The magnitude of dynamic load produced by high-speed trains depends on many factors,of which train speed is the most critical one.However,it is quite difficult to determine the effect of train speed on dynamic load us...The magnitude of dynamic load produced by high-speed trains depends on many factors,of which train speed is the most critical one.However,it is quite difficult to determine the effect of train speed on dynamic load using the theoretical methods due to the complexity of the interaction between vehicle and track-subgrade.Thus large-scale model test has gradually become an important approach for studying dynamic responses of ballastless track-subgrade of high-speed railway.In this study,a full-scale model of ballastless track-subgrade was constructed in accordance with the design and construction standards for Shanghai-Nanjing intercity high-speed railway line firstly.Then,the dynamic strain of slab and the dynamic earth pressure of subgrade were measured by conducting single wheel axle excitation test.In addition,the relationship between the dynamic load magnification factor（DLF） and the train speed was obtained.Finally,the DLF of track-subgrade under different train speeds was proposed,similar to that given by German Railway Standard.展开更多
This paper deals with an experimental study on dynamic fracture speed of three point bending specimen and cylindrical specimen made of epoxy resin by means of silver conductive painting grid. According to the test res...This paper deals with an experimental study on dynamic fracture speed of three point bending specimen and cylindrical specimen made of epoxy resin by means of silver conductive painting grid. According to the test results ,the relations between fracture load ,fracture speed and loading speed are discussed and the features of final fracture surfaces are analysed in detail.展开更多
As energy efficiency and indoor comfort increasingly become key standards in modern residential and office environments,research on intelligent fan speed control systems has become particularly important.This study ai...As energy efficiency and indoor comfort increasingly become key standards in modern residential and office environments,research on intelligent fan speed control systems has become particularly important.This study aims to develop a temperature-feedback-based fan speed optimization strategy to achieve higher energy efficiency and user comfort.Firstly,by analyzing existing fan speed control technologies,their main limitations are identified,such as the inability to achieve smooth speed transitions.To address this issue,a BP-PID speed control algorithm is designed,which dynamically adjusts fan speed based on indoor temperature changes.Experimental validation demonstrates that the designed system can achieve smooth speed transitions compared to traditional fan systems while maintaining stable indoor temperatures.Furthermore,the real-time responsiveness of the system is crucial for enhancing user comfort.Our research not only demonstrates the feasibility of temperature-based fan speed optimization strategies in both theory and practice but also provides valuable insights for energy management in future smart home environments.Ultimately,this research outcome will facilitate the development of smart home systems and have a positive impact on environmental sustainability.展开更多
Flexible net barriers are a new type of effective mitigation measure against debris flows in valleys and can affect the kinematic energy and mass of debris flows. Here, ten flume tests were performed to study the dyna...Flexible net barriers are a new type of effective mitigation measure against debris flows in valleys and can affect the kinematic energy and mass of debris flows. Here, ten flume tests were performed to study the dynamic behaviours of debris flows with differences in volumes, concentrations(solid volume fraction), and travel distances after interception by a uniform flexible net barrier. A high-speed camera was used to monitor the whole test process, and their dynamic behaviours were recorded. A preliminary computational framework on energy conversion is proposed according to the deposition mechanisms and outflow of debris flow under the effects of the flexible net barrier. The experimental results show that the dynamic interaction process between a debris flow and the flexible net barrier can be divided into two stages:(a) the two-phase impact of the leading edge of the debris flow with the net and(b) collision and friction between the body of the debris flow and intercepted debris material. The approach velocity of a debris flow decreases sharply(a maximum of 63%) after the interception by the net barrier, and the mass ratio of the debris material being intercepted and the kinetic energy ratio of the debris material being absorbed by the net barrier are close due to the limited interception efficiency of the flexible net barrier, which is believed to be related to the flexibility. The energy ratio of outflow is relative small despite the large permeability of the flexible net barrier.展开更多
