This study was motivated by the desire to contribute to the understanding of the movement of house prices and the role of the so-called economic ‘fundamentals’ in the housing market, especially within an Australian context. The core objective of this thesis is to aid understanding of the economic and other mechanisms by which the Australian housing market operates. We do this by constructing an analytical framework, or model, that encompasses the most important characteristics of the housing market. This thesis examines two important aspects of the Australian housing market: movements of house prices and changes in the net capital stock of dwellings in Australia. Movements of house prices are modelled from two perspectives: firstly, using the ‘fundamental’ approach, which explains the phenomena by changes in such ‘fundamental’ explanatory variables as income, interest rates, population and prices of building materials, and secondly, by analysing spatial interdependence of house prices in Australian capital cities. Changes in stock of dwellings were also modelled on the basis of a ‘fundamental’ approach by states and for Australia as a whole...

Thesis (M. Soc. Sc.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 90-94).

Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 242-260).

Thesis (M.Soc.Sc.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 90-94) Also available in print.

by Seyyed J. Golestaani. / Bibliography: p.107-108. / Prepared under Grant NSF-ENG75-14103. Originally presented as the author's thesis, (M.S.) in the M.I.T. Dept. of Electrical Engineering and Computer Science, 1976.

Σήμερα, σε όλα σχεδόν τα τηλεπικοινωνιακά συστήματα τα οποία προορίζονται για αποστολή δεδομένων σε υψηλούς ρυθμούς, έχουν υιοθετηθεί κώδικες διόρθωσης λαθών για την αύξηση της αξιοπιστίας τους και τη μείωση της απαιτούμενης ισχύος εκπομπής τους. Οι κώδικες αυτοί δίνουν τη δυνατότητα ανίχνευσης και διόρθωσης των λαθών που μπορεί να δημιουργήσει το μέσο μετάδοσης (κανάλι) σε κάποιο τμήμα πληροφορίας που μεταφέρεται μέσω του τηλεπικοινωνιακού δικτύου. Μία κατηγορία τέτοιων κωδίκων, και μάλιστα με εξαιρετικές επιδόσεις, είναι η οικογένεια των LDPC (Low Density Parity Check) κωδίκων. Πρόκειται για γραμμικούς μπλοκ κώδικες, με απόδοση πολύ κοντά στο όριο Shannon. Στην παρούσα διπλωματική μελετώνται οι κώδικες LDPC και σχετικές αρχιτεκτονικές υλικού. Oι κώδικες LDPC χρησιμοποιούνται όλο και περισσότερο σε εφαρμογές που απαιτούν αξιόπιστη και υψηλής απόδοσης μετάδοση, υπό την παρουσία ισχυρού θορύβου. Η κατασκευή τους στηρίζεται στη χρήση πινάκων ελέγχου ισοτιμίας χαμηλής πυκνότητας, ενώ η αποκωδικοποίηση εκτελείται με τη χρήση επαναληπτικών αλγορίθμων. Σε υψηλά επίπεδα θορύβου παρουσιάζουν πολύ καλή διορθωτική ικανότητα, αλλά υστερούν σε χαμηλότερα επίπεδα θορύβου, όπου υποφέρουν από το φαινόμενο του error floor. Στη συγκεκριμένη εργασία μελετάται εκτενώς μία αλγεβρική μέθοδος για την κατασκευή regular LDPC κωδίκων που βασίζεται σε κώδικες Reed-Solomon με δύο σύμβολα πληροφορίας. Η μέθοδος αυτή μας επιτρέπει την κατασκευή ενός πίνακα ελέγχου ισοτιμίας Η για τον κώδικα LDPC, όπου το διάγραμμα Tanner που του αντιστοιχεί δεν περιέχει κύκλους μήκους 4 (ελάχιστο μήκος κύκλου 6). Οι κύκλοι μικρού μήκους στο διάγραμμα Tanner «εγκλωβίζουν» τον αποκωδικοποιητή σε καταστάσεις που δεν μπορεί να ανιχνεύσει και να διορθώσει τα λάθη που δημιουργήθηκαν στη μετάδοση. Έτσι χρησιμοποιώντας την παραπάνω μέθοδο μπορούμε να κατασκευάσουμε απλούς σε δομή κώδικες, που σε συνδυασμό με τους επαναληπτικούς αλγορίθμους αποκωδικοποίησης οδηγούν σε αποκωδικοποιητές με εξαιρετικές διορθωτικές ικανότητες και εμφάνιση error floor σε πολύ χαμηλές τιμές του BER. Ακόμα, αυτού