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Chromium carbide (Cr3C2), as a kind of transition metal carbides, has exhibited extraordinary optoelectronic properties and aroused enormous attention. However, few reports have been focused on the nonlinear properties and relevant devices. In this study, we first demonstrated a novel Cr3C2 saturable absorber (SA). Cr3C2 with an average size of 200 nm was prepared through a low temperature salt flux synthetic method. The Cr3C2-film SA exhibited high robustness and strong linear and nonlinear saturable absorption response at 1560 nm. As the Cr3C2 SA was inserted into the Er3+-doped fiber laser cavity, Q-switched pulses were generated with a central wavelength of 1560 nm. To the best of our knowledge, this was the first report on the optical nonlinearity of Cr3C2 as a Q-switcher for the near-infrared fiber laser. Our experimental results verified that the integrated Cr3C2-based device possessed great potential as a nonlinear optical medium for high-performance optical applications.

Aiming at the trajectory planning and compliance of the one-legged hop of a quadruped robot, a method for designing the optimal trajectory of the bouncing by minimizing the jerk index is proposed, and active compliance control is used to reduce the impact of the end of the foot and improve the compliance of the one-legged. First, design a one-legged bounce strategy. The bounce is divided into three phases: take-off phase, vacant phase, and buffer phase, and trajectory optimization is performed for each phase. Secondly, a compliance control method is designed. During the bouncing process, the impact of the foot end is large, which will affect the stability of the robot and even destroy the mechanical structure of the leg. The joint level adopts force-position mixed control, and the one-legged level adopts impedance control to eliminate the impact of ground impact on one-legged. Finally, a one-legged model of a quadruped robot was established in the Vortex multi-body dynamics system. Simulation experiments have proved the feasibility of trajectory optimization and compliance control.

During the launch tests of a Multiple Launch Rocket System (MLRS), the front metal seal covers on unlaunched tubes had plastic deformation and felled to the ground. More seriously, the rocket exhausted jet directly caused damage to some of the unlaunched rockets projectiles. As the rocket exhausted jet impinged on the cover, high temperature and high pressure jet caused plastic deformation of the covers. So the temperature and pressure of exhausted jet acting on the surface of the cover were measured. Then pressure data were used to estimate the strain of front cover on adjacent launch tube caused only by pressure. And temperature data were used for thermal stress analysis of the cover. Furthermore, the triaxial strain curves of the cover were obtained during a flight test in which a 252-mm diameter rocket projectile was launched from the MLRS. The results demonstrated that plastic deformation of the covers is mainly due to the thermal deformation caused by the high temperature, which provided guidance for optimal design of front seal covers. No plastic deformation was found in the modified covers during subsequent launch tests of the MLRS.

Due to its special climate and geological reasons, Tianjin Binhai area has formed a large area of saline-alkali land. It is of great significance to explore the distribution of salt ions in crops under drip irrigation conditions. In this paper, maize was used as the research object, and different irrigation amount treatment was set up to study the distribution of Na+ and K+ in corn under drip irrigation conditions, and the transport selectivity of corn to Na+ and K+ was analyzed. The results show that the Na+ absorbed by corn is mainly distributed in roots and K+ is mainly distributed in stems and leaves; the transport selectivity coefficient decreases with the increase of irrigation amount, and the increase of Na+/K+ value is the improvement of salt tolerance of corn when irrigation amount is small. Corn can inhibit the transport of Na+ to the ground by enhancing the transport of K+ and reduce the damage to corn.

Effects of heat treatment on microstrucutures of a Re-containing single crystal superalloy have been investigated. The results showed that (γ+γ′) eutectic in as-cast alloy is practically dissolved with solution heat treatment, and the degree of segregation is distinctly decreased. The size, morphology and distribution of γ′ phase are mightily affected by the first-stage ageing treatment temperature. When the first-stage ageing treatment temperature lower than 1160°C, the shape of the γ′ phase is cubic. But the γ′ phase shape is transformed to sphericity when the temperature higher than 1180°C. The γ phase channel width is significantly increased, and the fine γ′ phase precipitated in the γ phase matrix channel.

This paper presents an overview of mechanical properties and constitutive law for wood. Current research on the mechanical properties of wood have mostly focused on density, grain, moisture, and other natural factors. It has been established that high density, dense grain, and high moisture lead to higher strength. In most literature, wood has been regarded as an anisotropic material because of its fiber. A microscopic view is used in research of wood today, in this way, which has allowed for clear observation of anisotropy. In general, wood has higher strength under a dynamic load, and no densification. The constitutive model is the basis of numerical analysis. An anisotropic model of porous and composite materials has been used for wood, but results were poor, and new constitutions have been introduced. According to the literature, there is no single theory that is widely accepted for the dynamic load. Research has shown that grain and moisture are key factors in wood strength, but there has not been enough study on dynamic loads so far. Hill law has been the most common method of simulation. Models that consider high strain rate are attracting more and more attention.