting.Initially,an optimized DB-SCAN(Density-Based Spatial Clustering of Applications with Noise)algorithm clusters wind fields based on wind direction,probability density,and spectral features,enhancing physical interpretability and reducing training complexity.Subsequently,a ResNet(Residual Network)extracts multi-scale patterns from decomposed wind signals,while transfer learning adapts the backbone network across clusters,cutting training time by over 90%.Finally,a CBAM(Convolutional Block Attention Module)attention mechanism is employed to prioritize features for LSTM-based prediction.Tested on the 2015 Jena wind speed dataset,the model demonstrates superior accuracy and robustness compared to state-of-the-art baselines.Key innovations include:(a)Physics-informed clustering for interpretable wind regime classification;(b)Transfer learning with deep feature extraction,preserving accuracy while minimizing training time;and(c)On the 2016 Jena wind speed dataset,the model achieves MAPE(Mean Absolute Percentage Error)values of 16.82%and 18.02%for the Weibull-shaped and Gaussian-shaped wind speed clusters,respectively,demonstrating the model’s robust generalization capacity.This framework offers an efficient and effective solution for long-term wind forecasting.
文摘Safer,smarter,faster...In China,people prefer high-speed trains to flights if the journey time is under five hours.High-speed train travel is set to become even more attractive with the addition of a new member to the high-speed train family:the CR450,the world’s fastest electric multiple unit(EMU).
文摘The dual challenges of critical speed prediction inaccuracies and ambiguous vibration behaviors are present in high-speed flexible rotors,particularly in free turbine rotors in turboshaft engine systems.The study begins with an examination of the rotor-bearing bidirectional coupling mechanism,with a primary focus on the nonlinear characteristics of the bearing.An investigation is carried out on the mechanical modeling methodologies for four-point contact ball bearings(FPCBBs)and cylindrical roller bearings(CRBs).To address the issue of excessive computational time in traditional bearing calculation methods,the sled dog optimization(SDO)algorithm is substituted for the conventional Newton-Raphson method.A rotor-bearing coupling dynamics model is developed by the finite element and lumped mass methods,with experimental validation achieved through a simulator test rig.The effects of three internal bearing parameters in FPCBBs(arching width and raceway groove curvature coefficient)and CRBs(initial radial clearance)on the critical speed characteristics and vibrational behavior of rotorbearing coupled systems are examined.The numerical simulation results show some interesting conclusions.
基金supported in part by the “Pioneer”and “Leading Goose”R&D Program of Zhejiang Province(Nos.2022C01132 and 2022C01122)the National Natural Science Foundation of China(No.52005441)+3 种基金the Young Elite Scientist Sponsorship Program by CAST(No.20222024QNRC001)the State Key Laboratory of Mechanical System and Vibration,China(No.MSV202316)the Fundamental Research Funds for the Provincial Universities of Zhejiang,China(RF-A2023007)the Research Project of ZJUT,China(No.GYY-ZH-2023075)。
文摘High Speed on/off Valve(HSV)is an essential component in Aerospace Digital Hydraulic Systems(ADHS),which impose stringent requirements on the dynamic performance and reliability of HSV due to the extreme application environments.However,the faster dynamic leads to increased impact between the spool and valve body,causing severe vibration and wear,which creates a conflict between rapid dynamic and high reliability.To address this problem,a Pre-Excitation Soft Switching Control(PESSC)with both pre-excitation and reverse deceleration functionalities is proposed.The initial current is optimized through pre-excitation to accelerate the opening time,while the application of reverse voltage hastens the decline of electromagnetic force,thereby reducing the spool velocity.The PESSC simultaneously achieves both faster dynamic performance and smaller impact velocity.Moreover,the optimal deceleration voltage parameters are obtained through multi-objective optimization.Experimental results demonstrate that the optimized PESSC shortens the opening time from 2.22 ms to 1.65 ms,reduces the impact velocity by 58.3%,and lowers wear by 55.4%.These findings underline the huge potential of PESSC in enhancing the dynamic performance and reliability of HSVs,offering promising applications in aerospace.
