Long-time coherent integration(LTCI)is an effective way for radar maneuvering target detection,but it faces the problem of a large number of search parameters and large amount of calculation.Realizing the simultaneous...Long-time coherent integration(LTCI)is an effective way for radar maneuvering target detection,but it faces the problem of a large number of search parameters and large amount of calculation.Realizing the simultaneous compensation of the range and Doppler migrations in complex clutter back-ground,and at the same time improving the calculation efficiency has become an urgent problem to be solved.The sparse transformation theory is introduced to LTCI in this paper,and a non-parametric searching sparse LTCI(SLTCI)based maneuvering target detection method is proposed.This method performs time reversal(TR)and second-order Keystone transform(SKT)in the range frequency&slow-time data to complete high-order range walk compensation,and achieves the coherent integra-tion of maneuvering target across range and Doppler units via the robust sparse fractional Fourier transform(RSFRFT).It can compensate for the nonlinear range migration caused by high-order motion.S-band and X-band radar data measured in sea clutter background are used to verify the detection performance of the proposed method,which can achieve better detection performance of maneuvering targets with less computational burden compared with several popular integration methods.展开更多
Based on the fifth-order Stokes regular wave theory, a simplified model for extreme-wave kinematics in deep sea was developed. In this model, from the wave records the average of two neighboring wave periods for the e...Based on the fifth-order Stokes regular wave theory, a simplified model for extreme-wave kinematics in deep sea was developed. In this model, from the wave records the average of two neighboring wave periods for the extreme crest or trough was defined as the period of the Stokes wave by the up and down zero-crossing methods. Then the input wave amplitude was deduced by substituting the wave period and extreme crest or trough into the expression for the fifth-order Stokes wave elevation. Thus the corresponding formula for the wave velocity can be used to describe kinematics beneath the extreme wave. By comparison with the published numerical models and experimental data, the proposed model is validated to be able to calculate the extreme wave velocity rather easily and accurately.展开更多
The mitochondrial genome(mitogenome)analysis is a significant tool for investigating the evolutionary history of metazoan animals.The family Pandalidae is a diverse caridean group containing mainly deep-sea species.Un...The mitochondrial genome(mitogenome)analysis is a significant tool for investigating the evolutionary history of metazoan animals.The family Pandalidae is a diverse caridean group containing mainly deep-sea species.Until May 302019,only two complete mitogenomes are available in GenBank.Here we present the complete mitogenome sequences of two deep-sea pandalid shrimps,Heterocarpus ensifer and Bitias brevis through Illumina sequencing.The mitochondrial genomes were determined to be 15939 bp and 15891 bp long,and both consist of 13 protein-coding genes(PCGs),23 transfer-RNA genes(tRNAs),two ribosomal-RNA genes(rRNAs),and one control region.The nucleotide composition is biased toward adenine and thymine.Overall,the gene contents and arrangements are consistent with the pancrustacean ground pattern.The alignment of the control regions of four pandalids reveals a conserved sequence block(CSB)(104 bp in length,average GC%=29.47%and 69.23%similarity).A phylogenetic analysis based on 51 Caridea complete mitogenomes revealed that the deep-sea pandalid shrimps are situated an intermediate lineage,with a tendency to originated from those living in shallow sea area.展开更多
In conventional marine seismic exploration data processing,the sea surface is usually treated as a horizontal free boundary.However,the sea surface is affected by wind and waves and there often exists dynamic small-ra...In conventional marine seismic exploration data processing,the sea surface is usually treated as a horizontal free boundary.However,the sea surface is affected by wind and waves and there often exists dynamic small-range fluctuations.These dynamic fluctuations will change the energy propagation path and affect the final imaging results.In theoretical research,different sea surface conditions need to be described,so it is necessary to study the modeling method of dynamic undulating sea surface.Starting from the commonly used sea surface mathematical simulation methods,this paper mainly studies the realization process of simple harmonic wave and Gerstner wave sea surface simulation methods based on ocean wave spectrum,and compares their advantages and disadvantages.Aiming at the shortcomings of the simple harmonic method and Gerstner method in calculational speed and sea surface simulation effect,a method based on wave equation and using dynamic boundary conditions for sea surface simulation is proposed.The calculational speed of this method is much faster than the commonly used simple harmonic method and Gerstner wave method.In addition,this paper also compares the new method with the more commonly used higher-order spectral methods to show the characteristics of the improved wave equation method.展开更多
