A novel traffic sign recognition system is presented in this work. Firstly, the color segmentation and shape classifier based on signature feature of region are used to detect traffic signs in input video sequences. S...A novel traffic sign recognition system is presented in this work. Firstly, the color segmentation and shape classifier based on signature feature of region are used to detect traffic signs in input video sequences. Secondly, traffic sign color-image is preprocessed with gray scaling, and normalized to 64×64 size. Then, image features could be obtained by four levels DT-CWT images. Thirdly, 2DICA and nearest neighbor classifier are united to recognize traffic signs. The whole recognition algorithm is implemented for classification of 50 categories of traffic signs and its recognition accuracy reaches 90%. Comparing image representation DT-CWT with the well-established image representation like template, Gabor, and 2DICA with feature selection techniques such as PCA, LPP, 2DPCA at the same time, the results show that combination method of DT-CWT and 2DICA is useful in traffic signs recognition. Experimental results indicate that the proposed algorithm is robust, effective and accurate.展开更多
Acoustic Emission(AE)waveforms contain information on microscopic structural features that can be related with damage of coal rock masses.In this paper,the Hilbert-Huang transform(HHT)method is used to obtain detailed...Acoustic Emission(AE)waveforms contain information on microscopic structural features that can be related with damage of coal rock masses.In this paper,the Hilbert-Huang transform(HHT)method is used to obtain detailed structural characteristics of coal rock masses associated with damage,at different loading stages,from the analyses of the characteristics of AE waveforms.The results show that the HHT method can be used to decompose the target waveform into multiple intrinsic mode function(IMF)components,with the energy mainly concentrated in the c1−c4 IMF components,where the c1 component has the highest frequency and the largest amount of energy.As the loading continues,the proportion of energy occupied by the low-frequency IMF component shows an increasing trend.In the initial compaction stage,the Hilbert marginal spectrum is mainly concentrated in the low frequency range of 0−40 kHz.The plastic deformation stage is associated to energy accumulation in the frequency range of 0−25 kHz and 200−350 kHz,while the instability damage stage is mainly concentrated in the frequency range of 0−25 kHz.At 20 kHz,the instability damage reaches its maximum value.There is a relatively clear instantaneous energy peak at each stage,albeit being more distinct at the beginning and at the end of the compaction phase.Since the effective duration of the waveform is short,its resulting energy is small,and so there is a relatively high value from the instantaneous energy peak.The waveform lasts a relatively long time after the peak that coincides with failure,which is the period where the waveform reaches its maximum energy level.The Hilbert three-dimensional energy spectrum is generally zero in the region where the real energy is zero.In addition,its energy spectrum is intermittent rather than continuous.It is therefore consistent with the characteristics of the several dynamic ranges mentioned above,and it indicates more clearly the low-frequency energy concentration in the critical stage of instability failure.This study well reflects the response law of geophysical signals in the process of coal rock instability and failure,providing a basis for monitoring coal rock dynamic disasters.展开更多
Rock joint shape characteristics,waviness and unevenness play essential but distinct roles in shear mechanism of rock joints.This study presents a novel method to generate virtual rock joint profiles with realistic wa...Rock joint shape characteristics,waviness and unevenness play essential but distinct roles in shear mechanism of rock joints.This study presents a novel method to generate virtual rock joint profiles with realistic waviness and unevenness features.Firstly,joint profiles are obtained by 3D laser scanning device.Secondly,quantification of waviness and unevenness is conducted by traditional method,including digital filtering technique and roughness parameter RL.Thirdly,the discrete Fourier transform(DFT)method is employed to analyze the joint outlines.Two representative Fourier shape descriptors(D3,D8)for characterization of waviness and unevenness are suggested.Then,the inverse discrete Fourier transform(IDFT)is adopted to reconstruct the joint profiles with random values of phase angles but prescribed amplitudes controlled by D3 and D8.The traditional method is then applied to the reconstructed joint profiles to examine statistically the relationships between D3 and D8 and parameters RL of waviness and unevenness,respectively.The results show that larger D8 tends to result in larger waviness while higher D3 tends to increase unevenness.Reference charts for estimation of waviness and unevenness with different pairs of D3 and D8 are also provided to facilitate implementation of random joint reconstruction.展开更多
