Pub Date : 1993-10-18DOI: 10.1109/OCEANS.1993.326169
I.J. Booth, K. Booth
A software neural net model to recognise the calls of individual seals has been constructed and has been shown to perform satisfactorily with all of the mammals in the available set. It has also proved stable in the presence of both man made and natural noise. Operating and conditioning times on typical computers are provided.<>
{"title":"Using neural nets to identify marine mammals","authors":"I.J. Booth, K. Booth","doi":"10.1109/OCEANS.1993.326169","DOIUrl":"https://doi.org/10.1109/OCEANS.1993.326169","url":null,"abstract":"A software neural net model to recognise the calls of individual seals has been constructed and has been shown to perform satisfactorily with all of the mammals in the available set. It has also proved stable in the presence of both man made and natural noise. Operating and conditioning times on typical computers are provided.<<ETX>>","PeriodicalId":130255,"journal":{"name":"Proceedings of OCEANS '93","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129484958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-18DOI: 10.1109/OCEANS.1993.325968
R. Driscoll, L. Iggins
Summary form only given. Snap loading of the umbilical cable connecting a ship to a remotely operated vehicle (ROV) and its cage is a major problem when the ROV system is operating in rough sea conditions. Snap loading is the instantaneous, high magnitude, tensile loading of a cable. This loading arises when the amplitude and frequency of the ship motion is such that it causes parts of the cable to be subjected to compressive forces. Since cables are incapable of resisting such loads, slack can develop in a section of the cable where there is a compressive load. If the rate of retensioning is rapid, the cable will then experience snap loading. This paper describes the design of a passive damping system to attenuate snap loading in the ROV system. The mathematical model consists of the following sub-systems: 1) the boom and ship, 2) the cable, 3) the passive damper, and 4) the cage. The cable is modelled with discrete elements implemented using finite element theory. The total cable length is divided into a large number of elements, and the motion equations are written for each element, and a forcing function is applied to the top element.<>
{"title":"Passive damping to attenuate snap loading on a ROV umbilical cable","authors":"R. Driscoll, L. Iggins","doi":"10.1109/OCEANS.1993.325968","DOIUrl":"https://doi.org/10.1109/OCEANS.1993.325968","url":null,"abstract":"Summary form only given. Snap loading of the umbilical cable connecting a ship to a remotely operated vehicle (ROV) and its cage is a major problem when the ROV system is operating in rough sea conditions. Snap loading is the instantaneous, high magnitude, tensile loading of a cable. This loading arises when the amplitude and frequency of the ship motion is such that it causes parts of the cable to be subjected to compressive forces. Since cables are incapable of resisting such loads, slack can develop in a section of the cable where there is a compressive load. If the rate of retensioning is rapid, the cable will then experience snap loading. This paper describes the design of a passive damping system to attenuate snap loading in the ROV system. The mathematical model consists of the following sub-systems: 1) the boom and ship, 2) the cable, 3) the passive damper, and 4) the cage. The cable is modelled with discrete elements implemented using finite element theory. The total cable length is divided into a large number of elements, and the motion equations are written for each element, and a forcing function is applied to the top element.<<ETX>>","PeriodicalId":130255,"journal":{"name":"Proceedings of OCEANS '93","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130339167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-18DOI: 10.1109/OCEANS.1993.326127
H. Freitag, P.E. Plimpton, M. Mcphaden
Downward-looking surface-moored Acoustic Doppler Current Profiler (ADCP) data is at times biased towards lower values when compared to mechanical current meters (MCM). This bias has been shown to be caused by the attraction of large pelagic fish to surface moorings. RD Instruments ADCPs have an optional algorithm which attempts to limit velocity bias due to fish. The algorithm compares echo intensity amplitude among the four beams of the instrument and rejects samples in which the highest and lowest echo intensity amplitude differ by more than a given level. The performance of the algorithm was evaluated at deployments in the eastern and western equatorial Pacific. Bias was found to be reduced in some cases, but remained in others. The cause of residual bias is shown to be the presence of fish in all four acoustic beams-a condition not considered by the algorithm. A post-processing method of correcting fish bias in ADCP velocity data is presented. The method involved computing vertical modes of the bias from ADCP-MCM differences using empirical orthogonal functions (EOFs). The vertical structure of the EOFs was interpolated to the higher vertical resolution of the ADCP and then applied as a correction to the ADCP data. The quality of ADCP data was significantly improved by this correction.<>
