Inversion of Seabed Geotechnical Properties in the Arctic Chukchi Deep Sea Basin Based on Time Domain Adaptive Search Matching Algorithm

The chirp sub-bottom profiler,for its high resolution,easy accessibility and cost-effectiveness,has been widely used in acoustic detection.In this paper,the acoustic impedance and grain size compositions were obtained based on the chirp sub-bottom profiler data collected in the Chukchi Plateau area during the 11th Arctic Expedition of China.The time-domain adaptive search matching algorithm was used and validated on our established theoretical model.The misfit between the inversion result and the theoretical model is less than 0.067%.The grain size was calculated according to the empirical relationship between the acoustic impedance and the grain size of the sediment.The average acoustic impedance of sub-seafloor strata is 2.5026×10^(6) kg(s m^(2))^(-1)and the average grain size(θvalue)of the seafloor surface sediment is 7.1498,indicating the predominant occurrence of very fine silt sediment in the study area.Comparison of the inversion results and the laboratory measurements of nearby borehole samples shows that they are in general agreement.

A Parallel Global-Local Mixed Evolutionary Algorithm for Multimodal Function Optimization Based on Domain Decomposition

This paper presents a parallel two-level evolutionary algorithm based on domain decomposition for solving function optimization problem containing multiple solutions. By combining the characteristics of the global search and local search in each sub-domain, the former enables individual to draw closer to each optima and keeps the diversity of individuals, while the latter selects local optimal solutions known as latent solutions in sub-domain. In the end, by selecting the global optimal solutions from latent solutions in each sub-domain, we can discover all the optimal solutions easily and quickly.

Immune evolutionary algorithms with domain knowledge for simultaneous localization and mapping

Immune evolutionary algorithms with domain knowledge were presented to solve the problem of simultaneous localization and mapping for a mobile robot in unknown environments. Two operators with domain knowledge were designed in algorithms, where the feature of parallel line segments without the problem of data association was used to construct a vaccination operator, and the characters of convex vertices in polygonal obstacle were extended to develop a pulling operator of key point grid. The experimental results of a real mobile robot show that the computational expensiveness of algorithms designed is less than other evolutionary algorithms for simultaneous localization and mapping and the maps obtained are very accurate. Because immune evolutionary algorithms with domain knowledge have some advantages, the convergence rate of designed algorithms is about 44% higher than those of other algorithms.

ANALYSIS OF WAVEGUIDE PROBLEMS USING A RELAXED ITERATIVE DOMAIN DECOMPOSITION METHOD COMBINED WITH MULTIFRONTAL ALGORITHM

In this paper, an absorbing Fictitious Boundary Condition (FBC) is presented to generate an iterative Domain Decomposition Method (DDM) for analyzing waveguide problems.The relaxed algorithm is introduced to improve the iterative convergence. And the matrix equations are solved using the multifrontal algorithm. The resulting CPU time is greatly reduced.Finally, a number of numerical examples are given to illustrate its accuracy and efficiency.

A ROBUST PHASE-ONLY DIRECT DATA DOMAIN ALGORITHM BASED ON GENERALIZED RAYLEIGH QUOTIENT OPTIMIZATION USING HYBRID GENETIC ALGORITHM

A robust phase-only Direct Data Domain Least Squares (D3LS) algorithm based on gen- eralized Rayleigh quotient optimization using hybrid Genetic Algorithm (GA) is presented in this letter. The optimization efficiency and computational speed are improved via the hybrid GA com- posed of standard GA and Nelder-Mead simplex algorithms. First, the objective function, with a form of generalized Rayleigh quotient, is derived via the standard D3LS algorithm. It is then taken as a fitness function and the unknown phases of all adaptive weights are taken as decision variables. Then, the nonlinear optimization is performed via the hybrid GA to obtain the optimized solution of phase-only adaptive weights. As a phase-only adaptive algorithm, the proposed algorithm is sim- pler than conventional algorithms when it comes to hardware implementation. Moreover, it proc- esses only a single snapshot data as opposed to forming sample covariance matrix and operating matrix inversion. Simulation results show that the proposed algorithm has a good signal recovery and interferences nulling performance, which are superior to that of the phase-only D3LS algorithm based on standard GA.

