Development of a 2D spatial displacement estimation method for turbulence velocimetry of the gas puff imaging system on EAST

A gas puff imaging(GPI)diagnostic has been developed and operated on EAST since 2012,and the time-delay estimation(TDE)method is used to derive the propagation velocity of fluctuations from the two-dimensional GPI data.However,with the TDE method it is difficult to analyze the data with fast transient events,such as edge-localized mode(ELM).Consequently,a method called the spatial displacement estimation(SDE)algorithm is developed to estimate the turbulence velocity with high temporal resolution.Based on the SDE algorithm,we make some improvements,including an adaptive median filter and super-resolution technology.After the development of the algorithm,a straight-line movement and a curved-line movement are used to test the accuracy of the algorithm,and the calculated speed agrees well with preset speed.This SDE algorithm is applied to the EAST GPI data analysis,and the derived propagation velocity of turbulence is consistent with that from the TDE method,but with much higher temporal resolution.

Full Scale-Aware Balanced High-Resolution Network for Multi-Person Pose Estimation

Scale variation is amajor challenge inmulti-person pose estimation.In scenes where persons are present at various distances,models tend to perform better on larger-scale persons,while the performance for smaller-scale persons often falls short of expectations.Therefore,effectively balancing the persons of different scales poses a significant challenge.So this paper proposes a newmulti-person pose estimation model called FSANet to improve themodel’s performance in complex scenes.Our model utilizes High-Resolution Network(HRNet)as the backbone and feeds the outputs of the last stage’s four branches into the DCB module.The dilated convolution-based(DCB)module employs a parallel structure that incorporates dilated convolutions with different rates to expand the receptive field of each branch.Subsequently,the attention operation-based(AOB)module performs attention operations at both branch and channel levels to enhance high-frequency features and reduce the influence of noise.Finally,predictions are made using the heatmap representation.The model can recognize images with diverse scales and more complex semantic information.Experimental results demonstrate that FSA Net achieves competitive results on the MSCOCO and MPII datasets,validating the effectiveness of our proposed approach.

Research of the wave measurement using GPS absolute velocity estimation technology

This paper analyzed the existing methods of wave measurement, and described the advantages of GPS applied in measuring the wave. The equations of absolute velocity estimation were discussed, focusing on two methods with Doppler shill. The error sources and their effect on velocity estimation were analyzed. Then, some tests were carried on to simulate dynamic velocity determination using static data Based on the high-frequency carrier-phase derived Doppler observations, the velocity has been estimated to the precision of 1 cm/s or so, even to the mm/s level. And with the receiver generated Doppler measurements, the precision can reach 3 - 15 cm/s.

Fusion of Convolutional Self-Attention and Cross-Dimensional Feature Transformationfor Human Posture Estimation

Human posture estimation is a prominent research topic in the fields of human-com-puter interaction,motion recognition,and other intelligent applications.However,achieving highaccuracy in key point localization,which is crucial for intelligent applications,contradicts the lowdetection accuracy of human posture detection models in practical scenarios.To address this issue,a human pose estimation network called AT-HRNet has been proposed,which combines convolu-tional self-attention and cross-dimensional feature transformation.AT-HRNet captures significantfeature information from various regions in an adaptive manner,aggregating them through convolu-tional operations within the local receptive domain.The residual structures TripNeck and Trip-Block of the high-resolution network are designed to further refine the key point locations,wherethe attention weight is adjusted by a cross-dimensional interaction to obtain more features.To vali-date the effectiveness of this network,AT-HRNet was evaluated using the COCO2017 dataset.Theresults show that AT-HRNet outperforms HRNet by improving 3.2%in mAP,4.0%in AP75,and3.9%in AP^(M).This suggests that AT-HRNet can offer more beneficial solutions for human posture estimation.