{"title":"Evaluation of an ADCP fish-bias rejection algorithm","authors":"H. Freitag, P.E. Plimpton, M. Mcphaden","doi":"10.1109/OCEANS.1993.326127","DOIUrl":"https://doi.org/10.1109/OCEANS.1993.326127","url":null,"abstract":"Downward-looking surface-moored Acoustic Doppler Current Profiler (ADCP) data is at times biased towards lower values when compared to mechanical current meters (MCM). This bias has been shown to be caused by the attraction of large pelagic fish to surface moorings. RD Instruments ADCPs have an optional algorithm which attempts to limit velocity bias due to fish. The algorithm compares echo intensity amplitude among the four beams of the instrument and rejects samples in which the highest and lowest echo intensity amplitude differ by more than a given level. The performance of the algorithm was evaluated at deployments in the eastern and western equatorial Pacific. Bias was found to be reduced in some cases, but remained in others. The cause of residual bias is shown to be the presence of fish in all four acoustic beams-a condition not considered by the algorithm. A post-processing method of correcting fish bias in ADCP velocity data is presented. The method involved computing vertical modes of the bias from ADCP-MCM differences using empirical orthogonal functions (EOFs). The vertical structure of the EOFs was interpolated to the higher vertical resolution of the ADCP and then applied as a correction to the ADCP data. The quality of ADCP data was significantly improved by this correction.<<ETX>>","PeriodicalId":130255,"journal":{"name":"Proceedings of OCEANS '93","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121179221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-18DOI: 10.1109/OCEANS.1993.325987
M. Foreman, R. Walters, R. Henry
A three-dimensional, finite element model has been developed to calculate the tidal and estuarine flows in the eastern Juan de Fuca Strait and the southern Strait of Georgia. The estuarine component is computed diagnostically from historical salinity and temperature measurements taken during each month in 1968. The tidal component is approximated with eight constituents that account for about 85% of the daily and half-daily signal. Predictions based on these model results will be used for pollution studies, commercial and pleasure boating, and search and rescue.<>
{"title":"A model for simulating currents in eastern Juan de Fuca Strait and and the southern Strait of Georgia","authors":"M. Foreman, R. Walters, R. Henry","doi":"10.1109/OCEANS.1993.325987","DOIUrl":"https://doi.org/10.1109/OCEANS.1993.325987","url":null,"abstract":"A three-dimensional, finite element model has been developed to calculate the tidal and estuarine flows in the eastern Juan de Fuca Strait and the southern Strait of Georgia. The estuarine component is computed diagnostically from historical salinity and temperature measurements taken during each month in 1968. The tidal component is approximated with eight constituents that account for about 85% of the daily and half-daily signal. Predictions based on these model results will be used for pollution studies, commercial and pleasure boating, and search and rescue.<<ETX>>","PeriodicalId":130255,"journal":{"name":"Proceedings of OCEANS '93","volume":"136 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121414994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-18DOI: 10.1109/OCEANS.1993.326070
D. Pantzartzis, C. D. de Moustier, D. Alexandrou
In the context of swath bathymetry with multibeam echo-sounders, seafloor echoes received at regularly spaced elements of a hydrophone array are summed coherently to form a number of directional beams from which athwartships depth measurements are derived. This process can be implemented as a conventional beamformer leading to estimates of the direction of arrival of the echoes for each time sample. The process is inadequate in resolving closely spaced synchronous returns and the accuracy of these estimates is proportional to the number of acoustic data samples used in the process. To improve the angular resolution the authors have considered a number of high-resolution algorithms well known in power spectral estimation applications: autoregressive techniques (i.e. Yule-Walker, and unconstrained least squares), minimum variance methods (i.e. Capon's method), and eigenanalysis algorithms (i.e. MUSIC). Comparisons of results obtained with realistic multibeam sonar simulations show that these algorithms have higher accuracy and better potential for high-resolution bathymetry than the conventional beamformer under nominal SNR levels.<>
