Classification of SD-OCT Volumes using Local Binary Patterns: Experimental Validation for DME Detection

International audienceThis paper addresses the problem of automatic classification of Spectral Domain OCT (SD-OCT) data for automatic identification of patients with Diabetic Macular Edema (DME) versus normal subjects. Optical Coherence Tomography (OCT) has been a valuable diagnostic tool for DME, which is among the most common causes of irreversible vision loss in individuals with diabetes. Here, a classification framework with five distinctive steps is proposed and we present an extensive study of each step. Our method considers combination of various pre-processings in conjunction with Local Binary Patterns (LBP) features and different mapping strategies. Using linear and non-linear classifiers, we tested the developed framework on a balanced cohort of 32 patients. Experimental results show that the proposed method outperforms the previous studies by achieving a Sensitivity (SE) and Specificity (SP) of 81.2% and 93.7%, respectively. Our study concludes that the 3D features and high-level representation of 2D features using patches achieve the best results. However, the effects of pre-processing is inconsistent with respect to different classifiers and feature configurations

Microgravity measurement in space using imaging techniques.

The proposal is made that very small changes in gravitational field could be detected by monitoring a cell of heated fluid. Variations in gravity would be observed by their effect on the convection in the fluid cell. It is proposed that the convection patterns be observed by using an interferometer to image the temperature gradient in the fluid by utilising the effect of temperature variations on the refractive index of the fluid. It was proposed that this system may be able to detect changes in the Earth's gravitational field from orbit. The possibility of using the NASA GAS programme to perform a space flight test of this proposal was suggested. Activities in this programme were therefore surveyed and a proposal made. The primary experimental results were recorded in the form of convection images which were later processed on the ground to extract information. Research has been carried out in this area as investigation has shown that existing image processing techniques are not suitable to process the anticipated fringe images. Meanwhile design and development of a GAS experiment was performed. This was undertaken in liaison with NASA in order to achieve the required safety approvals for flight. Subsequently the flight experiment was performed aboard the Space Shuttle Endeavour during the STS-77 mission launched on the 19th May 1996. As a result of this project an image processing system for the analysis of interferogram images of convection has been developed and an experiment to image convection in microgravity, with a view to analysing its use for the detection of changes in gravity has been performed

A COLLABORATIVE FILTERING APPROACH TO PREDICT WEB PAGES OF INTEREST FROMNAVIGATION PATTERNS OF PAST USERS WITHIN AN ACADEMIC WEBSITE

This dissertation is a simulation study of factors and techniques involved in designing hyperlink recommender systems that recommend to users, web pages that past users with similar navigation behaviors found interesting. The methodology involves identification of pertinent factors or techniques, and for each one, addresses the following questions: (a) room for improvement; (b) better approach, if any; and (c) performance characteristics of the technique in environments that hyperlink recommender systems operate in. The following four problems are addressed:Web Page Classification. A new metric (PageRank × Inverse Links-to-Word count ratio) is proposed for classifying web pages as content or navigation, to help in the discovery of user navigation behaviors from web user access logs. Results of a small user study suggest that this metric leads to desirable results.Data Mining. A new apriori algorithm for mining association rules from large databases is proposed. The new algorithm addresses the problem of scaling of the classical apriori algorithm by eliminating an expensive joinstep, and applying the apriori property to every row of the database. In this study, association rules show the correlation relationships between user navigation behaviors and web pages they find interesting. The new algorithm has better space complexity than the classical one, and better time efficiency under some conditionsand comparable time efficiency under other conditions.Prediction Models for User Interests. We demonstrate that association rules that show the correlation relationships between user navigation patterns and web pages they find interesting can be transformed intocollaborative filtering data. We investigate collaborative filtering prediction models based on two approaches for computing prediction scores: using simple averages and weighted averages. Our findings suggest that theweighted averages scheme more accurately computes predictions of user interests than the simple averages scheme does.Clustering. Clustering techniques are frequently applied in the design of personalization systems. We studied the performance of the CLARANS clustering algorithm in high dimensional space in relation to the PAM and CLARA clustering algorithms. While CLARA had the best time performance, CLARANS resulted in clusterswith the lowest intra-cluster dissimilarities, and so was most effective in this regard

