Switching mode DC/DC converters are critical building blocks in portable devices and hence their power efficiency, accuracy and cost are a major issue. The primary focus of this thesis is to address these critical issues.This thesis focuses on the different methods of feedback control loop which are employed in the switching mode DC/DC converters such as voltage mode control and current mode control. It also discusses about the structure of buck converter and tries to find an efficient solution for stepping-down the DC voltage level in ultra-low power applications. Based on this analysis, a 20 MHz voltage mode DC/DC buck converter with an on-chip compensated error amplifier in 65 nm CMOS process is designed and implemented.The power efficiency has been improved by sizing the power switches to have a low parasitic output and gate capacitances to reduce the capacitive and gate-drive losses. Also the error amplifier biasing current is chosen a small value (12.5 μA) to reduce the power dissipations in the control loop of the system. The maximum 84% power efficiency is achieved at 1.1 V to 500 mV conversion, above 81% efficiency can be achieved at load current from 0.5 mA to 1.26 mA. Due to wide bandwidth error amplifier and proper compensation network the fast transient response with settling time around 45 μs is achieved.

The present study examines typical features of internet language found in user-generated comments collected from commenting groups from four online magazines aimed at different readerships: (1) adult women (Working Mother and Mothering), (2) adult men (Esquire), (3) young women (Seventeen) and (4) young men (Gameinformer). Approximately 5,000 words from each commenting group were collected, creating a 21,087 word corpus which was analyzed with regard to typographic (emoticons, nonstandard typography of and, personal pronouns you and I) and orthographic features (abbreviations, acronyms) as well as syntactic and stylistic features resembling spoken language (contracted forms, ellipsis of subject and/or verb and commenting tone). The results show that adult men wrote the longest comments, followed by adult women, young men and young women in descending order. Furthermore, as for the typical features regarding typography and orthography, it was found that among the four commenting groups, adult men and adult women used them very sparsely, young men used them occasionally and young women used the features most frequently. The analysis of tone showed that adult men mostly used an aggressive or neutral tone, while adult women, young women and young men mostly used a friendly or neutral tone. Young women used an aggressive tone more often than adult women and young men. Moreover, regarding the syntactic and stylistic features, results revealed that the young men were the most frequent users of ellipsis of subject and/or verb, followed by adult women, young women and adult men. Contracted forms were used extensively in the potential places of contractions, regardless of commenting group. Since young men used the ellipsis of subject and/or verb most frequently of all commenting groups and also used the contracted forms in all potential places of contractions, the conclusion is that the young men used a style that is closer to spoken English than the three other commenting groups. / Den här studien undersöker språkdrag som är typiska för språk på internet. Det material som har undersöks har hämtats från användarkommentarer i nättidningar som är riktade till fyra olika läsargrupper: (1) kvinnor (Working Mother, Mothering), (2) män (Esquire), (3) unga kvinnor (Seventeen) och (4) unga män (Gameinformer). Cirka 5 000 ord hämtades från kommentarsfälten för varje tidning, vilket resulterade i en korpus som omfattade 21 087 ord totalt. Korpusen analyserades med hänsyn till typografiska språkdrag (smileys, ickestandardiserad stavning av personliga pronomen I och you samt and) och ortografiska språkdrag (förkortningar, akronymer) samt syntaktiska och stilistiska språkdrag som påminner om talspråk (sammandragningar, ellips av subjekt och/eller predikatsverb, tonläge). Resultaten visade att män skrev de längsta kommentarerna, följda av kvinnor, unga män och unga kvinnor i fallande ordning. Vad gäller typiska typografiska och ortografiska språkdrag visar resultatet att de återfanns mycket sparsamt i kvinnornas och männens data, att de återfanns då och då i de unga männens data och att de unga kvinnorna var de som använde dessa språkdrag mest frekvent. Analys av tonläge i användarkommentarerna visade att män oftast använde en aggressiv eller neutral ton, medan kvinnor, unga kvinnor och unga män oftast använde en vänskaplig eller neutral ton. Unga kvinnor använde en aggressiv ton oftare än kvinnor och unga män. Utöver detta visade resultatet att ellips av subjekt och/eller predikatsverb var mest frekvent i de unga männens användarkommentarer, följt av kvinnornas, de unga kvinnornas och männens. Sammandragna former användes näst intill undantagslöst i hela korpusen. Eftersom pojkarna uppvisade mest frekvent användning av ellips av subjekt och/eller predikatsverb samt använde sammandragna former i full utsträckning, kan slutsatsen dras att de unga männens syntax är mer påverkad av engelskt talspråk än syntaxen hos de tre andra kommenterande grupperna.

