The simulation of an algorithm for the active control of combustion noise generated by a turbulent flame produced by an open burner is developed in this thesis. The simulation includes (1) an autoregressive model of real combustion noise, (2) a feedback loop based on the "observer" method, (3) a model of the transfer function between the acoustic driver and the sensor through the flame, and (4) a method to take into account the time-delay due the calculation of the algorithm. A practical implementation of the control strategy is also proposed. An attenuation of up to 40 dB is obtained in the 0 - 3000 Hz band, decreasing with the time-delay required for creation of the feedback signal. The influence of the order of the autoregressive model is studied, and it is shown that better results are obtained by increasing the order. The choices for the location of the activator and for the type of sensor are investigated and discussed. Further analytical research on the method of computing the feedback signal in the presence of time-delay is identified. / Master of Science

Clostridium difficile causes pseudomenbranous colitis (PMC) and diarrhea in humans. Toxigenic strains of C. difficile produce two toxins. Toxin A is an enterotoxin and cytotoxin, and toxin B is a potent cytotoxin. The gene encoding toxin A has been sequenced and was shown to possess a 2.5 kb region, containing 38 similar repeating amino acid sequences, at the 3' -end of the gene. This region of the toxin A gene codes for the carbohydrate-binding portion of the toxin. The monoclonal antibody PCG-4 (MAb) binds to this portion of toxin A and neutralizes its enterotoxic activity. In addition, this monoclonal antibody has been shown to immunoprecipitate toxin A, suggesting that the MAb PCG-4 is binding to two or more similar epitopes on the toxin. The goal of this research project was to identify the neutralizing epitopes recognized by the MAb PCG-4 on the surface of the toxin A. To map the epitopes bound by the MAb PCG-4, a series of overlapping deletion clones were constructed from a 4.7 kb fragment from the 3'-end of the toxin A gene. The recombinant polypeptides expressed by these clones were tested for reactivity with the MAb PCG-4. By comparing the overlapping polypeptides, defined as either PCG-4 reactive or nonreactive, I localized the PCG-4 epitope to a 44-amino acid sequence situated between the amino acid residues 2098-2141 of toxin A A similarity search of the toxin with the 44-amino acid sequence containing the PCG-4 epitope revealed the presence of two other possible PCG-4 epitopes located between the amino acid residues 2355-2398 and 2459-2502. However, subsequent cloning experiments showed that only the region located between the amino acid residues 2355-2398 contained a PCG-4 reactive epitope. The identification of two similar epitopes within the toxin's structure explains how this monoclonal antibody is able to immunoprecipitate toxin A in the absence of subunits. Furthermore, I found that small recombinant polypeptides, containing the PCG-4 epitope lost reactivity with this monoclonal antibody following denaturation, suggesting that the epitopes recognized by this monoclonal antibody are conformationally dependent. / Master of Science

A methodology and prototype has been developed which enables users of GML and SCRIPT on an IBM 3090 to preview documents on a locally attached personal computer before printing. Currently, no utility exists to accomplish this activity. This new preview process is graphical in nature and provides an absolute picture of the document, exactly as it will be printed on an IBM 3812 laser printer. / Master of Science

El objetivo del documento es presentar un enfoque que evalúa el desempeño de la política monetaria y la política fiscal en una economía pequeña, abierta y parcialmente dolarizada como la peruana, más allá de las reglas o las funciones de reacción de política convencionales. En el período contenido entre el primer trimestre de 1990 y el último trimestre de 2013, se pretende explicar la política monetaria a partir de una Regla de Taylor, y la política fiscal sobre la base de una función de reacción. La Regla de Taylor expone el uso de la tasa de interés como instrumento de política, a partir de las brechas de producto y de inflación, y el efecto de la depreciación cambiaria. Además, en este estudio se propone incorporar el efecto de variables del ámbito internacional (los precios internacionales) y del marco político (la calidad institucional), con el propósito de analizar cómo cambia la eficiencia de las acciones y las decisiones de política. De otro lado, las acciones de política fiscal se enfocarán en el manejo de la brecha de gasto real como indicador de impulso fiscal, a través de una función de reacción, en la que se evalúa el efecto de la brecha de producto. En adición, se repite la estrategia de incorporar el impacto proveniente del entorno mundial (los términos de intercambio) y el desempeño institucional (la restricción política). Por tanto, los resultados muestran que no habría márgenes de maniobra para las acciones de política, puesto que al demostrar la dependencia de éstas al contexto internacional, y al perfil institucional interno, se comprueban las restricciones de política económica.

Following the U.S. Environmental Protection Agency’s specifications for pesticide registration tests, 12 experimental ponds were constructed in Blackstone, VA at VPI&SU Southern Piedmont Agricultural Experiment Station. Colonization and succession of the ponds’ phytoplankton communities were investigated during the first year after filling. Taxa richness and densities, biomass as chlorophyll a, and primary productivity (in situ oxygen method) were measured. In addition, water quality data were collected and analyzed. The dominant taxonomic groups were the Cyanophyceae, Chlorophyceae (with Desmidiaceae dominating), Dinobryon (in the Chrysophyceae), Dinophyceae, and Bacillariophyceae. Similar successional patterns in all 12 ponds occurred, however, the community structure between ponds was not similar at any given time. Although the ponds had statistically similar environmental characteristics, they varied in their community structure indicating that, after one year, they were not mature enough for use as replicate test systems. No structural parameter could be measured with reasonable precision using a three replicate pond scheme recommended by the USEPA. Taxa richness could be measured with a precision of approximately 25% over the year; and was ≤11% during the peak growing months. Taxa densities could usually be measured with a precision of <100% during these months. The in situ oxygen method for measuring primary productivity was found to be to insensitive during early colonization. The heterogeneity of the ponds’ phytoplankton communities indicate that mesocosms will need to be managed to produce replicate experimental units. / Master of Science

