Modern Control Theory is applied to analyze an existing aluminum mill drive, which was originally designed by Classical Methods. The system is studied with Optimal Control and z-transform zero-pole locus tools. The results and also the original design are compared with the performance of simulation. The models are built with the transition matrix and iterative procedures. Conclusions about the appropriated design methods and improvements to the control scheme result from the investigation. / Master of Science / incomplete_metadata

The major objectives of this study were to examine electrical and electromechanical properties of SBR filled with carbon black in the 0-70 phr range. The experiments were divided into four parts: dielectric measurement, loss modulus and phase angle measurements, temperature rise measurement during stress cycling, and dynamic conductivity measurement. It is established that there are three distinct conduction regimes existing at carbon black loadings below, at, and above the percolation threshold. Characteristics of dielectric dispersion depend strongly on carbon black loading and frequency. Dielectric and AC conductivity measurements are shown to provide a nondestructive method to explore the carbon black network inside the rubber. Both loss modulus and phase angle are related to hysteresis properties, and to temperature rise due to compressive cycling. Measurements of these parameters will be discussed in detail, as functions of carbon black loading, stress and strain amplitudes, and oscillation frequency. These and other results can be understood in terms of the mechanics of the carbon black network. The variation of conductivity with strain amplitude is related directly to the interplay between the "persistent" and "transient" fractions of carbon black network. It is shown that, owing to its experimental accuracy and great sensitivity to carbon black network changes, the dynamic conductivity measurement is preferable to traditional modulus measurements for determining certain dynamic properties of carbon black filled rubbers. / Master of Science

Digital Signal Processing (DSP) is a technology-driven field which develops as early as mid-1960 when computers and other digital circuitry became fast enough to process large amounts of data efficiently. Since then techniques and applications of DSP have been expanding at a tremendous rate. With the development of large-scale integration, the cost and size of digital components are reducing, and speed of digital components is increasing. Thus the range of applications of DSP techniques is growing. Almost all current discussions of speech bandwidth compression systems are directed toward digital implementation, because these are now the most practical. The importance of DSP appears to be increasing with no visible signs of saturation. This thesis provides the description and results of designing laboratory experiments for the illustration of basic theory in the field of DSP. All experiments are written for the Texas Instruments TMS320I0 digital signal processing microcomputer and based on softwares provided by Atlanta Signal Process, Inc. (ASPI). The use of the 320/pc Algorithm Development Package (ADP) and Digital Filter Design Package (DFDP) developed by ASPI is introduced. The basic concepts, such as linear convolution, Finite Impulse Response (FIR) and Infinite Impulse Response (IIR) filter design, Fast Fourier Transform (FF1), are demonstrated. The IBM PC AT is interfaced with the TMS32010 processor. The experiments and their introductions in the thesis also serve as a manual for the DSP Laboratory; to complement the introductory signal processing course. / Master of Science

Laboratory-obtained, manufacturer-supplied hearing protector attenuation ratings typically overestimate the workers' protection level In the workplace. In addition, several work-related in-field factors often degrade protection performance of the hearing protection devices (HPDs), posing the threat of underprotection for industrial workers. This research investigated the effects of HPD wearing time, subject activity movement, and HPD fitting procedure on the frequency-specific attenuation and user-rated comfort achieved with a popular foam cushion earmuff, two types of earplugs (user-molded foam and pre-molded, triple-flanged polymer), and an earmuff over foam earplug combination. Both attenuation and comfort data were collected from 40 naive but audiometrically normal subjects. Using a psychophysical real-ear-attenuation-at-threshoId-measurement procedure, attenuation data were obtained before, during, and after the activity movement tasks, which induced typical worker movements, so that the influence of wearing time and activity movement could be determined. Bipolar comfort rating data were also collected before and after the activity movement tasks, The results of statistical analyses indicated that achieved attenuation and user comfort significantly decreased over a two-hour wearing period and that training to achieve better fitting markedly improved protection, although these changes were device- and frequency-specific. Loss in frequency-specific attenuation over the wearing period was up to 6.3 dB for all HPDs except the foam plug, and attenuation Improvement due to training ranged from 4 to 14 dB for all HPDs except the earmuff at 1000 Hz and below. Almost no difference In achieved attenuation or comfort was found between the two activity (head/torso and temporomandibular) movements, but the earmuff tended to slip during highly kinematic head/torso movement. In general, out of the four different HPD configurations used in the study, the foam plug was very resilient to either type of activity movement but did benefit more than the other devices from the training for proper tilting; it was also perceived as the most acceptable and stable HPD by the subjects. In summary, the research illuminated the strong influence of in-field factors on HPD effectiveness. / Master of Science

