The accuracy of spot centroid positioning has a significant impact on the tracking accuracy of the system and the stability of the laser link construction.In satellite laser communication systems,the use of short-wave...The accuracy of spot centroid positioning has a significant impact on the tracking accuracy of the system and the stability of the laser link construction.In satellite laser communication systems,the use of short-wave infrared wavelengths as beacon light can reduce atmospheric absorption and signal attenuation.However,there are strong non-uniformity and blind pixels in the short-wave infrared image,which makes the image distorted and leads to the decrease of spot centroid positioning accuracy.Therefore,the high-precision localization of the spot centroid of the short-wave infrared images is of great research significance.A high-precision spot centroid positioning model for short-wave infrared is proposed to correct for non-uniformity and blind pixels in short-wave infrared images and quantify the localization errors caused by the two,further model-based localization error simulations are performed,and a novel spot centroid positioning payload for satellite laser communications has been designed using the latest 640×512 planar array InGaAs shortwave infrared detector.The experimental results show that the non-uniformity of the corrected image is reduced from 7%to 0.6%,the blind pixels rejection rate reaches 100%,the frame rate can be up to 2000 Hz,and the spot centroid localization accuracy is as high as 0.1 pixel point,which realizes high-precision spot centroid localization of high-frame-frequency short-wave infrared images.展开更多
Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail ...Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.展开更多
Accurate monitoring of track irregularities is very helpful to improving the vehicle operation quality and to formulating appropriate track maintenance strategies.Existing methods have the problem that they rely on co...Accurate monitoring of track irregularities is very helpful to improving the vehicle operation quality and to formulating appropriate track maintenance strategies.Existing methods have the problem that they rely on complex signal processing algorithms and lack multi-source data analysis.Driven by multi-source measurement data,including the axle box,the bogie frame and the carbody accelerations,this paper proposes a track irregularities monitoring network(TIMNet)based on deep learning methods.TIMNet uses the feature extraction capability of convolutional neural networks and the sequence map-ping capability of the long short-term memory model to explore the mapping relationship between vehicle accelerations and track irregularities.The particle swarm optimization algorithm is used to optimize the network parameters,so that both the vertical and lateral track irregularities can be accurately identified in the time and spatial domains.The effectiveness and superiority of the proposed TIMNet is analyzed under different simulation conditions using a vehicle dynamics model.Field tests are conducted to prove the availability of the proposed TIMNet in quantitatively monitoring vertical and lateral track irregularities.Furthermore,comparative tests show that the TIMNet has a better fitting degree and timeliness in monitoring track irregularities(vertical R2 of 0.91,lateral R2 of 0.84 and time cost of 10 ms),compared to other classical regression.The test also proves that the TIMNet has a better anti-interference ability than other regression models.展开更多
Following a brief history and progress of ionospheric research, this paper presents a brief review of the recent developments in the understanding of two major phenomena in low and mid latitude ionosphere—the equator...Following a brief history and progress of ionospheric research, this paper presents a brief review of the recent developments in the understanding of two major phenomena in low and mid latitude ionosphere—the equatorial ionization anomaly(EIA) and involved equatorial plasma fountain(EPF) and ionospheric irregularities. Unlike the easy-to-understand misinterpretations, the EPF involves field perpendicular E×B plasma drift and field-aligned plasma diffusion acting together and plasma flowing in the direction of the resultant at all points along the field lines at all altitudes. The EIA is formed mainly from the removal of plasma from around the equator by the upward E×B drift creating the trough and consequently the crests with small accumulation of plasma at the crests when the crests are within ~±20° magnetic latitudes and no accumulation when they are beyond ~±25° magnetic latitudes. The strong EIA under magnetically active conditions arises from the simultaneous impulsive action of eastward prompt penetration electric field and equatorward neutral wind. Intense ionospheric irregularities develop in the post-sunset bottom-side equatorial ionosphere when it rises to high altitudes, and evolve nonlinearly into the topside. Pre-reversal enhancement(PRE) of the vertical upward E×B drift and its fluctuations amplified during PRE provide the driving force and seed, with neutral wind and gravity waves being the primary sources. At low solar activity especially in summer when fast varying PRE is absent, the slow varying gravity waves including large scale waves(LSW)seem to act as both driver and seed for weak irregularities. At mid latitudes, the irregularities are weak and associated with medium scale traveling ionospheric disturbances(MSTIDs). A low latitude minimum in the occurrence of the irregularities at March equinox predicted by theoretical models is identified. The minimum occurs on the poleward side of the EIA crest and shifts equatorward from ~25° magnetic latitudes at high solar activity to below 17° at low solar activity.展开更多
In this article, unique spectral features of short-wave infrared band of 1 μm–3 μm, and various applications related to the photodetectors and focal plane arrays in this band, are introduced briefly. In addition, t...In this article, unique spectral features of short-wave infrared band of 1 μm–3 μm, and various applications related to the photodetectors and focal plane arrays in this band, are introduced briefly. In addition, the different material systems for the devices in this band are outlined. Based on the background, the development of lattice-matched and wavelengthextended InGaAs photodetectors and focal plane arrays, including our continuous efforts in this field, are reviewed. These devices are concentrated on the applications in spectral sensing and imaging, exclusive of optical fiber communication.展开更多
