Regulation Theory

This paper reviews the design of regulation loops for power converters. Power converter control being a vast domain, it does not aim to be exhaustive. The objective is to give a rapid overview of the main synthesis methods in both continuous- and discrete-time domains.Comment: 23 pages, contribution to the 2014 CAS - CERN Accelerator School: Power Converters, Baden, Switzerland, 7-14 May 201

Reading in a foreign language: Strategic variation between readers of differing proficiency

For university language students who are required to deal with literary texts for linguistic or literary purposes, there is hardly any transitional stage between short adapted expository texts, read in the early stages of language learning, and complex literary texts, encountered at university in the literature class. Language readers must then make a substantial mental effort to understand texts intended for a native readership. In challenging reading mode, the quality of reading depends on the efficiency of problem-solving operations, including evaluative and executive strategies, put into place in order to attempt to fill in the comprehension gaps present in complex texts. Although reading strategies used by foreign language learners have been identified and categorised by research, the conditions of their use and their relationships are still unclear. Moreover, to my knowledge, no empirical investigation has focused specifically on comprehension monitoring in the context of foreign language literary texts. Literature instruction would benefit from such a study. Using verbal reports to elicit data, this study proposes to examine how proficient and less proficient university students of French, at intermediate level of instruction, implement problem-solving strategies when reading literary texts. Strategies such as guessing at words, consulting a dictionary, and translating mentally, are studied in relation to their contribution to the overall monitoring cycle. The results obtained indicate that proficient and less proficient readers tend to use the same strategies but with different purposes. The study demonstrates that the major difference between the two groups of respondents resides in ability some readers have to integrate meaning and construct text in a cohesive and synthetic fashion

WHAT DOES GREATER ECONOMIC INTEGRATION MEAN FOR INTERREGIONAL INCOME INEQUALITY? AN ANALYSIS OF OECD COUNTRIES AND REGIONS

This paper provides an overview of the evolution of interregional income disparities among 304 regions from 27 OECD countries between 1995 and 2005. This sample of regions allows to compare interregional income inequality in different economic integration systems: the USA (used as an example of a political union), the European Economic and Monetary Union (EMU), the European Union (EU), and the North-American Free Trade Agreement (NAFTA). Overall, interregional income inequality is lower among US states and EMU regions than among EU regions and NAFTA regions. Thus, interregional income inequality seems to be negatively related to economic integration. However, income inequality has risen among US states, while it has been stable among OECD regions, and has even decreased among European regions. Moreover, rank-size scatterplots suggest that inequality is higher among low-income regions than among richer regions.REGIONAL INEQUALITY, ECONOMIC INTEGRATION, EUROPEAN UNION, EMU, NAFTA, ZIPF LAW

Interest Rate Setting at the ECB Following the Financial and Sovereign Debt Crises, in Real-Time

This paper examines European Central Bank (ECB) policy decisions to adjust the repo rate. We estimate a forward-looking, ordered-logit model using real-time and expectations data. In particular, we investigate the impact of the 2007-2009 financial and sovereign debt crises on the ECB interest rate policy. We find that the repo rate is more likely to rise when real economic activity (economic sentiment) is strong, and the ECB's decision to increase the repo rate is not affected by inflation forecasts. We find the ECB responds to an increasing sovereign risk premium by lowering the repo rate. In addition, we examine whether the change in ECB Presidency from Willem Duisenberg to Jean-Claude Trichet and the recent financial crisis induced a policy shift. We do not find a regime switch from the Duisenberg presidency to Trichet presidency, but we find that the financial crisis has reduced the importance of the exchange rate, and also how strongly the ECB reacts to improvements in economic activity

Flexibility and Interaction at a Distance: A Mixed-Model Environment For Language Learning

This article reports on the process of design and development of two language courses for university students at beginning levels of competence. Following a preliminary experience in a low-tech environment for distance language learning and teaching, and a thorough review of the available literature, we identified two major challenges that would need to be addressed in our design: (1) a necessity to build sufficient flexibility into the materials to cater to a variety of learners' styles, interests and skill levels, therefore sustaining learners' motivation; and (2) a need to design materials that would present the necessary requisites of authenticity and interactivity identified in the examined literature, in spite of the reduced opportunities for face-to-face communication. In response to these considerations, we designed and developed learning materials and tasks to be distributed on CD-ROM, complemented by a WebCT component for added interactivity and task authenticity. Although only part of the original design was implemented, and further research is needed to assess the impact of our environment on learning outcomes, the results of preliminary evaluations are encouraging

