Physics-constrained non-Gaussian probabilistic learning on manifolds

An extension of the probabilistic learning on manifolds (PLoM), recently introduced by the authors, has been presented: In addition to the initial data set given for performing the probabilistic learning, constraints are given, which correspond to statistics of experiments or of physical models. We consider a non-Gaussian random vector whose unknown probability distribution has to satisfy constraints. The method consists in constructing a generator using the PLoM and the classical Kullback-Leibler minimum cross-entropy principle. The resulting optimization problem is reformulated using Lagrange multipliers associated with the constraints. The optimal solution of the Lagrange multipliers is computed using an efficient iterative algorithm. At each iteration, the Markov chain Monte Carlo algorithm developed for the PLoM is used, consisting in solving an Itô stochastic differential equation that is projected on a diffusion-maps basis. The method and the algorithm are efficient and allow the construction of probabilistic models for high-dimensional problems from small initial data sets and for which an arbitrary number of constraints are specified. The first application is sufficiently simple in order to be easily reproduced. The second one is relative to a stochastic elliptic boundary value problem in high dimension.     

Probabilistic learning for modeling and quantifying model-form uncertainties in nonlinear computational mechanics

Recently, a novel nonparametric probabilistic method for modeling and quantifying model-form uncertainties in nonlinear computational mechanics was proposed. Its potential was demonstrated through several uncertainty quantification (UQ) applications in vibration analysis and nonlinear computational structural dynamics. This method, which relies on projection-based model order reduction to achieve computational feasibility, exhibits a vector-valued hyperparameter in the probability model of the random reduced-order basis and associated stochastic projection-based reduced-order model. It identifies this hyperparameter by formulating a statistical inverse problem, grounded in target quantities of interest, and solving the corresponding nonconvex optimization problem. For many practical applications, however, this identification approach is computationally intensive. For this reason, this paper presents a faster predictor-corrector approach for determining the appropriate value of the vector-valued hyperparameter that is based on a probabilistic learning on manifolds. It also demonstrates the computational advantages of this alternative identification approach through the UQ of two three-dimensional nonlinear structural dynamics problems associated with two different configurations of a microelectromechanical systems device.     

Diffusion maps-based surrogate modeling: An alternative machine learning approach

In this work, an alternative machine learning methodology is proposed, which utilizes nonlinear manifold learning techniques in the frame of surrogate modeling. Under the assumption that the solutions of a parametrized physical system lie on a low-dimensional manifold embedded in a high-dimensional Euclidean space, the goal is to unveil the manifold's intrinsic dimensionality and use it for the construction of a surrogate model, which will be used as a cost-efficient emulator of the high-dimensional physical system. To this purpose, a computational framework based on the diffusion maps algorithm is put forth herein, where a set of system solutions is used to identify the geometry of a low-dimensional space called the diffusion maps space. This space is completely described by a low-dimensional basis, which is constructed from the eigenvectors and eigenvalues of a diffusion operator on the data. The proposed approach exploits the diffusion maps space's reduced dimensionality for the construction of locally clustered interpolation schemes between the parameter space, the diffusion maps space, and the solution space, which are cheap to evaluate and highly accurate. This way, the need to formulate and solve the governing equations of the system is eliminated. In addition, a sampling methodology is proposed based on the metric of the diffusion maps space to efficiently sample the parameter space, thus ensuring the quality of the surrogate model. Even though it is exploited herein in the premises of uncertainty quantification, this methodology is applicable to any other problem type that depends on some parametric space (ie, optimization, sensitivity analysis, etc). In the numerical examples, it is shown that the proposed surrogate model is capable of high levels of accuracy, as well as significant computational gains.     