Dynamic responses of track structure and wave propagation in nearby ground vibration become significant when train operates on high speeds. A train-track-ground dynamic interaction analysis model based on the 2.5D fin...Dynamic responses of track structure and wave propagation in nearby ground vibration become significant when train operates on high speeds. A train-track-ground dynamic interaction analysis model based on the 2.5D finite element method is developed for the prediction of ground vibrations due to vertical track irregularities. The one-quarter car mode,1 is used to represent the train as lumped masses connected by springs. The embankment and the underlying ground are modeled by the 2.5D finite element approach to improve the computation efficiency. The Fourier transform is applied in the direction of train＇s movement to express the wave motion with a wave-number. The one-quarter car model is coupled into the global stiffness matrix describing the track-ground dynamic system with the displacement compatibility condition at the wheel-rail interface, including the irregularities on the track surface. Dynamic responses of the track and ground due to train＇s moving loads are obtained in the wave-number domain by solving the governing equation, using a conventional finite element procedure. The amplitude and wavelength are identified as two major parameters describing track irregularities. The irregularity amplitude has a direct impact on the vertical response for low-speed trains, both for short wavelength and long wavelength irregularities. Track irregularity with shorter wavelength can generate stronger track vibration both for low-speed and high-speed cases. For low-speed case, vibrations induced by track irregularities dominate far field responses. For high-speed case, the wavelength of track irregularities has very little effect on ground vibration at distances far from track center, and train＇s wheel axle weights becomes dominant.展开更多
The Qulong deposit in Tibet is one of the largest porphyry copper-molybdenum deposits in China.We used short-wave infrared(SWIR)spectroscopy to examine the spectral characteristics of the extensively developed chlorit...The Qulong deposit in Tibet is one of the largest porphyry copper-molybdenum deposits in China.We used short-wave infrared(SWIR)spectroscopy to examine the spectral characteristics of the extensively developed chlorite in this deposit.X-ray diffraction and electron microprobe analyses were used for phase identification and to obtain the chemical composition,ion substitution relationships,and formation environment of the chlorite.SWIR spectral parameters were applied to detect the hydrothermal centers.The results indicate that the wavelength of the absorption feature for Qulong chlorite Fe-OH(Pos2250)range from 2240 to 2268.4 nm;the chlorite substitution relationships are dominated by Mg-Fe substitution at the octahedral sites together with Al;-Si substitution at the tetrahedral sites;the chlorite formation temperatures range within the medium-low temperature hydrothermal alteration range from 164 to 281°C,with an average value of 264℃;the wavelength of the chlorite peak position for Fe-OH(2250 nm)absorption and its chemical composition are positively correlated with Al^(Ⅵ),Fe+Al^(Ⅵ),Fe/(Fe+Mg),Fe,and Fe+Al^(Ⅳ)but negatively correlated with Mg and Mg/(Fe+Mg);and the wavelength associated with the chlorite Fe-OH(2250 nm)absorption feature is positively correlated with the temperature at which the chlorite formed.These correlations indicate that more Fe and Al^(Ⅵ)ions and fewer Mg ions at the octahedral sites of chlorite lead to a longer the wavelength of the chlorite Fe-OH(2250 nm)absorption feature and a higher chlorite formation temperature.The wavelength of the Qulong chlorite Fe-OH(2250 nm)absorption feature(>2252 nm)can thus serve as an exploration indicator to guide the detection of hydrothermal centers in porphyry copper deposits.The results of the study indicate that the mineralogical and SWIR spectral characteristics of chlorite are significant indicators for locating hydrothermal centers within porphyry deposits.展开更多
The characteristics of high-frequency(HF)electromagnetic(EM)wave propagation can be affected when EM waves propagate in the ionosphere.When ionospheric irregularities appear in the ionosphere,they can have a serious i...The characteristics of high-frequency(HF)electromagnetic(EM)wave propagation can be affected when EM waves propagate in the ionosphere.When ionospheric irregularities appear in the ionosphere,they can have a serious impact on the propagation of HF EM waves.In this study,the propagation of HF EM waves in ionospheric irregularities was investigated by numerical simulation.First,a twodimensional model of plasma bubbles was used to produce ionospheric irregularities in the ionosphere.A ray-tracing method was then utilized to simulate the propagation of HF radio waves in these ionospheric irregularities.Results showed that the propagation of HF radio waves in the ionosphere was more complex in ionospheric irregularities than without ionospheric irregularities.In addition,corresponding ionograms were synthesized by radio rays propagated in the ionosphere with these irregularities.The synthesized ionograms were then compared with the experimental ionograms recorded by an ionosonde.Results showed that spread F could be simulated on the ionograms when ionospheric irregularities occurred in the ionosphere.This result was consistent with the ionosonde observations.展开更多
This paper briefly reviews ionospheric irregularities that occur in the E and F regions at mid-latitudes. Sporadic E(ES) is a common ionospheric irregularity phenomenon that is first noticed in the E layer. ES mainly ...This paper briefly reviews ionospheric irregularities that occur in the E and F regions at mid-latitudes. Sporadic E(ES) is a common ionospheric irregularity phenomenon that is first noticed in the E layer. ES mainly appears during daytime in summer hemispheres, and is formed primarily from neutral wind shear in the mesosphere and lower thermosphere(MLT) region. Field-aligned irregularity(FAI) in the E region is also observed by Very High Frequency(VHF) radar in mid-latitude regions. FAI frequently occurs after sunset in summer hemispheres, and spectrum features of E region FAI echoes suggest that type-2 irregularity is dominant in the nighttime ionosphere. A close relationship between ES and E region FAI implies that ES may be a possible source of E region FAI in the nighttime ionosphere. Strong neutral wind shear, steep ES plasma density gradient, and a polarized electric field are the significant factors affecting the formation of E region FAI. At mid-latitudes, joint observational experiments including ionosonde, VHF