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Rainbow particle tracking velocimetry can be used to measure 3D3C flow velocity vectors with a single color camera. The particle depth position is calculated from the hue degree of a particle color. A liquid–crystal display (LCD) projector can be used conveniently as a light source of the color pattern in place of the spectral diffraction of white light. Another advantage of using an LCD projector is the ability to change the RGB components of the color pattern. In this study, the rainbow color pattern was modified to increase available color. Colors with the same hue degree but different saturations were used in the color pattern. Using color space enhanced positional resolution in the color change direction. The parameters of new color patterns were number of cycles, saturation continuity and range of color space. They were designed and their performances were compared. The effective resolution in color change direction enhanced 2.4 times from original patten (single cycle rainbow), and velocity vector acquisition rate improved, in particular, for the range of small amount movement per step. [ABSTRACT FROM AUTHOR]

Velocity is fundamental information for ocean engineering. It is difficult for traditional Doppler sonar to provide accurate and wide-range velocity measurement information with a short time lag. Therefore, a frequency-supervised combined Doppler sonar system using an adaptive sliding window and Kalman filter is proposed. In this method, the initial value of the integer ambiguity is calculated based on the average value of the conventional Doppler sonar. The change value of the integer ambiguity is calculated by the difference of the adjacent velocities measured by coherent Doppler sonar. The velocity of combined Doppler sonar is calculated by the cumulative result of the initial and change values of integer ambiguities. Finally, the velocity bias due to the error of the integer ambiguity calculation is corrected by the frequency supervision using the Kalman filter in a sliding time window under different signal-to-noise ratios. The experimental results show that the proposed method is more accurate than the conventional Doppler sonar, has a wider measurement range compared with coherent Doppler sonar, and suppresses the impulsive noise well. The frequency-supervised combined Doppler sonar using an adaptive sliding window and Kalman filter can provide accurate and precise velocities with a short time lag over a wide range of signal-to-noise ratios. [ABSTRACT FROM AUTHOR]

Fluorescent tuft visualization technology, as a practical and convenient technique, has attracted widespread attention. In this study, a novel fluorescent tuft velocity measurement method is developed based on existing technologies. This method involves the recognition of tuft deflection angles, image transformation, block processing, temporal averaging, and post-visualization processing. Additionally, quantitative measurement of flow field velocity is achieved through tuft calibration. The study begins by comparing tufts of different materials, examining both fluorescent and deflection characteristics to determine optimal tuft parameters. The impact of tuft length on deflection characteristics is also investigated. Finally, the cotton tuft with a length of 7 mm and a diameter of about 0.1 mm was obtained as the best tuft sought in this experiment. Subsequently, at Reynolds number Re = 1.7 × 105, airfoil surface flow field visualization and quantitative analysis are conducted, exploring the relationship between airfoil surface flow structure and aerodynamics at different angles of attack. Finally, a comparative study is conducted between tuft velocity results and oil flow visualization experiments, as well as particle image velocimetry experiments, confirming the feasibility of the fluorescent tuft velocity measurement method. [ABSTRACT FROM AUTHOR]

To accelerate the convergence rate of high-dimensional optimization problems, inspired by the cooperative hunting process of spider colonies named Anelosimus eximius, a new A. eximius colony algorithm (AECA) was proposed to solve combinatorial optimization problems. In the AECA, a certain direction component of the problem solution is represented as a certain direction in which a spider travels, so that a high-dimensional optimization problem can be transformed into multiple low-dimensional optimization problems. The AECA includes two intelligent behaviors: the random walk of spiders and the summoning of the initiator. The random walk of spiders ensures the diversity of spider colonies, whereas the summoning of the initiator can accelerate the convergence rate. We theoretically proved that the AECA is globally convergent. The inversion method of asteroid spectrum reflectance template can be used to solve the problem that the measured planetary spectrum is affected by the asteroid absorption effect and improves the accuracy of celestial Doppler difference velocimetry, which uses celestial spectrum to provide the information of velocity measurement for navigation. The essence of this method is the optimal combination problem of intrinsic mode functions (IMFs). We applied the AECA to the inversion of the planetary spectrum reflectance template. Experimental results show that, compared with genetic algorithms (GAs), the AECA can obtain the optimal combination of spectrum reflectance templates faster. In addition, to verify the universality of the AECA, for the classical knapsack problem, the AECA has a better optimization effect, faster convergence rate, and higher stability than other swarm intelligence algorithms such as GA, discrete particle swarm optimization, and the quantum genetic algorithm. [ABSTRACT FROM AUTHOR]

The moving block system provided by CBTC increases train operation frequency and improves facilities management efficiency compared to the fixed block system. Trains controlled by CBTC need to have onboard functions to estimate their locations. One method for location estimation involves integrating the measured translational velocity of the trains based on the angular velocity of the wheelset. However, this method may introduce errors in measuring the traveling distance because the angular velocity of the wheelset can be changed on curved tracks due to shifting contact points, longitudinal creepages, and other factors. To observe the phenomenon of angular velocity changes on curved tracks, experiments and simulations were conducted. The results of both experiments and simulations are similar, showing that the angular velocity of wheelsets changes on the curved track and the relative changes differ between the front and rear axles of the bogie. The mechanisms of the angular velocity changing is clarified, identifying three factors: arc length differences between high and low rails, changes in rolling radius on wheels, and longitudinal creepages. Additionally, the impacts of these factors are formulated, indicating that the relative change in angular velocity on curved tracks can be estimated by the sum of the formulated impact factors. Moreover, the visualization method for the mechanism determinating the wheelsets’ angular velocity is developed. This method helps to clarify the reasons for the different relative change observed between the front and rear axles in the bogie during experiments. Specifically, it suggests that the different directions of longitudinal creepages cause the different relative change in the wheelsets’ angular velocity.

