During the thickening process of sludges with intermediate to high solid concentrations three settling regimes are typically encountered, namely, zone, transition, and compression regimes. Recent studies have indicated that the validity of Kynch's formulation, which is the most widely used for sizing settling basins, is limited to the zone settling regime. His formulation is based on the solids mass balance equation and does not consider the role of the rising sediment at the bottom of the settling basin. This limitation is rectified in this study by using a dynamic equation, a second order non - linear partial differential equation for the effective pressure of the solid particles. The equation is solved by using the finite element method. The so obtained effective pressure is used with an appropriate constitutive relation for the volume fraction of solids, to determine the variation of the solids content within the deposited material, and the height of the falling mudline. / Master of Science

Human factors research of automobile driver behavior often calls for timing in-car manual tasks. By measuring the time that a driver directs resources away from the primary task of driving, investigators can determine both if and where improvements need to be made in the driver-vehicle relationship. The present study was designed to compare the accuracy of various techniques for measuring in-car manual task durations. Additionally, this research was intended to reveal how closely these techniques approach the accuracy of the frame-by-frame video analysis method, which is time-consuming and expensive to perform. The study required three male and three female subjects to use an electronic stopwatch to measure "hand-off-wheel" times for 30 driver tasks. Each subject performed this procedure three times: once while sitting as an observer in the back seat of a research vehicle, once while watching a real-time video recording of task performance, and once while watching a one-sixth real-time video recording of task performance. Three independent variables were examined: timing Method (three levels), Duration of in-car task (three levels), and Subject (six levels). Dependent measures gathered were raw timing error (a measure of response bias), absolute timing error (a measure of response accuracy), and squared timing error (a measure of response consistency). Timing error was obtained by subtracting the measured time for a particular task from the "true" task time obtained by using the frame-by-frame video analysis technique. Analysis of the data indicated a significant effect of Method on response bias. Specifically, use of the slow-motion video technique resulted in overestimation of in-car task durations, and use of the two real-time techniques resulted in estimates of task durations that were either equal to or less than the true durations. Significant effects of Subject, Gender, and Subject x Method were also revealed. The results suggest that the on-road timing technique should be used in the future, since this procedure requires little in terms of cost and implementation time, and errors are small when compared with the frame-by-frame technique. Furthermore, it is recommended that only one experimenter serve as a timing analyst during an experiment to ensure a constant level of accuracy. / Master of Science

These studies examined the effects of altered developmental experience (rearing history) and altered behavioral context (testing environment) on the alarm call responsiveness of maternally naive, incubator-reared bobwhite quail chicks. Experiment 1 assessed alarm call responsiveness in socially-reared, socially-tested hatchlings across the first 96 hours following hatch. No significant age effects were revealed. Hatchlings tested at 24 hours did not differ significantly from birds tested at 48, 72, or 96 hours on the two principle behavioral measures (number of grid crossings and vocalizations per one-minute trials). Experiment 2 assessed whether hatchlings' alarm call responsiveness is at least partially dependent on the availability of cover (i.e., hiding sites) in the testing situation. No significant differences in responding were found in comparisons between hiding sites and social (non-hiding sites) testing conditions. However, behavioral observations did indicate that hatchlings in the hiding site condition utilized the hiding site as an attractor, in that chicks typically huddled and froze around the hiding site structure. Experiment 3 examined the relative effects of individual testing on socially-reared bobwhite quail hatchlings. Results revealed that individually tested hatchlings increased their locomotor activity following initial exposure to the maternal alarm call when compared to socially tested chicks. Vocalizations were significantly reduced in post-alarm call testing from pre-alarm call levels. However, hatchlings tested individually had higher levels of vocal activity when compared to socially tested chicks. In comparison with socially-reared/socially-tested subjects, socially-reared/individually tested subjects were more active following exposure to the maternal alarm call than they were prior to exposure to the call. Results from the three experiments are discussed in terms of species-typical experience and development. It is maintained that species-typical responding to the bobwhite maternal alarm call is partially influenced by social context. An argument for continued polythetic research on behavioral development in avian communication is also made. / Master of Science

A laser Doppler Anemometer (LDA) is used to make Reynolds stress measurements in a fully developed, turbulent pipe flow. Traverses are made to measure shear stress, normal stresses, and the correlation coefficient. To assess the accuracy of this system, these measurements are compared with results from other published investigations. The differences between the published reports are discussed to emphasize how much turbulence measurements can vary, even in a well-studied flow. Descriptions are included about LDA theory and turbulence measurement techniques. The techniques discussed include the selection of proper sampling rate, the reduction of statistical bias, the choice of amplification, and optimization practices. / Master of Science