Heat exchange performance of vertical U-tube heat exchanger was studied with two different borehole fill materials and CFD software. Borehole surface temperature and water temperature distribution were simulated on th...Heat exchange performance of vertical U-tube heat exchanger was studied with two different borehole fill materials and CFD software. Borehole surface temperature and water temperature distribution were simulated on the condition of continuous operation for 8 h in winter with inlet water temperature being 10℃. The results show that there is no obvious difference on heat exchanger performance between the two different borehole fill materials.展开更多
Properties of hydroxyapatite （HA, Ca10（PO4）6（OH）2）, including bioactivity, biocompatibility, solubility and adsorption could be tailored over wide ranges by the control of particle composition, particle size and...Properties of hydroxyapatite （HA, Ca10（PO4）6（OH）2）, including bioactivity, biocompatibility, solubility and adsorption could be tailored over wide ranges by the control of particle composition, particle size and morphology. In order to satisfy various applications, well-crystallized pure HA nanoparticles were synthesized at moderate temperatures by hydrotherrnal synthesis, and HA nanoparticles with different lengths were obtained by adding organic additives. X-ray diffractometry （XRD） and Fourier transform infrared （FTIR） spectrometry were used to characterize these nanoparticles, and the morphologies of the HA particles were observed by transmission electron microscopy （TEM）. The results demonstrate that shorter rod-like HA particles can be prepared by adding cetyltrimethylammonium bromide （CTAB）, as the additive of CTAB can block the HA crystal growth along with c-axis. And whisker HA particles are obtained by adding ethylenediamine tetraacetic acid （EDTA）, since EDTA may have effect on the dissolution-repreeipitation process of HA.展开更多
The influence of casting parameters on stray grain formation of a unidirectionally solidified superalloy IN738LC casting with three platforms was investigated by using a 3D cellular automaton-finite element （CAFE） m...The influence of casting parameters on stray grain formation of a unidirectionally solidified superalloy IN738LC casting with three platforms was investigated by using a 3D cellular automaton-finite element （CAFE） model in CALCOSOFT package. The model was first validated by comparison of the reported grain structure of AI-7%Si （mass fraction） alloy. Then, the influence of pouring temperature, heat flux of the lateral surface, convection heat coefficient of the cooled chill and mean undercooling of the bulk nucleation on the stray grain formation was studied during the unidirectional solidification. The predictions show that the stray grain formation is obviously sensitive to the pouring temperature, heat flux and mean undercooling of the bulk nucleation. However, increasing the heat convection coefficient has little influence on the stray grain formation.展开更多
The transient response of an unlimited cylindrical cavity buried in the infinite elastic soil subjected to an anti-plane impact load along the cavern axis direction was studied.Using Laplace transform combining with c...The transient response of an unlimited cylindrical cavity buried in the infinite elastic soil subjected to an anti-plane impact load along the cavern axis direction was studied.Using Laplace transform combining with contour integral of the Laplace inverse transform specifically,the general analytical expressions of the soil displacement and stress are obtained in the time domain,respectively.And the numerical solutions of the problem computed by analytical expressions are presented.In the time domain,the dynamic responses of the infinite elastic soil are analyzed,and the calculation results are compared with those from numerical inversion proposed by Durbin and the static results.One observes good agreement between analytical and numerical inversion results,lending the further support to the method presented.Finally,some valuable shear wave propagation laws are gained: the displacement of the soil remains zero before the wave arrival,and after the shear wave arrival,the stress and the displacement at this point increase abruptly,then reduce and tend to the static value gradually at last.The wave attenuates along the radial,therefore the farther the wave is from the source,the smaller the stress and the displacement are,and the stress and the displacement are just functions of the radial distance from the axis.展开更多
