There has been an increasing focus on web-based instruction (WBI) systems which accommodate individual differences in educational environments. Many of those studies have focused on the investigation of learners’ behaviour to understand their preferences, performance and perception using hypermedia systems. In this thesis, existing studies focus extensively on performance measurement attributes such as time spent using the system by a user, gained score and number of pages visited in the system. However, there is a dearth of studies which explore the relationship between such attributes in measuring performance level. Statistical analysis and data mining techniques were used in this study. We built a WBI program based on existing designs which accommodated learner’s preferences. We evaluated the proposed system by comparing its results with related studies. Then, we investigated the impact of related individual differences on learners’ preferences, performance and perception after interacting with our WBI program. We found that some individual differences and their combination had an impact on learners' preferences when choosing navigation tools. Consequently, it was clear that the related individual differences altered a learner’s preferences. Thus, we did further investigation to understand how multiple individual differences (Multi-ID) could affect learners’ preferences, performance and perception. We found that the Multi-ID clearly altered the learner’s preferences and performance. Thus, designers of WBI applications need to consider the combination of individual differences rather than these differences individually. Our findings also showed that attributes relationships had an impact on measuring learners’ performance level on learners with Multi-ID. The key contribution of this study lies in the following three aspects: firstly, investigating the impact of our proposed system, using three system features in the design, on a learner’s behavior, secondly, exploring the influence of Multi-ID on a learner’s preferences, performance and perception, thirdly, combining the three measurement attributes to understand the performance level using these measuring attributes.

A Study of the Effect of Cognitive Styles Learning Approaches on Identifying English Clause Tasks Lieu, Pin-huei Abstract The main purpose of this study intended to discuss the effect of Field Independent subjects(FIs), Field Dependent subjects (FDs) of junior high school using Discovery, Rule Learning approaches on identifying English clauses task. The questions explored here were: 1.How did FIs and FDs differently perform on identifying English clauses tasks. 2.How did Discovery and Rule learning approaches differently perform on identifying English clauses tasks. 3.How did FIs / FDs and Discovery/Rule learning approaches create interactive effect on identifying English clauses tasks. The study used experimental research method. The subjects were 90 third grade students of junior high school. According to the scores of Embedded Figures Test students were divided into FI and FD. Then depending on the scores of the prior test on identifying English clauses task, FIs and FDs match with two group to accept Discovery and Rule learning approaches , and each one was composed of 10 students. The instruments was ¡§ Embedded Figures Test¡¨ , ¡§self-made that clauses test ,¡¨and the information acquired was dealt with statistical testing through 2*2 ANOVA .The results indicated as followings. 1.An interactive effect of cognitive style and learning approaches were found through ANOVA. FIs using Discovery learning performed better than using Rule learning ,and FDs using Rule learning performed better using Discovery learning .In sum ,FIs appropriately use Discovery learning approach and FDs appropriately use Rule learning approach on identifying English clauses task. 2.Cognitive style lives up significantly different level .FIs performed better than those of FDs. 3.No overall difference were found between Discovery and Rule learning approach. Finally the study discussed the above results in more detail ,and provided suggestions and references of research concerning teaching of English clauses .

Since single nanopores were firstly proposed as a potential rapid and low-cost tool for DNA sequencing in 1990s (PNAS, 1996, 93, 13770), extensive studies on both biological and synthetic nanopores and nanochannels have been reported. Nanochannel based stochastic sensing at single molecular level has been widely reported through the detection of transient ionic current changes induced by geometry blockage due to analytes translocation. Novel properties, including ion current rectification (ICR), memristive and memcapacitive behaviors were reported. These fundamental properties of nanochannels arise from the nanoscale dimensions and enables applications not only in single molecule sensing, but also in drug delivery, electrochemical energy conversion, concentration enrichment and separation, nanoprecipitation, nanoelectronics etc. Electrostatic interactions at nanometer-scale between the fixed surface charges and mobile charges in solution play major roles in those applications due to high surface to volume ratio. However, the knowledge of surface charge density (SCD) at nanometer scale is inaccessible within nanoconfinement and often extrapolated from bulk planar values. The determination of SCD at nanometer scale is urgently needed for the interpretation of aforementioned phenomena. This dissertation mainly focuses on the determination of SCD confined at a nanoscale device with known geometry via combined electroanalytical measurements and theoretical simulation. The measured currents through charged nanodevices are different for potentials with the same amplitude but opposite polarities, which deviates away from linear Ohm's behavior, known as ICR. Through theoretical simulation of experiments by solving Poisson and Nernst-Planck equations, the SCD within nanoconfinement is directly quantified for the first time. An exponential gradient SCD is introduced on the interior surface of a conical nanopre based on the gradient distribution of applied electric field. The physical origin is proposed based on the facilitated deprotonation of surface functional groups by the applied electric field. The two parameters that describe the non-uniform SCD distribution: maximum SCD and distribution length are determined by fitting high- and low-conductivity current respectively. The model is validated and applied successfully for quantification and prediction of mass transport behavior in different electrolyte solutions. Furthermore, because the surface charge distribution, the transport behaviors are intrinsicaly heterogeneous at nanometer scale, the concept is extended to noninvasively determine the surface modification efficacy of individual nanopore devices. Preliminary results of single molecule sensing based on streptavidin-iminobiotin are included. The pH dependent binding affinity of streptavidin-iminobiotin binding is confirmed by different current change signals ("steps" and "spikes") observed at different pHs. Qualitative concentration and potential dependence have been established. The chemically modified nanopores are demonstrated to be reusable through regenerating binding surface.