radar, Global Positioning System(GPS) stations, and all-sky optical images have revealed strong connections across different scales of ionospheric irregularities in the nighttime F region, such as spread F(SF), medium-scale traveling ionospheric disturbances(MSTID), and F region FAI.Observations suggest that different scales of ionospheric irregularities are generally attributed to the Perkins instability and subsequently excited gradient drift instability. Nighttime MSTID can further evolve into small-scale structures through a nonlinear cascade process when a steep plasma density gradient exists at the bottom of the F region. In addition, the effect of ionospheric electrodynamic coupling processes, including ionospheric E-F coupling and inter-hemispheric coupling on the generation of ionospheric irregularities, becomes more prominent due to the significant dip angle and equipotentiality of magnetic field lines in the mid-latitude ionosphere. Polarized electric fields can map to different ionospheric regions and excite plasma instabilities which form ionospheric irregularities. Nevertheless,the mapping efficiency of a polarized electric field depends on the ionospheric background and spatial scale of the field.展开更多
Fault detection and isolation of high-speed train suspension systems is of critical importance to guarantee train running safety. Firstly, the existing methods concerning fault detection or isolation of train suspensi...Fault detection and isolation of high-speed train suspension systems is of critical importance to guarantee train running safety. Firstly, the existing methods concerning fault detection or isolation of train suspension systems are briefly reviewed and divided into two categories, i.e., model-based and data-driven approaches. The advantages and disadvantages of these two categories of approaches are briefly summarized. Secondly, a 1D convolution network-based fault diagnostic method for highspeed train suspension systems is designed. To improve the robustness of the method, a Gaussian white noise strategy(GWN-strategy) for immunity to track irregularities and an edge sample training strategy(EST-strategy) for immunity to wheel wear are proposed. The whole network is called GWN-EST-1 DCNN method. Thirdly, to show the performance of this method, a multibody dynamics simulation model of a high-speed train is built to generate the lateral acceleration of a bogie frame corresponding to different track irregularities, wheel profiles, and secondary suspension faults. The simulated signals are then inputted into the diagnostic network, and the results show the correctness and superiority of the GWN-EST-1DCNN method. Finally,the 1DCNN method is further validated using tracking data of a CRH3 train running on a high-speed railway line.展开更多
Recently, kilometer-scale Martian ionospheric irregularities have been measured by the Mars Atmosphere and Volatile EvolutioN(MAVEN) mission(Fowler et al., 2020). In this study, we carried out a simulation of these ir...Recently, kilometer-scale Martian ionospheric irregularities have been measured by the Mars Atmosphere and Volatile EvolutioN(MAVEN) mission(Fowler et al., 2020). In this study, we carried out a simulation of these irregularities, assuming a uniform Martian zonal neutral wind and a cosinusoidal perturbation of the plasma density as the seeding source. Results show that a vertical electric field shear could be induced by such a plasma density perturbation. We find that the vertical electric field shear causes a velocity shear of the plasma between the topside and bottomside ionosphere, which in turn is able to produce kilometer-scale ionospheric irregularities — irregularities of a smaller scale than were seen in previous simulations(Jiang CH et al., 2021). These kilometer-scale variations with altitude, in plasma density and magnetic field profiles, are comparable to the MAVEN observations.展开更多
The complete discrimination system for polynomial method is applied to the long-short-wave interaction system to obtain the classifications of single traveling wave solutions. Compared with the solutions given by the ...The complete discrimination system for polynomial method is applied to the long-short-wave interaction system to obtain the classifications of single traveling wave solutions. Compared with the solutions given by the （G~/G）-expansion method, we gain some new solutions.展开更多
Fructus cnidii （Chinese name shechuangzi） is the fruit produced by Cnidium monnieri （L.） Cusson （Umbelliferae）. It is a perennial herb that is used to treat skin-related diseases and gynecopathyell. Recent pharm...Fructus cnidii （Chinese name shechuangzi） is the fruit produced by Cnidium monnieri （L.） Cusson （Umbelliferae）. It is a perennial herb that is used to treat skin-related diseases and gynecopathyell. Recent pharmacological studies have revealed crude extracts or components isolated from fructus cnidii possess antiallergic, antipruritic, antidermatophytic, antibacterial, antifungal, and antiosteoporotic activities. Osthole and imperatorin are the major compounds present in shechuangzi. They are often used as standards for the evaluation of the quality of shechuangzi products.展开更多
Pantograph-catenary contact force provides the main basis for evaluation of current quality collection; however,the pantograph-catenary contact force is largely affected by the catenary irregularities.To analyze the c...Pantograph-catenary contact force provides the main basis for evaluation of current quality collection; however,the pantograph-catenary contact force is largely affected by the catenary irregularities.To analyze the correlated relationship between catenary irregularities and pantograph-catenary contact force,a method based on nonlinear auto-regressive with exogenous input(NARX) neural networks was developed.First,to collect the test data of catenary irregularities and contact force,the pantograph/catenary dynamics model was established and dynamic simulation was conducted using MATLAB/Simulink.Second,catenary irregularities were used as the input to NARX neural network and the contact force was determined as output of the NARX neural network,in which the neural network was trained by an improved training mechanism based on the regularization algorithm.The simulation results show that the testing error and correlation coefficient are 0.1100 and 0.8029,respectively,and the prediction accuracy is satisfactory.And the comparisons with other algorithms indicate the validity and superiority of the proposed approach.展开更多