Cr(Ⅵ)-amended soil was inoculated with Cr(Ⅵ)-reducing strain,Bacillus sp.XW-4 and incubated at 28 ℃in an incubator. Cr(Ⅵ)reduction,available Cr and Cr fractionin soils were studied.The results show that addition o...Cr(Ⅵ)-amended soil was inoculated with Cr(Ⅵ)-reducing strain,Bacillus sp.XW-4 and incubated at 28 ℃in an incubator. Cr(Ⅵ)reduction,available Cr and Cr fractionin soils were studied.The results show that addition of Bacillus sp.XW-4 can promote Cr(Ⅵ)reduction,but inoculation of this strain has a negative effect on the decrease of available Cr content in soil.In controls (without this strain)amended with 100 and 200 mg/kg of Cr(Ⅵ),Cr(Ⅵ)contents decrease to about 41 and 92 mg/kg respectively after incubation of 4 d,while in soil inoculated with XW-4,Cr(Ⅵ)contents decrease to about 18 and 60 mg/kg,respectively.The content of available Cr in soils with inoculation of XW-4 is higher than that in controls.Chromium is partitioned into water soluble Cr,exchangeable Cr,precipitated Cr,Cr bound to organics and residual Cr.The highest content of Cr is observed in residual form and water soluble Cr is not detected for all treatments after 42 d,but the soils inoculated with Bacillus sp.XW-4 contain higher content of exchangeable Cr and lower content of precipitated Cr than the soil without the inoculum.Inoculation of Bacillus sp.XW-4 can increase chromium activity in soils.展开更多
Solid-state wave gyroscope is one kind of high-performance vibrating gyroscopes. The present work develops a new type of solid-state wave gyroscope—a ring vibrating gyroscope driven by piezo-electrodes located on the...Solid-state wave gyroscope is one kind of high-performance vibrating gyroscopes. The present work develops a new type of solid-state wave gyroscope—a ring vibrating gyroscope driven by piezo-electrodes located on the sidewall of the structure. It has advantages of large vibrating amplitude, high energy conversion efficiency and compact structure. The working principle of the piezoelectric ring vibrating gyroscope is based on the inertia effect of the standing wave in the axisymmetric resonator caused by Coriolis force. The finite element method(FEM) analysis has been implemented to characterize the ring type resonator. The prototypal gyroscope was manufactured and has been trimmed by mechanical way. The harmonic response of the ring vibrating gyroscope has been tested. The resonating frequency of the ring type resonator is 3715.6 Hz and the frequency split of the two working modes before trimming was about 5 Hz and was reduced to sub-0.01 Hz after trimming procedure. The Q-factor of the ring type resonator was 2504. Then, the turntable experiment was implemented. The measured scale factor k is 9.24 m V/[(°)·s] and the full scale range of the gyroscope is larger than ±300(°)/s.展开更多
This paper addresses the existence detection of blanket jamming based on fractal features in fractional Fourier transform (FRET) domain. Firstly, the existences of fractal features of three typical jamming signals are...This paper addresses the existence detection of blanket jamming based on fractal features in fractional Fourier transform (FRET) domain. Firstly, the existences of fractal features of three typical jamming signals are analyzed, and box dimension and information dimension are employed to describe fractal features quantitatively. Then the differences of fractal characteristics between blanket jamming and white Gaussian noise (WGN) in FRFT domain are described, and a detector to detect the jamming is proposed. At last, simulations are done to verify that the algorithm is effective preferable.展开更多
基金Projects(90820302, 60805027) supported by the National Natural Science Foundation of ChinaProject(200805330005) supported by Research Fund for Doctoral Program of Higher Education, ChinaProject(2009FJ4030) supported by Academician Foundation of Hunan Province, China
文摘A novel traffic sign recognition system is presented in this work. Firstly, the color segmentation and shape classifier based on signature feature of region are used to detect traffic signs in input video sequences. Secondly, traffic sign color-image is preprocessed with gray scaling, and normalized to 64×64 size. Then, image features could be obtained by four levels DT-CWT images. Thirdly, 2DICA and nearest neighbor classifier are united to recognize traffic signs. The whole recognition algorithm is implemented for classification of 50 categories of traffic signs and its recognition accuracy reaches 90%. Comparing image representation DT-CWT with the well-established image representation like template, Gabor, and 2DICA with feature selection techniques such as PCA, LPP, 2DPCA at the same time, the results show that combination method of DT-CWT and 2DICA is useful in traffic signs recognition. Experimental results indicate that the proposed algorithm is robust, effective and accurate.