The performance of Doppler velocity logs (DVLs) in terms of velocity estimate error is directly linked to the geometry of the beam and the pulse transmitted. Beyond a specific transmitted bandwidth, the phase‐shift beamformer can introduce significant errors in velocity estimation. To delineate the operating mechanism of phase‐shift errors within a phased array of acoustic DVLs, the correlation between bottom echo and velocity distribution, in conjunction with the power‐weighted function, was initially examined predicated on spectral estimation theory. Subsequently, numerical and analytical models of the Gaussian‐shaped Doppler spectrum were formulated. The models are employed to evaluate the velocity estimation inaccuracies attributed to phase shifts in extant DVLs, and the comparative results with field experiments corroborate the model's efficacy in forecasting errors. The theoretical findings evaluate the performance limitations of the current phased array transducer design and provide insights for developing new designs. Pool experimental results show that this design effectively reduces the velocity estimation error caused by phase shift under static conditions and in the presence of Doppler frequencies to a level of almost complete elimination of the error compared to conventional configurations. [ABSTRACT FROM AUTHOR]

Submerged entry nozzle (SEN) clogging will affect the production efficiency and product quality in the continuous casting process. In this work, the transient SEN clogging model is developed by coupling the porous media model defined by the user-defined function (UDF) and the discrete phase model (DPM). The effects of the transient SEN clogging process on the flow field, the distribution of argon gas bubbles and the fluctuation of the interface between steel and slag in the concave bottom SEN in the continuous casting slab mold with a cross-section of 1500 mm × 230 mm are studied by coupling transient SEN clogging model, DPM and volume of fluid (VOF) model. The results show that the actual morphology and thicknesses of SEN clogging are in good agreement with the numerical simulation results. The measurement result of the surface velocity is consistent with the numerical simulation result. With increasing the simulation time, the degree of SEN clogging increases. The flow velocities of molten steel flowing from the outlet of the side hole increase, because the flow space is occupied with the clogging inclusions, which leads to the increased number of argon gas bubbles near the narrow wall. The steel–slag interface fluctuation near the narrow walls also increases, resulting in the increased risk of slag entrapment. [ABSTRACT FROM AUTHOR]

The automated removal of layers by scarfing to repair carbon fibre reinforced plastics (CFRP) has been investigated with vacuum suction blasting (VSB) showing promising results. However, its removal mechanism and particle behaviour were not yet fully understood. The removal leads to cavities on the surface and the central area is less removed after longer static blasting times. Further theoretical considerations and experiments of measured forces and velocities of the VSB particles can explain these effects to optimize the large-scale removal. Former studies on abrasive blasting used simplified approaches with incompressible Bernoulli equations taking the same velocities of particles and carrier medium. For VSB, the air is much faster than the particles and more complex equations are derived in this study. Additionally, it is taken into account, that the impinging forces act against the vacuum forces. To specify the power and removal mechanism of VSB for large scale removal, forces and velocities of the blasting particles are studied. Calculations by compressible Bernoulli equations, measurements of blasting particle velocities and impact forces give a good approximation. The air velocities and forces are calculated and compared with the measurements. Forces are measured by a piezo-electric sensor. Particle velocities are measured with a Particle Image Velocimetry (PIV) system tracking the abrasive particle movement through a transparent outer nozzle. The influence of different blasting parameters on the forces and velocities are identified. Results correspond to the material removal from former experiments and indicate the favourable process parameter set. Despite the impinging forces are in general low, they lead together with the particle velocity to the large-scale removal rate. The measured particle directions explain the removal behaviour of this VSB process. The measured velocities match to those well-known from grinding with bonded grinding tools. Article highlights: Force and velocity measurements of vacuum suction blasting process PIV measurements of blasting particles Forces calculated and measured by piezo-electric sensor. [ABSTRACT FROM AUTHOR]

• The flow characteristics of vertical slot fishways at different slopes (1.5%, 3.0%, 4.5%, 6.0%) were systematically studied. • The turbulence and energy dissipation in a fishway increase with increasing slope. • The distribution of vorticity shows little variability with increasing slope but may interfere with the passage of fish through the vertical slot. • An increase in water depth has no significant effect on the flow characteristics in the pool. The effects of a vertical slot fishway slope (with slope values from 1.5% to 6%) on a flow field are numerically investigated, using a re-normalization group k – ε model. The distribution of the velocity, turbulence kinetic energy (TKE), average energy dissipation rate per unit volume (E), and vorticity for different slopes are systemically explored. The results indicate that, with an increase in slope, the appearance of downward flow in conjunction with an increase in vertical velocity results in three-dimensional flow characteristics. The recirculation region in H s , at a 6.0% slope, was 20.9% less than that at a 1.5% slope. Meanwhile, the flow velocity in the vertical slot region grew with increasing slope, which would limit the passage of fish with burst speed lower than the velocity in the vertical slot region. The TKE and E may locally exceed the threshold at larger slopes. Furthermore, vorticity distribution shows little variability with increasing slope, but may interfere with the equilibrium of the fish in the vertical slot region. In addition, the change in water level has little effect on the flow field, which is changed by the increase in slope. These findings can aid vertical slot fishway designs especially in terms of the efficiency of fish passage. [ABSTRACT FROM AUTHOR]

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Velocity is fundamental information for ocean engineering. It is difficult for traditional Doppler sonar to provide accurate and wide-range velocity measurement information with a short time lag. Therefore, a frequency-supervised combined Doppler sonar system using an adaptive sliding window and Kalman filter is proposed. In this method, the initial value of the integer ambiguity is calculated based on the average value of the conventional Doppler sonar. The change value of the integer ambiguity is calculated by the difference of the adjacent velocities measured by coherent Doppler sonar. The velocity of combined Doppler sonar is calculated by the cumulative result of the initial and change values of integer ambiguities. Finally, the velocity bias due to the error of the integer ambiguity calculation is corrected by the frequency supervision using the Kalman filter in a sliding time window under different signal-to-noise ratios. The experimental results show that the proposed method is more accurate than the conventional Doppler sonar, has a wider measurement range compared with coherent Doppler sonar, and suppresses the impulsive noise well. The frequency-supervised combined Doppler sonar using an adaptive sliding window and Kalman filter can provide accurate and precise velocities with a short time lag over a wide range of signal-to-noise ratios.

