Not available / text

No description available.

<p>This thesis develops Bayesian latent class models for nested categorical data, e.g., people nested in households. The applications focus on generating synthetic microdata for public release and imputing missing data for household surveys, such as the 2010 U.S. Decennial Census.</p><p>The first contribution is methods for evaluating disclosure risks in fully synthetic categorical data. I quantify disclosure risks by computing Bayesian posterior probabilities that intruders can learn confidential values given the released data and assumptions about their prior knowledge. I demonstrate the methodology on a subset of data from the American Community Survey (ACS). The methods can be adapted to synthesizers for nested data, as demonstrated in later chapters of the thesis.</p><p>The second contribution is a novel two-level latent class model for nested categorical data. Here, I assume that all configurations of groups and units are theoretically possible. I use a nested Dirichlet Process prior distribution for the class membership probabilities. The nested structure facilitates simultaneous modeling of variables at both group and unit levels. I illustrate the modeling by generating synthetic data and imputing missing data for a subset of data from the 2012 ACS household data. I show that the model can capture within group relationships more effectively than standard one-level latent class models.</p><p>The third contribution is a version of the nested latent class model adapted for theoretically impossible combinations, e.g. a household with two household heads or a child older than her biological father. This version assigns zero probability to those impossible groups and units. I present a proof that the Markov Chain Monte Carlo (MCMC) sampling strategy estimates the desired target distribution. I illustrate this model by generating synthetic data and imputing missing data for a subset of data from the 2011 ACS household data. The results indicate that this version can estimate the joint distribution more effectively than the previous version.</p> / Dissertation

Since the Netflix Prize competition, latent factor models (LFMs) have become the comparison ``staples'' for many of the recent recommender methods. Meanwhile, it is still unclear to understand the impact of data preprocessing and updating algorithms on LFMs. The performance improvement of LFMs over baseline approaches, however, hovers at only low percentage numbers. Therefore, it is time for a better understanding of their real power beyond the overall root mean square error (RMSE), which as it happens, lies at a very compressed range, without providing too much chance for deeper insight. We introduce an experiment based handbook of LFMs and reveal data preprocessing and updating algorithms' power. We perform a detailed experimental study regarding the performance of classical staple LFMs on a classical dataset, Movielens 1M, that sheds light on a much more pronounced excellence of LFMs for particular categories of users and items, for RMSE and other measures. In particular, LFMs exhibit surprising and excellent advantages when handling several difficult user and item categories. By comparing the distributions of test ratings and predicted ratings, we show that the performance of LFMs is influenced by rating distribution. We then propose a method to estimate the performance of LFMs for a given rating dataset. Also, we provide a very simple, open-source library that implements staple LFMs achieving a similar performance as some very recent (2013) developments in LFMs, and at the same time being more transparent than some other libraries in wide use. / Graduate

As a new topic in text mining, novelty detection is a natural extension of information retrieval systems, or search engines. Aiming at refining raw search results by filtering out old news and saving only the novel messages, it saves modern people from the nightmare of information overload. One of the difficulties in novelty detection is the inherent ambiguity of language, which is the carrier of information. Among the sources of ambiguity, synonymy proves to be a notable factor. To address this issue, previous studies mainly employed WordNet, a lexical database which can be perceived as a thesaurus. Rather than borrowing a dictionary, we proposed a statistical approach employing Latent Semantic Indexing (LSI) to learn semantic relationship automatically with the help of language resources. To apply LSI which involves matrix factorization, an immediate problem is that the dataset in novelty detection is dynamic and changing constantly. As an imitation of real-world scenario, texts are ranked in chronological order and examined one by one. Each text is only compared with those having appeared earlier, while later ones remain unknown. As a result, the data matrix starts as a one-row vector representing the first report, and has a new row added at the bottom every time we read a new document. Such a changing dataset makes it hard to employ matrix methods directly. Although LSI has long been acknowledged as an effective text mining method when considering semantic structure, it has never been used in novelty detection, nor have other statistical treatments. We tried to change this situation by introducing external text source to build the latent semantic space, onto which the incoming news vectors were projected. We used the Reuters-21578 dataset and the TREC data as sources of latent semantic information. Topics were divided into years and types in order to take the differences between them into account. Results showed that LSI, though very effective in traditional information retrieval tasks, had only a slight improvement to the performances for some data types. The extent of improvement depended on the similarity between news data and external information. A probing into the co-occurrence matrix attributed such a limited performance to the unique features of microblogs. Their short sentence lengths and restricted dictionary made it very hard to recover and exploit latent semantic information via traditional data structure.

