60,175 research outputs found
Analyzing machine learning models to accelerate generation of fundamental materials insights
Machine learning for materials science envisions the acceleration of basic science research through automated identification of key data relationships to augment human interpretation and gain scientific understanding. A primary role of scientists is extraction of fundamental knowledge from data, and we demonstrate that this extraction can be accelerated using neural networks via analysis of the trained data model itself rather than its application as a prediction tool. Convolutional neural networks excel at modeling complex data relationships in multi-dimensional parameter spaces, such as that mapped by a combinatorial materials science experiment. Measuring a performance metric in a given materials space provides direct information about (locally) optimal materials but not the underlying materials science that gives rise to the variation in performance. By building a model that predicts performance (in this case photoelectrochemical power generation of a solar fuels photoanode) from materials parameters (in this case composition and Raman signal), subsequent analysis of gradients in the trained model reveals key data relationships that are not readily identified by human inspection or traditional statistical analyses. Human interpretation of these key relationships produces the desired fundamental understanding, demonstrating a framework in which machine learning accelerates data interpretation by leveraging the expertize of the human scientist. We also demonstrate the use of neural network gradient analysis to automate prediction of the directions in parameter space, such as the addition of specific alloying elements, that may increase performance by moving beyond the confines of existing data
Generation of Explicit Knowledge from Empirical Data through Pruning of Trainable Neural Networks
This paper presents a generalized technology of extraction of explicit
knowledge from data. The main ideas are 1) maximal reduction of network
complexity (not only removal of neurons or synapses, but removal all the
unnecessary elements and signals and reduction of the complexity of elements),
2) using of adjustable and flexible pruning process (the pruning sequence
shouldn't be predetermined - the user should have a possibility to prune
network on his own way in order to achieve a desired network structure for the
purpose of extraction of rules of desired type and form), and 3) extraction of
rules not in predetermined but any desired form. Some considerations and notes
about network architecture and training process and applicability of currently
developed pruning techniques and rule extraction algorithms are discussed. This
technology, being developed by us for more than 10 years, allowed us to create
dozens of knowledge-based expert systems. In this paper we present a
generalized three-step technology of extraction of explicit knowledge from
empirical data.Comment: 9 pages, The talk was given at the IJCNN '99 (Washington DC, July
1999
Analysis of Neural Networks in Terms of Domain Functions
Despite their success-story, artificial neural networks have one major disadvantage compared to other techniques: the inability to explain comprehensively how a trained neural network reaches its output; neural networks are not only (incorrectly) seen as a "magic tool" but possibly even more as a mysterious "black box". Although much research has already been done to "open the box," there is a notable hiatus in known publications on analysis of neural networks. So far, mainly sensitivity analysis and rule extraction methods have been used to analyze neural networks. However, these can only be applied in a limited subset of the problem domains where neural network solutions are encountered. In this paper we propose a wider applicable method which, for a given problem domain, involves identifying basic functions with which users in that domain are already familiar, and describing trained neural networks, or parts thereof, in terms of those basic functions. This will provide a comprehensible description of the neural network's function and, depending on the chosen base functions, it may also provide an insight into the neural network' s inner "reasoning." It could further be used to optimize neural network systems. An analysis in terms of base functions may even make clear how to (re)construct a superior system using those base functions, thus using the neural network as a construction advisor
A Robust Interpretable Deep Learning Classifier for Heart Anomaly Detection Without Segmentation
Traditionally, abnormal heart sound classification is framed as a three-stage
process. The first stage involves segmenting the phonocardiogram to detect
fundamental heart sounds; after which features are extracted and classification
is performed. Some researchers in the field argue the segmentation step is an
unwanted computational burden, whereas others embrace it as a prior step to
feature extraction. When comparing accuracies achieved by studies that have
segmented heart sounds before analysis with those who have overlooked that
step, the question of whether to segment heart sounds before feature extraction
is still open. In this study, we explicitly examine the importance of heart
sound segmentation as a prior step for heart sound classification, and then
seek to apply the obtained insights to propose a robust classifier for abnormal
heart sound detection. Furthermore, recognizing the pressing need for
explainable Artificial Intelligence (AI) models in the medical domain, we also
unveil hidden representations learned by the classifier using model
interpretation techniques. Experimental results demonstrate that the
segmentation plays an essential role in abnormal heart sound classification.
Our new classifier is also shown to be robust, stable and most importantly,
explainable, with an accuracy of almost 100% on the widely used PhysioNet
dataset
Artificial Neural Network Pruning to Extract Knowledge
Artificial Neural Networks (NN) are widely used for solving complex problems
from medical diagnostics to face recognition. Despite notable successes, the
main disadvantages of NN are also well known: the risk of overfitting, lack of
explainability (inability to extract algorithms from trained NN), and high
consumption of computing resources. Determining the appropriate specific NN
structure for each problem can help overcome these difficulties: Too poor NN
cannot be successfully trained, but too rich NN gives unexplainable results and
may have a high chance of overfitting. Reducing precision of NN parameters
simplifies the implementation of these NN, saves computing resources, and makes
the NN skills more transparent. This paper lists the basic NN simplification
problems and controlled pruning procedures to solve these problems. All the
described pruning procedures can be implemented in one framework. The developed
procedures, in particular, find the optimal structure of NN for each task,
measure the influence of each input signal and NN parameter, and provide a
detailed verbal description of the algorithms and skills of NN. The described
methods are illustrated by a simple example: the generation of explicit
algorithms for predicting the results of the US presidential election.Comment: IJCNN 202
Translating Feedforward Neural Nets to SOM-like Maps
A major disadvantage of feedforward neural networks is still the difficulty to gain insight into their internal functionality. This is much less the case for, e.g., nets that are trained unsupervised, such as KohonenĀæs self-organizing feature maps (SOMs). These offer a direct view into the stored knowledge, as their internal knowledge is stored in the same format as the input data that was used for training or is used for evaluation. This paper discusses a mathematical transformation of a feed-forward network into a SOMlike structure such that its internal knowledge can be visually interpreted. This is particularly applicable to networks trained in the general classification problem domain
- ā¦