The navigation and velocity measurement methods using GPS (global positioning system) signals based on a side-mounted single patch antenna are key technologies of the trajectory correction projectile. However, when the single patch antenna on the projectile receives the GPS signals at a high spin rate, there are effects such as the periodic Doppler shift induced by the rotation and crystal oscillator frequency offset, and periodic blockage that interferes with the measurement of the projectile's velocity. By analyzing the characteristics of the Doppler frequency of carrier and pseudorange rate, we propose a velocity measurement method using pseudorange rate to separate crystal oscillator frequency offset-induced Doppler shift and estimate the velocity for high-spinning projectiles by optimization. This method eliminates hazardous frequency induced by rotation and facilitates precise velocity measurement. The method has been verified through testbed experiments. The experimental results show that after eliminating hazardous Doppler frequency under high spin rate conditions, the root mean square error (RMSE) of velocity measurement was 0.42 m/s, which meets the requirements for velocity measurement in trajectory correction projectiles. [ABSTRACT FROM AUTHOR]

Oil droplets of S/O/W emulsion were manipulated by magnetic field. This S/O/W emulsion is safflower oil, containing magnetic particles, dispersed in water. This S/O/W emulsion is prepared using SPG membrane. First, magnetic field were applied to the statically placed S/O/W emulsion by an electromagnet from the side. As a result, the oil droplets moved in the direction of the magnet. Then, the magnetic field were applied to the oil droplets of the S/O/W emulsion flowing in a bifurcated channel branching in two directions. As a result, more than half of the oil droplets were guided to one of the branches. These experiments showed the larger the diameter of the oil droplets and the stronger the magnetic field, the faster the oil droplets moved. The larger the diameter of the oil droplet, the more it was guided to one of the branches. [ABSTRACT FROM AUTHOR]

The radar-based analysis of human motion is actively being researched due to its contact- and markerless nature and ability to measure motion directly via the Doppler effect. Especially in medical and biomechanical fields, precise movement analysis is crucial. However, existing radar-based studies typically exhibit low lateral resolution, focusing on velocity evaluations and the tracking of scattering centers resolvable in the range or Doppler domains. In this work, we present a novel concept that enables a pixel-wise velocity analysis of human motion in radar near-field imaging scenarios. For this, we utilize the well-established back-projection technique to reconstruct consecutive radar images and perform a subsequent pixel-wise phase comparison. To accurately capture pixel-specific velocities along the depth dimension, this is followed by corrections of near-field geometry distortions accounting for aperture properties and pixel positions. Our theoretical derivations are supported by comprehensive point target simulations. To assess the performance of the proposed approach, we conducted a proof-of-concept study. We tracked a hand surface's movement while performing a finger tapping motion and compared the fingertip position and velocity determined by the radar with the respective values obtained from an optical marker-based system. The results showed a velocity measurement accuracy of $8.1 \,\mathrm{mms}^{-1}$ and a tracking accuracy of $1.4 \,\mathrm{m}\mathrm{m}$, demonstrating the great potential of our approach. The high angular resolution of the velocity measurement enables the tracking of the entire illuminated body shell, extending the range of future applications of radar-based motion analysis.

Photoacoustic (PA) velocimetry holds the advantage of detecting ultrasound signals from selective targets sensitive to specific wavelengths of light irradiation. In particular, it is expected to be applied for measuring blood flow in microvasculature. However, PA velocimetry has not been sufficiently investigated for small velocity ranges down to several tens of millimeters per second. This study evaluates the performance and uncertainty of PA velocity measurements using a single graphite cylinder (GC) as a moving object. A pair of short laser pulses irradiated the object within a brief time interval. The velocity was measured based on the cross-correlation peak of successive PA signal pairs in the time domain. The limiting measurement uncertainty was 3.4 mm/s, determined by the sampling rate of the digitizer. The object motion was controlled in a sinusoidal linear motion, realized using a loudspeaker. With the PA measurement, the velocity of the object was obtained with a time resolution in milliseconds and with directional discrimination. Notably, the PA velocity measurements successfully provided the local velocities of the object across a wide range, with the reference velocity obtained as the time derivative of the displacement data acquired using a laser displacement sensor (LDS). The PA measurement exhibited uncertainties ranging from 0.86 to 2.1 mm/s for the maximum and minimum velocities during the experiment. The uncertainties are consistent with those in stationary cases, and nearly constant in the investigated velocity range. Furthermore, the PA measurements revealed local fine velocities of the object, which were not resolved by the reference velocities of the LDS measurements. The capability of the PA velocity measurement was found to be advantageous for measurements of objects with dynamic variations in magnitude and direction. [ABSTRACT FROM AUTHOR]

Purpose: This study analyzed the acute mechanical response to three workouts of the day (WOD) protocols in as many repetitions as possible (AMRAP), every minute on the minute (EMOM), and for time (FT) models by quantifying the degree of mechanical fatigue induced by popular resistance exercises in the Cross modalities, front squat (FS), and shoulder press (SP). We also analyzed whether the exercises' fastest velocity (Vfastest) could be an objective indicator of relative intensity (%1RM). Methods: Nine trained men performed three FS and SP exercises protocols. The degree of fatigue was quantified by the velocity loss (VL) achieved in both exercises and the velocity loss achieved in the WOD (VLWOD). Results: The VLWOD in the AMRAP, EMOM, and FT protocols was 73.2 ± 10.9%, 61.6 ± 15.1%, and 76.1 ± 8.8%, respectively. In the AMRAP and FT protocol, the Vfastest showed very strong relationships with the %1RM for FS and SP (r = -0.83, -0.75, respectively, p < .01); while in the EMOM protocol, there was a strong relationship between these variables, only for the SP (r = -0.61, p < .05). In the FT protocol, we observed an extremely strong relationship for FS (r = -0.91, p < .001) and very strong (r = -0.71, p < .05) for SP between these variables. Conclusion: Therefore, the AMRAP and FT training models induce the highest degrees of mechanical fatigue in the FS and SP exercises, and the Vfastest is a reliable tool for estimating relative intensity in resistance exercises of Cross modalities. [ABSTRACT FROM AUTHOR]

This article proposes a measurement method using a multi-dimensional LED detection array, which can be used to obtain the flight parameters (i.e., impact coordinates, flight velocity, and incident angle) of a small flying object. Firstly, the composition of the proposed system and its detection principle are described in detail. Then, a calculation model is derived according to the geometrical relationship between the different LED detection arrays, which can calculate the above flight parameters. Furthermore, numerical simulations are performed to analyze the change trend in the measurement error of the proposed system, and it can be verified that its measurement performance meets the related requirements in theory. Finally, we use the proposed system and a high-speed camera system to carry out comparison experiments with two different reference velocities of 900 m/s and 700 m/s, and the results show that the maximum deviation in the measured absolute velocity is always less than 1 m/s and that the maximum deviations of the measured coordinates of x and y are not more than 2 mm within the effective measurement range. Therefore, the proposed measurement method is feasible and effective, and it can also meet the requirements of the measurement system. [ABSTRACT FROM AUTHOR]