{"title":"Application of high-resolution beamforming to multibeam swath bathymetry","authors":"D. Pantzartzis, C. D. de Moustier, D. Alexandrou","doi":"10.1109/OCEANS.1993.326070","DOIUrl":"https://doi.org/10.1109/OCEANS.1993.326070","url":null,"abstract":"In the context of swath bathymetry with multibeam echo-sounders, seafloor echoes received at regularly spaced elements of a hydrophone array are summed coherently to form a number of directional beams from which athwartships depth measurements are derived. This process can be implemented as a conventional beamformer leading to estimates of the direction of arrival of the echoes for each time sample. The process is inadequate in resolving closely spaced synchronous returns and the accuracy of these estimates is proportional to the number of acoustic data samples used in the process. To improve the angular resolution the authors have considered a number of high-resolution algorithms well known in power spectral estimation applications: autoregressive techniques (i.e. Yule-Walker, and unconstrained least squares), minimum variance methods (i.e. Capon's method), and eigenanalysis algorithms (i.e. MUSIC). Comparisons of results obtained with realistic multibeam sonar simulations show that these algorithms have higher accuracy and better potential for high-resolution bathymetry than the conventional beamformer under nominal SNR levels.<<ETX>>","PeriodicalId":130255,"journal":{"name":"Proceedings of OCEANS '93","volume":"277 ","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113983304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-18DOI: 10.1109/OCEANS.1993.326069
J. Sun, R. Tyce
Bathymetry side-scan sonars (BASS), using two rows of transducers and the phase measuring technique, offer a simple approach to single swath mapping sonar systems which integrate both seafloor bathymetry and imagery. This paper discusses both BASS system design and the environmental factors which influence our ability to accurately determine travel time and arrival angle-the two parameters required to determine bathymetry. The authors have recently examined bathymetric performance limitations for an upgraded GLORIA system belonging to the USGS. Theoretical GLORIA phase data are presented along with the first field data. Phase difference estimates using different phase estimation algorithms are presented.<>
{"title":"Performance limitations on travel time and phase data extraction for bathymetry side-scan sonars","authors":"J. Sun, R. Tyce","doi":"10.1109/OCEANS.1993.326069","DOIUrl":"https://doi.org/10.1109/OCEANS.1993.326069","url":null,"abstract":"Bathymetry side-scan sonars (BASS), using two rows of transducers and the phase measuring technique, offer a simple approach to single swath mapping sonar systems which integrate both seafloor bathymetry and imagery. This paper discusses both BASS system design and the environmental factors which influence our ability to accurately determine travel time and arrival angle-the two parameters required to determine bathymetry. The authors have recently examined bathymetric performance limitations for an upgraded GLORIA system belonging to the USGS. Theoretical GLORIA phase data are presented along with the first field data. Phase difference estimates using different phase estimation algorithms are presented.<<ETX>>","PeriodicalId":130255,"journal":{"name":"Proceedings of OCEANS '93","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124293940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-18DOI: 10.1109/OCEANS.1993.326199
M. Wilmut, N. Chapman, S. Anderson
Ambient noise was measured at a deep ocean site using 16-element vertical line array which was deployed near the axis of the sound channel. Noise samples were recorded for time periods from 30 s to 120 s, and for local wind speeds from 2 to 15 m/s. Beamformed data were used to study the statistical properties of horizontal components of the noise field at a frequency of 245 Hz. It is well known in underwater acoustics that the horizontal component is sensitive to distant shipping noise and the vertical component is sensitive to local surface noise. The results indicated that both components of the noise field were independent, stationary and normally distributed for wind speeds greater than 7 m/s. However, at lower wind speeds, the vertical component did not pass the Lilliefor's test for normality. This result suggests that the noise process for surface generated noise at low wind speeds is not normally distributed. The results for the analysis of omnidirectional noise data indicated that the noise in the 49-300 Hz band as independent, stationary and normal for periods of up to two minutes.<>