We estimate the zonal drift velocity of small-scale ionospheric irregularities at low latitude by leveraging the spaced-receivers technique applied to two GNSS receivers for scintillation monitoring installed along th...We estimate the zonal drift velocity of small-scale ionospheric irregularities at low latitude by leveraging the spaced-receivers technique applied to two GNSS receivers for scintillation monitoring installed along the magnetic parallel passing in Presidente Prudente(Brazil,magnetic latitude 12.8°S).The investigated ionospheric sector is ideal to study small-scale irregularities,being located close to the expected position of the southern crest of the equatorial ionospheric anomaly.The measurement campaign took place between September 2013 and February 2014,i.e.equinox and summer solstice seasons under solar maximum,during which the probability of formation of small-scale irregularities is expected to maximize.We found that the hourly average of the velocity increases up to 135 m/s right after the local sunset at ionospheric altitudes and then smoothly decreases in the next hours.Such measurements are in agreement with independent estimations of the velocity made by the Incoherent Scatter Radar located at the Jicamarca Radio Observatory(magnetic latitude 0.1°N),by the Boa Vista Ionosonde(magnetic latitude 12.0°N),and by applying a recently-developed empirical regional short-term forecasting model.Additionally,we investigated the relationship with the percentage occurrence of amplitude scintillation;we report that it is exponentially dependent on the zonal velocity of the irregularities that cause it.展开更多
We investigate numerically the dynamical reactions of a moving wheelset model to real measured track irregularities.The background is to examine whether the dynamics are suitable as the input to the inverse problem:de...We investigate numerically the dynamical reactions of a moving wheelset model to real measured track irregularities.The background is to examine whether the dynamics are suitable as the input to the inverse problem:determine the true track geometry from measured wheelset dynamical reactions.It is known that the method works well for the vertical position of the rails but the computed lateral position is often flawed.We find that the lateral motion of the wheelset often may differ from the track geometry.The cases are investigated closely but the reasons remain unknown.While the wheelset dynamics reflect the larger(>4-6 mm)aperiodic track disturbances and single large disturbances quite well,this does not seem to be the case for general smaller or periodic track irregularities or sections behind single large disturbances.The resulting dynamics of a wheelset to lateral track irregularities are in general not sufficiently accurate to be used as the basis for a description of the track irregularities.展开更多
Synchisite-(Ce) from the Kibina alkaline massive, Kola peninsula, Russia , has been studied using electron diffraction and lattice-images techniques. The synchisite-(Ce) with relatively ordered stacking shows a microt...Synchisite-(Ce) from the Kibina alkaline massive, Kola peninsula, Russia , has been studied using electron diffraction and lattice-images techniques. The synchisite-(Ce) with relatively ordered stacking shows a microtwin. The semirandom stacking is caused by the displacement of CO3 layers parallel to the basal planes. The irregular stacking crystals contain Ca layers adjacent to each other.The synchisite-(Ce) is considered as a polymatic mineral with short-range disorder.展开更多
A theoretical model which describes the small-scale irregularities excited by powerful high frequency （3–30 MHz） electromagnetic wave in ionosphere heating is investigated quantitatively in this paper. The model is...A theoretical model which describes the small-scale irregularities excited by powerful high frequency （3–30 MHz） electromagnetic wave in ionosphere heating is investigated quantitatively in this paper. The model is based on the transport equation in magnetic plasma and mode conversion from electromagnetic wave to electrostatic wave in ionospheric modification.Threshold electric field for exciting small-scale （meter scale） irregularities and spatial spectra of irregularities are analytically calculated by this model. The results indicate that background electron density and geomagnetic field play an important role for the threshold electric field and the spatial scale of the electron density irregularities. The results demonstrate that the electric field threshold increases with the decrease of the spatial scale of the irregularities. For exciting meter scale irregularities, the threshold electric field is about tens of mV m^（-1）. The theoretical results are consistent with those of the experiments.展开更多
In this paper, the Lie symmetry analysis and generalized symmetry method are performed for a short-wave model. The symmetries for this equation are given, and the phase portraits of the traveling wave systems are anal...In this paper, the Lie symmetry analysis and generalized symmetry method are performed for a short-wave model. The symmetries for this equation are given, and the phase portraits of the traveling wave systems are analyzed using the bifurcation theory of dynamical systems. The exact parametric representations of four types of traveling wave solutions are obtained.展开更多
基金Supported by the Short-wave Infrared Camera Systems(B025F40622024)。
文摘The accuracy of spot centroid positioning has a significant impact on the tracking accuracy of the system and the stability of the laser link construction.In satellite laser communication systems,the use of short-wave infrared wavelengths as beacon light can reduce atmospheric absorption and signal attenuation.However,there are strong non-uniformity and blind pixels in the short-wave infrared image,which makes the image distorted and leads to the decrease of spot centroid positioning accuracy.Therefore,the high-precision localization of the spot centroid of the short-wave infrared images is of great research significance.A high-precision spot centroid positioning model for short-wave infrared is proposed to correct for non-uniformity and blind pixels in short-wave infrared images and quantify the localization errors caused by the two,further model-based localization error simulations are performed,and a novel spot centroid positioning payload for satellite laser communications has been designed using the latest 640×512 planar array InGaAs shortwave infrared detector.The experimental results show that the non-uniformity of the corrected image is reduced from 7%to 0.6%,the blind pixels rejection rate reaches 100%,the frame rate can be up to 2000 Hz,and the spot centroid localization accuracy is as high as 0.1 pixel point,which realizes high-precision spot centroid localization of high-frame-frequency short-wave infrared images.