In shockwave experiments, the launch velocity of flyer is a crucial parameter for determining the physical quantities in sample under dynamic compression. Magnet velocity induction system is used to determine the velocity of flyer which can work under hypervelocity conditions. Based on finite element method, ANSYS Electromagnetics Suite module was used to establish a three-dimensional model and the launch process of flyer was simulated. The simulated results well reproduce the experimental signals. Comparing to the experimental results, the relative error of simulated amplitude of induced electromotive force (AIEMF) is 1.1%, lower than the system error of 2.0%. The relative error for flyer velocity determined by simulation is less than 0.4%, also lower than the measurement system error of 0.9%. The dependence of AIEMF with the thickness, radius, tilt angle, launch velocity of flyer and the diameter of pick-up coils is analyzed. The simulation result provides a reference for better signal acquisition in shockwave experiments. [ABSTRACT FROM AUTHOR]

Submerged entry nozzle (SEN) clogging will affect the production efficiency and product quality in the continuous casting process. In this work, the transient SEN clogging model is developed by coupling the porous media model defined by the user-defined function (UDF) and the discrete phase model (DPM). The effects of the transient SEN clogging process on the flow field, the distribution of argon gas bubbles and the fluctuation of the interface between steel and slag in the concave bottom SEN in the continuous casting slab mold with a cross-section of 1500 mm × 230 mm are studied by coupling transient SEN clogging model, DPM and volume of fluid (VOF) model. The results show that the actual morphology and thicknesses of SEN clogging are in good agreement with the numerical simulation results. The measurement result of the surface velocity is consistent with the numerical simulation result. With increasing the simulation time, the degree of SEN clogging increases. The flow velocities of molten steel flowing from the outlet of the side hole increase, because the flow space is occupied with the clogging inclusions, which leads to the increased number of argon gas bubbles near the narrow wall. The steel–slag interface fluctuation near the narrow walls also increases, resulting in the increased risk of slag entrapment.

To improve the global optimization ability and convergence speed of the swarm intelligence algorithm, we proposed a new swarm intelligence optimization algorithm, namely the Oryctolagus cuniculus algorithm. This includes five mechanisms: the determination of safety zones, the cave escape, the agglomeration of Oryctolagus cuniculi, the maintenance of the Oryctolagus cuniculus king, and the zone competition. Each solution is represented by each Oryctolagus cuniculus's position (including zone number and specific location number). The grass density and safety index at the location of the Oryctolagus cuniculus represents its fitness value. The determination of safety zones implies that predators such as eagles hunt Oryctolagus cuniculi in dangerous zones, and the zone without predators is considered a safety zone. The cave escape refers to the act of Oryctolagus cuniculi using a connected cave system to flee from a dangerous zone and reach a secure zone, thereby evading potential predators. We select the Oryctolagus cuniculus with higher fitness values as the king of each zone, and the Oryctolagus cuniculi gather towards the Oryctolagus cuniculus king. This mechanism ensures that Oryctolagus cuniculus mainly searches in zones with abundant grass and quickly finds the optimal solution. In the maintenance of the Oryctolagus cuniculus king, we choose the one with higher fitness values as the Oryctolagus cuniculus king. Zone competition is induced by an increase in the number of Oryctolagus cuniculi in zones with abundant grass by ordering the fitness values of each zone, and vice versa. We apply the Oryctolagus cuniculus algorithm to the inversion method of the asteroid spectra reflectance template. The experimental results show that compared with artificial rabbit optimization, this algorithm has a faster rate of convergence and better solution, effectively screens the reflectance template, and improves the Doppler difference velocimetry accuracy. In addition, the application of the Oryctolagus cuniculus algorithm to the knapsack problem also performs effectively. [ABSTRACT FROM AUTHOR]

The increasingly improved performance of mass-market GNSS chipsets is driving smartphone GNSS positioning or velocimetry as a low-cost GNSS solution for high-precision vibration monitoring applications. In this study, the Android GNSS velocity measurement performance of mass-market smartphones was evaluated. Based on the smartphone GNSS data generated by the Geo + + RINEX Logger, we found smartphone anomalous clock variations, as evidenced by the biases between the TDCP-estimated and Doppler-estimated receiver clock drifts, as well as frequent jumps. As a result, the traditional Doppler and TDCP combination method that estimates the receiver TDCP clock drift as the same parameter as the Doppler clock drift is no longer applicable. To solve this problem, we provide two strategies, including inter-satellite differencing and dual clock drift estimation. The results of static and shake table experiments show that the traditional combination method solutions for smartphones contain many outliers, with the root mean square (RMS) of the horizontal velocity measurement errors exceeding 1 m/s. In contrast, using the inter-satellite differencing and dual clock drift estimation strategies, the velocity error RMS are both reduced to less than 1 cm/s. For a representative Huawei P40 smartphone, their static experimental horizontal velocity error RMS is 0.27 and 0.26 cm/s, respectively, and their mean velocity error RMS of six shaking tests are 0.52 and 0.40 cm/s, respectively. In addition, the causes of this anomalous clock variation are further discussed and the noise characteristics of Android multi-constellation multi-frequency Doppler and TDCP observations are analyzed. These results are encouraging and show that we can obtain a few mm/s velocities using inexpensive smartphones or their embedded GNSS chipsets. In this case, there is a cost-effective solution for implementing a dense network of monitoring arrays or developing low-cost monitoring instruments with integrated GNSS. [ABSTRACT FROM AUTHOR]

