Three studies were designed to determine the relation between subcortical neural temporal coding and the perception of musical consonance. Consonance describes the pleasing perception of resolution and stability that occurs when musical notes with simple frequency ratios are combined. Recent work suggests that consonance is likely to be driven by the perception of ‘harmonicity’, i.e. the extent to which the frequency components of the combined spectrum of two or more notes share a common fundamental frequency and therefore resemble a single complex tone (McDermott et al, 2010, Curr Biol). The publication in Chapter 3 is a paper describing a method for measuring the harmonicity of neural phase locking represented by the frequency-following response (FFR). The FFR is a scalp-recorded auditory evoked potential, generated by neural phase locking and named from the characteristic peaks in the waveform with periods corresponding to the frequencies present in the fine structure and envelope of the stimulus. The studies in Chapters 4 and 5 demonstrate that this method predicts individual differences in the perception of consonance in young normal-hearing listeners, both with and without musical experience. The results of the study in Chapter 4 also demonstrate that phase locking to distortion products resulting from monaural cochlear interactions which enhance the harmonicity of the FFR may also increase the perceived pleasantness of consonant combinations of notes. The results of the study in Chapter 5 suggest that the FFR to two-note chords consisting of frequencies below 2500 Hz is likely to be generated in part by a basal region of the cochlea tuned to above this frequency range. The results of this study also demonstrate that the effects of high-frequency masking noise can be accounted for by a model of a saturating inner hair-cell receptor potential. Finally, the study in Chapter 6 demonstrates that age is related to a decline in the distinction between the representation of the harmonicity of consonant and dissonant dyads in the FFR, concurrent with a decline in the perceptual distinction between the pleasantness of consonant and dissonant dyads. Overall the results of the studies in this thesis provide evidence that consonance perception can be explained in part by subcortical neural temporal coding, and that age-related declines in temporal coding may underlie a decline in the perception of consonance.

This dissertation describes the effect that the construction of frequency tables has on basic statistics computed from those frequency tables. It is directly applicable only to normally distributed data summarized by Sturges' Rule. The purpose of this research was to identify factors tending to bias sample statistics when data are summarized, and thus to allow researchers to avoid such bias. The methodology employed was a large scale simulation where 1000 replications of samples of size n = 2 ᵏ⁻¹ for 2 to 12 were drawn from a normally distributed population with a mean of zero and a standard deviation of one. A FORTRAN IV source listing is included. The report concludes that researchers should avoid the use of statistics computed from frequency tables in cases where raw data are available. Where the use of such statistics is unavoidable, the researchers can eliminate their bias by the use of empirical correction factors provided in the paper. Further research is suggested to determine the effect of summarization of data drawn from various non-normal distributions.

Power amplifiers (PA) are typically the most power-consuming building blocks of RF transceivers. Therefore, the design of a high-efficiency radio frequency power amplifier is the most obvious solution to overcoming the battery lifetime limitation in the portable communication systems. A power amplifier's classes (A, AB, B, C, F, E, etc), and design techniques (Load-pull and large-signal S-parameters techniques) are presented. The design accuracy of class-A power amplifier based on the small-signal S-parameters was investigated, where compression in the power gain was used as an indicator for design accuracy. The effect of drain voltage variation on the power gain compression has been studied in this research. The class-E amplifier has a maximum theoretical efficiency of 100%. It consists of a single transistor that is driven as a switch and a passive load network. The passive load network is designed to minimize drain (collector) voltage and current waveforms overlapping, which minimize the output power dissipation. Two L-band class-E amplifiers are implemented in section 5.3. One of them is a lumped elements based circuit and the other is a transmission lines based circuit. Both circuits show good performance (60% PAD) over a wide bandwidth (1.0 GHz). In section 5.4, lumped elements and transmission lines based X-band class-E amplifiers are presented. Both circuits show good performance (62% PAD) over wide bandwidth (4.8 GHz). A new technique to improve the drain efficiency of the class-E amplifier has been proposed. This technique uses two passive networks. One of them is in a series with the shunt capacitor CS and the other is in a series with the transistor's source terminal. This technique shows improvement in the drain efficiency, which jumps from 62% to 82%. Last few years have seen an increase in the popularity of the wireless communication systems. As a result, the demand for compact, low-cost, and low power portable (Single-chip) transceivers has increased dramatically. Among the transceiver's building blocks is the power amplifier. Thus, there is a need for a low-cost power amplifier. A 900 MHz CMOS RF PA with one-watt output power and a high power added efficiency (68%) is presented in chapter 6. This PA can be used in the European standard for mobile communications (GSM) handset transmitter. / Ph. D.

