The component of light in the 3<sup>rd</sup> dimension decreases as light enters the 4<sup>th</sup> dimension created by a Black Hole. Hence particles moving in 3-D space will emit radiation du...The component of light in the 3<sup>rd</sup> dimension decreases as light enters the 4<sup>th</sup> dimension created by a Black Hole. Hence particles moving in 3-D space will emit radiation due to the Cherenkov Effect. Gravity and acceleration are the same according to Einstein’s Equivalence Principle. Density also has the same effect as gravity because gravity attracts matter thereby increasing matter density. The laws of Physics and all the constants of nature such as the Speed of light, Planck’s constant, the Gravitational constant, and so on are a function of the dimension of the space they are in since the vacuum energy density of each higher dimension is greater. We analyze the graph of the accelerated expansion of the Universe to calculate the acceleration for small Redshift z and predict what will happen for larger z values.展开更多
To satisfy the need of high speed NC (numerical control) machining, an acceleration and deceleration (acc/dec) control model is proposed, and the speed curve is also constructed by the cubic polynomial. The proposed c...To satisfy the need of high speed NC (numerical control) machining, an acceleration and deceleration (acc/dec) control model is proposed, and the speed curve is also constructed by the cubic polynomial. The proposed control model provides continuity of acceleration, which avoids the intense vibration in high speed NC machining. Based on the discrete characteristic of the data sampling interpolation, the acc/dec control discrete mathematical model is also set up and the discrete expression of the theoretical deceleration length is obtained furthermore. Aiming at the question of hardly predetermining the deceleration point in acc/dec control before interpolation, the adaptive acc/dec control algorithm is deduced from the expressions of the theoretical deceleration length. The experimental result proves that the acc/dec control model has the characteristic of easy implementation, stable movement and low impact. The model has been applied in multi-axes high speed micro fabrication machining successfully.展开更多
A linear acceleration sensor,which is inspired by the human balance organ,is designed and prepared. It uses a liquid mass-block and a symmetrical-electrodes metal-core polyvinylidene fluoride fiber(SMPF)as the sensor ...A linear acceleration sensor,which is inspired by the human balance organ,is designed and prepared. It uses a liquid mass-block and a symmetrical-electrodes metal-core polyvinylidene fluoride fiber(SMPF)as the sensor element. The output signal of the sensor has an exponential relationship with the excitation amplitude of the impacting vibration. It is capable of detecting the amplitude and the correct frequency for sinusoidal excitations using an exponential correlation. The experiments indicate that both the output signal of the sensor and the resonance frequency increase substantially with increasing diameter of the metal core. The first-order resonance frequencies of the sensors with 40,60,and 80 μm diameter metal wires are below 10 Hz,which is near the range of human body motion frequencies.展开更多
Numerous wireless networks have emerged that can be used for short communication ranges where the infrastructure-based networks may fail because of their installation and cost.One of them is a sensor network with embe...Numerous wireless networks have emerged that can be used for short communication ranges where the infrastructure-based networks may fail because of their installation and cost.One of them is a sensor network with embedded sensors working as the primary nodes,termed Wireless Sensor Networks(WSNs),in which numerous sensors are connected to at least one Base Station(BS).These sensors gather information from the environment and transmit it to a BS or gathering location.WSNs have several challenges,including throughput,energy usage,and network lifetime concerns.Different strategies have been applied to get over these restrictions.Clustering may,therefore,be thought of as the best way to solve such issues.Consequently,it is crucial to analyze effective Cluster Head(CH)selection to maximize efficiency throughput,extend the network lifetime,and minimize energy consumption.This paper proposed an Accelerated Particle Swarm Optimization(APSO)algorithm based on the Low Energy Adaptive Clustering Hierarchy(LEACH),Neighboring Based Energy Efficient Routing(NBEER),Cooperative Energy Efficient Routing(CEER),and Cooperative Relay Neighboring Based Energy Efficient Routing(CR-NBEER)techniques.With the help of APSO in the implementation of the WSN,the main methodology of this article has taken place.The simulation findings in this study demonstrated that the suggested approach uses less energy,with respective energy consumption ranges of 0.1441 to 0.013 for 5 CH,1.003 to 0.0521 for 10 CH,and 0.1734 to 0.0911 for 15 CH.The sending packets ratio was also raised for all three CH selection scenarios,increasing from 659 to 1730.The number of dead nodes likewise dropped for the given combination,falling between 71 and 66.The network lifetime was deemed to have risen based on the results found.A hybrid with a few valuable parameters can further improve the suggested APSO-based protocol.Similar to underwater,WSN can make use of the proposed protocol.The overall results have been evaluated and compared with the existing approaches of sensor networks.展开更多
