A new method uses a linear array that takes advantage of underwater physical sound fields to estimate the velocity of an underwater moving target. The mathematical model was established by considering the geometric re...A new method uses a linear array that takes advantage of underwater physical sound fields to estimate the velocity of an underwater moving target. The mathematical model was established by considering the geometric relationship between the moving target installed with only two transducers to radiate sound of different frequencies and the linear array. In addition, deterministic maximum likelihood and signal phase matching algorithms were introduced to effectively find the directions of arrival （DOAs） of the sound sources of the two transducers installed on the target. Factors causing velocity measurement errors were considered. To track the target, a linear array with a compass, a pressure transducer, a signal conditioner and a digital recorder was configured. Relevant requirements for the array parameters were derived. The simulation showed that a 16-element array with an aperture of less than lm can measure velocity with relative error of no more＇, than 4% when including typical system errors. Anechoic pool and reservoir experiments confirmed these results.展开更多
The activation of multisite high-entropy alloy(HEA)electrocatalysts is helpful for improving the atomic utilization of each metal in water electrolysis catalysis.Herein,well-dispersed HEA nanocrystals on Nrich graphen...The activation of multisite high-entropy alloy(HEA)electrocatalysts is helpful for improving the atomic utilization of each metal in water electrolysis catalysis.Herein,well-dispersed HEA nanocrystals on Nrich graphene with abundant M–pyridinic N–C bonds were synthesized through an ultrasonic-assisted confinement synthesis method.Operando Raman analysis and density functional theory calculations revealed that the electrocatalysts presented the optimal electronic rearrangement with fast ratedetermined H_(2)O dissociation kinetics and favorable H^(*)adsorption behavior that greatly enhanced hydrogen generation in alkaline electrolyte.A small overpotential of only 138.6 mV was required to obtain the current density of 100 mA cm^(-2) and the Tafel slope of as low as 33.0 mV dec^(-1),which was considerably smaller than the overpotentials of the counterpart with poor M–pyridinic N–C bonds(290.4 mV)and commercial Pt/C electrocatalysts(168.6 mV).The atomic structure,coordination environment,and electronic structure were clarified.This work provides a new avenue toward activating HEA as advanced electrocatalysts and promotes the research on HEA for energy-related electrolysis.展开更多
基金Supported by the National Science Foundation of China under Grant No.60672136
文摘A new method uses a linear array that takes advantage of underwater physical sound fields to estimate the velocity of an underwater moving target. The mathematical model was established by considering the geometric relationship between the moving target installed with only two transducers to radiate sound of different frequencies and the linear array. In addition, deterministic maximum likelihood and signal phase matching algorithms were introduced to effectively find the directions of arrival （DOAs） of the sound sources of the two transducers installed on the target. Factors causing velocity measurement errors were considered. To track the target, a linear array with a compass, a pressure transducer, a signal conditioner and a digital recorder was configured. Relevant requirements for the array parameters were derived. The simulation showed that a 16-element array with an aperture of less than lm can measure velocity with relative error of no more＇, than 4% when including typical system errors. Anechoic pool and reservoir experiments confirmed these results.
基金supported by the National Natural Science Foundation of China(21838003,51621002)the Innovation Program of Shanghai Municipal Education Commissionthe Fundamental Research Funds for the Central Universities。
文摘The activation of multisite high-entropy alloy(HEA)electrocatalysts is helpful for improving the atomic utilization of each metal in water electrolysis catalysis.Herein,well-dispersed HEA nanocrystals on Nrich graphene with abundant M–pyridinic N–C bonds were synthesized through an ultrasonic-assisted confinement synthesis method.Operando Raman analysis and density functional theory calculations revealed that the electrocatalysts presented the optimal electronic rearrangement with fast ratedetermined H_(2)O dissociation kinetics and favorable H^(*)adsorption behavior that greatly enhanced hydrogen generation in alkaline electrolyte.A small overpotential of only 138.6 mV was required to obtain the current density of 100 mA cm^(-2) and the Tafel slope of as low as 33.0 mV dec^(-1),which was considerably smaller than the overpotentials of the counterpart with poor M–pyridinic N–C bonds(290.4 mV)and commercial Pt/C electrocatalysts(168.6 mV).The atomic structure,coordination environment,and electronic structure were clarified.This work provides a new avenue toward activating HEA as advanced electrocatalysts and promotes the research on HEA for energy-related electrolysis.
