acase@tulane.edu / The Socioeconomic Stratification System (SES) in Colombia is an official classification mechanism used by the government to determine eligibility for subsidies on a sliding scale based on conditions of the dwelling and access to infrastructure. This system classifies housing in up to six categories depending on the household’s features, surrounding area, and urban context. In this thesis, I analyze the social and epistemological implications of the SES in Colombia by looking at how the SES facilitates society to reimagine class identity affecting self-worth and social mobility. The two-main arguments are: 1) the SES categorization system has been transformed from a housing label to the identity of the individual, and 2) social dynamics in Colombia have been altered by the SES. Finally, this thesis should demonstrate the importance for research that not only focuses on the effectiveness of social programs, but also, on their social impact. / 1 / Ana María López

Yes / Despite much work on the frontier of Roman Britain, major questions concerned with society and settlement archaeology remain underinvestigated. Salient details of two major urban sites, Carlisle and Corbridge, both of which may shed further light on processes of settlement growth and decline, and which may ultimately contribute to a greater understanding of how the frontier worked, are summarized. At Carlisle, and probably also at Corbridge, settlement growth associated with forts was rapid and multi-tracked, but from the later 2nd century AD changes took place associated, perhaps, with enhanced status and a growing sense of community.

This study aimed to understand constructs related to classroom social dynamics in a sample (n = 1863) of rural middle school students. First, it used latent profile analysis to classify classrooms based on classroom norm salience. Next, the study used the Hierarchical Linear Model to study the influence of classroom norm salience on the social roles and reputations, social network centrality, bullying involvement, and school belonging of students with disabilities. There were four major findings. First, classrooms were classified into two distinct categories based on students’ social reputations, which were positively associated with peer-nominated popularity: High Aggression Norm Salience Classrooms and High Academic/Prosocial Norm Salience Classrooms. Second, there were significant differences by class type in two specific social characteristics: students with disabilities were more likely to get their way and be nominated as leaders in classrooms classified as High Aggression Norm Salience Classrooms. Third, there was no difference in either social network centrality or bullying involvement of students with disabilities by class type. Fourth, students with disabilities were more likely to feel school belonging in classrooms that were identified as High Academic/Prosocial Norm Salience Classrooms. The implications for practice and policy are discussed.

There is a dearth of literature on the effects of the implementation of the Skills Development Act (SDA) in South African governmental or Higher Education Institutions (HEIs). Although the available body of scholarship draws attention to problems that HEIs encounter with the implementation of the SDA, it does not elaborate on the underlying reasons for these problems. The aim of this critical interpretive study was, therefore, to gain an understanding of the rationale for and meaning of HEIs' employee staff development practices and that of the implementation of the SDA, as well as the match and mismatch between them. The intention of this study was to bring to the surface the underlying social dynamics that Skills Development Facilitators (SDFs) attach to the implementation of the SDA in HEIs. The epistemological intersection between interpretivism and critical theory was, therefore, chosen as the paradigmatic backdrop of this study. The use of Atlas.ti™ to analyse systematically the volume of unstructured data gathered from seven SDFs at HEIs not only facilitated the data analysis but also enhanced the validity of the study. Besides this, Professor Elsie (Liz) Greyling and Professor Nico Sauer intensively scrutinised and commented on my interpretation of the data, also contributing to the validity of this study. An analysis of the research data generated the following interrelated themes: • HEIs experience a total lack of support and guidance from the ETDP SETA. • The descriptions of terminology in the SDA and the explanations offered by government officials are often contradictory and confusing. • Informal development, one of HEIs' core employee learning methods, is difficult to capture. • HEIs' Workplace Skills Plans (WSP) and Annual Training Reports (ATR) submitted to the ETDP SETA are not a fair and accurate reflection of HEIs' staff development practices. • The development of systems to capture HEIs' employee ETD practices on the ETDP SETA's templates for the WSP and ATR is costly. • Time frames for the development of WSPs in HEIs differ from the time frame of the ETDP SETA. These were the main themes indicating why HEIs find it difficult to integrate the SDA in their staff development framework. The effect of these reasons why HEIs find it difficult to integrate the SDA in their staff development practices is that HEIs submit their WSPs and ATRs only to recoup in rebates (grants) the levies they pay. The government furthermore aims to take control of HEIs' employee ETD practices by enforcing the establishment of institutional structures to manage staff development mechanistically. Moreover, HEIs are compelled to prioritise investment in the education, training and development of designated employees, whereas the service delivery of quality education depends on the efficiency of all HEIs' staff members (by implication the development of all employees). In addition, HEIs are compelled to invest in the development of unemployed SA citizens, although the relationship between investment in ETD and economic prosperity is not proven. HEIs are, furthermore, compelled to follow a statutory policy framework that focuses on the manual skills required in the labour market, not on the cognitive, intellectual and largely scholarly skills that HEIs require to maintain and enhance quality education in South Africa. The result of the latter, viewed from a institutional perspective (macro-financial), is that HEIs not only have less funds for ETD practices than they had before the implementation of the SDA, but also that the implementation of the SDA could create negative social relations in HEIs themselves. These effects of the implementation of the SDA also seem to be perpetuated by the lack of interaction and debate between the ETDP SETA and HEIs. It is therefore argued in this study that the absence of officially structured dialogical activities between HEIs' representatives and ETDP SETA officials would perpetuate the dissonance between the reasons for and aims of the SDA and those of skills development in HEIs. / Thesis (PhD)--University of Pretoria, 2009. / Human Resource Management / unrestricted

