We present a novel predictive model architecture based on the principles of predictive coding that enables open loop prediction of future observations over extended horizons. There are two key innovations. First, whereas current methods typically learn to make long-horizon open-loop predictions using a multi-step cost function, we instead run the model open loop in the forward pass during training. Second, current predictive coding models initialize the representation layer's hidden state to a constant value at the start of an episode, and consequently typically require multiple steps of interaction with the environment before the model begins to produce accurate predictions. Instead, we learn a mapping from the first observation in an episode to the hidden state, allowing the trained model to immediately produce accurate predictions. We compare the performance of our architecture to a standard predictive coding model and demonstrate the ability of the model to make accurate long horizon open-loop predictions of simulated Doppler radar altimeter readings during a six degree of freedom Mars landing. Finally, we demonstrate a 2X reduction in sample complexity by using the model to implement a Dyna style algorithm to accelerate policy learning with proximal policy optimization.

This paper proposes a novel adaptive guidance system developed using reinforcement meta-learning with a recurrent policy and value function approximator. The use of recurrent network layers allows the deployed policy to adapt real time to environmental forces acting on the agent. We compare the performance of the DR/DV guidance law, an RL agent with a non-recurrent policy, and an RL agent with a recurrent policy in four difficult tasks with unknown but highly variable dynamics. These tasks include a safe Mars landing with random engine failure and a landing on an asteroid with unknown environmental dynamics. We also demonstrate the ability of a recurrent policy to navigate using only Doppler radar altimeter returns, thus integrating guidance and navigation. INTRODUCTION Many space missions take place in environments with complex and time-varying dynamics that may be incompletely modeled during the mission design phase. For example, during an orbital refueling mission, the inertia tensor of each of the two spacecraft will change significantly as fuel is transferred from one spacecraft to the other, which can make the combined system difficult to control. The wet mass of an exoatmospheric kill vehicles (EKV) consists largely of fuel, and as this is depleted with divert thrusts, the center of mass changes, and the divert thrusts are no longer orthogonal to the EKV's velocity vector, which wastes fuel and impacts performance. Future missions to asteroids might be undertaken before the asteroid's gravitational field, rotational velocity, and local solar radiation pressure are accurately modeled.

In this paper, we solve a semi-supervised regression problem. Due to the lack of knowledge about the data structure and the presence of random noise, the considered data model is uncertain. We propose a method which combines graph Laplacian regularization and cluster ensemble methodologies. The co-association matrix of the ensemble is calculated on both labeled and unlabeled data; this matrix is used as a similarity matrix in the regularization framework to derive the predicted outputs. We use the low-rank decomposition of the co-association matrix to significantly speedup calculations and reduce memory. Numerical experiments using the Monte Carlo approach demonstrate robustness, efficiency, and scalability of the proposed method.

Deep reinforcement learning algorithms have recently been used to train multiple interacting agents in a centralised manner whilst keeping their execution decentralised. When the agents can only acquire partial observations and are faced with a task requiring coordination and synchronisation skills, inter-agent communication plays an essential role. In this work, we propose a framework for multi-agent training using deep deterministic policy gradients that enables the concurrent, end-to-end learning of an explicit communication protocol through a memory device. During training, the agents learn to perform read and write operations enabling them to infer a shared representation of the world. We empirically demonstrate that concurrent learning of the communication device and individual policies can improve inter-agent coordination and performance, and illustrate how different communication patterns can emerge for different tasks.

Abstract--We consider an ad hoc network where multiple users access the same set of channels. The channel characteristics are unknown and could be different for each user (heterogeneous). No controller is available to coordinate channel selections by the users, and if multiple users select the same channel, they collide and none of them receive any rate (or reward). For such a completely decentralized network we develop algorithms that aim to achieve optimal network throughput. Due to lack of any direct communication between the users, we allow each user to exchange information by transmitting in a specific pattern and sense such transmissions from others. However, such transmissions and sensing for information exchange do not add to network throughput. For the wideband sensing and narrowband sensing scenarios, we first develop explore-and-commit algorithms that converge to near-optimal allocation with high probability in a small number of rounds. Building on this, we develop an algorithm that gives logarithmic regret, even when the number of users changes with time. I. INTRODUCTION Cognitive cellular networks are one of the key components of the next generation wireless networks. It promises seamless and high-speed connectivity by combining the features of both cellular and ad hoc networks [1, 2], which is a much-desired requirement in all mission-critical and Internet of Things (IoT) applications. In the ad hoc component of such networks, a central controller may not always exist which makes the coordination amongthe users challenging. Further, users may not know characteristics (mean rewards) of the available channels, and these characteristics could be statistically different across users due to their geographical separations. Thus for effective utilization of network resources, users not only need to learn the channel characteristics experienced by them but also that experienced by the others. This work develops distributed learning algorithms for such networks that achieve optimal network performance using signaling schemes. A. Sensing and Signaling Ad hoc networks are usually dynamic in nature and users may not know how many others are present in the network.

