Data-driven models such as neural networks are being applied more and more to safety-critical applications, such as the modeling and control of cyber-physical systems. Despite the flexibility of the approach, there are still concerns about the safety of these models in this context, as well as the need for large amounts of potentially expensive data. In particular, when long-term predictions are needed or frequent measurements are not available, the open-loop stability of the model becomes important. However, it is difficult to make such guarantees for complex black-box models such as neural networks, and prior work has shown that model stability is indeed an issue. In this work, we consider an aluminum extraction process where measurements of the internal state of the reactor are time-consuming and expensive. We model the process using neural networks and investigate the role of including skip connections in the network architecture as well as using l1 regularization to induce sparse connection weights. We demonstrate that these measures can greatly improve both the accuracy and the stability of the models for datasets of varying sizes.
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人工神经网络今天具有广泛的应用程序,因为它们的高度灵活性和从数据中建模非线性功能的能力。但是,由于其黑盒性质,从小型数据集概括的能力差以及在培训期间的不一致的融合,神经网络的可信度受到限制。铝电解是一个复杂的非线性过程,具有许多相互关联的子处理。人工神经网络可能非常适合对铝电解过程进行建模,但是此过程的安全性最关键的性质需要值得信赖的模型。在这项工作中,稀疏的神经网络经过训练,以建模铝电解模拟器的系统动力学。与相应的密集神经网络相比,稀疏模型结构的模型复杂性显着降低。我们认为这使模型更容易解释。此外,实证研究表明,稀疏模型比密集的神经网络从小型训练集中概括得更好。此外,训练具有不同参数初始化的稀疏神经网络的合奏表明,模型会收敛到具有相似学习的输入特征的相似模型结构。
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随着数据的不断增加,将现代机器学习方法应用于建模和控制等领域的兴趣爆炸。但是,尽管这种黑盒模型具有灵活性和令人惊讶的准确性,但仍然很难信任它们。结合两种方法的最新努力旨在开发灵活的模型,这些模型仍然可以很好地推广。我们称为混合分析和建模(HAM)的范式。在这项工作中,我们调查了使用数据驱动模型纠正基于错误的物理模型的纠正源术语方法(COSTA)。这使我们能够开发出可以进行准确预测的模型,即使问题的基本物理学尚未得到充分理解。我们将Costa应用于铝电解电池中的Hall-H \'Eroult工艺。我们证明该方法提高了准确性和预测稳定性,从而产生了总体可信赖的模型。
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Graph Neural Networks (GNNs) are deep learning models designed to process attributed graphs. GNNs can compute cluster assignments accounting both for the vertex features and for the graph topology. Existing GNNs for clustering are trained by optimizing an unsupervised minimum cut objective, which is approximated by a Spectral Clustering (SC) relaxation. SC offers a closed-form solution that, however, is not particularly useful for a GNN trained with gradient descent. Additionally, the SC relaxation is loose and yields overly smooth cluster assignments, which do not separate well the samples. We propose a GNN model that optimizes a tighter relaxation of the minimum cut based on graph total variation (GTV). Our model has two core components: i) a message-passing layer that minimizes the $\ell_1$ distance in the features of adjacent vertices, which is key to achieving sharp cluster transitions; ii) a loss function that minimizes the GTV in the cluster assignments while ensuring balanced partitions. By optimizing the proposed loss, our model can be self-trained to perform clustering. In addition, our clustering procedure can be used to implement graph pooling in deep GNN architectures for graph classification. Experiments show that our model outperforms other GNN-based approaches for clustering and graph pooling.
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Nowadays, the PQ flexibility from the distributed energy resources (DERs) in the high voltage (HV) grids plays a more critical and significant role in grid congestion management in TSO grids. This work proposed a multi-stage deep reinforcement learning approach to estimate the PQ flexibility (PQ area) at the TSO-DSO interfaces and identifies the DER PQ setpoints for each operating point in a way, that DERs in the meshed HV grid can be coordinated to offer flexibility for the transmission grid. In the estimation process, we consider the steady-state grid limits and the robustness in the resulting voltage profile against uncertainties and the N-1 security criterion regarding thermal line loading, essential for real-life grid operational planning applications. Using deep reinforcement learning (DRL) for PQ flexibility estimation is the first of its kind. Furthermore, our approach of considering N-1 security criterion for meshed grids and robustness against uncertainty directly in the optimization tasks offers a new perspective besides the common relaxation schema in finding a solution with mathematical optimal power flow (OPF). Finally, significant improvements in the computational efficiency in estimation PQ area are the highlights of the proposed method.