Inversion of walkaway VSP data in the presence of lateral velocity heterogeneity

Multi-azimuth walkaway vertical seismic profiling is an established technique for the estimation of in situ slowness surfaces and inferring anisotropy parameters.Normally,this technique requires the assumption of lateral homogeneity,which makes the horizontal slowness components at depths of downhole receivers equal to those measured at the surface.Any violations of this assumption,such as lateral heterogeneity or nonzero dip of intermediate interfaces,lead to distortions in reconstructed slowness surfaces and,consequently,to errors in estimated anisotropic parameters.In this work,we relax the assumption of lateral homogeneity and discuss how to correct vertical seismic profile data for weak lateral heterogeneity.We describe a procedure of downward continuation of recorded traveltimes that accounts for the presence of both vertical inhomogeneity and weak lateral heterogeneity,which produces correct slowness surfaces at depths of downhole receivers,noticing that sufficiently dense receiver coverage along a borehole is required to separate influences of vertical and lateral heterogeneity on measured traveltimes and obtain accurate estimates of the slowness surfaces.Once the slowness surfaces are found and a desired type of anisotropic model to be inverted is selected,the corresponding anisotropic parameters,providing the best fit to the estimated slownesses,can be obtained.We invert the slowness surfaces of P-waves for parameters of the simplest anisotropic model describing dipping fractures(transversely isotropic medium with a tilted symmetry axis).Five parameters of this model,namely,the P-wave velocity V0 in the direction of the symmetry axis,Thomsen's anisotropic coefficients e and d,the tilt n,and the azimuth b of the symmetry axis,can be estimated in a stable manner when maximum source offset is greater than half of receiver depth.

Demagnetization Analysis and Velocity Tracking Control of In-wheel Motor

The error caused by irreversible demagnetization damages the accurate velocity tracking of an in-wheel motor in a mobile robot.A current feedforward vector control system based on ESO is proposed to compensate it for the demagnetization motor.A demagnetization mathematical model is established to describe a permanent magnet synchronous motor,which took the change of permanent magnet flux linkage parameters as a factor to count the demagnetization error in velocity tracking.The uncertain disturbance estimation model of the control system is built based on ESO,which eliminates the system error by the feedforward current compensation.It is compared with the vector control method in terms of control accuracy.The simulation results show that the current feedforward vector control method based on ESO reduces the velocity tracking error greatly in conditions of motor demagnetization less than 30%.It is effective to improve the operation accuracy of the mobile robot.

Numerical Simulation for Accuracy of Velocity Analysis in Small-Scale High-Resolution Marine Multichannel Seismic Technology

When used with large energy sparkers, marine multichannel small-scale high-resolution seismic detection technology has a high resolution, high-detection precision, a wide applicable range, and is very flexible. Positive results have been achieved in submarine geological research, particularly in the investigation of marine gas hydrates. However, the amount of traveltime difference information is reduced for the velocity analysis under conditions of a shorter spread length, thus leading to poorer focusing of the velocity spectrum energy group and a lower accuracy of the velocity analysis. It is thus currently debatable whether the velocity analysis accuracy of short-arrangement multichannel seismic detection technology is able to meet the requirements of practical application in natural gas hydrate exploration. Therefore, in this study the bottom boundary of gas hydrates(Bottom Simulating Reflector, BSR) is used to conduct numerical simulation to discuss the accuracy of the velocity analysis related to such technology. Results show that a higher dominant frequency and smaller sampling interval are not only able to improve the seismic resolution, but they also compensate for the defects of the short-arrangement, thereby improving the accuracy of the velocity analysis. In conclusion, the accuracy of the velocity analysis in this small-scale, high-resolution, multi-channel seismic detection technology meets the requirements of natural gas hydrate exploration.

Velocity estimation of moving targets with stepped-frequency radar based on Doppler frequency difference

By analyzing the signal model of stepped-frequency waveform, a novel method for velocity measurement is proposed. The method is based on Doppler frequency difference which is achieved by using Hough transform. As the estimated velocity is inversely proportional to the frequency step size instead of the carrier frequency of the transmitted signal as the pulse-Doppler （PD） processing, the new algorithm can achieve much wider unambiguous velocity range. Furthermore, non-coherent integration of the sub-pulses with different carrier frequencies can be implemented by Hough trans- form to improve the anti-noise performance. Besides, field experimental results show that the high range resolution profile （HRRP） of a bullet with high speed can be reconstructed correctly without distortion.