Modelo de acesso a fontes em linguagem natural no governo electrónico

Doutoramento em Engenharia InformáticaFor the actual existence of e-government it is necessary and crucial to provide public information and documentation, making its access simple to citizens. A portion, not necessarily small, of these documents is in an unstructured form and in natural language, and consequently outside of which the current search systems are generally able to cope and effectively handle. Thus, in thesis, it is possible to improve access to these contents using systems that process natural language and create structured information, particularly if supported in semantics. In order to put this thesis to test, this work was developed in three major phases: (1) design of a conceptual model integrating the creation of structured information and making it available to various actors, in line with the vision of e-government 2.0; (2) definition and development of a prototype instantiating the key modules of this conceptual model, including ontology based information extraction supported by examples of relevant information, knowledge management and access based on natural language; (3) assessment of the usability and acceptability of querying information as made possible by the prototype - and in consequence of the conceptual model - by users in a realistic scenario, that included comparison with existing forms of access. In addition to this evaluation, at another level more related to technology assessment and not to the model, evaluations were made on the performance of the subsystem responsible for information extraction. The evaluation results show that the proposed model was perceived as more effective and useful than the alternatives. Associated with the performance of the prototype to extract information from documents, comparable to the state of the art, results demonstrate the feasibility and advantages, with current technology, of using natural language processing and integration of semantic information to improve access to unstructured contents in natural language. The conceptual model and the prototype demonstrator intend to contribute to the future existence of more sophisticated search systems that are also more suitable for e-government. To have transparency in governance, active citizenship, greater agility in the interaction with the public administration, among others, it is necessary that citizens and businesses have quick and easy access to official information, even if it was originally created in natural language.Para a efectiva existência de governo electrónico é necessário e crucial a disponibilização de informação e documentação pública e tornar simples o acesso a esta pelos cidadãos. Uma parte, não necessariamente pequena, destes documentos encontra-se sob uma forma não estruturada e em linguagem natural e, consequentemente, fora do que os sistemas de pesquisa actuais conseguem em geral suportar e disponibilizar eficazmente. Assim, em tese, é possível melhorar o acesso a estes conteúdos com recurso a sistemas que processem linguagem natural e que sejam capazes de criar informação estruturada, em especial se suportados numa semântica. Com o objectivo de colocar esta tese à prova, o desenvolvimento deste trabalho integrou três grandes fases ou vertentes: (1) Criação de um modelo conceptual integrando a criação de informação estruturada e a sua disponibilização para vários actores, alinhado com a visão do governo electrónico 2.0; (2) Definição e desenvolvimento de um protótipo instanciando os módulos essenciais deste modelo conceptual, nomeadamente a extracção de informação suportada em ontologias e exemplos de informação relevante, gestão de conhecimento e acesso baseado em linguagem natural; (3) Uma avaliação de usabilidade e aceitabilidade da consulta à informação tornada possível pelo protótipo – e em consequência do modelo conceptual - por utilizadores num cenário realista e que incluiu comparação com formas de acesso existentes. Além desta avaliação, a outro nível, mais relacionado com avaliação de tecnologias e não do modelo, foram efectuadas avaliações do desempenho do subsistema responsável pela extracção de informação. Os resultados da avaliação mostram que o modelo proposto foi percepcionado como mais eficaz e mais útil que as alternativas. Associado ao desempenho do protótipo a extrair informação dos documentos, comparável com o estado da arte, os resultados obtidos mostram a viabilidade e as vantagens, com a tecnologia actual, de utilizar processamento de linguagem natural e integração de informação semântica para melhorar acesso a conteúdos em linguagem natural e não estruturados. O modelo conceptual e o protótipo demonstrador pretendem contribuir para a existência futura de sistemas de pesquisa mais sofisticados e adequados ao governo electrónico. Para existir transparência na governação, cidadania activa, maior agilidade na interacção com a administração pública, entre outros, é necessário que cidadãos e empresas tenham acesso rápido e fácil a informação oficial, mesmo que ela tenha sido originalmente criada em linguagem natural