Intentional electromagnetic interference is a serious threat to the safety of electronic devices. Multiple electromagnetic pulses will be coupled and transmitted to electronic devices through the cables.Accumulative e...Intentional electromagnetic interference is a serious threat to the safety of electronic devices. Multiple electromagnetic pulses will be coupled and transmitted to electronic devices through the cables.Accumulative effects are generated, which make it easier for damage to occur in the electronic devices. In this article, the working principle of micro-silicon acceleration sensors is introduced. The accumulative effects of multiple pulses on acceleration sensors is studied by a large number of injection experiments.The accumulation trends of multiple pulses with different pulse numbers and intervals are analyzed. The damaged structures inside abnormal sensor amplifiers were observed via optical microscopy and scanning electron microscopy. The experimental results show that the accumulative effect is strengthened with increased pulse number or decreased pulse interval, and the threshold voltage for multiple pulses on the acceleration sensor decreases. The threshold voltage for a single pulse is 321.57 V. When the pulse interval is 1 μs and the pulse number is 5, the threshold voltage for multiple pulses is 163.42 V,which is reduced by 49.12% compared with a single pulse. These results provide a reference for the damage design of electromagnetic pulse weapons.展开更多
This paper suggests a novel model-based nonlinear DC motor speed regulator without the use of a current sensor.The current dynamics,machine parameters and mismatched load variations are considered.The proposed control...This paper suggests a novel model-based nonlinear DC motor speed regulator without the use of a current sensor.The current dynamics,machine parameters and mismatched load variations are considered.The proposed controller is designed to include an active damping term that regulates the motor speed in accordance with the first-order low-pass filter dynamics through the pole-zero cancellation.Meanwhile,the angular acceleration and its reference are obtained from simple first-order estimators using only the speed information.The effectiveness is experimentally verified using hardware comprising the QUBEServo2,myRIO-1900,and LabVIEW.展开更多
We present a Machian model of Quantum Cosmology with full dark matter and light speed expansion and rotation. During galaxy formation and evolution, fraction of dark matter transforms to visible matter with a relation...We present a Machian model of Quantum Cosmology with full dark matter and light speed expansion and rotation. During galaxy formation and evolution, fraction of dark matter transforms to visible matter with a relation of the form, m_vis = constant * (m_dark)<sup>2/3</sup>. Using this relation and replacing MOND’s “critical acceleration” with “current cosmic maximum angular acceleration”, galactic flat rotation speed range of (50 to 500) km/sec can be fitted well. Estimated flat rotation speeds of DD168, Milky Way and UGC12591 are 49.96 km/sec, 199.66 km/sec and 521.75 km/sec respectively. Based on these striking coincidences, it is possible to say that, MOND’s approach is implicitly connected with cosmological estimation of 95% invisible matter. With reference to SPARC data for flat rotation speeds and current cosmic maximum angular acceleration, galactic total mass can be estimated. Considering galactic total mass, galactic visible mass and dark mass can be estimated. Proceeding further, galactic working radii, angular velocity and visible matter density can be estimated. Estimated Milky Way’s effective radius is 293 kpc. Even though, this model is free from “big bang”, “inflation”, “dark energy”, “flatness” and “red shift” issues, at 2.722 K, estimated present Hubble parameter is 66.24 km/sec/Mpc, cosmic radius is 146.3 times of the Hubble radius, angular velocity is 146.3 times lower than the Hubble parameter and cosmic age is 146.3 times of the Hubble age. With future observations and advanced telescopes, it may be possible to see far distant galaxies and very old stars far beyond the current observable cosmic radius.展开更多
Since high-speed railway bridges are subjected to cyclic loading by the continuous wheel loads traveling at high speed and regular spacing, their dynamic behavior is of extreme importance and has significant influence...Since high-speed railway bridges are subjected to cyclic loading by the continuous wheel loads traveling at high speed and regular spacing, their dynamic behavior is of extreme importance and has significant influence on the riding safety of the trains. To secure the riding safety of the trains, advanced railway countries have limited the vertical acceleration of the bridge slab below critical values at specific frequency domains. Since these limitations of the vertical acceleration constitute the most important factors in securing the dynamic safety of the bridges, these countries have opted for a conservative approach. However, the Korean specifications limit only the size of the peak acceleration without considering the frequency domain, which impede significantly rational evaluation of the high-speed railway bridges in Korea. In addition, the evaluation of the acceleration without consideration of the frequency domain is the cause of disagreement between the dynamic analysis and measurement results. This study conducts field monitoring and dynamic analysis on high-speed railway bridges to gather the acceleration signals and compare them. Significant difference in the size of the vertical acceleration was observed between the measured and dynamic analysis accelerations when discarding the frequency domain as done in the current specifications. The comparison of the accelerations considering only low frequencies below 30 Hz showed that the dynamic analysis reflected accurately the measured vertical acceleration.展开更多