The occurrence of rogue waves is closely related to the non-Gaussianity of sea states,and this non-Gaussianity can be estimated using corresponding two-dimensional wave spectra.This paper presents an approach to non-G...The occurrence of rogue waves is closely related to the non-Gaussianity of sea states,and this non-Gaussianity can be estimated using corresponding two-dimensional wave spectra.This paper presents an approach to non-Gaussianity estimation based on a phase-resolving model called the high-order spectral method(HOSM).Based on numerous HOSM simulations,a set of precalculated non-Gaussianity indicators was established that could be applied to real sea states without any calibration of spectral shapes.With a newly developed extraction approach,the indicators for given two-dimensional wave spectra could then be conveniently extracted from the precalculated dataset.The feasibility of the newly developed approach in a real wave environment is verified.Using the estimation approach,phase-resolved non-Gaussianity can now be illustrated throughout the evolution of sea states of interest,not just at a few specific times;and the level of non-Gaussianity at any time in a duration can be identified according to the statistics(e.g.,quantities)of the phase-resolved indicators,that are obtained throughout the duration concerned.展开更多
There are various indications that the so-called Arbitral Tribunal on the South China Sea disputes arbitration has become a tool for a few Western countries such as the United States,Japan and some others outside the ...There are various indications that the so-called Arbitral Tribunal on the South China Sea disputes arbitration has become a tool for a few Western countries such as the United States,Japan and some others outside the region to play political games with China and challenge China’s inherent rights and legitimate claims in the展开更多
针对短相干积累时间(coherent integration time,CIT)引起的多普勒分辨率低,无法从强大海杂波中检测出舰船目标的问题,提出了基于高阶奇异值分解(higher order singular value decomposition,HOSVD)的海杂波抑制算法。首先利用相邻单元...针对短相干积累时间(coherent integration time,CIT)引起的多普勒分辨率低,无法从强大海杂波中检测出舰船目标的问题,提出了基于高阶奇异值分解(higher order singular value decomposition,HOSVD)的海杂波抑制算法。首先利用相邻单元内海杂波的相干性,将毗邻距离单元和方位单元的多脉冲接收数据应用三阶张量表示,然后采用HOSVD方法求解三阶张量的海杂波子空间和目标子空间的投影矩阵,最后利用投影矩阵将三阶张量映射到目标子空间以抑制海杂波。该方法与现有子空间类海杂波抑制方法相比,提高了信干噪比(signal to clutter plus noise ratio,SCNR)和峰值旁瓣电平比(peak sidelobe level ratio,PSLR),解决了目标谱峰偏移问题。展开更多
基金supported by the National Natural Science Foundation of China(62222120,61871391,U1933135)Shandong Provincial Natural Science Foundation(ZR2021YQ43).
文摘Long-time coherent integration(LTCI)is an effective way for radar maneuvering target detection,but it faces the problem of a large number of search parameters and large amount of calculation.Realizing the simultaneous compensation of the range and Doppler migrations in complex clutter back-ground,and at the same time improving the calculation efficiency has become an urgent problem to be solved.The sparse transformation theory is introduced to LTCI in this paper,and a non-parametric searching sparse LTCI(SLTCI)based maneuvering target detection method is proposed.This method performs time reversal(TR)and second-order Keystone transform(SKT)in the range frequency&slow-time data to complete high-order range walk compensation,and achieves the coherent integra-tion of maneuvering target across range and Doppler units via the robust sparse fractional Fourier transform(RSFRFT).It can compensate for the nonlinear range migration caused by high-order motion.S-band and X-band radar data measured in sea clutter background are used to verify the detection performance of the proposed method,which can achieve better detection performance of maneuvering targets with less computational burden compared with several popular integration methods.
基金Supported by the NSFC (under Grant Nos.5070900 and 10772040)the National High Tech Research and Development Program of China (2006AA09A109-3)
文摘Based on the fifth-order Stokes regular wave theory, a simplified model for extreme-wave kinematics in deep sea was developed. In this model, from the wave records the average of two neighboring wave periods for the extreme crest or trough was defined as the period of the Stokes wave by the up and down zero-crossing methods. Then the input wave amplitude was deduced by substituting the wave period and extreme crest or trough into the expression for the fifth-order Stokes wave elevation. Thus the corresponding formula for the wave velocity can be used to describe kinematics beneath the extreme wave. By comparison with the published numerical models and experimental data, the proposed model is validated to be able to calculate the extreme wave velocity rather easily and accurately.
