The present quantitative study investigates MA-students’ comprehension of lectures in the first language (L1) and in English at a large university in Sweden. Forty-five students responded to a self-assessment questionnaire survey regarding their comprehension of lectures in the L1 and lectures in English. The scores from these were compared to each other to see if English lectures are more difficult to comprehend than lectures in the L1 and if so, to what extent. The findings show that, although not substantial, most students find almost all aspects regarding English lectures to be more difficult than L1 lectures. This is in line with what other studies investigating the effects of English Medium Instruction in higher education have found. The most prominent issues were with unfamiliar vocabulary and expressions as well as unclear pronunciation of content. The results suggest that there is a need to improve students’ and lecturers’ English proficiency as well as the effectiveness of lectures in higher education, regardless of the language of instruction.

The Ministry of Education in Abu Dhabi launched an extensive reform initiative developed by the Abu Dhabi Education Council (ADEC) in partnership with international operators. The reform has introduced innovative teaching methodologies, modern books, a new curriculum and the use of English as a medium of instruction (EMI) in mathematics and science classes. The research carried out for this thesis investigated 11 Emirati female teachers. The data was collected from interviews and several informal observations carried out in a public middle school in a town outside Abu Dhabi city, UAE. The rationale for this study is to critically investigate the effects that rapid reform is having on the performance of the female teachers in the classroom and the impact of this speedy reform on their professional and personal lives so as to highlight differences between reform theory and practice. This study is significant because few studies on female teachers in a Gulf educational reform environment have been undertaken and it is essential to uncover the foreign and non-egalitarian nature of the reform programme. Therefore, the study’s aims are to highlight teacher perspectives and teacher marginalization, EMI and consider whether the reform is being implemented successfully at the classroom level. Of course, an important aim of this critical study has also been to raise the consciousness of those participating in the reform. This study has revealed mostly negative perceptions regarding the Abu Dhabi education reform programme, in particular with teachers’ perceptions of the work environment and the new pedagogy. It has also disclosed several instances of teacher marginalization as the result of a top-down reform and has exposed a prevailing sentiment of teacher disempowerment because of the presence of foreigners operating in the country. Teacher perceptions regarding EMI have been numerous in particular with cultural issues relating to the use of EMI in mathematics and science classes. Surprisingly, the study revealed a few unexpected positive findings with certain aspects of reform.

<p>This thesis is a project carried out at the “Centre for RF Measurements Technology of Gävle”. The first aim of this work was basically to develop an EMI measurement system, to that purpose, it has been used an EMI Tester receiver, Spectrum Analyzer and a broadband antenna. Tables and graphics are shown to provide the values of the different detectors utilized.</p><p>Using this measurement system, an interference file was recorded and then inserted in a Bluetooth communication model. The interference file was simulated with Matlab Simulink, to check how the interference affected the communication; the effects of the signal degradation are presented in a graphic.</p><p>Finally a real Bluetooth communication was established using two Bluetooth modules from Free2Move Company, to prove that the effect of microwave oven interferences produces the increase of transmission time and therefore decrease the Throughput.</p>

A gate driver IC with programmable driving strength to reduce electromagnetic interference (EMI) in SMPS is presented in this thesis. The design builds on previous segmented gate driver designs that have been used to improve light load efficiency. The presented solution is to dynamically adjust the output resistance Rout at the arrival of each gate pulse to minimize EMI while maintaining low switching loss. Dynamically adjusting Rout is not possible with conventional gate driver designs. Thus, a segmented gate driver is designed and fabricated in the AMS 0.35μm 40V HVCMOS process. Unlike traditional snubber circuits, the proposed method does not require extra discrete components that dissipate energy. Experimental results indicate up to a 7dBμV improvement in peak Conducted EMI (CEMI) between 20 MHz and 30 MHz and a 150μV/m improvement in peak Radiated EMI (REMI) between 88 MHz and 216 MHz.

