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The purpose of this study was to investigate how reciprocal teaching affected vocabulary acquisition and reading comprehension in four at-risk students in a fourth grade inclusion classroom. A single subject research study method was used to measure the baseline of each student. Subsequently, students were assessed daily after receiving two interventions that alternated during a six week period: reciprocal teaching and guided reading. Key findings indicated that three of the participants increased in both vocabulary acquisition and reading comprehension skills. However, there were no differences found when both interventions were used for one of the participants. Overall, all participants gained the most benefits from the reciprocal teaching method. (Contains 8 charts.) [Master's Thesis, Kean University.]

The genetics of eight small red squirrel (Sciurus vulgaris L. ) populations in northern Belgium is investigated by analysing variation in a section of the mitochondrial control region and five microsatellite loci. The full sequence of the mitochondrial control region in red squirrels is determined and is compared to that of other mammals. The isolation of microsatellite loci is also described. The eight fragment populations are compared with two large Belgian populations and one large population in the Bavarian Forest, Germany. Virtually no variation is found in the control region within any of the Belgian squirrels, although the German population is found to be highly variable. However, the Belgian and German samples show comparable levels of diversity at the microsatellite loci. The lack of variation in the control region of the Belgian squirrels suggests that they have lost variation, due to either selective or demographic pressures. A combination of a bottleneck and metapopulation structuring could lead to reduced diversity levels and explain the observed patterns of variation. The recent effects of habitat fragmentation and population expansion can be seen in the microsatellite data. Three of the fragment populations show evidence of recent bottlenecks or founder events, probably due to the recent colonisation of these areas by squirrels from nearby expanding populations. Estimations of FsT and RsT show that there is some differentiation among the populations, but none of the populations are significantly differentiated from any of the others. There is no correlation between genetic differentiation and geographic distance indicating that migration is influenced by other factors as well as distance. The fragment populations all contain more allelic diversity than would be expected in populations of their size at mutation-drift equilibrium. Migration between the populations appears to be maintaining nuclear variation and counteracting the effects of random genetic drift.

In 1983 the National Commission on Excellence in Education released "A Nation at Risk", which triggered an extended era of school reform culminating in today's accountability movement. In Kentucky the school improvement process, in which principals play an integral part, is based on the "Standards and Indicators for School Improvement" (SISI-with nine standards and 88 indicators overall) and the Scholastic Audit, a measurement tool based thereon. Murphy's (2004) mediated model of instructional leadership recognizes that complex school reform necessitates both direct and indirect skills. The central research question captures the purpose of this study, testing Murphy's model: Based on Scholastic Audits, what are the effects of instructional leadership on Kentucky accountability scores, as mediated by curriculum and instruction? Secondary data from 83 high schools in Kentucky are examined to determine the direct and indirect effect of leadership on student achievement. Descriptive statistics were calculated for nine demographic factors and the composite Academic Index (AI), an accountability measure. Factors for Standard 7 (Leadership), Standard 1 (Curriculum), and Standard 3 (Instruction) were derived from exploratory factor analysis of the 11, 7, and 8 indicators, respectively, for the standards. Cronbach's alpha and inter-scale correlations were also calculated. Simultaneous multiple regressions examined relationships among demographic factors, three standards, and Al. The full mediated effects model was tested with hierarchical regression. The three sets of indicators each produced a single factor solution explaining 45.4%, 52.9%, and 48.2%, respectively of the variance. Cronbach's alpha ranged from 0.837 to 0.873. Standard 7 (Leadership) explained 39%, 40%, and 20%, respectively, of the variance on Curriculum, Instruction, and the AI. Standards 1 and 3 combined explained 40% of the AI. Demographic factors explained 65% of variance on AI; each of the three standards was essentially independent of demographic controls. In final hierarchical model, Leadership added 0.06 to the variance explained in Step 2. Step 3 with Curriculum and Instruction added produced an additional 0.05; all that influence came from Standard 3 (Instruction). The final model had an effect size of 76%, establishing empirical support for Murphy's mediated effects model of instructional leadership for high schools in Kentucky. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]

