水声定位系统在海洋工程中的应用

以海洋资源的勘探与开发为主要目的的大洋勘探、海洋开发以及海洋工程中,广泛需要声学定位系统提供水下定位服务。以水声定位技术与系统为关注对象,介绍了水声定位系统的国内外现状、技术发展趋势,以及水声定位系统在海洋油气开发、海底矿石开采、未来海洋空间站以及海底打捞、勘探等作业中的应用需求,并对影响水声定位系统性能的因素进行了分析总结。     

一种非高斯随机振动过程数值模拟方法

目的 考虑真实随机振动的非高斯特性,提出一种根据已知信息生成与其相符的非高斯随机振动过程的数值模拟方法。方法 基于均值、方差、偏斜度、峭度及功率谱密度函数（或自相关函数）等约束条件,对非高斯随机振动进行模拟。根据功率谱获取非高斯过程的自相关矩阵;通过Hermite多项式的正交性质和多项式混沌展开方法推导出的公式,构造满足标准正态分布随机过程的协方差矩阵,并对其进行谱分解和主成分分析;最后,利用Karhunen-Loeve展开和多项式混沌展开来表示所模拟的非高斯振动过程。结果 随着采样点个数的增加,实测数据与模拟数据之间的误差越来越小,该方法具有较好的模拟精度。结论 应用多项式混沌展开、Karhunen-Loeve展开以及蒙特卡洛等方法,可生成非高斯随机振动过程,并得到准确有效的各项统计参数模拟值。     

高斯与非高斯随机振动对洗护产品包装的影响

目的 研究高斯激振力和非高斯激振力的随机振动对商品包装的影响差异,提供随机振动试验方法和参数,并对商品运输包装设计方案提供优化建议。方法 利用科学计量方法研究随机振动技术的发展态势。通过增大峭度的方法进行非高斯激振模拟随机振动试验。研究随机振动强度通过功率谱密度和疲劳损伤的表达,以及随机振动试验时间与疲劳损伤的表达关系。结果 电商渠道销售通过快递配送的洗洁精商品包裹优先采用ISTA 3A—2018 Packaged-Products for Parcel Delivery System Shipment 70 kg(150 lb) or less。使用Over-The-Road Trailer图谱和Pick-up and Delivery Vehicle图谱进行随机振动试验,通过加载峭度进行加速模拟试验和加强模拟试验。结论 在洗洁精商品包裹加载峭度为5、7、9条件下,能够复现实际配送中商品的货损。基于试验结果提出的包装设计修改方案在加强模拟试验条件下可以实现商品防护的功能。全渠道供应链配送商品包裹应采用高效、科学的实验室测试方法,为运输包装设计和验证提供方法和数据。     

Numerical discretization of stationary random processes

The increasing interest of the research community to the probabilistic analysis concerning the civil structures with space-variant properties points out the problem of achieving a reliable discretization of random processes (or random fields in a multi-dimensional domain). Given a discretization method, a continuous random process is approximated by a finite set of random variables. Its dimension affects significantly the accuracy of the approximation, in terms of the relevant properties of the continuous random process under investigation. The paper presents a discretization procedure based on the truncated Karhunen–Loève series expansion and the finite element method. The objective is to link in a rational way the number of random variables involved in the approximation to a quantitative measure of the discretization accuracy. The finite element method is applied to evaluate the terms of the series expansion when a closed form expression is not available. An iterative refinement of the finite element mesh is proposed in this paper, leading to an accurate random process discretization. The technique is tested with respect to the exponential covariance function, that enables a comparison with analytical expressions of the approximated properties of the random process. Then, the procedure is applied to the square exponential covariance functions, which is one of the most used covariance models in the structural engineering field. The comparison of the adaptive refinement of the discretization with a non-adaptive procedure and with the wavelet Galerkin approach allows to demonstrate the computational efficiency of the proposal within the framework of the Karhunen–Loève series expansion. A comparison with the Expansion Optimal Linear Estimation (EOLE) method is performed in terms of efficiency of the discretization strategy.     

Linear models for non-Gaussian processes and applications to linear random vibration

Linear models are finite sums of specified deterministic, continuous functions of time with random coefficients. It is shown that linear models provide (i) accurate approximations for real-valued non-Gaussian processes with continuous samples defined on bounded time intervals, (ii) simple solutions for linear random vibration problems with non-Gaussian input, and (iii) efficient techniques for selecting optimal designs from collections of proposed alternatives. Theoretical arguments and numerical examples are presented to establish properties of linear models, illustrate the construction of linear models, solve linear random vibration with non-Gaussian input, and propose an approach for optimal design of linear dynamic systems. It is shown that the proposed linear model provides an efficient tool for analyzing linear systems in non-Gaussian environment.     