基金Projects(51904167, 51474134, 51774194) supported by the National Natural Science Foundation of ChinaProject(SKLCRSM19KF008) supported by the Research Fund of the State Key Laboratory of Coal Resources and Safe Mining,CUMT,China+5 种基金Project(cstc2019jcyj-bsh0041) supported by the Natural Science Foundation of Chongqing,ChinaProject(2011DA105287-BH201903) supported by the Postdoctoral ScienceFunded by State Key Laboratory of Coal Mine Disaster Dynamics and Control,ChinaProject(2019SDZY034-2) supported by the Key R&D plan of Shandong Province,ChinaProject(2020M670781) supported by the China Postdoctoral Science FoundationProject supported by the Taishan Scholars ProjectProject supported by the Taishan Scholar Talent Team Support Plan for Advantaged&Unique Discipline Areas,China
文摘Acoustic Emission(AE)waveforms contain information on microscopic structural features that can be related with damage of coal rock masses.In this paper,the Hilbert-Huang transform(HHT)method is used to obtain detailed structural characteristics of coal rock masses associated with damage,at different loading stages,from the analyses of the characteristics of AE waveforms.The results show that the HHT method can be used to decompose the target waveform into multiple intrinsic mode function(IMF)components,with the energy mainly concentrated in the c1−c4 IMF components,where the c1 component has the highest frequency and the largest amount of energy.As the loading continues,the proportion of energy occupied by the low-frequency IMF component shows an increasing trend.In the initial compaction stage,the Hilbert marginal spectrum is mainly concentrated in the low frequency range of 0−40 kHz.The plastic deformation stage is associated to energy accumulation in the frequency range of 0−25 kHz and 200−350 kHz,while the instability damage stage is mainly concentrated in the frequency range of 0−25 kHz.At 20 kHz,the instability damage reaches its maximum value.There is a relatively clear instantaneous energy peak at each stage,albeit being more distinct at the beginning and at the end of the compaction phase.Since the effective duration of the waveform is short,its resulting energy is small,and so there is a relatively high value from the instantaneous energy peak.The waveform lasts a relatively long time after the peak that coincides with failure,which is the period where the waveform reaches its maximum energy level.The Hilbert three-dimensional energy spectrum is generally zero in the region where the real energy is zero.In addition,its energy spectrum is intermittent rather than continuous.It is therefore consistent with the characteristics of the several dynamic ranges mentioned above,and it indicates more clearly the low-frequency energy concentration in the critical stage of instability failure.This study well reflects the response law of geophysical signals in the process of coal rock instability and failure,providing a basis for monitoring coal rock dynamic disasters.
