Reliability Of Velocity Measurements Research Articles

Validity and reliability of velocity measurements on ultrasonography using custom software with an optical-flow algorithm.

[Purpose] The purposes of this study were: 1) to validate a commercial software program using an optical-flow algorithm to measure the velocity of muscle movement; and 2) to determine optimal image quality and the size and location of regions of interest. [Materials and Methods] First, a block of pork thigh muscle was pulled at 33 different constant velocities. Subsequently, an accelerometer, a high-velocity camera, and ultrasonography were used to obtain measurements, and an Echolizer software was used to determine ultrasound-based velocities. Finally, the impact of the location and size of the regions of interest and the brightness and contrast of the images was analyzed. [Results] The regression equation was expressed as y=1.150 × −0.071 with a determination coefficient of 0.996. The average absolute error of the software was 0.02 mm/s, and the average relative error was 0.20% of the actual velocity between 2.5 and 16.5 mm/s after the regression equation was applied to the measured data. The accuracy of measurement was reduced owing to the increased size of the regions of interest, which included poor image quality or a deeper zone. [Conclusion] Our method of measuring muscle velocity using a custom program showed high validity and reliability. It is necessary to use the regression equation in the program to improve accuracy. However, the validity of the method could be reduced if the regions of interest involve deep tissues or areas with poor visualization of the muscle bundles, or if the brightness and contrast of the image are set inaccurately.

CFD study on flow approach angle of a bi-directional velocity probe for fire testing

The present study examines the flow characteristics near the bi-directional velocity probe and estimates the probe constant associated with the Reynolds number and flow approach angle. A series of numerical experiments using CFX model are conducted to simulate the 3D flow field near the probe. The CFD model was validated with the best fit polynominal of the experimental data of McCaffrey and Heskestad. The calculated probe constants for a Reynolds number higher than 3000 are almost constant at 1.07 and match well with the conventionally-accepted asymptotic value of 1.08. Using the validated numerical code, a series of parameter studies were conducted. The angular sensitivity of the bi-directional probe increases when increasing the flow approach angle from 0 to 30 degrees, and the maximum angular sensitivity was observed near the flow approach angle of 30 degree. Based on the detailed analysis of flow structure, the present study shows that the pressure at the rear hole of the probe is more affected by the flow approach angle and influenced by the asymmetric wake flow behind the probe body. It is expected that this study can contribute to enhancing the reliability of velocity measurement in fire testing and be utilized as a preliminary study for design optimization of the bi-directional probe based on the understanding of detailed flow characteristics.

Eddy current sensor based velocity and distance estimation in rail vehicles

The precise localisation of rail vehicles is fundamental to the development and employment of more efficient train control systems in security, logistics and disposition applications. A key element of this is the exact and reliable velocity and distance estimation. The popular satellite navigation (global navigation satellite systems) and visual odometry, based on optical systems, tend to fail in the rough environment of rail application scenarios. This study describes an approach to making a precise distance estimate using an innovative eddy current sensor system. This is achieved through the combination of an augmented cross-correlation approach to highly accurate velocity estimation. That is subsequently employed to determine the travelled distance based on counting rail clamps in a spatial transformed space. This approach relies on recursive state estimation of the dynamic states and a statistical assessment of the counted rail clamps for the purpose of outlier rejection. The proposed methods are compared and evaluated in a quantitative way on the basis of experimental data. The results prove that the proposed approach can improve the accuracy and reliability of velocity measurement and relative position detection.

Comparative Study of Power-Based Versus Mean Frequency-Based Transcranial Color-Coded Duplex Sonography in Normal Adults

Power-based transcranial color-coded duplex sonography (p-TCCD) is a new ultrasonic method that has advantages compared with frequency-based TCCD (f-TCCD), since it is essentially independent of the angle of insonation, not subject to aliasing, and has a better signal-to-noise ratio. The purpose of this study was to evaluate the ability of p-TCCD to visualize flow in cerebral parenchyma and to compare the advantages, limitations, and reliability of velocity measurements of p-TCCD versus f-TCCD in the major basal cerebral arteries of normal subjects. Two investigators performed 15 p-TCCD and 15 f-TCCD studies in 30 normal subjects with adequate ultrasonic windows. Each investigator did a p-TCCD or f-TCCD study in every patient, and each was blinded in every case to the results of the other. Peak systolic (Vs) and end-diastolic (Vd) velocities were determined in the anterior, middle, and posterior cerebral, basilar, and vertebral arteries. The reliability of p-TCCD velocimetry was evaluated by calculating both the correlation coefficient (r) of the difference between p-TCCD versus f-TCCD measurements and the coefficient of variation (CV), defined as the difference between the mean values for p-TCCD and f-TCCD divided by the mean values for f-TCCD measurements, expressed as percent. p-TCCD did not display flow in cerebral parenchyma but depicted arteries with a course perpendicular to that of the ultrasound beam and showed good reliability of velocity measurements in all examined arteries: for Vs, r was .84 to .93 (P < .001) and CV was 7.7% to 10.8%; for Vd, r was .87 to .90 (P < .001) and CV was 10.3% to 13.7%. The lack of directional and velocity information and tissue motion artifacts were unimportant limitations in p-TCCD. Compared with f-TCCD, p-TCCD had no important advantages but had several unimportant limitations in a study of normal adults with adequate ultrasonic windows.

Comment on "Reliability of Velocity Measurement by MTD Radar"

Comment on "Reliability of Velocity Measurement by MTD Radar"

Reliability of Velocity Measurement by MTD Radar

For an ATC radar with MTD-type of signal processing, admissible PRF stagger ratios for expanding the unambiguous velocity interval are derived, and formulas and curves for the parameters describing the reliability of velocity information, based on simulation, are presented. In a noise-only environment and for a Swerling 1 target with S/N resulting in Pd = 90 percent, there is a probability of > 50 percent of obtaining velocity information with an expanded unambiguous velocity interval of 832 knots and a standard deviation of < 1 knot. The probability of false measurement is < 10-5.

The role of seismic refraction data for studies of the origin and evolution of continental rifts

Universal attributes of continental rift systems are crustal extension with associated asthenospheric upwelling or modification of the mantle beneath the rift axis. Continental rifting is thus greatly controlled, if not driven, by geodynamic processes in the lower lithosphere. Seismic refraction profiling is a technique for obtaining high-resolution data on structures, seismic velocities, and petrologic conditions in the deep crust and upper mantle. Status of presently available seismic refraction data in four major Cenozoic continental rift systems (Rhinegraben of central Europe, Rio Grande rift of southwestern United States, Baikal rift of Eastern Siberia, and Kenya rift of East Africa) is reviewed in the light of extent of coverage in area and depth, reliability of velocity measurements, and outstanding structural and geodynamical problems that remain unanswered for each system. Evidence of crustal thinning, anomalous mantle at the Moho, as well as shallow and midcrustal velocity anomalies exist in all four examples. The Rhinegraben is the best constrained system from the point of view of seismic structure models. Seismic refraction structure data for the Kenya rift are sparse and raise more questions than answers. Since extensive geological, volcanological, and petrological data available for the East Africa system usually make it the standard for models of continental rifting, modern, high-resolution, deep seismic refraction profiles in Kenya are urgently needed in order to advance understanding of basic continental rifting processes.