基于协同采样主动学习的恶意代码检测

研究了基于机器学习分类算法的恶意代码检测,考虑到目前主要采用传统分类方法对恶意代码进行分类识别,这些方法需要通过学习大量标记样本来获得精准的分类器模型,然而样本标记工作只有少数专家才能完成,导致标记样本往往不足,致使分类结果准确率不高,提出了一种基于协同采样的主动学习方法。运用这种学习方法,仅需少量标记样本即可有效识别出恶意代码。实验证明,相对于传统的恶意代码分类方法,该方法能够显著提升分类准确率和泛化性能。     

Probabilistic nonconvex constrained optimization with fixed number of function evaluations

A methodology is proposed for the efficient solution of probabilistic nonconvex constrained optimization problems with uncertain. Statistical properties of the underlying stochastic generator are characterized from an initial statistical sample of function evaluations. A diffusion manifold over the initial set of data points is first identified and an associated basis computed. The joint probability density function of this initial set is estimated using a kernel density model and an Itô stochastic differential equation (ISDE) constructed with this model as its invariant measure. This ISDE is adapted to fluctuate around the manifold yielding additional joint realizations of the uncertain parameters, design variables, and function values, which are obtained as solutions of the ISDE. The expectations in the objective function and constraints are then accurately evaluated without performing additional function evaluations. The methodology brings together novel ideas from manifold learning and stochastic Hamiltonian dynamics to tackle an outstanding challenge in stochastic optimization. Three examples are presented to highlight different aspects of the proposed methodology.     

Nonlinear magnetoquasistatic interface problem in a permanent-magnet machine with stochastic partial differential equation constraints

This study discusses an application of the stochastic collocation method for the solution of a nonlinear magnetoquasistatic interface problem that is constrained by a partial differential equation with random input data. Special attention is given to finding the robust design of a rotor and a stator of an electrical machine for the reduction of electromagnetic losses and a cogging torque under material uncertainties. For this reason, variations of material properties are modelled using the polynomial chaos expansion technique. To develop the domain derivative of a robust cost functional, the velocity method is applied with an adjoint technique. The utility and efficiency of the proposed method has been successfully demonstrated by applying it to the design of a permanent-magnet synchronous machine used in electric vehicles.     

基于机器学习算法的超声流量计使用中检验

为保证使用中超声流量计的准确度,基于随机森林算法,建立了超声流量计使用中检验预测分析模型。研究了超声流量计使用中检验程序。首先,获取超声流量计的信号质量数据、流态指标数据、以及计量性能数据;其次,采用随机森林算法对使用中超声流量计的流量偏差进行预测,预测值与真实值的偏差在0.76%以内,分析了影响使用中超声流量计测量准确度的各数据对超声流量计性能的影响程度;最后,对预测模型的不确定度进行分析,其扩展不确定度U=0.92%~0.22%(k=2)。     

Recommendation Algorithm Based on Probabilistic Matrix Factorization with Adaboost

A current problem in diet recommendation systems is the matching of food preferences with nutritional requirements, taking into account individual characteristics,such as body weight with individual health conditions, such as diabetes. Current dietary recommendations employ association rules, content-based collaborative filtering, and constraint-based methods, which have several limitations. These limitations are due to the existence of a special user group and an imbalance of non-simple attributes. Making use of traditional dietary recommendation algorithm researches, we combine the Adaboost classifier with probabilistic matrix factorization. We present a personalized dietrecommendation algorithm by taking advantage of probabilistic matrix factorization via Adaboost. A probabilistic matrix factorization method extracts the implicit factorsbetween individual food preferences and nutritional characteristics. From this, we can make use of those features with strong influence while discarding those with little influence. After incorporating these changes into our approach, we evaluated our algorithm’s performance. Our results show that our method performed better than others at matching preferred foods with dietary requirements, benefiting user health as a result. The algorithm fully considers the constraint relationship between users’ attributes and nutritional characteristics of foods. Considering many complex factors in our algorithm, the recommended food result set meets both health standards and users’ dietary preferences. A comparison of our algorithm with others demonstrated that our method offers high accuracy and interpretability.     

Crack detection of structures using modified extreme learning machine (MELM)

In this paper, crack detection and estimation method is presented in structures using modified extreme learning machine. For this purpose, extreme learning machine was modified using modified weights and biases. By using the first three frequencies and mode shapes as input, crack was detected as output. Performance of the proposed method was evaluated by using some numerical examples consisting of a simply supported beam, cantilever beam and fixed-simply supported beam. In addition, noise effect (3% noise level) on the measured frequencies and mode shapes have been investigated. In another work, a portal frame has been studied. The results indicated that the proposed method is effective and fast in crack detection and estimation of structures.     