Diagnosing the operational status of High-voltage circuit breakers(HVCBs)is crucial for ensuring the safe and stable operation of the grid.Mechanical characteristic parameters are effective indicators for evaluating t...Diagnosing the operational status of High-voltage circuit breakers(HVCBs)is crucial for ensuring the safe and stable operation of the grid.Mechanical characteristic parameters are effective indicators for evaluating the performance of HVCBs.Recent studies have shown that the actions of the springs and cams in HVCBs can be used to detect the operational status of the mechanical mechanisms,which occur extremely quickly,usually in the speed of m/ms.In this paper,dynamic vision sensing technology was employed to rapidly and dynamically capture the movements of the springs and cam of the HPL245B1 HVCB.The data volume of a single experiment is less than 100 MB,whereas the data collected by a high-speed camera at the same frame rate exceeds 1 GB.Action data streams of the springs and cam were obtained and images were reconstructed from the event streams.The Lucas-Kanade optical flow algorithm and the normalised cross-correlation algorithm are applied to calculate the parameters of spring deformation characteristics and cam rotation characteristics for mechanical feature detection of HVCBs.This is the first attempt to utilize brain-inspired hardware technology for the status monitoring of electrical equipment.The advantages of dynamic vision sensing technology,such as high dynamic range,low data transmission,and low energy con-sumption,also offer significant benefits for air discharge monitoring and status moni-toring of electrical equipment.展开更多
A high-speed dynamic-range-extended white light interferometry(HS-DRE-WLI)system is developed for fast,high-resolution 3D surface profiling across varying reflectance levels.The system combines high-speed fiber-stretc...A high-speed dynamic-range-extended white light interferometry(HS-DRE-WLI)system is developed for fast,high-resolution 3D surface profiling across varying reflectance levels.The system combines high-speed fiber-stretcher-based optical path difference modulation with an asymmetric line-illumination technique to en-hance imaging speed and dynamic range.Chromatic and polarization-induced distortions are minimized through dispersion compensation using optimized fiber lengths and a Faraday rotator,achieving 14.2-pm axial resolution.Validated on diverse samples,the system captures fine and large-scale features with high fidelity,demonstrating strong potential for industrial and biomedical applications requiring accurate,robust surface measurements.展开更多
This paper deals with both the leading train and the following train in a train tracking under a four-aspect fixed autoblock system in order to study the optimum operating strategy for energy saving. After analyzing t...This paper deals with both the leading train and the following train in a train tracking under a four-aspect fixed autoblock system in order to study the optimum operating strategy for energy saving. After analyzing the working principle of the four-aspect fixed autoblock system, an energy-saving control model is created based on the dynamics equation of the Wains. In addition to safety, energy consumption and time error are the main concerns of the model. Based on this model, dynamic speed constraints of the following train are proposed, defined by the leading gain dynamically. At the same time, the static speed constraints defined by the line conditions are also taken into account. The parallel genetic algorithm is used to search the optimum operating strategy. In order to simplify the solving process, the external punishment function is adopted to transform this problem with constraints to the one without constraints. By using the real number coding and the strategy of dividing ramps into three parts, the convergence of GA is accelerated and the length of chromosomes is shortened. The simulation result from a four-aspect fixed autoblock system simulation platform shows that the method can reduce the energy consumption effectively in the premise of ensuring safety and punctuality.展开更多