In the present work, the processes of steady combustion and autoignition of hydrogen are investigated using the Conditional Moment Closure (CMC) model with a Reynolds Averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) code. A study of the effects on the flowfield of changing turbulence model constants, specifically the turbulent Schmidt number, Sct, and C epsilon 1 of the k − epsilon model, are investigated. The effects of two different mixing models are explored: the AMC model, which is commonly used in CMC implementations, and a model based on the assumption of inhomogeneous turbulence. The background equations required for implementation of the CMC model are presented, and all relevant closures are discussed. The numerical implementation of the CMC model, in addition to other techniques aimed at reducing computational expense of the CMC calculations, are provided. The CMC equation is discretised using finite volume (FV) method. The CFD and CMC calculations are fully coupled, allowing for simulations of steady flames or flame development after the occurrence of autoignition. Through testing of a steady jet flame, it is observed that the flowfield calculations follow typical k − epsilon model trends, with an overprediction of spreading and an underprediction of penetration. The CMC calculations are observed to perform well, providing good agreement with experimental measurements. Autoignition simulations are conducted for 3 different cases of turbulence constants and 7 different coflow temperatures to determine the final effect on the steady flowfield. In comparison to the standard constants, reduction of Sct results in a reduction of the centreline mixing intensity within the flowfield and a corresponding reduction of ignition length, while reducing C 1 results in an increase of centreline mixing intensity and an increase in the ignition length. All scenarios tested result in an underprediction of ignition length in comparison to experimental results; however, good agreement with the experimental trends is achieved. At low coflow temperatures, the effects of mixing intensity within the flowfield are seen to have the largest influence on ignition length, while at high coflow temperatures, the chemical source term in the CMC equation increases in magnitude, resulting in very little difference between predictions for different sets of turbulence constants. The inhomogeneous mixing model is compared using the standard turbulence constants. A reduction of ignition lengths in comparison to the AMC model is observed. In steady state simulation of the autoigniting flow, the inhomogeneous model is observed to predict both lifted flames and fully anchored flames, depending on coflow temperature.

Primary and secondary school students (Setzer, Lewis, and Greene, 2005), college students (I. E. Allen and Seaman, 2003, 2004), and corporate employees (Galvin, 2002) are all engaging more and more in some form of online or blended online/face-to-face education. Given the large number of pedagogical and design choices that we must make, however, where do we begin when designing new environments? I argue that its important for us to consider how technological design choices interact with pedagogical choices and cognitive states to affect learning behaviors. To illustrate this, I examine the impact of synchronous chat media on educational discussions. Specifically, I ask two questions: (1) Since research has often reported that chat environments promote conversational equity (e.g., Warschauer, 1997), which features of synchronous text-based chat seem to help create conversational equity? and (2) how does this change impact the content of small group discussions? Using ethnographic-style observations and quasi-experimental studies, I show how changing conversational media influences (or doesnt) the resulting discussion among students. I present three results: * Certain properties of the chat medium seem to discourage conversational dominance by any one individual through (a) denying that individual mechanisms to control the conversational floor and (b) reducing the inhibition felt by shy or otherwise disempowered students. * The choice of medium does not seem to affect the quality of discussion content nearly as much as other variables. * Efficiency is diminished in chatrooms; achieving quality discussions online requires significantly more time because (a) typing is slower than speaking and (b) students are able to do other, parallel activities while engaging in a chat discussion. In the conclusion, I examine the broader implications of these findings for the design of conversational environments, whether for educational or business use.