Estimation of S-wave Velocity for Gas Hydrate Reservoir in the Shenhu Area,North South China Sea

Estimation of S-wave velocity using logging data has mainly been performed for sandstone, mudstone and oil and gas strata, while its application to hydrate reservoirs has been largely overlooked. In this paper we present petxophysical methods to estimate the S-wave velocity of hydrate reservoirs with the P-wave velocity and the density as constraints. The three models used in this paper are an equivalent model （MBGL）, a three-phase model （TPBE）, and a thermo-elasticity model （TEM）. The MBGL model can effectively describe the internal relationship among the components of the rock, and the estimated P-wave velocities are in good agreement with the measured data （2.8% error）. However, in the TPBE model, the solid, liquid and gas phases axe considered to be independent of each other, and the estimation results are relatively low （46.6% error）. The TEM model is based on the sensitivity of the gas hydrate to temperature and pressure, and the accuracy of the estimation results is also high （3.6% error）. Before the estimation, the occurrence patterns of hydrates in the Shenhu area were examined, and occurrence state one （the hydrate is in solid form in the reservoir） was selected for analysis. By using the known P-wave velocity and density as constraints, a reasonable S-wave velocity value （ranging from 400 to 1100 m s 1 and for a hydrate layer of 1100 m s 1） can be obtained through multiple iterations. These methods and results provide new data and technical support for further research on hydrates and other geological features in the Shenhu area.

Estimation of peak relative velocity and peak absolute acceleration of linear SDOF systems

We have found some mistakes in the article by Jianwei Song et al. （2007）. The revisions are given below：

AN ADAPTIVE FILTERING ALGORITHM OF VELOCITY ESTIMATION

In this paper, a novel adaptive filtering algorithm using real-time deviation of velocity estimation is presented for maneuvering target tracking. This new algorithm will be called adaptive filtering algorithm of velocity estimation. A number of simulation results indicate that the algorithm not only has good performance on tracking maneuvering target, but also greatly improves the capacity for tracking non-maneuvering target. So it is worthy to be applied widely in practice.

Stable Estimation of Horizontal Velocity for Planetary Lander with Motion Constraints

The planetary lander usually selects image feature points and tracks them from frame to frame in order to determine its own position and velocity during landing. Aiming to keep features tracking in consecutive frames, this paper proposes an approach of calculating the field of view (FOV) overlapping area in a 2D plane. Then the rotational and translational motion constraints of the lander can be found. If the FOVs intersects each other, the horizontal velocity of the lander is quickly estimated based on the least square method after the ill-conditioned matrices are eliminated previously. The Monte Carlo simulation results show that the proposed approach is not only able to recover the ego-motion of planetary lander, but also improves the stabilization performance. The relationship of the estimation error, running time and number of points is shown in the simulation results as well. © 2014 Chinese Association of Automation.

City Routing Velocity Estimation Model under theEnvironment of Lack of Floating Car Data

After introducing the principle of float car data (FCD), this paper gives the primary flow of pre-handing and map- matching of the FCD. After analyzing the percentage of coverage of FCD on the road network, large quantity of heritage database of routing status is used to estimate the routing velocity when lack of FCD on parts road segments. Multi liner regression model is then put forwarded by considering the spatial correlativity among the road network, and some model parameters are deduced when time series is classified in day and week. Besides, error of velocity probability and error of status probability are achieved based on the result from field testing while the feasibility and reliability of the velocity estimation model is obtained as well. Finally, as a case study in Shanghai center area, the whole routing velocity in the road network is estimated and published in real time.

High precision phase-domain radial velocity estimation for wideband radar systems

Radial velocity estimation used in wide-band radar systems is investigated.By analyzing the signal of cross-correlation output of adjacent echoes,it is found that the frequency and phase of the cross-correlation output are related to the target’s radial velocity.Since the precision of the phase estimation is higher than that of the frequency,a phase-based velocity estimator is proposed.However,the ambiguity problem exists in the phase estimators,and thus the estimation of the cross-correlation of adjacent echoes(CCAE)is used to calculate the ambiguity number.The root-mean-square-error(RMSE)of the proposed estimator is derived.Simulation results show that the performance of the proposed method is better than that of the frequency-based estimator.