Parallel finite element algorithm based on full domain partition for stationary Stokes equations

Based on the full domain partition, a parallel finite element algorithm for the stationary Stokes equations is proposed and analyzed. In this algorithm, each subproblem is defined in the entire domain. Majority of the degrees of freedom are associated with the relevant subdomain. Therefore, it can be solved in parallel with other subproblems using an existing sequential solver without extensive recoding. This allows the algorithm to be implemented easily with low communication costs. Numerical results are given showing the high efficiency of the parallel algorithm.

Error Analysis in Frequency Domain for Linear Multipass Algorithms

Error analysis methods in frequency domain are developed in this paper for determining the characteristic root and transfer function errors when the linear multipass algorithms are used to solve linear differential equations. The relation between the local truncation error in time domain and the error in frequency domain is established, which is the basis for developing the error estimation methods. The error estimation methods for the digital simulation model constructed by using the Runge-Kutta algorithms and the linear multistep predictor-corrector algorithms are also given.

A Domain Extension Algorithm for Digital Error Correction of Pipeline ADCs

A domain extension algorithm to correct the comparator offsets of pipeline analog-to-digital converters (ADCs) is presented, in which the 1.5-bit/stage ADC quantify domain is extended from a three-domain to a five-domain. This algorithm is designed for high speed and low comparator accuracy application. The comparator offset correction ability is improved. This new approach also promises significant improvements to the spurious-free dynamic range (SFDR), the total harmonic distortion (THD), the signal-to-noise ratio (SNR) and the minor analog and digital circuit modifications. Behavioral simulation results are presented to demonstrate the effectiveness of the algorithm, in which all absolute values of comparator offsets are set to |3Vref/8|. SFDR, THD and SNR are improved, from 34.62-dB, 34.63-dB and 30.33-dB to 60.23-dB, 61.14-dB and 59.35-dB, respectively, for a 10-bit pipeline ADC.

Conformal Wavelet Finite-difference Time-domain Algorithm for Analysis of Milimeter Wave Attenuation on Coplanar Waveguide

Addressed is the calculation of millimeter wave attenuation on coplanar waveguide(CPW). A novel conformal wavelet finite-difference time-domain(CWFDTD) algorithm is proposed with emphasis on its application in calculation of millimeter wave attenuation on CPW, which is the combination of conformal algorithm dealing with the deformed cell with Wavelet-FDTD using multi-resolution analysis(MRA). Derived is the difference formulation for multi-resolution time domain(MRTD) based on Daubechies wavelets, and also given is the stability conditions for wavelet-FDTD algorithm. To validate its accuracy and efficiency, this novel method is applied to calculate the millimeter wave attenuation on lithium niobate CPW. Numerical results demonstrate that this new CWFDTD algorithm has the same accuracy with the conformal finite-difference time-domain(CFDTD) and conformal finite-difference time-domain based on alternating-direction implicit method(ADI-CFDTD), but saves computational time and computer memory.

分布式软件定义网络中多域流量工程的路由优化方法

针对分布式软件定义网络(software-defined networking,SDN)中流量管理调度不均衡的流量工程问题,提出一种基于负载均衡的多控制域流量路由优化的解决方案。首先分析控制消息流量的组成、域内通信及域间通信规则;然后基于4种控制消息定义控制链路流量的构成,明确链路承载流量分为控制消息流量和业务流量,建立平衡控制器负载和最小化最大链路利用率的优化模型;最后基于域内通信和域间通信提出两层路由算法。为提高模型求解精度,进一步提出改进离散萤火虫算法求解最优路由。结合ABILENE网络和GEANT网络,分析控制消息流量、控制器负载和链路负载等评价指标。实验结果表明,优化模型能有效实现控制器和链路负载均衡,控制消息流量是流量工程重要组成部分。相比集中控制模式,扁平分布式控制模式的平均控制器负载降低47.3%,最大链路利用率相差不超过15%。

基于模型驱动的密码算法可视化开发平台研究

针对密码算法开发平台普适性差、无法跨平台的问题,本文采用模型驱动实现密码算法开发的方法,设计了一种基于模型驱动的密码算法可视化开发平台,提出了一种基于模型驱动的密码算法开发的领域语言—MCL密码元语言;实现了基于模型的代码生成器和代码映射器.实验证明,该开发平台仅需要开发者拖拽图形块的操作就可以实现密码算法模型的建立,然后平台可以根据建立的密码算法模型生成不同编程环境下的代码.平台实现了C和python的代码映射器模块,密码算法模型可快速映射为C、python代码.平台有较好的实用性,开发者的密码算法实现过程简洁、高效,不同编程环境下的代码均可以通过平台自动生成,提高了密码算法实现的跨平台性.

