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Three-dimensional mode coupling around a seamount

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Science China(Physics,Mechanics & Astronomy) 2011年第9期54卷 1561-1569页

作者： luo wenyu ZHANG RenHe SCHMIDT Henrik State Key Laboratory of Acoustics Institute of Acoustics Chinese Academy of Sciences Beijing 100190 China Department of Mechanical Engineering Massachusetts Institute of Technology Massachusetts 02139 USA

A recently developed three-dimensional normal-mode model is adopted to investigate mode coupling around a seamount in a deep water environment. As indicated by the theoretical analysis and verified by the numerical results, strong mode coupling occurs at the edge of a seamount under certain conditions. Therefore, mode coupling is critical for the investigation of the acoustic field in the presence of a seamount. In addition, the issue regarding the number of sectors assuring convergence is also presented. This issue is important in a two-way coupled-mode approach, especially for solving three-dimensional problems, because the computational effort increases dramatically with the number of sectors in representing a varying bathymetry. The theoretical analysis as well as the numerical example in this paper shows that artificial diffraction lobes form in the event that uniform discretization is used with a horizontal step size greater than half of the acoustic wavelength. However, by using random discretization instead, such artificial diffraction lobes are diffused, resulting in a faster convergence rate.

关键词： normal mode three-dimensional mode coupling seamount

An efficient broadband coupled-mode model using the Hamiltonian method for modal solutions

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Science China(Physics,Mechanics & Astronomy) 2017年第9期60卷 37-46页

作者： XueFeng Yang wenyu luo HaoZhong Wang ChangQing Hu Shanghai Acoustic Laboratory Chinese Academy of Sciences University of Chinese Academy of Sciences State Key Laboratory of Acoustics Institute of Acoustics Chinese Academy of Sciences College of Information Science and Engineering Ocean University of China

A numerically efficient broadband, range-dependent propagation model is proposed, which incorporates the Hamiltonian method into the coupled-mode model DGMCM. The Hamiltonian method is highly efficient for finding broadband eigenvalues, and DGMCM is an accurate model for range-dependent propagation in the frequency domain. Consequently, the proposed broadband model combining the Hamiltonian method and DGMCM has significant virtue in terms of both efficiency and accuracy. Numerical simulations are also provided. The numerical results indicate that the proposed model has a better performance over the broadband model using the Fourier synthesis and COUPLE, while retaining the same level of accuracy.

关键词： broadband modeling Fourier synthesis coupled modes Hamiltonian method range-dependent waveguide

A Tractable Approach to Analyzing the Physical-Layer Security in K-Tier Heterogeneous Cellular Networks

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China Communications 2015年第S1期12卷 166-173页

作者： ZHONG Zhihao PENG Janhua luo wenyu HUANG Kaizhi National Digital Switching System Engineering & Technological Research Center

This study proposes a tractable approach to analyze the physical-layer security in the downlink of a multi-tier heterogeneous cellular network. This method is based on stochastic geometry, has low computational complexity, and uses the two-dimensional Poisson point process to model the locations of K-tier base stations and receivers, including those of legitimate users and eavesdroppers. Then, the achievable secrecy rates for an arbitrary user are determined and the upper and lower bounds of secrecy coverage probability derived on the condition that cross-tier interference is the main contributor to aggregate interference. Finally, our analysis results reveal the innate connections between information-theoretic security and the spatial densities of legitimate and malicious nodes.

关键词： heterogeneous cellular networks physical layer security stochastic geometry secrecy coverage probability

A numerically stable coupled-mode formulation for acoustic propagation in range-dependent waveguides

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Science China(Physics,Mechanics & Astronomy) 2012年第4期55卷 572-588页

作者： luo wenyu YANG ChunMei QIN JiXing ZHANG RenHe State Key Laboratory of Acoustics Institute of AcousticsChinese Academy of SciencesBeijing 100190China Graduate University of Chinese Academy of Sciences Beijing 100049China

In this paper,a stepwise coupled-mode model with the use of the direct global matrix approach is *** method is capable of handling two-dimensional problems with either a point source in cylindrical geometry or a line source in plane *** the use of the direct global matrix approach,this method is numerically *** addition,by introducing appropriately normalized range solutions,this model is free from the numerical overflow ***,we put forward source conditions appropriate for the line-source problem in plane *** a result,this method is capable of addressing the scenario with a line source on top of a sloping ***-form expressions for coupling matrices are derived and applied in this paper for handling problems with pressure-release boundaries and a homogeneous water *** numerical simulations indicate that the proposed model is accurate,efficient,and numerically ***,this model can serve as a benchmark model in range-dependent propagation *** this method is verified by an ideal wedge problem in this paper,the formulation applies to realistic problems as well.