του τύπου οι πίνακες ισοτιμίας επιβάλλουν μία συγκεκριμένη δομή για το γεννήτορα πίνακα G που χρησιμοποιείται για την κωδικοποίηση. Για το λόγο αυτό μελετάται επίσης ο τρόπος για να κατασκευάσουμε ένα συστηματικό πίνακα G, ο οποίος απλουστεύει κατά πολύ τη διαδικασία της κωδικοποίησης. Όλες οι παραπάνω διαδικασίες εφαρμόζονται για την κατασκευή του κώδικα (2048,1723) RS-LDPC. Πρόκειται για έναν κώδικα ρυθμού 0,84 που χρησιμοποιείται από το πρότυπο 802.3an της IEEE για το 10GBASE-T Ethernet και παρουσιάζει ιδιαίτερο ενδιαφέρον λόγω των επιδόσεών του. Για τον κώδικα αυτό προτείνεται σχεδίαση για τον κωδικοποιητή και τον αποκωδικοποιητή καθώς και για όλα τα εξωτερικά κυκλώματα που απαιτούνται ώστε να δημιουργηθεί ένα ολοκληρωμένο σύστημα αποστολής, λήψης και διόρθωσης δεδομένων. Έχοντας όλο το υπόβαθρο για την κατασκευή ενός RS-LDPC συστήματος κωδικοποίησης-αποκωδικοποίησης, υλοποιήσαμε τη σχεδίαση του συστήματος σε κώδικα VHDL ενώ εκτελέστηκαν οι απαραίτητες εξομοιώσεις (Modelsim). Στη συνέχεια εκτελέστηκαν οι διαδικασίες της σύνθεσης (εργαλείο XST του Xilinx ISE) και της πλήρους υλοποίησης σε fpga (Virtex 5 XC5VLX330T-1FF1738), δίνοντας μας έτσι τη δυνατότητα διεξαγωγής ταχύτατων εξομοιώσεων ειδικά σε χαμηλά επίπεδα θορύβου σε σχέση με τις αντίστοιχες υλοποιήσεις σε λογισμικό (MATLAB). Πραγματοποιώντας πειράματα στο υλικό παρατηρούμε τη διορθωτική ικανότητα του αλγορίθμου αποκωδικοποίησης και συγκρίνουμε τα αποτελέσματα με αυτά των υλοποιήσεων σε λογισμικό. Επίσης μελετάται ο τρόπος μεταβολής της διορθωτικής ικανότητας του αλγορίθμου ανάλογα με τον αριθμό των επαναλήψεων που εκτελεί. Τέλος, πήραμε κάποιες μετρήσεις για το throughput του αποκωδικοποιητή, ώστε σε περίπτωση που θέλουμε να πετύχουμε ένα συγκεκριμένο ρυθμό επεξεργασίας δεδομένων να μπορούμε να υπολογίσουμε τον αριθμό των αποκωδικοποιητών που θα χρειαστούμε. / Nowadays, almost every telecommunication system that aims to achieve high transmission rates has adopted error correction codes in order to increase its reliability while decreasing the required power of transmission. The information signal is transmitted over a communication channel with the presence of noise. Error correction codes allow systems to detect and correct errors that occurred to the information signal due to the noise. LDPC (Low Density Parity Check) codes compose a large family of error correcting linear block codes with great performance, close to the Shannon limit. In this thesis we analyze LDPC codes and the corresponding hardware designs. LDPC codes are used in applications that require reliable and highly efficient transmission under high levels of noise. Any LDPC code is fully defined by a sparse parity-check-matrix and all of them use iterative belief propagation techniques for the decoding process. In general, LDPC codes perform very well in high levels of noise, but in very low levels they suffer from “error floor” effect. First we present a thorough analysis of an algebraic method for constructing regular LDPC codes based on Reed-Solomon codes with two information symbols. This construction method results in a class of LDPC codes which are free of cycles of length 4 in their Tanner graphs (so the girth of their Tanner graphs is at least 6). The existence of circles with length 4 in the Tanner graph “traps” the decoder in states that it cannot detect and correct any error occuring in the transmitted codeword. So by using the previous constructing method we can create simply structured codes which, combined with iterative decoding algorithms, may provide decoders with great performance and error floor at very low levels of BER. Furthermore, this type of decoders requires that the