In this work, we present a unified, general approach to variance reduction in agent evaluation using machine learning to minimize variance. Evaluating an agent's performance in a stochastic setting is necessary for agent development, scientific evaluation, and competitions. Traditionally, evaluation is done using Monte Carlo estimation (sample averages); the magnitude of the stochasticity in the domain or the high cost of sampling, however, can often prevent the approach from resulting in statistically significant conclusions. Recently, an advantage sum technique based on control variates has been proposed for constructing unbiased, low variance estimates of agent performance. The technique requires an expert to define a value function over states of the system, essentially a guess of the state's unknown value. In this work, we propose learning this value function from past interactions between agents in some target population. Our learned value functions have two key advantages: they can be applied in domains where no expert value function is available and they can result in tuned evaluation for a specific population of agents (e.g., novice versus advanced agents). This work has three main contributions. First, we consolidate previous work in using control variates for variance reduction into one unified, general framework and summarize the connections between this previous work. Second, our framework makes variance reduction practically possible in any sequential decision making task where designing the expert value function is time-consuming, difficult or essentially impossible. We prove the optimality of our approach and extend the theoretical understanding of advantage sum estimators. In addition, we significantly extend the applicability of advantage sum estimators and discuss practical methods for using our framework in real-world scenarios. Finally, we provide low-variance estimators for three poker domains previously without variance reduction and improve strategy selection in the expert-level University of Alberta poker bot.

Chromium has been used extensively in the industry process of metal refinishing and electroplating. It is also a byproduct of the processing of fissionable materials at United States Department of Energy facilities. Chromate (Cr (VI)) is soluble and readily absorbed by cells, while the reduced form of chromium, Cr (III), is insoluble. Thus means of reducing Cr (VI) to Cr (III) in the environment is a potential means of remediation. Desulfovibrio desulfuricans strain 27774 is a sulfate reducing bacterium that can reduce Cr (VI). It also can respire nitrate to ammonia. As some sites of chromium contamination also contain high concentrations of nitrate, an investigation of Cr (VI) reduction under nitrate reducing growth conditions by D. desulfuricans strain 27774 was conducted. A growth medium that was compatible with the colorimetric assay for Cr (VI) and did not itself reduce Cr (VI) was formulated. Cell assays determined that Cr (VI) reduction was primarily in the supernatant, catalyzed by a secreted secondary metabolite. A genomics investigation identified two pathways as possible mechanisms. / Bayer School of Natural and Environmental Sciences / Environmental Science and Management (ESM);= / MS / Thesis

Perchlorate is one of the major emerging contaminants of concern and has been found in soil and water systems throughout the United States. Human exposures to perchlorate could occur by ingestion of contaminated water and food as well as by skin contact. Studies show that perchlorate blocks the sodium iodide symporter (NIS) protein in human body, which results in several diseases. It has been demonstrated that perchlorate can be removed by Advanced Reduction Processes (ARPs) that combine chemical reductants (e.g. sulfite) with activating methods (e.g. UV light) in order to produce highly reactive reducing free radicals that are capable of rapid and effective perchlorate reduction. However, other compounds in a real system might inhibit or promote this reduction process. Natural organic matter (NOM) widely exists in the environment and it can absorb UV light, so it has the potential to influence the process of perchlorate reduction by ARPs that use UV light as the activating method. Therefore, batch experiments were conducted to obtain data on the impacts of natural organic matter and light intensity on destruction of perchlorate by the ARPs that use sulfite activated by ultraviolet light produced by low-pressure mercury lamps or KrCl excimer lamps. The results indicate that NOM strongly inhibits perchlorate removal by either the sulfite/UV-KrCl or the sulfite/UV-L ARP, because NOM competes with sulfite for UV light and can possibly scavenge sulfite radicals. Even though the absorbance of sulfite is much higher at UV wavelength of 222 nm than that at 254 nm, the results indicate that a higher portion of perchlorate was removed with the UV-L lamp than with the UV-KrCl lamp. The results of this study will help to develop the proper way to apply the ARPs in a real wastewater treatment plant.