两种非高斯海洋环境噪声统计模型分析

海洋环境噪声是影响声呐工作的主要因素之一,噪声模型的选取十分重要,普遍采用的高斯噪声模型在很多情况下存在局限性。引出两种非高斯噪声模型匹配实际非平稳的海洋环境噪声:广义自回归条件异方差模型(Generalized Autoregressive Conditional Heteroscedasticity,GARCH)和双模模型,通过分析两种噪声的概率密度分布函数,并与高斯模型噪声和实测海洋环境噪声比较得出两种噪声模型的适用性。GARCH(1,1)模型通过调节参数可以吻合大部分浅海和深海海洋环境噪声,双模模型则只对浅海某些情况存在适用性,而对深海吻合性较差。两种噪声模型的统计特性分析表明它们可以适用于高斯噪声模型存在局限的非平稳环境下。     

基于随机工程误差的磁悬浮列车轨道设计方法

 为在设计阶段即考虑随机工程误差对磁浮轨道曲线的影响,基于概率统计的观点,给出了考虑随机工程误差影响的磁悬浮轨道设计方法,建立了相关的分析公式,导出了设计曲线加工成败的判据.由此将工程过程与设计相结合,设计者在设计阶段即可预测轨道加工的成败,在设计磁悬浮列车轨道时综合考虑了经济性和可靠性.     

Reliability assessment models for dependent competing failure processes considering correlations between random shocks and degradations

This article develops reliability models for systems subject to two dependent competing failure processes, considering the correlation between additional damage size on degradation in soft failure process and stress magnitude of shock load in hard failure process, both of which are caused by the same kth random shock. The generalized correlative reliability assessment model based on copulas is proposed, which is then extended to three different shock patterns: (1) δ‐shock, (2) m‐shock, and (3) m‐run shocks. There are some statistical works to be introduced in reliability modeling, including data separation of total degradation amount, inferring the distribution of amount of aging continuous degradation at time t, and fitting copula to the specific correlation. The developed reliability models are demonstrated for an application example of a micro‐electro‐mechanical system.     

我国海洋水色遥感应用工程技术的新进展

介绍了近年来我国在海洋水色遥感应用工程技术方面的新进展,包括以应用为导向的关键技术研究和各类应用示范系统的开发等。针对当前海洋水色遥感业务化应用服务所面临的问题和一些急需解决的关键工程技术进行了分析和展望。     

A two-channel circuit for protecting a resonant gravitational antenna from correlated non-Gaussian interference

A modernized circuit with a noninertial nonlinear element, a whitening filter and a matched filter, connected in series-parallel, for suppressing correlated non-Gaussian interference at the output of a cryogenic resonant gravitational antenna is considered. The algorithm is based on the use of optimum processing of vector signals. __________ Translated from Metrologiya, No. 5, pp. 3–9, May, 2008.     

A translation model for non-stationary, non-Gaussian random processes

A model for simulation of non-stationary, non-Gaussian processes based on non-linear translation of Gaussian random vectors is presented. This method is a generalization of traditional translation processes that includes the capability of simulating samples with spatially or temporally varying marginal probability density functions. A formal development of the properties of the resulting process includes joint probability density function, correlation distortion and lower and upper bounds that depend on the target marginal distributions. Examples indicate the possibility of exactly matching a wide range of marginal pdfs and second order moments through a simple interpolating algorithm. Furthermore, the application of the method in simulating statistically inhomogeneous random media is investigated, using the specific case of binary translation with stationary and non-stationary target correlations.     

A proposal for a random Raman laser

The concept of a random Raman laser is investigated using a Monte Carlo simulation. Stimulated Raman scattering is taken into account by introducing an interaction between Raman and pump photons. Due to a lack of experimental data on the subject, validation of this model is accomplished via comparison to analytical solutions in the no scattering, no absorption limit. Random Raman lasing is discussed, and several distinctive properties are predicted.     

Cohesive crack propagation in a random elastic medium

The issue of generating non-Gaussian, multivariate and correlated random fields, while preserving the internal auto-correlation structure of each single-parameter field, is discussed with reference to the problem of cohesive crack propagation. Three different fields are introduced to model the spatial variability of the Young modulus, the tensile strength of the material, and the fracture energy, respectively. Within a finite-element context, the crack-propagation phenomenon is analyzed by coupling a Monte Carlo simulation scheme with an iterative solution algorithm based on a truly-mixed variational formulation which is derived from the Hellinger–Reissner principle. The selected approach presents the advantage of exploiting the finite-element technology without the need to introduce additional modes to model the displacement discontinuity along the crack boundaries. Furthermore, the accuracy of the stress estimate pursued by the truly-mixed approach is highly desirable, the direction of crack propagation being determined on the basis of the principal-stress criterion. The numerical example of a plain concrete beam with initial crack under a three-point bending test is considered. The statistics of the response is analyzed in terms of peak load and load–mid-deflection curves, in order to investigate the effects of the uncertainties on both the carrying capacity and the post-peak behaviour. A sensitivity analysis is preliminarily performed and its results emphasize the negative effects of not accounting for the auto-correlation structure of each random field. A probabilistic method is then applied to enforce the auto-correlation without significantly altering the target marginal distributions. The novelty of the proposed approach with respect to other methods found in the literature consists of not requiring the a priori knowledge of the global correlation structure of the multivariate random field.     

