水果和蔬菜的检测,分割和跟踪是精确农业的三个基本任务,实现了机器人的收获和产量估计。但是,现代算法是饥饿的数据,并非总是有可能收集足够的数据来运用最佳性能的监督方法。由于数据收集是一项昂贵且繁琐的任务,因此在农业中使用计算机视觉的能力通常是小企业无法实现的。在此背景下的先前工作之后,我们提出了一种初始弱监督的解决方案,以减少在精确农业应用程序中获得最新检测和细分所需的数据,在这里,我们在这里改进该系统并探索跟踪果实的问题果园。我们介绍了拉齐奥南部(意大利)葡萄的葡萄园案例,因为葡萄由于遮挡,颜色和一般照明条件而难以分割。当有一些可以用作源数据的初始标记数据(例如,葡萄酒葡萄数据)时,我们会考虑这种情况,但与目标数据有很大不同(例如表格葡萄数据)。为了改善目标数据的检测和分割,我们建议使用弱边界框标签训练分割算法,而对于跟踪,我们从运动算法中利用3D结构来生成来自已标记样品的新标签。最后,将两个系统组合成完整的半监督方法。与SOTA监督解决方案的比较表明,我们的方法如何能够训练以很少的标记图像和非常简单的标签来实现高性能的新型号。
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Simulating quantum channels is a fundamental primitive in quantum computing, since quantum channels define general (trace-preserving) quantum operations. An arbitrary quantum channel cannot be exactly simulated using a finite-dimensional programmable quantum processor, making it important to develop optimal approximate simulation techniques. In this paper, we study the challenging setting in which the channel to be simulated varies adversarially with time. We propose the use of matrix exponentiated gradient descent (MEGD), an online convex optimization method, and analytically show that it achieves a sublinear regret in time. Through experiments, we validate the main results for time-varying dephasing channels using a programmable generalized teleportation processor.
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Electricity prices in liberalized markets are determined by the supply and demand for electric power, which are in turn driven by various external influences that vary strongly in time. In perfect competition, the merit order principle describes that dispatchable power plants enter the market in the order of their marginal costs to meet the residual load, i.e. the difference of load and renewable generation. Many market models implement this principle to predict electricity prices but typically require certain assumptions and simplifications. In this article, we present an explainable machine learning model for the prices on the German day-ahead market, which substantially outperforms a benchmark model based on the merit order principle. Our model is designed for the ex-post analysis of prices and thus builds on various external features. Using Shapley Additive exPlanation (SHAP) values, we can disentangle the role of the different features and quantify their importance from empiric data. Load, wind and solar generation are most important, as expected, but wind power appears to affect prices stronger than solar power does. Fuel prices also rank highly and show nontrivial dependencies, including strong interactions with other features revealed by a SHAP interaction analysis. Large generation ramps are correlated with high prices, again with strong feature interactions, due to the limited flexibility of nuclear and lignite plants. Our results further contribute to model development by providing quantitative insights directly from data.
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Despite the impact of psychiatric disorders on clinical health, early-stage diagnosis remains a challenge. Machine learning studies have shown that classifiers tend to be overly narrow in the diagnosis prediction task. The overlap between conditions leads to high heterogeneity among participants that is not adequately captured by classification models. To address this issue, normative approaches have surged as an alternative method. By using a generative model to learn the distribution of healthy brain data patterns, we can identify the presence of pathologies as deviations or outliers from the distribution learned by the model. In particular, deep generative models showed great results as normative models to identify neurological lesions in the brain. However, unlike most neurological lesions, psychiatric disorders present subtle changes widespread in several brain regions, making these alterations challenging to identify. In this work, we evaluate the performance of transformer-based normative models to detect subtle brain changes expressed in adolescents and young adults. We trained our model on 3D MRI scans of neurotypical individuals (N=1,765). Then, we obtained the likelihood of neurotypical controls and psychiatric patients with early-stage schizophrenia from an independent dataset (N=93) from the Human Connectome Project. Using the predicted likelihood of the scans as a proxy for a normative score, we obtained an AUROC of 0.82 when assessing the difference between controls and individuals with early-stage schizophrenia. Our approach surpassed recent normative methods based on brain age and Gaussian Process, showing the promising use of deep generative models to help in individualised analyses.
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We examined multiple deep neural network (DNN) architectures for suitability in predicting neurotransmitter concentrations from labeled in vitro fast scan cyclic voltammetry (FSCV) data collected on carbon fiber electrodes. Suitability is determined by the predictive performance in the "out-of-probe" case, the response to artificially induced electrical noise, and the ability to predict when the model will be errant for a given probe. This work extends prior comparisons of time series classification models by focusing on this specific task. It extends previous applications of machine learning to FSCV task by using a much larger data set and by incorporating recent advancements in deep neural networks. The InceptionTime architecture, a deep convolutional neural network, has the best absolute predictive performance of the models tested but was more susceptible to noise. A naive multilayer perceptron architecture had the second lowest prediction error and was less affected by the artificial noise, suggesting that convolutions may not be as important for this task as one might suspect.