Association of Estimated Pulse Wave Velocity and the Dynamic Changes in Estimated Pulse Wave Velocity with All-Cause Mortality among Middle-Aged and Elderly Chinese

Objective We aimed to clarify the association between estimated pulse wave velocity(ePWV)and the changes in ePWV with all-cause mortality among middle-aged and elderly Chinese.Methods Data were obtained from the China Health and Retirement Longitudinal Study(CHARLS)from 2011-2018.The ePWV was calculated using an equation that included age and mean blood pressure(MBP).The ΔePWV was assessed as the difference in ePWV between the first two waves.Cox proportional hazard models were used to determine the association between ePWV and ΔePWV with all-cause mortality after adjustment for potential confounders.Results Of 13,116 participants during a median follow-up of 7.0 years,1,356 deaths occurred.An increased ePWV was independently associated with all-cause mortality.The hazard ratio[95% confidence interval(CI)]for participants from the 1^(st)-4^(th) quartile groups was 1.00,1.69(1.31-2.18),3.09(2.44-3.91),and 8.54(6.78-10.75),respectively.Each standard deviation(SD)increment of ePWV increased the risk of all-cause mortality by 132%.Furthermore,theΔePWV was significantly associated with a 1.28-fold(95%CI,1.18-1.38)risk of all-cause mortality per SD increment.Conclusion This cohort study provided novel evidence from a Chinese population that an increased ePWV or progression of the ePWV was independently associated with all-cause mortality,which highlighted the importance of mitigating ePWV progression in clinical practice.

An improved multidirectional velocity model for micro-seismic monitoring in rock engineering

An improved multidirectional velocity model was proposed for more accurately locating micro-seismic events in rock engineering. It was assumed that the stress wave propagation velocities from a micro-seismic source to three nearest monitoring sensors in a sensor's array arrangement were the same. Since the defined objective function does not require pre-measurement of the stress wave propagation velocity in the field, errors from the velocity measurement can be avoided in comparison to three traditional velocity models. By analyzing 24 different cases, the proposed multidirectional velocity model iterated by the Simplex method is found to be the best option no matter the source is within the region of the sensor's array or not. The proposed model and the adopted iterative algorithm are verified by field data and it is concluded that it can significantly reduce the error of the estimated source location.

Re-adhesion control strategy based on the optimal slip velocity seeking method

In the railway industry, re-adhesion control plays an important role in attenuating the slip occurrence due to the low adhesion condition in the wheel-rail inter- action. Braking and traction forces depend on the normal force and adhesion coefficient at the wheel-rail contact area. Due to the restrictions on controlling normal force, the only way to increase the tractive or braking effect is to maximize the adhesion coefficient. Through efficient uti- lization of adhesion, it is also possible to avoid wheel-rail wear and minimize the energy consumption. The adhesion between wheel and rail is a highly nonlinear function of many parameters like environmental conditions, railway vehicle speed and slip velocity. To estimate these unknown parameters accurately is a very hard and competitive challenge. The robust adaptive control strategy presented in this paper is not only able to suppress the wheel slip in time, but also maximize the adhesion utilization perfor- mance after re-adhesion process even if the wheel-rail contact mechanism exhibits significant adhesion uncer- tainties and/or nonlinearities. Using an optimal slip velocity seeking algorithm, the proposed strategy provides a satisfactory slip velocity tracking ability, which was demonstrated able to realize the desired slip velocity without experiencing any instability problem. The control torque of the traction motor was regulated continuously to drive the railway vehicle in the neighborhood of the opti- mal adhesion point and guarantee the best traction capacity after re-adhesion process by making the railway vehicle operate away from the unstable region. The results obtained from the adaptive approach based on the second- order sliding mode observer have been confirmed through theoretical analysis and numerical simulation conducted in MATLAB and Simulink with a full traction model under various wheel-rail conditions.