Cycle distribution and fatigue damage assessment in broad-band non-Gaussian random processes

The aim of the paper is to propose a method to assess the cycle distribution and the fatigue damage in stationary broad-band non-Gaussian processes; the method is a further development of an existing procedure proposed for Gaussian processes [Int J Fatigue 2002; 24(11)]. By introducing a suitable transformation, we link a non-Gaussian process to an underlying Gaussian one, for which we can estimate the cumulative distribution of counted cycles; the corresponding joint density for the non-Gaussian process is then derived. The analysis of time histories measured on Mountain-bikes in off-road tracks shows that the new method is able to correctly assess the distribution of ‘rainflow’ counted cycles taking into account the non-normality of the load.     

弹性-粘弹性复合结构系统的随机响应分析

本文建立在随机振动时域复模态分析的基础上,利用扩阶状态变量,将弹性－粘弹性复合结构系统的微分积分动力学方程变换成常规的状态方程,提出了一种分析弹性－粘弹性复合结构系统随机响应的方法,得到了弹性－粘弹性复合结构系统在平稳随机激励下响应相关函数矩阵的表达式,并对典型的平稳随机激励（平稳白噪声激励及平稳滤过白噪声激励）情形,进行了分析,得到了典型平稳随机激励下,弹性－粘弹性复合结构系统响应相关函数矩阵的复代数解析表达式。所提分析方法简便、易用,无论单自由度系统或多自由度系统均可适用。本文方法为粘弹性系统的随机响应分析提供了一条途径。     

Digital harmonic analysis of multicomponent random processes

Identification performance enhancement is considered for harmonic spectral components in the presence of wide-band stationary noise, with the solution based on the sign-function method of primary transformation and the use of random auxiliary signals. Experimental results are presented. __________ Translated from Izmeritel’naya Tekhnika, No. 4, pp. 22–26, April, 2006.     

On waves in a random micropolar conducting magneto-thermo-viscoelastic medium

Effects of random inhomogeneity on wave propagation in the interacting micropolar conducting magneto-generalized thermo-viscoelastic medium are studied. The couple stress theory relevant to micropolar solids is employed. The analysis is carried out under the smooth perturbation technique amenable to stochastic linear differential equations up to the second perturbation. The perturbing field has been assumed to be weakly conducting and weakly thermal. The generalized thermoelasticity has been used. Six different types of waves have been observed to propagate in the medium. The dispersion equations have been derived. Effects due to random variations of micropolar-elastic, conducting-electromagnetic and generalized thermo-visco-parameters have been computed. Effects of random heterogeneity of the conducting magnetic field are readily available up to first order perturbation. However effects of the generalized thermal field are discernible only in the domain of second order perturbation. Change of phase speed occurs on account of randomness. Attenuation coefficients for types of waves have been computed. A special type of generalized theromomechanical auto- and cross-correlation functions has been used to approximately measure effects of random variations of parameters. Uncoupled problem has been formulated for future investigations.     

涡旋光束通过非高斯随机粗糙面的场分布特性

基于角谱衍射理论,利用Johnson传递系统数值模拟非高斯粗糙面,研究了拉盖尔-高斯涡旋光束通过随机非高斯粗糙表面的场分布特性。在分析了非高斯粗糙面方向自相关长度、峰度、偏斜以及均方根粗糙度对涡旋光束场分布影响的基础上,研究了涡旋光束通过随机粗糙表面后光束光强分布变化时的均方根粗糙度取值范围,并通过实验,将实验数据与仿真结果进行了对比分析。结果表明:当非高斯粗糙面方向相关长度为20 mm,偏斜为0.001,峰度为6,均方根粗糙度大于0.12 mm时,拉盖尔-高斯光束透过随机表面的光强分布不再保持空心分布,对应的相位奇点消失。     

Frequency-based fatigue analysis of non-stationary switching random loads

The service loadings in real systems are not only random, but also non-stationary. The spectral methods based on a frequency-domain characterization of random loads, which have been used in alternative to classical time-domain approaches, cannot be applied to non-stationary loads, because the conventional spectral density spectrum is not able to capture the evolutionary frequency characteristics of non-stationary loads. This clearly restricts the applicability of the existing frequency-based methods only to loads which are stationary. At the same time, it is also very difficult to propose general models valid for all types of load non-stationarity encountered in practice. Therefore, a practical approach is to restrict the analysis to a specific class of non-stationary loads; in this work, we consider particular non-stationary loads (i.e. switching loads), which are piecewise stationary in their variance. A frequency-domain analysis of such loads is proposed, which is based on a combination of the frequency-based analysis of each adjacent stationary segment, which can be either Gaussian or non-Gaussian. Numerically simulated load histories, as well as loads measured on mountain bikes in special tracks, are analysed to validate the proposed methodology. The presented results also show the correlation between load non-stationarity and non-Gaussianity.     

Fatigue life prediction under wide band random loading

In this paper, a method for the high‐cycle fatigue life prediction of components subjected to gaussian, stationary, wide band random loading is presented. It allows the user to evaluate the fatigue life of components subjected to uniaxial stress states directly from the stress power spectral density (PSD), avoiding onerous simulations in time domain. The proposed method can be applied to random stress processes having PSD of any shape, and the fatigue life predictions obtained are more accurate than that provided by most of the frequency domain techniques proposed in literature.