Currently, there is a significant increase in oceanic air traffic. The Federal Aviation Administration (FAA) is attempting to keep pace with this traffic. Automation is being planned in the airline and Air Traffic Control (ATC) system; eventually, all oceanic functions will be part of the FAA Advanced Automation System (AAS). The Oceanic Display and Planning System (ODAPS) capabilities include oceanic flight data processing, conflict probe, flight strip printing; and aircraft situation display capabilities. The Fight Data Input/Output (FDIO) device is currently being used as the main controller input device to the ODAPS. The objective of the Oceanic Air Traffic Control System (OATCS) is to replace the FDIO device with a system that will provide more flexibility and assistance to the oceanic air traffic controller in interfacing with the ODAPS The OA TCS being proposed by this research and thesis is an interim system in support of planned automation. The OATCS will provide the controller with the ability to scroll, and search through previous received ODAPS update, alert, and response messages, and to compose and edit ODAPS flight plan messages. The OATCs will augment and enhance the current functionality of the FDIO system of the ODAPS by providing high technology workstations similar to AAS. The OATCS also will provide the capability to process Automatic Depending Surveillance (ADS) position reports by replacing ODAPS peripherals to improve the working environment for oceanic controllers, the ARINC Communication Center, and the pilot. In addition, the OATCS will support a future two way data link between the oceanic controller and the pilot. / Master of Science

This document explains the design of the Acoustic Emission Detection and Characterization System (AEDCS). The AEDCS is capable of recording several Acoustic Emmision ( E) characteristics including AE event peak amplitude, duration, frequency, and time of occurrence. The analog and digital circuits designed to implement these functions are monitored and controlled by a microprocessor system. The microprocessor system processes and records the AE event information, and passes it to a host computer for mass storage and further manipulation. The AEDCS is the first low cost, self-contained device that records these AE characteristics in real time. The AEDCS is designed to be used in the AE testing of materials. It is well-suited for non-destructive applications that produce a relatively low AE count rate, such as AE monitoring of wooden structures. The AEDCS is also capable of recording AE event characteristics in destructive test applications. The results of using the AEDCS in a mechanical loading test application on several different types of wood are given here as well. / Master of Science

This thesis consists of a personal exploration of the concepts of "identification" and "alienation" as they relate to one's relationship to the physical world. :Identification" as defined by Christian Norberg Schultz refers to the quality of the relationship between human beings and their environments. (p.21) "Alienation" on the other hand refers to a manner of existence where identification does not take place, and implies an unnatural separation between ones psychic and physical experiences (p.168) The argument is made that the experiences inherent in identification are fundamental to the quality of life and that the increasing sense of alienation within "modem society" has left many people feeling lost. This suggests that it is becoming increasingly more important that we find a means to redefine the concept of identification so that it has the capacity to meet our need today. The second half of the thesis is devoted to a series of design explorations. In creating the sculptures and landscapes illustrated I sought an increased conscious understanding of <u>my</u> processes of identification. It is my hope that the documentation of my experiences will serve as a tools for the reader, not to predict what their experiences would or should be, but rather as a guide to a better understanding of the possibilities that can exist within the relationship between all human beings and their environments. / Master of Landscape Architecture

This document describes the theory, design and implementation of a digital receiver designed for the ACTS propagation experiments. The Virginia Tech Satellite Communications Group is designing, constructing and distributing eight ACTS propagation terminals (APTs) under a contract with NASA. The terminals will measure the received signal power from the ACTS satellite beacons (20 GHz, 27.5 GHz) in various climates at different elevation angles. The resulting signal power measurement, radiometer and weather measurement data will be used to characterize atmospheric effects on signal propagation at Ka band. Each APT system will contain two identical, independent digital receivers; one 20 GHz channel and one 27.5 GHz channel. The algorithm implemented on each receiver utilizes the results of multiple fast Fourier transforms to reliably identify the carrier tone amidst neighboring modulation tones. The acquisition procedure, can reliably identify the carrier signal at signal-to-noise ratios down to 10 dB in a 20 Hz bandwidth (23 dBHz in a 1 Hz bandwidth, -26 dB relative to clear air conditions on the APT system) in 2 seconds. The receiver then uses a comb filter, two FIR filters and additional FFTs to produce power measurements accurate to 0.1 dB at signal-to-noise ratios down to 5 dB in a 20 Hz bandwidth (18 dBHz in a 1 Hz bandwidth, -31 dB relative to clear air conditions on the APT system) at 1 Hz and 20 Hz sampling rates. The algorithm also provides several supplemental functions including a software selectable detection bandwidth from 2 Hz to 50 Hz (1 Hz increments), spectrum analyzer type output for a 303.333 kHz bandwidth centered on the current carrier frequency and carrier frequency estimates accurate to ±O. 5 Hz. / Master of Science

