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| 1 | Ambient noise spectral properties in the north area of Xisha显示文摘Ambient noise is very important in the prediction system of a sonar performance, because it determines the detection ranges always in a passive sonar and usually in an active sonar. In the uncertainty issue for the sonar performance, it is necessary to know this factor's statistical characteristics that are only obtained by data processing from the underwater ambient noise measurements. Broad-band ambient noise signals from 16 hydrophones were amplified and recorded for 2 min every 1 h. The results show that the ambient noise is essentially depth independent. The cross correlation of the ambient noise levels(1, 6 and 12 h average) with a wind speed is presented. It was found that the correlation is excellent on the upper frequency band and the noise levels correlate better with high wind speed than with low wind speed. | DA Lianglong WANG Chao HAN Mei ZHANG Lin | 2014 | Acta Oceanologica Sinica2014，33，12： | 6 |
| 2 | The rapid uncertainty prediction of the ocean-acoustic coupled model显示文摘 | CUI Baolong DA Lianglong GUO Wuhong ZHAO Jianxin | 2018 | Chinese Journal of Acoustics2018，37，4： | 2 |
| 3 | Capturing uncertainties of the underwater acoustic environment based on an ocean-acoustic coupled model显示文摘Considering the uncertain effects of temporal and spatial changes in the marine environment on the underwater acoustic environment,we established an ocean-acoustic coupled numerical model and performed a parallel calculation.This model incorporated acoustic calculations into the dynamic ocean,thereby achieving a dynamic forecasting and assessment of the acoustic environment.Furthermore,we adopted the ensemble prediction method to predict the vertical structure of temperature in a classic cross-section,the sound speed of the cross-section of the investigated sea area,and transmission losses.We gave the prediction errors of the sound speed profile as well as the 90%probability interval of transmission losses and the uncertainty histograms of the sound speeds,transmission losses,and sonar ranges at different depths and frequencies.The results reflected the influence of marine temporal and spacial variations on the uncertainties of the underwater acoustic environment,and the results also quantified the uncertainties of the underwater acoustic environment parameters.The experimental results indicate that the method used in this study is able to delineate and quantify the uncertainties of the underwater acoustic environment caused by marine dynamic changes. | DA Lianglong GUO Wuhong ZHAO Jianxin FAN Peiqin | 2015 | Chinese Journal of Acoustics2015，34，3： | 2 |
| 4 | The characteristics of frequency-time azimuth spectrum estimation by a vector hydrophone in shallow water显示文摘 | DA Lianglong HOU Wenshu SUN Qindong | 2018 | Chinese Journal of Acoustics2018，37，1： | 1 |
| 5 | Identification of the sensitive area for targeted observation to improve vertical thermal structure prediction in summer in the Yellow Sea显示文摘The sensitive area of targeted observations for short-term(7 d)prediction of vertical thermal structure(VTS)in summer in the Yellow Sea was investigated.We applied the Conditional Nonlinear Optimal Perturbation(CNOP)method and an adjoint-free algorithm with the Regional Ocean Modeling System(ROMS).We used vertical integration of CNOP-type temperature errors to locate the sensitive areas,where reduction of initial errors is expected to yield the greatest improvement in VTS prediction for the selected verification area.The identified sensitive areas were northeast−southwest orientated northeast to the verification area,which were possibly related to the southwestward background currents.Then,we performed a series of sensitivity experiments to evaluate the effectiveness of the identified sensitive areas.Results show that initial errors in the identified sensitive areas had the greatest negative effect on VTS prediction in the verification area compared to errors in other areas(e.g.,the verification area and areas to its east and northeast).Moreover,removal of initial errors through deploying simulated observations in the identified sensitive areas led to more refined prediction than correction of initial conditions in the verification area itself.Our results suggest that implementation of targeted observation in the CNOP-based sensitive areas is an effective method to improve short-term prediction of VTS in summer in the Yellow Sea. | Huiqin Hu Jingyi Liu Lianglong Da Wuhong Guo Kun Liu Baolong Cui | 2021 | Acta Oceanologica Sinica2021，40，7： | 1 |
| 6 | A frequency-adapted optimal-weighted method of array interference striations显示文摘Considering the filter properties of the long horizontal line array(HLA) to the sound field modes,we established an adaptive optimal method to design HLA weights,which can change the filter pass band with the frequency.Using the normal modes theory and combining with the feature of the sound field HLA beamformer,and analyzing the differences of definition and slope in the LOFAR(Low Frequency Analysis Recording) spectrogram between the single-hydrophone and the beamformer,a frequency-adapted optimal-weighted(FAOW)estimate method was obtained by solving a quadratic optimization model with linear equality constraints.The numerical simulation and the experimental data analysis indicated that we can obtain the beamformer signal with the designed optimal array weight which was made up by the Surface-Reflected Bottom-Reflected modes or Non-Surface-Reflected Bottom-Reflected modes.The slope of striations in the signal spectrogram fitted well with the theoretical analysis. | DA Lianglong XU Guojun ZHAO Jianxin HAN Mei | 2017 | Chinese Journal of Acoustics2017，36，3： | 0 |