Travel Demand Management (TDM) is now considered one of the most important aspects of transportation planning and operation. The prime objective of TDM is to develop a sustainable transportation system utilizing the existing infrastructure. It is now a well known fact that excessive use of single occupancy vehicle causes numerous problems like traffic congestion, environmental pollution etc. Thus, from TDM perspective, it is of great importance to analyze travel behaviour in order to influence people to reduce car use and choose more sustainable modes such as carpool, public transit, park & ride, walk, bike etc. This study attempts an in-depth analysis of commuting mode choice behaviour using workplace commuter survey data from the City of Edmonton. Unlike traditional mode choice models, this study uses both instrumental and latent variables to better understand the choice process and analyzes their sensitivities with respect to TDM policies. / Transportation Engineering

The experiments reported in the present thesis examined the behavioural processes of Pavlovian fear extinction and latent inhibition. The first series of experiments studied the reacquisition of extinguished fear responses following different amounts of extinction training. Rapid reacquisition occurred when rats were reconditioned after moderate extinction, showing that the original learning remained intact across this extinction. In contrast, when reconditioning was given after massive extinction, reconditioned responding was first depressed but then spontaneously recovered over time. This suggests that massive extinction produces a relatively permanent loss of the originally learned responding, while additionally imposes on the extinguished CS a transient latent inhibitory process that prevented the immediate but not the delayed expression of reconditioning. The second series of experiments studied the impact of spontaneous recovery of extinguished fear responses on their additional extinction. These experiments demonstrated that a CS that had time to show spontaneous recovery underwent greater response loss across additional extinction than one lacking recovery. They also showed that an excitor extinguished in compound with a CS showing recovery suffered greater response loss than an excitor extinguished in compound with a CS lacking recovery. Further, extinction of a compound composed of two CSs, one showing recovery and a second lacking recovery, produced greater extinction to the CS that showed recovery. These results show that spontaneous recovery of extinguished responses deepens their extinction through an error-correction mechanism regulated by both common and individual error terms. The third series of experiments studied the spontaneous recovery of latently inhibited and extinguished fear responses in within-subject designs. Using a compound test procedure, a CS that had received extensive preexposure or extensive extinction was found to have undergone greater spontaneous recovery relative to a CS just moderately preexposed or moderately extinguished. A CS given a mixed history of preexposure and extinction also underwent greater recovery relative to a CS just preexposed or just extinguished. These results suggest that both latent inhibition and extinction share a transient depressive process, and that the resulting recovery of responding is proportional to the amount of this depression.

The experiments reported in the present thesis examined the behavioural processes of Pavlovian fear extinction and latent inhibition. The first series of experiments studied the reacquisition of extinguished fear responses following different amounts of extinction training. Rapid reacquisition occurred when rats were reconditioned after moderate extinction, showing that the original learning remained intact across this extinction. In contrast, when reconditioning was given after massive extinction, reconditioned responding was first depressed but then spontaneously recovered over time. This suggests that massive extinction produces a relatively permanent loss of the originally learned responding, while additionally imposes on the extinguished CS a transient latent inhibitory process that prevented the immediate but not the delayed expression of reconditioning. The second series of experiments studied the impact of spontaneous recovery of extinguished fear responses on their additional extinction. These experiments demonstrated that a CS that had time to show spontaneous recovery underwent greater response loss across additional extinction than one lacking recovery. They also showed that an excitor extinguished in compound with a CS showing recovery suffered greater response loss than an excitor extinguished in compound with a CS lacking recovery. Further, extinction of a compound composed of two CSs, one showing recovery and a second lacking recovery, produced greater extinction to the CS that showed recovery. These results show that spontaneous recovery of extinguished responses deepens their extinction through an error-correction mechanism regulated by both common and individual error terms. The third series of experiments studied the spontaneous recovery of latently inhibited and extinguished fear responses in within-subject designs. Using a compound test procedure, a CS that had received extensive preexposure or extensive extinction was found to have undergone greater spontaneous recovery relative to a CS just moderately preexposed or moderately extinguished. A CS given a mixed history of preexposure and extinction also underwent greater recovery relative to a CS just preexposed or just extinguished. These results suggest that both latent inhibition and extinction share a transient depressive process, and that the resulting recovery of responding is proportional to the amount of this depression.