Continuous Speech Keyword Spotting (CSKS) is the problem of spotting keywords in recorded conversations, when a small number of instances of keywords are available in training data. Unlike the more common Keyword Spotting, where an algorithm needs to detect lone keywords or short phrases like "Alexa", "Cortana", "Hi Alexa!", "Whatsup Octavia?" etc. in speech, CSKS needs to filter out embedded words from a continuous flow of speech, ie. spot "Anna" and "github" in "I know a developer named Anna who can look into this github issue." Apart from the issue of limited training data availability, CSKS is an extremely imbalanced classification problem. We address the limitations of simple keyword spotting baselines for both aforementioned challenges by using a novel combination of loss functions (Prototypical networks' loss and metric loss) and transfer learning. Our method improves F1 score by over 10%.

Prediction accuracy and model explainability are the two most important objectives when developing machine learning algorithms to solve real-world problems. The neural networks are known to possess good prediction performance, but lack of sufficient model explainability. In this paper, we propose to enhance the explainability of neural networks through the following architecture constraints: a) sparse additive subnetworks; b) orthogonal projection pursuit; and c) smooth function approximation. It leads to a sparse, orthogonal and smooth explainable neural network (SOSxNN). The multiple parameters in the SOSxNN model are simultaneously estimated by a modified mini-batch gradient descent algorithm based on the backpropagation technique for calculating the derivatives and the Cayley transform for preserving the projection orthogonality. The hyperparameters controlling the sparse and smooth constraints are optimized by the grid search. Through simulation studies, we compare the SOSxNN method to several benchmark methods including least absolute shrinkage and selection operator, support vector machine, random forest, and multi-layer perceptron. It is shown that proposed model keeps the flexibility of pursuing prediction accuracy while attaining the improved interpretability, which can be therefore used as a promising surrogate model for complex model approximation. Finally, the real data example from the Lending Club is employed as a showcase of the SOSxNN application.

Diffusion reach probability between two nodes on a network is defined as the probability of a cascade originating from one node reaching to another node. An infinite number of cascades would enable calculation of true diffusion reach probabilities between any two nodes. However, there exists only a finite number of cascades and one usually has access only to a small portion of all available cascades. In this work, we addressed the problem of estimating diffusion reach probabilities given only a limited number of cascades and partial information about underlying network structure. Our proposed strategy employs node representation learning to generate and feed node embeddings into machine learning algorithms to create models that predict diffusion reach probabilities. We provide experimental analysis using synthetically generated cascades on two real-world social networks. Results show that proposed method is superior to using values calculated from available cascades when the portion of cascades is small.

Deep neural networks (DNNs)-powered Electrocardiogram (ECG) diagnosis systems emerge recently, and are expected to take over tedious examinations by cardiologists. However, their vulnerability to adversarial attacks still lack of comprehensive investigation. ECG recordings differ from images in the visualization, dynamic property and accessibility, thus, the existing image-targeted attack may not directly applicable. To fill this gap, this paper proposes ECGadv to explore the feasibility of adversarial attacks on arrhythmia classification system. We identify the main issues under two different deployment models(i.e., cloud-based and local-based) and propose effective attack schemes respectively. Our results demonstrate the blind spots of DNN-powered diagnosis system under adversarial attacks, which facilitates future researches on countermeasures.

Supervised machine learning methods usually require a large set of labeled examples for model training. However, in many real applications, there are plentiful unlabeled data but limited labeled data; and the acquisition of labels is costly. Active learning (AL) reduces the labeling cost by iteratively selecting the most valuable data to query their labels from the annotator. This article introduces a Python toobox ALiPy for active learning. ALiPy provides a module based implementation of active learning framework, which allows users to conveniently evaluate, compare and analyze the performance of active learning methods. In the toolbox, multiple options are available for each component of the learning framework, including data process, active selection, label query, results visualization, etc. In addition to the implementations of more than 20 state-of-the-art active learning algorithms, ALiPy also supports users to easily configure and implement their own approaches under different active learning settings, such as AL for multi-label data, AL with noisy annotators, AL with different costs and so on. The toolbox is well-documented and open-source on Github, and can be easily installed through PyPI.