916 resultados para Corrective Switching


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[EN] Since Long's Interaction Hypothesis (Long, 1983) multiple studies have suggested the need of oral interaction for successful second language learning. Within this perspective, a great deal of research has been carried out to investigate the role of corrective feedback in the process of acquiring a second language, but there are still varied open debates about this issue. This comparative study seeks to contribute to the existing literature on corrective feedback in oral interaction by exploring teachers' corrective techniques and students' response to these corrections. Two learning contexts were observed and compared: a traditional English as a foreign language (EFL) classroom and a Content and Language Integrated Learning (CLIL) classroom .The main aim was to see whether our data conform to the Counterbalance Hypothesis proposed by Lyster and Mori (2006). Although results did not show significant differences between the two contexts, a qualitative analysis of the data shed some light on the differences between these two language teaching settings. The findings point to the need for further research on error correction in EFL and CLIL contexts in order to overcome the limitations of the present study.

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Most second language researchers agree that there is a role for corrective feedback in second language writing classes. However, many unanswered questions remain concerning which linguistic features to target and the type and amount of feedback to offer. This study examined two new pieces of writing by 151 learners of English as a Second Language (ESL), in order to investigate the effect of direct and metalinguistic written feedback on errors with the simple past tense, the present perfect tense, dropped pronouns, and pronominal duplication. This inquiry also considered the extent to which learner differences in language-analytic ability (LAA), as measured by the LLAMA F, mediated the effects of these two types of explicit written corrective feedback. Learners in the feedback groups were provided with corrective feedback on two essays, after which learners in all three groups completed two additional writing tasks to determine whether or not the provision of corrective feedback led to greater gains in accuracy compared to no feedback. Both treatment groups, direct and metalinguistic, performed better than the comparison group on new pieces of writing immediately following the treatment sessions, yet direct feedback was more durable than metalinguistic feedback for one structure, the simple past tense. Participants with greater LAA proved more likely to achieve gains in the direct feedback group than in the metalinguistic group, whereas learners with lower LAA benefited more from metalinguistic feedback. Overall, the findings of the present study confirm the results of prior studies that have found a positive role for written corrective feedback in instructed second language acquisition.

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© IMechE 2014. Controlled auto-ignition, also known as homogeneous charge compression ignition, has been the subject of extensive research because of their ability to provide simultaneous reductions in fuel consumption and NOx emissions from a gasoline engine. However, due to its limited operation range, switching between controlled auto-ignition and spark ignition combustion is needed to cover the complete operating range of a gasoline engine for passenger car applications. Previous research has shown that the spark ignition -controlled auto-ignition hybrid combustion (SCHC) has the potential to control the ignition timing and heat release process during the mode transition operations. However, it was found that the SCHC is often characterized with large cycle-to-cycle variations. The cyclic variations in the in-cylinder pressure are particularly noticeable in terms of both their peak values and timings while the coefficient of variation in the indicated mean effective pressure is much less. In this work, the cyclic variations in SCHC operations were analyzed by means of in-cylinder pressure and heat release analysis in a single-cylinder gasoline engine equipped with Variable Valve Actuation (VVA) systems. First, characteristics of the in-cylinder pressure traces during the spark ignition-controlled auto-ignition hybrid combustion operation are presented and their heat release processes analyzed. In order to clarify the contribution to heat release and cyclic variation in SCHC, a new method is introduced to identify the occurrence of auto-ignition combustion and its subsequent heat release process. Based on the new method developed, the characteristics of cyclic variations in the maximum rate of pressure rise and different stages of heat release process have been analyzed and discussed.

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Memristive switching serves as the basis for a new generation of electronic devices. Memristors are two-terminal devices in which the current is turned on and off by redistributing point defects, e.g., vacancies, which is difficult to control. Memristors based on alternative mechanisms have been explored, but achieving both the high On/Off ratio and the low switching energy desirable for use in electronics remains a challenge. Here we report memristive switching in a La_(0.7)Ca_(0.3)MnO_(3)/PrBa_(2)Cu_(3)O_(7) bilayer with an On/Off ratio greater than 103 and demonstrate that the phenomenon originates from a new type of interfacial magnetoelectricity. Using results from firstprinciples calculations, we show that an external electric-field induces subtle displacements of the interfacial Mn ions, which switches on/off an interfacial magnetic “dead” layer, resulting in memristive behavior for spin-polarized electron transport across the bilayer. The interfacial nature of the switching entails low energy cost about of a tenth of atto Joule for write/erase a “bit”. Our results indicate new opportunities for manganite/cuprate systems and other transition-metal-oxide junctions in memristive applications.