Infrared (IR) small dim target detection near the sea–sky line (SSL) is crucial for enhancing the early warning capability of maritime vehicles. However, the interferences caused by the strong contrast have not been properly addressed. Consequently, a specially designed algorithm regional-division local contrast measure (RDLCM) that focuses on the detection of IR small dim targets appearing near the SSL is proposed. First, an SSL detection module based on a lightweight convolutional neural network (CNN) is devised to achieve fast pixel-level SSL detection. Then, a set of regional-division windows (RDWs) are designed according to the strong grayscale contrast distribution around the SSL, and through the division of the effective regions, the RDWs could realize the potential extraction and refinement of the IR small dim targets that appear near the SSL. Experiments on three IR image sequences demonstrate that the proposed algorithm achieves the best detection accuracy among the classical and state-of-the-art algorithms in comparison and runs at 44 frames per second (FPS), which could meet real-time requirements. The code and dataset are available at RDLCM. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To assess the validity of different commercial portable velocity testing devices in strength training by systematic and Meta-analysis method. METHODS: Related articles were searched in Web of Science, PubMed, and CNKI databases. “Appraisal of Study Design for Psychometric Articles” was used as a scale to evaluate the quality of the included studies. In both fixed and random effect models, the Pearson correlated coefficient (r) was aggregated by R language to conduct a Meta-analysis of different types of speed measurement devices. RESULTS: A total of 44 and 16 studies were included for qualitative and quantitative analysis, respectively. The general quality of included studies was moderate. Twenty-six brands of velocity testing devices were involved. Qualitative findings in validity: line position transducers and video-based devices < iPhone APP and accelerators, Smith machine > free weight. Quantitative findings in validity: GymAware had high validity for measuring mean velocity [low intensity: r=0.98, 95% confidence interval (CI): 0.95-0.99; medium intensity: r=0.98, 95% CI: 0.95-0.99; high intensity: r=0.98, 95% CI: 0.96-0.99] and peak velocity (low intensity: r=0.99, 95% CI: 0.97-0.99; medium intensity: r=0.98, 95% CI: 0.97-0.99; high intensity: r=0.95, 95% CI: 0.97-0.99) in free weight, with a positive correlation with the gold standard (P=0.001). Push had poor validity for measuring mean velocity (low intensity: r=0.69, 95% CI: 0.49-0.82; medium intensity: r=0.69, 95% CI: 0.37-0.86; high intensity: r=0.48, 95% CI: 0.21-0.68) and peak velocity (low intensity: r=0.71, 95% CI: 0.52-0.83; medium intensity: r=0.82, 95% CI: 0.69-0.89; high intensity: r=0.68, 95% CI: 0.37-0.85) in free weight, with a positive correlation with the gold standard (P=0.001). CONCLUSION: Existing evidence has confirmed that line position transducer and video-based device have the highest validity, iPhone APP takes the second place, and accelerators are poor in validity. High-valid line position transducers and video-based devices should be applied in velocity-based training rather than accelerators. [ABSTRACT FROM AUTHOR]

Ultrasonic polar scan (UPS) records the amplitude in transmission for a wide range of incidence angles, providing a UPS image with characteristic contours reflecting the acoustic parameters of the material. This study focused on a newly developed wave velocity measurement of the DD6 single-crystal material plate by analyzing the UPS image to realize the ultrasonic thickness measurement of the DD6 single-crystal material plate accordingly. Firstly, considering transducer contour size compensation, the UPS images are obtained by numerical simulation on the DD6 single-crystal material plates with different crystal orientations. Secondly, the fitting equations are obtained by analyzing the UPS images to calculate wave velocity in the thickness direction. Finally, a 5-joint UPS scanner is designed to validate the accuracy of wave velocity simulation results experimentally, and it indicates a good agreement with conventional ultrasonic velocity measurement. The measurement results demonstrated that the UPS method could evaluate the wave velocity in the through-thickness direction of the DD6 single-crystal material plate with high precision.

An integrated interferometric fiber optic velocimetry sensor has been proposed and demonstrated at the central wavelength of 638 nm. The sensor is based on the principle of two laser-beams' interference. The light signal scattered from the particles or vapor is demodulated to measure the water surface velocity and water vapor velocity. Three velocity measurement experiments are carried out to measure the velocity, and the experimental data shows that the velocity increases linearly in the range of 4 mm·s−1 to 100 mm·s−1, with a slope of linear fitting curve of 0.99777 and the R-Square of 1.00000. The velocity calculated from frequency shift fits well with the reference velocity. The maximum average relative error in the three velocity measurements is less than 2.5%. In addition, the maximum speed of 4.398 m·s−1 is confirmed in the rotating disk calibration experiment, which expands the sensor's velocity measurement range. To solve the problem that it is difficult to directly measure the velocity of small-scale water surface flow velocity, especially from the aspect of the low velocity of air-water surface, the interferometric fiber optic sensor can be applied to the measurement of water surface velocity and wind velocity on the water surface. [ABSTRACT FROM AUTHOR]

We have developed a new method for measuring temperature and velocity at a high spatial resolution (minimum 2.56 mm pitch along an optical fiber). The developed method uses the same principle as a hot wire anemometer, where the velocity perpendicular to an optical fiber is estimated as a function of the cooling curve of a gold-coated layer on the optical fiber Joule-heated intermittently. The developed optical fiber sensor demonstrated the ability to acquire a transient velocity profile in airflow experiments with high repeatability and accuracy. This paper describes optical fiber-based velocity measurement in the velocity range of approximately 0–7 m/s with an error of approximately 10% compared to a hot wire anemometer and a new method for simultaneous temperature and velocity measurements. Applicability to velocity distribution measurements and seconds transient velocity changes are also described. [ABSTRACT FROM AUTHOR]

In this paper, based on the principle of charge induction, a new velocity measurement method is proposed. A moving target generates a low-frequency electric field, which can be induced with an electrode and detection frontend. Velocity measurements are achieved by placing two electrodes at a fixed distance to detect the characteristic times. Firstly, the electric field generated by the moving target is modeled, and the theoretical output of the detection frontend is obtained via a simulation of the target passing by a single electrode. Then, according to the theoretical output, the velocity measurement simulation results of double electrodes are given for various driving conditions, such as a single vehicle driving in a single lane, a single vehicle changing lanes, two vehicles driving close together, and a multiple-vehicle situation. Finally, the above driving conditions are experimentally verified in sunny weather, windy and rainy weather, and a night environment. [ABSTRACT FROM AUTHOR]