Hybrid actuation is an expanding field in which several systems, such as a mechanical, electrical, hydraulic, pneumatic, and/or thermal, among others, are integrated in order to combine certain aspects of each system, and achieve a better and more efficient performance under certain operating conditions. The concept of piezohydraulic actuation takes advantage of the high force capabilities that piezoceramics have and combines it with the operation at high frequencies, in order to achieve the hydraulic actuation of a system under a specified stroke and force. High frequency rectification translates the low stroke of a piezoelectric stack into a desired amount of stroke per unit time. Thus, the low displacement, oscillatory motion of the piezoelectric device (coupled with a high frequency operation) is translated into a unidirectional motion of a hydraulic cylinder. As part of this research, a benchtop piezohydraulic unit has been developed and the concept of piezohydraulic actuation has been demonstrated. The effective bidirectional displacement of a hydraulic cylinder through the actuation of a piezoelectric stack has been achieved. A lumped parameter model is developed in order to simulate the dynamics of the hydraulic system and of the entire piezohydraulic unit. The model did approximate the response of the piezohydraulic unit under a one-sided operation. Time response analysis is performed through the frequency spectrum comparison of the measured and the simulated data. Then a two-stage cycle simulation is used to model the pumping operation of the unit. Discrepancies were obtained between the model and the actual system for the single-ended piezohydraulic unit, nonetheless, a good approximation has been achieved for the pumping operation of the double-ended unit under certain conditions. Furthermore, several factors have been identified that may limit the operation of the piezohydraulic unit. First, the need of high displacement actuators often comes with the requirement of high voltage operation along with high current consumptions. Thus, the amplifier becomes the first limitation to overcome. Second, is the response of the controlled valves. The highest valve operating frequency and their time response will set the limit on the piezohydraulic unit. And finally, once these limitations are overcome, the unit is eventually limited by the dynamics of the fluid and the hydraulic system itself. Attenuation in the frequency response, or the operation near resonance and the possibility of cavitation, are some of the aspects that eventually will limit the operation of the piezohydraulic unit. A custom made, high displacement stack is used along with a custom made switching amplifier. The current system is being limited by the second factor, the solenoid valves. Nonethelss the analysis performed has addresed the relevant issues required for the design and use of another set of controlled valves. Finally, the eventual limitation from the hydraulic system has been determined through the analysis of the fluid dynamics of the system. The analysis does not account for potential cavitation, and future operations at high frequencies should take it into account. / Master of Science

Behavioral contrast has been interpreted as a function of either (1) the reduction of frequency of reinforcement in one component of a multiple schedule or (2) the suppression of responses in one component regardless of reinforcement frequency. These explanations are discussed in terms of their adequacy in accounting for several recent experimental results. Two alternative explanations are considered. First, contrast is interpreted as a function of the relative summation of excitatory and inhibitory effects of stimuli. Second, contrast is discussed as a possible function of a switch from a response-reinforcer contingency to a stimulus-reinforcer contingency as seen in auto-pecking. Both avenues are considered promising in terms of accounting for behavioral contrast.

No description available.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, February 6, 2015. / We explore indirect detections of Dark Matter, focusing on deep radio observations of six dwarf spheroidal galaxies (dSph), Carina, Fornax, BootesII, Hercules, Segue2, Sculptor. We discuss the WIMP Dark Matter particle annihilation process and describe brie y the particles produced in this process. We consider the emissions, which can result from electrons and positrons produced. We describe why dSph are the best observational targets for indirect Dark Matter detection at radio frequencies. We describe the theoretical framework for predicting Dark Matter synchrotron emissions and make some predictions for the six dSph of interest to us. We discuss ATCA observations of these dSph and explore the background source subtraction process in detail. We obtain an upper limit on the WIMP mass and compare our results to various other experiments. We discuss prospects for this work towards attaining an indirect Dark Matter detection.

Waterfowl hunting is important historically, culturally, and economically in Mississippi and North America. I evaluated effect of hunting frequency (2 or 4 days/week) on duck abundance, harvest, and hunters’ perceived quality of their experience on Mississippi Wildlife Management Areas (WMAs). Neither relative abundance nor harvest of all ducks, mallard (Anas platyrhynchos), northern shoveler (A. clypeata), or green-winged teal (A. crecca) differed between experimental hunting frequencies. Duck harvest increased with hours spent afield. Hunters’ perceived quality did not differ between hunting frequencies but was greatest when hunters harvested > 4 ducks/ day and increased with harvest of larger sized ducks. I suggest WMAs may be hunted 4 days/week without impacting duck abundance, harvest, or hunt quality. I recommend continued evaluations of hunting frequency on duck abundance, harvest, and hunt quality to sustain science-guided management of waterfowl hunting on Mississippi public lands.

No description available.

No description available.