51 research outputs found
Symbol-by-symbol APP decoding of the Golay code and iterative decoding of concatenated Golay codes
An efficient coset based symbol-by-symbol soft-in/soft-out a posteriori probability (APP) decoding algorithm is presented for the Golay code. Its application in the iterative decoding of concatenated Golay codes is analyzed.published_or_final_versio
Document Meta-Information as Weak Supervision for Machine Translation
Data-driven machine translation has advanced considerably since the first pioneering work
in the 1990s with recent systems claiming human parity on sentence translation for highresource tasks. However, performance degrades for low-resource domains with no available
sentence-parallel training data. Machine translation systems also rarely incorporate the
document context beyond the sentence level, ignoring knowledge which is essential for
some situations. In this thesis, we aim to address the two issues mentioned above by
examining ways to incorporate document-level meta-information into data-driven machine
translation. Examples of document meta-information include document authorship and
categorization information, as well as cross-lingual correspondences between documents,
such as hyperlinks or citations between documents. As this meta-information is much more
coarse-grained than reference translations, it constitutes a source of weak supervision for
machine translation. We present four cumulatively conducted case studies where we devise
and evaluate methods to exploit these sources of weak supervision both in low-resource
scenarios where no task-appropriate supervision from parallel data exists, and in a full
supervision scenario where weak supervision from document meta-information is used to
supplement supervision from sentence-level reference translations. All case studies show
improved translation quality when incorporating document meta-information
Timing is everything: A spatio-temporal approach to the analysis of facial actions
This thesis presents a fully automatic facial expression analysis system based on the Facial Action
Coding System (FACS). FACS is the best known and the most commonly used system to describe
facial activity in terms of facial muscle actions (i.e., action units, AUs). We will present our research
on the analysis of the morphological, spatio-temporal and behavioural aspects of facial expressions.
In contrast with most other researchers in the field who use appearance based techniques, we use a
geometric feature based approach. We will argue that that approach is more suitable for analysing
facial expression temporal dynamics. Our system is capable of explicitly exploring the temporal
aspects of facial expressions from an input colour video in terms of their onset (start), apex (peak)
and offset (end).
The fully automatic system presented here detects 20 facial points in the first frame and tracks them
throughout the video. From the tracked points we compute geometry-based features which serve as
the input to the remainder of our systems. The AU activation detection system uses GentleBoost
feature selection and a Support Vector Machine (SVM) classifier to find which AUs were present in an
expression. Temporal dynamics of active AUs are recognised by a hybrid GentleBoost-SVM-Hidden
Markov model classifier. The system is capable of analysing 23 out of 27 existing AUs with high
accuracy.
The main contributions of the work presented in this thesis are the following: we have created a
method for fully automatic AU analysis with state-of-the-art recognition results. We have proposed
for the first time a method for recognition of the four temporal phases of an AU. We have build the
largest comprehensive database of facial expressions to date. We also present for the first time in the
literature two studies for automatic distinction between posed and spontaneous expressions
Error-Correction Coding and Decoding: Bounds, Codes, Decoders, Analysis and Applications
Coding; Communications; Engineering; Networks; Information Theory; Algorithm
Modem design for digital satellite communications
The thesis is concerned with the design of a phase-shift keying system for a
digital modem, operating over a satellite link. Computer simulation tests and
theoretical analyses are used to assess the proposed design.
The optimum design of both transmitter and receiver filters for the system to be
used in the modem are discussed. Sinusoidal roll-off spectrum with different roll-off
factor and optimum truncation lengths of the sample impulse response are designed
for the proposed scheme to approximate to the theoretical ideal. It has used an EF
bandpass filter to band limit the modulated signal, which forms part of the satellite
channel modelling. The high power amplifier (HPA) at the earth station has been
used in the satellite channel modelling due to its effect in introducing nonlinear AMAM
and AM-PM conversion effects and distortion on the transmitted signal from the
earth station. The satellite transponder is assumed to be operating in a linear mode.