Gearbox, as the crucial transmission equipment of high-speed train drive system, bears mainly the impact of wheel-rail excitation during its application, resulting in fatigue failure of the housing structure. In order...Gearbox, as the crucial transmission equipment of high-speed train drive system, bears mainly the impact of wheel-rail excitation during its application, resulting in fatigue failure of the housing structure. In order to analyze the vibration characteristics of the high-speed train gearbox housing, a test had been performed under operating condition on Wuhan-Guangzhou High-Speed Railway, where a host of vibration characteristics of different parts of housing had been obtained, and vibration signals had also been comparatively analyzed using acceleration amplitude spectrum and equivalent acceleration amplitude method. The result showed that the vibration level of the measuring point A on the joint part of the gearbox housing and axle bearing block was higher than that of the measuring point B on the upper part of the gearbox housing, both horizontally and vertically. And there existed attenuation during the transmission process of vibration from point A to Point B. Further, when a train was moving at a high speed, the gearbox vibration at the head carriage was better than that at the tail carriage. In addition, when a train slowed down from 300 km/h to 200 km/h, the horizontal equivalent acceleration amplitude dropped by 58% while the vertical one declined by 62%. Equivalent acceleration amplitude method was used to identify the vibration relations among different parts of housing, and the validity and applicability of this method were verified by data analysis. The study provided reference to ensure the operating safety of high-speed train drive system and design of new housing structure.展开更多
Based on piezoresistive effect, the acceleration sensitivity of multi-walled canbon nanotube (MWNT) films was investigated. A three-point bending technique was presented to measure the piezoresistivity, which used a b...Based on piezoresistive effect, the acceleration sensitivity of multi-walled canbon nanotube (MWNT) films was investigated. A three-point bending technique was presented to measure the piezoresistivity, which used a bending stress applied to the samples while making MWNT films wheeling with a rotational machine. The experimental results showed that the fractional increase in resistance increases linearly versus the increase of centripetal acceleration, and there is a linear relationship between the acceleration and the strain. These shed light on using carbon nanotube films as acceleration sensors for many potential applications.展开更多
The high speed maglev is mainly characterized by propulsion using linear synchronous motor (LSM) and vehicle levitation from the guideway surface. In LSM propulsion control, the position detection sensor is used to de...The high speed maglev is mainly characterized by propulsion using linear synchronous motor (LSM) and vehicle levitation from the guideway surface. In LSM propulsion control, the position detection sensor is used to detect running vehicle position for synchronized current generation. To maintain the stable levitating condition during vehicle running, the irregularity of guideway surface should be monitored by sensors measuring the displacement and acceleration between vehicle and guideway. In this study, the application methods of these sensors in the high speed maglev are investigated and through the experiments by using the small-scale test bed, the validity of examined methods is confirmed.展开更多
According to the verification regulation of the Wind Direction and Wind Speed Sensor of Automatic Meteorological Station[JJG(meteorological)004-2011],relying on the wind tunnel laboratory of Hebei meteorological measu...According to the verification regulation of the Wind Direction and Wind Speed Sensor of Automatic Meteorological Station[JJG(meteorological)004-2011],relying on the wind tunnel laboratory of Hebei meteorological measurement station,EL15-1 A type of wind speed sensor in the automatic weather station was verified.The experimental data of sensor verification in different laboratory environments were obtained through data comparison.Using standard wind speed measurement formula,the influence of laboratory temperature,humidity and air pressure on verification results was analyzed quantitatively.The results showed that laboratory temperature had the greatest influence on the verification results of this type of sensor,while the humidity and air pressure had less influence.Therefore,it should be noted that the temperature change in the laboratory should not be too large in the process of verification,so as to improve the accuracy of the verification results.展开更多
In order to consider the influence of steel pole on the measurement of wind speed sensors and determinate the installation position of wind speed sensors, the flow field around wind speed sensors was investigated. Bas...In order to consider the influence of steel pole on the measurement of wind speed sensors and determinate the installation position of wind speed sensors, the flow field around wind speed sensors was investigated. Based on the three-dimensional steady Reynolds-averaged Navier-Stokes equations and k-ε double equations turbulent model, the field flow around the wind speed sensor and the steel pole along a high-speed railway was simulated on an unstructured grid. The grid-independent validation was conducted and the accuracy of the present numerical simulation method was validated by experiments and simulations carried out by previous researchers. Results show that the steel pole has a significant influence on the measurement results of wind speed sensors. As the distance between two wind speed sensors is varied from 0.3 to 1.0 m, the impact angles are less than ±20°, it is proposed that the distance between two wind speed sensors is 0.8 m at least, and the interval between wind speed sensors and the steel pole is more than 1.0 m with the sensors located on the upstream side.展开更多
