Oriented amorphous fraction in biaxially oriented poly(vinylidene fluoride) gives it significantly enhanced dielectric and ferroelectric properties.

Hydraulic engineering built in the cold region, such as reservoirs and hydropower stations, is often threatened by static ice pressure from nature. Therefore, it is of vital significance to research the pressure variation in the growth and melting processes of the ice layer for the design and protection of hydraulic structures in cold regions. This paper introduces an optical fiber sensor system based on the fiber loop ring-down spectroscopy technology and field-programmable gate array (FPGA) pulse modulation technology. An electro-optic modulation scheme that relied on FPGA to generate optical pulses with adjustable pulse width and period is proposed, which is more suitable for the in-situ observation. In addition, the temperature stability and repeatability of the system are also discussed. This system was applied to the real-time detection of static ice pressure on the sidewall and bottom of the polyvinyl chloride (PVC) pipe during the ice growth and melting processes. The results indicate that the system has favorable stability and sensitivity, and the relationship obtained between the static ice pressure and temperature could provide some references for the field application in the future.

Inland waterways play an important role in the transportation of goods and passengers. But maneuvering vessels in this type of restricted area can be challenging due to the limited maneuverability and the presence of obstacles. Hence, these areas can be abstracted as constrained surfaces. The dynamic window approach (DWA) is a path planning strategy for real-time navigation in constrained environments that considers dynamic constraints. While the pivot point concept is a useful technique which analyze the spot that vessels rotate around. Concerning these two concepts, this paper proposes a real-time local path planning algorithm named retrofitted dynamic window approach (RDWA) for maneuvering inland vessels on constrained surfaces. The algorithm retrofitted the DWA to satisfy the control behavior constraints stemming from the limited maneuverability. Further, the pivot point technique is leveraged to enable the vessel to pivot around desired points. The algorithm is evaluated by simulations, which demonstrate the approach can pivot the vessel around a number of pre-defined points for more than 90 degrees and form an arc motion trajectory in less than three minutes.