We developed a signal processing algorithm to determine three components of the velocity vector of a highly maneuverable aircraft. We developed an equation of the distance from an aircraft to an underlying surface. This equation describes a general case of random spatial aircraft positions. Particularly, this equation considers distance changes according to an aircraft flight velocity variation. We also determined the relationship between radial velocity measured within the radiation pattern beam, the signal frequency Doppler shift, and the law of the range changing within the irradiated surface area. The models of the emitted and received signals were substantiated. The proposed equation of the received signal assumes that a reflection occurs not from a point object, but from a spatial area of an underlying surface. It fully corresponds to the real interaction process between an electromagnetic field and surface. The considered solution allowed us to synthesize the optimal algorithm to estimate the current range and three components { V x , V y , V z } of the aircraft's velocity vector V → . In accordance with the synthesized algorithm, we propose a radar structural diagram. The developed radar structural diagram consists of three channels for transmitting and receiving signals. This number of channels is necessary to estimate the full set of the velocity and altitude vector components. We studied several aircraft flight trajectories via simulations. We analyzed straight-line uniform flights; flights with changes in yaw, roll, and attack angles; vertical rises; and landings on a glide path and lining up with the correct yaw, pitch, and roll angles. The simulation results confirmed the correctness of the obtained solution. [ABSTRACT FROM AUTHOR]

• Arrayed fibers and a line scan camera are used for the transmission and acquisition of signals. • The system uses the high line rate of the line scan camera to measure the velocity. • It uses arrayed fibers with known spacing to measure the dimension. • The results are analyzed with digital image processing techniques. This paper presents a laser screen imaging measurement system (LSIMS) based on arrayed fibers to measure the velocity and dimension of a flying object. A laser diode is connected to the emission module of the laser screen via a single-mode fiber, then the emitted light beam is collimated into a parallel beam with a lens, this structure is arrayed to form the laser screen. The receiving module of the laser screen employs a cylindrical lens array to converge the collimated beams into a focal line. The input ends of the plastic fibers are arrayed along this focal line, while the output ends are imaged on the sensor of a line scan camera (LSC) through a lens. The LSIMS effectively modulates the process of a flying object passing through the laser screen into the light intensity change in the plastic fibers. The velocity and dimension of the flying object are subsequently measured through the analysis of the image obtained by the LSC. The timing accuracy of the LSIMS is verified through experiments. The velocity and diameter of pellets launched by a slingshot are measured and analyzed for errors. [ABSTRACT FROM AUTHOR]

Photoacoustic (PA) velocimetry holds the advantage of detecting ultrasound signals from selective targets sensitive to specific wavelengths of light irradiation. In particular, it is expected to be applied for measuring blood flow in microvasculature. However, PA velocimetry has not been sufficiently investigated for small velocity ranges down to several tens of millimeters per second. This study evaluates the performance and uncertainty of PA velocity measurements using a single graphite cylinder (GC) as a moving object. A pair of short laser pulses irradiated the object within a brief time interval. The velocity was measured based on the cross-correlation peak of successive PA signal pairs in the time domain. The limiting measurement uncertainty was 3.4 mm/s, determined by the sampling rate of the digitizer. The object motion was controlled in a sinusoidal linear motion, realized using a loudspeaker. With the PA measurement, the velocity of the object was obtained with a time resolution in milliseconds and with directional discrimination. Notably, the PA velocity measurements successfully provided the local velocities of the object across a wide range, with the reference velocity obtained as the time derivative of the displacement data acquired using a laser displacement sensor (LDS). The PA measurement exhibited uncertainties ranging from 0.86 to 2.1 mm/s for the maximum and minimum velocities during the experiment. The uncertainties are consistent with those in stationary cases, and nearly constant in the investigated velocity range. Furthermore, the PA measurements revealed local fine velocities of the object, which were not resolved by the reference velocities of the LDS measurements. The capability of the PA velocity measurement was found to be advantageous for measurements of objects with dynamic variations in magnitude and direction.

This article proposes a measurement method using a multi-dimensional LED detection array, which can be used to obtain the flight parameters (i.e., impact coordinates, flight velocity, and incident angle) of a small flying object. Firstly, the composition of the proposed system and its detection principle are described in detail. Then, a calculation model is derived according to the geometrical relationship between the different LED detection arrays, which can calculate the above flight parameters. Furthermore, numerical simulations are performed to analyze the change trend in the measurement error of the proposed system, and it can be verified that its measurement performance meets the related requirements in theory. Finally, we use the proposed system and a high-speed camera system to carry out comparison experiments with two different reference velocities of 900 m/s and 700 m/s, and the results show that the maximum deviation in the measured absolute velocity is always less than 1 m/s and that the maximum deviations of the measured coordinates of x and y are not more than 2 mm within the effective measurement range. Therefore, the proposed measurement method is feasible and effective, and it can also meet the requirements of the measurement system.

As an important part of hydrometry, river discharge monitoring plays an irreplaceable role in the planning and management of water resources and is an essential element and necessary means of river management. Due to its benefits of simplicity, efficiency and safety, Space-Time Image Velocimetry (STIV) has attracted attention from all around the world. The most crucial component of the STIV is the detection of the Main Orientation of Texture (MOT), and the precision of detection directly affects the results of calculations. However, due to the complicated river flow characteristics and the harsh testing environment in the field, a large amount of noise and interfering textures show up in the space-time images, which affects the detection results of the MOT. In response to the shortage of noise and interference texture, a new non-contact image analysis method is developed. Firstly, Multi-scale Retinex (MSR) is proposed to pre-process the images for contrast enhancement; secondly, a fourth-order Gaussian derivative steerable filter is employed to enhance the structure of the texture; next, based on the probability density distribution function and the orientations of the enhanced images, the noise suppression function and the orientation-filtering function are designed to filter out the noise to highlight the texture. Finally, the Fourier Maximum Angle Analysis (FMAA) is used to filter out the noise further and obtain the clear orientations to achieve the measurement of velocity and discharge. The experimental results show that, compared with the widely used image velocimetry measurements, the accuracy of our method in the average velocity and flow discharge is significantly improved, and the real-time performance is excellent. [ABSTRACT FROM AUTHOR]