The experiments reported in the present thesis examined the behavioural processes of Pavlovian fear extinction and latent inhibition. The first series of experiments studied the reacquisition of extinguished fear responses following different amounts of extinction training. Rapid reacquisition occurred when rats were reconditioned after moderate extinction, showing that the original learning remained intact across this extinction. In contrast, when reconditioning was given after massive extinction, reconditioned responding was first depressed but then spontaneously recovered over time. This suggests that massive extinction produces a relatively permanent loss of the originally learned responding, while additionally imposes on the extinguished CS a transient latent inhibitory process that prevented the immediate but not the delayed expression of reconditioning. The second series of experiments studied the impact of spontaneous recovery of extinguished fear responses on their additional extinction. These experiments demonstrated that a CS that had time to show spontaneous recovery underwent greater response loss across additional extinction than one lacking recovery. They also showed that an excitor extinguished in compound with a CS showing recovery suffered greater response loss than an excitor extinguished in compound with a CS lacking recovery. Further, extinction of a compound composed of two CSs, one showing recovery and a second lacking recovery, produced greater extinction to the CS that showed recovery. These results show that spontaneous recovery of extinguished responses deepens their extinction through an error-correction mechanism regulated by both common and individual error terms. The third series of experiments studied the spontaneous recovery of latently inhibited and extinguished fear responses in within-subject designs. Using a compound test procedure, a CS that had received extensive preexposure or extensive extinction was found to have undergone greater spontaneous recovery relative to a CS just moderately preexposed or moderately extinguished. A CS given a mixed history of preexposure and extinction also underwent greater recovery relative to a CS just preexposed or just extinguished. These results suggest that both latent inhibition and extinction share a transient depressive process, and that the resulting recovery of responding is proportional to the amount of this depression.

PhD / This thesis describes an interview study of forty five professionally accomplished male and female designers and architects. The study considers how each respondent designs and makes discoveries throughout conceptual design. How they start designing, what they attempt to achieve, the means they employ, how they cope with getting stuck, their breakthroughs and discoveries and the circumstances of these experiences, are the main ingredients of the study. The aim of the research is to estimate the extent to which designing may be regarded as an insightful activity, by investigating experiences of discoveries as reported by the respondents. Throughout the thesis, discoveries or ideas occurring to respondents when they are not actively designing, an apparent outcome of a latent designing or preparation activity, are referred to as cold discoveries. This label is used to distinguish these discoveries from discoveries that emerge in the run of play, when individuals are actively designing. The latter are referred to as hot discoveries. The relative insightfulness of hot and cold discoveries is also investigated. In general, the evidence from the research suggests that designing is significantly insightful. Most respondents (39:45) reported experiences of insights that have contributed to their designing. In addition there is strong evidence that cold discoveries are considerably more important, both quantitatively and qualitatively, than is currently recognized. More than half of the respondents (25:45) reported the experience of cold discoveries, many after disengaging from designing, when they had been stuck. Being stuck means they were experiencing frustration, or had recognised they were not making satisfactory progress in attempts to resolve some aspect of conceptual design. Typically these respondents reported experiencing discoveries while doing other work, performing some physical activity, resting, or very soon after resuming work. They had elected to let ideas come to them, rather than persist in searching and this strategy was successful. Moreover, many respondents (10:45) described positive attributes of cold discoveries using terms such as stronger, more potent, or pushes boundaries, which suggest their cold discoveries are more insightful than their hot discoveries. Many respondents associated their cold discoveries with mental activities such as incubation, a concept identified by Gestalt theorists nearly a century ago. They used a range of informal terms, such as ideas ticking over, or percolating away. These apparently uncontrolled mental experiences, which I refer to generically as latent preparation, varied from one respondent to another in when, where and how they occurred. Latent preparation or its outcomes, in the form of interruptive thoughts, apparently takes place at any time and during different states of consciousness and attentiveness. It appears to be, at different times, unplanned, unintentional, undirected, unnoticed, or unconscious, in combinations, not necessarily all at once. It is clearly not only an unconscious process. This suggests one, or more of the following; 1) that incubation is only a component of latent preparation, or 2) that the conventional view of incubation, as an unconscious process, does not adequately account for the range of insightful experiences of mentally productive people, such as designers, or 3) that the old issue of whether incubation is a conscious, or an unconscious process, is not vital to a systematic investigation of insightful discovery. The thesis concludes by considering prospects for further research and how the research outcomes could influence education. Apart from the findings already described, statements by the respondents about personal attributes, designing, coping with being stuck and discoveries, were wide ranging, resourceful and down-to-earth, suggesting there are many ways for individuals to become proficient, creative designers at the high end of their profession. A major implication for future research is that latent preparation may be found as readily among highly motivated and skilled individuals in other occupations unrelated to architecture or designing. The evidence of the research so far suggests there is much to be learned about latent preparation that can be usefully applied, for the benefit of individuals aiming to be designers, or simply wanting to become more adept at intervening, transforming and managing unexpected and novel situations of any kind.