generator matrix G used for the encoding process of the system must have specific structural properties. For this reason we are going to study the way of constructing a proper systematic generator matrix which also simplifies the decoding process. All the previous stages are carried out in order to construct the (2048, 1723) RS-LDPC code. This code was adopted in 802.3an IEEE standard for the 10GBASE-T and is of high interest due to its remarkable efficiency. For this code we demonstrate a specific implementation for the encoder, decoder and all the additional components required in order to design a complete transmitter-receiver system, coupled with error correction capabilities. We utilize the above mentioned background so as to implement our design in VHDL code and run the proper simulations (Modelsim tool). Later on we synthesized (XST tool, Xilinx ISE) and implemented our design on an fpga board (Virtex 5 XC5VLX330T-1FF1738). This enabled us to accomplish rapid simulation times, especially under low level of noise in contrast to the corresponding software implementations (MATLAB). We evaluate the error correction capability of the decoding algorithm by running experiments in hardware and we compare these results with software implementations. Moreover we observe how the effectiveness of the decoding algorithm is affected by its number of iterations. Finally, we measure the decoder throughput so that in case we want to achieve a specific decoding rate we are able to estimate the required number of decoders for this rate.

This dissertation explores the problem of energy estimation in supervised Non-Intrusive Load Monitoring (NILM). NILM refers to a set of techniques used to estimate the electricity consumed by individual loads in a building from measurements of the total electrical consumption. Most commonly, NILM works by first attributing any significant change in the total power consumption (also known as an event) to a specific load and subsequently using these attributions (i.e. the labels for the events) to estimate energy for each load. For this last step, most proposed solutions in the field impart simplifying assumptions to make the problem more tractable. This has severely limited the practicality of the proposed solutions. To address this knowledge gap, we present a framework for creating appliance models based on classification labels and aggregate power measurements that can help relax many of these assumptions. Within the framework, we model the problem of utilizing a sequence of event labels to generate energy estimates as a broader class of problems that has two major components (i) With the understanding that the labels arise from a process with distinct states and state transitions, we estimate the underlying Finite State Machine (FSM) model that most likely generated the observed sequence (ii) We allow for the observed sequence to have errors, and present an error correction algorithm to detect and correct them. We test the framework on data from 43 appliances collected from 19 houses and find that it improves errors in energy estimates when compared to the case with no correction in 19 appliances by a factor of 50, leaves 17 appliances unchanged, and negatively impacts 6 appliances by a factor of 1.4. This approach of utilizing event sequences to estimate energy has implications in virtual metering of appliances as well. In a case study, we utilize this framework in order to substitute the need of plug-level sensors with cheap and easily deployable contacless sensors, and find that on the 6 appliances virtually metered using magnetic field sensors, the inferred energy values have an average error of 10:9%.

