When a high-power laser beam is incident on water, the rapid heat transfer process triggers ionization of the water in the
active region, resulting in an explosion as well as outward propagating shock waves. Here, the formation, propagation, and
interaction of underwater shock waves induced by nanosecond laser pulses were experimentally investigated. By fitting
the theoretical model (Sedov-Taylor expansion model) to the experimental results, we quantified the effective energy
carried by the shock wave during propagation. Numerical simulations with an analytic model using the distance between
adjacent breakdown locations as input obtain the shock wave emission images at different time delays and provide insights
into experimentally not accessible shock wave parameters. An empirical model is used to describe the pressure behind the
shock wave. The results show the near-acoustic propagation behavior of the shock waves at longer time delays. On top of
that, we compared the effect of the distance between adjacent excitation positions on the shock wave emission process.
The shock wave parameters in the far field are more accurate and easier to perform. Furthermore, utilizing multipoint
excitation offers a flexible approach to delve deeper into the physical mechanisms that cause optical tissue damage in
nanosecond laser surgery, leading to a better comprehension of the subject.
To study the influence of laser intensity and temperature on the performance of laser power converters (LPCs), a two-dimensional model of an In0.3Ga0.7As LPC by the finite element method was established. The validity of the model was verified by comparing the theoretical value with the experimental results. The factors that influence the performance of LPCs were analyzed from the perspective of recombination. Results indicate that the existence of grids at the front surface improves the collection of carriers efficiently, and the influence of temperature and laser intensity on carriers recombination is quite different at 0 and Vm (voltage at maximum power point) bias voltages. The research of this paper provides a reference for the optimization of LPCs.
The morphology of high-voltage cable sealing layer has an important impact on the sealing characteristics. Aiming at the measurement problem of high-voltage cable sealing layer morphology, this paper uses a lattice laser to irradiate the target to form a laser lattice on the surface of the target, and then obtains the target image with a binocular polarization camera. The polarized light is used to overcome the influence of metal reflected flare, and then a pair of target images are matched. Then the parallax of each point is calculated. Finally, these points are used to reconstruct the point cloud to obtain the three-dimensional(3D) shape of lead sealing layer. The method in this paper provides a method for the measurement of the 3D shape of lead sealing layer, which is of great significance for the quality control of lead sealing layer.
Lead has good corrosion resistance and sealing property, which is often used in cable lead sealing process and various processes. In the production process, there may be small defects in the lead products, which may affect the quality of the products. Therefore, it is of great economic significance to inspect them to ensure their reliability. Due to the variety of lead products, the use of traditional ultrasonic detection is limited, and laser ultrasound has the ability to detect all kinds of surface samples. However, when the inner defect size of lead products is submillimeter or smaller, the echo signal-to-noise ratio(SNR) is low, so the traditional laser ultrasonic technology is difficult to locate the defects. In this paper, the synthetic aperture focusing (SAFT) technology is applied to the laser ultrasonic detection of lead internal defects. The minimum defect identification ability and resolution ability of laser ultrasonic combined with SAFT are studied, which provides reference for practical application.
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