Indirect Velocity Measurements Research Articles

Particle filter-based modulation domain infrared targets tracking

Faced with problems of low contrast, poor SNR, and relatively complicated tracking environment, stable infrared target tracking is worth researching for its many potential applications. In this paper, instead of traditional target tracking in the pixel domain, we propose a sampling importance resampling (SIR) particle filter method with indirect velocity measurements to track infrared targets in the modulation domain. The dominant amplitude modulation (AM) features used for tracking is extracted by decomposing the input image using an 18-channel Gabor filter bank followed by the application of the dominant component analysis approach. The dominant AM modulation features provide a significant partial texture characteristic of the target which can be separated from background with better discrimination. To take advantage of observed kinematics, we utilize the augmented state vector with indirect velocity information via combining the measurements of velocity in adjacent frames to the SIR particle filter framework, which weakens weights of particles with bad velocity estimates but still having association with the cluttered background or other moving objects. A dynamic template update strategy is also provided to prevent the tracker from appearance model drift. Experiments indicate that the proposed method is effective for raising the tracking accuracy compared with other tracking methods.

Indirect Velocity Measurement from Standing Waves in Rockbed Rivers

Direct measurement of velocities and discharge in turbulent rockbed rivers is dangerous and often impracticable. Float measurements of surface velocity in sediment-free rockbed reaches of rivers are used to test the equation—due to Kennedy—that the mean velocity of a critical wave train is given by v= 1.2495√λ, where λ is the wavelength of the standing waves. Field data collected for wavelengths between 0.5 m and 7 m estimates surface velocity as about 2% significantly higher than the predicted mean velocity. It is concluded that the Kennedy equation successfully represents the mean velocity in rockbed rivers, which are essentially free from sediment, and that measuring the wavelengths of standing wave trains is an accurate and economical method of measuring mean velocity in the field. From estimated wave train width and computed critical depth, minimum discharge can be estimated for the section.

On the method of indirectly measuring gas and particulate phase velocities in shock induced dusty-gas flows

A method of indirectly measuring the temporally varying velocities of the gas and particulate phases in the nonequilibrium region of a shock wave moving at constant speed in a dusty-gas flow is described, and this method is assessed by using experimental data from shock-induced air flows containing 40-μm-diameter glass beads in a dusty-gas shock-tube facility featuring a large horizontal channel (19.7-cm by 7.6-cm in cross-section). Simultaneous measurements of the shock-front speed with time-of-arrival gauges, particle concentration by light extinctiometry and gas-particle mixture density by beta-ray absorption are used in conjunction with two mass conservation laws to obtain the indirect velocity measurements of both phases. A second indirect measurement of the gas-phase velocity is obtained when the gas pressure is simultaneously recorded along with the particle concentration and shock-front speed when used in conjunction with the conservation of mixture momentum. Direct measurements of the particulate-phase velocity by laser-Doppler velocimetry are also presented, as a means of assessing the indirect velocity measurement method.

An indirect method of measuring gas- and particulate-phase velocities of shock-induced dusty-gas flows

A method of indirectly measuring the temporally varying velocities of both the particulate and gas phases in the nonequilibrium region of a shock wave moving at constant speed in a dusty-gas mixture is described. This method is implemented by using experimental data from shock-induced air flows containing glass beads 40 μm in diameter in a dusty-gas shock-tube facility featuring a large horizontal channel 197 mm high by 76 mm wide with a special dust-injection device. Simultaneous measurements of the shock-front speed with time-of-arrival gauges, particulate concentration by light extinctiometry, and combined particulate concentration and gas density by beta-ray absorption are used in conjunction with two mass conservation laws to provide these indirect two-phase velocity measurements. Direct measurements of the particulate-phase velocity by laser-Doppler velocimetry are also presented for comparison, and the capability of the indirect velocity-measurement method is assessed.