1731 research outputs found
Sort by
Wildlife Road Crossing: innovative Solution for preventing Vehicle Collision based on pervasive WSN monitoring System
No full textThe study, design and development of a monitoring system for wildlife road crossing problem is addressed in this thesis. Collisions between fauna and vehicles is a relevant issue in several mountain and rural regions and a valuable low-cost solution has not yet been identified. In particular, the proposed system is composed by a network of sensors installed along road margins, in order to detect wildlife events, (e.g., approaching, leaving or crossing the road), thus to promptly warn the incoming drivers. The sensor nodes communicate wirelessly among the network thus collecting the sensed information in a control unit for data storage, processing and statistics. The detection process is performed by the wireless nodes, which are equipped with low-cost Doppler radars for real-time identification of wildlife movements. In detail, different technologies valuable for solving the problem and related off-the-shelf solutions have been investigated and properly tested in order to validate their actual performance considering the specific problem scenario. A final classification based on specific parameters has allowed identifying the Doppler radar system as the better low-cost technology for contributing to the problem objective. The performance of the proposed system has also been investigated in a real scenario, which has been identified to be the actual pilot site for the monitoring system. This confirms the system capability of movements detection in the road proximity, thus defining a security area along it, where all occurring events may be identified
From states to objects and events through stratification: A formal account and an application to data analytics
No full textIn this thesis, we are mainly interested in representing and stratifying objects, states, and events. From an epistemological or perceptual perspective, states may be seen as "time stamped data" or "basic observations". Perception and cognition organize sensory outputs by grouping them in units that allow us to interact with the world in a quick and fruitful way. Similarly, states can be organized by synchronically grouping them into complex configurations of the world, or diachronically grouping them into events. We are specially interested in the logical forms of existential dependencies between states, objects and events. In the view of some philosophers, the world is stratified in levels by means of existential dependencies. This view is also present in theories of granularity, where (i) an abstraction mechanism allows for the simplification of fine-grained (lower level) entities into coarser (higher level) entities, stratifying entities in levels of abstraction; or (ii) data resolution is considered a criterion for stratifying data in levels of granularity, reflecting a more epistemological perspective on levels.
We present here a framework for representing and stratifying objects, states, and events in levels. We show that our theory supports different notions of level, and suggest applications to data analytics
Los caminos ecfrásticos de la palabra al borde de la visión: Valente, Durero y el «ovillo negro» de Interior con figuras
No full textEste trabajo analiza el territorio ecfrástico de la primera sección del poemario “Interior con figuras” de José Ángel Valente y la necesidad de su palabra de conquistar, sobre todo a través de un diálogo visceral con la pintura y el arte, un espacio interior de autoconocimiento cada vez más profundo. En particular, examina las imágenes y la simbología del oscuro poema “Una antigua representación” dedicado a la famosa obra “El caballero, la muerte y el diablo” de Durero. La larga historia generada por este grabado empieza en el siglo XVI y se transforma con el pasar del tiempo, de las distintas lecturas, de las reescrituras literarias y de las ideologías hasta alcanzar sus interpretaciones más extremas en los eslóganes propagandísticos del Tercer Reich: ¿por qué encuentra su lugar también en la poesía de Valente y bajo qué perspectiva es insertada? ¿Remite el poema a alguna tradición o a otras versiones literarias precedentes? ¿Por qué sus imágenes parecen imprescindibles para el descenso del poeta en el interior de su palabra? Como demuestran las fechas de composición de los poemas de “Interior con figuras”, para llegar a concebir “Territorio”, poema programático del entero poemario, Valente necesitó primero contemplar los objetos-talismanes de las pinturas de Luis Fernández, la material memoria de Antoni Tàpies, los sueños de Odilon Redon, el enigma de la mirada del ángel de la “Melancolía I” y los símbolos de esa “antigua representación” que encontró rescatada eternamente por un grabado de Durero, “El caballero, la muerte y el diablo”. Sólo entonces se abrió la visión consciente del territorio interior de su palabra: otredad, figuras solas y materia fracturada