The modeling of transport behavior of charged particles carried out in our laboratory is based on classical continuum electro kinetic theory. It is applied to a variety of systems from small electrolyte ions to macromolecules including peptides, DNA and nanoparticles. Systems range from weakly charged particles to highly charged ones. Transport properties studied include conductance, electrophoresis, and diffusion. In this dissertation, the conductance of polyvalent electrolytes ions is studied both by a “small ion” model [R.M. Fuoss, L. Onsager, J. Phys. Chem. 61 (1957) 668] and “large ion” model [R.W. O’Brien, L.R. White, J. Chem. Soc. Faraday Trans. 2 (74) (1978) 1607)]. Also, the coarse-grained continuum primitive model is developed and used to characterize the titration and electrical conductance behavior of aqueous solutions of fullerene hexa-malonic acid, which is a highly charged electrolyte with an absolute valence charge as high as 12. Free solution electrophoresis is closely related to conductance and a coarse-grained bead modeling methodology, BMM, developed in the Allison’s laboratory starting in 2006, is generalized to characterize peptide systems with respect to the charge, conformation, and possibly specific interactions with components of the BGE. For weakly charged peptides, the electrostatic potential is treated at the level of linear Poisson-Boltzmann equation, which predicts the electrophoretic mobility with considerable accuracy [S. Allison, H. Pei, U. Twahir, H. Wu, J. Sep. Sci., 2010, 33(16):2430-2438], but fails for highly charged systems. A new nonlinear Poisson-Boltzmann, NLPB-BM procedure is developed and applied to the free solution electrophoretic mobility of low molecular mass oligolysines. The difficulty of highly charged systems is twofold: more complex handeling of electrostatics and accounting for the relaxation effect. Both issues are addressed in this dissertation. A related problem we investigated deals with the retarding influence of a gel on the rotational motion of a macromolecule. This is investigated within the framework of the Effective Medium (EM) model and is applied to examine the electric birefringence decay of a 622 base pair DNA fragment in an agarose gel. Modeling is also compared with experiment.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Power utilities are expected to keep the cost of electricity as low as possible. They are also expected to be environmentally friendly and, amongst other things, not to produce unacceptable audible noise. When the electric field on a conductor is high enough corona is produced and this is accompanied by audible noise. Air pressure, which is directly related to altitude, has an effect on the voltage at which corona will start. It is more difficult to ionise the air at sea level (high air pressure) than at high altitude (low air pressure). Altitude does not only affect the corona inception voltage, but also the intensity of the audible noise. A thorough scan of literature revealed that there is very little evidence of prior research work on the effect of air density on corona under fair weather (dry) conditions. In South Africa, transmission lines are built at altitudes higher than 1800 m above sea level. The cost of a 400 kV line is in the region of R2M per km. It is important to predict the noise levels under a proposed line accurately, before it is energised. This research indicated that the altitude correction for conductor corona audible noise, under dry conditions, might be steeper than the general accepted correction of 1 dB/300m. This correction, however, appears to be valid for heavy rain conditions. Under heavy rain conditions the corona is mainly determined by the water droplets, whereas under dry conditions the condition of the conductor plays the biggest role. The air density therefore has a bigger effect on the corona performance under dry conditions. The implication of a steeper altitude correction for dry conditions is that too low noise levels will be predicted for a higher altitude, which could lead to complaints. On the other hand, predictions for lower altitudes will be too conservative. / AFRIKAANSE OPSOMMING: Daar word van kragvoorsieners verwag om die koste van elektrisiteit so laag as moontlik te hou. Hulle is verder onder druk om omgewingsvriendelik te wees en om onder andere nie onaanvaarbare hoorbare geraas te veroorsaak nie. Wanneer die elektriese veld op ‘n geleier hoog genoeg is, kan korona ontstaan wat dan hoorbare geraas veroorsaak. Die lugdruk, en daarom die hoogte bo seevlak, beïnvloed die spanning waarby ‘n geleier in korona sal gaan. Dit is moeiliker om die lug te ioniseer by seevlak (hoë lugdruk) as hoog bo seevlak (lae lugdruk). Die hoogte bo seevlak beïnvloed daarom nie net die spanning waarby korona sal begin nie maar ook die intensiteit van die hoorbare geraas. Dit wil voorkom of die effek van hoogte bo seevlak, op hoorbare geraas, a.g.v. geleier korona tot op datum baie skraps nagevors is. Baie min kon in die literatuur gevind word op die effek onder droë toestande. In Suid-Afrika is dit nodig om transmissielyne op hoogtes van 1800 m en hoër te bou. So ‘n lyn (400 kV) kos in die omgewing van R2M per km. Dit is daarom van uiterste belang om die geraasvlakke wat ‘n beplande lyn sal veroorsaak, akkuraat te bepaal, voordat so ‘n lyn aangeskakel word. Hierdie navorsing het gewys dat die effek van hoogte bo seespieël op hoorbare korona geraas onder droë toestande groter kan wees as wat algemene aanvaar word. Die helling van die korreksiefaktor vir hoogte bo seevlak blyk steiler as 1 dB/300 m te wees vir droë toestande. Die implikasie hiervan is dat geraas voorspellings vir hoër hoogtes bo seespieël te laag sal wees en die vir lae hoogtes te konserwatief kan wees. Die navorsing stem egter saam met die korreksiefaktor van 1 dB/300 m onder swaar reën toestande. Dit wil voorkom of die invloed van die waterdruppels op geleier korona groter is as lugdruk. Onder droë toestande speel die toestand van die geleier 'n groter rol en is die effek van lugdruk groter.

