[Design of acoustic radiation force module for ultrasound elastography].

Developing an acoustic radiation force excitation module including 64 channels based in FPGA for ultrasound elastography. The circuit of the module was derived in bipolar, and the parameters such as excitation frequency, pulse repetition frequency, pulse number, element number and focus depth were adjustable. The acoustic field for special parameter was experimented with OptiSon laser acoustic field system with a result which reflects the width of focal spot is about 3 mm. The acoustic power was experimented with RFB2000 radiation force balance with a result which reflects acoustic power is increasing linearly with the number of pulses and the number of elements, and is increasing squarely with the peak-to-peak value of excitation voltage. The module is promising in factual application which can be triggered externally in synchronously, and can be combined with B-mode ultrasound system for ultrasound elastography.

Numerical Simulation and Experimental Investigation of Laser Ablation of Al2O3 Ceramic Coating.

This paper presents an evaluation of the molten pool laser damage done to an Al2O3 ceramic coating. Mechanism analysis of the laser damage allowed for a 2D finite element model of laser ablation of the Al2O3 ceramic coating to be built. It consisted of heat transfer, laminar flow, and a solid mechanics module with the level set method. Results showed that the laser damage mechanisms through laser ablation were melting, gasification, spattering, and micro-cracking. The ablation depth and diameter increased with the increasing laser ablation time under continuous irradiation. The simulation profile was consistent with the experimental one. Additionally, the stress produced by the laser ablation was 3500-9000 MPa, which exceeded the tensile stress (350-500 MPa), and fracturing and micro-cracks occurred. Laser damage analysis was performed via COMSOL Multiphysics to predict laser damage morphology, and validate the 3D surface profiler and scanning electron microscope results.

Research on laser-assisted selective metallization of a 3D printed ceramic surface.

In recent years, the question of how to fabricate conductive patterns on complex ceramic surfaces in a high-definition and low-cost manner has been an increasing challenge. This paper presents a complete process chain for the selective metallization of Al2O3 ceramic surfaces based on 3D printing. Laser pre-activation (LPA) is used to "activate" the surface of the ceramic substrate, and then, combined with the electroless copper plating (ECP) process, the Al2O3 substrates can be metalized with preset patterns at room temperature, and a densely packed copper layer with high accuracy and good reproducibility can be obtained. The obtained coating has satisfactory roughness, excellent stability and bonding force, and good solderability. The resistivity of the copper layer measured using a four-probe resistance meter is about 3.1 mΩ cm. The limit line width of the metal circuit is about 33.2 µm. Finally, application cases of precision devices such as antennas with ceramic substrates are prepared. This study opens up a broader space for the design and manufacture of 3D microwave devices.

Continuous detection of muscle aspect ratio using keypoint tracking in ultrasonography.

Muscle aspect ratio of cross-sectional area is one of the most widely used parameters for quantifying muscle function in both diagnosis and rehabilitation assessment. Ultrasound imaging has been frequently used to noninvasively study the characteristics of human muscles as a reliable method. However, the aspect ratio measurement is traditionally conducted by the manual digitization of reference points; thus, it is subjective, time-consuming, and prone to errors. In this paper, a novel method is proposed to continuously detect the muscle aspect ratio. Two keypoint pairs are manually digitized on the lateral and longitudinal borders at the first frame, and automatically tracked by an optical flow technique at the subsequent frames. The muscle aspect ratio is thereby obtained based on the estimated muscle width and thickness. Six ultrasound sequences from different subjects are used to evaluate this method, and the overall coefficient of multiple correlation of the results between manual and proposed methods is 0.97 ± 0.02. The linear regression shows that a good linear correlation between the results of the two methods is obtained (R(2) = 0.974), with difference -0.01 ± 0.16. The method proposed here provides an accurate, high repeatable, and efficient approach for estimating muscle aspect ratio during human motion, thus justifying its application in biological sciences.