Wireless smart sensors(WSS)process field data and inform inspectors about the infrastructure health and safety.In bridge engineering,inspectors need reliable data about changes in displacements under loads to make cor...Wireless smart sensors(WSS)process field data and inform inspectors about the infrastructure health and safety.In bridge engineering,inspectors need reliable data about changes in displacements under loads to make correct decisions about repairs and replacements.Access to displacement information in the field and in real-time remains a challenge as inspectors do not see the data in real time.Displacement data from WSS in the field undergoes additional processing and is seen at a different location.If inspectors were able to see structural displacements in real-time at the locations of interest,they could conduct additional observations,creating a new,information-based,decision-making reality in the field.This paper develops a new,human-centered interface that provides inspectors with real-time access to actionable structural data during inspection and monitoring enhanced by augmented reality(AR).It summarizes and evaluates the development and validation of the new human-infrastructure interface in laboratory experiments.The experiments demonstrate that the interface that processes all calculations in the AR device accurately estimates dynamic displacements in comparison with the laser.Using this new AR interface tool,inspectors can observe and compare displacement data,share it across space and time,visualize displacements in time history,and understand structural deflection more accurately through a displacement time history visualization.展开更多
As the technological breakthrough is made in wireless charging, the wireless rechargeable sensor networks (WRSNs) are finally proposed. In order to reduce the charging completion time, most existing works use the “mo...As the technological breakthrough is made in wireless charging, the wireless rechargeable sensor networks (WRSNs) are finally proposed. In order to reduce the charging completion time, most existing works use the “mobilethen- charge” model—the Wireless charging vehicles (WCV) moves to the charging spot first and then charges nodes nearby. These works often aim to reduce the node’s movement delay or charging delay. However, the charging opportunities during the movement are overlooked in this model because WCV can charge nodes when it goes from one spot to the next. In order to use the charging opportunities, a speed grading method is proposed under the circumstance of variable WCV speed, which transformed the problem of final charging delay into a traveling salesman problem with speed grading. The problem was further solved by linear programming method. The simulation experiments show that, compared with the existing charging methods, the proposed method has a significant improvement in charging delay.展开更多
In recent years,high-end equipment is widely used in industry and the accuracy requirements of the equipment have been risen year by year.During the machining process,the high-end equipment failure may have a great im...In recent years,high-end equipment is widely used in industry and the accuracy requirements of the equipment have been risen year by year.During the machining process,the high-end equipment failure may have a great impact on the product quality.It is necessary to monitor the status of equipment and to predict fault diagnosis.At present,most of the condition monitoring devices for mechanical equipment have problems of large size,low precision and low energy utilization.A wireless self-powered intelligent spindle vibration acceleration sensor system based on piezoelectric energy harvesting is proposed.Based on rotor sensing technology,a sensor is made to mount on the tool holder and build the related circuit.Firstly,the energy management module collects the mechanical energy in the environment and converts the piezoelectric vibration energy into electric energy to provide 3.3 Vfor the subsequent circuit.The lithium battery supplies the system with additional power and monitors’the power of the energy storage circuit in real-time.Secondly,a three-axis acceleration sensor is used to collect,analyze and filter a series of signal processing operations of the vibration signal in the environment.The signal is sent to the upper computer by wireless transmission.The host computer outputs the corresponding X,Y,and Z channel waveforms and data under the condition of the spindle speed of 50∼2500 r/min with real-time monitoring.The KEIL5 platform is used to develop the system software.The small-size piezoelectric vibration sensor with high-speed,high-energy utilization,high accuracy,and easy installation is used for spindle monitoring.The experiment results show that the sensor system is available and practical.展开更多
A novel speed sensor-less direct torque control induction motor drive system for the mining locomotive haulage is presented in the paper. Rotor speed identification is based on the model reference adaptive control the...A novel speed sensor-less direct torque control induction motor drive system for the mining locomotive haulage is presented in the paper. Rotor speed identification is based on the model reference adaptive control theory with neural network using back propagation algorithm. The system is implemented using a real-time TMS320F240 digital signal processor. The simulation study and experiment results indicate that the suggested system has good performance.展开更多
