The Australian wheat production environments are typically water-limited, and both temperature and vapour pressure deficit increase as the season progresses. As a result, high incidences of small or shriveled wheat kernels (screenings) are commonly generated and can substantially reduce grain value. Previous studies suggest the incorporation of the tiller inhibition (tin) gene can reduce the production of infertile tillers and increase kernel weight (KW). It was hypothesised that the incorporation of the tin gene into wheat germplasm may a) contribute to the maintenance of large KW and reduction in screenings (SCR) in terminal water deficit environments; and b) not be associated with a grain yield (GY) penalty in terminal water deficit environments. Thus, the major objective of this thesis was to evaluate the expression and performance of tin gene in terms of GY and SCR: 1) in different genetic backgrounds and across Australian production environments; 2) in various northern production environments which are particularly prone to terminal water deficit conditions; and 3) to determine the mechanisms that contribute to the maintenance of large KW of tin lines in terminal stress conditions. To address the overall objective, populations of lines were genotyped for the presence/absence of the tin gene and were field tested. Line differences in GY, yield components, SCR and general growth and development attributes were determined in 22 field experiments conducted between 2005-2007. The experiments were grouped into those that evaluated: a large number of sister lines from four genetic backgrounds in multi-location experiments; selected lines from Silverstar population in multi-location experiments; and selected sister lines in detailed agronomic experiments examining the effect of plant density and controlled levels of water supply through the use of a rainout shelter facility. The effect of tin on GY and SCR varied with environment and genetic background. In the Brookton, Wyalkatchem and Chara background, there was no reduction in GY associated with tin in southern production environments. However, a 31% and 10%, advantage of free-tillering over reduced tillering Silverstar lines existed in the 2005 western and 2006 northern experiments respectively, and led to an average 12% reduction in GY of Silverstar tin lines. In northern experiments, tin lines in a Silverstar background produced up to 50% fewer SCR than Silverstar free-tillering lines. Averaged across experiments, KW of Silverstar tin lines was 10% greater than free-tillering lines. Based on stem number per plant, Silverstar lines were classified into three groups; the restricted (R) and semi-restricted (SR) tin and free-tillering lines attained 2.9, 3.4 and 4.8 stems per plant respectively. Expression of tin in terms of maximum stem number production was genetic background and genotype dependent, and unlike free-tillering lines, R tin lines in particular, were not as responsive to plant density. Head number per unit area rather than kernel number per head was strongly associated with KW determination. Therefore, to maximize KW under water limiting conditions it is more beneficial if high kernel number can be achieved via the production of low head number with more kernels per head, as can be achieved with the use of tin lines. The KW advantage of Silverstar R tin was associated with greater anthesis total dry matter, stem water soluble carbohydrate and nitrogen available per head relative to free-tillering lines, and thus R tin lines had more assimilate for translocation during the grain filling period. In a terminal water deficit experiment, individual KW data collected for Silverstar tin and free-tillering lines revealed that KW of tin lines (≈ 25 mg per kernel) was maintained for main stem to fourth tiller heads and across floret positions 1-4 within spikelets. In contrast, free-tillering lines (≈ 18 mg per kernel) generated small kernels across the entire plant, with the largest proportion originating from floret positions 3 and 4. Lines containing the tin gene had a greater mean KW and kernel width, and a higher frequency of wider kernels than free-tillering lines. The high frequency of large kernel widths was associated with significantly less SCR in tin lines. A strong positive association between maturity head number per plant and SCR indicated, for every fertile head produced, SCR increased by 11% in the terminal water deficit experiment. Reduction in SCR in the Silverstar tin material in the north, was associated with high KW and a tendency for lower GY, although tin lines with equivalent GY to Silverstar could be identified in each environment. The incorporation of the tin gene has the potential to significantly reduce the incidence of SCR in commercial wheat crops. The reduction in GY associated with the tin gene was dependent on genetic background, suggesting the potential for selection of higher-yielding tin progeny in commercial line development. However, a tailored agronomic package to optimize yield potential of tin lines needs to be developed for different target environments. With the incorporation of the tin gene into genetic material adapted to the northern wheat belt and optimisation of head density, there exists scope for simultaneous improvements in GY and KW and subsequent reduction in SCR for terminal water deficit environments.

