Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. ...Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. Aimed at a high-speed railway engineering practice in the newly built Yun-Gui high-speed railway expansive soil section in China, indoor vibration test on a full-scaled new cutting subgrade model is carried out. Based on the established track-subgrade-foundation of expansive soil system dynamic model test platform, dynamic behavior of new cutting subgrade structure under train loads coupling with extreme service environment(dry, raining, and groundwater level rising) is analyzed comparatively. The results show that the subgrade dynamic response is significantly influenced by service conditions and the dynamic response of subgrade gradually becomes stable with the increasing vibration times under various service environment conditions. The vertical dynamic soil stress is related with the depth in an approximate exponential function, and the curves of vertical dynamic soil stress present a "Z" shape distribution along transverse distance. The peak value of dynamic soil stress appears below the rail, and it increases more obviously near the roadbed surface. However, the peak value of dynamic soil stress is little affected outside 5.0 m of center line. The vibration velocity and acceleration are in a quadratic curve with an increase in depth, and the raining and groundwater level rising increase both the vibration velocity and the acceleration. The vertical deformations at different depths are differently affected by service environment in roadbed. The deformation of roadbed increases sharply when the water gets in the foundation of expansive soil, and more than 60% of the total deformation of roadbed occurs in expansive soil foundation. The laid waterproofing and drainage structure layer, which weakens the dynamic stress and improves the track regularity, presents a positive effect on the control deform展开更多
针对GPS接收机的功率倒置算法(PI)在高动态环境下的加权系数更新速度滞后于干扰入射的变化速度问题,提出基于零陷加宽的PI功率倒置算法,通过零陷的加宽对来向干扰的接触面积更大,能抑制干扰的角度范围更大。同时为了满足硬件平台的可行...针对GPS接收机的功率倒置算法(PI)在高动态环境下的加权系数更新速度滞后于干扰入射的变化速度问题,提出基于零陷加宽的PI功率倒置算法,通过零陷的加宽对来向干扰的接触面积更大,能抑制干扰的角度范围更大。同时为了满足硬件平台的可行性,改进了基于零陷加宽的PI功率倒置算法,对协方差矩阵引入了与零陷宽度相关的矩阵T,一次权值更新只需计算一次协方差矩阵。仿真结果表明在高动态环境下,抗干扰的零陷增益达到68 d B。在DSP+FPGA的硬件平台上,一次权值更新时间只需6.3 ms,满足高动态的干扰入射角度的变化速度。展开更多
同时定位与地图构建(Simultaneous Localization and Mapping,SLAM)在人工智能领域有着不可替代的作用。传统的视觉SLAM算法在静态环境下具有较好的稳定性,但在动态场景下的鲁棒性和准确性较差,影响了其定位精度。为了解决这个问题,提...同时定位与地图构建(Simultaneous Localization and Mapping,SLAM)在人工智能领域有着不可替代的作用。传统的视觉SLAM算法在静态环境下具有较好的稳定性,但在动态场景下的鲁棒性和准确性较差,影响了其定位精度。为了解决这个问题,提出了一种结合ORB-SLAM3、语义分割线程和几何线程的语义视觉SLAM方法,利用DeepLabv 3+语义分割网络来分割潜在的先验动态对象,再通过几何线程使用多视图几何方法来检测动态对象的运动状态信息,剔除掉动态对象上的特征点,使用剩余的静态特征点求解相机位姿。最后,提出了一种新的蜣螂优化方案,通过最优路径找到所有动态特征点的集合,避免遍历所有特征点,减少动态目标检测时间,提高系统的实时性。通过在公开数据集上进行实验,结果表明,与同类算法相比,本文提出的方法有效提高了系统在高动态环境下的定位精度,提高了系统的实时性。展开更多
Evaluation of the conspicuity of roadway environments for their environmental impact on driving performance is vital for roadway safety. Existing meters and tools for roadway measurements cannot record light and geome...Evaluation of the conspicuity of roadway environments for their environmental impact on driving performance is vital for roadway safety. Existing meters and tools for roadway measurements cannot record light and geometry data simultaneously in a high resolution. This study introduced a new method that adopted recently developed high dynamic range (HDR) photogrammetry to measure the luminance and XYZ coordinates of millions of points across a road scene with the same device—a camera, and a MatLab code for data treatment and visualization. To validate this method, the roadway environments of a straight and flat section of Jayhawk Boulevard (482.8 m long) at Lawrence, KS and a roundabout (15.3 m in diameter) at its end were measured under clear and cloudy sky in the daytime and at nighttime with dry and wet pavements. Eight HDR images of the roadway environments under different