The transverse pumping geometry simplifies the laser system design by separating pump and laser beams and providing space for multiple diode laser pump sources with poor beam quality. A transverse pumping double-pass model for metastable rare gas lasers is presented in this paper, in which some intra-cavity information can be obtained. The comparison with Yang’s longitudinally pumped calculation results demonstrated the validity of our model. Several important factors having influence on optical conversion efficiency are simulated and discussed. Simulation of the effects of the required plasma size in transverse pumping model shows that a small size of $0.3\mathrm{cm}\times 10\mathrm{cm}\times 10\mathrm{cm}$ is capable of emitting 9 kW with an optical conversion efficiency over 55% and a megawatt-class output would only need an active medium of several liters if the metastable atoms concentration reaches $3\times {10}^{13}{\mathrm{cm}}^{-3}$.

As a difficult-to-machine material widely used in the aerospace industry, the high-quality and efficient cutting of titanium alloys has been a hot issue in the field of machining. This work performed electric-pulse-assisted turning (EPT) and conventional turning (CT) for Ti5Al4Mo6V2Nb1Fe (TC27) alloy with two kinds of cutters. The results showed that electric pulses significantly improved the machining performance and surface finish quality. With the help of the electric pulse, the cutting force of TiAlN-coated cemented carbide insert (CCI) and uncoated carbide insert (UCI) tools during turning was reduced by more than 20%, and the surface roughness decreased by about 30% with a root mean square of the current density of 0.9 A/mm², because the larger current led to a more obvious electro-plasticity effect. Compared with CT, the surface microhardness of the EPT samples processed with different current densities decreased; this is because the hardened surface was softened by both thermal and athermal effects under the continuous pulse current. However, the microhardness of the EPT samples was still higher than the matrix. At the same time, EPT reduces the wear of the cutting tool, thus helping to extend the tool’s service life. Finally, the electric pulse parameters recommended to assist turning are as follows: an electro-pulsing frequency of 600 Hz, a root mean square of the current density in the cross-section of 0.57 A/mm², and a lasting time of the current per circle of 100 μs.

This study investigated the effect of laser shock peening (LSP) treatment on the fatigue performance of Q355D steel butt-welded joints. The results demonstrate that LSP sig-nificantly enhances joint fatigue resistance through gradient hardening in surface lay-ers, introduction of high-magnitude residual compressive stress fields, and micro-structural refinement. Specifically, microhardness increased across all joint zones with gradient attenuation of strengthening effects within an approximately 700 μm depth. LSP effectively suppressed residual tensile stress concentration in regions beyond 4 mm on both sides of the weld. Fatigue tests confirmed that LSP substantially extended joint fatigue life: by 113–165% in the high-stress region (250–270 MPa) and 46–63% in the medium-low-stress region (230–240 MPa). Fractographic analysis further revealed reduced fatigue striation spacing and lower microcrack density in LSP-treated speci-mens, reflecting the synergistic effect of residual compressive stress fields and micro-structural refinement in retarding crack propagation. This work substantiates LSP as an effective method for enhancing fatigue resistance in Q355D steel welded joints.

To effectively improve the properties of a mullite coating and its interfacial bonding with the substrate, a Ni–P layer is deposited on the surface of mullite powders by electroless plating. The original mullite powders and coated mullite powders are then deposited onto stainless-steel substrates by plasma spraying. The growth mechanism of the Ni–P layer during the plating, the microstructures of the coated powders and mullite coating and the properties of the mullite coatings are characterized and analyzed. The results indicate that the Ni–P layer on the surface of the mullite powder has cell structures with a dense uniform distribution and grows in layers on the surface of the mullite powder. The crystallization behavior of Ni-P amorphous layer is induced by heat treatment. Compared to the original mullite coating, the coating prepared by the coated mullite powders has better manufacturability, stronger adhesion to the substrate, lower porosity (7.40%, 65% of that of the original coating), higher hardness (500.1 HV, 1.2 times that of the original coating), and better thermal cycle resistance (two times that of the original coating). The method of preparation of high-temperature thermal barrier coatings with coated mullite powders has a high application value.

The metastable rare gas atoms are used as lasing species for optically-pumped rare gas laser (OPRGL), which are mainly produced by electrical discharge. Radio-frequency (RF) capacitive discharge is a promising technique for the continued production of the large volume needed for OPRGL systems. In this work, we examined the feasibility of using a RF discharge to produce a continuous gain medium with a gain volume of 4 cm ³ . Metastable argon atoms were measured using tunable Ti: sapphire laser absorption spectroscopy. Simulations of an $\alpha-$ mode RF discharge are performed for varying mixtures of argon and helium using a one-dimensional model. The model is validated qualitatively and quantitatively by measurement in many aspects. The measured and simulated results indicated that the metastable densities decrease with the pressure and reach a peak as the Ar-fraction increases. The model predicted a 35 times increase in peak power with respect to the continuous wave power by use of the cavity dumping technique.