In most areas of China, affected by the environment of low temperature and high humidity, the wind speed sensor and wind direction sensor are frozen and cannot output data in autumn, winter or the alternation of winte...In most areas of China, affected by the environment of low temperature and high humidity, the wind speed sensor and wind direction sensor are frozen and cannot output data in autumn, winter or the alternation of winter and spring. In order to solve the freezing situation of the wind sensor, this paper designs a new type of antifreeze wind speed sensor. After meteorology performance testing and field observation tests, the correlation coefficient of the observation data is demonstrated, and the data curve is fitted. The result shows the sensor is stable, and has a good antifreeze effect, the data output is reliable.展开更多
文摘The component of light in the 3<sup>rd</sup> dimension decreases as light enters the 4<sup>th</sup> dimension created by a Black Hole. Hence particles moving in 3-D space will emit radiation due to the Cherenkov Effect. Gravity and acceleration are the same according to Einstein’s Equivalence Principle. Density also has the same effect as gravity because gravity attracts matter thereby increasing matter density. The laws of Physics and all the constants of nature such as the Speed of light, Planck’s constant, the Gravitational constant, and so on are a function of the dimension of the space they are in since the vacuum energy density of each higher dimension is greater. We analyze the graph of the accelerated expansion of the Universe to calculate the acceleration for small Redshift z and predict what will happen for larger z values.
基金the Hi-Tech Research and Development Pro-gram (863) of China (No. 2006AA04Z233)the National NaturalScience Foundation of China (No. 50575205)the Natural ScienceFoundation of Zhejiang Province (Nos. Y104243 and Y105686),China
文摘To satisfy the need of high speed NC (numerical control) machining, an acceleration and deceleration (acc/dec) control model is proposed, and the speed curve is also constructed by the cubic polynomial. The proposed control model provides continuity of acceleration, which avoids the intense vibration in high speed NC machining. Based on the discrete characteristic of the data sampling interpolation, the acc/dec control discrete mathematical model is also set up and the discrete expression of the theoretical deceleration length is obtained furthermore. Aiming at the question of hardly predetermining the deceleration point in acc/dec control before interpolation, the adaptive acc/dec control algorithm is deduced from the expressions of the theoretical deceleration length. The experimental result proves that the acc/dec control model has the characteristic of easy implementation, stable movement and low impact. The model has been applied in multi-axes high speed micro fabrication machining successfully.
基金Supported by the High Technology Research and Development Programme of China ( No. 2003AA602230) and the National Natural Science Foundation of China(No. 50308007).
基金supported by the National Natural Science Foundation of China(Nos. 51775483 and 51275447)the Research Innovation Program for College Graduates of Jiangsu Province(No.SJLX_0589)
文摘A linear acceleration sensor,which is inspired by the human balance organ,is designed and prepared. It uses a liquid mass-block and a symmetrical-electrodes metal-core polyvinylidene fluoride fiber(SMPF)as the sensor element. The output signal of the sensor has an exponential relationship with the excitation amplitude of the impacting vibration. It is capable of detecting the amplitude and the correct frequency for sinusoidal excitations using an exponential correlation. The experiments indicate that both the output signal of the sensor and the resonance frequency increase substantially with increasing diameter of the metal core. The first-order resonance frequencies of the sensors with 40,60,and 80 μm diameter metal wires are below 10 Hz,which is near the range of human body motion frequencies.
文摘Numerous wireless networks have emerged that can be used for short communication ranges where the infrastructure-based networks may fail because of their installation and cost.One of them is a sensor network with embedded sensors working as the primary nodes,termed Wireless Sensor Networks(WSNs),in which numerous sensors are connected to at least one Base Station(BS).These sensors gather information from the environment and transmit it to a BS or gathering location.WSNs have several challenges,including throughput,energy usage,and network lifetime concerns.Different strategies have been applied to get over these restrictions.Clustering may,therefore,be thought of as the best way to solve such issues.Consequently,it is crucial to analyze effective Cluster Head(CH)selection to maximize efficiency throughput,extend the network lifetime,and minimize energy consumption.This paper proposed an Accelerated Particle Swarm Optimization(APSO)algorithm based on the Low Energy Adaptive Clustering Hierarchy(LEACH),Neighboring Based Energy Efficient Routing(NBEER),Cooperative Energy Efficient Routing(CEER),and Cooperative Relay Neighboring Based Energy Efficient Routing(CR-NBEER)techniques.With the help of APSO in the implementation of the WSN,the main methodology of this article has taken place.The simulation findings in this study demonstrated that the suggested approach uses less energy,with respective energy consumption ranges of 0.1441 to 0.013 for 5 CH,1.003 to 0.0521 for 10 CH,and 0.1734 to 0.0911 for 15 CH.The sending packets ratio was also raised for all three CH selection scenarios,increasing from 659 to 1730.The number of dead nodes likewise dropped for the given combination,falling between 71 and 66.The network lifetime was deemed to have risen based on the results found.A hybrid with a few valuable parameters can further improve the suggested APSO-based protocol.Similar to underwater,WSN can make use of the proposed protocol.The overall results have been evaluated and compared with the existing approaches of sensor networks.
