Electrophoresis is the technique used to characterize proteins, oligonucleotides, and DNA. Methods employed to date include gel and capillary electrophoresis. Most samples can be characterized by these methods. However, large DNA molecules do not separate well with either method. A newer electrophoresis method involves the use of the Doppler effect to determine a particle’s characteristics. This thesis is concerned with the design and development of an open geometry Doppler electrophoresis instrument for macromolecular characterization in solution where gel characteristics and electroosmotic flow need not be considered. / Master of Science

The method of Pseudo-Linear Identification (PLID) is developed for application in an adaptive control loop. The effects of noise are investigated for the case of full-order system identification, and the results are applied to the use of PLID as a reduced-order system estimator. A self-tuning regulator (STR) is constructed using PLID and the effects of reducing the expected order of the system are demonstrated. A second adaptive control algorithm is presented wherein the STR controller is varied to achieve some degree of closeness to a given model (model-reference adaptive control). / Master of Science

This thesis describes testing of an electrostatic precipitator that has a portion of the main precipitator flow drawn through a porous (fabric) collecting surface. Tests investigated effects of flow through the collecting surface (side flow) on precipitator turbulence and particulate removal efficiency. Particulate removal tests were conducted at both ambient temperature and boiler slipstream conditions. Side flow was shown to reduce turbulence in the boundary layers of the collecting plates, but to have no significant effect on turbulence in the main gas stream (beyond the boundary layer). Side flow was shown to create a more uniform horizontal velocity profile within the precipitator. Side flow was shown to have little effect on the reentrainment of single particles, but appears to reduce reentrainment of an established dust layer. Reentrainment was shown to be an important concern primarily for particles greater than three micrometers in diameter. This research strongly indicated the advisability of using two stage electrostatic precipitation for the collection of particles less than three micrometers in size. / Master of Science

Dormant bud and actively growing shoot tip explants of B. uber were cultured on Murashige & Skoog (MS) and modified woody plant (WPM) basal salts supplemented with organic nutrients and benzylaminopurine (BAP). Shoot tip explants were morphogenically more responsive than dormant bud explants. The modified WPM proved to be better than MS medium for the establishment and proliferation of B. uber cultures. Shoot proliferation was greatest at 8.9 μM BAP. However, BAP at 4.4 μM produced the greatest number of shoots > 10 mm. Indolebutyric acid (IBA) was more effective than naphthaleneacetic acid (NAA) for rooting of microcuttings in vitro. Rooting was best with a low level of IBA (2.5 μM) in the culture medium. Ex vitro rooting of microcuttings using a conventional potting mix of sand-peat-perlite (1:2:1 v/v/v) was superior to all in vitro rooting treatments. Plantlets were acclimated successfully to greenhouse conditions. Genotype differences with regard to both rooting and shooting abilities were observed. / Master of Science

As the size of hybrid microelectronics is reduced, the power density increases and thermal interaction between heat-producing devices becomes significant. A nondimensional model is developed to investigate the effects of heat source interaction on a substrate. The results predict the maximum temperature created by a device for a wide range of device sizes, substrate thicknesses, device spacings, and external boundary conditions. They can be used to assess thermal interaction for preliminary design and layout of power devices on hybrid substrates. Previous work in this area typically deals with semi-infinite regions or finite regions with isothermal bases. In the present work, the substrate and all heat dissipating mechanisms below the substrate are modeled as two separate thermal resistances in series. The thermal resistance at the base of the substrate includes the bond to the heat sink, the heat sink, and convection to a cooling medium. Results show that including this external resistance in the model can significantly alter the heat flow path through the substrate and the spreading resistance of the substrate. Results also show an optimal thickness exists to minimize temperature rise when the Biot number is small and the device spacing is large. Tables are presented which list nondimensional values for maximum temperature and spreading resistance over a wide range of substrate geometries, device sizes, and boundary conditions. A design example is included to demonstrate an application of the results to a practical problem. The design example also shows the error that can result from assuming an isothermal boundary at the bottom of the substrate rather than a finite thermal resistance below the substrate. Several other models are developed and compared with the axisymmetric model. A one-dimensional model and two two-dimensional models are simpler than the axisymmetric model but prove to be inaccurate. The axisymmetric model is then compared with a full three-dimensional model for accuracy. The model proves to be accurate when sources are symmetrically spaced and when sources are asymmetrical under certain conditions. However, when the sources are asymmetrical the axisymmetric model does not always predict accurate results. / Master of Science

Agricultural operations such as harvesting and sorting typify controlled processes. Engineering students who wish to specialize in automatic control often do not get sufficient experience in the integration of the three areas of a complete control system: sensors, computing, and actuation. A teststand was designed and built for laboratory exercises which illustrate the inter-relationship of sensors, computing, and actuation in a sorting operation. Black, gray, and white blocks were placed on a conveyor and moved past two sensors which provided color and position information to a control program. Based upon the information provided by the sensors, the control algorithm activated pneumatic cylinders that sorted the blocks. Two algorithms, identified as open-loop and closed-loop, were tested. For the open-loop tests, the conveyor moved at constant velocity, and for the closed-loop tests, conveyor velocity was cycled. The algorithms calculated the delay between the time a block passed the position sensor and the point where the block was struck by a cylinder, and adjusted the actuation time accordingly. Tests were run at conveyor speeds between 10 and 80 cm/s. Using the open-loop algorithm, 99.7% of the blocks were identified and struck by the correct cylinder, and for the closed-loop algorithm the accuracy was 98.6%. The control program was written in C and executed on an IBM PC. Three laboratory exercises at various levels of difficulty were developed for the teststand. / Master of Science