Essays on Growth Complementarity Between Agriculture and Industry in Developing Countries

This dissertation examines three aspects of the macroeconomic role of agriculture in the industrialization of developing countries. In the first essay, I utilize instrumental variable techniques to empirically identify the effect of growth in agriculture on growth in manufacturing. Using data for 62 countries and instrumental variable techniques, I find that higher land yields in agriculture raise growth in manufacturing in the short to medium run. Along with extensions of the basic empirical model, this finding suggests that land-saving technical change can stimulate demand for industrial goods, raise fiscal revenues, and provide foreign exchange earnings to finance capital accumulation. In the second essay, I examine the role of biased-technical change in agriculture in the formation of aggregate demand for industry. I use a two-sector growth model to show that, under conditions of low factor substitutability and hidden unemployment, land-saving innovations can raise rural employment, enlarge the domestic market for manufactures, and promote faster industrial accumulation --- in contrast to labor-saving innovations. I also develop saving-constrained and open economy extensions of the baseline model. The essay casts light on a recent strand of empirical studies --- including the first essay of this dissertation --- which have identified a positive impact of higher land yields on industrial growth. Finally, in the third essay I develop a political-economic explanation for the labor-displacing trend that existed across the larger and most dynamic agricultural establishments in Brazil during the 1950-1980 period. Using primary data and the secondary literature, I document this trend and argue that it resulted from the interaction between public policies to promote the use of modern inputs, on the one hand, and size and power inequality across landholdings, on the other hand. As a result, the pattern of technical change in agriculture aggravated the problem of underemployment that beset Brazil\u27s industrialization, preventing a broader distribution of its benefits

Assessing and responding to audit risk in a financial statement audit, revised edition as of October 1, 2009; audit and accounting guide

https://egrove.olemiss.edu/aicpa_guides/1746/thumbnail.jp

Essays on entrepreneurship and pricing

This dissertation studies questions about the interrelationship between the macroeconomic environment and entrepreneurship as well as questions on optimal pricing. It is comprised of three chapters which can be read independently. Chapters 1 and 2 are concerned with the effects of macroeconomic trends and fluctuations on entrepreneurship. In Chapter 1 I investigate the long run decline in firm creation rates in the US since the early 1980s. I document new empirical facts on the contemporaneous increase in average firm size and relate them to the decline in firm creation rates in a quantitative model. In the second Chapter which is co-authored with Konrad Stahl and Joacim Tag we empirically analyze the relationship between variation in entrepreneurial quality and variation in firm quality and relate both to business cycle fluctuations. In Chapter 3 I analyze a theoretical model of optimal monopoly pricing in which the monopolist is uncertain about the demand he faces which introduces new tradeoffs into the optimal pricing problem