Different phase-shift keying signals such as differentially encoded quaternary
phase-shift keying (DEQPSK), offset quaternary phase-shift keying (OQPSK) and
convolutionally encoded 8PSK (CE8PSK) signals are analysed and discussed in the
thesis, when the high power amplifier (HPA) at the earth station is operating in a
nonlinear mode. Convolutional encoding is discussed when applied to the system
used in the modem, and a Viterbi -algorithm decoder at the receiver has been used, for
CE8PSK signals for a nonlinear satellite channel. A method of feed-forward
synchronisation scheme is designed for carrier recovery in CE8PSK receiver.
The thesis describes a method of baseband linearizing the baseband signal in
order to reduce the nonlinear effects caused by the HPA at the earth station. The
scheme which compensates for the nonlinear effects of the HPA by predistorting the
baseband signal prior to modulation as opposed to correcting the distortion after
modulation, thus reducing the effects of nonlinear distortion introduced by the HPA.
The results of the improvement are presented.
The advanced technology of digital signal processors (DSPs) has been used in the implementation of the demodulation and digital filtering parts of the modem
replacing large parts of conventional circuits. The Viterbi-algorithm decoder for
CE8PSK signals has been implemented using a digital signal processor chip, giving excellent performance and is a cost effective and easy way for future developments
and any modifications,
The results showed that, by using the various studied techniques, as well as the
implementation of digital signal processor chip in parts of the modem, a potentially
more cost effective modem can be obtained
Harmonized-Multinational qEEG Norms (HarMNqEEG)
This paper extends the frequency domain quantitative electroencephalography (qEEG) methods pursuing higher sensitivity to detect Brain Developmental Disorders. Prior qEEG work lacked integration of cross-spectral information omitting important functional connectivity descriptors. Lack of geographical diversity precluded accounting for site-specific variance, increasing qEEG nuisance variance. We ameliorate these weaknesses. i) Create lifespan Riemannian multinational qEEG norms for cross-spectral tensors. These norms result from the HarMNqEEG project fostered by the Global Brain Consortium. We calculate the norms with data from 9 countries, 12 devices, and 14 studies, including 1564 subjects. Instead of raw data, only anonymized metadata and EEG cross-spectral tensors were shared. After visual and automatic quality control, developmental equations for the mean and standard deviation of qEEG traditional and Riemannian DPs were calculated using additive mixed-effects models. We demonstrate qEEG "batch effects" and provide methods to calculate harmonized z-scores. ii) We also show that the multinational harmonized Riemannian norms produce z-scores with increased diagnostic accuracy to predict brain dysfunction at school-age produced by malnutrition only in the first year of life. iii) We offer open code and data to calculate different individual z-scores from the HarMNqEEG dataset. These results contribute to developing bias-free, low-cost neuroimaging technologies applicable in various health settings
Publications of the Jet Propulsion Laboratory, 1979
This bibliography includes 1004 technical reports, released during calendar year 1979, that resulted from scientific and engineering work performed, or managed, by the Jet Propulsion Laboratory. Three classes of publications are included: (1) JPL Publications; (2) articles published in the open literature; and (3) articles from the bimonthly Deep Space Network Progress Report. The publications are indexed by: (1) author, (2) subject, and (3) publication type and number. A descriptive entry appears under the name of each author of each publication; an abstract is included with the entry for the primary (first listed) author. Unless designated otherwise, all publications listed are unclassified
Max-log-MAP filtering algorithm for decoding product F24 code
This paper presents a symbol-by-symbol decoding method for the F24 code. It forms the core part of an iterative Max-Log-MAP filtering algorithm for the product F24 code and noticeable coding gain is observed by simulation. The complexity of the proposed algorithm is very modest. The relatively short frame length of the product F24 code can be an advantage for its applications in some communication systems.link_to_subscribed_fulltex
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