我们考虑识别大规模线性和稳定的动态系统,其输出可能是许多相关输入的结果。因此,严重的疾病可能会影响估计问题。当通过许多子单元的互连给出的复杂物理系统进行建模时,这种情况通常是一种情况,在这些子单元的互连中可以遇到反馈和代数循环。我们制定了一种基于贝叶斯正则化的策略,其中任何脉冲响应都被建模为实现零均值高斯过程的策略。稳定的样条协方差用于包括有关脉冲反应的平滑指数衰减的信息。然后,我们设计了一种新的马尔可夫链蒙特卡洛方案,该方案涉及共线性,并能够有效地重建冲动反应的后部。它基于Gibbs采样的变化,该变体基于影响不同输入的截然性水平更新参数空间的重叠块。包括数值实验以测试数百个脉冲响应形成系统的方法的好处,并且输入相关性可能非常高。
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为了识别动态网络中嵌入的系统(模块),必须制定一个多输入估计问题,该问题需要测量某些节点并将其作为预测输入。但是,由于传感器选择和放置问题,在许多实际情况下,其中一些节点可能无法测量。这可能会导致目标模块的偏差估计。此外,与多输入结构相关的识别问题可能需要确定实验者不特别感兴趣的大量参数,并且在大型网络中的计算复杂性增加。在本文中,我们通过使用数据增强策略来解决这些问题,该策略使我们能够重建缺失的节点测量并提高估计目标模块的准确性。为此,我们使用基于正规化的基于内核的方法和近似推理方法开发了系统识别方法。为感兴趣的模块保留一个参数模型,我们将其他模块作为高斯过程(GP)建模,并用所谓的稳定样条核给出的内核。经验贝叶斯(EB)方法用于估计目标模块的参数。相关的优化问题是使用预期最大化(EM)方法来解决的,在该方法中,我们采用马尔可夫链蒙特卡洛(MCMC)技术来重建未知的缺失节点信息和网络动力学。动态网络示例上的数值模拟说明了开发方法的电势。
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网络推断已在系统生物学和社会科学等多个领域进行了广泛的研究。学习网络拓扑和内部动力学对于了解复杂系统的机制至关重要。特别是,稀疏拓扑和稳定的动态是许多现实世界连续时间(CT)网络的基本特征。鉴于通常只有一组节点能够观察到,在本文中,我们认为线性CT系统可以描绘网络,因为它们可以通过传输函数对未测量的节点进行建模。另外,测量值往往很嘈杂,并且采样频率较低和不同。因此,我们考虑CT模型,因为离散的时间近似通常需要细粒度的测量和均匀的采样步骤。开发的方法应用了源自线性随机微分方程(SDE)的动力结构函数(DSF)来描述测量节点的网络。一种数值抽样方法,即预处理的曲柄 - 尼科尔森(PCN),用于完善粗粒轨迹以提高推理精度。开发方法的收敛属性对数据源的维度具有鲁棒性。蒙特卡洛模拟表明,开发的方法优于最先进的方法,包括稀疏贝叶斯学习(GSBL),宾果游戏,基于内核的方法,dyngenie3,genie3和arni。模拟包括随机和环网,以及合成生物网络。这些是具有挑战性的网络,表明可以在广泛的环境中应用开发的方法,例如基因调节网络,社交网络和通信系统。
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最近,经验可能性已在贝叶斯框架下广泛应用。马尔可夫链蒙特卡洛(MCMC)方法经常用于从感兴趣参数的后验分布中采样。然而,可能性支持的复杂性,尤其是非凸性的性质,在选择适当的MCMC算法时建立了巨大的障碍。这种困难限制了在许多应用中基于贝叶斯的经验可能性(贝叶赛)方法的使用。在本文中,我们提出了一个两步的大都会黑斯廷斯算法,以从贝耶斯后期进行采样。我们的建议是在层次上指定的,其中确定经验可能性的估计方程用于根据其余参数的建议值提出一组参数的值。此外,我们使用经验可能性讨论贝叶斯模型的选择,并将我们的两步大都会黑斯廷斯算法扩展到可逆的跳跃马尔可夫链蒙特卡洛手术程序,以便从最终的后验中采样。最后,提出了我们提出的方法的几种应用。
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A framework for creating and updating digital twins for dynamical systems from a library of physics-based functions is proposed. The sparse Bayesian machine learning is used to update and derive an interpretable expression for the digital twin. Two approaches for updating the digital twin are proposed. The first approach makes use of both the input and output information from a dynamical system, whereas the second approach utilizes output-only observations to update the digital twin. Both methods use a library of candidate functions representing certain physics to infer new perturbation terms in the existing digital twin model. In both cases, the resulting expressions of updated digital twins are identical, and in addition, the epistemic uncertainties are quantified. In the first approach, the regression problem is derived from a state-space model, whereas in the latter case, the output-only information is treated as a stochastic process. The concepts of It\^o calculus and Kramers-Moyal expansion are being utilized to derive the regression equation. The performance of the proposed approaches is demonstrated using highly nonlinear dynamical systems such as the crack-degradation problem. Numerical results demonstrated in this paper almost exactly identify the correct perturbation terms along with their associated parameters in the dynamical system. The probabilistic nature of the proposed approach also helps in quantifying the uncertainties associated with updated models. The proposed approaches provide an exact and explainable description of the perturbations in digital twin models, which can be directly used for better cyber-physical integration, long-term future predictions, degradation monitoring, and model-agnostic control.
