Analysis and Design of Four-Plate Capacitive Wireless Power Transfer System for Undersea Applications

This paper presents a four-plate undersea capacitive wireless power transfer(CPT)system for underwater applications such as autonomous underwater vehicles(AUVs).Generally,a CPT system transfers the power based on electric fields.The complex resonant compensation networks are used to make the CPT system work in the resonant condition.The resonant voltage is always very high.It will be a big challenge to the human safety.In this paper,a virtual electrons periodic reciprocating flow theory is proposed for the CPT system.In one switching cycle,the electrons firstly flow in the forward direction through the forward path and then flow in the inverse direction through the inverse path.The CPT system has been deeply studied with the vacuum dielectric or the air dielectric.However,for the CPT system,there are few papers to show the underwater application.In this paper,an undersea four-plate CPT system is designed and studied in the underwater condition.The two coupling capacitors and other elements of the CPT system could build a closed-loop path.A small value inductor is adapted as a resonant compensation network for the four-plate CPT system.The DC voltage is inverted to the AC voltage in the primary side with the single-phase full-bridge inverter.The resonant voltage is rectified to the DC voltage in the secondary side with the single-phase full-bridge diode rectifier.A 100 W power level CPT system is constructed to verify the theory analysis and the calculation.The theory analysis is verified by the simulated and experimental results.The stable output voltage and load power are achieved in this paper.

A method of multichannel chaotic phase modulation spread spectrum and its application in underwater acoustic communication

Direct-sequence spread spectrum （DSSS） communication possesses low probability of detection and has been widely used in confidential communications. However, pseudo-noise （PN） sequences, used as spreading code in conventional DSSS communications, possess peri- odic character and binary value. In hostile environments, these distinct characters may lead to some important parameters of signals being estimated accurately, and then lead to the leakage of transmitted information. To solve the problem, we propose the chaotic phase modulation （CPM） sequence alternating the PN sequences. CPM sequence has complex values and constant envelope, and also possesses large quantity and good correlation characteristics. Moreover, it has more hidden features than conventional sequences by modulating its phases using chaotic sequence. To improve the data rate, we apply it into the technique of multichannel communica-tion. Simulation results show this scheme＇s superior bit error ratio （BER） performance, which demonstrates its feasibility in underwater acoustic communications.

Extraction and application of the low dimensional dynamical component from underwater acoustic target radiating noise

Signal processing in phase space based on nonlinear dynamics theory is a new method for underwater acoustic signal processing. One key problem when analyzing actual acoustic signal in phase space is how to reduce the noise and lower the embedding dimen- sion. In this paper, local-geometric-projection method is applied to obtain fow dimensional element from various target radiating noise and the derived phase portraits show obviously low dimensional attractors. Furthermore, attractor dimension and cross prediction error are used for classification. It concludes that combining these features representing the geometric and dynamical properties respectively shows effects in target classification.

Application and measurement of underwater acoustic reciprocity transfer functions in reverberant sound field

The reciprocity measurement theory in anomalous reverberant sound fields was investigated.An improved method Was proposed due to the interrelated errors.The source volume velocity Was corrected by spatial average of measurement results and evaluation of the reverberant sound field influence on acoustic energy density.The result was validated in underwater experiment,corrected reciprocity measurement results were almost the same as direct measurement results.It indicates that reverberant sound field does not affect the validitv of the principle,but influences the obtainment of source volume velocity,then influences the measurement of transfer functions with the principle.The proposed method is simple and effective in anomalous reverberant sound fields.The study mav be valuable for the applications which are based on the principle.

Matrix-Mediated Color-Tunable Ultralong Organic Room Temperature Phosphorescence of 7H-Benzo[c]carbazole Derivatives

Building on the recent systematic research on 1Hbenzo[f]indole(Bd),an important advancement in constructing ultralong organic room temperature(UORTP)materials with a universal strategy via a readily obtained unit(7H-Benzo[c]carbazole,BCz)is proposed in this work.Pure powders of BCz and its derivatives merely exhibit blue fluorescence at ambient condition.However,when BCz and its derivatives are dispersed into polymer or powder matrixes,strong photo-activated green UORTP can be observed from their doped systems at room temperature.Moreover,the UORTP color can be tuned between green and yellow depending on the matrix.The ultralong phosphorescence originates from the generation of charge-separated states via radicals.The matrixes play a key role in both stabilizing charge-separated states and controlling UORTP color.More interestingly,when using polymethyl methacrylate as matrix,the doped films achieve stronger photo-activated ultralong phosphorescence underwater than in air at room temperature.Comparedwith Bd,BCz achieves better performance not only in ultralong phosphorescence properties but also in practical applications.This work gains a deeper insight into the mechanism of UORTP and paves a new approach to applying organic phosphorescent materials to underwater coating and imaging.

Temperature-sensitive and solvent-resistance hydrogel sensor for ambulatory signal acquisition in“moist/hot environment”

To realize continuously and stably work in a“moist/hot environment”,flexible electronics with excellent humid resistance,antiswelling,and detection sensitivity are demanding.Herein,a solvent-resistant and temperature-ultrasensitive hydrogel sensor was prepared by combining MXene and quaternized chitosan(QCS)with the binary polymer chain.The strong electrostatic interaction between the QCS chain and the poly(acrylic acid)(PAA)network endows the hydrogel stability against solvent erosion,high temperature,and high humidity.The strong dynamic interaction between MXene and polymer matrix significantly improves the mechanical properties and sensing(strain and temperature)sensitivity of the hydrogel.The hydrogel strain sensor exhibits a high gauge factor(5.53),temperature/humidity tolerance(equilibrium swelling ratio of 2.5%at 80℃),and excellent cycle stability,which could achieve a remote and accurate perception of complex human motion and environment fluctuation under aquatic conditions.Moreover,the hydrogel sensor exhibits impressive thermal response sensitivity(-3.183%/℃),ultrashort response time(<2.53 s),and a low detection limit(<0.5℃)in a wide temperature range,which is applied as an indicator of the body surface and ambient temperature.In short,this study broadens the application scenarios of hydrogels in persistent extreme thermal and wet environments.

Bioinspired wet-resistant organogel for highly sensitive mechanical perception

Smart flexible electronics with underwater motion detection have become a promising research aspect in intelligent perception.Inspired by the strong adaptability of marine creatures to complex underwater environments,conventional biocompatible hydrogels are worth developing into organogels with preferred underwater adhesive properties,hydrophobic and antiswelling performance,and motion perception ability.Herein,a highly sensitive organogel sensor exhibiting good hydrophobicity,electromechanical properties,and adhesion properties was prepared for underwater utilization by regulating the chemical components and internal interactions.The synergistic effect of massive reversible noncovalent bonds ensures the organogel’s excellent underwater adhesion to multifarious substrates.Meanwhile,the interactions of hydrophobic conductive fillers and the dynamic hydrophobic associations in the organogel endow it with satisfactory hydrophobic performance(contact angle of111.8°)and antiswelling property(equilibrium swelling ratio of-31%after 15-day immersion).The fabricated flexible organogel strain sensor exhibits high sensitivity(gauge factor of1.96),ultrafast response rate(79.1 ms),low limit of detection(0.45 Pa),and excellent cyclic stability(1044 tensile cycles followed by 3981 compressive cycles).Results demonstrate the proposed organogel’s precise perception of sophisticated human motions in air and underwater,which expands its application scenarios.