基金supported by Natural Science Foundation of China(52178441)the Scientific Research Projects of the China Academy of Railway Sciences Co.,Ltd.(Grant No.2022YJ043).
文摘Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.
基金supported by the Sichuan Science and Technology Program(Nos.2024JDRC0100 and 2023YFQ0091)the National Natural Science Foundation of China(Nos.U21A20167 and 52475138)the Scientific Research Foundation of the State Key Laboratory of Rail Transit Vehicle System(No.2024RVL-T08).
文摘Accurate monitoring of track irregularities is very helpful to improving the vehicle operation quality and to formulating appropriate track maintenance strategies.Existing methods have the problem that they rely on complex signal processing algorithms and lack multi-source data analysis.Driven by multi-source measurement data,including the axle box,the bogie frame and the carbody accelerations,this paper proposes a track irregularities monitoring network(TIMNet)based on deep learning methods.TIMNet uses the feature extraction capability of convolutional neural networks and the sequence map-ping capability of the long short-term memory model to explore the mapping relationship between vehicle accelerations and track irregularities.The particle swarm optimization algorithm is used to optimize the network parameters,so that both the vertical and lateral track irregularities can be accurately identified in the time and spatial domains.The effectiveness and superiority of the proposed TIMNet is analyzed under different simulation conditions using a vehicle dynamics model.Field tests are conducted to prove the availability of the proposed TIMNet in quantitatively monitoring vertical and lateral track irregularities.Furthermore,comparative tests show that the TIMNet has a better fitting degree and timeliness in monitoring track irregularities(vertical R2 of 0.91,lateral R2 of 0.84 and time cost of 10 ms),compared to other classical regression.The test also proves that the TIMNet has a better anti-interference ability than other regression models.
基金supported by National Natural Science Foundation of China (41621063, 41774161)the Open Research Project of Large Research Infrastructures of CAS-"Study on the interaction between low/mid-latitude atmosphere and ionosphere based on the Chinese Meridian Project"
文摘Following a brief history and progress of ionospheric research, this paper presents a brief review of the recent developments in the understanding of two major phenomena in low and mid latitude ionosphere—the equatorial ionization anomaly(EIA) and involved equatorial plasma fountain(EPF) and ionospheric irregularities. Unlike the easy-to-understand misinterpretations, the EPF involves field perpendicular E×B plasma drift and field-aligned plasma diffusion acting together and plasma flowing in the direction of the resultant at all points along the field lines at all altitudes. The EIA is formed mainly from the removal of plasma from around the equator by the upward E×B drift creating the trough and consequently the crests with small accumulation of plasma at the crests when the crests are within ~±20° magnetic latitudes and no accumulation when they are beyond ~±25° magnetic latitudes. The strong EIA under magnetically active conditions arises from the simultaneous impulsive action of eastward prompt penetration electric field and equatorward neutral wind. Intense ionospheric irregularities develop in the post-sunset bottom-side equatorial ionosphere when it rises to high altitudes, and evolve nonlinearly into the topside. Pre-reversal enhancement(PRE) of the vertical upward E×B drift and its fluctuations amplified during PRE provide the driving force and seed, with neutral wind and gravity waves being the primary sources. At low solar activity especially in summer when fast varying PRE is absent, the slow varying gravity waves including large scale waves(LSW)seem to act as both driver and seed for weak irregularities. At mid latitudes, the irregularities are weak and associated with medium scale traveling ionospheric disturbances(MSTIDs). A low latitude minimum in the occurrence of the irregularities at March equinox predicted by theoretical models is identified. The minimum occurs on the poleward side of the EIA crest and shifts equatorward from ~25° magnetic latitudes at high solar activity to below 17° at low solar activity.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0402400)the National Natural Science Foundation of China(Grant Nos.61675225,61605232,and 61775228)the Shanghai Rising-Star Program,China(Grant No.17QA1404900)
文摘In this article, unique spectral features of short-wave infrared band of 1 μm–3 μm, and various applications related to the photodetectors and focal plane arrays in this band, are introduced briefly. In addition, the different material systems for the devices in this band are outlined. Based on the background, the development of lattice-matched and wavelengthextended InGaAs photodetectors and focal plane arrays, including our continuous efforts in this field, are reviewed. These devices are concentrated on the applications in spectral sensing and imaging, exclusive of optical fiber communication.
