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Published byHilary Cole Modified over 9 years ago
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Chapter 15 Probabilistic Reasoning over Time
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Chapter 15, Sections 1-5 Outline Time and uncertainty Inference: ltering, prediction, smoothing Hidden Markov models Kalman lters (a brief mention) Dynamic Bayesian networks Particle ltering
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Time and uncertainty The world changes; we need to track and predict it Diabetes management vs vehicle diagnosis Basic idea: copy state and evidence variables for each time step
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Markov processes (Markov chains)
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Example
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Inference tasks
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Filtering
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Filtering example
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Smoothing
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Smoothing example
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Most likely explanation
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Viterbi example
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Hidden Markov models
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Country dance algorithm
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Kalman lters
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Updating Gaussian distributions
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Simple 1-D example
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General Kalman update
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2-D tracking example: ltering
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2-D tracking example: smoothing
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Where it breaks
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Dynamic Bayesian networks
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DBNs vs. HMMs
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DBNs vs Kalman lters
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Exact inference in DBNs
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Likelihood weighting for DBNs
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Particle ltering
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Particle ltering contd.
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Particle ltering performance
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Chapter 15, Sections 1-5 Summary
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Chapter 15, Section 6 Outline Speech as probabilistic inference Speech sounds Word pronunciation Word sequences
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Speech as probabilistic inference
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Phones
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Speech sounds
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Phone models
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Phone model example
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Word pronunciation models
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Isolated words
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Continuous speech
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Language model
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Combined HMM
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DBNs for speech recognition
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Chapter 15, Section 6 Summary Since the mid-1970s, speech recognition has been formulated as probabilistic inference Evidence = speech signal, hidden variables = word and phone sequences "Context" effects (coarticulation etc.) are handled by augmenting state Variability in human speech (speed, timbre, etc., etc.) and background noise make continuous speech recognition in real settings an open problem
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