<p>In this thesis a predefined design parameters are used to present theoretical guidelines for design of low voltage, and low power DC-DC converter with high power efficiency and low levels of EMI (Electro-Magnetic Interference). This converter is used to alter the DC voltage supplied by the power source. Several DC-DC converters of different types and topologies are described and analyzed. Switched converter of buck topology is found to satisfy the design criteria most adequately and therefore is chosen as the solution for the task of the thesis. Three control schemes are analysed PWM (Pulse-Width Modulation), PFM (Phase-Frequency Modulation), and Sliding control. PWM is found to be most appropriate for implementation with this type of converter. Further, basic operation of the buck converter which includes two modes of operation CCM (Continuous-Conduction Mode) and DCM (Discontinuous-Conduction Mode) is described. Power losses associated with it are analysed as well. Finally several techniques for power conversion improvement are presented.</p>

<p>With an increasing number of transistors integrated on a single die, the need for global on-chip interconnectivity is growing. Long interconnects, in turn, have very large capacitances which consume a large share of a chip’s total power budget.</p><p>Power consumption can be lowered in several ways, mainly by reduction of switching activity, reduction of total capacitance and by using low voltage swing. In this project, the issue is addressed by proposing a new encoding based on Pulse Width Modulation (PWM). The implementation of this encoding will both lower the switching activity and decrease the capacitance between nearby wires. Hence, the total effective capacitance will be reduced considerably. Schematic level implementation of a robust transmitter and receiver circuit was carried out in CMOS090, designed for speeds up to 100 MHz. On a 10 mm wire, this implementation would give a 40% decrease in power dissipation compared to a parallel bus having the same metal footprint. The proposed encoding can be efficiently applied for global interconnects in sub-micron systems-on-chip (SoC).</p>

This thesis focuses particularly on the application of chemometrics in the field of analytical chemistry. Chemometrics (or multivariate analysis) consists in finding a relationship between two groups of variables, often called dependent and independent variables. In infrared spectroscopy for instance, chemometrics consists in the prediction of a quantitative variable (the obtention of which is delicate, requiring a chemical analysis and a qualified operator), such as the concentration of a component present in the studied product from spectral data measured on various wavelengths or wavenumbers (several hundreds, even several thousands). In this research we propose a methodology in the field of chemometrics to handle the chemical data (spectrophotometric data) which are often in high dimension. To handle these data, we first propose a new incremental method (step-by-step) for the selection of spectral data using linear and non-linear regression based on the combination of three principles: linear or non-linear regression, incremental procedure for the variable selection, and use of a validation set. This procedure allows on one hand to benefit from the advantages of non-linear methods to predict chemical data (there is often a non-linear relationship between dependent and independent variables), and on the other hand to avoid the overfitting phenomenon, one of the most crucial problems encountered with non-linear models. Secondly, we propose to improve the previous method by a judicious choice of the first selected variable, which has a very important influence on the final performances of the prediction. The idea is to use a measure of the mutual information between the independent and dependent variables to select the first one; then the previous incremental method (step-by-step) is used to select the next variables. The variable selected by mutual information can have a good interpretation from the spectrochemical point of view, and does not depend on the data distribution in the training and validation sets. On the contrary, the traditional chemometric linear methods such as PCR or PLSR produce new variables which do not have any interpretation from the spectrochemical point of view. Four real-life datasets (wine, orange juice, milk powder and apples) are presented in order to show the efficiency and advantages of both proposed procedures compared to the traditional chemometric linear methods often used, such as MLR, PCR and PLSR.

A multilevel Space Vector PWM (SVPWM) technique is developed for a 3-level 3-phase PWM Voltage Source Inverter using a 3-phase coupled inductor to ensure high performance operation. The selection of a suitable PWM switching scheme for the Coupled Inductor Inverter (CII) topology should be based on the dual requirements for a high-quality multilevel PWM output voltage together with the need to minimize high frequency currents and associated losses in the coupled inductor and the inverter switches. Compared to carrier-based multilevel PWM schemes, the space vector techniques provide a wider variety of choices of the available switching states and sequences. The precise identification of pulse placements in the SVPWM method is used to improve the CII performance. The successful operation of the CII topology over the full modulation range relies on selecting switching states where the coupled inductor presents a low winding current ripple and a high effective inductance between the upper and lower switches in each inverter leg. In addition to these requirements, the CII operation is affected by the imbalance inductor common mode dc current. When used efficiently, SVPWM allows for an appropriate balance between the need to properly manage the inductor winding currents and to achieve harmonic performance gains. A number of SVPWM strategies are developed, and suitable switching states are selected for these methods. Employing the interleaved PWM technique by using overlapping switching states, the interleaved Discontinuous SVPWM (DSVPWM) method, compared to other proposed SVPWM methods, doubles the effective switching frequency of the inverter outputs and, as a result, offers superior performance for the CII topology by reducing the inductor losses and switching losses. The inverter operation is examined by means of simulation and experimental testing. The experimental performance comparison is obtained for different PWM switching patterns. The inverter performance is affected by high-frequency inductor current ripple; the excessive inductor losses are reduced by the DSVPWM method. Additional experimental test results are carried out to obtain the inverter performance as a variable frequency drive when operated in steady-state and during transient conditions. The CII topology is shown to have great potential for variable speed drives. / Power Engineering and Power Electronics