基金Project supported by the National Key Technology R&D Program of the Ministry of Science and Technology of China(No.2009BAG12A01-B12-3)the National Natural Science Foundation of China(No.51178418)the Technology Promotion Program from the Ministry of Railway of China(No.2008G005-D)
文摘Dynamic responses of track structure and wave propagation in nearby ground vibration become significant when train operates on high speeds. A train-track-ground dynamic interaction analysis model based on the 2.5D finite element method is developed for the prediction of ground vibrations due to vertical track irregularities. The one-quarter car mode,1 is used to represent the train as lumped masses connected by springs. The embankment and the underlying ground are modeled by the 2.5D finite element approach to improve the computation efficiency. The Fourier transform is applied in the direction of train＇s movement to express the wave motion with a wave-number. The one-quarter car model is coupled into the global stiffness matrix describing the track-ground dynamic system with the displacement compatibility condition at the wheel-rail interface, including the irregularities on the track surface. Dynamic responses of the track and ground due to train＇s moving loads are obtained in the wave-number domain by solving the governing equation, using a conventional finite element procedure. The amplitude and wavelength are identified as two major parameters describing track irregularities. The irregularity amplitude has a direct impact on the vertical response for low-speed trains, both for short wavelength and long wavelength irregularities. Track irregularity with shorter wavelength can generate stronger track vibration both for low-speed and high-speed cases. For low-speed case, vibrations induced by track irregularities dominate far field responses. For high-speed case, the wavelength of track irregularities has very little effect on ground vibration at distances far from track center, and train＇s wheel axle weights becomes dominant.
基金funded by Science and Technology Project of Tibet Autonomous Region(Grant Nos.XZ201801-GB-01XZ202102YD0024C)+2 种基金The Second Round of Comprehensive Investigation and Research on the Qinghai-Tibet Plateau(Grant No.2019QZKK0806)National Natural Science Foundation of China(Grant No.42002097)Demonstration Research on Alteration Mapping using Short-wave Infrared and Thermal Infrared Hyperspectral Technologies(Grant No.KK2102)。
文摘The Qulong deposit in Tibet is one of the largest porphyry copper-molybdenum deposits in China.We used short-wave infrared(SWIR)spectroscopy to examine the spectral characteristics of the extensively developed chlorite in this deposit.X-ray diffraction and electron microprobe analyses were used for phase identification and to obtain the chemical composition,ion substitution relationships,and formation environment of the chlorite.SWIR spectral parameters were applied to detect the hydrothermal centers.The results indicate that the wavelength of the absorption feature for Qulong chlorite Fe-OH(Pos2250)range from 2240 to 2268.4 nm;the chlorite substitution relationships are dominated by Mg-Fe substitution at the octahedral sites together with Al;-Si substitution at the tetrahedral sites;the chlorite formation temperatures range within the medium-low temperature hydrothermal alteration range from 164 to 281°C,with an average value of 264℃;the wavelength of the chlorite peak position for Fe-OH(2250 nm)absorption and its chemical composition are positively correlated with Al^(Ⅵ),Fe+Al^(Ⅵ),Fe/(Fe+Mg),Fe,and Fe+Al^(Ⅳ)but negatively correlated with Mg and Mg/(Fe+Mg);and the wavelength associated with the chlorite Fe-OH(2250 nm)absorption feature is positively correlated with the temperature at which the chlorite formed.These correlations indicate that more Fe and Al^(Ⅵ)ions and fewer Mg ions at the octahedral sites of chlorite lead to a longer the wavelength of the chlorite Fe-OH(2250 nm)absorption feature and a higher chlorite formation temperature.The wavelength of the Qulong chlorite Fe-OH(2250 nm)absorption feature(>2252 nm)can thus serve as an exploration indicator to guide the detection of hydrothermal centers in porphyry copper deposits.The results of the study indicate that the mineralogical and SWIR spectral characteristics of chlorite are significant indicators for locating hydrothermal centers within porphyry deposits.
基金We acknowledge the Institute of Earthquake Forecasting for providing the ionosonde data.This work was supported by the National Natural Science Foundation of China(no.41604133).
文摘The characteristics of high-frequency(HF)electromagnetic(EM)wave propagation can be affected when EM waves propagate in the ionosphere.When ionospheric irregularities appear in the ionosphere,they can have a serious impact on the propagation of HF EM waves.In this study,the propagation of HF EM waves in ionospheric irregularities was investigated by numerical simulation.First,a twodimensional model of plasma bubbles was used to produce ionospheric irregularities in the ionosphere.A ray-tracing method was then utilized to simulate the propagation of HF radio waves in these ionospheric irregularities.Results showed that the propagation of HF radio waves in the ionosphere was more complex in ionospheric irregularities than without ionospheric irregularities.In addition,corresponding ionograms were synthesized by radio rays propagated in the ionosphere with these irregularities.The synthesized ionograms were then compared with the experimental ionograms recorded by an ionosonde.Results showed that spread F could be simulated on the ionograms when ionospheric irregularities occurred in the ionosphere.This result was consistent with the ionosonde observations.