| 7 | Passive ranging of a moving sound source using three-dimensional measured information显示文摘To solve the problem of passive ranging of a moving sound source,a method of estimating the initial distance of target is presented by using the measured information of target azimuth,Doppler frequency shift and distance characteristic quantity.Through pseudo linearization,a linear model with heteroscedasticity is constructed.The system can uniquely determine the distance,velocity and course of a non-radial moving sound source target by using the observed information of three target bearings,two Doppler frequency shifts and two distance characteristic quantities,but the system is unobservable only by using the observed information of the target azimuth and distance characteristic quantity under the condition that the sonar platform moves in a straight line.Under the condition that the initial distance is 5 n mile,the Monte Carlo simulations show that the average convergence time of the three-dimensional information measured method is about 200 s less than that of the reference method,and the standard deviation of the convergence time is about 40 s less.Increasing the initial distance between the target and the sonar platform,the average convergence time difference between the two methods tends to increase,which means the robustness of the three-dimensional information construction method is better than that of the reference method.The experimental data further verify that the estimation of target distance tends to converge in about 300 s.Therefore,this method can realize passive ranging of a moving sound source under the condition of stable interference structure. | ZHAO Jianxin DA Lianglong XU Guojun GUO Wuhong | 2021 | Chinese Journal of Acoustics2021，40，3： | 0 |
| 8 | Turning depths of internal tides in the South China Sea inferred from profile data显示文摘Theoretically,propagating internal tides in the ocean may reflect at turning depths,where buoyancy frequencies equal tidal frequencies,before colliding with the air-sea interface or rugged bottom topography.Globally,the internal tide lower turning depths(ITLTDs)in the open ocean have been mapped;however,knowledge of the presence of ITLTDs in the South China Sea(SCS)is lacking.In this study,2125 high-quality temperature-salinity profiles(including 58 deep-sea hydrographic measurements with observational depths exceeding 3000 m)are collected and analyzed to investigate the existence of ITLTDs in the SCS.Furthermore,the concept of the upper turning depth is first introduced in the context of internal tides,and internal tide upper turning depths(ITUTDs)are also investigated.ITLTDs are found to exist at several abyssal stations;these stations are distributed mostly in the southern part of the SCS basin,possibly due to the greater water depths there.Fewer locations show the presence of ITLTDs for K_(1) versus M_(2) tidal frequencies because of the lower tidal frequency.The distance between ITLTDs and the seafloor ranged from 270 m to more than 1200 m,implying the possible existence of multiple internal wave evanescent regions in the abyssal bottom.ITUTDs of tens of meters are ubiquitous in the SCS;stations with the presence of ITUTDs are located mainly in the northeastern SCS due to the intensive observations there.However,the calculated ITUTDs have large uncertainties;they are sensitive to the selected bin values.The horizontal propagation directions of internal tides in the SCS change dramatically,and as a result,the estimated turning depths under the full Coriolis force definition are different compared to that under the traditional approximation. | Kun Liu Lianglong Da Wuhong Guo Chenglong Liu Junchuan Sun | 2022 | Acta Oceanologica Sinica2022，41，2： | 0 |
| 9 | The target motion parameters estimation based on the acoustic field interference structure similarity match显示文摘A spectral sequence matched algorithm based on acoustic field interference structure is proposed to estimate the target motion parameters.According to the longitudinalcorrelation of the acoustic field using the spectral sequences of different frequencies obtained from the target LOFAR spectrogram and the target range solution vector obtained from the two-azimuth and two-range target motion parameters calculation method,a matching cost factor of the spectral sequences similarity is constructed to estimate the target motion parameters.Both the numerical simulation and the experimental data analysis show that the initial range,course and speed can be clearly presented in the visual distribution diagram of target motion parameters.The results demonstrate that the algorithm is simple,efficient and robust to the azimuth errors. | DA Lianglong XU Guojun HAN Mei ZHANG Lin FAN Peiqin | 2020 | Chinese Journal of Acoustics2020，39，1： | 0 |
| 10 | Sparse asymptotic minimum variance based bearing estimation algorithm for a single vector hydrophone显示文摘For underwater target detection using a single vector hydrophone,sparse asymptotic minimum variance(SAMV)method is used to estimate the target bearing.The SAMV discretizes the entire scanning space and the target bearing is located at the position of the discrete direction.The SAMV algorithm utilizes the sparsity of the spatial signal to improve the estimation performance of the target bearing.Background noise level(BNL)of the bearing estimation of SAMV algorithm is lower than those of the conventional beam forming(CBF)method and minimum variance distortionless response(MVDR)method for different signal noise ratios(SNRs).When the SNR is higher than 0 d B,the direction-finding error of this algorithm is less than 2°.Moreover,the SAMV algorithm has a better dimensional orientation resolution capability.The experimental results show that the SAMV algorithm gives a bearing and time recording map with a lower BNL,which effectively verifies the effectiveness of SAMV algorithm in terms of underwater target detection. | WANG Chao DA Lianglong HAN Mei SUN Qindong WANG Wenlong | 2022 | Chinese Journal of Acoustics2022，41，1： | 0 |
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