{"title":"Statistical properties of horizontal, vertical and omnidirectional underwater noise fields at low frequency","authors":"M. Wilmut, N. Chapman, S. Anderson","doi":"10.1109/OCEANS.1993.326199","DOIUrl":"https://doi.org/10.1109/OCEANS.1993.326199","url":null,"abstract":"Ambient noise was measured at a deep ocean site using 16-element vertical line array which was deployed near the axis of the sound channel. Noise samples were recorded for time periods from 30 s to 120 s, and for local wind speeds from 2 to 15 m/s. Beamformed data were used to study the statistical properties of horizontal components of the noise field at a frequency of 245 Hz. It is well known in underwater acoustics that the horizontal component is sensitive to distant shipping noise and the vertical component is sensitive to local surface noise. The results indicated that both components of the noise field were independent, stationary and normally distributed for wind speeds greater than 7 m/s. However, at lower wind speeds, the vertical component did not pass the Lilliefor's test for normality. This result suggests that the noise process for surface generated noise at low wind speeds is not normally distributed. The results for the analysis of omnidirectional noise data indicated that the noise in the 49-300 Hz band as independent, stationary and normal for periods of up to two minutes.<<ETX>>","PeriodicalId":130255,"journal":{"name":"Proceedings of OCEANS '93","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126397287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-18DOI: 10.1109/OCEANS.1993.326113
B. Lévesque, M. Richard
This paper introduces an augmented dynamical model for robotic manipulators, including an approximation method for the computation of drag forces. A stochastic adaptive controller, based on this model and on a model of noisy flow is then developed for the regulation of motions of a manipulator subjected to highly variable flows. The techniques described here will help to stabilize underwater systems without the help of an operator, which is an important problem due to long transmission delays in some control systems. Simulations with noisy flows show very interesting results.<>
{"title":"Simplified dynamics and stochastic controller for underwater robots","authors":"B. Lévesque, M. Richard","doi":"10.1109/OCEANS.1993.326113","DOIUrl":"https://doi.org/10.1109/OCEANS.1993.326113","url":null,"abstract":"This paper introduces an augmented dynamical model for robotic manipulators, including an approximation method for the computation of drag forces. A stochastic adaptive controller, based on this model and on a model of noisy flow is then developed for the regulation of motions of a manipulator subjected to highly variable flows. The techniques described here will help to stabilize underwater systems without the help of an operator, which is an important problem due to long transmission delays in some control systems. Simulations with noisy flows show very interesting results.<<ETX>>","PeriodicalId":130255,"journal":{"name":"Proceedings of OCEANS '93","volume":"79 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128106250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-18DOI: 10.1109/OCEANS.1993.326228
A. Zielinski, R. Coates, L. Wang, A. Saleh
High rate communication over a very shallow channel is discussed. A multipath for such a channel is proposed and is used to predict performance of a phase modulated acoustic communication system. The results obtained indicate that transmission rates in excess of 6 kbits/s are possible over a distance of 3.5 km and in a water depth of only 15 meters. Such a system can find application for collecting data from underwater sensors.<>