High wind power penetration(WPP)is challenging system frequency stability.As a countermeasure,virtual inertia controls are introduced,utilizing kinetic energy(KE)stored in wind turbine generators(WTGs)for frequency re...High wind power penetration(WPP)is challenging system frequency stability.As a countermeasure,virtual inertia controls are introduced,utilizing kinetic energy(KE)stored in wind turbine generators(WTGs)for frequency regulation.Without restoration,generation efficiency of WTGs will be degraded after inertia contribution.To counter this issue,we propose an inertia control scheme of a doubly fed induction generator(DFIG),aiming at achieving dynamic inertia recovery regarding both KE and DC link energy.An asymmetrical droop control,referred to as the rate of change of frequency(RoCoF),is proposed for KE management.The upper boundary of droop gain is extended to give full play to converters and is revised,considering the system frequency state,to counter positive feedback issues induced by reversible gain regulation,which is restricted by KE to ensure stable operations as well.The inertial DC energy needed to cooperate with KE control regarding countering small fluctuations,is improved with an orderly recovery behavior.Case studies are conducted under dynamic wind conditions and the results indicate that with our proposed scheme,the ability of dynamic inertia recovery can be obtained,bringing DFIG higher generation efficiency and more adequate operation margin for sustained regulation.Essentially,the inertial frequency response and fluctuation suppression ability is well maintained.展开更多
A 2.5 GS/s 14-bit D/A converter（DAC） with 8 to 1 MUX is presented. This 14-bit DAC uses a ＂5＋9＂segment PMOS current-steering architecture. A bias circuit which ensures the PMOS current source obtains a larger out...A 2.5 GS/s 14-bit D/A converter（DAC） with 8 to 1 MUX is presented. This 14-bit DAC uses a ＂5＋9＂segment PMOS current-steering architecture. A bias circuit which ensures the PMOS current source obtains a larger output impedance under every PVT（process, source voltage and temperature） corner is also presented. The8 to 1 MUX has a 3 stage structure, and a proper timing sequence is designed to ensure reliable data synthesis. A DEM function which is merged with a ＂5-31＂decoder is used to improve the DAC＇s dynamic performance. This DAC is embedded in a 2.5 GHz direct digital frequency synthesizer（DDS） chip, and is implemented in a 0.18 m CMOS technology, occupies 4.86 2. 28 mm-2 including bond pads（DAC only）, and the measured performance is SFDR 〉 40 d B（with and without DEM） for output signal frequency up to 1 GHz. Compared with other present published DACs with a non-analog-resample structure（means return-to-zero or quad-switch structure is unutilized）,this paper DAC＇s clock frequency（2.5 GHz） and higher output frequency SFDR（〉 40 d B, up to 1 GHz） has some competition.展开更多
基金the National Natural Science Foundation of China(51225804,U1234204,51222803,51178418)for the financial supports
文摘The magnitude of dynamic load produced by high-speed trains depends on many factors,of which train speed is the most critical one.However,it is quite difficult to determine the effect of train speed on dynamic load using the theoretical methods due to the complexity of the interaction between vehicle and track-subgrade.Thus large-scale model test has gradually become an important approach for studying dynamic responses of ballastless track-subgrade of high-speed railway.In this study,a full-scale model of ballastless track-subgrade was constructed in accordance with the design and construction standards for Shanghai-Nanjing intercity high-speed railway line firstly.Then,the dynamic strain of slab and the dynamic earth pressure of subgrade were measured by conducting single wheel axle excitation test.In addition,the relationship between the dynamic load magnification factor（DLF） and the train speed was obtained.Finally,the DLF of track-subgrade under different train speeds was proposed,similar to that given by German Railway Standard.
文摘This paper deals with an experimental study on dynamic fracture speed of three point bending specimen and cylindrical specimen made of epoxy resin by means of silver conductive painting grid. According to the test results ,the relations between fracture load ,fracture speed and loading speed are discussed and the features of final fracture surfaces are analysed in detail.