After a U. S. Navy ship is built but before it is placed into service, many performance tests of all shipboard systems are conducted. These tests vary greatly in who performs the test, the purpose of each test, which system or systems are being tested, and the duration of each test. As naval warfare ships become increasingly complicated, the performance tests that are conducted also become numerous and complex. The current test philosophy prescribes that for each test and test organization, telemetry cables for electrical sensors are strung throughout the ship immediately prior to the test being conducted. As the shipboard tests and trials become more numerous and complex this philosophy becomes expensive from a labor and materials point of view. This thesis proposes an economical solution to the current test and trials problem by offering a fiber optic network with optical sensors. The fiber optic network will be designed to accommodate as many different users as possible, and it will be installed once, during the new ship construction. Prior to the network design, optical fiber sensor schemes are discussed. One sensing scheme, using quartz crystal oscillators, looks promising for the test and trials application. This one sensing method can be applied to acceleration, velocity, displacement, temperature, current, and voltage. Thus economies can be realized by using one network and sensor type for the majority of tests and trials applications. / Master of Science

Once a reactor is critical and at a constant power level, the net reactivity at any time is zero. The major contributions to changes of reactivity in the V.P.I. Argonaut reactor are: 1) Fuel and coolant temperature changes 2) Graphite temperature changes 3) Xenon poisoning The control rods have to be continuously positioned so that the total reactivity change of these parameters is nullified. The reactivity effects of the fuel and coolant have been combined into one temperature coefficient because for this investigation they are assumed to have simultaneous temperature changes. An experiment was conducted to measure the temperature coefficient of fuel and coolant which was found to be negative. The temperature coefficient for graphite was measured by installing heaters in two graphite blocks which were placed in the core. This experiment showed the reactivity effect of the graphite to be positive. The reactivity effect due to xenon poisoning was calculated using the xenon-iodine equations. The results of these experiments and calculations were used to predict the position of the control rods during long power operation. The predicted position was in good agreement with the actual position. / Master of Science

Starting in September 1984, the Telesign project is an extensive and complex project proposed and undertaken by Dr. Nadler at Virginia Tech. The emphasis of this project is to enable the members of the deaf community to communicate visually using sign language or lip reading over the telephone network. The Image Processing Board (IPB) is the 'Brain' of the whole system. The IPB processes a given frame of an image to transmit only selected data. It uses the pseudo-laplacian operator, invented by Dr. Nadler, for edge detection. According to a recent survey of various edge detection algorithms by D. E. Pearson, [1], the pseudo-laplacian operator is the most efficient one and it produces the most natural pictures. The whole IPB hosts about one hundred LSI/VLSI chips according to the present hardware description. In the case of such a big system, hardware simulation becomes mandatory in order to ensure reliability of the design and to anticipate any kind of logic or timing errors in the design. This thesis describes the modifications to the original design to make it reconfigurable with proper initialization and the Hardware Simulation of the IPB, using General Simulation Program (GSP), including some comments on the simulators available at Virginia Tech and in particular a critique of the simulator used here. Many improvements to the simulator are suggested. Precautions to be taken while preparing the lay-out and wiring of the IPB, suggestions to simplify the design at some points at the cost of a few more chips, and lastly the instructions to run the models to get the required results, are outlined in this thesis. / Master of Science

Studies were conducted to evaluate the effect of pre-irrigation media moisture deficit, irrigation application rate, and intermittent irrigation on irrigation efficiency [(amount applied - amount leached) amount applied' 100] of spray stake-irrigated, container-grown plants. In the first experiment, pine bark-filled containers were irrigated to replace moisture deficits of 600, 1200, or 1800 ml. Deficits were returned in single, continuous applications at application rates of 148, 220, and 270 ml/min. Application rate did not affect irrigation efficiency. Efficiency decreased with increased medium moisture deficit. In the second experiment, containers, at 600 ml media moisture deficits, were irrigated with 400 or 600 ml (65% and 100% water replacement, respectively). Irrigation volumes were returned in a single, continuous application or in 100ml applications with 30 min intervals between irrigations (intermittent). Irrigation efficiency was greater with intermittent irrigation, 95 % and 84 % for 400 and 600 ml replacement, respectively, than with continuous irrigation, 84% and 67% for 400 and 600 ml replacement, respectively. When applied intermittently, most water loss from containers occurred after 400 ml were applied. In the third experiment, containers were irrigated with 600 ml (100% water replacement) in 50, 100, or 150 ml applications with 20, 40, or 60 min intelVals between applications. A control was included in which 600 ml was applied in a single, continuous application. Irrigation efficiency increased with decreasing application volume and increasing length of interval between applications. The greatest efficiency (86%) was produced with an irrigation regimen of 50 ml applications with at least 40 min between applications. The control treatment (continuous) produced an irrigation efficiency of 62%. When applied intermittently, most water loss from containers occurred after a total of 300 ml were applied. / Master of Science