Switching mode DC/DC converters are critical building blocks in portable devices and hence their power efficiency, accuracy and cost are a major issue. The primary focus of this thesis is to address these critical issues.This thesis focuses on the different methods of feedback control loop which are employed in the switching mode DC/DC converters such as voltage mode control and current mode control. It also discusses about the structure of buck converter and tries to find an efficient solution for stepping-down the DC voltage level in ultra-low power applications. Based on this analysis, a 20 MHz voltage mode DC/DC buck converter with an on-chip compensated error amplifier in 65 nm CMOS process is designed and implemented.The power efficiency has been improved by sizing the power switches to have a low parasitic output and gate capacitances to reduce the capacitive and gate-drive losses. Also the error amplifier biasing current is chosen a small value (12.5 μA) to reduce the power dissipations in the control loop of the system. The maximum 84% power efficiency is achieved at 1.1 V to 500 mV conversion, above 81% efficiency can be achieved at load current from 0.5 mA to 1.26 mA. Due to wide bandwidth error amplifier and proper compensation network the fast transient response with settling time around 45 μs is achieved.

No description available.

In this thesis a predefined design parameters are used to present theoretical guidelines for design of low voltage, and low power DC-DC converter with high power efficiency and low levels of EMI (Electro-Magnetic Interference). This converter is used to alter the DC voltage supplied by the power source. Several DC-DC converters of different types and topologies are described and analyzed. Switched converter of buck topology is found to satisfy the design criteria most adequately and therefore is chosen as the solution for the task of the thesis. Three control schemes are analysed PWM (Pulse-Width Modulation), PFM (Phase-Frequency Modulation), and Sliding control. PWM is found to be most appropriate for implementation with this type of converter. Further, basic operation of the buck converter which includes two modes of operation CCM (Continuous-Conduction Mode) and DCM (Discontinuous-Conduction Mode) is described. Power losses associated with it are analysed as well. Finally several techniques for power conversion improvement are presented.

With an increasing number of transistors integrated on a single die, the need for global on-chip interconnectivity is growing. Long interconnects, in turn, have very large capacitances which consume a large share of a chip’s total power budget. Power consumption can be lowered in several ways, mainly by reduction of switching activity, reduction of total capacitance and by using low voltage swing. In this project, the issue is addressed by proposing a new encoding based on Pulse Width Modulation (PWM). The implementation of this encoding will both lower the switching activity and decrease the capacitance between nearby wires. Hence, the total effective capacitance will be reduced considerably. Schematic level implementation of a robust transmitter and receiver circuit was carried out in CMOS090, designed for speeds up to 100 MHz. On a 10 mm wire, this implementation would give a 40% decrease in power dissipation compared to a parallel bus having the same metal footprint. The proposed encoding can be efficiently applied for global interconnects in sub-micron systems-on-chip (SoC).

This thesis proposes a dimming approach with Double Pulse Width Modulation for equalizing the light output of the back light with light emitted diodes (LEDs) for large scale outdoor liquid crystal displays (LCDs). The approach compensates the difference among the LED light bars by adjusting the power outputs of converters according to the feedback of light strength from light sensors. With the proposed Double Pulse Width Modulation method, local brightness adjustment on the light bars can be made to provide a uniform light output and the dimming function for LCD can be retained. Experiments results made on a 46¡¨ LCD with four LED light bars demonstrate that the double pulse-width- modulation can provide uniformly in the light bar output. The experimental results show the proposed Double Pulse Width Modulation (DPWM) method can alleviate the problem from divergence of the light bars and thus can generate more uniform light output on LCDs.