An experimental study of the structure of turbulence in a tip leakage vortex was conducted in a large scale, linear turbine cascade. The study was performed in a cross sectional plane 0.96 of the axial chord length downstream of the blade leading edge. The cascade consisted of five blades with an aspect ratio of one and an axial chord of 235.2 mm. The tip clearance gap was nominally 2.1% of the blade span. A specially designed rotatable x-wire hot wire probe with high spatial resolution was used to measure both the mean velocity distribution and all six components of the Reynolds stress tensor. An automated probe positioning and digital signal processing system was developed to facilitate quick, accurate measurements at a large number of data points. A geared stepper-motor drive mechanism was used to rotate the endflow hot-wire probe about its axis. Performance of the probe and the data analysis routines was verified by measurements in a fully developed pipe flow. The contribution of turbulence to the over a1l 1osses was investigated by studying both the general level of turbulence and the work done on the fluid by the turbulence stresses. This allowed the study of the physical mechanisms of loss production; spanwise mixing processes were found to be major contributors. The high level of turbulence in the tip leakage vortex was found to amount to about 36% of the total pressure loss generated by the plane near the blade trailing edge. / Master of Science

We develop a general three-stage Moving Average Matched Filter (MAMF) receiver system for digital communications in an environment where the noise conditions are unknown a priori and change constantly and significantly with time. The MAMF is a subset of the class of matched filters which are optimal with respect to enhancing the signal energy relative to the noise power in order to improve discrimination between signals at the receiver. In a time-varying noise environment, a fixed signal cannot be designed and used for transmission which will provide optimal performance at the receiver under all noise conditions. Designing a signal for optimality in a particular noise environment will typically lead to a deteriorated performance in another noise environment relative to a signal which is chosen for the new environment. This deterioration in performance can be so severe that the signal-to-noise ratio (SNR) from the input to the output of the filter is degraded. Ideally, to achieve performance which is more nearly optimal under all noise conditions, the transmitted signal should change or adapt in response to variations in the noise environment. For practical reasons, it is desirable to concentrate all adaptivity in the receiver rather than the transmitter. Typically, a MAMF receiver consists of two stages - a filtering stage and a detection stage. We develop the general design expressions for a three-stage MAMF receiver in which the additional stage is a linear pre-filter placed before the filtering and detection stages. Obviously, if the MAMF is optimal for a given noise condition, any operation performed on the received signal plus noise prior to filtering will potentially reduce performance at that given noise condition by some amount. We accept this performance loss in favor of a pre-filtering operation which can effectively manipulate the transmitted signal upon arrival at the receiver and provide more robust performance in the time-varying noise environment. Specifically, we compare a pre-filter consisting of a unity gain with a prefilter that linearly combines k M x 1 partitions of the transmitted signal vector (i.e. transmitted signal vector of length N = k x M). Proper design of the transmitted signals can ensure that the partitions are linearly independent. In this case, we can view the transmitted signal as representing a k-dimensional subspace of the original M-dimensional signal space. By linearly combining these partitions at the receiver we can achieve any vector within this subspace. We show that we can select these partitions such that the resulting signal vector represents an optimum signal subspace for k noise environments. This is contrasted with the fixed 1-dimensional subspace of the original N-dimensional signal subspace when the pre-filter is a constant gain. The two MAMF receivers are compared by measuring the signal-to-noise ratio improvement (SNRI) of the filters. The SNRI is defined as the output signal-to-noise ratio (OSNR) measured at the output of the filtering stage over the input signal-to-noise ratio (ISNR) measured at the input to the pre-filtering stage. We demonstrate through simulation that the signal subspace version can be more robust with respect to deviation from the absolute maximum SNRI achievable by either system. Using maximum likelihood techniques, we derive an optimal detector for an arbitrary bank of L linear pre-filter and MAMF sections. This is shown to outperform a detection scheme that has been derived for use solely in an optimal binary communication scenario. / Master of Science