认知域作战主要样式演进与发展趋势

为把握认知域作战发展规律和作战机理,系统梳理其主要样式和演进规律。最初样式为以谋略为核心的攻心战,具有道义优势、关键节点和攻心伐谋制胜等特征;在大众传媒的推动下,发展为以宣传为核心的舆论战,制胜机理是宣传主导、媒介依托和技术赋能等;社交媒体等网络平台的出现,推动以算法为核心的算法认知战成为主要样式,“算法+谋略”是核心支撑、“算法+内容”是关键因子、“算法+平台”是重要支撑。据此,归纳出认知域作战关涉意识形态叙事、全面融入混合战争、消弭平战军民界限、凸显科技赋能优势等发展趋势。

用户恶意跨域数据安全加密共享算法仿真

在跨域数据共享场景下,涉及到多个组织或多个域的用户参与,为了保证数据安全,避免隐私信息泄露,提出了支持恶意用户追踪的跨域数据安全共享算法。将基于密文策略的属性基加密方法与白盒追踪算法和黑盒追踪算法结合。设计恶意用户追踪机制,实现对恶意用户的有效追踪。将对称加密算法和非对称加密算法相结合,生成公钥、私钥和密钥,对数据展开加解密处理,实现跨域数据安全共享。实验结果表明,所提算法的数据安全共享效果较高,在不同实验环境下均能够保持较低的内存,且信息熵较高,能够确保数据的安全性。

基于影响矩阵和精英遗传算法的斜拉桥索力优化

由于传统索力优化方法不能自动优化和兼顾全桥结构性能,以及与智能优化算法相结合后存在计算量大、耗时长、效率低和收敛速度慢等缺点,以Ansys和Matlab分别作为结构计算器和主控程序,以最小弯矩能为控制目标,将影响矩阵和精英保留策略引入到遗传算法中,实现成桥阶段的索力优化.该方法能够同时兼顾主梁与主塔的受力特性,而且影响矩阵的应用可以解决每一代都需要有限元评估的问题,大大减少了计算量.与传统的影响矩阵法相比,所提方法在吸取影响矩阵法优点的基础上,还考虑参数迭代过程,可在结构的关键截面添加特殊的约束要求,使得优化过程更加符合实际,而精英保留策略的引入可以提高进化迭代收敛的速度与进化过程的稳定性.最后,通过一个实际工程应用验证了所提方法的可行性.

基于优化变分模态分解的混凝土浅层空洞病害识别

针对开放环境下混凝土空洞病害检测的病害特征识别中噪声干扰、成分识别问题进行了研究,提出了基于优化变分模态分解(improved variational mode decomposition,IVMD)与自由振动衰减速度的混凝土浅层病害声振信号识别方法。该研究建立了混凝土浅层空洞病害的理论模型,仿真了不同工况下的病害特征频率及其变化规律;提出了基于IVMD的信号分解方法,设计了基于Tent混沌与柯西变异优化的麻雀搜索算法联合搜索变分模态分解的关键参数k和α,在最佳分解的基础上提出了基于自相关函数图形、相关系数、衰减系数与频域分布情况的浅层空洞病害本征模态函数(intrinsic mode function,IMF)识别方法;选取幅值衰减评估了特征IMF的衰减速度,得出了基于振动衰减特征的空洞病害识别方法;通过预埋病害模型试验对比分析,验证了所提方法的有效性。研究结果表明,基于IVMD的分解方法能够有效降低噪声及其他成分的干扰,提高空洞病害识别精度和准确度。