Essays on tasks, technology, and trends in the labor market

This thesis contains three essays on the role of tasks and technology in explaining the trends in reallocation of employment across occupations and sectors, and inequalities in the labor market. The first two chapters focus on the task content of occupations with special emphasis on the effect of interpersonal interactions in the changing structure of employment in the labor market. Chapter 1 studies structural change of employment at the task level. Interactions with customers are a key friction against the implementation of potentially better production styles and technologies, since customers are hard to train and should be satisfied according to their tastes. Using a wide range of data sources on tasks, detailed occupation employment, labor productivity, and computer adoption, Chapter 1 develops a novel task measure, interpersonal-service task intensity, to study the growing importance of service activity in the US labor market in recent decades and explores its linkages with technical change. The chapter explains the empirical findings with a model of structural change at the task level which suggests two distinct roles for interpersonal-service intensity and task-routinizability. Concerned with the reallocation of employment jointly across occupations and sectors, Chapter 2 quantifies the impact of interpersonal-service task intensity and routinization on job polarization and structural change of sector employment. I estimate a task-biased technical change model which is capable to address occupation-specific and sector-specific technical change separately and show that substantial portion of occupational and sectoral employment reallocation between 1987 and 2014 in the US can be explained by the two task aspects. While both types of tasks are significant drivers of job polarization, interpersonal-service tasks stand out in explaining the growth of service sector employment. Using the framework I also suggest answers to several issues in the related literature. Chapter 3 switches the focus of study from the task content to skills while keeping the occupation-based perspective. The last chapter studies the importance of within-occupation heterogeneity of skills in understanding the rising labor market inequalities. I document that employment and wage growth of occupations tend to increase monotonically with various measures of skill intensity since 1980 in the US, in contrast to the existing interpretation of labor market polarization along occupational wages. I establish robustness of the documented fact, explore the sources of the seemingly contrasting finding and argue that labor market polarization cannot be interpreted as polarization of skills that are comparable across occupations. The chapter reconciles the documented facts in an extended version of the canonical skill-biased technical change model which incorporates many occupations and within-occupation heterogeneity of skill types

The consequences of financial regulation.

Given the importance of the financial services for capital accumulation, financial stability, and global financial intermediaries, the last decade has witnessed widespread calls for vigilant regulation of the sector, especially since 2007 to 2009 financial crisis. This has reinvigorated the debates on the economic benefits and costs of regulating the financial services. In this work, I examine the impact of financial regulation on the financial sector to better understand its influence on compliance costs, quality of financial reporting, and risk-taking, as well as the wider impact on the stock market liquidity and price informativeness. I also examine the impact of the UK’s decision to leave the European Union (BREXIT) on the UK stock market and industry. In the first paper, I review the empirical evidence on the literature on financial regulation published over the past thirty-five years with the aim: (1) to extend my understanding of its impact on the financial sector, (2) evaluate whether the regulation achieves the purpose it was designed, and (3) provide insights and suggestions for future research. I find several useful insights have been generated over the past two decades. Despite this progress, I find that most empirical studies were done in the United States, research on other regulatory context is under-researched. Further, most empirical research on costs of regulation exclude the financial sector, and we know that this sector is highly regulated. There is a need for more empirical research to provide insight on the regulatory cost burden to the financial sector. In the second paper, I examine how the Statutory Audit and Corporate Reporting Directives (SACORD) affect the compliance costs, risk-taking and quality of financial reporting of the EU banks. Using a natural experiment, I find that post SACORD, compliance costs of the EU banks increase by 11 to 26 percent. Further, there is a significant increase in risk-taking and a decline in the reporting quality. I conclude that as far as the EU banks are concerned, these regulations do not appear to have the desired effects of improving the reporting quality and constraining risk-taking. In the third paper, I investigate the impact of the MiFID on stock price informativeness and liquidity in the European Union (EU). Using data from 28 EU countries and the Difference in Differences approach, I find that post-MiFID the stock prices reflect greater firm-specific information and the market becomes more liquid. Consistent with the ‘Hysteresis Hypothesis’ the evidence shows that the impact of MiFID regarding price informativeness is greater for countries that have superior quality of regulation. The results are robust with respect to the choice of price informativeness and liquidity proxies as well as the control variables. Finally, in the fourth paper, I analyse the impact of UK referendum outcome (Brexit) on stock prices, along three key arguments made by proponents. I document that restricting EU labour movement is associated with a decline in market value by 9.64% to 10.35% over a 10-day event window. Further, sectors with a majority of their business operations outside the EU fared better than sectors that requires a lot of workforce from the EU. I find evidence that highly regulated sectors benefit more from expected deregulation of EU-derived laws except for the financial institutions. Additionally, internationally focused companies’ performed better than domestically focused firms. In sum, my evidence shows that the market expectations about labour restrictions, streamlining regulation and trade policies significantly affect firm values.PhD in Leadership and Managemen