基金funded by the National Natural Science Foundation of China(Grant No.11502118).
文摘Intentional electromagnetic interference is a serious threat to the safety of electronic devices. Multiple electromagnetic pulses will be coupled and transmitted to electronic devices through the cables.Accumulative effects are generated, which make it easier for damage to occur in the electronic devices. In this article, the working principle of micro-silicon acceleration sensors is introduced. The accumulative effects of multiple pulses on acceleration sensors is studied by a large number of injection experiments.The accumulation trends of multiple pulses with different pulse numbers and intervals are analyzed. The damaged structures inside abnormal sensor amplifiers were observed via optical microscopy and scanning electron microscopy. The experimental results show that the accumulative effect is strengthened with increased pulse number or decreased pulse interval, and the threshold voltage for multiple pulses on the acceleration sensor decreases. The threshold voltage for a single pulse is 321.57 V. When the pulse interval is 1 μs and the pulse number is 5, the threshold voltage for multiple pulses is 163.42 V,which is reduced by 49.12% compared with a single pulse. These results provide a reference for the damage design of electromagnetic pulse weapons.
基金supported in part by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(2020M3H4A3106326)supported in part by the NRF grant funded by the Korea government(Ministry of Science and ICT)(NRF-2020R1A2C1005449)。
文摘This paper suggests a novel model-based nonlinear DC motor speed regulator without the use of a current sensor.The current dynamics,machine parameters and mismatched load variations are considered.The proposed controller is designed to include an active damping term that regulates the motor speed in accordance with the first-order low-pass filter dynamics through the pole-zero cancellation.Meanwhile,the angular acceleration and its reference are obtained from simple first-order estimators using only the speed information.The effectiveness is experimentally verified using hardware comprising the QUBEServo2,myRIO-1900,and LabVIEW.
文摘We present a Machian model of Quantum Cosmology with full dark matter and light speed expansion and rotation. During galaxy formation and evolution, fraction of dark matter transforms to visible matter with a relation of the form, m_vis = constant * (m_dark)<sup>2/3</sup>. Using this relation and replacing MOND’s “critical acceleration” with “current cosmic maximum angular acceleration”, galactic flat rotation speed range of (50 to 500) km/sec can be fitted well. Estimated flat rotation speeds of DD168, Milky Way and UGC12591 are 49.96 km/sec, 199.66 km/sec and 521.75 km/sec respectively. Based on these striking coincidences, it is possible to say that, MOND’s approach is implicitly connected with cosmological estimation of 95% invisible matter. With reference to SPARC data for flat rotation speeds and current cosmic maximum angular acceleration, galactic total mass can be estimated. Considering galactic total mass, galactic visible mass and dark mass can be estimated. Proceeding further, galactic working radii, angular velocity and visible matter density can be estimated. Estimated Milky Way’s effective radius is 293 kpc. Even though, this model is free from “big bang”, “inflation”, “dark energy”, “flatness” and “red shift” issues, at 2.722 K, estimated present Hubble parameter is 66.24 km/sec/Mpc, cosmic radius is 146.3 times of the Hubble radius, angular velocity is 146.3 times lower than the Hubble parameter and cosmic age is 146.3 times of the Hubble age. With future observations and advanced telescopes, it may be possible to see far distant galaxies and very old stars far beyond the current observable cosmic radius.