估算的脉搏波传导速度对新发糖尿病的影响

目的:探讨估算的脉搏波传导速度(ePWV)对新发糖尿病的影响。方法:以参加2006年7月至2007年10月健康体检、既往无糖尿病病史且资料完整的82 440例开滦集团公司职工为观察队列,平均随访(13.19±3.73)年。将研究人群按ePWV四分位数分为四组:Q_1组(ePWV<12.35 m/s,n=20 610)、Q_(2)组(12.35 m/s≤ePWV<13.74 m/s,n=20 610)、Q_3组(13.74 m/s≤ePWV<15.16 m/s,n=20 611)和Q_4组(ePWV≥15.16 m/s,n=20 609),计算各组糖尿病的发病密度。采用ROC曲线分析ePWV对新发糖尿病的预测价值。在校正传统心血管危险因素(包括性别、吸烟、饮酒、体育锻炼、文化程度、心血管疾病家族史、心肌梗死史、脑卒中史、体重指数、总胆固醇、空腹血糖、血尿酸和高敏C反应蛋白)后,采用多因素Cox回归模型分析ePWV对新发糖尿病的影响。结果:ePWV预测新发糖尿病的ROC曲线的AUC为0.60,最佳截断值为12.78 m/s。随着ePWV四分位数的递增,糖尿病的发病密度呈递增趋势,分别为5.84/千人年、12.04/千人年、15.70/千人年和16.87/千人年。在校正性别、基线空腹血糖、吸烟、饮酒等传统心血管危险因素后,ePWV每增加1 m/s,糖尿病的发生风险增加9%(HR=1.09,95%CI:1.08~1.11,P<0.01)。进一步分析显示,无论有无心血管危险因素、男性还是女性、年龄<51岁还是≥51岁,ePWV均与糖尿病的发生存在显著关联,HR(95%CI)分别为1.07(1.05~1.08)和1.21(1.08~1.36),1.07(1.06~1.09)和1.17(1.15~1.20),1.22(1.19~1.24)和1.06(1.04~1.07)。结论:ePWV对新发糖尿病具有一定的预测价值,是新发糖尿病的独立危险因素。

基于多频脉冲采样的血流速度估计方法

传统双模超声技术相较于新兴技术更具实现可穿戴化的潜力。在进行脉冲多普勒血流速度估计时,双模超声需同时发射B模式脉冲进行成像定位,这要求B模式脉冲和多普勒脉冲共享采样时间。采用基于单频多普勒脉冲的稀疏间隔发射方式可以解决这一问题,但常见的稀疏发射排布方式(如嵌套发射、互质发射等)存在采样时间窗较长的缺点,特别是在血流速度变化明显的情况下存在时间分辨率不足的问题。此外,长时间窗包含了较多的血流速度分量,容易由于稀疏采样引起伪影,从而影响血流速度估计的准确性。因此,文中提出了一种基于多频脉冲采样的新型血流速度估计方法。首先,构建了多频脉冲采样的回波模型,并对该模型进行推导,证明了在频率衰减平稳假设下,该数学模型等价于单频多普勒脉冲稀疏发射方式,即多频脉冲采样可以通过较短的时间窗实现类似于基于单频脉冲采样模式的长时间窗的性能,从而提高血流速度谱的时间分辨率和估计精度;然后,提出了两种可用于多频脉冲采样模式的血流速度谱的构建方法,分别为复杂度较低的BMUSIC算法和伪影抑制效果较佳的VMUSIC算法。基于FieldⅡ仿真数据和人体实测数据的实验结果表明:相较于单频多普勒脉冲稀疏发射方式,文中方法不仅可以采用较短的时间窗提升血流速度谱的时间分辨率,还可以获得连续、清晰、精度较高且伪影抑制效果较佳的血流速度估计结果;在人体实测数据实验中,由于实验条件所限,文中方法无法实现非整数倍频,未能充分展现VMUSIC算法的性能优势。

基于线性调频连续波的合作式通信辐射源测距

针对加速运动目标参数估计中,离散多项式变换方法无法进行非整数估计的问题,本文提出基于瑞夫算法的离散多项式变换法和基于Chirp-Z变换的离散多项式变换法2种新型离散多项式变换算法,对加速运动目标速度和加速度进行估计,并对2种算法的估计误差和计算量进行了分析比较。结果表明:2种算法在信噪比-20 dB时均方误差开始接近克拉美罗界。基于瑞夫算法的离散多项式变换法与3次迭代基于Chirp-Z变换的离散多项式变换法均可在较低信噪比下可实现任意频率的有效估计且性能接近,二者均可实现低信噪比下速度、加速度的有效估计,但基于瑞夫算法的离散多项式变换法计算量远小于3次迭代基于Chirp-Z变换的离散多项式变换法。