We formulate a physics-informed compressed sensing (PICS) method for the reconstruction of velocity fields from noisy and sparse phase-contrast magnetic resonance signals. The method solves an inverse Navier-Stokes boundary value problem, which permits us to jointly reconstruct and segment the velocity field, and at the same time infer hidden quantities such as the hydrodynamic pressure and the wall shear stress. Using a Bayesian framework, we regularize the problem by introducing a priori information about the unknown parameters in the form of Gaussian random fields. This prior information is updated using the Navier-Stokes problem, an energy-based segmentation functional, and by requiring that the reconstruction is consistent with the $k$ -space signals. We create an algorithm that solves this inverse problem, and test it for noisy and sparse $k$ -space signals of the flow through a converging nozzle. We find that the method is capable of reconstructing and segmenting the velocity fields from sparsely-sampled (15% $k$ -space coverage), low ($\sim 10$) signal-to-noise ratio (SNR) signals, and that the reconstructed velocity field compares well with that derived from fully-sampled (100% $k$ -space coverage) high ($> 40$) SNR signals of the same flow. [ABSTRACT FROM AUTHOR]

Hovering drones use ground control points to measure the surface flow velocity of rivers. This study aims to use only GPS data and images captured by a drone to extract the flowrate at a designated absolute position. Using GPS data, the moving directions of the drone and of the image were calculated, and each image point was converted into a physical UTM (Universal Transverse Mercator) coordinate system. After determining the range of observation by selecting the start and end frames, all images of the measurement cross section were divided into reference frames (measurement subsections), and the flowrate was calculated with spatiotemporal volume obtained by gathering images for 1 sec (30 frames) for all measurement subsections. The results were comparable with those obtained using the existing hovering drone image analysis method. [ABSTRACT FROM AUTHOR]

Currently, the number of vehicles in road traffic is increasing, which enhances the variety of traffic situations and needs related to road traffic and safety. A cooperative intelligent transport system (C-ITS) can improve road safety and benefit drivers and traffic participants. The C-Roads specification defines many different use cases for informing road vehicles about speed limits, impending danger, road work, signalized intersections, and more. In this article, we propose a new use case targeting the need for Integrated Rescue System services to slow down or stop selected vehicles that are violating rules. Unlike most use cases in C-Roads, in our case, it is not enough to only notify the driver’s vehicle; it must also be slowed down or stopped completely. This intervention requires addressing issues from a technical and a procedural/legal point of view. In this work, we define the use case itself, following the templates of the specification in C-Roads. Then, we discuss the issues in terms of secure communication between vehicles and privacy. We also analyze existing protection security techniques against typical cybersecurity attacks and privacy countermeasures. Next, we propose a system architecture concerning appropriate C-ITS messages and communication between vehicles and present an onboard diagnostics simulator implementing the proposed architecture for the core needs of a given use case. Furthermore, we create a practical demonstrator of our proposal based on real vehicle components. Finally, we discuss open research questions and the ongoing development of the use case before the application on the Internet of Vehicles. [ABSTRACT FROM AUTHOR]

River discharge is an essential hydrological index of the global water cycle and is important for flood and drought forecast. Ultrahigh frequency (UHF) radar has gained much attention since it can remotely retrieve river discharge from the surface flow velocity measurement in real-time and all-weather condition. However, it becomes challenging for the mountain river case where the water level changes more significant than that of the plain river due to the deep-narrow channel, which breaks the previous empirical relationship between surface flow velocity and discharge. In this letter, an improved index-velocity method is proposed to address this issue. Through modeling the nonuniform variation of the cross-sectional area with water level, a more accurate surface flow velocity–discharge relationship is established. Experimental results show that the proposed method produces higher calculation accuracy than that of the previous methods, which enlarges the applicable scenario of UHF radar in discharge measurement. [ABSTRACT FROM AUTHOR]

A cooperative radar-communication (RadCom) system architecture employing a multiport interferometer receiver is introduced and demonstrated for low-power and low-cost multifunction wireless applications. The proposed system operates in both radar sensing and radio communication modes, which are arranged in different time slots within a single hardware platform. In the radar sensing cycle, a triangular frequency-modulated continuous-wave (FMCW) scheme is adopted for distance and velocity measurements. The radio cycle following the radar sensing cycle is used to communicate beat frequency information among different measurement stations for a cooperative radar operation, which can also be used for other data transmissions. The interferometric receiver for a unified multifunction operation benefits from the cooperative approach as it does not require a receiver front-end with a high dynamic range. The receiver architecture also makes use of a balanced detection scheme to suppress the frequency mixing components generated between radar echoes and cooperative radar responses, which eliminates undesired interferences and false targets as well as to enhance the signal quality. A mathematical model of the proposed sensing system is derived to design and implement the system for operation in a multistation environment. The system performance consisting of two stations in a low microwave frequency band has been established and evaluated for both modes with several experiments. In radar sensing mode, the distance and velocity measurements demonstrate the target finding capability of our proposed system. In radio mode, the demodulation of various digitally modulated signals has been successfully studied at different data rates. [ABSTRACT FROM AUTHOR]

Aiming at the problem that the unbalanced vibration of a high-speed magnetically suspended rotor affects the attitude angular velocity measurement accuracy of magnetically suspended control and sensitive gyroscope (MSCSG), a multifrequency vibration suppression method based on adaptive multifrequency estimation (AMFE) is proposed. First, the reason of rotor mass unbalance vibration is analyzed, the dynamic model of MSCSG with unbalance vibration is established, and its influence on spacecraft attitude angular velocity measurement accuracy is pointed out. The multifrequency vibration suppression controller and the compensation module of residual synchronous displacement stiffness force are designed when the rotor speed is unknown. The measurement signal of the radial ${X}$ -channel displacement sensor and its orthogonal signal are used to realize the estimation of the rotor speed. Finally, the convergence of the AMFE algorithm and the stability of the system are analyzed. The simulation and experimental results show that the proposed method can effectively suppress harmonic currents and residual synchronous displacement stiffness disturbance force caused by mass imbalance. The method proposed in this article can effectively improve the attitude angular velocity measurement accuracy of MSCSG. [ABSTRACT FROM AUTHOR]