文摘Since high-speed railway bridges are subjected to cyclic loading by the continuous wheel loads traveling at high speed and regular spacing, their dynamic behavior is of extreme importance and has significant influence on the riding safety of the trains. To secure the riding safety of the trains, advanced railway countries have limited the vertical acceleration of the bridge slab below critical values at specific frequency domains. Since these limitations of the vertical acceleration constitute the most important factors in securing the dynamic safety of the bridges, these countries have opted for a conservative approach. However, the Korean specifications limit only the size of the peak acceleration without considering the frequency domain, which impede significantly rational evaluation of the high-speed railway bridges in Korea. In addition, the evaluation of the acceleration without consideration of the frequency domain is the cause of disagreement between the dynamic analysis and measurement results. This study conducts field monitoring and dynamic analysis on high-speed railway bridges to gather the acceleration signals and compare them. Significant difference in the size of the vertical acceleration was observed between the measured and dynamic analysis accelerations when discarding the frequency domain as done in the current specifications. The comparison of the accelerations considering only low frequencies below 30 Hz showed that the dynamic analysis reflected accurately the measured vertical acceleration.
文摘Gearbox, as the crucial transmission equipment of high-speed train drive system, bears mainly the impact of wheel-rail excitation during its application, resulting in fatigue failure of the housing structure. In order to analyze the vibration characteristics of the high-speed train gearbox housing, a test had been performed under operating condition on Wuhan-Guangzhou High-Speed Railway, where a host of vibration characteristics of different parts of housing had been obtained, and vibration signals had also been comparatively analyzed using acceleration amplitude spectrum and equivalent acceleration amplitude method. The result showed that the vibration level of the measuring point A on the joint part of the gearbox housing and axle bearing block was higher than that of the measuring point B on the upper part of the gearbox housing, both horizontally and vertically. And there existed attenuation during the transmission process of vibration from point A to Point B. Further, when a train was moving at a high speed, the gearbox vibration at the head carriage was better than that at the tail carriage. In addition, when a train slowed down from 300 km/h to 200 km/h, the horizontal equivalent acceleration amplitude dropped by 58% while the vertical one declined by 62%. Equivalent acceleration amplitude method was used to identify the vibration relations among different parts of housing, and the validity and applicability of this method were verified by data analysis. The study provided reference to ensure the operating safety of high-speed train drive system and design of new housing structure.
基金Funded by the National Natural Science Foundation of China (No. 60376032 and No. 90406024) and the Key Teacher Foundation of Chongqing University.
文摘Based on piezoresistive effect, the acceleration sensitivity of multi-walled canbon nanotube (MWNT) films was investigated. A three-point bending technique was presented to measure the piezoresistivity, which used a bending stress applied to the samples while making MWNT films wheeling with a rotational machine. The experimental results showed that the fractional increase in resistance increases linearly versus the increase of centripetal acceleration, and there is a linear relationship between the acceleration and the strain. These shed light on using carbon nanotube films as acceleration sensors for many potential applications.
文摘The high speed maglev is mainly characterized by propulsion using linear synchronous motor (LSM) and vehicle levitation from the guideway surface. In LSM propulsion control, the position detection sensor is used to detect running vehicle position for synchronized current generation. To maintain the stable levitating condition during vehicle running, the irregularity of guideway surface should be monitored by sensors measuring the displacement and acceleration between vehicle and guideway. In this study, the application methods of these sensors in the high speed maglev are investigated and through the experiments by using the small-scale test bed, the validity of examined methods is confirmed.
文摘According to the verification regulation of the Wind Direction and Wind Speed Sensor of Automatic Meteorological Station[JJG(meteorological)004-2011],relying on the wind tunnel laboratory of Hebei meteorological measurement station,EL15-1 A type of wind speed sensor in the automatic weather station was verified.The experimental data of sensor verification in different laboratory environments were obtained through data comparison.Using standard wind speed measurement formula,the influence of laboratory temperature,humidity and air pressure on verification results was analyzed quantitatively.The results showed that laboratory temperature had the greatest influence on the verification results of this type of sensor,while the humidity and air pressure had less influence.Therefore,it should be noted that the temperature change in the laboratory should not be too large in the process of verification,so as to improve the accuracy of the verification results.
基金Projects(U1334205,51205418)supported by the National Natural Science Foundation of ChinaProject(2014T002-A)supported by the Science and Technology Research Program of China Railway CorporationProject(132014)supported by the Fok Ying Tong Education Foundation of China
文摘In order to consider the influence of steel pole on the measurement of wind speed sensors and determinate the installation position of wind speed sensors, the flow field around wind speed sensors was investigated. Based on the three-dimensional steady Reynolds-averaged Navier-Stokes equations and k-ε double equations turbulent model, the field flow around the wind speed sensor and the steel pole along a high-speed railway was simulated on an unstructured grid. The grid-independent validation was conducted and the accuracy of the present numerical simulation method was validated by experiments and simulations carried out by previous researchers. Results show that the steel pole has a significant influence on the measurement results of wind speed sensors. As the distance between two wind speed sensors is varied from 0.3 to 1.0 m, the impact angles are less than ±20°, it is proposed that the distance between two wind speed sensors is 0.8 m at least, and the interval between wind speed sensors and the steel pole is more than 1.0 m with the sensors located on the upstream side.