关键词： coupled-mode theory range-dependent waveguide direct global matrix approach

Robust secure transmission for multiuser MISO systems with probabilistic QoS constraints

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Science China(Information Sciences) 2016年第2期59卷 126-138页

作者： Lijian ZHANG Liang JIN wenyu luo Chunming WANG Yanqun TANG National Digital Switching System Engineering & Technological Research Center School of Information Systems Engineering Zhengzhou Information Science and Technology Institute

This paper considers a unicast multiuser multiple-input single-output(MISO) downlink system overheard by multiple single-antenna eavesdroppers. The objective is to jointly design the beamforming vectors and the artificial noise(AN) covariance matrix with imperfect channel state information(CSI) at the transmitter,such that the total transmit power is minimized while satisfying probabilistic quality of service(Qo S) constraints at legitimate users and the eavesdroppers. Using Bernstein-type inequalities and the S-procedure, we recast the non-convex power minimization problem as two different convex semidefinite programs(SDPs) which can be solved using interior-point methods. Simulation results show that the proposed methods outperform a nonrobust method and the ones using the isotropic AN.

关键词： physical layer security artificial noise imperfect CSI robust beamforming semidefinite program outage probability

Stability and a fast calculation method of travel speed of pulse peak in convergence zone

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Science China(Physics,Mechanics & Astronomy) 2014年第7期57卷 1274-1282页

作者： REN Yun ZHANG RenHe WANG Jun GUO YongGang luo wenyu State Key Laboratory of Acoustics Institute of Acoustics Chinese Academy of Sciences

A long-range sound propagation experiment was conducted in the West Pacific Ocean in summer *** signals received by a towed array indicate that the travel speed of pulse peak(TSPP)in the convergence zones is ***,an equivalent sound speed can be used at all ranges in the convergence zones.A fast calculation method based on the beam-displace-ment ray-mode(BDRM)theory and convergence zone theory is proposed to calculate this equivalent sound *** computation speed of this proposed method is over 1000 times faster than that of the conventional calculation method based on the normal mode theory,with the computation error less than 0.4%compared with the experimental ***,the effect of frequency and sound speed profile on the TSPP is studied with the conventional and fast calculation methods,showing that the TSPP is almost independent of the frequency and sound speed profile in the ocean surface layer.

关键词： travel speed pulse peak pulse propagation BDRM theory turning point convergence zone

Sound propagation from the shelfbreak to deep water

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Science China(Physics,Mechanics & Astronomy) 2014年第6期57卷 1031-1037页

作者： QIN JiXing ZHANG RenHe luo wenyu PENG ZhaoHui LIU JianJun WANG DeJun State Key Laboratory of Acoustics Institute of AcousticsChinese Academy of Sciences Graduate University of Chinese Academy of Sciences

Motivated by a phenomenon in an experiment conducted in the Northwestern Pacific indicating that the energy of the received signal around the sound channel axis is much greater than that at shallower depths,we study sound propagation from the transitional area(shelfbreak)to deep *** simulations with different source depths are first performed,from which we reach the following *** the source is located near the sea surface,sound will be strongly attenuated by bottom losses in a range-independent oceanic environment,whereas it can propagate to a very long range because of the continental *** the source is mounted on the bottom in shallow water,acoustic energy will be trapped near the sound channel axis,and it converges more evidently than the case where the source is located near the sea ***,numerical simulations with different source ranges are *** comparing the relative energy level in the vertical direction between the numerical simulations and the experimental data,the range of the air-gun source can be approximated.

关键词： sound propagation transitional area deep water parabolic equation

Experimental analysis on air-to-water sound transmission loss in shallow water

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Chinese Journal of Acoustics 2017年第2期36卷 217-230页

作者： ZHANG Lingshan PENG Zhaohui WANG Guangxu luo wenyu State Key Laboratory of Acoustics Institute of AcousticsChinese Academy of Sciences University of Chinese Academy of Sciences

The research of propagation characteristics of air-to-water sound transmission is of great importance to the detection of aerial targets from *** order to study the propagation characteristics of air-to-water sound transmission in shallow water,State Key Laboratory of Acoustics,Institute of Acoustics,conducted an experiment in the South China Sea in March,*** the experiment,multi-frequency signals transmitted by a hooter hung on a research ship were received by an underwater hydrophone,and the distance between the hooter and the hydrophone was from 2.4 km to 9.8 km *** analyzing experimental data in this work,the experimental air-to-water transmission loss at frequencies128 Hz and 256 Hz is estimated up to 9.8 km in range,and its oscillation structure is *** wave-number integration approach is used to simulate theoretical air-to-water transmission losses,which are in good agreement with experimental values and to explain the experimental air-to-water sound transmission characteristics.

关键词： shallow underwater transmitted airborne evident excited processed aerial calculating receiver

A two-way marching coupled-mode method for range-dependent propagation

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Chinese Journal of Acoustics 2012年第4期31卷 371-391页

作者： luo wenyu ZHANG Renhe SCHMIDT Henrik Institute of Acoustics Chinese Academy of Sciences Beijing 100190 Department of Mechanical Engineering MIT Cambridge MA 02139 USA

An efficient, accurate, and numerically stable coupled-mode solution is presented for acoustic propagation in a range-dependent waveguide. This method is numerically stable due to the appropriately normalized range solutions introduced in the formulation. In addition, by combining a forward marching and a backward marching, this method provides accurate solu- tions for range-dependent propagation problems, especially those characterized by large bottom slope angle and/or high impedance contrast between water and the bottom. Furthermore, this two-way solution also provides high efficiency, which is achieved by applying the single-scatter approximation. Numerical examples are also provided to demonstrate the efficiency, accuracy, and stability of this method.

关键词：声波传播耦合模式数值稳定标准化稳定性