Hearing protection devices (HPDs), a widely used countermeasure against noise-induced hearing loss, are laboratory-tested for their attenuation (noise reduction) capabilities. Unfortunately, laboratory tests overestimate the in-workplace performance of the devices, potentially leading to inadequate protection for the user. Many factors affect in-field effectiveness, including the physical design and "wearability" of the protector. Wearability, a highly subjective aspect which encompasses such characteristics as user comfort, ease of use, and acceptability, directly affects performance by influencing the regularity of use and the manner in which a protector is worn. This research investigated the influence of the user's work-related activities over a prolonged wearing period, and of variations in headband compression force and cushion material (liquid- or foam-filled) on achieved noise attenuation and wearability (comfort and acceptability) of earmuff hearing protectors. REAT (real-ear attenuation at threshold) testing procedures were used to collect attenuation data on 24 subjects, both prior-to and following completion of a simulated work task. Bipolar rating scales were utilized to collect pre- and post-task wearabi1ity data. Statistical analyses demonstrated that the work-related movement and wearing time significantly reduced achieved attenuation and, for higher compression earmuffs, also degraded perceived comfort and acceptability. A high headband compression force was 1inked to increased attenuation and to poorer user comfort and acceptance. The data revealed no significant difference in achieved attenuation or wearability between cushion types. The results illustrate the powerful influence of physical activity on HPD effectiveness and the criticality of certain earmuff design parameters to both attenuation and wearability. Furthermore, the existing tradeoff in earmuff design between comfort and attenuation was clearly demonstrated. / Master of Science

Rising energy demands and the continual push to find more energy efficient technologies have been the impetus for the investigation of waste heat recovery techniques. Diesel engine exhaust heat utilization has the potential to significantly reduce the consumption of fossil fuels and reduce the release of greenhouse gases, because diesel engines are ubiquitous in industry and transportation. The exhaust energy can used to provide refrigeration by implementing an organic Rankine cycle coupled with a vapor-compression cycle. A critical component in this system, and in any waste heat recovery system, is the heat exchanger that extracts the heat from the exhaust. In this study, a cross-flow microchannel heat exchanger was geometrically examined and thermally tested under laboratory conditions. The heat exchanger, referred to as the Heat Recovery Unit (HRU), was designed to transfer diesel exhaust energy to a heat transfer oil. Two methods were developed to measure the geometry of the microchannels. The first was based on image processing of microscope photographs, and the second involved an analysis of profilometer measurements. Both methods revealed that the exhaust channels (air channels) were, on average, smaller in cross-sectional area by 11% when compared to the design. The cross-sectional area of the oil channels were 8% smaller than their design. The hydraulic diameters for both channel geometries were close to their design. Hot air was used to simulate diesel engine exhaust. Thermal testing of the heat exchanger included measurements of heat transfer, effectiveness, air pressure drop, and oil pressure drop. The experimental results for the heat transfer and effectiveness agreed well with the model predictions. However, the measured air pressure drop and oil pressure drop were significantly higher than the model. The discrepancy was attributed to the model's ideal representation of the channel areas. Additionally, since the model did not account for the complex flow path of the oil stream, the measured oil pressure drop was much higher than the predicted pressure drop. The highest duty of the Heat Recovery Unit observed during the experimental tests was 12.3 kW and the highest effectiveness was 97.8%. To examine the flow distribution through the air channels, velocity measurements were collected at the outlet of the Heat Recovery Unit using a hot film anemometer. For unheated air flow, the profile measurements indicated that there was flow maldistribution. A temperature profile was measured and analyzed for a thermally loaded condition. / Graduation date: 2012