Algorithms and Performance Analysis for Synchrophasor and Grid State Estimation
No full textThe electrical quantities of future power networks are expected to exhibit strong fluctuations caused by dynamic bidirectional energy flows transferred from/to a multitude of "prosumers”. Such variations have to be accurately measured in real-time either for efficient power distribution or for safety and protection purposes. This task can be accomplished by the Phasor Measurement Units (PMUs), which measure the phasor of voltage or current waveforms synchronized to the Coordinated Universal Time (UTC). Accuracy of synchrophasor measurements is one of the many open challenges that need to be addressed in order to guarantee smart grid reliability and availability. Synchrophasor measurement has gained an undisputed relevance in the research community working on power delivery issues for various reasons. Among them, state estimation (SE) of both transmission and distribution networks is one of the most important. Within this general context, this dissertation covers two complementary topics. In the first part, starting from the concept of synchrophasor and from the definition of the parameters to evaluate PMU performances, useful guidelines to design a filter-based synchrophasor estimator are provided. Afterwards, an extensive performance comparison of some state-of-the-art synchrophasor estimation algorithms is reported in most of the static and dynamic conditions described in the IEEE Standards C37.118.1-2011. Also, a novel technique able to address both static and dynamic disturbances is presented and analyzed in depth. In this respect, special attention is devoted to phasor angle estimation accuracy, which is particularly important for active distribution networks.
The second part of the dissertation is focused on the role and the impact of PMUs for grid state estimation.
After recalling the state estimation problem and the traditional Weighted Least Square (WLS) technique to solve it, a general uncertainty sensitivity analysis to different types of measurements is introduced and justified both theoretically and through simulations. Afterwards, the effect of a growing number of PMUs on WLS-based state estimation uncertainty is evaluated as a function of instrumental accuracy and line parameters tolerance.
Finally, a Bayesian linear state estimator (BLSE) based on a linear approximation of power flow equations for distribution networks is presented. The main advantage of BLSE is that in most cases it is so accurate as the WLS technique, but it is computationally lighter, faster
and more stable from the numerical point of view
Socially aware motion planning of assistive robots in crowded environments
No full textPeople with impaired physical or mental ability often find it challenging to negotiate crowded or unfamiliar environments, leading to a vicious cycle of deteriorating mobility and sociability. In particular, crowded environments pose a challenge to the comfort and safety of those people. To address this issue we present a novel two-level motion planning framework to be embedded efficiently in portable devices. At the top level, the long term planner deals with crowded areas, permanent or temporary anomalies in the environment (e.g., road blocks, wet floors), and hard and soft constraints (e.g., "keep a toilet within reach of 10 meters during the journey", "always avoid stairs"). A priority tailored on the user's needs can also be assigned to the constraints. At the bottom level, the short term planner anticipates undesirable circumstances in real time, by verifying simulation traces of local crowd dynamics against temporal logical formulae. The model takes into account the objectives of the user, preexisting knowledge of the environment and real time sensor data. The algorithm is thus able to suggest a course of action to achieve the user’s changing goals, while minimising the probability of problems for the user and other people in the environment.
