Pavement horizontal curve is designed to serve as a transition between straight segments, and its presence may cause a series of driving-related safety issues to motorists and drivers. As is recognized that traditiona...Pavement horizontal curve is designed to serve as a transition between straight segments, and its presence may cause a series of driving-related safety issues to motorists and drivers. As is recognized that traditional methods for curve geometry investigation are time consuming, labor intensive, and inaccurate, this study attempts to develop a method that can automatically conduct horizontal curve identification and measurement at network level. The digital highway data vehicle （DHDV） was utilized for data collection, in which three Euler angles, driving speed, and acceleration of survey vehicle were measured with an inertial measurement unit （IMU）. The 3D profiling data used for cross slope calibration was obtained with PaveVision3D Ultra technology at 1 mm resolution. In this study, the curve identification was based on the variation of heading angle, and the curve radius was calculated with ki- nematic method, geometry method, and lateral acceleration method. In order to verify the accuracy of the three methods, the analysis of variance （ANOVA） test was applied by using the control variable of curve radius measured by field test. Based on the measured curve radius, a curve safety analysis model was used to predict the crash rates and safe driving speeds at horizontal curves. Finally, a case study on 4.35 km road segment demonstrated that the proposed method could efficiently conduct network level analysis.展开更多
In this work,we report the dielectric and ferroelectric properties of CuO-doped(1-x)[0.5573Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.4427PbTiO_(3)]-xBa(Zn_(1/3)Nb_(2/3))_(3)(PMNT-xBZN)relaxor ferrielectric ceramic samples with x=0....In this work,we report the dielectric and ferroelectric properties of CuO-doped(1-x)[0.5573Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.4427PbTiO_(3)]-xBa(Zn_(1/3)Nb_(2/3))_(3)(PMNT-xBZN)relaxor ferrielectric ceramic samples with x=0.1725,0.1925,02125 and 0.2325,which were fabricated by a conventional solid-state reaction method.By introducing the CuO into PMNT-xBZN,the sintering temperature of this system is drastically lowered from 1280℃to 1120℃.The second pyrochlore phase,which is often generated during sintering at high temperature,is also inhibited.Meanwhile,broad dielectric peaks with strong dielectric relaxation characteristics are observed from150℃to 100℃.Slim and slanted P-E hysteresis loops and purely electrostrictive strains with V-shape are obtained simultaneously in studied compositions from 30℃to 150℃.These results suggest that CuO could effectively lower the sintering temperature while maintaining the dielectric and ferroelectric properties of PMNT-xBZN relaxor ferroelectric ceramics.展开更多
Ba_(0.9)Sr_(0.1)TiO_(3) ceramics with or without ZnO have been prepared by traditional solid state reaction method.The XRD analysis showed that the doped Zn^(2+) ions diffused into the BST crystal lattice,resulting in...Ba_(0.9)Sr_(0.1)TiO_(3) ceramics with or without ZnO have been prepared by traditional solid state reaction method.The XRD analysis showed that the doped Zn^(2+) ions diffused into the BST crystal lattice,resulting in the variation of dielectric properties.Especially the dielectric constant at Curie point decreased with doping ZnO content when it is lower than 0.5 mol%.Due to the promotion of sintering,doping ZnO can enhance the density of ceramics but increase grain size.However,ZnO is a kind of semiconductor and can lead to the decrease in electrical breakdown strength value.展开更多
文摘Pavement horizontal curve is designed to serve as a transition between straight segments, and its presence may cause a series of driving-related safety issues to motorists and drivers. As is recognized that traditional methods for curve geometry investigation are time consuming, labor intensive, and inaccurate, this study attempts to develop a method that can automatically conduct horizontal curve identification and measurement at network level. The digital highway data vehicle （DHDV） was utilized for data collection, in which three Euler angles, driving speed, and acceleration of survey vehicle were measured with an inertial measurement unit （IMU）. The 3D profiling data used for cross slope calibration was obtained with PaveVision3D Ultra technology at 1 mm resolution. In this study, the curve identification was based on the variation of heading angle, and the curve radius was calculated with ki- nematic method, geometry method, and lateral acceleration method. In order to verify the accuracy of the three methods, the analysis of variance （ANOVA） test was applied by using the control variable of curve radius measured by field test. Based on the measured curve radius, a curve safety analysis model was used to predict the crash rates and safe driving speeds at horizontal curves. Finally, a case study on 4.35 km road segment demonstrated that the proposed method could efficiently conduct network level analysis.
基金supported by the National Nature Science Foundation of China(Grant Nos.51772239,51761145024)the Fundamental Research Funds for the Central Universities(XJTU),the Key Scientific and Tech-nological Innovation Team of Shannxi Province(Grant No.2018TD-024)the“111”Project(Grant No.B14040).
文摘In this work,we report the dielectric and ferroelectric properties of CuO-doped(1-x)[0.5573Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.4427PbTiO_(3)]-xBa(Zn_(1/3)Nb_(2/3))_(3)(PMNT-xBZN)relaxor ferrielectric ceramic samples with x=0.1725,0.1925,02125 and 0.2325,which were fabricated by a conventional solid-state reaction method.By introducing the CuO into PMNT-xBZN,the sintering temperature of this system is drastically lowered from 1280℃to 1120℃.The second pyrochlore phase,which is often generated during sintering at high temperature,is also inhibited.Meanwhile,broad dielectric peaks with strong dielectric relaxation characteristics are observed from150℃to 100℃.Slim and slanted P-E hysteresis loops and purely electrostrictive strains with V-shape are obtained simultaneously in studied compositions from 30℃to 150℃.These results suggest that CuO could effectively lower the sintering temperature while maintaining the dielectric and ferroelectric properties of PMNT-xBZN relaxor ferroelectric ceramics.
基金The work is supported by"Fundamental Research Funds for the Central Universities"(XDJK2016E010,XDJK2015C001 and SWU113054).
文摘Ba_(0.9)Sr_(0.1)TiO_(3) ceramics with or without ZnO have been prepared by traditional solid state reaction method.The XRD analysis showed that the doped Zn^(2+) ions diffused into the BST crystal lattice,resulting in the variation of dielectric properties.Especially the dielectric constant at Curie point decreased with doping ZnO content when it is lower than 0.5 mol%.Due to the promotion of sintering,doping ZnO can enhance the density of ceramics but increase grain size.However,ZnO is a kind of semiconductor and can lead to the decrease in electrical breakdown strength value.
