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Online Learning of Combinatorial Objects

Holakou Rahmanian
PhD Thesis. UC Santa Cruz.
Publication year: 2018

Abstract. This thesis develops algorithms for learning combinatorial objects. A combinatorial object is a structured concept composed of components. Examples are permutations, Huffman trees, binary search trees and paths in a directed graph. Learning combinatorial objects is a challenging problem: First, the number of combinatorial objects is typically exponential in terms of number of components. Second, the convex hull of these objects is a polytope whose characterization in the original space may have exponentially many facets or a description of the polytope in terms of facets/inequalities may not be even known. Finally, the loss of each object could be a complicated function of its component and may not be simply additive as a function of the components. In this thesis, we explore a wide variety of combinatorial objects and address the challenges above. For each combinatorial object, we go beyond the original space of the problem and introduce auxiliary spaces and representations. The representation of the objects in these auxiliary spaces admits additive losses and polytopes with polynomially many facets. This allows us to extend well-known algorithms like Expanded Hedge and Component Hedge to these combinatorial objects for the first time.

Breathing Rate Prediction Using Finger-tip Sensor

Holakou Rahmanian
Masters Thesis. UC Santa Cruz.
Publication year: 2015

Abstract. Personalized health-care is trending and individuals tend to wear sensors in order to record their own health data. As a part of this trend, any redundancy in the data captured by wearable sensors must be exploited to reduce the number of devices one may wear. In this thesis, we work with a device which senses breathing and pulse through pressure tube and pulse oximetry, respectively. Extracting the dependency between these two measurements, we approximately predict the breathing rate by first reconstructing the breathing signal using the data coming from the finger-tip sensor, and then detecting the peaks in the reconstructed signal. For breathing signal reconstruction, two different techniques are used: (1) applying low- and high-pass filters on the pulse signal (2) training a neural network on a prepared dataset. Our experiments show that neural networks have a better performance comparing to filters in reconstructing the breathing signal, and consequently, predicting the breathing rate.