A gate driver IC with programmable driving strength to reduce electromagnetic interference (EMI) in SMPS is presented in this thesis. The design builds on previous segmented gate driver designs that have been used to improve light load efficiency. The presented solution is to dynamically adjust the output resistance Rout at the arrival of each gate pulse to minimize EMI while maintaining low switching loss. Dynamically adjusting Rout is not possible with conventional gate driver designs. Thus, a segmented gate driver is designed and fabricated in the AMS 0.35μm 40V HVCMOS process. Unlike traditional snubber circuits, the proposed method does not require extra discrete components that dissipate energy. Experimental results indicate up to a 7dBμV improvement in peak Conducted EMI (CEMI) between 20 MHz and 30 MHz and a 150μV/m improvement in peak Radiated EMI (REMI) between 88 MHz and 216 MHz.

This thesis is a project carried out at the “Centre for RF Measurements Technology of Gävle”. The first aim of this work was basically to develop an EMI measurement system, to that purpose, it has been used an EMI Tester receiver, Spectrum Analyzer and a broadband antenna. Tables and graphics are shown to provide the values of the different detectors utilized. Using this measurement system, an interference file was recorded and then inserted in a Bluetooth communication model. The interference file was simulated with Matlab Simulink, to check how the interference affected the communication; the effects of the signal degradation are presented in a graphic. Finally a real Bluetooth communication was established using two Bluetooth modules from Free2Move Company, to prove that the effect of microwave oven interferences produces the increase of transmission time and therefore decrease the Throughput.

