Dynamic nonlinearity errors in laser Doppler vibrometer measurements induced by environmental vibration and error correction.

Laser Doppler vibrometers (LDVs) are widely used for vibration testing in various fields. Nonlinearity errors are the key factor affecting the measurement accuracy of LDVs. The conventional Heydemann method cannot correct nonlinearity errors produced by noisy environments. Thus, we establish a novel model to describe dynamic nonlinearity errors produced in noisy environments and propose a compensation method to mitigate signal distortion. The performance of the proposed method is assessed by performing both simulations and experiments. The results of experiments carried out in a noisy environment indicate that the proposed method suppresses the nonlinearity to 30 nm compared to 737 nm using the conventional Heydemann correction. The proposed method can improve the accuracy of LDV measurements in industrial environments.

Thoracic aortic computed tomography angiography in swine: establishment of a baseline for endovascular evaluation of the ascending aorta.

OBJECTIVES: Our goal was to establish a baseline of computed tomography (CT) angiographic data for the porcine ascending thoracic aorta for endovascular evaluation of animal experiments and device development. METHODS: Thoracic aortic CT angiography was conducted on 49 pigs with an average body weight of 60-65 kg. The CT angiographic scans were done on an imaging reconstruction workstation to obtain the specific aortic geometric data, including the diameters of the planes, the heights among the planes and the clock positions of target arteries. RESULTS: Fourteen important planes were defined in the study for endograft customizing reference. The diameters of the planes were measured, and the heights among the planes were recorded. For endograft fenestrations, the right coronary artery ostium clock position was 100.11 ± 7.29°, and the brachiocephalic trunk ostium clock position was 74.72 ± 6.45°. The best projection angle of the tangent position of the left coronary artery was the right anterior oblique 17 ± 7° position. A pig with a rare congenital giant dilated aorta was found among the candidate experimental animals. CONCLUSIONS: For experimental porcine models, CT angiography has proved to be a suitable imaging technique. The established baseline angiography of the swine can provide reference values for future animal experiments and device development.

Dynamics of partially obstructed breakup of bubbles in microfluidic Y-junctions.

For revealing the dynamics of partially obstructed breakup of bubbles in microfluidic Y-junctions, the combination of dimensionless power-law and geometric model was applied to study the effects of capillary number, bubble length, and channel angle on the bubble rupture process. In the squeezing process, the gas-liquid interface curve follows the parabolic model. For the evolution of the bubble neck during breakup, the increase of the bubble length, the channel angle, and the capillary number leads to the decrease of the focus distance α. The chord m increases with the increase of the capillary number and the decrease of the bubble length, and it would reach the maximum value when the channel angle is 90°. In the fast pinch-off stage during bubble breakup, the bubble's neck curve no longer conforms to the parabolic model so the focus and chord no longer exist. For the evolution of the bubble head during breakup, the value of γ approaches 1 with the increase of the capillary number and the bubble length, and with the close of the channel angle to 90°. It is found that the quadrilateral model can be applied for the partially obstructed rupture of bubbles in the symmetrical microfluidic Y-junction.