基金Projects(51478477,51878668)supported by the National Natural Science Foundation of ChinaProjects(2014122006,2017-123-033)supported by the Guizhou Provincial Department of Transportation Foundation,ChinaProject(201722ts200)supported by the Fundamental Research Funds for the Central Universities,China
文摘Rock joint shape characteristics,waviness and unevenness play essential but distinct roles in shear mechanism of rock joints.This study presents a novel method to generate virtual rock joint profiles with realistic waviness and unevenness features.Firstly,joint profiles are obtained by 3D laser scanning device.Secondly,quantification of waviness and unevenness is conducted by traditional method,including digital filtering technique and roughness parameter RL.Thirdly,the discrete Fourier transform(DFT)method is employed to analyze the joint outlines.Two representative Fourier shape descriptors(D3,D8)for characterization of waviness and unevenness are suggested.Then,the inverse discrete Fourier transform(IDFT)is adopted to reconstruct the joint profiles with random values of phase angles but prescribed amplitudes controlled by D3 and D8.The traditional method is then applied to the reconstructed joint profiles to examine statistically the relationships between D3 and D8 and parameters RL of waviness and unevenness,respectively.The results show that larger D8 tends to result in larger waviness while higher D3 tends to increase unevenness.Reference charts for estimation of waviness and unevenness with different pairs of D3 and D8 are also provided to facilitate implementation of random joint reconstruction.
基金Project(CSTC 2004AA7008 2 2) supported by Key Technologies for Development of Small Cities of ChongqingMunicipality
文摘Heat exchange performance of vertical U-tube heat exchanger was studied with two different borehole fill materials and CFD software. Borehole surface temperature and water temperature distribution were simulated on the condition of continuous operation for 8 h in winter with inlet water temperature being 10℃. The results show that there is no obvious difference on heat exchanger performance between the two different borehole fill materials.
基金Project(20070410304) supported by Postdoctoral Foundation of ChinaProject(07JJ3105) supported by Hunan Provincial Natural Science Foundation of China
文摘Properties of hydroxyapatite （HA, Ca10（PO4）6（OH）2）, including bioactivity, biocompatibility, solubility and adsorption could be tailored over wide ranges by the control of particle composition, particle size and morphology. In order to satisfy various applications, well-crystallized pure HA nanoparticles were synthesized at moderate temperatures by hydrotherrnal synthesis, and HA nanoparticles with different lengths were obtained by adding organic additives. X-ray diffractometry （XRD） and Fourier transform infrared （FTIR） spectrometry were used to characterize these nanoparticles, and the morphologies of the HA particles were observed by transmission electron microscopy （TEM）. The results demonstrate that shorter rod-like HA particles can be prepared by adding cetyltrimethylammonium bromide （CTAB）, as the additive of CTAB can block the HA crystal growth along with c-axis. And whisker HA particles are obtained by adding ethylenediamine tetraacetic acid （EDTA）, since EDTA may have effect on the dissolution-repreeipitation process of HA.
基金Project(08BZ1130100) supported by the Science and Technology Committee of Shanghai,ChinaProject(SHUCX102251) supported by the Innovation Fund for Graduate Student of Shanghai University,China
文摘The influence of casting parameters on stray grain formation of a unidirectionally solidified superalloy IN738LC casting with three platforms was investigated by using a 3D cellular automaton-finite element （CAFE） model in CALCOSOFT package. The model was first validated by comparison of the reported grain structure of AI-7%Si （mass fraction） alloy. Then, the influence of pouring temperature, heat flux of the lateral surface, convection heat coefficient of the cooled chill and mean undercooling of the bulk nucleation on the stray grain formation was studied during the unidirectional solidification. The predictions show that the stray grain formation is obviously sensitive to the pouring temperature, heat flux and mean undercooling of the bulk nucleation. However, increasing the heat convection coefficient has little influence on the stray grain formation.