DE LA TESISEsta Tesis se centra en el estudio de las perturbaciones conducidas generadas por un ondulador de tensión en configuración de puente y alimentado de red a través de un rectificador no controlado. El objetivo de esta Tesis es poder identificar el origen de las perturbaciones y poder cuantificar de una forma relativamente rápida y sencilla el efecto de diversos factores (topología, lay-out, técnicas de modulación y tipo de componentes) sobre la propagación de las mismas. Para ello se ha desarrollado una metodología de estudio que es perfectamente válida y aplicable sin grandes dificultades a otro tipo de topologías, utilicen o no la conmutación dura. El método de estudio se basa en la estructura fuente-medio de propagación-perturbación y en el planteamiento de circuitos equivalentes de parámetros concentrados, cuyas ecuaciones son resueltas en el dominio frecuencial. En esta metodología, que permite discriminar la contribución de los dos modos de propagación (modo común, MC, y modo diferencial, MD) al nivel global de perturbación, se ha primado la sencillez y robustez de simulación del modelo frente a la exactitud. El método propuesto ofrece buenos resultados hasta una frecuencia de 5MHz aproximadamente.En el Capítulo 1 se introduce el problema planteado por las perturbaciones electromagnéticas generadas por los convertidores conmutados, se describe y caracteriza todo el instrumental (analizador de espectros, red artificial, pinza amperimetrica de alta frecuencia), la planta experimental así como la herramienta matemática utilizada. En el Capítulo 2 se aborda el tema de la caracterización del medio de propagación de las perturbaciones. En primer lugar se describe el método de medida de impedancias utilizado, que es una de las aportaciones de la Tesis, para después presentar los resultados obtenidos a la hora de caracterizar las impedancias significativas del sistema. A partir de estas medidas se obtienen circuitos equivalentes de parámetros concentrados que caracterizan el medio de propagación. En el Capítulo 3 se estudian las perturbaciones que generan individualmente el rectificador de entrada y el ondulador. El estudio se lleva a cabo sobre una configuración monofásica para una mayor simplicidad del mismo. En este Capítulo se caracteriza la fuente de perturbación en el caso de ambos convertidores y, junto con la caracterización del camino de propagación obtenida en el Capítulo 2, se calculan las perturbaciones generadas. Gracias a los modelos obtenidos es posible calcular el efecto de diversos parámetros sobre las perturbaciones y la contribución de ambos modos de propagación (modo común y diferencial) al nivel final de perturbación. En el Capítulo 4 se combinan los resultados obtenidos en el Capítulo 3 para obtener la perturbación que se propaga hacia la red en la asociación en cascada de ambos convertidores. Tanto en el Capítulo 3 como en el Capítulo 4 la validación del modelo se lleva a cabo por comparación de los resultados experimentales con los obtenidos por simulación.Una vez cumplidos los objetivos de la Tesis, el Capítulo 5 ilustra la validez de la metodología desarrollada en el Capítulo 3. En el Capítulo 5 se aplica esta metodología al estudio de las perturbaciones en MC generadas por el ondulador y que se propagan hacia la carga. Este Capítulo es una extensión al caso trifásico y un ejemplo de aplicación de gran interés industrial. En este Capítulo aparece una de las aportaciones de la Tesis: una técnica de modulación orientada a la reducción del MC generado por el ondulador. Para demostrar la validez del modelo se comparan las medidas de corriente en MC en el lado carga con los valores obtenidos a partir del modelo.Las conclusiones de la Tesis aparecen en el Capítulo 6. También se describen los trabajos futuros que se sugieren a partir de los resultados de la Tesis. / OF THE THESISThe subject of this Thesis is to study conducted disturbances produced by a voltage source inverter supplied from the mains through a rectifier. The main goal is to identify the origin of conducted disturbances and also quantify in a quick and easy way the influence of different factors (topology and lay-out of the converter, switching patterns, components) on EMI . In order to achieve this goal, a systematic analysis approach has been developed. This new methodology can be easily applied to any converter topology, whatever the kind of switching (soft or hard) is used. The analysis is based on the source of noise-propagation path-disturbance approach and consists in the setting out of two equivalent circuits of lumped parameters, one for each mode of propagation. This separate treatment of both modes of propagation allows the calculation of their contribution to the global level of disturbance. Equations drawn from these equivalent circuits are solved in the frequency domain. This approach avoids all the problems of time-domain simulations and provides robust and quick simulations rather than very accurate results. The simulation results of this methodology show a good agreement with experimental measures up to 5MHz.Chapter 1 describes problems caused by electromagnetic disturbances generated by switched power converters. The state of the art about this matter is presented. All instruments used to carry out measures (spectrum analyser, LISN, HF current clamp) are described and modelled. The experimental set-up is thoroughly described. Also some considerations about mathematical tools used are presented.Chapter 2 is devoted to study the propagation path of disturbances. First of all, the impedance measuring method is described, which is one of the contributions of the Thesis. After that, main impedances of the system are identified and measured. From these results, equivalent circuits of lumped parameters that model the main impedances of the propagation path are derived.In Chapter 3, disturbances generated in a single phase arrangement by the rectifier and the inverter working separately are studied. Source of noise in both cases are identified and modelled. Finally, disturbances are calculated taking into account results of Chapter 2.Results obtained in Chapter 3 are combined in Chapter 4 in order to obtain the disturbance reaching the mains when both converters (rectifier and inverter) are connected in cascade. Experimental validation of the model are presented in Chapters 3 and 4, by comparing results of measures with those provided by simulation.Once main goals of the Thesis are achieved, Chapter 5 shows the validity of the methodology developed in Chapter 3 when it is used to calculate the CM currents in the load side of a three-phase inverter. In this Chapter another contribution of the Thesis is presented: a new modulation technique for three-phase inverters specially intended to reduce CM currents in the load side. Comparison between simulation results and measurements show a good agreement.The conclusions of the Thesis are summarised in Chapter 6. The future works suggested by the results of the Thesis are also presented.