基金supported by the National Key Research and Development Program of China(2022YFA1404800)National Natural Science Foundation of China(12174107,12004221,12192254,92250304,W2441005,12334014,12192251)+4 种基金Natural Science Foundation of Shandong Province(ZR2024QA024,ZR2021ZD02)Postdoctoral Innovation Talents Support Program of Shandong Province(No.SDBX2019005)Shanghai Municipal Science and Technology Major ProjectFundamental Research Funds for the Central UniversitiesEngineering Research Center for Nanophotonics&Advanced Instrument,Ministry of Education,East China Normal University(No.2023nmc005)。
文摘We demonstrate a high-speed rotating slit beam shaping method for femtosecond(fs)laser three-dimensional(3D)isotropic inscription in glass materials.By integrating fs laser direct writing with a real-time rotating slit mechanism,a 3D symmetric spherical focal field distribution is created in the laser-irradiated regions of transparent substrates.The corresponding focal field distribution is theoretically calculated and validated by examining the features of laser-inscribed lines in glass samples.Moreover,we investigate the influences of laser writing speed and slit rotational speed on the fabrication resolution in glass,and discuss the formation mechanism of the generated periodic microstructures.To showcase its powerful capability for3D isotropic fabrication,the high-speed rotating slit beam shaping method is applied to create straight optical waveguides,bending optical waveguides,and hollow microchannels in the glass.The proposed method holds great potential for the facile manufacture of diverse 3D isotropic microstructures and devices within transparent materials across various applications,including advanced photonics,microoptics,micro-electromechanical systems,and microfluidics.
文摘WE observe that the response speed of a linear timeinvariant system to a step reference input depends not only on the system parameters but also on the magnitude of the step input.Based on this observation,we demonstrate a method to schedule the magnitude of the reference input to achieve a faster response.
基金supported by the National Key R&D Program of China“Response-driven intelligent enhanced analysis and control for bulk power system stability”(No.2021YFB2400800)。
文摘The equivalent simplification of large wind farms is essential for evaluating the safety of power systems.However,sub-synchronous oscillations can significantly affect the stability of power systems.Although detailed mathematical models of wind farms can help accurately analyze the oscillation mechanism,the solution process is complicated and may lead to problems such as the“dimensional disaster.”Therefore,this paper proposes a sub-synchronous frequency domain-equivalent modeling method for wind farms based on the nature of the equivalent resistance of the rotor,in order to analyze sub-synchronous oscillations accurately.To this end,Matlab/Simulink is used to simulate a detailed model,a single-unit model,and an equivalent model,considering a wind farm as an example.A simulation analysis is then performed under the sub-synchronous frequency to prove that the model is effective and that the wind farm equivalence model method is valid.
文摘Nowadays with the improvement in the degree of emphasis on new energy, the wind power system has developed more and more rapidly over the world. Usually the wind plants are located in the remote areas which are far from the load centers. Generally series compensated AC transmission and high voltage DC transmission are made use of to improve the transmission capacity as two main effective ways which can solve the problem of large scale wind power transmission. The paper describes the three kinds of impact varieties and impact mechanisms in the sub-synchronous oscillation phenomena of wind power system based on doubly fed induction generator (DFIG) wind generators. At last, we point out the important problem that should be stressed in the wind power system.
基金National Key Research and Development Program of China under Grant No.2017YFB0902002.
文摘With the rapid development of wind power, wind turbines are accompanied by a large quantity of power electronic converters connected to the grid, causing changes in the characteristics of the power system and leading to increasingly serious sub-synchronous oscillation (SSO) problems, which urgently require the generalized classification and characterization of the emerging oscillation problems. This paper classifies and characterizes the emerging types of SSO caused by grid-connected wind turbines to address these issues. Finally, the impact of the typical system parameters changes on the oscillation pattern is analyzed in depth to provide effective support for the subsequent suppression and prevention of SSO.