This study attempted to assess the major determinants of interprovincial migration in the People's Republic of China. The findings suggest that the classical gravity and pull-push hypotheses can also find supporting evidence in the People's Republic of China. Basically, the differential socio-economic characteristics and circumstances determined interprovincial population movement, but relatively speaking, the destination factors played more important roles. Among the variables examined in the study, destination investment and agricultural income level had the strongest pull-force on migrants. On the other hand, unemployment of destination was found to have a push-force discouraging migrants. From the contrast between the positive effect of the destination investment and negative one of the destination unemployment, a conclusion was drawn that the interprovincial migration was largely job-related. Moreover, people in the origin with a higher level of industrialization were less likely to migrate. The analysis also found that the higher level of educational attainment at the origin relative to that at the destination, the higher the migration. In addition, in spite of the similar influence of population and distance on male and female migration streams, the socio-economic conditions affected male migration stream to a larger extent than female migration streams. / Master of Science

Data on safety belt use were collected at two swimming pools over three consecutive summers. The impact of several variables upon safety belt use was examined. First, an Intervention Program (IP) was designed, comprised of Promotional, Reward, and Feedback components. Second, an Awareness/Education (AE) strategy was introduced to children enrolled in swim lessons. Third, belt use was examined before and after a mandatory safety belt use law (BUL) was enacted in Virginia. The moderating effects of the BUL were studied by implementing both the IP and the AE interventions during the pre- and post-BUL environments. Finally, some aspects of a behavioral prompt (i.e., a "Personal" vs. an "Impersonal" delivery method), and their relationship to safety belt use were examined. Major findings include, those individuals most influenced by the IP in the pre-BUL environment were those same individuals who were influenced by the BUL. Thus, while the IF did have an impact upon mean safety belt use levels in the post-BUL context, belt use increases over Baseline were not as dramatic as those observed in the pre-BUL environment. / Master of Science

Electron diffraction and microwave studies of hionyl tetrafluoride (SOF₄) have been conducted in order to determine its molecular structure. The results from these investigations were however found to be inconsistent. In view of these controversial findings, a microwave investigation was undertaken to accurately assign the rotational transitions, compare the determined moments with those from prior studies and examine the Stark effect in SOF₄ in order to determine its dipole moment. Calculations using an Asymmetric Rotor program were made to determine the Stark coefficients for transitions having J = 1-40 and frequencies between 12-27 MHz. Absorption peaks were identified as had been predicted by theoretical calculations. The spectrum was very rich and exhibited many strong Q-branch transitions (ΔJ=0). Most were high J transitions whose Stark components could not be resolved. The R-branch transitions (ΔJ=1), were observable for only low J transitions and at very low Stark voltages. Stark peaks were not well resolved for the low J transitions; most of them had been masked by the strong Q-branch transitions. Data from the 1(0,1) ----> 2(1,1) transition at 14049 MHz gave a dipole moment of 0.97 Debye. A least squares fit of the observed frequencies correlated well with those from the structure D4, proposed by Hedberg and Hedberg. The rotational constants and moments of inertia were calculated to obtain the values: A = 4181.0 ± 0.04 MHz B = 3289.8 ± 0.04 MHz C = 3206.3 ± 0.04 MHz I_a= 120.9 ± 0.02 amu Ų I_b= 153.6 ± 0.02 amu Ų I_c= 157.6 ± 0.02 amu Ų / Master of Science

To study the influence of the time-dependent behavior of various materials being considered for use in orbiting precision segmented reflectors, simple sandwich beam models are developed. The beam models included layers representing face sheets, core and adhesive. The issue of time-dependency is essential because the expected life of a reflector is on the order of 20 years. Using the principle of stationary potential energy, the elastic response of three-layer and five-layer symmetric sandwich beams to mechanical and thermally-induced loads is studied. The sensitivity of the three-layer and five-layer sandwich beams to reductions of the material properties is studied. Using the correspondence principle of viscoelasticity, these elastic models are transformed to time-dependent models. Representative cases of time-dependent material properties are used to demonstrate the application of the correspondence principle and evaluate the time-dependent response of the reflector. To verify the viscoelastic models, and to obtain a better idea of the amount of time-dependency to expect from the materials, simple time-dependent experiments on candidate materials were performed. Candidate materials include a quartz-epoxy face sheet material and a glass-imide honeycomb core material. The percent increase in strain for a constant stress for the quartz-epoxy in tension and the honeycomb in shear were measured. For both, a four-parameter fluid model captured the essential characteristics of their behavior. These four-parameter fluid models were then used in the three-layer sandwich beam model to predict the time-dependent response of the beam to three-point bending. This predicted response was compared to experimental results of a sandwich beam subjected to three-point bending. / Master of Science