Representation and problem solving with Distribution Envelope Determination (DEnv)

Distribution Envelope Determination (DEnv) is a method for computing the CDFs of random variables whose samples are a function of samples of other random variable(s), termed inputs. DEnv computes envelopes around these CDFs when there is uncertainty about the precise form of the probability distribution describing any input. For example, inputs whose distribution functions have means and variances known only to within intervals can be handled. More generally, inputs can be handled if the set of all plausible cumulative distributions describing each input can be enclosed between left and right envelopes. Results will typically be in the form of envelopes when inputs are envelopes, when the dependency relationship of the inputs is unspecified, or both. For example in the case of specific input distribution functions with unspecified dependency relationships, each of the infinite number of possible dependency relationships would imply some specific output distribution, and the set of all such output distributions can be bounded with envelopes. The DEnv algorithm is a way to obtain the bounding envelopes. DEnv is implemented in a tool which is used to solve problems from a benchmark set.     

基于机器学习的热导率预测模型研究

传统的理论研究、实验研究及计算仿真已无法满足科学家对新材料的探索与设计。数据驱动的机器学习算法对材料的筛选与性能预测有着推动作用。将机器学习算法应用到材料信息学,基于现有材料热导率数据集,建立机器学习热导率预测模型,通过交叉验证来对机器学习回归模型进行评估。利用机器学习算法建立描述符与热导率属性之间的映射模型,可用于大规模的材料筛选,从而指导实验研究。     

Interval spectral stochastic finite element analysis of structures with aggregation of random field and bounded parameters

This paper presents the study on non‐deterministic problems of structures with a mixture of random field and interval material properties under uncertain‐but‐bounded forces. Probabilistic framework is extended to handle the mixed uncertainties from structural parameters and loads by incorporating interval algorithms into spectral stochastic finite element method. Random interval formulations are developed based on K–L expansion and polynomial chaos accommodating the random field Young's modulus, interval Poisson's ratios and bounded applied forces. Numerical characteristics including mean value and standard deviation of the interval random structural responses are consequently obtained as intervals rather than deterministic values. The randomised low‐discrepancy sequences initialized particles and high‐order nonlinear inertia weight with multi‐dimensional parameters are employed to determine the change ranges of statistical moments of the random interval structural responses. The bounded probability density and cumulative distribution of the interval random response are then visualised. The feasibility, efficiency and usefulness of the proposed interval spectral stochastic finite element method are illustrated by three numerical examples. Copyright © 2016 John Wiley & Sons, Ltd.     

Non‐Gaussian positive‐definite matrix‐valued random fields with constrained eigenvalues: Application to random elasticity tensors with uncertain material symmetries

This paper is devoted to the construction of a class of prior stochastic models for non‐Gaussian positive‐definite matrix‐valued random fields. The proposed class allows the variances of selected random eigenvalues to be specified and exhibits a larger number of parameters than the other classes previously derived within a nonparametric framework. Having recourse to a particular characterization of material symmetry classes, we then propose a mechanical interpretation of the constraints and subsequently show that the probabilistic model may allow prescribing higher statistical fluctuations in given directions. Such stochastic fields turn out to be especially suitable for experimental identification under material symmetry uncertainties, as well as for the development of computational multi‐scale approaches where the randomness induced by fine‐scale features may be taken into account. We further present a possible strategy for inverse identification, relying on the sequential solving of least‐square optimization problems. An application is finally provided. Copyright © 2011 John Wiley & Sons, Ltd.     

An extended stochastic pseudo-spectral Galerkin finite element method (XS-PS-GFEM) for elliptic equations with hybrid uncertainties

Nouy and Clement introduced the stochastic extended finite element method to solve linear elasticity problem defined on random domain. The material properties and boundary conditions were assumed to be deterministic. In this work, we extend this framework to account for multiple independent input uncertainties, namely, material, geometry, and external force uncertainties. The stochastic field is represented using the polynomial chaos expansion. The challenge in numerical integration over multidimensional probabilistic space is addressed using the pseudo-spectral Galerkin method. Thereafter, a sensitivity analysis based on Sobol indices using the derived stochastic extended Finite Element Method solution is presented. The efficiency and accuracy of the proposed novel framework against conventional Monte Carlo methods is elucidated in detail for a few one and two dimensional problems.     

