基于STM32的回声测深仪模拟检定装置研究

针对回声测深仪校准的需求,设计了一种以STM32为核心处理器的模拟检定装置系统.充分利用STM32单片机具有72MHz主频及多定时器的功能,对采集到的回声测深仪信号进行计数和定时处理,最终得到精确的延时时间后的回波信号.该系统主要包括有脉冲计数单元,定时处理单元、回波发生及发送单元等.经试验验证,本系统可以精确的模拟测深仪所测水深,完全可以满足我们对测深仪校准的要求.

Energy-optimal trajectory planning for solar-powered aircraft using soft actor-critic

High-Altitude Long-Endurance(HALE)solar-powered Unmanned Aircraft Vehicles(UAVs)can utilize solar energy as power source and maintain extremely long cruise endurance,which has attracted extensive attentions from researchers.Trajectory optimization is a promising way to achieve superior flight time because of the finite solar energy absorbed in a day.In this work,a method of trajectory optimization and guidance for HALE solar-powered aircraft based on a Reinforcement Learning(RL)framework is introduced.According to flight and environment information,a neural network controller outputs commands of thrust,attack angle,and bank angle to realize an autonomous flight based on energy maximization.The validity of the proposed method was evaluated in a 5-km radius area in simulation,and results have shown that after one day-night cycle,the battery energy of the RL-controller was improved by 31%and 17%compared with those of a Steady-State(SS)strategy with a constant speed and a constant altitude and a kind of statemachine strategy,respectively.In addition,results of an uninterrupted flight test have shown that the endurance of the RL controller was longer than those of the control cases.

Vernier effect of fiber interferometer based on cascaded PANDA polarization maintaining fiber

This Letter shows the Vernier effect based on two segments of PANDA polarization maintaining fiber(PMF),whose lengths are 28 and 23 cm, respectively. The two PMFs are spliced together, and the angle between the fast axes is set to 45°. This cascaded PMF is inserted in a Sagnac loop to form an interferometer that can generate the Vernier effect. The spectrum consists of finesse fringe and envelope and realizes simultaneous measurement of strain and temperature. The envelope can provide strain and temperature sensitivities of 58.0 pm/με and -1.05 nm/℃. The finesse fringe provides sensitivities of 5.9 pm/με and -1.36 nm/℃.

Singlet relaxation dynamics and long triplet lifetimes of thiophene-coupled perylene diimides dyads:New insights for high efficiency organic solar cells

In the active layer of organic solar cells(OSCs),the lifetime of triplet excitons is one of the decisive factors in the diffusion length and therefore has important impact on the power conversion efficiency of the devices.Herein,we have investigated singlet excited state relaxation dynamics and their triplet exciton lifetimes of two thiophene-coupled perylene diimides(PDI)dyads(2 PDI-Th and fused-2 PDI-Th),in order to provide a unique explanation in depth on their different performances in OSC devices.From the transient absorption(TA)spectra,the singlet excitons of 2 PDI-Th form excimers in the time scale of 1.5 ps.Then the excimers go into the triplet state via intersystem crossing(ISC).In fused-2 PDI-Th,triplet excitons are generated directly from the singlet excited excitons via the efficient ISC.Density functional theory(DFT)calculations further support the formation of excimers.DFT results indicate that 2 PDI-Th exhibits an H-typed molecular configuration which is beneficial to form the excimers,while fused-2 PDITh gives a twisted X-shaped configuration in the optimized ground and excited state.In steady-state emission spectra,2 PDI-Th shows abroad and featureless spectral characteristics of the excimers with a decay time of 840 ps,which is much shorter than those of PDI(5.5 ns)and fused-2 PDI-Th(3.3 ns).The triplet lifetime(67 ms)of fused-2 PDI-Th is factor of 3 longer than that of 2 PDI-Th(22 ms).These results demonstrate that ring-fused structure is an efficient strategy to eliminate excimer formation and prolong the lifetime of triplet excitons,which provides a new insight for design of optoelectronic molecules for high efficiency organic solar cells.

Real-time dynamics of soliton triplets in fiber lasers

The evolution of soliton molecules emphasizes the complex soliton dynamics akin to matter molecules.Beyond the simplest soliton molecule-a soliton pair constituted by two bound pulses-soliton molecules with more constituents have more degrees of freedom because of the temporal pulse separations and relative phases.Here we detailedly characterize the transient dynamics of soliton triplets in fiber lasers by using the dispersive Fourier transform measurement.A particular form of leading,central,and tailing pulses is constructed to shed new light on more intriguing scenarios and fuel the molecular analogy.Especially the vibrating dynamics of the central and tailing pulses are captured near the regime of equally spaced soliton triplets,which is reminiscent of the recurrent timing jitters within multi-pulse structures.Further insights enable acess into a universal form of unequally spaced soliton triplets interpreted as 2+1 soliton molecules.Different binding strengths of intramo-lecular and intermolecular bonds are validated with respect to the diverse internal motions involved in this soliton triplet molcule.All these findings unveil the transient dynamics with more degrees of freedom as well as highlight the possible application for all-optical bit storage.