In the seawater desalination system, the energy recovery system is a crucial part, as it consumes a lot of energy and plays a guiding role in the recovery efficiency. Therefore, in the energy recovery system, the recovery rate and energy consumption are the key factors to guide the system design. In order to make the energy recovery device achieve a high recovery rate under conditions of low energy consumption, the design and selection of each device in the system are particularly important. At the current stage, system matching optimization, device design optimization, and function objective optimization are widely used to improve the energy recovery system. In this paper, the design principle of the energy recovery integration system is analyzed, methods of reducing energy consumption and improving recovery efficiency are presented. The study provides guidance for the design and selection of energy recovery devices under different operating conditions.

The deep-sea environment has the characteristics of high pressure and low temperature. In addition to the extremely high requirements on the structural reliability, the ultra-high ambient pressure also has a great impact on the working characteristics of the hydraulic source. In this paper, the efficiency characteristics of a deep-sea hydraulic source are studied in the full-ocean-depth pressure range. According to the power transfer process, the efficiency of the deep-sea motor, gear pump and hydraulic circuit is analyzed. In so doing, the oil friction loss of the motor rotor, the internal leakage of the gear pump, the viscous friction loss of the hydraulic system, etc., are calculated. Then, simulating the deep-sea high-pressure environment by the pressure cylinder, the output characteristics and corresponding input power of the prototype are measured. By analyzing the experimental data, the efficiency characteristic curve of the hydraulic source prototype, changing with the ambient pressure, is obtained. The experimental and calculation results show that, with the increase of ambient pressure, the system efficiency of the hydraulic source prototype increases first and then decreases.

The ability of unmanned surface vehicles (USV) on motion control and the accurate following of preset paths is the embodiment of its autonomy and intelligence, while there is extensive room for improvement when expanding its application scenarios. In this paper, a model fusion of USV and preset path was carried out through the Serret-Frenet coordinate system. Control strategies were then scrupulously designed with the help of Lyapunov stability theory, including resultant velocity control in the presence of drift angle, course control based on the nonlinear backstepping method, and reference point velocity control as a virtual control variable. Specifically, based on USV resultant velocity control, this paper proposes respective solutions for two common scenarios through velocity planning. In a derailment correction scenario, an adaptive reference velocity was designed according to the position and attitude of USV, which promoted its maneuverability remarkably. In a dynamic obstacle avoidance scenario, an appropriate velocity curve was searched by dynamic programming on ST graph and optimized by quadratic programming, which enabled USV to evade obstacles without changing the original path. Simulation results proved the convergence and reliability of the motion control strategies and path following algorithm. Furthermore, velocity planning was verified to perform effectively in both scenarios.

The primary objective of this article is to present a semi-analytical algorithm for the transient behaviors of Functionally Graded Materials plates (FGM plates) considering both the influence of in-plane displacements and the influence of temperature changes. Based on the classical plate theory considering the effect of in-plane displacements, the equilibrium equations of the motion system are derived by Hamilton’s principle. Here, we propose a novel, accurate, and efficient semi-analytical method that incorporates the Fourier series expansion, the Laplace transforms, and its numerical inversion and the Differential Quadrature Method (DQM) to simulate the transient behaviors. This paper validates the proposed method by comparisons with semi-analytical natural frequency results and those from the literature. Expressly, the results of dynamic response also agree well with those generated by the Navier’s method and Finite Element Method (FEM). A convergence study that utilizes the different numbers of sampling points shows that the process can converge quickly, and a few sampling points can achieve high accuracy. The effects of various boundary conditions at the ends, material graded index, and temperature change are further investigated. From the detailed parametric study, it is seen that the peak displacement increases as the edge degrees of freedom, the gradient index of the material, and temperature change increase.

This paper gives the quantitative relationship between prediction error and given past sample size in our research of sea level time series. The present result exhibits that the prediction error of sea level time series in terms of given past sample size follows decayed power functions, providing a quantitative guideline for the quality control of sea level prediction.