The theory of passive localization for underwater sources based on acoustic ray channel modeling is discussed. The principles of channel modeling in Ray-theory, determination of eigenrays which connect source and rece...The theory of passive localization for underwater sources based on acoustic ray channel modeling is discussed. The principles of channel modeling in Ray-theory, determination of eigenrays which connect source and receiver, analysis of DOA arriving structure and time delay spectrum arriving structure, their relationship to source location are given in the paper. Source location is estimated by matching measured DOA and TDS to their calculated counterparts. The method of Ray-theory based passive localization features its simplicity, less calculation, short array aperture and robust performance to environment parameters, as compared with those methods based on Normal Mode theory.展开更多
The corrosion behaviour of 316L and Alloy 625 was investigated using cyclic polarization,electrochemical impedance spectroscopy,X-ray photoelectron spectroscopy,Auger electron spectroscopy and induced coupled plasma-o...The corrosion behaviour of 316L and Alloy 625 was investigated using cyclic polarization,electrochemical impedance spectroscopy,X-ray photoelectron spectroscopy,Auger electron spectroscopy and induced coupled plasma-optical emis sion spectrometer.The results indicated that Alloy 625 showed better corrosion resistance than 316L and the prolonging immersion time could enhance corrosion resistance of the two alloys.The passive film formed on the surface of 316L exhibited an electronic structure of p-p heterojunction,with Fe3O4 and Cr2O3 enriched in the outer and inner layers,respectively.However,Alloy 625 presented the electronic structure of n-p heterojunction dominated by the outer Fe2O3/NiFe2O4 and inner Cr2O3.This resulted in the opposite semiconductive properties of the passive films formed on the two materials.In the acid solutions,Fe and Mo suffered from selective dissolution while Cr and Ni were relatively stable.The corrosion rates were mainly dominated by the dissolution of iron.Alloy 625 presented better corrosion resistance than 316L due to the obviously lower content of Fe and the higher content of Cr and Ni in the passive film.The continuously selective dissolution of iron resulted in the increase in Cr/Fe ratio in the passive film,which was responsible for the enhancement in corrosion resistance.展开更多
The semi-conductive performances of hot growth film on 316L stainless steel were studied by means of electrochemical impedance spectroscopy（EIS） and Mott-Schottky analysis.The chemical compositions of the hot growth...The semi-conductive performances of hot growth film on 316L stainless steel were studied by means of electrochemical impedance spectroscopy（EIS） and Mott-Schottky analysis.The chemical compositions of the hot growth films were detected by X-ray photoelectron spectroscopy（XPS）.The results show that the transfer resistance and film resistance increase with increasing temperature to 400℃,then they decrease sharply with further continuously increasing temperature.Formation time plays an important role in determining the electron properties of the hot growth film,when formation time reaches to 1 d,the transfer resistance and film resistance reach to the maximum value.Hot growth film has better anticorrosion behaviour in bicarbonate/carbonate solution containing chloride ions or sulfide ions.Mott-Schottky analysis reveals that hot growth film has n-p type semi-conductive property.XPS results show that the hot growth film is mainly composed of the inner chromium oxide and the outer iron oxide.展开更多
文摘The theory of passive localization for underwater sources based on acoustic ray channel modeling is discussed. The principles of channel modeling in Ray-theory, determination of eigenrays which connect source and receiver, analysis of DOA arriving structure and time delay spectrum arriving structure, their relationship to source location are given in the paper. Source location is estimated by matching measured DOA and TDS to their calculated counterparts. The method of Ray-theory based passive localization features its simplicity, less calculation, short array aperture and robust performance to environment parameters, as compared with those methods based on Normal Mode theory.
基金financially supported by the Fundamental Research Funds for the Central Universities (No.FRFIC-18-007)the China Postdoctoral Science Foundation(No. 2019M650487).
文摘The corrosion behaviour of 316L and Alloy 625 was investigated using cyclic polarization,electrochemical impedance spectroscopy,X-ray photoelectron spectroscopy,Auger electron spectroscopy and induced coupled plasma-optical emis sion spectrometer.The results indicated that Alloy 625 showed better corrosion resistance than 316L and the prolonging immersion time could enhance corrosion resistance of the two alloys.The passive film formed on the surface of 316L exhibited an electronic structure of p-p heterojunction,with Fe3O4 and Cr2O3 enriched in the outer and inner layers,respectively.However,Alloy 625 presented the electronic structure of n-p heterojunction dominated by the outer Fe2O3/NiFe2O4 and inner Cr2O3.This resulted in the opposite semiconductive properties of the passive films formed on the two materials.In the acid solutions,Fe and Mo suffered from selective dissolution while Cr and Ni were relatively stable.The corrosion rates were mainly dominated by the dissolution of iron.Alloy 625 presented better corrosion resistance than 316L due to the obviously lower content of Fe and the higher content of Cr and Ni in the passive film.The continuously selective dissolution of iron resulted in the increase in Cr/Fe ratio in the passive film,which was responsible for the enhancement in corrosion resistance.
基金Supported by the National Basic Research Program of China(No.2007CB707702)
文摘The semi-conductive performances of hot growth film on 316L stainless steel were studied by means of electrochemical impedance spectroscopy（EIS） and Mott-Schottky analysis.The chemical compositions of the hot growth films were detected by X-ray photoelectron spectroscopy（XPS）.The results show that the transfer resistance and film resistance increase with increasing temperature to 400℃,then they decrease sharply with further continuously increasing temperature.Formation time plays an important role in determining the electron properties of the hot growth film,when formation time reaches to 1 d,the transfer resistance and film resistance reach to the maximum value.Hot growth film has better anticorrosion behaviour in bicarbonate/carbonate solution containing chloride ions or sulfide ions.Mott-Schottky analysis reveals that hot growth film has n-p type semi-conductive property.XPS results show that the hot growth film is mainly composed of the inner chromium oxide and the outer iron oxide.