viewing conditions were generated using the HDR photogrammetric techniques and calibrated. From each HDR image, synchronous light and geometry data were extracted in Radiance and further analyzed to identify potential roadway environmental hazards using the MatLab code (http://people.ku.edu/~h717c996/research.html). The HDR photogrammetric measurement with current equipment had a margin of errors for geometry measurement that varied with the measuring distance, averagely 23.1% - 27.5% for the Jayhawk Boulevard and 9.3% - 16.2% for the roundabout. The accuracy of luminance measurement was proven in the literature as averagely 1.5% - 10.1%. The camera-aided measurement is fast, non-contact, non-destructive, and off the road, thus, it is deemed more efficient and safer than conventional ways using meters and tools. The HDR photogrammetric techniques with current equipment still need improvements on accuracy and speed of the data treatment.展开更多
To acquire global navigation satellite system(GNSS)signals means four-dimension acquisition of bit transition,Doppler frequency,Doppler rate,and code phase in high-dynamic and weak signal environments,which needs a hi...To acquire global navigation satellite system(GNSS)signals means four-dimension acquisition of bit transition,Doppler frequency,Doppler rate,and code phase in high-dynamic and weak signal environments,which needs a high computational cost.To reduce the computations,this paper proposes a twostep compressed acquisition method(TCAM)for the post-correlation signal parameters estimation.Compared with the fast Fourier transform(FFT)based methods,TCAM uses fewer frequency search points.In this way,the proposed method reduces complex multiplications,and uses real multiplications instead of improving the accuracy of the Doppler frequency and the Doppler rate.Furthermore,the differential process between two adjacent milliseconds is used for avoiding the impact of bit transition and the Doppler frequency on the integration peak.The results demonstrate that due to the reduction of complex multiplications,the computational cost of TCAM is lower than that of the FFT based method under the same signal to noise ratio(SNR).展开更多
基金Projects(51478484,51308551,51678571)supported by the National Natural Science Foundation of ChinaProject(2016zzts063)supported by Fundamental Research Funds for the Central Universities,China
文摘Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. Aimed at a high-speed railway engineering practice in the newly built Yun-Gui high-speed railway expansive soil section in China, indoor vibration test on a full-scaled new cutting subgrade model is carried out. Based on the established track-subgrade-foundation of expansive soil system dynamic model test platform, dynamic behavior of new cutting subgrade structure under train loads coupling with extreme service environment(dry, raining, and groundwater level rising) is analyzed comparatively. The results show that the subgrade dynamic response is significantly influenced by service conditions and the dynamic response of subgrade gradually becomes stable with the increasing vibration times under various service environment conditions. The vertical dynamic soil stress is related with the depth in an approximate exponential function, and the curves of vertical dynamic soil stress present a "Z" shape distribution along transverse distance. The peak value of dynamic soil stress appears below the rail, and it increases more obviously near the roadbed surface. However, the peak value of dynamic soil stress is little affected outside 5.0 m of center line. The vibration velocity and acceleration are in a quadratic curve with an increase in depth, and the raining and groundwater level rising increase both the vibration velocity and the acceleration. The vertical deformations at different depths are differently affected by service environment in roadbed. The deformation of roadbed increases sharply when the water gets in the foundation of expansive soil, and more than 60% of the total deformation of roadbed occurs in expansive soil foundation. The laid waterproofing and drainage structure layer, which weakens the dynamic stress and improves the track regularity, presents a positive effect on the control deform
