In this research, a hybrid approach for path planning of autonomous ships that generates both global and local paths, respectively, is proposed. The global path is obtained via an improved artificial potential field (APF) method, which makes up for the shortcoming that the typical APF method easily falls into a local minimum. A modified velocity obstacle (VO) method that incorporates the closest point of approach (CPA) model and the International Regulations for Preventing Collisions at Sea (COLREGS), based on the typical VO method, can be used to get the local path. The contribution of this research is two-fold: (1) improvement of the typical APF and VO methods, making up for previous shortcomings, and integrated COLREGS rules and good seamanship, making the paths obtained more in line with navigation practice; (2) the research included global and local path planning, considering both the safety and maneuverability of the ship in the process of avoiding collision, and studied the whole process of avoiding collision in a relatively entirely way. A case study was then conducted to test the proposed approach in different situations. The results indicate that the proposed approach can find both global and local paths to avoid the target ship.

In a recent study, we have reported that there are many novel cuts of quartz crystal exhibiting the highly treasured cubic frequency-temperature relations which are currently shown only with the AT-and SC-cut. Through setting the first-and second-order derivatives of the frequency respect to temperature to zeroes, a family of quartz crystal cuts with different temperatures of zero frequency (turnover temperatures) has been found and examined. It is now possible to fabricate quartz crystal resonators with turnover temperature near its operating temperature to keep the resonator functioning in a lean and more natural state. By selecting a few cuts based on orientations from our study, we analyzed the thickness-shear vibrations of quartz crystal plates to confirm the superior frequency-temperature relations with the theory of incremental thermal field and Mindlin plate equations and presenting comparisons with known AT-and SC-cut to demonstrate that resonators with newly found cuts can also achieve exceptional frequency stability as demanded.