基于随机卷积特征和集成超限学习机的快速SAR目标识别

深度卷积神经网络在目标检测与识别等方面表现出了优异性能,但将其用于SAR目标识别时,较少的训练样本和深度模型的优化设计是必须解决的两个问题。本文设计了一种结合二维随机卷积特征和集成超限学习机的SAR目标识别算法。首先,随机生成具有不同宽度的二维卷积核,对输入图像进行卷积与池化操作,提取随机卷积特征向量。其次,为提高分类器的泛化能力,并降低训练时间,基于集成学习思想对提取的卷积特征进行随机采样,然后采用超限学习机训练基分类器。最后,通过投票表决法对基分类器的分类结果进行集成。采用MSTAR数据集进行了SAR目标识别实验,实验结果表明,由于采用的超限学习机具有快速训练能力,训练时间降低了数十倍,在无需进行数据增强的情况下,分类精度与采用数据增强和多层卷积神经网络的深度学习算法相当。提出的算法具有实现简单、需要调整参数少等优点,采用集成学习思想提高了分类器的泛化能力。

     

Research on scheduling with job-dependent learning effect and convex resource-dependent processing times

We study resource allocation scheduling with job-dependent learning effect on a single machine with or without due date assignment considerations. For a convex resource processing time function, we provide a polynomial time algorithm to find the optimal job sequence, and resource allocations that minimise the schedule criterion (the total compression cost) subject to the constraint that the total compression cost (the schedule criterion) is less than or equal to a fixed amount.     

Particular Cases of the Calculation of the Errors (Uncertainties) of the Results of Direct Measurements with Multiple Observations

It is shown that an expression for the total error as defined in GOST 8.207-76 of the corrected results of a measurement possesses an anomaly when this error is less than one of its components, and that a similar anomaly occurs for the expanded uncertainty as defined in MI 2552-99. The error of uncorrected results of a measurement whose random component is distributed according to different laws is compared with calculations utilizing RD 50-453-84 and MI 1788-87.     

基于二值随机森林的非均匀光照QR码重构算法

目的 现实生活QR码在识别过程中,易受到非均匀光照因素的影响,导致QR码无法识别,为此提出一种基于二值随机森林的QR码像素值重构算法。方法 依据QR码图像的双峰特点和梯度值相等的特性,用于提取非均匀光照下受损QR码局部像素特征,并利用随机森林的分类方法确定QR码局部矩阵中间单个像素值,逐步实现受损QR码所有像素值的重构恢复。结果 实验表明与其他方法相比,该算法模型能够很好地利用局部特征提取QR码的真实像素值,并对受损QR码图像进行恢复,实验结果图像均具有较高水平。结论 采用基于二值随机森林的QR码重构算法,能够很好地处理因非均匀光照而导致的识别出错问题,并可以广泛应用于生活中的QR码识别过程,具有较强的实用性。     

The state-of-the-art on Intellectual Property Analytics (IPA): A literature review on artificial intelligence,machine learning and deep learning methods for analysing intellectual property (IP) data

Big data is increasingly available in all areas of manufacturing and operations, which presents an opportunity for better decision making and discovery of the next generation of innovative technologies. Recently, there have been substantial developments in the field of patent analytics, which describes the science of analysing large amounts of patent information to discover trends. We define Intellectual Property Analytics (IPA) as the data science of analysing large amount of IP information, to discover relationships, trends and patterns for decision making. In this paper, we contribute to the ongoing discussion on the use of intellectual property analytics methods, i.e artificial intelligence methods, machine learning and deep learning approaches, to analyse intellectual property data. This literature review follows a narrative approach with search strategy, where we present the state-of-the-art in intellectual property analytics by reviewing 57 recent articles. The bibliographic information of the articles are analysed, followed by a discussion of the articles divided in four main categories: knowledge management, technology management, economic value, and extraction and effective management of information. We hope research scholars and industrial users, may find this review helpful when searching for the latest research efforts pertaining to intellectual property analytics.