New radiometric ages and field relations within the Coastal Maine Magmatic Province suggest a bimodal distribution of igneous rocks in both space and time. The earlier magmatic event is represented by the development of large igneous complexes which occur along a magmatic axis extending from Calais to Penobscot Bay, Maine. These complexes are dominated by mafic magmatism ranging in composition from olivine norite through quartz diorite and granodiorite. Partially crystallized mafic magmas are often intruded by slightly peraluminous biotite ± hornblende granites as demonstrated by the occurrence of a wide range of enclave-host relationships. The igneous complexes are commonly cut by younger voluminous biotite ± hornblende granites and represent the development of a new tectonothermal perturbation of the crust. New radiometric data on igneous rocks from the Moosehorn Igneous Complex (MIC) near Calais, Maine indicate that the earlier magmatic event occurred during the interval of 440-420 m.y. This magmatic event in the MIC is marked by the emplacement of a large, complex assemblage of olivine norite, hypersthene gabbro, gabbro, biotite ± hornblende diorite, quartz diorite, and granodiorite. Compositional layering is present in many mafic bodies, and most commonly strikes northwest and dips gently to the southwest. The Moosehorn complex was intruded by the Baring granite before complete crystallization, resulting in the development of texturally diverse enclave swarms within the granite. / Master of Science

An attempt is made to understand the phenomenon of aeroelasticity as applied to the helicopter rotors, specifically laminated composite rotor blades. Realizing the immense complexity of the problem, a beginning has been made by developing a structural model for a rotating composite beam. Present work has three objectives; 1) To carry out an extensive survey of research related to the aeroelastic analysis of rotor blades, 2) To expand an existing finite element model by introducing new degrees of freedom and validate the changes, 3) and, finally using this model to carry out a linear static and dynamic analysis for a rotating composite beam. It was found that the rotation and fiber orientations have a pronounced effect on the static deflections and the natural frequencies of vibration of the laminated beam. / Master of Science

A quadtree-like representation for storing gridded elevation data is described. In its simplest form, the data structure is a pyramid with each node containing a two bit code. The root of the pyramid has associated with it the minimum elevation for the grid and the range (the greatest power of 2 less than or equal to the difference between the minimum and maximum elevation values). Any specified elevation value is determined by traversing a path from the root to a leaf node. As the traversal proceeds, the minimum and range values are refined by interpreting the codes stored at each node along the path. At the leaf level, the final minimum value equals the associated elevation value. Since the total number of nodes in the pyramid is 4/3 the number of elevation grid cells, the amortized storage cost is less than 3 bits per grid cell. When the difference between elevation values is not "too great", this basic representation is quite effective. For data where greater elevation differences occur between neighboring cells, this basic method is modified to improve the representation, but at a cost in storage. Our method is most appropriate for efficient secondary storage archival, such as on CD-ROM. It also allows efficient retrieval of complete elevation data from any subregion, at multiple scales, within the entire elevation database. / Master of Science

A new method for analyzing axisymmetric, high-frequency transformers is presented. The method is based on the simultaneous solution of the coupled, nonlinear thermal and electromagnetic equations using the finite element method. A novel technique for modeling the reluctivity of the soft-ferrite core material permits a time-harmonic transformation of the electromagnetic equations. This eliminates the need to step through time while maintaining the effects of hysteresis losses. Also, a quasi-steady formulation of the heat-conduction equation eliminates the time dependency on the thermal problem. A direct substitution iterative scheme is used in conjunction with the finite element method to compensate for the coupled and nonlinear nature of the equations. To verify the magnetics portion of the finite element code numerically, a linear, uncoupled test case is given which compares the magnetic results from the present method to those from a commercial software package. To investigate the accuracy of the fully coupled and nonlinear model, an example is presented which compares the results from the numerical analysis of an inductor to those obtained by experimental measurement. / Master of Science

Three long-term field experiments were established in the spring of 1978 and continued through 1988 to evaluate corn (Zea <i>mays</i> L.) response to high Cu levels from Cu rich swine manure and CuS0₄ applications. The field research was conducted on soils with diverse properties, i.e., on a Bertie fine sandy loam (Aquic Hapludults), a Guernsey silt loam (Aquic Hapludalfs), and a Starr-Dyke clay loam (Fluventic DystrochreptsTypic Rhodudults). Three treatments in the long-term field experiments on the three soils were a control, annual applications of eu as eu rich swine manure, and annual applications of Cu as CuS0₄ equivalent to that in the manure. After the 11 years, 1109 mt ha⁻¹ of wet Cu rich swine manure were applied for the manure treatment. The Cu rich manure contained an average of 1316 mg Cu kg⁻¹, An average of 325 kg Cu ha⁻¹ added to the soils from the manure application over the 11 years exceeded U.S.E.P.A. guidelines for safe copper loading levels for cropland by 45 kg ha⁻¹. Copper concentrations in corn ear leaves were within the normal range of 3 to 20 mg kg⁻¹ where the 325 kg Cu ha⁻¹ were applied to the soil as either Cu rich manure or CuS0₄. Concentrations of Cu in the grain were also in the normal range of 1 to 5 mg kg⁻¹ where the high level of the two Cu sources was applied to soils. There was no decrease in corn yield on the three soils from application of either Cu source. / Master of Science