This research focuses on the development of engineered materials, also known as meta- materials, with desirable effective constitutive parameters: electric permittivity (epsilon) and magnetic permeability (mu) to decouple antennas and noise mitigation from electromagnetic systems. An interesting phenomenon of strong relevance to a wide range of problems, where electromagnetic interference is of concern, is the elimination of propagation when one of the constitutive parameters is negative. In such a scenario, transmission of electromagnetic energy would cease, and hence the coupling between radiating systems is reduced. In the first part of this dissertation, novel electromagnetic artificial media have been developed to alleviate the problem of mutual coupling between high-profile and ow-profile antenna systems. The developed design configurations are numerically simulated, and experimentally validated. In the mutual coupling problem between high-profile antennas, a decoupling layer based on artificial magnetic materials (AMM) has been developed and placed between highly-coupled monopole antenna elements spaced by less than Lambda/6, where Lambda is the operating wavelength of the radiating elements. The decoupling layer not only provides high mutual coupling suppression (more than 20-dB) but also maintains good impedance matching and low correlation between the antenna elements suitable for use in Multiple-Input Multiple-Output (MIMO) communication systems. In the mutual coupling problem between low-profile antennas, novel sub-wavelength complementary split-ring resonators (CSRRs) are developed to decouple microstrip patch antenna elements. The proposed design con figuration has the advantage of low-cost production and maintaining the pro file of the antenna system unchanged without the need for extra layers. Using the designed structure, a 10-dB reduction in the mutual coupling between two patch antennas has been achieved. The second part of this dissertation utilizes electromagnetic artificial media for noise mitigation and reduction of undesirable electromagnetic radiation from high-speed printed-circuit boards (PCBs) and modern electronic enclosures with openings (apertures). Numerical results based on the developed design configurations are presented, discussed, and compared with measurements. To alleviate the problem of simultaneous switching noise (SSN) in high-speed microprocessors and personal computers, a novel technique based on cascaded CSRRs has been proposed. The proposed design has achieved a wideband suppression of SSN and maintained a robust signal integrity performance. A novel use of electromagnetic bandgap (EBG) structures has been proposed to mitigate undesirable electromagnetic radiation from enclosures with openings. By using ribbon of EBG surfaces, a significant suppression of electromagnetic radiation from openings has been achieved.

This thesis develops a power line carrier(PLC) communication module using FSK modulation technology by integration of PLC chip, with various hardware circuits such as DSP, signal coupling and amplifier circuits, filter. The communication performance and conduction EMI tests and executed for the communication module developed. The PLC module is then applied for appliance control of commercial customers to fulfill the demand response function for energy conservation by reducing the summer peak loading. Besides sending the load control command from central station in the smart grid, the power consumption of various appliances can also be collected and transmitted back to the control station via two way communication with the PLC communication module. Finally, the broadband PLC (BPLC) is applied for the CCTV supervision in system to support asset management of distribution room to prevent the power equipment from steal. With the remote control of light brightness and CCTV lens with high data transmission rate provided, the communication performance of PLC can therefore be verified in this study.

In recent year, the single-end transmission line is instead by differential transmission line . Differential signaling has been generally used in the high speed digital interconnection on the PCBs. The advantages of the differential signal with a low noise and high common-mode noise suppression, but the differential mode transmission signal is a very high quality requirements of circuit, the two line should have same length and symmetry, but in the practical package the circuit is not this case, In the limit space ,the differential signal should through the bend, it would lead to the phase skew and produce the differential to common mode conversion noise on the signal integrity and electromagnetic interference(EMI) problem. In this paper a new type of bend is proposed that reduces differential -to-common mode conversion noise for high speed digital circuit. This novel structure can reduce the mode conversion over 20dB at DC to 10GHz, and the differential insertion loss remains low. Also time domain the TDT common mode noise from 0.09V to 0.008V as compared with the bended differential transmission line using the edge couple bend. Moreover, the measurement on proposed structure show a close match with the full-wave simulation result. However, this structure does not have a reference plane, the return path is not complete, the current is easy to radiate out, so I design a guard trace to reduce the radiation in this structure.