An accurate model of human behaviour is crucial when planning motion of a robotic platform in human environments. The Social Force Model (SFM) is such a model, having parameters that control both deterministic and stochastic elements. The short term planner embeds the SFM in a control loop that determines higher level objectives and reacts to environmental changes. Low level predictive modelling is provided by the SFM fed by sensors; high level logic is provided by statistical model checking. To parametrise and improve the short term planner, we have conducted experiments to consider typical human interactions in crowded environments. We have identified a number of behavioural patterns which may be explicitly incorporated in the SFM to enhance its predictive power. To validate our hierarchical motion planner we have run simulations and experiments with elderly people within the context of the DALi European project. The performance of our implementation demonstrates that our technology can be successfully embedded in a portable device or robot
Thinking Security: A Reflectivist Approach to Franceâs Security Policy-Making in sub-Saharan Africa
No full textRecent years have witnessed increased French military activism in Africa. Despite efforts to normalise its post-colonial relationship and considerable downsizing of its permanent military presence, France remains a sought-after actor in solving African security problems. Notwithstanding French decision-makersâ repeated promises that the gendarme of Africa belongs to the past, French troops have participated in nine military operations since the turn of the millennium. Against all expectations, the Hollande administration has stood out for being particularly interventionist, concerting a military intervention in Mali and deploying a peacekeeping force to the Central African Republic within two years of assuming office. The ambiguity between an interventionist policy and a disengaged discourse suggests that French military interventionism in sub-Saharan Africa no longer follows the same automaticity as in the past. The two interventions in Mali and the CAR testify to the intense ideational struggles between different belief systems that had shaped French actorsâ minds and thus influenced decision-making processes and policy outcomes.
Economic interests and neo-colonial continuity have been traditionally identified as the root causes of French interventionism in francophone Africa. For the past two decades the literature on French-African relations has been dominated by the so-called continuity vs. change debate, which scrutinises the presence of colonial / neo-colonial practices in the post-1990 French foreign policy. While ideational approaches to Franceâs African policy are not rare, few studies have engaged with the decision-making processes that produce French military interventions. Most studies focus on policy outcomes, which are rooted in static conceptualisations of ideas that are aggregated at the level of the state. Starting from these observations, the present study argues that the mere analysis of policy outcomes tells us little about the actual motivations that drive French foreign and security policy in Africa.
Instead of analysing French interventionism by relying on a predefined set of explanatory variables that are juxtaposed with a series of observable outcomes in order to falsify predefined hypotheses, this thesis explains French interventionism by drawing on actorsâ subjective perceptions and motivations. The study uses the actorsâ own utterances to explain why French decision-makers are ready to accept the considerable risks and costs involved in guaranteeing or re-establishing the security of African countries. Adopting an actor-centred constructivist ontology, this study not only identifies ideas as core explanatory variables but also traces their emergence and subsequent development throughout decision-making processes. This approach goes beyond the dichotomous view that reduces French motivations to material interests or post-colonial ambitions.
Relying on discursive material such as official statements, verbatim reports of press conferences and parliamentary hearings, policy reports, and thirty-two high-level interviews with French decision-makers, the present study narrates military intervention in Mali and the CAR from the perspective of French foreign policy elites under the Hollande Presidency. This recent and largely unexplored empirical material provides new insights into Franceâs foreign and defence policy. The study also demonstrates why and how the âAfrica factorâ still matters in Franceâs foreign policy considerations. The importance of Africa in Franceâs security policy has less to do with neo-colonial ambitions per se, than with the understanding French policy-makers have of themselves and their country. More generally, the findings show how comprehensive explanations of foreign policy can be produced by considering actorsâ subjective perceptions. In so doing, the study not only explains Franceâs current policies in sub-Saharan Africa, but also offers insights into foreign policy decision-making processes in general, and thereby provides further evidence about how ideational factors influence the making of world politics.