Thesis (MScEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: The increasing popularity of microblogging services such as Twitter means that more and more unstructured data is available for analysis. The informal language usage in these media presents a problem for traditional text mining and natural language processing tools. We develop a pre-processor to normalise this noisy text so that useful information can be extracted with standard tools. A system consisting of a tokeniser, out-of-vocabulary token identifier, correct candidate generator, and N-gram language model is proposed. We compare the performance of generative and discriminative probabilistic models for these different modules. The effect of normalising the training and testing data on the performance of a tweet sentiment classifier is investigated. A linear-chain conditional random field, which is a discriminative model, is found to work better than its generative counterpart for the tokenisation module, achieving a 0.76% character error rate compared to 1.41% for the finite state automaton. For the candidate generation module, however, the generative weighted finite state transducer works better, getting the correct clean version of a word right 36% of the time on the first guess, while the discriminatively trained hidden alignment conditional random field only achieves 6%. The use of a normaliser as a pre-processing step does not significantly affect the performance of the sentiment classifier. / AFRIKAANSE OPSOMMING: Mikro-webjoernale soos Twitter word al hoe meer gewild, en die hoeveelheid ongestruktureerde data wat beskikbaar is vir analise groei daarom soos nooit tevore nie. Die informele taalgebruik in hierdie media maak dit egter moeilik om tradisionele tegnieke en bestaande dataverwerkingsgereedskap toe te pas. ’n Stelsel wat hierdie ruiserige teks normaliseer word ontwikkel sodat bestaande pakkette gebruik kan word om die teks verder te verwerk. Die stelsel bestaan uit ’n module wat die teks in woordeenhede opdeel, ’n module wat woorde identifiseer wat gekorrigeer moet word, ’n module wat dan kandidaat korreksies voorstel, en ’n module wat ’n taalmodel toepas om die mees waarskynlike skoon teks te vind. Die verrigting van diskriminatiewe en generatiewe modelle vir ’n paar van hierdie modules word vergelyk en die invloed wat so ’n normaliseerder op die akkuraatheid van ’n sentimentklassifiseerder het word ondersoek. Ons bevind dat ’n lineêre-ketting voorwaardelike toevalsveld—’n diskriminatiewe model — beter werk as sy generatiewe eweknie vir tekssegmentering. Die voorwaardelike toevalsveld-model behaal ’n karakterfoutkoers van 0.76%, terwyl die toestandsmasjien-model 1.41% behaal. Die toestantsmasjien-model werk weer beter om kandidaat woorde te genereer as die verskuilde belyningsmodel wat ons geïmplementeer het. Die toestandsmasjien kry 36% van die tyd die regte weergawe van ’n woord met die eerste raaiskoot, terwyl die diskriminatiewe model dit slegs 6% van die tyd kan doen. Laastens het ons bevind dat die vooraf normalisering van Twitter boodskappe nie ’n beduidende effek op die akkuraatheid van ’n sentiment klassifiseerder het nie.