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从降压和嘈杂的测量值(例如MRI和低剂量计算机断层扫描(CT))中重建图像是数学上不良的反问题。我们提出了一种基于期望传播(EP)技术的易于使用的重建方法。我们将蒙特卡洛(MC)方法,马尔可夫链蒙特卡洛(MCMC)和乘数(ADMM)算法的交替方向方法纳入EP方法,以解决EP中遇到的棘手性问题。我们在复杂的贝叶斯模型上演示了图像重建的方法。我们的技术应用于伽马相机扫描中的图像。我们仅将EPMC,EP-MCMC,EP-ADMM方法与MCMC进行比较。指标是更好的图像重建,速度和参数估计。在真实和模拟数据中使用伽马相机成像进行的实验表明,我们提出的方法在计算上比MCMC昂贵,并且产生相对更好的图像重建。
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多项式概率贝叶斯添加剂回归树(MPBART)框架是由Kindo等人提出的。 (KD),与BART的多项式概率(MNP)模型中的潜在实用程序近似(Chipman等人,2010年)。与多项式逻辑模型相比,MNP不假定独立的替代方案,并且可以通过多元高斯分布式潜在实用程序指定替代方案之间的相关结构。我们介绍了两种新算法,以拟合MPBART,并表明我们的提案的理论混合速率相等或优于KD中现有的算法。通过模拟,我们探讨了方法对参考水平的选择,结果频率的不平衡以及实用程序误差项的先前超参数的规格。这项工作是由基于电子健康记录(EHR)从肯尼亚提供医疗保健(AMPATH)的学术模型中的电子健康记录(EHR)来实现后验预测分布来在HIV阳性患者中进行护理的后验预测分配的动机。在应用程序和模拟中,与KD相比,在MCMC收敛速率和后验预测精度方面,我们使用建议的性能更好。
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我们引入了一种新的经验贝叶斯方法,用于大规模多线性回归。我们的方法结合了两个关键思想:(i)使用灵活的“自适应收缩”先验,该先验近似于正常分布的有限混合物,近似于正常分布的非参数家族; (ii)使用变分近似来有效估计先前的超参数并计算近似后期。将这两个想法结合起来,将快速,灵活的方法与计算速度相当,可与快速惩罚的回归方法(例如Lasso)相当,并在各种场景中具有出色的预测准确性。此外,我们表明,我们方法中的后验平均值可以解释为解决惩罚性回归问题,并通过直接解决优化问题(而不是通过交叉验证来调整)从数据中学到的惩罚函数的精确形式。 。我们的方法是在r https://github.com/stephenslab/mr.ash.ash.alpha的r软件包中实现的
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Surrogate models have shown to be an extremely efficient aid in solving engineering problems that require repeated evaluations of an expensive computational model. They are built by sparsely evaluating the costly original model and have provided a way to solve otherwise intractable problems. A crucial aspect in surrogate modelling is the assumption of smoothness and regularity of the model to approximate. This assumption is however not always met in reality. For instance in civil or mechanical engineering, some models may present discontinuities or non-smoothness, e.g., in case of instability patterns such as buckling or snap-through. Building a single surrogate model capable of accounting for these fundamentally different behaviors or discontinuities is not an easy task. In this paper, we propose a three-stage approach for the approximation of non-smooth functions which combines clustering, classification and regression. The idea is to split the space following the localized behaviors or regimes of the system and build local surrogates that are eventually assembled. A sequence of well-known machine learning techniques are used: Dirichlet process mixtures models (DPMM), support vector machines and Gaussian process modelling. The approach is tested and validated on two analytical functions and a finite element model of a tensile membrane structure.
