Yujia Li

Exploring Compositional High Order Pattern Potentials for Structured Output Learning

When modeling structured outputs such as image segmentations, prediction can be improved by accurately modeling structure present in the labels. A key challenge is developing tractable models that are able to capture complex high level structure like shape. In this work, we study the learning of a general class of pattern-like high order potential, which we call Compositional High Order Pattern Potentials (CHOPPs). We show that CHOPPs include the linear deviation pattern potentials of Rother et al. [26] and also Restricted Boltzmann Machines (RBMs), we also establish the near equivalence of these two models. Experimentally, we show that performance is affected significantly by the degree of variability present in the datasets, and we define a quantitative variability measure to aid in studying this. We then improve CHOPPs performance in high variability datasets with two primary contributions: (a) developing a loss-sensitive joint learning procedure, so that internal pattern parameters can be learned in conjunction with other model potentials to minimize expected loss, and (b) learning an image-dependent mapping that encourages or inhibits patterns depending on image features. We also explore varying how multiple patterns are composed, and learning convolutional patterns. Quantitative results on challenging highly variable datasets show that the joint learning and image-dependent high order potentials can improve performance.

Feedback-based handwriting recognition from inertial sensor data for wearable devices

This paper presents a novel interactive method for recognizing handwritten words, using the inertial sensor data available on smart watches. The goal is to allow the user to write with a finger, and use the smart watch sensor signals to infer what the user has written. Past work has exploited the similarity of handwriting recognition to speech recognition in order to deploy HMM based methods. In contrast to speech recognition, however, in our scenario, the user can see the individual letters that are recognized on a sequential basis, and provide feedback or corrections after each letter. In this paper, we exploit this key difference to improve the input mechanism over a classical source-channel model. For a small increase in the amount of time required to input a word, we improve recognition accuracy from 59.6% to 91.4% with an implicit feedback mechanism, and to 100% with an explicit feedback mechanism.