基金Air Force Research Laboratory(AFRL,Grant No.FA9453-18-2-0022)the New Mexico Consortium(NMC,Grant No.2RNA6)the US Department of Transportation Center:Transportation Consortium of South-Central States(TRANSET)Project 19STUNM02(TRANSET,Grant No.8-18-060ST)。
文摘Wireless smart sensors(WSS)process field data and inform inspectors about the infrastructure health and safety.In bridge engineering,inspectors need reliable data about changes in displacements under loads to make correct decisions about repairs and replacements.Access to displacement information in the field and in real-time remains a challenge as inspectors do not see the data in real time.Displacement data from WSS in the field undergoes additional processing and is seen at a different location.If inspectors were able to see structural displacements in real-time at the locations of interest,they could conduct additional observations,creating a new,information-based,decision-making reality in the field.This paper develops a new,human-centered interface that provides inspectors with real-time access to actionable structural data during inspection and monitoring enhanced by augmented reality(AR).It summarizes and evaluates the development and validation of the new human-infrastructure interface in laboratory experiments.The experiments demonstrate that the interface that processes all calculations in the AR device accurately estimates dynamic displacements in comparison with the laser.Using this new AR interface tool,inspectors can observe and compare displacement data,share it across space and time,visualize displacements in time history,and understand structural deflection more accurately through a displacement time history visualization.
文摘As the technological breakthrough is made in wireless charging, the wireless rechargeable sensor networks (WRSNs) are finally proposed. In order to reduce the charging completion time, most existing works use the “mobilethen- charge” model—the Wireless charging vehicles (WCV) moves to the charging spot first and then charges nodes nearby. These works often aim to reduce the node’s movement delay or charging delay. However, the charging opportunities during the movement are overlooked in this model because WCV can charge nodes when it goes from one spot to the next. In order to use the charging opportunities, a speed grading method is proposed under the circumstance of variable WCV speed, which transformed the problem of final charging delay into a traveling salesman problem with speed grading. The problem was further solved by linear programming method. The simulation experiments show that, compared with the existing charging methods, the proposed method has a significant improvement in charging delay.
基金supported by the National Natural Science Foundation of China(51975058).
文摘In recent years,high-end equipment is widely used in industry and the accuracy requirements of the equipment have been risen year by year.During the machining process,the high-end equipment failure may have a great impact on the product quality.It is necessary to monitor the status of equipment and to predict fault diagnosis.At present,most of the condition monitoring devices for mechanical equipment have problems of large size,low precision and low energy utilization.A wireless self-powered intelligent spindle vibration acceleration sensor system based on piezoelectric energy harvesting is proposed.Based on rotor sensing technology,a sensor is made to mount on the tool holder and build the related circuit.Firstly,the energy management module collects the mechanical energy in the environment and converts the piezoelectric vibration energy into electric energy to provide 3.3 Vfor the subsequent circuit.The lithium battery supplies the system with additional power and monitors’the power of the energy storage circuit in real-time.Secondly,a three-axis acceleration sensor is used to collect,analyze and filter a series of signal processing operations of the vibration signal in the environment.The signal is sent to the upper computer by wireless transmission.The host computer outputs the corresponding X,Y,and Z channel waveforms and data under the condition of the spindle speed of 50∼2500 r/min with real-time monitoring.The KEIL5 platform is used to develop the system software.The small-size piezoelectric vibration sensor with high-speed,high-energy utilization,high accuracy,and easy installation is used for spindle monitoring.The experiment results show that the sensor system is available and practical.
文摘A novel speed sensor-less direct torque control induction motor drive system for the mining locomotive haulage is presented in the paper. Rotor speed identification is based on the model reference adaptive control theory with neural network using back propagation algorithm. The system is implemented using a real-time TMS320F240 digital signal processor. The simulation study and experiment results indicate that the suggested system has good performance.
文摘In most areas of China, affected by the environment of low temperature and high humidity, the wind speed sensor and wind direction sensor are frozen and cannot output data in autumn, winter or the alternation of winter and spring. In order to solve the freezing situation of the wind sensor, this paper designs a new type of antifreeze wind speed sensor. After meteorology performance testing and field observation tests, the correlation coefficient of the observation data is demonstrated, and the data curve is fitted. The result shows the sensor is stable, and has a good antifreeze effect, the data output is reliable.