As the growing of social media and user-generated content phenomena, SNSs (Social Networking Sites) become a critical platform for people to join the virtual community to communicate and interact with each other. In addition to the positive virtual groups, there are also negative-bias counterparts - Anti-fans groups. The main purpose of Anti-fans groups is to oppose and attack particular celebrities they hate. The influence of such groups on the Internet cannot be underestimated. Based on the Use and Gratification Theory, the study proposes both environmental and psychological factors have the effect on motives, behaviors and attitudes. The research hypothesizes that both Computer-mediated Communication characteristics (CMC) and Big Five Personality traits do influence the motives, behaviors and attitudes of participating in Anti-fans groups. This research adopted Internet surveys and took samples from members from Anti-fans groups on Facebook. Results showed that high levels of Disinhibition and Self-disclosure of CMC characteristics and significantly predicted the motives, behaviors and attitudes of participating in Anti-fans groups, and so do Extraversion and Neuroticism of Big Five Personality traits. Furthermore, individuals with different motivations have diversity of behaviors and gratifications of participating in Anti-fans group

Stigmas associated with depression and schizophrenia have been found to negatively impact the communication those with mental illness have with others in face-to-face interactions (e.g., Lysaker, Roe, & Yanos, 2007; Nicholson & Sacco, 1999). This study attempted to specifically examine how stigma affects cognitions, emotions, and behaviors of interactants without a mental illness toward those with a mental illness in online interactions. In this experimental study, 412 participants interacted with a hypothetical target on Facebook, who was believed to have depression, schizophrenia, or a cavity (i.e., the control group). They were asked to read a profile of the target on Facebook, respond to a message from the target, and complete measurements assessing perceived positive and negative face threats in the target's message, perceived facial expressions of the target, induced affect, predicted outcome value, and rejecting attitudes towards the target. Results revealed that the target labeled as schizophrenic was rejected more and perceived to have lower outcome value than the target without a mental illness or labeled as depressive. However, there were no significant differences in any outcomes between the depression and control groups. The mixed results were discussed in relation to methodological limitations and possible modifications of previous theoretical arguments. Theoretical and practical contributions were considered and suggestions for future research were offered. / text

The purpose of this study was to investigate the performances on speaking assessments in a first semester Spanish course to determine if there are differences among four sections based on required speaking tasks and mode of class delivery. Two of the classes were conducted online in a distance education delivery mode and two of the classes were conducted in the classroom. One section of delivery mode was required to fulfill speaking tasks throughout the semester while the alternate sections were offered the same speaking tasks as optional activities. Furthermore, the study investigated testing items repeated prompts versus new prompts to determine if there were differences in performance. Finally, the study investigated student performance confidence and beliefs about course materials. The data were collected through quantitative methods (oral rubric scores) and qualitative methods (open-ended questions). A total of 64 students participated in the study. Eight students completed the distance education course with optional speaking tasks. Thirteen students completed the distance education course with required speaking. Eighteen students completed the classroom course with optional speaking, and 24 students completed the classroom course with required speaking. In general, all classes made improvement between the first assessment and the second assessment. However, the mean performance scores for three of the four speaking prompts did not show significant difference among the four classes. In addition, there were no significant differences in mean scores of performances at the introduction of the two new speaking tasks on the final assessment. Only with one speaking repeated measure was there a significant difference. The significant difference was between the classroom with required speaking section and the distance education with optional speaking section. With an analysis of the Target Language Use, it was determined that the differences were due to lexical complexity and morphological complexity. In general, the self-report of confidence levels on the final oral assessment showed no significant differences among the four classes. There was a significant drop in confidence on one of the two new assessment prompts for all classes. Student comments indicated that there were frustrations with cognitive overload and dealing with ambiguity. / text