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现代深度学习方法构成了令人难以置信的强大工具,以解决无数的挑战问题。然而,由于深度学习方法作为黑匣子运作,因此与其预测相关的不确定性往往是挑战量化。贝叶斯统计数据提供了一种形式主义来理解和量化与深度神经网络预测相关的不确定性。本教程概述了相关文献和完整的工具集,用于设计,实施,列车,使用和评估贝叶斯神经网络,即使用贝叶斯方法培训的随机人工神经网络。
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通过变分贝叶斯近似来提出框架,用于拟合逆问题模型。与标准马尔可夫链蒙特卡罗方法相比,这种方法可确保对广泛的应用,良好的应用,良好的精度性能和降低的模型拟合时间来灵活。我们描述的变分贝叶斯的消息传递和因子图片段方法促进了简化的近似推理算法的实现,并形成软件开发的基础。这种方法允许将许多响应分布和惩罚抑制到逆问题模型中。尽管我们的工作被赋予了一个和二维响应变量,但我们展示了一个基础设施,其中还可以导出基于变量之间的无效弱交互的有效算法更新,以便在更高维度中的逆问题。通过生物医学和考古问题激励的图像处理应用程序作为图示。
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In a fissile material, the inherent multiplicity of neutrons born through induced fissions leads to correlations in their detection statistics. The correlations between neutrons can be used to trace back some characteristics of the fissile material. This technique known as neutron noise analysis has applications in nuclear safeguards or waste identification. It provides a non-destructive examination method for an unknown fissile material. This is an example of an inverse problem where the cause is inferred from observations of the consequences. However, neutron correlation measurements are often noisy because of the stochastic nature of the underlying processes. This makes the resolution of the inverse problem more complex since the measurements are strongly dependent on the material characteristics. A minor change in the material properties can lead to very different outputs. Such an inverse problem is said to be ill-posed. For an ill-posed inverse problem the inverse uncertainty quantification is crucial. Indeed, seemingly low noise in the data can lead to strong uncertainties in the estimation of the material properties. Moreover, the analytical framework commonly used to describe neutron correlations relies on strong physical assumptions and is thus inherently biased. This paper addresses dual goals. Firstly, surrogate models are used to improve neutron correlations predictions and quantify the errors on those predictions. Then, the inverse uncertainty quantification is performed to include the impact of measurement error alongside the residual model bias.
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Hierarchical Bayesian Poisson regression models (HBPRMs) provide a flexible modeling approach of the relationship between predictors and count response variables. The applications of HBPRMs to large-scale datasets require efficient inference algorithms due to the high computational cost of inferring many model parameters based on random sampling. Although Markov Chain Monte Carlo (MCMC) algorithms have been widely used for Bayesian inference, sampling using this class of algorithms is time-consuming for applications with large-scale data and time-sensitive decision-making, partially due to the non-conjugacy of many models. To overcome this limitation, this research develops an approximate Gibbs sampler (AGS) to efficiently learn the HBPRMs while maintaining the inference accuracy. In the proposed sampler, the data likelihood is approximated with Gaussian distribution such that the conditional posterior of the coefficients has a closed-form solution. Numerical experiments using real and synthetic datasets with small and large counts demonstrate the superior performance of AGS in comparison to the state-of-the-art sampling algorithm, especially for large datasets.
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We propose a novel model agnostic data-driven reliability analysis framework for time-dependent reliability analysis. The proposed approach -- referred to as MAntRA -- combines interpretable machine learning, Bayesian statistics, and identifying stochastic dynamic equation to evaluate reliability of stochastically-excited dynamical systems for which the governing physics is \textit{apriori} unknown. A two-stage approach is adopted: in the first stage, an efficient variational Bayesian equation discovery algorithm is developed to determine the governing physics of an underlying stochastic differential equation (SDE) from measured output data. The developed algorithm is efficient and accounts for epistemic uncertainty due to limited and noisy data, and aleatoric uncertainty because of environmental effect and external excitation. In the second stage, the discovered SDE is solved using a stochastic integration scheme and the probability failure is computed. The efficacy of the proposed approach is illustrated on three numerical examples. The results obtained indicate the possible application of the proposed approach for reliability analysis of in-situ and heritage structures from on-site measurements.
