Passive Stabilization Method Research Articles

Analysis of the Passive Stabilization Methods of Optical Frequency Comb in Ultrashort-Pulse Erbium-Doped Fiber Lasers

In this review paper, we describe the current state of the art to stabilize the output radiation of ultrashort-pulse (USP) fiber lasers and analyze passive methods to reduce the magnitude of fluctuations in the amplitude–frequency noise of output radiation. Regarding main noise characterization in mode-locked fiber lasers, we further consider the influence on laser operation of primary generation regimes starting up in cavities, such as solitons, stretched pulses, similaritons, and dissipative solitons. Then, we proceed to analyze the external and internal factors that affect the stability of the output radiation characteristics depending on the mode-locking mechanism and the resonator scheme.

Reaction-Wheel-Based Roll Stabilization for a Robotic Fish Using Neural Network Sliding Mode Control

The intrinsically reciprocating motion in fishlike propulsion causes severe attitude instability of a robotic fish, which poses enormous challenges for environmental perception and autonomous operation. To address this issue, in this article, we propose a reaction-wheel-based control framework for guaranteeing the roll stability of the robotic fish. The mechatronic design and dynamic model of the designed robotic fish with an internal rotor are presented. By means of the simplified model and frequency domain analysis, the effect factors about roll stability are concretely analyzed. More importantly, a hybrid controller that combines a sliding mode controller with a neural network feedforward compensator is developed to reject the severe disturbance on roll angle. Then, the Lyapunov stability theory is utilized to analyze the stability and convergence property of the closed-loop system. Finally, the experimental results show that the proposed methods possess more significant performances than the passive stabilization method, which provides a valuable reference for attitude stabilization control and robust environmental perception of underwater robots.

Stable radio frequency dissemination-based on passive method by avoiding second harmonic distortion

A stable radio frequency passive stabilization method is proposed over the optical fiber. Different from the traditional schemes, a higher-frequency precompensated signal of 4f is retransmitted. This method can avoid the distortion of second harmonics resulting from modulation and mixing. Therefore, the stability of the system is enhanced. In the simulation scheme, instabilities of the recovered signal at remote station (50 km) are 7.1 × 10 − 14 / s and 2.0 × 10 − 18 / 104 s.

Evaluation of uniform delivery of colloidal nano-Silica stabilizer to liquefiable silty sands

Liquefaction is one of the most important and complex topics in geotechnical earthquake engineering. In recent years, passive site stabilization method has been proposed for non-disruptive mitigation of liquefaction risk at developed sites susceptible to liquefaction using colloidal nano-silica stabilizer. In this research, 4 box models were used to investigate the ability to uniformly deliver colloidal nano-silica stabilizer to liquefiable loose mixes of sand with variations in silt content from 0 to 30% using 5 low-head injection and 2 extraction wells. After delivery was completed the models were cured for 30 days. Then the treated soil was excavated and a few samples were extracted for dynamic loading testing. According to the results, colloidal silica can be delivered uniformly in silty sand formations. With the same conditions, the amount of fine grained soil (silt content) strongly affected delivery time. The passive stabilization method can be appropriate for deposits with up to 20% fine graded silt, a concentration of 5 wt% colloidal silica is expected to be able to effectively mitigate the liquefaction risk of these deposits. The strains during seismic cyclic loading will probably be less than 3% and little permanent strain should result.