A comparison of two novel demodulators. The first is a basic zero crossing demodulator, as introduced by Beards. The second is an approach proposed by Hovin. The two demodulators are compared to each other and to the conventional method of demodulation. / Graduation date: 1998

The validity of the dynamic analysis based on simplified plate model was investigated using of FE-codes ANSYS in the present paper. The simplified clamped multi-layered plate model was first verified by comparison with the exact model. The simply supported plate model was confirmed to be not a suitable model due to its large error as comparing with exact model. Influence of dimensions of laminar diaphragm on nature frequencies was studied. Deflection and voltage response driven by mechanical and electric loads were described. The optimized thickness ratio of PZT layer to SiO₂ and Si layers was given in the paper to obtain the best deflection export of actuator in design. / Singapore-MIT Alliance (SMA)

by W.G. Tuller and T.P. Cheatham, Jr. / "June 30, 1946." / Includes bibliographical references. / Contract OEMsr-262

by W.G. Tuller. / "March 8, 1946." "NDRC Division 14." / Army Signal Corps Contract No. W-36-039 sc-32037. Contract OEMsr-262.

Thesis (Ph. D.)--Ohio State University, 2006. / Full text release at OhioLINK's ETD Center delayed at author's request

Not available

Anthropogenic noise is increasingly widespread as human development continues. Noise can negatively affect humans and wildlife, but the most deleterious effects are incurred by species that rely on vocal communication for mating, territory defence, and other vital functions. Songbirds are particularly susceptible, often experiencing declines in richness and abundance in noise-affected areas. Yet, some species remain abundant in noisy environments. High frequency vocalizations, or the ability to shift to higher frequencies, is one adaptation that may allow birds to communicate above low frequency anthropogenic noise. However, the mechanisms underlying frequency shifting, and the relationship between vocal frequency and abundance, are still not fully understood. I examined whether black-capped chickadees produce songs at higher frequencies in noisy areas, and whether these differences could be due to altered vegetative structure rather than noise. I also examined whether chickadees could plastically change song frequencies as noise increased. Finally, I surveyed abundance and recorded vocalizations from several songbird species to evaluate whether plasticity in song frequency, or mean song frequency, could predict how abundance and urban prevalence would be affected by anthropogenic noise. I found that black-capped chickadees shifted to higher song frequencies in noise-affected areas, and that vegetative differences did not account for these changes. Further, chickadees at roadside locations plastically increased their song frequencies as noise levels increased. Vocal plasticity, however, was not related to abundance in my multi-species comparison. Instead, noise-related changes in abundance were predicted by a species minimum song frequency. Nevertheless, minimum song frequency did not necessarily predict whether a species would be widespread in urban areas. In addition to frequency parameters, urban species may avoid overlap with noise through spatial and temporal mechanisms, but those that lack any mechanisms to communicate within anthropogenic noise may experience declines. Thus, reducing anthropogenic noise may increase the quality of urban habitats for birds. / Ecology

Otoacoustic emissions (OAEs) have been under investigation since their discovery 30 years ago (Kemp, 1978). Otoacoustic emissions are quiet sounds generated within the cochlea that can be detected with a sensitive microphone placed within the ear canal. They are used clinically as a hearing screening tool but have the potential for diagnostic and monitoring purposes. For this dissertation, high-resolution instrumentation was developed for improving the acquisition of OAEs. It was shown that a high bit-depth device is required in order to simultaneously characterize the ear canal and the cochlear responses. This led to a reduction in the stimulus artifact that revealed early latency, high-frequency otoacoustic emissions. Next, a swept-tone technique originally developed for use in acoustical systems was formally developed for use in the human ear. The swept-tone technique allows for the simultaneous acquisition of a system's impulse response and its distortion components. The swept-tone was first used in this study to characterize the ear canal transfer properties. From that transfer function, a compensation routine was developed which equalized the magnitude and phase distortions of the ear canal. As a result, an improved acoustical click could be presented to the ear, which allowed for further reduction of the stimulus artifact, revealing early latency emissions. Spectral flatness and effective duration measurements of the compensated click showed an improvement over traditional click stimuli. Furthermore, wavelet analysis and time-frequency latency computations showed that higher frequency otoacoustic emissions were recoverable when using a compensated click stimulus. The swept-tone technique was then utilized for the direct acquisition of otoacoustic emissions. The swept-tone response was compressed to an impulse response and compared to a standard click response. It was found that several similarities exist between the two response types. The divergences, primarily in the low-frequencies, have implications in the generation mechanisms involved in a click-evoked otoacoustic emission. The swept-tone response provided some clinical benefits, namely in an improved signal-to-noise ratio, and in the removal of obstructive synchronized spontaneous OAEs when compared to a standard click response. Current methods are restricted by noise contamination, and the use of a swept-tone technique can reduce the acquisition time by up to a factor of four, compared to standard click methods. These implications and future potential studies are discussed.

Thesis (Ph. D.)--University of Texas at Dallas, 2006. / Includes vita. Includes bibliographical references (leaves 253-256).

In this thesis, hidden Markov model, maximum likelihood ratio and lexicon search strategy are used to establish a Chinese resume inputting system. The resume contains five items: name introduction, gender, birth date, birth place and education. This system is developed using a PC with an Intel Pentium 1.6 GHz CPU and Red Hat Linux 9.0 operating system. For the speaker-dependent case, a resume can be completed within 45 seconds on the average.