Recent progress in the discipline of computer applications such as the advent of web-based communication, afforded by the Web 2.0, has paved the way for novel applications in language learning, namely, social networking. Social networking has challenged the area of Computer Mediated Communication (CMC) to expand its research palette in order to account for the way individuals engage in processes of learning and socialization, the way they interact, and the way they construct and perform their identities. With this in mind, it is necessary to examine the new material conditions, social arrangements, and the communicational landscape of Social Networking Sites (SNS). This study focuses on SNSs for language learning (SNSLL) and examines the particular case of Busuu. Drawing on theoretical tenets of sociocultural and ecological approaches combined with multimodal social semiotics, this research aims to analyze the views of language and learning that are enacted through the semiotic design of Busuu. It also purports to examine the types of identities wherein users are positioned through the compositional elements of this participatory online environment. The research design is informed by the principles of a qualitative case study and autoethnographic research. The data collected for this study consist of documentary information obtained from Busuu and the autoethnographic accounts of the researcher, who participated as a member of the Busuu community for 10 weeks. Results indicate that overall Busuu is an ecological system composed of sub-systems of nested views about language, learning, and users in which multiple timescales, spatiotemporal, and discursive resonances of various theories work in synergy. Thus, the semiotic spaces of Busuu combine structural, interactional and ecological views of language. Similarly, Busuu crystalizes views of learning that echo behaviorist, cognitivist, and constructivist theories. The website enacts different identities, positioning users as learners and teachers/tutors who are members of an imagined community. The study draws implications about the need for theoretical coherence and pedagogical alignment among the different components of the language curriculum (e.g. language and learning views, instructional activities) of Social Networking Sites for Language Learning.

Ces travaux portent sur le développement d'un matériau virtuel pour la simulation et l'optimisation des matériaux à microstructure hétérogène, en particulier des composites à matrice céramique de nouvelle génération. Pour ce faire une modélisation du fil est mise en place, au travers d'une démarche intégrée qui prend en compte la complexité de la microstructure et de sa variabilité issues du procédé de fabrication. La démarche proposée repose sur deux étapes : i) la construction d'une morphologie synthétique du fil, basée sur l'étude de micrographies et ii) une méthode de simulation multiéchelle inspirée de la méthode des éléments finis généralisée. L'originalité de cette dernière provient de l'utilisation de motifs, sorte de situations physiques ou topologiques élémentaires, pour décrire à la fois la microstructure et la cinématique locale. La démarche est validée et appliquée à diverses sections de fil synthétiques 2D, pour lesquelles le choix des motifs est discuté. L'extension au traitement de tronçon 3D du fil, ainsi qu'à la simulation de la fissuration à l'aide d'une méthode discrète est discutée et des premiers éléments de réponse sont apportés.

La diffusione di Internet e delle Nuove Tecnologie nella vita quotidiana ha offerto la possibilità agli utenti di costruire liberamente diversi profili, anche protetti dall’anonimato. Molti autori si sono interessati del rapporto tra immagine online e Identità e il dibattito ha spostato il focus da un concetto monolitico di Identità all’adozione di una prospettiva dialogica. La domanda di ricerca nasce dall’esigenza di chiarire come si prenda forma online e quanto queste parziali presentazioni si discostino dalle immagini create durante le interazioni faccia a faccia. La ricerca si basa su una proposta teorica focalizzata sui concetti di Soggettività (parziale immagine di sé adattata alle condizioni contestuali) e Intersoggettività (dimensione polilogica entro la quale gli interlocutori negoziano le proprie immagini). Dopo aver costruito un sistema di categorie con cui analizzare la comunicazione via chatline (primo studio), il secondo e il terzo studio, invece, sono incentrati sulla variabilità, sull’adattabilità e sulla natura connettiva della Soggettività. I risultati mostrano che la Soggettività è in grado di adattarsi alle condizioni contestuali facendo emergere un’immagine parziale, ma specifica che è frutto dell’interazione con l’interlocutore. Adattabilità e parzialità non sono necessariamente segni di instabilità, ma costituiscono un strumento con cui evitare un rapporto rigido con la realtà. / The increased use of Internet and New Technologies gives the possibility to users to create many real or anonymous, images/profiles. Scholars have been studying the correlation between Identity and the online profiles, and are shifting from the concept of Identity in to a dialogic perspective. The aim of this study is to understand how users present their selves in online environments and if these partial images are so different compared to face to face interactions’ ones. This work is based on a new theoretical proposal based on two concepts: Subjetivity (partial presentation of the Self adapted to external conditions) and Intersubjectivity (dialogical/polilogical dimension in which interlocutors negotiate their subjectivities). A codebook for the analysis of communication via chat line was created in the first study. The second and the third studies are focused on the adapting and connectivistic nature of Subjectivity; results show how users are able to present strategically their selves thanks to negotiation with interlocutors. Adaptability is not necessary a sign of instability, it is a just tool to improve a good relations with ever changing reality.