文摘针对GPS接收机的功率倒置算法(PI)在高动态环境下的加权系数更新速度滞后于干扰入射的变化速度问题,提出基于零陷加宽的PI功率倒置算法,通过零陷的加宽对来向干扰的接触面积更大,能抑制干扰的角度范围更大。同时为了满足硬件平台的可行性,改进了基于零陷加宽的PI功率倒置算法,对协方差矩阵引入了与零陷宽度相关的矩阵T,一次权值更新只需计算一次协方差矩阵。仿真结果表明在高动态环境下,抗干扰的零陷增益达到68 d B。在DSP+FPGA的硬件平台上,一次权值更新时间只需6.3 ms,满足高动态的干扰入射角度的变化速度。
文摘同时定位与地图构建(Simultaneous Localization and Mapping,SLAM)在人工智能领域有着不可替代的作用。传统的视觉SLAM算法在静态环境下具有较好的稳定性,但在动态场景下的鲁棒性和准确性较差,影响了其定位精度。为了解决这个问题,提出了一种结合ORB-SLAM3、语义分割线程和几何线程的语义视觉SLAM方法,利用DeepLabv 3+语义分割网络来分割潜在的先验动态对象,再通过几何线程使用多视图几何方法来检测动态对象的运动状态信息,剔除掉动态对象上的特征点,使用剩余的静态特征点求解相机位姿。最后,提出了一种新的蜣螂优化方案,通过最优路径找到所有动态特征点的集合,避免遍历所有特征点,减少动态目标检测时间,提高系统的实时性。通过在公开数据集上进行实验,结果表明,与同类算法相比,本文提出的方法有效提高了系统在高动态环境下的定位精度,提高了系统的实时性。
文摘Evaluation of the conspicuity of roadway environments for their environmental impact on driving performance is vital for roadway safety. Existing meters and tools for roadway measurements cannot record light and geometry data simultaneously in a high resolution. This study introduced a new method that adopted recently developed high dynamic range (HDR) photogrammetry to measure the luminance and XYZ coordinates of millions of points across a road scene with the same device—a camera, and a MatLab code for data treatment and visualization. To validate this method, the roadway environments of a straight and flat section of Jayhawk Boulevard (482.8 m long) at Lawrence, KS and a roundabout (15.3 m in diameter) at its end were measured under clear and cloudy sky in the daytime and at nighttime with dry and wet pavements. Eight HDR images of the roadway environments under different viewing conditions were generated using the HDR photogrammetric techniques and calibrated. From each HDR image, synchronous light and geometry data were extracted in Radiance and further analyzed to identify potential roadway environmental hazards using the MatLab code (http://people.ku.edu/~h717c996/research.html). The HDR photogrammetric measurement with current equipment had a margin of errors for geometry measurement that varied with the measuring distance, averagely 23.1% - 27.5% for the Jayhawk Boulevard and 9.3% - 16.2% for the roundabout. The accuracy of luminance measurement was proven in the literature as averagely 1.5% - 10.1%. The camera-aided measurement is fast, non-contact, non-destructive, and off the road, thus, it is deemed more efficient and safer than conventional ways using meters and tools. The HDR photogrammetric techniques with current equipment still need improvements on accuracy and speed of the data treatment.
基金supported by the National Natural Science Foundation of China(61901154,41704154)Zhejiang Province Science Foundation for Youths(LQ19F010006).
文摘To acquire global navigation satellite system(GNSS)signals means four-dimension acquisition of bit transition,Doppler frequency,Doppler rate,and code phase in high-dynamic and weak signal environments,which needs a high computational cost.To reduce the computations,this paper proposes a twostep compressed acquisition method(TCAM)for the post-correlation signal parameters estimation.Compared with the fast Fourier transform(FFT)based methods,TCAM uses fewer frequency search points.In this way,the proposed method reduces complex multiplications,and uses real multiplications instead of improving the accuracy of the Doppler frequency and the Doppler rate.Furthermore,the differential process between two adjacent milliseconds is used for avoiding the impact of bit transition and the Doppler frequency on the integration peak.The results demonstrate that due to the reduction of complex multiplications,the computational cost of TCAM is lower than that of the FFT based method under the same signal to noise ratio(SNR).