The trend towards more and all-electric apparatuses and more electrification will lead to higher electrical demand. Increases in electrical power demand can be provided by either higher currents or higher voltages. Due to "weight" and "voltage" drop, a raise in the current is not preferred; so, "higher voltages" are being considered. Another trend is to reduce the size and weight of apparatuses. Combined, these two trends result in the high voltage, high power density concept. It is expected that by 2030, 80% of all electric power will flow through "power electronics systems". In regards to the high voltage, high power density concept described above, "wide bandgap (WBG) power modules" made from materials such as "SiC and GaN (and, soon, Ga2O3 and diamond)", which can endure "higher voltages" and "currents" rather than "Si-based modules", are considered to be the most promising solution to reducing the size and weight of "power conversion systems". In addition to the trend towards higher "blocking voltage", volume reduction has been targeted for WBG devices. The blocking voltage is the breakdown voltage capability of the device, and volume reduction translates into power density increase. This leads to extremely high electric field stress, E, of extremely nonuniform type within the module, leading to a higher possibility of "partial discharge (PD)" and, in turn, insulation degradation and, eventually, breakdown of the module. Unless the discussed high E issue is satisfactorily addressed and solved, realizing next-generation high power density WBG power modules that can properly operate will not be possible. Contributions and innovations of this Ph.D. work are as follows. i) Novel electric field grading techniques including (a) various geometrical techniques, (b) applying "nonlinear field-dependent conductivity (FDC) materials" to high E regions, and (c) combination of (a) and (b), are developed; ii) A criterion for the electric stress intensity based upon accurate dimensions of a power device package and its "PD measurement" is presented; iii) Guidelines for the electrical insulation design of next-generation high voltage (up to 30 kV), high power density "WBG power modules" as both the "one-minute insulation" and PD tests according to the standard IEC 61287-1 are introduced; iv) Influence of temperature up to 250°C and frequency up to 1 MHz on E distribution and electric field grading methods mentioned in i) is studied; and v) A coupled thermal and electrical (electrothermal) model is developed to obtain thermal distribution within the module precisely. All models and simulations are developed and carried out in COMSOL Multiphysics. / Doctor of Philosophy / In power engineering, power conversion term means converting electric energy from one form to another such as converting between AC and DC, changing the magnitude or frequency of AC or DC voltage or current, or some combination of these. The main components of a power electronic conversion system are power semiconductor devices acted as switches. A power module provides the physical containment and package for several power semiconductor devices. There is a trend towards the manufacturing of electrification apparatuses with higher power density, which means handling higher power per unit volume, leading to less weight and size of apparatuses for a given power. This is the case for power modules as well. Conventional "silicon (Si)-based semiconductor technology" cannot handle the power levels and switching frequencies required by "next-generation" utility applications. In this regard, "wide bandgap (WBG) semiconductor materials", such as "silicon carbide (SiC)"," gallium nitride (GaN)", and, soon, "gallium oxide" and "diamond" are capable of higher switching frequencies and higher voltages, while providing for lower switching losses, better thermal conductivities, and the ability to withstand higher operating temperatures. Regarding the high power density concept mentioned above, the challenge here, now and in the future, is to design compact WBG-based modules. To this end, the extremely nonuniform high electric field stress within the power module caused by the aforementioned trend and emerging WBG semiconductor switches should be graded and mitigated to prevent partial discharges that can eventually lead to breakdown of the module. In this Ph.D. work, new electric field grading methods including various geometrical techniques combined with applying nonlinear field-dependent conductivity (FDC) materials to high field regions are introduced and developed through simulation results obtained from the models developed in this thesis.

Le style cognitif est un domaine bien étudié et approfondi dans les pays occidentaux, surtout aux États-Unis, mais il reste peu développé par les chercheurs chinois. Cette notion est à propos de la personnalité, de la façon de traiter des informations reçus chez les différents individus, et elle peut aussi porter une influence sur l’éducation, qui contient l’éducation de mathématiques. En Chine, les mathématiques sont une matière principale et importante dans le système éducatif, et sous un contexte particulier de la société chinoise, un système éducatif chinois s’est formé. La phase secondaire est la phase la plus représentative dans le système éducatif chinois, et sous le contexte particulier, il faut considérer les styles cognitifs les plus fréquents chez les élèves et aussi le style cognitif de chaque élève pour trouver des méthodes d’améliorer l’éducation mathématique aux écoles secondaires. Pour ce but, il faut bien prendre en considération le côté d’apprentissage et le côté de didactique. Ainsi, notre travail va commencer par une étude des recherches et des théories matures de style cognitif qui serviront de base théorique, et ensuite avec la présentation du contexte de l’éducation mathématique en Chine nous allons pouvoir mieux le lier avec le style cognitif. Avec les résultats de notre recherche nous analysons et proposons des manières possibles au niveau de politique, de didactique et d’apprentissage pour améliorer l’éducation mathématique aux écoles secondaires en profitant des théories de style cognitif et des résultats de notre recherche. / The cognitive style is a well-developed and studied domain in western countries, especially in USA, but it is still a new ground for Chinese researchers. This conception is about the personality, the way to treat the received information for individuals, and it can also influence the education, which includes of course the mathematic education. In China, the mathematic is a principle subject at school in the Chinese educational system. With a special background in the society of China, a special educational system has been formed. The secondary education is the most typical in this educational system, and we need to think about the most frequent cognitive styles among Chinese students and also the cognitive style of each student to find the best methods to make the mathematic education better and more appropriate. For this destination, we need to consider the side of learning and the side of teaching. Therefore, our work will start by a presentation of the researches of cognitive styles and those mature theories, which can be our theoretical base, and then we will connect the education of mathematic with cognitive styles by a presentation of the situation of mathematics education in China. With the results of our research, we will analysis and make some advises about the politics of education, of the teaching and learning methods to try to ameliorate the mathematic education in China with help of cognitive styles and this research.