文摘As energy efficiency and indoor comfort increasingly become key standards in modern residential and office environments,research on intelligent fan speed control systems has become particularly important.This study aims to develop a temperature-feedback-based fan speed optimization strategy to achieve higher energy efficiency and user comfort.Firstly,by analyzing existing fan speed control technologies,their main limitations are identified,such as the inability to achieve smooth speed transitions.To address this issue,a BP-PID speed control algorithm is designed,which dynamically adjusts fan speed based on indoor temperature changes.Experimental validation demonstrates that the designed system can achieve smooth speed transitions compared to traditional fan systems while maintaining stable indoor temperatures.Furthermore,the real-time responsiveness of the system is crucial for enhancing user comfort.Our research not only demonstrates the feasibility of temperature-based fan speed optimization strategies in both theory and practice but also provides valuable insights for energy management in future smart home environments.Ultimately,this research outcome will facilitate the development of smart home systems and have a positive impact on environmental sustainability.
基金supported by the National Natural Science Foundation of China (51639007)the Youth Science and Technology Fund of Sichuan Province (2016JQ0011)the Science and Technology Fund of Chengdu Water Authority (14H1055).
文摘Flexible net barriers are a new type of effective mitigation measure against debris flows in valleys and can affect the kinematic energy and mass of debris flows. Here, ten flume tests were performed to study the dynamic behaviours of debris flows with differences in volumes, concentrations(solid volume fraction), and travel distances after interception by a uniform flexible net barrier. A high-speed camera was used to monitor the whole test process, and their dynamic behaviours were recorded. A preliminary computational framework on energy conversion is proposed according to the deposition mechanisms and outflow of debris flow under the effects of the flexible net barrier. The experimental results show that the dynamic interaction process between a debris flow and the flexible net barrier can be divided into two stages:(a) the two-phase impact of the leading edge of the debris flow with the net and(b) collision and friction between the body of the debris flow and intercepted debris material. The approach velocity of a debris flow decreases sharply(a maximum of 63%) after the interception by the net barrier, and the mass ratio of the debris material being intercepted and the kinetic energy ratio of the debris material being absorbed by the net barrier are close due to the limited interception efficiency of the flexible net barrier, which is believed to be related to the flexibility. The energy ratio of outflow is relative small despite the large permeability of the flexible net barrier.
基金National Natural Science Foundation of China,Grant/Award Numbers:52077118,62411560155Guangdong Basic and Applied Basic Research Foundation,Grant/Award Number:2024A1515012597。
文摘Diagnosing the operational status of High-voltage circuit breakers(HVCBs)is crucial for ensuring the safe and stable operation of the grid.Mechanical characteristic parameters are effective indicators for evaluating the performance of HVCBs.Recent studies have shown that the actions of the springs and cams in HVCBs can be used to detect the operational status of the mechanical mechanisms,which occur extremely quickly,usually in the speed of m/ms.In this paper,dynamic vision sensing technology was employed to rapidly and dynamically capture the movements of the springs and cam of the HPL245B1 HVCB.The data volume of a single experiment is less than 100 MB,whereas the data collected by a high-speed camera at the same frame rate exceeds 1 GB.Action data streams of the springs and cam were obtained and images were reconstructed from the event streams.The Lucas-Kanade optical flow algorithm and the normalised cross-correlation algorithm are applied to calculate the parameters of spring deformation characteristics and cam rotation characteristics for mechanical feature detection of HVCBs.This is the first attempt to utilize brain-inspired hardware technology for the status monitoring of electrical equipment.The advantages of dynamic vision sensing technology,such as high dynamic range,low data transmission,and low energy con-sumption,also offer significant benefits for air discharge monitoring and status moni-toring of electrical equipment.
基金National Research Foundation of Korea(NRFRS-2021-NR060086)Korea Evaluation Institute of Industrial Technology(1415181752)Institute of Civil-Military Technology Cooperation(23-SF-EL-09).
文摘A high-speed dynamic-range-extended white light interferometry(HS-DRE-WLI)system is developed for fast,high-resolution 3D surface profiling across varying reflectance levels.The system combines high-speed fiber-stretcher-based optical path difference modulation with an asymmetric line-illumination technique to en-hance imaging speed and dynamic range.Chromatic and polarization-induced distortions are minimized through dispersion compensation using optimized fiber lengths and a Faraday rotator,achieving 14.2-pm axial resolution.Validated on diverse samples,the system captures fine and large-scale features with high fidelity,demonstrating strong potential for industrial and biomedical applications requiring accurate,robust surface measurements.