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部分微分方程(PDE)参见在科学和工程中的广泛使用,以将物理过程的模拟描述为标量和向量场随着时间的推移相互作用和协调。由于其标准解决方案方法的计算昂贵性质,神经PDE代理已成为加速这些模拟的积极研究主题。但是,当前的方法并未明确考虑不同字段及其内部组件之间的关系,这些关系通常是相关的。查看此类相关场的时间演变通过多活动场的镜头,使我们能够克服这些局限性。多胎场由标量,矢量以及高阶组成部分组成,例如双分数和三分分射线。 Clifford代数可以描述它们的代数特性,例如乘法,加法和其他算术操作。据我们所知,本文介绍了此类多人表示的首次使用以及Clifford的卷积和Clifford Fourier在深度学习的背景下的转换。由此产生的Clifford神经层普遍适用,并将在流体动力学,天气预报和一般物理系统的建模领域中直接使用。我们通过经验评估克利福德神经层的好处,通过在二维Navier-Stokes和天气建模任务以及三维Maxwell方程式上取代其Clifford对应物中常见的神经PDE代理中的卷积和傅立叶操作。克利福德神经层始终提高测试神经PDE代理的概括能力。
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时间序列预测是一个重要的问题,具有许多现实世界的应用。深度神经网络的合奏最近实现了令人印象深刻的预测准确性,但是在许多现实世界中,如此大的合奏是不切实际的。变压器模型已成功应用于各种具有挑战性的问题。我们建议对原始变压器体系结构进行新颖的改编,重点是时间序列预测的任务,称为持久性初始化。该模型通过使用与残留跳过连接的乘法门控机制初始化为幼稚的持久性模型。我们使用具有REZERO标准化和旋转位置编码的解码器变压器,但适应适用于任何自动回归神经网络模型。我们评估了有关挑战性M4数据集的拟议体系结构,与基于合奏的方法相比,取得了竞争性能。我们还将最近提议的变压器模型进行比较,以预测时间序列,显示了M4数据集中的卓越性能。广泛的消融研究表明,持久性初始化会导致更好的性能和更快的收敛性。随着模型的大小的增加,只有我们提出的适应性增长的模型。我们还进行了一项额外的消融研究,以确定正常化和位置编码的选择的重要性,并发现旋转编码的使用和REZERO归一化对于良好的预测性能至关重要。
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使用麦克风阵列的扬声器定位取决于准确的时间延迟估计技术。几十年来,基于与相变的广义跨相关性(GCC-PHAT)的方法已被广泛用于此目的。最近,GCC-PHAT也已用于为神经网络提供输入特征,以消除噪声和混响的影响,但以无噪声条件下的理论保证为代价。我们提出了一种新的方法来扩展GCC-PHAT,其中使用移位模糊的神经网络过滤接收的信号,该神经网络保留信号中包含的时序信息。通过广泛的实验,我们表明我们的模型始终减少不利环境中GCC-PHAT的误差,并保证在理想条件下确切的时间延迟恢复。
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引入了Wasserstein距离的许多变体,以减轻其原始计算负担。尤其是切成薄片的距离(SW),该距离(SW)利用了一维投影,可以使用封闭式的瓦斯汀距离解决方案。然而,它仅限于生活在欧几里得空间中的数据,而Wasserstein距离已被研究和最近在歧管上使用。我们更具体地专门地关注球体,为此定义了新颖的SW差异,我们称之为球形切片 - 拖鞋,这是朝着定义SW差异的第一步。我们的构造明显基于圆圈上瓦斯汀距离的封闭式解决方案,以及新的球形ra径。除了有效的算法和相应的实现外,我们在几个机器学习用例中说明了它的属性,这些用例中,数据的球形表示受到威胁:在球体上的密度估计,变异推理或超球体自动编码器。
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生物系统对形态损害非常强大,但人工系统(机器人)目前却不是。在本文中,我们介绍了一个基于神经细胞自动机的系统,其中运动机器人的进化,然后赋予能够通过基于梯度的训练从损害中再生其形态。因此,我们的方法结合了进化的好处,可以发现各种不同的机器人形态,以及通过可区别的更新规则对鲁棒性的监督培训的效率。所得的神经细胞自动机能够生长能够恢复超过80 \%功能的虚拟机器人,即使经过严重的形态损害。
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