Experimental study of sandwich structures as armour against medium-velocity impacts

An experimental impact study has been conducted on sandwich structures to identify and improve armour solutions for aeronautical applications. The objectives are to find the best configurations, i.e. the non-perforated targets with the minimal weight and back deformations. Medium-velocity impacts (120 m/s) have been conducted using a 127 g spherical projectile. The targets are simply supported at the rear of the structure. Two potential choices of front skin have been identified for the sandwich structure: 3 mm thick AA5086-H111 aluminium plates and dry aramid stitched fabrics (between 8 and 18 plies). The dry stitched fabrics appear to be an original solution, which associates a lightweight structure and a good perforation resistance. Moreover, a strong coupling has been found between the front skin and the core. The impact tests indicate that aluminium honeycomb core associated with aluminium skins show mitigated results. However, the combination of dry fabric front skin and aluminium honeycomb show better performances than aluminium sandwiches, with a global weight decrease

Validation of low velocity impact modelling on different stacking sequences of CFRP laminates and influence of fibre failure

This paper presents a validation of low-velocity impact Finite Element (FE) modelling. Based on switching ply location of reference layup [02,452,902,-452]s T700GC/M21 laminated plates from Bouvet et al. (2012) [1], twelve possible layups under a constraint of double-ply, mirror-symmetric, balanced, and quasi- isotropic are allowed. However only seven layups are chosen for the study and one of them reveals the importance of longitudinal fibre compressive failure during impact events. Therefore, the second aspect of this work is the introduction of a fibre compressive failure law associated with fracture damage development. This makes it possible to improve the simulation for all seven different layups. Good correspondence is achieved between simulation and experiment for aspects such as delamination areas/shapes and force–displacement responses. The influence of the addition of fibre compressive failure according to fracture toughness in mode I is discussed

Failure analysis of CFRP laminates subjected to Compression After Impact: FE simulation using discrete interface elements

This paper presents a model for the numerical simulation of impact damage, permanent indentation and compression after impact (CAI) in CFRP laminates. The same model is used for the formation of damage developing during both low-velocity / low-energy impact tests and CAI tests. The different impact and CAI elementary damage types are taken into account, i.e. matrix cracking, fiber failure and interface delamination. Experimental tests and model results are compared, and this comparison is used to highlight the laminate failure scenario during residual compression tests. Finally, the impact energy effect on the residual strength is evaluated and compared to experimental results

Low velocity impact modeling in composite laminates capturing permanent indentation

This paper deals with impact damage and permanent indentation modeling. A numerical model has been elaborated in order to simulate the different impact damage types developing during low velocity/low energy impact. The three current damage types: matrix cracking, fiber failure and delamination, are simulated. Inter-laminar damage, i.e. interface delamination, is conventionally simulated using interface elements based on fracture mechanics. Intra-laminar damage, i.e. matrix cracks, is simulated using interface elements based on failure criterion. Fiber failure is simulated using degradation in the volume elements. The originality of this model is to simulate permanent indentation after impact with a ‘‘plastic-like’’model introduced in the matrix cracking elements. This model type is based on experimental observations showing matrix cracking debris which block crack closure. Lastly, experimental validation is performed, which demonstrates the model’s satisfactory relevance in simulating impact damage. This acceptable match between experiment and modeling confirms the interest of the novel approach proposed in this paper to describe the physics behind permanent indentation

Modelling of impact damage and permanent indentation on laminate composite plate

This paper deals with impact damage and permanent indentation modelling. A model enabling the formation of damages developing during a low velocity / low energy impact test on laminate composite panels has been elaborated. The different impact damages developing during an impact test, i.e. matrix cracking, fibres failure and interfaces delamination, are simulated. The interlaminar damages, i.e. interfaces delamination, are classically simulated thanks to interface finite elements based on the fracture mechanics. The particularity of this model is to account for the intralaminar damages, i.e. matrix cracks, thanks to interface finite elements which respect their discontinue character. These interface elements allow equally to simulate the permanent indentation during the impact unloading. This impact mark modelling is very original in the literature, and should allow to entirely design a composite structure thanks to impact damage tolerance