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Dissertação de Mestrado, Ciências da Linguagem, Faculdade de Ciências Humanas e Sociais, Universidade do Algarve, 2013

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The voltage source inverter (VSI) and current voltage source inverter (CSI) are widely used in industrial application. But the traditional VSIs and CSIs have one common problem: can’t boost or buck the voltage come from battery, which make them impossible to be used alone in Hybrid Electric Vehicle (HEV/EV) motor drive application, other issue is the traditional inverter need to add the dead-band time into the control sequence, but it will cause the output waveform distortion. This report presents an impedance source (Z-source network) topology to overcome these problems, it can use one stage instead of two stages (VSI or CSI + boost converter) to buck/boost the voltage come from battery in inverter system. Therefore, the Z-source topology hardware design can reduce switching element, entire system size and weight, minimize the system cost and increase the system efficiency. Also, a modified space vector pulse-width modulation (SVPWM) control method has been selected with the Z-source network together to achieve the best efficiency and lower total harmonic distortion (THD) at different modulation indexes. Finally, the Z-source inverter controlling will modulate under two control sequences: sinusoidal pulse width modulation (SPWM) and SVPWM, and their output voltage, ripple and THD will be compared.

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Renewable or sustainable energy (SE) sources have attracted the attention of many countries because the power generated is environmentally friendly, and the sources are not subject to the instability of price and availability. This dissertation presents new trends in the DC-AC converters (inverters) used in renewable energy sources, particularly for photovoltaic (PV) energy systems. A review of the existing technologies is performed for both single-phase and three-phase systems, and the pros and cons of the best candidates are investigated. In many modern energy conversion systems, a DC voltage, which is provided from a SE source or energy storage device, must be boosted and converted to an AC voltage with a fixed amplitude and frequency. A novel switching pattern based on the concept of the conventional space-vector pulse-width-modulated (SVPWM) technique is developed for single-stage, boost-inverters using the topology of current source inverters (CSI). The six main switching states, and two zeros, with three switches conducting at any given instant in conventional SVPWM techniques are modified herein into three charging states and six discharging states with only two switches conducting at any given instant. The charging states are necessary in order to boost the DC input voltage. It is demonstrated that the CSI topology in conjunction with the developed switching pattern is capable of providing the required residential AC voltage from a low DC voltage of one PV panel at its rated power for both linear and nonlinear loads. In a micro-grid, the active and reactive power control and consequently voltage regulation is one of the main requirements. Therefore, the capability of the single-stage boost-inverter in controlling the active power and providing the reactive power is investigated. It is demonstrated that the injected active and reactive power can be independently controlled through two modulation indices introduced in the proposed switching algorithm. The system is capable of injecting a desirable level of reactive power, while the maximum power point tracking (MPPT) dictates the desirable active power. The developed switching pattern is experimentally verified through a laboratory scaled three-phase 200W boost-inverter for both grid-connected and stand-alone cases and the results are presented.

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Using a Markov switching unobserved component model we decompose the term premium of the North American CDX index into a permanent and a stationary component. We establish that the inversion of the CDX term premium is induced by sudden changes in the unobserved stationary component, which represents the evolution of the fundamentals underpinning the probability of default in the economy. We find evidence that the monetary policy response from the Fed during the crisis period was effective in reducing the volatility of the term premium. We also show that equity returns make a substantial contribution to the term premium over the entire sample period.

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L’objectif de cette étude qualitative est de décrire et de comprendre le processus décisionnel sous-jacent à la rétroaction corrective d’un enseignant de langue seconde à l’oral. Pour ce faire, elle décrit les principaux facteurs qui influencent la décision de procéder à une rétroaction corrective ainsi que ceux qui sous-tendent le choix d’une technique de rétroaction particulière. Trois enseignantes de français langue seconde auprès d’un public d’adultes immigrants au Canada ont participé à cette recherche. Des séquences complètes d’enseignement ont été filmées puis présentées aux participantes qui ont commenté leur pratique. L’entretien de verbalisation s’est effectué sous la forme d’un rappel stimulé et d’une entrevue. Cet entretien constitue les données de cette étude. Les résultats ont révélé que la rétroaction corrective ainsi que le choix de la technique employée étaient influencés par des facteurs relatifs à l’erreur, à l’apprenant, au curriculum, à l’enseignant et aux caractéristiques des techniques. Ils ont également révélé que l’apprenant est au cœur du processus décisionnel rétroactif des enseignants de langue seconde. En effet, les participantes ont affirmé vouloir s’adapter à son fonctionnement cognitif, à son état affectif, à son niveau de langue et à la récurrence de ses erreurs. L’objectif de cette étude est d’enrichir le domaine de la formation initiale et continue des enseignants de L2. Pour cela, des implications pédagogiques ont été envisagées et la recommandation a été faite de porter à la connaissance des enseignants de L2 les résultats des recherches sur l’efficacité des techniques de rétroaction corrective, particulièrement celles qui prennent en compte les caractéristiques des apprenants.