Fat-tailed distributions, characterized by the relation P(x) ∝ x^{−α−1}, are an emergent statistical signature of many complex systems, and in particular of social activities. These fat-tailed distributions are the outcome of dynamical processes that, contrary to the shape of the distributions, is in most cases are unknown. Knowledge of these processes’ properties sheds light on how the events in these fat tails, i.e. extreme events, appear and if it is possible to anticipate them. In this Thesis, we study how to model the dynamics that lead to fat-tailed distributions and the possibility of an accurate prediction in this context. To approach these problems, we focus on the study of attention to items (such as videos, forum posts or papers) in the Internet, since human interactions through the online media leave digital traces that can be analysed quantitatively. We collected four sets of time series of online activity that show fat tails and we characterize them. Of the many features that items in the datasets have, we need to know which ones are the most relevant to describe the dynamics, in order to include them in a model; we select the features that show high predictability, i.e. the capacity of realizing an accurate prediction based on that information. To quantify predictability we propose to measure the quality of the optimal forecasting method for extreme events, and we construct this measure. Applying these methods to data, we find that more extreme events (i.e. higher value of activity) are systematically more predictable, indicating that the possibility of discriminate successful items is enhanced. The simplest model that describes the dynamics of activity is to relate linearly the increment of activity with the last value of activity recorded. This starting point is known as proportional effect, a celebrated and widely used class of growth models in complex systems, which leads to a distribution of activity that is fat-tailed. On the one hand, we show that this process can be described and generalized in the framework of Stochastic Differential Equations (SDE) with Normal noise; moreover, we formalize the methods to estimate the parameters of such SDE. On the other hand, we show that the fluctuations of activity resulting from these models are not compatible with the data. We propose a model with proportional effect and Lévy-distributed noise, that proves to be superior describing the fluctuations around the average of the data and predicting the possibility of an item to become an extreme event. However, it is possible to model the dynamics using more than just the last value of activity; we generalize the growth models used previously, and perform an analysis that indicates that the most relevant variable for a model is the last increment in activity. We propose a new model using only this variable and the fat-tailed noise, and we find that, in our data, this model is superior to the previous models, including the one we proposed. These results indicate that, even if present, the relevance of proportional effect as a generative mechanism for fat-tailed distributions is greatly reduced, since the dynamical equations of our models contain this feature in the noise. The implications of this new interpretation of growth models to the quantification of predictability are discussed along with applications to other complex systems.

No description available.

No description available.

The successful crowdsourcing model and gamification design of Stack Overflow (SO) Q&A platform have attracted many programmers to ask and answer technical questions, regardless of their level of expertise. Researchers have recently found evidence of security vulnerable code snippets being possibly copied from SO to production software. This inspired us to study how reliable is SO in providing secure coding suggestions. In this project, we automatically extracted answer posts related to Java security APIs from the entire SO site. Then based on the known misuses of these APIs, we manually labeled each extracted code snippets as secure or insecure. In total, we extracted 953 groups of code snippets in terms of their similarity detected by clone detection tools, which corresponds to 785 secure answer posts and 644 insecure answer posts. Compared with secure answers, counter-intuitively, insecure answers has higher view counts (36,508 vs. 18,713), higher score (14 vs. 5), more duplicates (3.8 vs. 3.0) on average. We also found that 34% of answers provided by the so-called trusted users who have administrative privileges are insecure. Our finding reveals that there are comparable numbers of secure and insecure answers. Users cannot rely on community feedback to differentiate secure answers from insecure answers either. Therefore, solutions need to be developed beyond the current mechanism of SO or on the utilization of SO in security-sensitive software development. / Master of Science / Stack Overflow (SO), the most popular question and answer platform for programmers today, has accumulated and continues accumulating tremendous question and answer posts since its launch a decade ago. Contributed by numerous users all over the world, these posts are a type of crowdsourced knowledge. In the past few years, they have been the main reference source for software developers. Studies have shown that code snippets in answer posts are copied into production software. This is a dangerous sign because the code snippets contributed by SO users are not guaranteed to be secure implementations of critical functions, such as transferring sensitive information on the internet. In this project, we conducted a comprehensive study on answer posts related to Java security APIs. By labeling code snippets as secure or insecure, contrasting their distributions over associated attributes such as post score and user reputation, we found that there are a significant number of insecure answers (644 insecure vs 785 secure in our study) on Stack Overflow. Our statistical analysis also revealed the infeasibility of differentiating between secure and insecure posts leveraging the current community feedback system (eg. voting) of Stack Overflow.