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非线性动态系统的识别仍然是整个工程的重大挑战。这项工作提出了一种基于贝叶斯过滤的方法,以提取和确定系统中未知的非线性项的贡献,可以将其视为恢复力表面类型方法的替代观点。为了实现这种识别,最初将非线性恢复力的贡献作为高斯过程建模。该高斯过程将转换为状态空间模型,并与系统的线性动态组件结合使用。然后,通过推断过滤和平滑分布,可以提取系统的内部状态和非线性恢复力。在这些状态下,可以构建非线性模型。在模拟案例研究和实验基准数据集中,该方法被证明是有效的。
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潜在位置网络模型是网络科学的多功能工具;应用程序包括集群实体,控制因果混淆,并在未观察的图形上定义前提。估计每个节点的潜在位置通常是贝叶斯推理问题的群体,吉布斯内的大都市是最流行的近似后分布的工具。然而,众所周知,GIBBS内的大都市对于大型网络而言是低效;接受比计算成本昂贵,并且所得到的后绘高度相关。在本文中,我们提出了一个替代的马尔可夫链蒙特卡罗战略 - 使用分裂哈密顿蒙特卡罗和萤火虫蒙特卡罗的组合定义 - 利用后部分布的功能形式进行更有效的后退计算。我们展示了这些战略在吉布斯和综合网络上的其他算法中优于大都市,以及学区的教师和工作人员的真正信息共享网络。
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我们考虑贝叶斯逆问题,其中假设未知状态是具有不连续结构的函数先验。介绍了基于具有重型重量的神经网络输出的一类现有分布,其具有关于这种网络的无限宽度限制的现有结果。理论上,即使网络宽度是有限的,我们也显示来自这种前导者的样本具有所需的不连续性,使得它们适合于边缘保留反转。在数值上,我们考虑在一个和二维空间域上定义的解卷积问题,以说明这些前景的有效性;地图估计,尺寸 - 鲁棒MCMC采样和基于集合的近似值用于探测后部分布。点估计的准确性显示出超过从非重尾前沿获得的那些,并且显示不确定性估计以提供更有用的定性信息。
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We present the GPry algorithm for fast Bayesian inference of general (non-Gaussian) posteriors with a moderate number of parameters. GPry does not need any pre-training, special hardware such as GPUs, and is intended as a drop-in replacement for traditional Monte Carlo methods for Bayesian inference. Our algorithm is based on generating a Gaussian Process surrogate model of the log-posterior, aided by a Support Vector Machine classifier that excludes extreme or non-finite values. An active learning scheme allows us to reduce the number of required posterior evaluations by two orders of magnitude compared to traditional Monte Carlo inference. Our algorithm allows for parallel evaluations of the posterior at optimal locations, further reducing wall-clock times. We significantly improve performance using properties of the posterior in our active learning scheme and for the definition of the GP prior. In particular we account for the expected dynamical range of the posterior in different dimensionalities. We test our model against a number of synthetic and cosmological examples. GPry outperforms traditional Monte Carlo methods when the evaluation time of the likelihood (or the calculation of theoretical observables) is of the order of seconds; for evaluation times of over a minute it can perform inference in days that would take months using traditional methods. GPry is distributed as an open source Python package (pip install gpry) and can also be found at https://github.com/jonaselgammal/GPry.
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在分析由(X,Y)-PAIS组成的数据集中,默契假设是每对对应于相同的观察单元。然而,如果通过记录链接获得两种文件的成对,则可以在不匹配错误生根的结果中违反此假设,例如,在两个文件中缺少可靠的标识符中。最近,在这个设置下,在“混合数据”术语下,在该设置中飙升,其中通过未知的索引置换来表示(x,y)-pairs的底层正确配对。置换的显式建模往往与大量的过度装备相关联,提示需要合适的正则化方法。在本文中,我们提出了一种柔性指数家庭,以便在置换组上为此目的,可用于集成各种结构,例如稀疏和局部约束的混洗。这前结果是针对规范洗牌数据问题的缀合物,其中固定置换上的可能性条件可以在相应的(x,y)-pabes上表示为产品。推断是基于EM算法,其中富有居民算法由Fisher-yates算法近似。如果(x,y)-paess的可能性在概括的线性模型的情况下,则显示M-Step以获得从$ n ^ 2 $的大幅减少到$ n $术语。合成和实数据的比较表明,所提出的方法对竞争方法有利比较。
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标准GPS为行为良好的流程提供了灵活的建模工具。然而,预计与高斯的偏差有望在现实世界数据集中出现,结构异常值和冲击通常会观察到。在这些情况下,GP可能无法充分建模不确定性,并且可能会过度推动。在这里,我们将GP框架扩展到一类新的时间变化的GP,从而可以直接建模重尾非高斯行为,同时通过非均匀GPS表示的无限混合物保留了可拖动的条件GP结构。有条件的GP结构是通过在潜在转化的输入空间上调节观测值来获得的,并使用L \'{e} Vy过程对潜在转化的随机演变进行建模,该过程允许贝叶斯在后端预测密度和潜在转化中的贝叶斯推断功能。我们为该模型提供了马尔可夫链蒙特卡洛推理程序,并证明了与标准GP相比的潜在好处。
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