Keywords: France, Africa, Mali, CAR, foreign policy analysis, international security, decision-making, political psychology, constructivis
Social Capital and the Urban Informal Economy:The Case of Street Vendors in Addis Ababa, Ethiopia
No full textMicro-enterprise development has become one of the most important approaches to reduce poverty in the LDCs. Like other LDCs, in Ethiopia micro-enterprise development forms the major component in the promotion of broad based growth and improvement of the well-being of the poor by providing income generating opportunities. Accordingly, formalizing informal sector activities has become one of the priorities of micro-enterprise programs. The main aspect of micro-enterprise programs is the use of social capital as a substitute for collateral in providing credit and forming enterprise groups. Despite the significance of social capital in micro-enterprise programs in particular and the informal economy in general, its nature and potential contributions remain under-investigated in Ethiopia. The purpose of this study is, therefore, to examine the configuration of social capital among the poor street vendors in Addis Ababa. The study has employed the network approach to social capital. Data were collected from 154 street vendors living in Addis Ababa. Multi-stage sampling procedures involving purposive and systematic random-walk techniques were used to draw samples. The study applies a mixed-methods research design. Accordingly, quantitative and qualitative data were collected through name and position generator surveys and in-depth interviews. While the quantitative data were analyzed through social network analysis procedures and statistical techniques, the data from interviews were transcribed, classified, and presented in a narrative form. Two-sample T-test, one-way-ANOVA, and OLS and Instrumental Variable regression models were used as statistical tools for the study. The results of the study reveal that homophily in religion and ethnic lines forms the strongest divide among street vendors’ personal networks followed by sex and marital status homophily. However, street vendors exhibit heterophilous networks regarding income, age, and occupation. Street vendors demonstrate dense, less effective, less efficient, and highly constrained network structures. They also exhibit greater proportion of strong ties in their personal networks. Street vendors have most of their relationships with people of lower occupational prestige. In addition, they have low access to high prestige positions, low resource heterogeneity, and low social capital volume.
Comparisons of networks between gender and among ethnic groups show the presence of significant differences. Women’s network exhibits larger percentage of strong ties and more ethnic and religious homogeneity than men. Also, women exhibit small network size, less effective, and highly constrained networks. Network characteristics by ethnic group shows that the Gurages exhibit high proportions of strong ties and high levels of ethnic homophily but embedded in networks of diverse education, occupation, and income compared to the Amharas and the Oromos. Conversely, the Amharas have diverse ethnic and religious contacts and demonstrate relatively high proportions of weak ties than others. Structurally, while the Gurages exhibit large network size with dense and less effective networks; the Amharas display small network size and less dense networks. The overall heterogeneity index shows that the Gurages exhibit more heterogeneous networks than the Amharas and the Oromos. By examining network dynamics, the study also reveals significant changes in the number and nature of ties kept, ties lost, and new ties created over the phases of enterprise development. There have also been changes in network composition and structure over the three entrepreneurial phases. The study further investigated the effect of social capital in enterprise performance. Four separate regression models were fitted to predict the effect of relational, structural, and embedded resources dimensions of social capital on enterprise performance. After controlling the potential endogeneity problem of social capital, the estimation results revealed that the resources embedded in networks contribute positively to enterprise performance compared to the strength of ties and the structural constraint. Human capital measures, on the other hand, do not significantly predict enterprise performance.
The implications of the outcomes of the study is that in providing credit and establishing enterprise groups, micro-enterprise programs should evaluate the trade-off between strong versus weak ties and homogeneity versus heterogeneity of networks. While religion, ethnicity, gender, and marital status homophily as well as strong family and friendship ties are worthwhile for credit delivery and forming enterprise groups, network heterogeneity is central for enterprise success. Overall, it is unlikely that social problems can be resolved without analyzing the social ties of individuals in particular and the community in general. Thus, it is imperative to conduct further studies in a broader scope to advance the significance of social capital for poor targeted development interventions in Ethiopia
Quality Teaching in Large University Classes: Designing Online Collaboration among Learners for Deep Understanding