基金supported by the National Natural Science Foundation of China (No. 41574146, 41774162, 42074187)the National Key R&D Program of China (No. 2018YFC1503506)+1 种基金the Excellent Youth Foundation of Hubei Provincial Natural Science Foundation (No. 2019CFA054)the Foundation of the National Key Laboratory of Electromagnetic Environment (No. 20200101)。
文摘This paper briefly reviews ionospheric irregularities that occur in the E and F regions at mid-latitudes. Sporadic E(ES) is a common ionospheric irregularity phenomenon that is first noticed in the E layer. ES mainly appears during daytime in summer hemispheres, and is formed primarily from neutral wind shear in the mesosphere and lower thermosphere(MLT) region. Field-aligned irregularity(FAI) in the E region is also observed by Very High Frequency(VHF) radar in mid-latitude regions. FAI frequently occurs after sunset in summer hemispheres, and spectrum features of E region FAI echoes suggest that type-2 irregularity is dominant in the nighttime ionosphere. A close relationship between ES and E region FAI implies that ES may be a possible source of E region FAI in the nighttime ionosphere. Strong neutral wind shear, steep ES plasma density gradient, and a polarized electric field are the significant factors affecting the formation of E region FAI. At mid-latitudes, joint observational experiments including ionosonde, VHF radar, Global Positioning System(GPS) stations, and all-sky optical images have revealed strong connections across different scales of ionospheric irregularities in the nighttime F region, such as spread F(SF), medium-scale traveling ionospheric disturbances(MSTID), and F region FAI.Observations suggest that different scales of ionospheric irregularities are generally attributed to the Perkins instability and subsequently excited gradient drift instability. Nighttime MSTID can further evolve into small-scale structures through a nonlinear cascade process when a steep plasma density gradient exists at the bottom of the F region. In addition, the effect of ionospheric electrodynamic coupling processes, including ionospheric E-F coupling and inter-hemispheric coupling on the generation of ionospheric irregularities, becomes more prominent due to the significant dip angle and equipotentiality of magnetic field lines in the mid-latitude ionosphere. Polarized electric fields can map to different ionospheric regions and excite plasma instabilities which form ionospheric irregularities. Nevertheless,the mapping efficiency of a polarized electric field depends on the ionospheric background and spatial scale of the field.
基金supported by the National Nature Science Foundation of China(No.71871188)the Fundamental Research Funds for the Central Universities(No.2682021CX051)supported by China Scholarship Council(No.201707000113)。
文摘Fault detection and isolation of high-speed train suspension systems is of critical importance to guarantee train running safety. Firstly, the existing methods concerning fault detection or isolation of train suspension systems are briefly reviewed and divided into two categories, i.e., model-based and data-driven approaches. The advantages and disadvantages of these two categories of approaches are briefly summarized. Secondly, a 1D convolution network-based fault diagnostic method for highspeed train suspension systems is designed. To improve the robustness of the method, a Gaussian white noise strategy(GWN-strategy) for immunity to track irregularities and an edge sample training strategy(EST-strategy) for immunity to wheel wear are proposed. The whole network is called GWN-EST-1 DCNN method. Thirdly, to show the performance of this method, a multibody dynamics simulation model of a high-speed train is built to generate the lateral acceleration of a bogie frame corresponding to different track irregularities, wheel profiles, and secondary suspension faults. The simulated signals are then inputted into the diagnostic network, and the results show the correctness and superiority of the GWN-EST-1DCNN method. Finally,the 1DCNN method is further validated using tracking data of a CRH3 train running on a high-speed railway line.
基金supported by the National Natural Science Foundation of China(NSFC No.42074184 and No.41727804)。
文摘Recently, kilometer-scale Martian ionospheric irregularities have been measured by the Mars Atmosphere and Volatile EvolutioN(MAVEN) mission(Fowler et al., 2020). In this study, we carried out a simulation of these irregularities, assuming a uniform Martian zonal neutral wind and a cosinusoidal perturbation of the plasma density as the seeding source. Results show that a vertical electric field shear could be induced by such a plasma density perturbation. We find that the vertical electric field shear causes a velocity shear of the plasma between the topside and bottomside ionosphere, which in turn is able to produce kilometer-scale ionospheric irregularities — irregularities of a smaller scale than were seen in previous simulations(Jiang CH et al., 2021). These kilometer-scale variations with altitude, in plasma density and magnetic field profiles, are comparable to the MAVEN observations.
基金Project supported by the Scientific Research Fund of Education Department of Heilongjiang Province of China (Grant No.12531475)
文摘The complete discrimination system for polynomial method is applied to the long-short-wave interaction system to obtain the classifications of single traveling wave solutions. Compared with the solutions given by the （G~/G）-expansion method, we gain some new solutions.
基金Supported by the Talented Young Pressional Foundation of Jilin Province(No 2005123)
文摘Fructus cnidii （Chinese name shechuangzi） is the fruit produced by Cnidium monnieri （L.） Cusson （Umbelliferae）. It is a perennial herb that is used to treat skin-related diseases and gynecopathyell. Recent pharmacological studies have revealed crude extracts or components isolated from fructus cnidii possess antiallergic, antipruritic, antidermatophytic, antibacterial, antifungal, and antiosteoporotic activities. Osthole and imperatorin are the major compounds present in shechuangzi. They are often used as standards for the evaluation of the quality of shechuangzi products.
