Understanding how biological neural networks carry out learning using spike-based local plasticity mechanisms can lead to the development of powerful, energy-efficient, and adaptive neuromorphic processing systems. A large number of spike-based learning models have recently been proposed following different approaches. However, it is difficult to assess if and how they could be mapped onto neuromorphic hardware, and to compare their features and ease of implementation. To this end, in this survey, we provide a comprehensive overview of representative brain-inspired synaptic plasticity models and mixed-signal CMOS neuromorphic circuits within a unified framework. We review historical, bottom-up, and top-down approaches to modeling synaptic plasticity, and we identify computational primitives that can support low-latency and low-power hardware implementations of spike-based learning rules. We provide a common definition of a locality principle based on pre- and post-synaptic neuron information, which we propose as a fundamental requirement for physical implementations of synaptic plasticity. Based on this principle, we compare the properties of these models within the same framework, and describe the mixed-signal electronic circuits that implement their computing primitives, pointing out how these building blocks enable efficient on-chip and online learning in neuromorphic processing systems.

自主代理需要自定位才能在未知环境中导航。他们可以使用视觉进程（VO）来估计自我运动并使用视觉传感器定位自己。作为惯性传感器或滑板作为轮编码器，这种运动估算策略不会因漂移而受到损害。但是，带有常规摄像机的VO在计算上是要求的，它限制了其在严格的低延迟， - 内存和 - 能量要求的系统中的应用。使用基于事件的相机和神经形态计算硬件为VO问题提供了有希望的低功率解决方案。但是，VO的常规算法不容易转换为神经形态硬件。在这项工作中，我们提出了一种完全由适合神经形态实现的神经元构件构建的VO算法。构建块是代表向量符号体系结构（VSA）计算框架中向量的神经元组，该框架是作为编程神经形态硬件的抽象层提出的。我们提出的VO网络生成并存储了对展示的视觉环境的工作记忆。它更新了此工作内存，同时估计相机的位置和方向的变化。我们证明了如何将VSA作为神经形态机器人技术的计算范式借用。此外，我们的结果代表了使用神经形态计算硬件进行快速和效率的VO以及同时定位和映射（SLAM）的相关任务的重要步骤。我们通过机器人任务和基于事件的数据集对实验进行了实验验证这种方法，并证明了最先进的性能。

基于脑部的事件的神经形态处理系统已成为一种有前途的技术，尤其是生物医学电路和系统。但是，神经网络的神经形态和生物学实现都具有关键的能量和记忆约束。为了最大程度地减少在多核神经形态处理器中的内存资源的使用，我们提出了一种受生物神经网络启发的网络设计方法。我们使用这种方法来设计针对小世界网络优化的新路由方案，同时介绍了一种硬件感知的放置算法，该算法优化了针对小型世界网络模型的资源分配。我们使用规范的小世界网络验证算法，并为其他网络提供初步结果

在视觉场景理解中，推断对象的位置及其刚性转换仍然是一个开放的问题。在这里，我们提出了一种使用有效的分解网络的神经形态解决方案，该解决方案基于三个关键概念：（1）基于矢量符号体系结构（VSA）的计算框架，带有复杂值值矢量； （2）分层谐振器网络（HRN）的设计，以处理视觉场景中翻译和旋转的非交换性质，而两者都被组合使用； （3）设计多室尖峰拟态神经元模型，用于在神经形态硬件上实现复杂值的矢量结合。 VSA框架使用矢量结合操作来产生生成图像模型，其中绑定充当了几何变换的模棱两可的操作。因此，场景可以描述为向量产物的总和，从而可以通过谐振器网络有效地分解以推断对象及其姿势。 HRN启用了分区体系结构的定义，其中矢量绑定是一个分区内的水平和垂直翻译，以及另一个分区内的旋转和缩放的定义。尖峰神经元模型允许将谐振网络映射到有效且低功耗的神经形态硬件上。在这项工作中，我们使用由简单的2D形状组成的合成场景展示了我们的方法，经历了刚性的几何变换和颜色变化。同伴论文在现实世界的应用程序方案中为机器视觉和机器人技术展示了这种方法。

自主边缘设备的强大现实部署需要对用户，环境和任务引起的可变性进行芯片改编。由于片上记忆的限制，先前的学习设备仅限于没有时间内容的静态刺激。我们提出了一个0.45毫米$^2 $尖峰RNN处理器，启用了几秒钟的任务 - 不合骨在线学习，我们为导航，手势识别和在0.8％的内存架设上进行示例显示，并在0.8％的内存间接开销和<150- $ \ $ \ MU $中进行了显示。W培训功率预算。