文摘The transient response of an unlimited cylindrical cavity buried in the infinite elastic soil subjected to an anti-plane impact load along the cavern axis direction was studied.Using Laplace transform combining with contour integral of the Laplace inverse transform specifically,the general analytical expressions of the soil displacement and stress are obtained in the time domain,respectively.And the numerical solutions of the problem computed by analytical expressions are presented.In the time domain,the dynamic responses of the infinite elastic soil are analyzed,and the calculation results are compared with those from numerical inversion proposed by Durbin and the static results.One observes good agreement between analytical and numerical inversion results,lending the further support to the method presented.Finally,some valuable shear wave propagation laws are gained: the displacement of the soil remains zero before the wave arrival,and after the shear wave arrival,the stress and the displacement at this point increase abruptly,then reduce and tend to the static value gradually at last.The wave attenuates along the radial,therefore the farther the wave is from the source,the smaller the stress and the displacement are,and the stress and the displacement are just functions of the radial distance from the axis.
基金Project(20050532009)supported by the Doctoral Foundation of Ministry of Education of ChinaProject supported by Program for Changjiang Scholars and Innovative Research Team in University
文摘Cr(Ⅵ)-amended soil was inoculated with Cr(Ⅵ)-reducing strain,Bacillus sp.XW-4 and incubated at 28 ℃in an incubator. Cr(Ⅵ)reduction,available Cr and Cr fractionin soils were studied.The results show that addition of Bacillus sp.XW-4 can promote Cr(Ⅵ)reduction,but inoculation of this strain has a negative effect on the decrease of available Cr content in soil.In controls (without this strain)amended with 100 and 200 mg/kg of Cr(Ⅵ),Cr(Ⅵ)contents decrease to about 41 and 92 mg/kg respectively after incubation of 4 d,while in soil inoculated with XW-4,Cr(Ⅵ)contents decrease to about 18 and 60 mg/kg,respectively.The content of available Cr in soils with inoculation of XW-4 is higher than that in controls.Chromium is partitioned into water soluble Cr,exchangeable Cr,precipitated Cr,Cr bound to organics and residual Cr.The highest content of Cr is observed in residual form and water soluble Cr is not detected for all treatments after 42 d,but the soils inoculated with Bacillus sp.XW-4 contain higher content of exchangeable Cr and lower content of precipitated Cr than the soil without the inoculum.Inoculation of Bacillus sp.XW-4 can increase chromium activity in soils.
基金Projects(51335011,51275522)supported by the National Natural Science Foundation of ChinaProject(HPCM-2013-08)supported by Key Lab Open Foundation of State Key Laboratory of High Performance(Complex Manufacturing),Central South University,China
文摘Solid-state wave gyroscope is one kind of high-performance vibrating gyroscopes. The present work develops a new type of solid-state wave gyroscope—a ring vibrating gyroscope driven by piezo-electrodes located on the sidewall of the structure. It has advantages of large vibrating amplitude, high energy conversion efficiency and compact structure. The working principle of the piezoelectric ring vibrating gyroscope is based on the inertia effect of the standing wave in the axisymmetric resonator caused by Coriolis force. The finite element method(FEM) analysis has been implemented to characterize the ring type resonator. The prototypal gyroscope was manufactured and has been trimmed by mechanical way. The harmonic response of the ring vibrating gyroscope has been tested. The resonating frequency of the ring type resonator is 3715.6 Hz and the frequency split of the two working modes before trimming was about 5 Hz and was reduced to sub-0.01 Hz after trimming procedure. The Q-factor of the ring type resonator was 2504. Then, the turntable experiment was implemented. The measured scale factor k is 9.24 m V/[(°)·s] and the full scale range of the gyroscope is larger than ±300(°)/s.
基金supported by Key Laboratory of Science and Technology in Complex Electromagnetic Environment(201E-05-1)
文摘This paper addresses the existence detection of blanket jamming based on fractal features in fractional Fourier transform (FRET) domain. Firstly, the existences of fractal features of three typical jamming signals are analyzed, and box dimension and information dimension are employed to describe fractal features quantitatively. Then the differences of fractal characteristics between blanket jamming and white Gaussian noise (WGN) in FRFT domain are described, and a detector to detect the jamming is proposed. At last, simulations are done to verify that the algorithm is effective preferable.