This research has investigated the potential of emerging GaN power transistors to meet some of the power conversion challenges that are being posed by transport electrification. The switching performance, driving requirements and on-state characteristics of an example high current GaN HEMT are examined practically followed by the development and demonstration of a high-step-down-ratio DC-DC converter that includes a soft-switching capability. The GS66516T 650 V/60 A HEMT from GaN Systems that represents a typical GaN HEMT model, was shown to achieve a turn-on speed of 9.2 A/ns with a current overshoot of 32% and a turn-off speed of 94.7 V/ns with a voltage overshoot of 45%, resulting in a total switching loss of less than 150 μJ at 400 V, 40 A. The significance of the driver selection and parasitic component optimization were highlighted and the ultra-low turn-off loss mechanism of the GaN HEMT was identified. The dynamic on-state resistance of three GaN devices were measured over a range of conditions that are often encountered in converter applications. Significant variations were observed between device types. An increase in dynamic on-state resistance of 20~30% was observed for the GaN Systems device within 3 μs of turn-on after 50 μs of 400 V stress voltage. The dynamic on-state resistance was largely insensitive to temperature but depended on the switching energy. During continuous operation, an increase of 50.4% in average on-state resistance of the GaN Systems device was observed when operating at 400 V, 10 A, 400 kHz and 0.5 duty ratio. The switched-capacitor, step-down DC-DC converter topology was extended to an interleaved configuration, enabling increased output currents, and its performance was evaluated in a 270-28 V, 200 kHz, 1.2 kW prototype, paying particular attention to the switching waveforms. Furthermore, a multi-layer assembly was used to provide compact electrical and thermal connections. The efficiency of 92.6% represented a five percentage point increase over an equivalent silicon design. A soft-switching topology was then developed to control the switching losses and dv/dt levels by adding a small auxiliary circuit. The converter overall efficiency remained similar due to the introduced auxiliary losses but the converter reliability was significantly improved due to the reduced stress in the GaN transistors.

This thesis presents the design and analysis of a control technique for a 70 kW five-phase high-impedance permanent-magnet generator (PMG) system conceived as a more-electric aircraft aero-engine embedded generator technology. The control design must preserve the fault-tolerance properties of the high-impedance machine whilst providing high power quality and DC voltage regulation over the full speed and load operating range. The generator's fault tolerance is given by its magnetically, thermally and electrically isolated high-impedance phases. Thus, to sustain the fault tolerance characteristics, the generator system is treated as five separate subsystems, i.e., per-phase AC to DC voltage converters, current sensors and actuating controlling algorithms. The derived controllers are designed for unity power factor operation, DC bus voltage regulation, power load sharing, and high-speed field weakening operation. Mathematical modelling of the loops and detailed frequency domain controller design is presented. Two time-domain simulation models and a hardware-in-the-loop emulator system are used to validate the controller's effectiveness throughout the entire load and speed range of the high-impedance PMG system.

Growing aircraft transportation has brought the convenience for travelling around, as well as increasing benefits to transport related industries and commercial companies. However, this also has brought more greenhouse gas emission than before, leaving an urgent issue to balance between benefits and pollutions in the aircraft transport sector. More electric aircraft systems, as a solution for replacing conventional aircraft systems, help to reduce the greenhouse gas emissions, improve energy efficiency and reduce maintenance costs. Multiphase machines in aircraft systems reduce the power per electronic device, reducing its size and cost but with improved system reliability on fault condition and power density. This thesis evaluates the performance of multiphase synchronous machines for a DC power network, where particularly harmonic components and winding configurations for the machine under healthy and fault conditions are studied. The analytical method involved in this thesis is the complex harmonic analysis, which is a frequency domain analysis tool for machine design, considers how the harmonic components change with different machine geometry and winding configurations in order to improve the machine performance. The experimental and finite element validation for the complex harmonic analysis are conducted in this thesis to illustrate the limit of the complex harmonic analysis together with some improvements for this method to account a better fit for the machine modelling. The complex harmonic analysis has been extended with novel work addressing saliency modelling, representation of saturation and evaluation of DQ modelling. There is also new work in the end winding leakage calculations. This thesis also presents an example of the complex harmonic analysis applied to a reconfigurable fifteen phase generator-rectifier system with different layouts to maximise the performance and fault tolerance. Specifically, the 15-phase, three sets of 5-phase and five sets of 3-phase along with series or parallel stacked diode rectifier sets are considered. Although this thesis is focused on a specific machine, the conclusions drawn from steady state healthy and fault performance are generalised for other winding configurations, for example, the presence of zero-sequence current and lowered winding factor in short-pitched windings leads to lower peak power capability and the parallel path in parallel stacked diode rectifier sets leads to severe interference between healthy and faulted subsets.