基金Supported by the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(CAS)(No.QYZDB-SSW-DQC036)the Strategic Priority Research Program of CAS(No.XDA22050302)+1 种基金the Senior User Project of R/V Kexue(No.KEXUE2019GZ02)the National Natural Science Foundation of China(No.31872215)。
文摘The mitochondrial genome(mitogenome)analysis is a significant tool for investigating the evolutionary history of metazoan animals.The family Pandalidae is a diverse caridean group containing mainly deep-sea species.Until May 302019,only two complete mitogenomes are available in GenBank.Here we present the complete mitogenome sequences of two deep-sea pandalid shrimps,Heterocarpus ensifer and Bitias brevis through Illumina sequencing.The mitochondrial genomes were determined to be 15939 bp and 15891 bp long,and both consist of 13 protein-coding genes(PCGs),23 transfer-RNA genes(tRNAs),two ribosomal-RNA genes(rRNAs),and one control region.The nucleotide composition is biased toward adenine and thymine.Overall,the gene contents and arrangements are consistent with the pancrustacean ground pattern.The alignment of the control regions of four pandalids reveals a conserved sequence block(CSB)(104 bp in length,average GC%=29.47%and 69.23%similarity).A phylogenetic analysis based on 51 Caridea complete mitogenomes revealed that the deep-sea pandalid shrimps are situated an intermediate lineage,with a tendency to originated from those living in shallow sea area.
基金The General Program of National Natural Science Foundation of China under contract No.42074150the National Key Research and Development Project under contract No.2017YFC0601305。
文摘In conventional marine seismic exploration data processing,the sea surface is usually treated as a horizontal free boundary.However,the sea surface is affected by wind and waves and there often exists dynamic small-range fluctuations.These dynamic fluctuations will change the energy propagation path and affect the final imaging results.In theoretical research,different sea surface conditions need to be described,so it is necessary to study the modeling method of dynamic undulating sea surface.Starting from the commonly used sea surface mathematical simulation methods,this paper mainly studies the realization process of simple harmonic wave and Gerstner wave sea surface simulation methods based on ocean wave spectrum,and compares their advantages and disadvantages.Aiming at the shortcomings of the simple harmonic method and Gerstner method in calculational speed and sea surface simulation effect,a method based on wave equation and using dynamic boundary conditions for sea surface simulation is proposed.The calculational speed of this method is much faster than the commonly used simple harmonic method and Gerstner wave method.In addition,this paper also compares the new method with the more commonly used higher-order spectral methods to show the characteristics of the improved wave equation method.
基金Supported by the National Key Research and Development Program of China(Nos.2016YFC1402004,2016YFC1401805,2017YFC1404201)。
文摘The occurrence of rogue waves is closely related to the non-Gaussianity of sea states,and this non-Gaussianity can be estimated using corresponding two-dimensional wave spectra.This paper presents an approach to non-Gaussianity estimation based on a phase-resolving model called the high-order spectral method(HOSM).Based on numerous HOSM simulations,a set of precalculated non-Gaussianity indicators was established that could be applied to real sea states without any calibration of spectral shapes.With a newly developed extraction approach,the indicators for given two-dimensional wave spectra could then be conveniently extracted from the precalculated dataset.The feasibility of the newly developed approach in a real wave environment is verified.Using the estimation approach,phase-resolved non-Gaussianity can now be illustrated throughout the evolution of sea states of interest,not just at a few specific times;and the level of non-Gaussianity at any time in a duration can be identified according to the statistics(e.g.,quantities)of the phase-resolved indicators,that are obtained throughout the duration concerned.
文摘There are various indications that the so-called Arbitral Tribunal on the South China Sea disputes arbitration has become a tool for a few Western countries such as the United States,Japan and some others outside the region to play political games with China and challenge China’s inherent rights and legitimate claims in the
文摘针对短相干积累时间(coherent integration time,CIT)引起的多普勒分辨率低,无法从强大海杂波中检测出舰船目标的问题,提出了基于高阶奇异值分解(higher order singular value decomposition,HOSVD)的海杂波抑制算法。首先利用相邻单元内海杂波的相干性,将毗邻距离单元和方位单元的多脉冲接收数据应用三阶张量表示,然后采用HOSVD方法求解三阶张量的海杂波子空间和目标子空间的投影矩阵,最后利用投影矩阵将三阶张量映射到目标子空间以抑制海杂波。该方法与现有子空间类海杂波抑制方法相比,提高了信干噪比(signal to clutter plus noise ratio,SCNR)和峰值旁瓣电平比(peak sidelobe level ratio,PSLR),解决了目标谱峰偏移问题。