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Multiferroic materials displaying coupled ferroelectric and ferromagnetic order parameters could provide a means for data storage whereby bits could be written electrically and read magnetically, or vice versa. Thin films of Aurivillius phase Bi6Ti2.8Fe1.52Mn0.68O18, previously prepared by a chemical solution deposition (CSD) technique, are multiferroics demonstrating magnetoelectric coupling at room temperature. Here, we demonstrate the growth of a similar composition, Bi6Ti2.99Fe1.46Mn0.55O18, via the liquid injection chemical vapor deposition technique. High-resolution magnetic measurements reveal a considerably higher in-plane ferromagnetic signature than CSD grown films (MS = 24.25 emu/g (215 emu/cm3), MR = 9.916 emu/g (81.5 emu/cm3), HC = 170 Oe). A statistical analysis of the results from a thorough microstructural examination of the samples, allows us to conclude that the ferromagnetic signature can be attributed to the Aurivillius phase, with a confidence level of 99.95%. In addition, we report the direct piezoresponse force microscopy visualization of ferroelectric switching while going through a full in-plane magnetic field cycle, where increased volumes (8.6 to 14% compared with 4 to 7% for the CSD-grown films) of the film engage in magnetoelectric coupling and demonstrate both irreversible and reversible magnetoelectric domain switching.

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L’objectif de cette étude qualitative est de décrire et de comprendre le processus décisionnel sous-jacent à la rétroaction corrective d’un enseignant de langue seconde à l’oral. Pour ce faire, elle décrit les principaux facteurs qui influencent la décision de procéder à une rétroaction corrective ainsi que ceux qui sous-tendent le choix d’une technique de rétroaction particulière. Trois enseignantes de français langue seconde auprès d’un public d’adultes immigrants au Canada ont participé à cette recherche. Des séquences complètes d’enseignement ont été filmées puis présentées aux participantes qui ont commenté leur pratique. L’entretien de verbalisation s’est effectué sous la forme d’un rappel stimulé et d’une entrevue. Cet entretien constitue les données de cette étude. Les résultats ont révélé que la rétroaction corrective ainsi que le choix de la technique employée étaient influencés par des facteurs relatifs à l’erreur, à l’apprenant, au curriculum, à l’enseignant et aux caractéristiques des techniques. Ils ont également révélé que l’apprenant est au cœur du processus décisionnel rétroactif des enseignants de langue seconde. En effet, les participantes ont affirmé vouloir s’adapter à son fonctionnement cognitif, à son état affectif, à son niveau de langue et à la récurrence de ses erreurs. L’objectif de cette étude est d’enrichir le domaine de la formation initiale et continue des enseignants de L2. Pour cela, des implications pédagogiques ont été envisagées et la recommandation a été faite de porter à la connaissance des enseignants de L2 les résultats des recherches sur l’efficacité des techniques de rétroaction corrective, particulièrement celles qui prennent en compte les caractéristiques des apprenants.

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This paper examines the impact of service orientation (SO) on relationship quality, and its consequences for consumer behaviour in the travel industry. Specifically consumers' positive behavioural intentions, perceptions of switching costs, and consumer activism are examined as consequences of relationship quality (RQ). A sample of leisure and business travellers on a cross sea ferry were surveyed using a consumer intercept methodology. We find that SO has a significant and positive impact on RQ and that RQ has a positive impact on positive behavioural intentions and perceptions of switching costs. Both RQ and switching costs were found to reduce consumer activism. The implications of these findings for service managers and academics are discussed and directions forfuture research presented.

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- This paper presents a validation proposal for development of diagnostic and prognostic algorithms for SF6 puffer circuit-breakers reproduced from actual site waveforms. The re-ignition/restriking rates are duplicated in given circuits and the cumulative energy dissipated in interrupters by the restriking currents. The targeted objective is to provide a simulated database for diagnosis of re-ignition/restrikes relating to the phase to earth voltage and the number of re-ignition/restrikes as well as estimating the remaining life of SF6 circuit-breakers. The model-based diagnosis of a tool will be useful in monitoring re-ignition/restrikes as well as predicting a nozzle’s lifetime. This will help ATP users with practical study cases and component data compilation for shunt reactor switching and capacitor switching. This method can be easily applied with different data for the different dielectric curves of circuit breakers and networks. This paper presents modelling details and some of the available cases, required project support, the validation proposal, the specific plan for implementation and the propsed main contributions.

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A recent Australian survey of beginning teachers indicates that issue of classroom management continues to be a key concern for early career educators (Australian Education Union, 2007). This finding is supported by the wider literature that identifies managing the classroom, particularly managing behaviour within the classroom, as critical issues for early career teachers (Arends, 2006; Charles, 2004; Groundwater-Smith, Ewing & Le Cornu, 2007). In fact, struggling to manage student behaviour and maintain positive relationships with students are among the top reasons for teachers leaving the teaching profession (Charles, 2004). So, how does a teacher effectively organise and manage up to thirty students learning and behaviour at any one time? The issue of classroom management is a persistent one for all teachers, but is particularly daunting for new teachers. Historically, classrooms were established on strong hierarchical structures that relied heavily on teacher control and authority. However, more recent approaches to managing the classroom are proactive and more collaborative. That is not to say that there exists a single management recipe, far from it. Beginning teachers must view possible approaches to managing the classroom in light of their own beliefs about teaching and learning, their current classroom practice and variables from the context in which they are teaching.