In 1983 the National Commission on Excellence in Education released A Nation at Risk, which triggered an extended era of school reform culminating in today's accountability movement. In Kentucky the school improvement process, in which principals play an integral part, is based on the Standards and Indicators for School Improvement (SISI--with nine standards and 88 indicators overall) and the Scholastic Audit, a measurement tool based thereon. Murphy's (2004) mediated model of instructional leadership recognizes that complex school reform necessitates both direct and indirect skills. The central research question captures the purpose of this study, testing Murphy's model: Based on Scholastic Audits, what are the effects of instructional leadership on Kentucky accountability scores, as mediated by curriculum and instruction? Secondary data from 83 high schools in Kentucky are examined to determine the direct and indirect effect of leadership on student achievement. Descriptive statistics were calculated for nine demographic factors and the composite Academic Index (AI), an accountability measure. Factors for Standard 7 (Leadership), Standard 1 (Curriculum), and Standard 3 (Instruction) were derived from exploratory factor analysis of the 11, 7, and 8 indicators, respectively, for the standards. Cronbach's alpha and inter-scale correlations were also calculated. Simultaneous multiple regressions examined relationships among demographic factors, three standards, and AI. The full mediated effects model was tested with hierarchical regression. The three sets of indicators each produced a single factor solution explaining 45.4%,52.9%, and 48.2%, respectively of the variance. Cronbach's alpha ranged from .837 to .873. Standard 7 (Leadership) explained 39%, 40%, and 20%, respectively, of the variance on Curriculum, Instruction, and the AI. Standards 1 and 3 combined explained 40% of the AI. Demographic factors explained 65% of variance on AI; each of the three standards was essentially independent of demographic controls. In final hierarchical model, Leadership added .06 to the variance explained in Step 2. Step 3 with Curriculum and Instruction added produced an additional.05; all that influence came from Standard 3 (Instruction). The final model had an effect size of 76%, establishing empirical support for Murphy's mediated effects model of instructional leadership for high schools in Kentucky.

Circuit level analytical models are developed for rapid and accurate evaluation of hard-switching, soft-switching, and dv/dt-induced false turn events of Silicon Carbide (SiC) MOSFETs using only datasheet parameters. The models include the high-frequency parasitic components in the circuit and incorporate the nonlinearities in the junction capacitances of the devices by fitting their nonlinear capacitance curves to a simple equation. The analytical models were solved numerically using MATLAB and the results showed a very good match with the experiments and LTspice simulations. The proposed models were more accurate than LTspice models in predicting the switching losses and required one third of the computation time. The analytical models are evaluated at 25 °C and 125 °C and their experimental validation is described. The model is extended to include the reverse recovery effect of a SiC MOSFET body diode to investigate the dynamic performance of the body diode in hard-switching operation. The dv/dt-induced false turn-on conditions of the SiC MOSFET are predicted analytically and validated experimentally. It was observed that consideration of nonlinearities in the junction capacitances ensures accurate prediction of false turn on. The soft-switching waveforms were also compared with the hard-switching ones both analytically and experimentally to illustrate the advantages of soft-switching in practical converter applications. It was found that soft-switching can significantly reduce the switching losses and could enable higher operating switching frequency for SiC MOSFETs. Two soft-switching DC-DC boost topologies are investigated to extend the switching frequencies of 1200 V, 100 A SiC MOSFET modules beyond the state-of-the-art, 75 kHz. Auxiliary circuits are introduced to the switching legs of the dual-interleaved boost converter to ensure snubber assisted zero voltage zero current (SAZZ) switching of all the semiconductor devices. In the conventional SAZZ topology each auxiliary circuit contains a snubber capacitor, a SiC MOSFET, a SiC Schottky diode and an auxiliary inductance. The auxiliary inductance is replaced by a pulse transformer and a Schottky diode in the modified SAZZ topology. In both topologies, the snubber capacitors and output capacitances of the main devices are discharged prior to turn on by resonating with the auxiliary inductance, eliminating turn on losses. Furthermore, the turn off losses are significantly reduced since the energy stored in the device output capacitance at turn off is recovered at turn on. The design equations are derived and the timing requirements for the soft-switching operation are established for both topologies. A SiC prototype of the conventional SAZZ topology operated at 12.6 kW, 112 kHz, 170-400 V, reducing the switching losses by 57% compared with hard-switching. However, the soft-switching range of the converter was limited to duty ratios above 50%. The modified SAZZ topology overcomes the limitation by replacing the auxiliary inductor with a pulse transformer with 1 : 2 turns ratio and ensures soft-switching for all duty ratios. The SiC prototype using the modified SAZZ topology operated at 20 kW, 112 kHz, 320-600 V, reducing the switching losses by 75% compared with the hard-switching operation.