Traditional research into pro-environmental behaviour change has a tendency to be focussed on either the context in which practices are enacted or the cognitive processes that lead to particular behaviours. Research is often located within individual disciplines, with policy implications defined by (often) narrow interpretations of a problem. Despite increasing recognition of the ability of behaviour change to significantly contribute to the reduction in emissions required to meet UK targets, policy is so far failing to encourage ‘normative’ low carbon practices in many areas of life. Based on theories of social practice, this thesis attempts to redress the relationship between individuals and behaviour in order to discover how energy practices are developed, maintained and reconfigured. Specifically, it develops a phenomenological approach to energy consumption by exploring how energy practices are experienced by individuals on a daily basis, based on the premise that much human behaviour is driven by individuals’ perceptions of their actions. The study highlights the importance of the meanings and associations that individuals possess in relation to their energy practices and how these are implicated by their experiences, past and present. Furthermore, it contends that practices are influenced by social interactional dynamics and normative frameworks within the home, as well as by the form and frequency of social relations external to the home. With energy consumption so closely interlocked with the practices with which individuals engage in a daily basis, this thesis suggests that policy needs to be more in tune with the everyday experiences of energy consumers. It concludes by setting out a form of policy-making that has the potential to reduce everyday energy use by being sensitive to the experiences and well-being of individuals and society.

A existência de opiniões distintas em uma sociedade na qual indivíduos interagem constantemente atraiu o interesse de cientistas sociais e físicos estatísticos. Em 1997, Robert Axelrod propôs um modelo vetorial para o estudo da formação de domínios culturais diferentes em uma rede de agentes interagentes. Nesse modelo, os agentes são representados por um vetor de F componentes em que cada componente assume um dentre Q estados inteiros. O modelo apresenta uma transição de um estado monocultural (ordenado) para um estado multicultural (desordenado) que tem sido estudada na literatura através de parâmetros de ordem tais como o tamanho relativo do maior domínio cultural (S) e a fração de domínios culturais diferentes (g). Desde então, propriedades como robustez à introdução de ruídos, à variação de topologia e à introdução de campos local, global e externo foram investigadas. Nosso trabalho está organizado em três partes principais. Na primeira, apresentamos a proposta de novas medidas baseadas no conceito de atividade por agente para o estudo do modelo de Axelrod na rede quadrada. Mostramos que a variância da atividade do sistema (A) pode ser usada para indicar os pontos de transição e que sua distribuição de frequência pode indicar a ordem da transição. Na segunda, estimamos o diagrama de fases no plano (F,Q) e comparamos resultados obtidos em redes com condição de contorno aberta e fechada. Para isso, utilizamos as susceptibilidades dos parâmetros de ordem S e A para determinar os valores críticos Qc(F) para alguns valores de F. Na terceira, analisamos a formação de domínios culturais com a introdução de agentes persistentes para modelar efeitos de mídia interna. Nossos resultados revelam uma dependência de Qc com a probabilidade de ocupação p de agentes persistentes que nos permite obter o diagrama de fases no plano (p,Q). Interpretamos a linha crítica como resultado da competição de duas forças opostas (denominadas efeito de barreira e efeito de ligação) causadas por agentes não-persistentes que aderem aos persistentes. / The existence of different opinions in a society where individuals constantly interact has attracted the interest of social scientists and statistical physicists. In 1997, Robert Axelrod proposed a vectorial model to study the formation of cultural domains in a network of interacting agents. In this model, the agents are represented by a F components vector in which one from Q integer states is assigned to each component. The model presents a transition from a monocultural state (ordered) to a multicultural one (disordered) that has been studied by using order parameters such as the relative size of the biggest cultural domain (S) and the fraction of different domains (g). Since then, some properties as the robustness to the introduction of noise, to the variation of topology and to the introduction of local, global and external fields were studied. Our work is organized in three main parts. In the first part we present the proposal of new measurements based on the concept of activity per agent to study the Axelrod\'s model in a square lattice. We show the variance of system\'s activity (A) can be used to indicate the transition points and that the system\'s activity frequency distribution can be used to indicate the order of the transition. In the second part we estimate the phase diagram in the (F,Q) plane and compare the results obtained from simulations performed in lattices with open and closed boundary conditions. For this purpose, we use the susceptibility of order parameters S and A to determine the critical values Qc(F) for some values of F. In the third part we analyze the formation of cultural domains by introducing persistent agents to model effects of internal media. Our results reveal a dependence of Qc on the occupation probability p of persistent agents that allows us to obtain the phase diagram in the (p,Q) plane. We interpret the critical locus as a result of two opposite forces (called barrier effect and bonding effect) caused by non-persistent agents which adhere the persistent ones.