基于字符和词特征融合的恶意域名检测

针对现有恶意域名检测方法对域名生成算法(domain generation algorithm, DGA)随机产生的恶意域名检测性能不高,且对由随机单词组成的恶意域名检测效果较差的问题,提出一种基于字符和词特征融合的恶意域名检测算法(cha-racter and word network, CWNet)。利用并行卷积神经网络分别提取域名中字符和词的特征;将两种特征进行拼接,构造成融合特征;利用Softmax函数实现合法域名与恶意域名的检测。实验结果表明,该算法可以提升对恶意域名的检测能力,对更具挑战性的恶意域名家族的检测准确率提升效果更为明显。

基于空海异构无人平台的水下目标搜索与跟踪

海上异构无人系统可有效提高复杂任务的完成效率。文中采用自主水下航行器(AUV)和无人机(UAV)来完成近海海域内未知水下目标的搜索与跟踪任务。首先,描述了水下目标搜索跟踪任务,将任务过程分为目标搜索和目标跟踪阶段,2个阶段的目标分别是使AUV&UAV总搜索空间最大化以及AUV与水下目标的末端位置误差最小;然后,建立AUV&UAV跨域协同搜索模型,并设定模型中AUV和UAV探测范围和通信距离等约束条件;最后,在跨域协同搜索与路径跟踪规划中,基于传统粒子群算法,加入自适应学习因子调控策略和精英保存策略,生成搜索与跟踪路径。仿真实验表明,采用改进粒子群优化算法的AUV&UAV异构无人系统能够更高效地完成水下目标搜索与跟踪任务。

多元化渐进域迁移弱监督实时目标检测

针对像素级自适应较大的图像翻译偏差,特征级自适应的源偏判别风险以及弱监督学习无法兼顾检测准确性和实时性等问题,提出了多元化域移位器和伪边界框生成器以逐步调整预训练模型,在像素级与特征级渐进完成自适应的域迁移框架。通过域移位器从源域生成多样化的中间域图像调整检测模型以弥合域差距,减小图像翻译偏差。将中间域作为监督的源域,并结合目标域中的图像级标签生成伪标注图像调整检测模型以改善源偏判别性。基于SSD算法构建与域迁移框架相匹配的实时目标检测器,实现弱监督条件下的实时目标检测。在PASCAL VOC迁移至Clipart1k等数据集上的mAP优于现有方法0.4%~4.7%,检测速度为32 FPS~47 FPS,提高准确率的同时满足了实时检测的要求,具有更优越的迁移检测性能。

基2-FFT输入分级截断算法在频域合成孔径超声成像中的研究

为提高超声频域成像算法的计算速度,提出一种应用于超声频域成像算法的基2-FFT输入分级截断算法。首先,借助于COMSOL多物理场仿真软件,建立钢件中含有孔缝缺陷的有限元模型进行声场仿真。仿真结果得到关于缺陷的回波信号,并通过PSM算法对频域内声场进行重建,得到成像区域的聚焦图像,和原始仿真信号的B扫图像相比效果更加直观且成像质量更好,验证了PSM算法的可行性。然后为了避免超声频域成像算法中二维傅里叶变换的冗余计算,进一步提出了支持任意非0值输入的基2-FFT输入分级截断算法。实验结果证明,基2-FFT输入分级截断算法比标准基2-FFT算法快27%,超声频域算法成像速度提高13%。

多机器人协同路径的时域协作-势场A*规划

为了减小多机器人协同工作路径长度并提高路径平滑度,提出了基于时域协作-势场A*算法的多机器人协同规划方法。建立了机器人工作环境的栅格模型,分析了传统A*算法辅助信息不充分的问题。为了充分利用环境中的障碍物和目标点位置等先验信息,基于势场法将障碍物和目标点信息引入到A*算法辅助信息中,提出了基于势场A*算法的单机器人路径规划方法。使用三维时空图代替二维平面图,可以有效判断出多机器人碰撞问题,并根据碰撞类型制定了避撞策略。经验证,势场A*算法规划的路径长度和平滑度均优于传统A*算法、文献[11]蚁群算法;在多机器人协同路径规划中,在规划出各机器人最优路径基础上,可以有效解决机器人之间的碰撞问题。实验结果验证了时域协作-势场A*算法在多机器人协同路径规划中的有效性和优越性。