There is an abundance of complex dynamic systems that are critical to our daily lives and our society but that are hardly understood, and even with today's possibilities to sense and collect large amounts of experimental data, they are so complex and continuously evolving that it is unlikely that their dynamics will ever be understood in full detail. Nevertheless, through computational tools we can try to make the best possible use of the current technologies and available data. We believe that the most useful models will have to take into account the imbalance between system complexity and available data in the context of limited knowledge or multiple hypotheses. The complex system of biological cells is a prime example of such a system that is studied in systems biology and has motivated the methods presented in this paper. They were developed as part of the DARPA Rapid Threat Assessment (RTA) program, which is concerned with understanding of the mechanism of action (MoA) of toxins or drugs affecting human cells. Using a combination of Gaussian processes and abstract network modeling, we present three fundamentally different machine-learning-based approaches to learn causal relations and synthesize causal networks from high-dimensional time series data. While other types of data are available and have been analyzed and integrated in our RTA work, we focus on transcriptomics (that is gene expression) data obtained from high-throughput microarray experiments in this paper to illustrate capabilities and limitations of our algorithms. Our algorithms make different but overall relatively few biological assumptions, so that they are applicable to other types of biological data and potentially even to other complex systems that exhibit high dimensionality but are not of biological nature.
@cite_30: Nowadays, the detection of human fall is a problem recognized by the entire scientific community. Methods that have good performance use human falls samples in the train set, while methods that do not use it, can only work well under certain conditions. Since examples of human falls are very difficult to retrieve, there is a strong need to develop systems that can work well event with few or no data to be used for their training phase. In this article, we show a first study on few-shot learning Siamese Neural Network applied to human falls detection by using audio signals. This method has been compared with algorithms based on SVM and OCSVM, all evaluated starting from the same conditions. The proposed approach is able to learn the differences between signals belonging to different classes of events. In classification phase, using only one human fall signal as a template, it achieves about 80 of F1 -Measure related to the human fall class, while the SVM based method gets around 69 , when it is trained in the same data knowledge conditions.
@cite_11: 
@cite_14: 6DOF camera relocalization is an important component of autonomous driving and navigation. Deep learning has recently emerged as a promising technique to tackle this problem. In this paper, we present a novel relative geometry-aware Siamese neural network to enhance the performance of deep learning-based methods through explicitly exploiting the relative geometry constraints between images. We perform multi-task learning and predict the absolute and relative poses simultaneously. We regularize the shared-weight twin networks in both the pose and feature domains to ensure that the estimated poses are globally as well as locally correct. We employ metric learning and design a novel adaptive metric distance loss to learn a feature that is capable of distinguishing poses of visually similar images from different locations. We evaluate the proposed method on public indoor and outdoor benchmarks and the experimental results demonstrate that our method can significantly improve localization performance. Furthermore, extensive ablation evaluations are conducted to demonstrate the effectiveness of different terms of the loss function.
@cite_28: Searching sounds by text labels is often difficult, as text labels cannot always provide sufficient information for the sound content. Previously we proposed an unsupervised system called IMISOUND for sound search by vocal imitation. In this paper, we further propose a Convolutional Semi-Siamese Network (CSN) called IMINET. IMINET uses two towers of Convolutional Neural Networks (CNN) to extract features from vocal imitations and sound recordings, respectively. It then adopts a fully connected network to predict the similarity between vocal imitations and sound recordings. We propose three different configurations of the CSN by choosing different weight sharing strategies between the two towers. We also propose late fusion of the retrieval results of IMINET's different configurations and those of IMISOUND as a baseline. Experiments show significant improvements of the retrieval performance from the IMISOUND baseline to the fusion of IMINET's different configurations, and to different fusions between IMINET and the IMISOUND baseline.
@cite_29: We consider the statistical problem of learning common source of variability in data which are synchronously captured by multiple sensors, and demonstrate that Siamese neural networks can be naturally applied to this problem. This approach is useful in particular in exploratory, data-driven applications, where neither a model nor label information is available. In recent years, many researchers have successfully applied Siamese neural networks to obtain an embedding of data which corresponds to a "semantic similarity". We present an interpretation of this "semantic similarity" as learning of equivalence classes. We discuss properties of the embedding obtained by Siamese networks and provide empirical results that demonstrate the ability of Siamese networks to learn common variability.
@cite_32: 
@cite_5: Abstract We consider the statistical problem of learning a common source of variability in data which are synchronously captured by multiple sensors, and demonstrate that Siamese neural networks can be naturally applied to this problem. This approach is useful in particular in exploratory, data-driven applications, where neither a model nor label information is available. In recent years, many researchers have successfully applied Siamese neural networks to obtain an embedding of data which corresponds to a “semantic similarity”. We present an interpretation of this “semantic similarity” as learning of equivalence classes. We demonstrate the ability of Siamese networks to learn common variability in a range of experiments on synthetic and real-world data, and demonstrate the potential of Siamese networks to provide new leads for data-driven research through unsupervised learning in cancer data.
@cite_16: 
@cite_13: 
@cite_17: Original siamese neural network objective function.Polar sine-based angular reformulation for cosine dissimilarity learning.Application on a multimodal human action dataset.New evaluations of 3 siamese neural networks using input data pairs, triplets and tuples.Projection space analysis and computation complexity. This paper focuses on metric learning with Siamese Neural Networks (SNN). Without any prior, SNNs learn to compute a non-linear metric using only similarity and dissimilarity relationships between input data. Our SNN model proposes three contributions: a tuple-based architecture, an objective function with a norm regularisation and a polar sine-based angular reformulation for cosine dissimilarity learning. Applying our SNN model for Human Action Recognition (HAR) gives very competitive results using only one accelerometer or one motion capture point on the Multimodal Human Action Dataset (MHAD). Performances and properties of our proposals in terms of accuracy, convergence and complexity are assessed, with very favourable results. Additional experiments on the Challenge for Multimodal Mid-Air Gesture Recognition for Close Human Computer Interaction Dataset (ChAirGest) confirm the competitive comparison of our proposals with state-of-the-arts models.
The particular artificial neural networks we use for causality detection in our primary method fall into the general class of Siamese neural networks, which are composed using two subnetworks with shared weights, each responsible for processing one of the inputs. While originally proposed for signature verification (a type of similarity detection) in @cite_13 @cite_16 , they have recently attracted renewed interest @cite_32 @cite_29 @cite_17 @cite_5 @cite_11 @cite_28 @cite_30 @cite_14 , with many applications ranging from image recognition to audio search. The key abstract feature of Siamese networks that is important for us is their capability to directly encode structural properties of a logical relation (in our case causality) and hence to enable efficient learning tailored to the domain. Although we use relatively low-complexity 1D convolutional Siamese networks suitable for time series processing, we had to resort to curriculum training to obtain a stable learning algorithm. While conventional Siamese networks are suitable for similarity relations that exhibit a structural symmetry, we also use a variation of Siamese networks to detect causality which directly encode the structural antisymmetry of this relation (when viewed as a function) in terms of the network structure.