基金Project(20120009110035)supported by Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject(2011BAG01B05)supported by National Key Technology Research and Development Program of ChinaProject(2011AA110501)supported by National High-tech Research and Development Program of China
文摘Pantograph-catenary contact force provides the main basis for evaluation of current quality collection; however,the pantograph-catenary contact force is largely affected by the catenary irregularities.To analyze the correlated relationship between catenary irregularities and pantograph-catenary contact force,a method based on nonlinear auto-regressive with exogenous input(NARX) neural networks was developed.First,to collect the test data of catenary irregularities and contact force,the pantograph/catenary dynamics model was established and dynamic simulation was conducted using MATLAB/Simulink.Second,catenary irregularities were used as the input to NARX neural network and the contact force was determined as output of the NARX neural network,in which the neural network was trained by an improved training mechanism based on the regularization algorithm.The simulation results show that the testing error and correlation coefficient are 0.1100 and 0.8029,respectively,and the prediction accuracy is satisfactory.And the comparisons with other algorithms indicate the validity and superiority of the proposed approach.
基金funded by FAPESP(Process 06/04008-2)funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sk?odowska-Curie Actions grant agreement No 722023。
文摘We estimate the zonal drift velocity of small-scale ionospheric irregularities at low latitude by leveraging the spaced-receivers technique applied to two GNSS receivers for scintillation monitoring installed along the magnetic parallel passing in Presidente Prudente(Brazil,magnetic latitude 12.8°S).The investigated ionospheric sector is ideal to study small-scale irregularities,being located close to the expected position of the southern crest of the equatorial ionospheric anomaly.The measurement campaign took place between September 2013 and February 2014,i.e.equinox and summer solstice seasons under solar maximum,during which the probability of formation of small-scale irregularities is expected to maximize.We found that the hourly average of the velocity increases up to 135 m/s right after the local sunset at ionospheric altitudes and then smoothly decreases in the next hours.Such measurements are in agreement with independent estimations of the velocity made by the Incoherent Scatter Radar located at the Jicamarca Radio Observatory(magnetic latitude 0.1°N),by the Boa Vista Ionosonde(magnetic latitude 12.0°N),and by applying a recently-developed empirical regional short-term forecasting model.Additionally,we investigated the relationship with the percentage occurrence of amplitude scintillation;we report that it is exponentially dependent on the zonal velocity of the irregularities that cause it.
文摘We investigate numerically the dynamical reactions of a moving wheelset model to real measured track irregularities.The background is to examine whether the dynamics are suitable as the input to the inverse problem:determine the true track geometry from measured wheelset dynamical reactions.It is known that the method works well for the vertical position of the rails but the computed lateral position is often flawed.We find that the lateral motion of the wheelset often may differ from the track geometry.The cases are investigated closely but the reasons remain unknown.While the wheelset dynamics reflect the larger(>4-6 mm)aperiodic track disturbances and single large disturbances quite well,this does not seem to be the case for general smaller or periodic track irregularities or sections behind single large disturbances.The resulting dynamics of a wheelset to lateral track irregularities are in general not sufficiently accurate to be used as the basis for a description of the track irregularities.
文摘Synchisite-(Ce) from the Kibina alkaline massive, Kola peninsula, Russia , has been studied using electron diffraction and lattice-images techniques. The synchisite-(Ce) with relatively ordered stacking shows a microtwin. The semirandom stacking is caused by the displacement of CO3 layers parallel to the basal planes. The irregular stacking crystals contain Ca layers adjacent to each other.The synchisite-(Ce) is considered as a polymatic mineral with short-range disorder.
基金supported by National Natural Science Foundation of China(NSFC grants 41204111,4157414641774162 and 41704155)China Postdoctoral Science Foundation(2017M622504)
文摘A theoretical model which describes the small-scale irregularities excited by powerful high frequency （3–30 MHz） electromagnetic wave in ionosphere heating is investigated quantitatively in this paper. The model is based on the transport equation in magnetic plasma and mode conversion from electromagnetic wave to electrostatic wave in ionospheric modification.Threshold electric field for exciting small-scale （meter scale） irregularities and spatial spectra of irregularities are analytically calculated by this model. The results indicate that background electron density and geomagnetic field play an important role for the threshold electric field and the spatial scale of the electron density irregularities. The results demonstrate that the electric field threshold increases with the decrease of the spatial scale of the irregularities. For exciting meter scale irregularities, the threshold electric field is about tens of mV m^（-1）. The theoretical results are consistent with those of the experiments.
基金Project supported by the Foundation of Guangxi Key Laboratory of Trusted Software, the Guangxi Natural Science Foundation, China (Grant No. 2011GXNSFA018134)the National Natural Science Foundation of China (Grant Nos. 11161013 and 61004101)
文摘In this paper, the Lie symmetry analysis and generalized symmetry method are performed for a short-wave model. The symmetries for this equation are given, and the phase portraits of the traveling wave systems are analyzed using the bifurcation theory of dynamical systems. The exact parametric representations of four types of traveling wave solutions are obtained.