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Dimensionality reduction has become an important research topic as demand for interpreting high-dimensional datasets has been increasing rapidly in recent years. There have been many dimensionality reduction methods with good performance in preserving the overall relationship among data points when mapping them to a lower-dimensional space. However, these existing methods fail to incorporate the difference in importance among features. To address this problem, we propose a novel meta-method, DimenFix, which can be operated upon any base dimensionality reduction method that involves a gradient-descent-like process. By allowing users to define the importance of different features, which is considered in dimensionality reduction, DimenFix creates new possibilities to visualize and understand a given dataset. Meanwhile, DimenFix does not increase the time cost or reduce the quality of dimensionality reduction with respect to the base dimensionality reduction used.
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Besides accuracy, recent studies on machine learning models have been addressing the question on how the obtained results can be interpreted. Indeed, while complex machine learning models are able to provide very good results in terms of accuracy even in challenging applications, it is difficult to interpret them. Aiming at providing some interpretability for such models, one of the most famous methods, called SHAP, borrows the Shapley value concept from game theory in order to locally explain the predicted outcome of an instance of interest. As the SHAP values calculation needs previous computations on all possible coalitions of attributes, its computational cost can be very high. Therefore, a SHAP-based method called Kernel SHAP adopts an efficient strategy that approximate such values with less computational effort. In this paper, we also address local interpretability in machine learning based on Shapley values. Firstly, we provide a straightforward formulation of a SHAP-based method for local interpretability by using the Choquet integral, which leads to both Shapley values and Shapley interaction indices. Moreover, we also adopt the concept of $k$-additive games from game theory, which contributes to reduce the computational effort when estimating the SHAP values. The obtained results attest that our proposal needs less computations on coalitions of attributes to approximate the SHAP values.
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Bayesian optimization (BO) is one of the most effective methods for closed-loop experimental design and black-box optimization. However, a key limitation of BO is that it is an inherently sequential algorithm (one experiment is proposed per round) and thus cannot directly exploit high-throughput (parallel) experiments. Diverse modifications to the BO framework have been proposed in the literature to enable exploitation of parallel experiments but such approaches are limited in the degree of parallelization that they can achieve and can lead to redundant experiments (thus wasting resources and potentially compromising performance). In this work, we present new parallel BO paradigms that exploit the structure of the system to partition the design space. Specifically, we propose an approach that partitions the design space by following the level sets of the performance function and an approach that exploits partially-separable structures of the performance function found. We conduct extensive numerical experiments using a reactor case study to benchmark the effectiveness of these approaches against a variety of state-of-the-art parallel algorithms reported in the literature. Our computational results show that our approaches significantly reduce the required search time and increase the probability of finding a global (rather than local) solution.
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在本文中,我们研究了DRL算法在本地导航问题的应用,其中机器人仅配备有限​​量距离的外部感受传感器(例如LIDAR),在未知和混乱的工作区中朝着目标位置移动。基于DRL的碰撞避免政策具有一些优势,但是一旦他们学习合适的动作的能力仅限于传感器范围,它们就非常容易受到本地最小值的影响。由于大多数机器人在非结构化环境中执行任务,因此寻求能够避免本地最小值的广义本地导航政策,尤其是在未经训练的情况下,这是非常兴趣的。为此,我们提出了一种新颖的奖励功能,该功能结合了在训练阶段获得的地图信息,从而提高了代理商故意最佳行动方案的能力。另外,我们使用SAC算法来训练我们的ANN,这表明在最先进的文献中比其他人更有效。一组SIM到SIM和SIM到现实的实验表明,我们提出的奖励与SAC相结合的表现优于比较局部最小值和避免碰撞的方法。
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社交媒体平台主持了有关每天出现的各种主题的讨论。理解所有内容并将其组织成类别是一项艰巨的任务。处理此问题的一种常见方法是依靠主题建模,但是使用此技术发现的主题很难解释,并且从语料库到语料库可能会有所不同。在本文中,我们提出了基于推文主题分类的新任务,并发布两个相关的数据集。鉴于涵盖社交媒体中最重要的讨论点的广泛主题,我们提供了最近时间段的培训和测试数据,可用于评估推文分类模型。此外,我们在任务上对当前的通用和领域特定语言模型进行定量评估和分析,这为任务的挑战和性质提供了更多见解。
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