To reduce emissions and maintenance cost, bulky mechanical actuators and systems in aircrafts are expected to be replaced by lightweight electric or hybrid solutions requiring power electronic converters. One requirement is for a DC-AC converter to synthesize an AC source to power some of the AC loads, and the power density of this converter would be a key design criterion. The main objective of this research is to investigate techniques to improve the power density of this converter, such as through improved design techniques and the use of new wide band-gap semiconductor technologies. It may also be possible to apply these innovations to other DC-AC converters requiring high performance. The thesis identifies the semiconductor losses and the weight of the AC filter as two key design aspects that significantly affect the power density of DC-AC converters. Further reductions in filter weight are hindered by the switching capability of traditional Si semiconductor devices. However new wide band-gap devices such as SiC have lower losses and are capable of switching at high frequencies, making them a candidate technology for applications targeting power density. Firstly, the operation and the loss mechanisms of three widely used DC-AC converter topologies are analysed, which quantifies the reduction in semiconductor losses using SiC devices. Then analytical loss models for three converter topologies are derived, and after applying device datasheet values in the loss models, the SiC two-level converter has been identified as the most suitable converter. The SiC two-level converter gives a 3 % increase in efficiency at a switching frequency of 50 kHz, compared to the same topology switched at 20 kHz with Si IGBTs. Secondly, design constraints for the filter are identified and incorporated into a set of equations that allow calculation of a minimum weight LC filter. Thirdly, models developed for the LC filter are extended to the LCLC filter and the interleaved LCLC filter, which results in a 70 % reduction in filter weight compared to the LC filter. Finally a 10 kW, 100 A single-phase prototype using SiC devices is constructed to demonstrate and validate the analysis and the design methods. The converter achieved a gravimetric power density of 2.9 kW/kg and a volumetric power density 5.3 kW/litre with an efficiency of 95.1 % at 10 kW.

The increasing electrical load demand on on-board (aircraft, marine, automotive, commercial vehicles and rail) power networks, together with the proposed embedded electrical generators introduces new challenges including the potential for engine-generator-electrical system interactions. Accurately emulating such systems is essential to enable the identification and mitigation of such interactions to ensure reliable, robust operation. In this thesis, an advanced emulation method which cancels the natural drive system dynamics using system identification is proposed, designed, simulated and demonstrated experimentally to show its performance in emulating a wide range of aircraft mechanical systems using a commercial electrical drive system. The thesis firstly examines the performance of the existing emulator system hardware, which consists of an electrical drive, real-time control platform and inline speed and torque sensors, to identify aspects of the drive behaviour which may impose a limit on the range or the accuracy of the systems being emulated. Two features of the experimental data were identified which may compromise the ability of the emulator system to emulate mechanical sources, the first is an 89ms time delay between the reference speed and the measured speed, and the second is the relatively low, 60rad/s, bandwidth of the speed controller with a significant resonant peak at approximately, 40rad/s, which significantly limit the range of frequencies which can successfully be emulated. Existing time delay compensation techniques were analysed and simulated using an experimentally validated simulation model, offering only a modest reduction in time delay. An advanced natural drive system dynamics compensator method is proposed to cancel the speed control loop characteristics and so extend the emulation bandwidth of the electrical drive-based emulator system without the need for any hardware changes or knowledge of the drive system parameters. This compensator is designed by applying parameter system identification to experimental data from the emulator drive system speed step response, and then modified to incorporate the effects of field weakening and load variations. The effectiveness of the proposed emulation approach is demonstrated by simulation and experimental emulation of a wide range of mechanical systems, with a focus on aerospace applications, including gas engine dynamics and the associated mechanical transmission effects due to a compliant drivetrain and backlash effects. The proposed emulation method is not limited to a specific mechanical system model, and is particularly suitable for the emulation of the high-speed and high-power mechanical systems.

The increasing use of electrical technologies within on-board (aircraft, road vehicle, train and ship) power systems is resulting in complex and highly dynamic networks in which energy storage devices have an important role to play, for example to resolve the instantaneous mismatch between load demand and power availability or to provide the flexibility to optimise overall performance. In this thesis, a multi-level controller for a super-capacitor based energy storage system (ESS) is designed, simulated, emulated and validated experimentally to show its effectiveness in smoothing load and managing state-of-charge of the energy storage system. This thesis first investigates the low level control of the dual-interleaved converter, particularly at light load where seven discontinuous conduction modes (DCMs) appear. A thorough analysis of these operating modes is given and validated by simulations and experiments. Based on the analysis, an inverse-model-based feed-forward current controller is implemented, offering a low level converter control interface which serves the high level supervisory controller within the energy storage system. Two supervisory control methods have been proposed in this thesis, both producing a super-capacitor current reference for the low level controller. The first supervisory control not only manages the energy within the ESS but also shields the primary power source from rapid load transients , which has been examined through an emulated ESS in the Intelligent Electrical Power Network Evaluation Facility (IEPNEF). A more advanced supervisory controller is then proposed which in addition to the benefits of the first control, regulates the rate-of-change in power that is drawn from the primary power source in the system. The proposed second control method is implemented within a real super-capacitor energy storage system in IEPNEF, with both simulation and experimental results successfully demonstrating and validating its operation.