No full textThis study aimed to explore the impact of eLearning on quality teaching in higher education and to implement Computer-Supported Collaborative Learning (CSCL) that targeted the quality challenges in practice. It was a mixed method research composing of three stages. It initially focused on university teachers’ perception of quality teaching, problems, and strategies in practice to understand the actual usage of eLearning by practitioners. Seventeen university teachers participated in the inquiry of stage 1. It found the common perception of quality teaching was students’ deep understanding of the learning subject. Besides, large class teaching was the most common problem faced by teachers who already achieved quality teaching in small classes, which became the research focus in the inquiry of stage 2. CSCL was selected as a potential eLearning strategy that targeted quality challenges in large class teaching due to its theoretical benefits. the inquiry of stage 2 aimed to explore the impact of CSCL on quality teaching in large classes. Considering the institutional influence on teaching approaches, it defined the case in the university level. Two universities composed of ten teachers were investigated. It found the majority of participants perceived a limited quality in large class teaching, and this limitation was due to two issues: insufficient teacher-student interaction, and the difficulty in checking students’ understanding in the learning process. Besides, CSCL was not widely adopted in practice, and adopted strategies did not target those two issues mentioned above. The inquiry of stage 3 designed and implemented CSCL activities in an authentic large university class with the aim to explore its impact. It indicated CSCL helped to improve teaching quality in large classes – students’ deep understanding - by enhancing interaction and feedback in the learning process. In sum, this three-stage study revealed the practical challenges of quality teaching in higher education, then designed and implemented eLearning activities to tackle them
Distributed Contact and Identity Management
No full textContact management is a twofold problem involving a local and global level where the separation between them is rather fuzzy. Locally, users need to deal with contact management, which refers to a local need to store, organize, maintain up to date, and find information that will allow them contacting or reaching other people, organizations, etc. Globally, users deal with identity management that refers to peers having multiple identities (i.e., profiles) and the need of staying in control of them. In other words, they should be able to manage what information is shared and with whom. We believe many existing applications try to deal with this problem looking only at the data level and without analyzing the underlying complexity. Our approach focus on the complex social relations and interactions between users, identifying three main subproblem: (i) management of identity, (ii) search, and (iii) privacy.
The solution we propose concentrates on the models that are needed to address these problems. In particular, we propose a Distributed Contact Management System (DCM System) that:
Models and represents the knowledge of peers about physical or abstract objects through the notion of entities that can be of different types (e.g., locations, people, events, facilities, organizations, etc.) and are described by a set of attributes;
By representing contacts as entities, allows peers to locally organize their contacts taking into consideration the semantics of the contact’s characteristics;
By describing peers as entities allows them to manage their different identities in the network, by sharing different views of themselves (showing possibly different in- formation) with different people.
The contributions of this thesis are, (i) the definition of a reference architecture that allows dealing with the diversity in relation with the partial view that peers have of the world, (ii) an approach to search entities based on identifiers, (iii) an approach to search entities based on descriptions, and (iv) the definition of the DCM system that instantiates the previously mentioned approaches and architecture to address concrete usage scenarios
Au-delà du formalisme. La critique des écrivains en France et en Italie pendant la seconde moitié du XXe siècle
Get PDFMy dissertation covers the field of what Albert Thibaudet called “the critique of artists” in order to show that, throughout the second half of the twentieth century, this form of criticism has given readers a different perspective on literature in comparison to that of the formalists and the neo-avant-garde. In the first part of my study, I examine the evolution of formalist criticism in the twentieth century, considering the linguistic turn of the 1960s as the natural outcome of a cultural revolution which took place at the end of the nineteenth century. By conducting a comparative study between France and Italy, I attempt to outline a transnational model which shows that the two formalist critiques share the same understanding of the literature postulated by the neo-avant-garde. The second part of my thesis is devoted to the study of one of the main tendencies in the critique of the writers since the Second World War, a tendency that called into question a purely intrinsic study of the work of art. Here, I propose a comparative study of the literary critique of Georges Perec, Michel Tournier, Philippe Muray, Tommaso Landolfi, Pier Paolo Pasolini and Pier Vittorio Tondelli, in order to underline that their critical practice has not limited itself to a personal declaration of their poetic views, but it has truly opened up an alternative approach to formalist theoretical positions. They refused to speak of literature as a secluded world, and by doing so they anticipated one of the most important features of the literature of the end of the twentieth century, both in France and in Italy