基金supported by the National Science & Technology Pillar Program during the Eleventh Five-Year Plan Period of China (No.2009BAG12A05)
文摘This paper deals with both the leading train and the following train in a train tracking under a four-aspect fixed autoblock system in order to study the optimum operating strategy for energy saving. After analyzing the working principle of the four-aspect fixed autoblock system, an energy-saving control model is created based on the dynamics equation of the Wains. In addition to safety, energy consumption and time error are the main concerns of the model. Based on this model, dynamic speed constraints of the following train are proposed, defined by the leading gain dynamically. At the same time, the static speed constraints defined by the line conditions are also taken into account. The parallel genetic algorithm is used to search the optimum operating strategy. In order to simplify the solving process, the external punishment function is adopted to transform this problem with constraints to the one without constraints. By using the real number coding and the strategy of dividing ramps into three parts, the convergence of GA is accelerated and the length of chromosomes is shortened. The simulation result from a four-aspect fixed autoblock system simulation platform shows that the method can reduce the energy consumption effectively in the premise of ensuring safety and punctuality.
文摘High wind power penetration(WPP)is challenging system frequency stability.As a countermeasure,virtual inertia controls are introduced,utilizing kinetic energy(KE)stored in wind turbine generators(WTGs)for frequency regulation.Without restoration,generation efficiency of WTGs will be degraded after inertia contribution.To counter this issue,we propose an inertia control scheme of a doubly fed induction generator(DFIG),aiming at achieving dynamic inertia recovery regarding both KE and DC link energy.An asymmetrical droop control,referred to as the rate of change of frequency(RoCoF),is proposed for KE management.The upper boundary of droop gain is extended to give full play to converters and is revised,considering the system frequency state,to counter positive feedback issues induced by reversible gain regulation,which is restricted by KE to ensure stable operations as well.The inertial DC energy needed to cooperate with KE control regarding countering small fluctuations,is improved with an orderly recovery behavior.Case studies are conducted under dynamic wind conditions and the results indicate that with our proposed scheme,the ability of dynamic inertia recovery can be obtained,bringing DFIG higher generation efficiency and more adequate operation margin for sustained regulation.Essentially,the inertial frequency response and fluctuation suppression ability is well maintained.
基金Project supported by the National Natural Science Foundation of China(Nos.61006027,61176030)the Research Foundation of Key Laboratory of Analog Integrated Circuit(Nos.9140C0902120C09034,9140c090204130c09042)the Fundamental Research Funds for the Central Universities of China(No.ZYGX2012J003)
文摘A 2.5 GS/s 14-bit D/A converter（DAC） with 8 to 1 MUX is presented. This 14-bit DAC uses a ＂5＋9＂segment PMOS current-steering architecture. A bias circuit which ensures the PMOS current source obtains a larger output impedance under every PVT（process, source voltage and temperature） corner is also presented. The8 to 1 MUX has a 3 stage structure, and a proper timing sequence is designed to ensure reliable data synthesis. A DEM function which is merged with a ＂5-31＂decoder is used to improve the DAC＇s dynamic performance. This DAC is embedded in a 2.5 GHz direct digital frequency synthesizer（DDS） chip, and is implemented in a 0.18 m CMOS technology, occupies 4.86 2. 28 mm-2 including bond pads（DAC only）, and the measured performance is SFDR 〉 40 d B（with and without DEM） for output signal frequency up to 1 GHz. Compared with other present published DACs with a non-analog-resample structure（means return-to-zero or quad-switch structure is unutilized）,this paper DAC＇s clock frequency（2.5 GHz） and higher output frequency SFDR（〉 40 d B, up to 1 GHz） has some competition.