{"title":"High rate shallow water acoustic communication","authors":"A. Zielinski, R. Coates, L. Wang, A. Saleh","doi":"10.1109/OCEANS.1993.326228","DOIUrl":"https://doi.org/10.1109/OCEANS.1993.326228","url":null,"abstract":"High rate communication over a very shallow channel is discussed. A multipath for such a channel is proposed and is used to predict performance of a phase modulated acoustic communication system. The results obtained indicate that transmission rates in excess of 6 kbits/s are possible over a distance of 3.5 km and in a water depth of only 15 meters. Such a system can find application for collecting data from underwater sensors.<<ETX>>","PeriodicalId":130255,"journal":{"name":"Proceedings of OCEANS '93","volume":"192 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125665570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1993-10-18DOI: 10.1109/OCEANS.1993.326145
W. Venezia, J.N. Aycock
A continuing need exists for accurate three dimensional tracking of submerged targets on instrument ranges. The common problems faced by developers of acoustic underwater tracking systems range from launch, recovery, and structure life to telemetry and real time processing of source signals. The Naval Surface Warfare Center controls an underwater test site that ranges from shore to a water depth of 600 meters. To support long term growth, an underwater tracking system capable of operating over the majority of the range with a serviceable life of twenty years was developed and is described. The system design goals included long term compatibility with the marine environment and stringent tracking accuracy requirements. Environmentally compatible materials selection included fiber reinforced plastics for structures, glass spheres for pressure vessels, and titanium for fasteners. Tracking accuracy is achieved using a synchronous tracking system consisting of four hydrophones on an eight meter baseline. Pulse detection and arrival time are determined using a combination of in band and out of band energy detection with replica correlation of the apex channel. The system has single bit digitizing using zero crossing detectors. Differential arrival times for two adjacent channels are determined using cross correlation with the apex channel. This paper contributes an overview of the underwater tracking system and of the Fort Lauderdale facilities and test capabilities. A summary of experimentally obtained data on the tracking accuracy from deployments in 180 and 450 meters is given. Tracking resolutions are given as a function of environmental parameters including range from the array, depth, and ambient sound velocity profiles. Array performance characteristics are extrapolated over usable water depth based on evaluation of the arrays at the two test sites.<>
{"title":"Test and evaluation of a midwater three dimensional underwater tracking array","authors":"W. Venezia, J.N. Aycock","doi":"10.1109/OCEANS.1993.326145","DOIUrl":"https://doi.org/10.1109/OCEANS.1993.326145","url":null,"abstract":"A continuing need exists for accurate three dimensional tracking of submerged targets on instrument ranges. The common problems faced by developers of acoustic underwater tracking systems range from launch, recovery, and structure life to telemetry and real time processing of source signals. The Naval Surface Warfare Center controls an underwater test site that ranges from shore to a water depth of 600 meters. To support long term growth, an underwater tracking system capable of operating over the majority of the range with a serviceable life of twenty years was developed and is described. The system design goals included long term compatibility with the marine environment and stringent tracking accuracy requirements. Environmentally compatible materials selection included fiber reinforced plastics for structures, glass spheres for pressure vessels, and titanium for fasteners. Tracking accuracy is achieved using a synchronous tracking system consisting of four hydrophones on an eight meter baseline. Pulse detection and arrival time are determined using a combination of in band and out of band energy detection with replica correlation of the apex channel. The system has single bit digitizing using zero crossing detectors. Differential arrival times for two adjacent channels are determined using cross correlation with the apex channel. This paper contributes an overview of the underwater tracking system and of the Fort Lauderdale facilities and test capabilities. A summary of experimentally obtained data on the tracking accuracy from deployments in 180 and 450 meters is given. Tracking resolutions are given as a function of environmental parameters including range from the array, depth, and ambient sound velocity profiles. Array performance characteristics are extrapolated over usable water depth based on evaluation of the arrays at the two test sites.<<ETX>>","PeriodicalId":130255,"journal":{"name":"Proceedings of OCEANS '93","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132421691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：