Structural Health Monitoring (SHM) describes a process for inferring quantifiable metrics of structural condition, which can serve as input to support decisions on the operation and maintenance of infrastructure assets. Given the long lifespan of critical structures, this problem can be cast as a sequential decision making problem over prescribed horizons. Partially Observable Markov Decision Processes (POMDPs) offer a formal framework to solve the underlying optimal planning task. However, two issues can undermine the POMDP solutions. Firstly, the need for a model that can adequately describe the evolution of the structural condition under deterioration or corrective actions and, secondly, the non-trivial task of recovery of the observation process parameters from available monitoring data. Despite these potential challenges, the adopted POMDP models do not typically account for uncertainty on model parameters, leading to solutions which can be unrealistically confident. In this work, we address both key issues. We present a framework to estimate POMDP transition and observation model parameters directly from available data, via Markov Chain Monte Carlo (MCMC) sampling of a Hidden Markov Model (HMM) conditioned on actions. The MCMC inference estimates distributions of the involved model parameters. We then form and solve the POMDP problem by exploiting the inferred distributions, to derive solutions that are robust to model uncertainty. We successfully apply our approach on maintenance planning for railway track assets on the basis of a "fractal value" indicator, which is computed from actual railway monitoring data.

The polynomial kernels are widely used in machine learning and they are one of the default choices to develop kernel-based classification and regression models. However, they are rarely used and considered in numerical analysis due to their lack of strict positive definiteness. In particular they do not enjoy the usual property of unisolvency for arbitrary point sets, which is one of the key properties used to build kernel-based interpolation methods. This paper is devoted to establish some initial results for the study of these kernels, and their related interpolation algorithms, in the context of approximation theory. We will first prove necessary and sufficient conditions on point sets which guarantee the existence and uniqueness of an interpolant. We will then study the Reproducing Kernel Hilbert Spaces (or native spaces) of these kernels and their norms, and provide inclusion relations between spaces corresponding to different kernel parameters. With these spaces at hand, it will be further possible to derive generic error estimates which apply to sufficiently smooth functions, thus escaping the native space. Finally, we will show how to employ an efficient stable algorithm to these kernels to obtain accurate interpolants, and we will test them in some numerical experiment. After this analysis several computational and theoretical aspects remain open, and we will outline possible further research directions in a concluding section. This work builds some bridges between kernel and polynomial interpolation, two topics to which the authors, to different extents, have been introduced under the supervision or through the work of Stefano De Marchi. For this reason, they wish to dedicate this work to him in the occasion of his 60th birthday.

The proliferation of deep learning techniques led to a wide range of advanced analytics applications in important business areas such as predictive maintenance or product recommendation. However, as the effectiveness of advanced analytics naturally depends on the availability of sufficient data, an organization's ability to exploit the benefits might be restricted by limited data or likewise data access. These challenges could force organizations to spend substantial amounts of money on data, accept constrained analytics capacities, or even turn into a showstopper for analytics projects. Against this backdrop, recent advances in deep learning to generate synthetic data may help to overcome these barriers. Despite its great potential, however, synthetic data are rarely employed. Therefore, we present a taxonomy highlighting the various facets of deploying synthetic data for advanced analytics systems. Furthermore, we identify typical application scenarios for synthetic data to assess the current state of adoption and thereby unveil missed opportunities to pave the way for further research.

To make machine learning (ML) sustainable and apt to run on the diverse devices where relevant data is, it is essential to compress ML models as needed, while still meeting the required learning quality and time performance. However, how much and when an ML model should be compressed, and {\em where} its training should be executed, are hard decisions to make, as they depend on the model itself, the resources of the available nodes, and the data such nodes own. Existing studies focus on each of those aspects individually, however, they do not account for how such decisions can be made jointly and adapted to one another. In this work, we model the network system focusing on the training of DNNs, formalize the above multi-dimensional problem, and, given its NP-hardness, formulate an approximate dynamic programming problem that we solve through the PACT algorithmic framework. Importantly, PACT leverages a time-expanded graph representing the learning process, and a data-driven and theoretical approach for the prediction of the loss evolution to be expected as a consequence of training decisions. We prove that PACT's solutions can get as close to the optimum as desired, at the cost of an increased time complexity, and that, in any case, such complexity is polynomial. Numerical results also show that, even under the most disadvantageous settings, PACT outperforms state-of-the-art alternatives and closely matches the optimal energy cost.

Learned Bloom Filters, i.e., models induced from data via machine learning techniques and solving the approximate set membership problem, have recently been introduced with the aim of enhancing the performance of standard Bloom Filters, with special focus on space occupancy. Unlike in the classical case, the "complexity" of the data used to build the filter might heavily impact on its performance. Therefore, here we propose the first in-depth analysis, to the best of our knowledge, for the performance assessment of a given Learned Bloom Filter, in conjunction with a given classifier, on a dataset of a given classification complexity. Indeed, we propose a novel methodology, supported by software, for designing, analyzing and implementing Learned Bloom Filters in function of specific constraints on their multi-criteria nature (that is, constraints involving space efficiency, false positive rate, and reject time). Our experiments show that the proposed methodology and the supporting software are valid and useful: we find out that only two classifiers have desirable properties in relation to problems with different data complexity, and, interestingly, none of them has been considered so far in the literature. We also experimentally show that the Sandwiched variant of Learned Bloom filters is the most robust to data complexity and classifier performance variability, as well as those usually having smaller reject times. The software can be readily used to test new Learned Bloom Filter proposals, which can be compared with the best ones identified here.