X-ray diffraction (XRD) is a well-known technique used by scientists and engineers to determine the atomic-scale structures as a basis for understanding the composition-structure-property relationship of materials. The current approach for the analysis of XRD data is a multi-stage process requiring several intensive computations such as integration along 2θ for conversion to 1D patterns (intensity-2θ), background removal by polynomial fitting, and indexing against a large database of reference peaks. It impacts the decisions about the subsequent experiments of the materials under investigation and delays the overall process. In this paper, we focus on eliminating such multi-stage XRD analysis by directly learning the phase regions from the raw (2D) XRD image. We introduce a peak area detection network (PADNet) that directly learns to predict the phase regions using the raw XRD patterns without any need for explicit preprocessing and background removal. PADNet contains specially designed large symmetrical convolutional filters at the first layer to capture the peaks and automatically remove the background by computing the difference in intensity counts across different symmetries. We evaluate PADNet using two sets of XRD patterns collected from SLAC and Bruker D-8 for the Sn-Ti-Zn-O composition space; each set contains 177 experimental XRD patterns with their phase regions. We find that PADNet can successfully classify the XRD patterns independent of the presence of background noise and perform better than the current approach of extrapolating phase region labels based on 1D XRD patterns.

Organic Solar Cells are a promising technology for solving the clean energy crisis in the world. However, generating candidate chemical compounds for solar cells is a time-consuming process requiring thousands of hours of laboratory analysis. For a solar cell, the most important property is the power conversion efficiency which is dependent on the highest occupied molecular orbitals (HOMO) values of the donor molecules. Recently, machine learning techniques have proved to be very useful in building predictive models for HOMO values of donor structures of Organic Photovoltaic Cells (OPVs). Since experimental datasets are limited in size, current machine learning models are trained on data derived from calculations based on density functional theory (DFT). Molecular line notations such as SMILES or InChI are popular input representations for describing the molecular structure of donor molecules. The two types of line representations encode different information, such as SMILES defines the bond types while InChi defines protonation. In this work, we present an ensemble deep neural network architecture, called SINet, which harnesses both the SMILES and InChI molecular representations to predict HOMO values and leverage the potential of transfer learning from a sizeable DFT-computed dataset- Harvard CEP to build more robust predictive models for relatively smaller HOPV datasets. Harvard CEP dataset contains molecular structures and properties for 2.3 million candidate donor structures for OPV while HOPV contains DFT-computed and experimental values of 350 and 243 molecules respectively. Our results demonstrate significant performance improvement from the use of transfer learning and leveraging both molecular representations.

Materials discovery is crucial for making scientific advances in many domains. Collections of data from experiments and first-principle computations have spurred interest in applying machine learning methods to create predictive models capable of mapping from composition and crystal structures to materials properties. Generally, these are regression problems with the input being a 1D vector composed of numerical attributes representing the material composition and/or crystal structure. While neural networks consisting of fully connected layers have been applied to such problems, their performance often suffers from the vanishing gradient problem when network depth is increased. Hence, predictive modeling for such tasks has been mainly limited to traditional machine learning techniques such as Random Forest. In this paper, we study and propose design principles for building deep regression networks composed of fully connected layers with numerical vectors as input. We introduce a novel deep regression network with individual residual learning, IRNet, that places shortcut connections after each layer so that each layer learns the residual mapping between its output and input. We use the problem of learning properties of inorganic materials from numerical attributes derived from material composition and/or crystal structure to compare IRNet's performance against that of other machine learning techniques. Using multiple datasets from the Open Quantum Materials Database (OQMD) and Materials Project for training and evaluation, we show that IRNet provides significantly better prediction performance than the state-of-the-art machine learning approaches currently used by domain scientists. We also show that IRNet's use of individual residual learning leads to better convergence during the training phase than when shortcut connections are between multi-layer stacks while maintaining the same number of parameters.

Training Convolutional Neural Network (CNN) is a computationally intensive task whose parallelization has become critical in order to complete the training in an acceptable time. However, there are two obstacles to developing a scalable parallel CNN in a distributed-memory computing environment. One is the high degree of data dependency exhibited in the model parameters across every two adjacent minibatches and the other is the large amount of data to be transferred across the communication channel. In this paper, we present a parallelization strategy that maximizes the overlap of inter-process communication with the computation. The overlapping is achieved by using a thread per compute node to initiate communication after the gradients are available. The output data of backpropagation stage is generated at each model layer, and the communication for the data can run concurrently with the computation of other layers. To study the effectiveness of the overlapping and its impact on the scalability, we evaluated various model architectures and hyperparameter settings. When training VGG-A model using ImageNet data sets, we achieve speedups of 62.97× and 77.97× on 128 compute nodes using mini-batch sizes of 256 and 512, respectively.

Recent progress in big data and computer vision with deep learning models has gained a lot of attention. Deep learning has been performed on tasks such as image classification, object detection, image segmentation, image captioning, visual question and answering, using large collections of annotated images. This calls for more curated large image datasets with clearer descriptions, cleaner contents, and diversified usability. However, the curation and labeling of such datasets can be labor-intensive. In this paper, we present PinterNet, an algorithm for automatic curation and label generation from noisy textual descriptions, and also publish a big image dataset containing over 110K images automatically labeled with their themes. Our dataset is hierarchical in nature, it has high level category information which we refer as verticals with fine-grained thematic labels at lower level. This advocates a new type of hierarchical theme classification problem closer to human cognition and of business value. We provide benchmark performances using deep learning models based on AlexNet architecture with different pre-training schemes for this novel task and new data.