In this work, we propose a novel deep learning reconstruction framework for rapid and accurate reconstruction of 4D flow MRI data. Reconstruction is performed on a slice-by-slice basis by reducing artifacts in zero-filled reconstructed complex images obtained from undersampled k-space. A deep residual attention network FlowRAU-Net is proposed, trained separately for each encoding direction with 2D complex image slices extracted from complex 4D images at each temporal frame and slice position. The network was trained and tested on 4D flow MRI data of aortic valvular flow in 18 human subjects. Performance of the reconstructions was measured in terms of image quality, 3-D velocity vector accuracy, and accuracy in hemodynamic parameters. Reconstruction performance was measured for three different k-space undersamplings and compared with one state of the art compressed sensing reconstruction method and three deep learning-based reconstruction methods. The proposed method outperforms state of the art methods in all performance measures for all three different k-space undersamplings. Hemodynamic parameters such as blood flow rate and peak velocity from the proposed technique show good agreement with reference flow parameters. Visualization of the reconstructed image and velocity magnitude also shows excellent agreement with the fully sampled reference dataset. Moreover, the proposed method is computationally fast. Total 4D flow data (including all slices in space and time) for a subject can be reconstructed in 69 seconds on a single GPU. Although the proposed method has been applied to 4D flow MRI of aortic valvular flows, given a sufficient number of training samples, it should be applicable to other arterial flows. [ABSTRACT FROM AUTHOR]

Different models have been used to evaluate the interfacial Dzyaloshinskii–Moriya interaction (DMI) from the asymmetric bubble expansion method using magneto-optics. Here, we investigate the most promising candidates over a range of different magnetic multilayers with perpendicular anisotropy. Models based on the standard creep hypothesis are not able to reproduce the domain wall (DW) velocity profile when the DW roughness is high. Our results demonstrate that the DW roughness and the interface roughness of the sample layers are correlated. Furthermore, we give guidance on how to obtain reliable results for the DMI value with this popular method. A comparison of the results with Brillouin light scattering (BLS) measurements on the same samples shows that the BLS approach often results in higher measured values of DMI. [ABSTRACT FROM AUTHOR]

This article presents a design methodology and prototyping of an angular speed sensor based on microwave polarimetry. The detection mechanism relies on the transmission response of a dual-polarized circular aperture irradiating an array of regularly spaced copper traces printed on a PCB. The generated response is a regular pulse train defined by the location of the copper trace with reference to the center of the circular aperture. While the angular speed sensor can be sampled at any rate and for any time length, the detector response was acquired within a 1-s duration with the circular aperture response effectively sampled at 10 kHz for demonstration purposes. The acquired response was analyzed in the frequency domain using the fast Fourier transform (FFT) and the rotor speed was obtained from the frequency spectrum of the acquired pulse train. To demonstrate the working principle of the detection system, the printed PCB rotor, which occupies an area of 84.64 cm2, was attached to a rotary stage set to rotate at certain angular speeds, including but not limited to 62 r/min. In all the speed settings, the speeds were detected in 1 s with a worst case error of ±0.625 r/min. [ABSTRACT FROM AUTHOR]

The measurement of river discharge is essential for sustainable water resource management. The velocity–area approach is the most common method for calculating river discharge. Although several velocity measurement methods exist, they often have varying degrees of technical issues attributed to their operational complexity, time effectiveness, accuracy, and environmental impact. To address these issues, we propose a three-dimensional (3D) hydrodynamic model coupled with data assimilation (DA) for velocity measurement with improved accuracy and efficiency. We then apply this model to the Lanxi River reach in Zhejiang Province, China. The experimental results confirm that the obtained assimilated velocities using our proposed algorithm are much closer to the observed velocities than the simulated velocities. Our results show that when using the proposed method, the RMSE is decreased by 78%, and the SKILL and DASS values are 0.96 and 0.92, respectively. These confirm that the DA scheme of the flow velocity measurement is effective and capable of significantly improving the accuracy of the velocity with lower computational complexity. [ABSTRACT FROM AUTHOR]

The calibration of scale factor and installation errors plays an essential role to improve the accuracy of integrated navigation system of strap-down inertial navigation system (SINS) and Doppler velocity log (DVL). The DVL measurements will be affected by complex underwater environment, which may affect the calibration results. To solve the above problems, a Global Navigation Satellite System (GNSS) aided separate calibration method for DVL error is proposed in this article. First, an iterative method based on adaptive weight is proposed to calculate the scale factor. Second, a vector observation model is established and the method optimal-REQUEST is introduced to calculate the misalignment angles. In order to improve the estimation accuracy, a vector reconstruction method based on robust filtering is designed according to the measurement variation characteristics of parameter model to reduce the influence of thick tail noise. Finally, the simulation and Yangzi River experiments are conducted to evaluate the feasibility of the proposed DVL calibration method. Experimental results show that the proposed method has a good effect on the calibration of DVL error when DVL measurements are disturbed by noise. Compared to the combined calibration method based on state estimation, iterative method has no need to establish the system noise model, and the estimation result is relatively stable. The river results show that the proposed method is efficient and the positioning result has been greatly improved after calibration. [ABSTRACT FROM AUTHOR]

This article presents the novel structure of an eddy current sensor for linear speed measurements. The sensor has one excitation coil and two pairs of antiserially connected pick-up coils, which are located inside and outside the excitation coil. The design and modeling of the sensor are considered with an air core and with a magnetic yoke (core) to compare their performances in terms of sensitivity and nonlinearity error. The experiments and the analysis are performed at different excitation frequencies and speeds. A novel three-dimensional analytical method is developed and utilized for parametric analysis and for the design of this sensor. The simulation results are compared with measurements up to 16.7 m/s (60 km/h). The achieved nonlinearity error is as low as 0.3%. [ABSTRACT FROM AUTHOR]

As the higher order or generalized extended state observer (ESO), generalized proportional-integral (GPI) observer (GPIO) haves been proposed to enhance the active disturbance rejection (ADR) control (ADRC) system's disturbance rejection ability. However, different ADR controllers can be deduced based on the same order GPIO, resulting in different dynamic performances. In this article, ten different ADR controllers based on the fourth order GPIO are present. In order to reveal the relationship between these ADR controllers and the conventional ADR controllers based on the third order ESO, six different third-order-ESO-based ADR controllers are present and compared with the fourth-order-ESO-based ADR controllers. To ease the comparison between different ADRC systems, a common expression is built for different ADR controllers. A novel frequency-domain analysis method is also introduced to reveal how the observer and feedback control law affects the closed-loop control system's dynamic performance. The effectiveness of the proposed method is verified on the test bench based on dSPACE DS1103. [ABSTRACT FROM AUTHOR]