With increasing energy costs and competitive pressures, interest has increased in surveying installed pumps for potential energy savings. Field pump efficiency tests are required to assess pumping performance and help to identify improvement opportunities. This work concerns the on-site measurements of pulp-suspension pumping efficiency. This involves the measurement of pump head, flow rate and power consumption. Provided that consistent flow measurements are available, it is possible to reliably and non-invasively measure actual pump system efficiencies in pulp suspension flow, with a minimum process disturbance. As part of a most appropriate measurement-procedure study, four portable nonintrusive flow meters were evaluated on site for pulp suspension flow. The Fast Fourier Transform Doppler was found to be the most suitable for a pulp mill pump survey. Efficiency measurements were performed on six pump systems with motors between 100 and 700 HP. It is shown that as-installed pump efficiency can be used to help predict the degradation of the pump and also its effect on the pumping system’s operation. A system approach analysis was performed in each case, which can be effective in assessing system performance and finding potential enhancements. The use of variable speed drives allows the operating point to move along the system curve, requiring less energy to drive the pump. VSD of larger motors are expensive and their profitability compared to other modification alternatives should always be carefully checked by calculations based on accurate on site measurements and life cycle costs. Finally, in this survey of six pump systems, significant potential savings of around 30% of present power consumption were found.

An integrated NOx adsorption-reduction process has been proposed in this study for the treatment of flue gases under lean-burn conditions by decoupling the adsorption and reduction into two different zones. The hypothesis has then been validated in a novel internal circulating fluidized bed. The adsorption and reaction performance of Fe/ZSM-5 for the selective catalytic reduction (SCR) of NOx with propylene was investigated in a fixed bed reactor. The fine Fe/ZSM-5(Albemarle) catalyst showed reasonable NOx adsorption capacity, and the adsorption performance of the catalyst was closely related to the particle size and other catalyst properties. Fe/ZSM-5 catalyst was sensitive to the reaction temperature and space velocity, and exhibited acceptable activity when O₂ concentration was controlled at a low level. Water in the flue gas was found to slightly enhance the reactivity of Fe/ZSM-5(Albemarle), while the presence of CO₂ showed little effect. SO₂ severely inhibited the reactivity of Fe/ZSM-5(Albemarle), and the deactivated catalyst could be only partially regenerated. Configurations of the reactor influenced the hydrodynamic performance significantly in a cold model internal circulating fluidized bed (ICFB) reactor. For all configurations investigated, the high gas bypass ratio from the annulus to draft tube (RAD) and low draft tube to annulus gas bypass ratio (RDA) were observed, with the highest RDA associated with the conical distributor which showed the flexible and stable operation over a wide range of gas velocities. Solids circulation rates increased with the increase of gas velocities both in the annulus and the draft tube. Gas bypass was also studied in a hot model ICFB reactor. The results showed that the orientation of perforated holes on the conical distributor could be adjusted to reduce RAD and/or enhance RDA. Coarse Fe/ZSM-5(PUC) and fine Fe/ZSM-5(Albemarle) catalysts were used in an ICFB and a conventional bubbling fluidized bed to test the NOx reduction performance. Coarse Fe/ZSM-5(PUC) catalyst showed poor catalytic activity, while fine Fe/ZSM-5(Albemarle) catalyst exhibited promising NOx reduction performance and strong inhibiting ability to the negative impact of excessive O₂ in the ICFB reactor, proving that the adsorption-reduction two-zone reactor is effective for the NOx removal from oxygen-rich combustion flue gases.

Bibliography: leaves 244-259. / xxii, 259 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Copper loaded Australian natural zeolites and ZSM-5 zeolites were investigated for the selective catalytic reduction of nitrogen oxides using CH4 and C3h6 with the specific aims of investigating natural zeolite as an alternative support to ZSM-5, determining a rate law for the selective catalytic reduction of nitrogen oxides using C3h6 over Cu-ZSM-5; and, investigating the molecular scale interactions of the reaction gases with Cu-ZSM-5. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1999

Manganese furnace dust is made up of volatiles and fine particles of the raw materials collected from the off-gas during smelting of manganese alloys. Impediments to the recycling of the manganese furnace dust back to the ferroalloy furnaces are handling due to the presence of tar, and the potential accumulation of zinc in the furnaces, which can cause irregularities in their operation. The aim of the thesis was to establish conditions for zinc removal from the dust and assess the feasibility of the dust recycling in the Tasmanian Electrometallurgical Company sinter plant. Major findings are: - Manganese furnace dust taken from the settling ponds contained water, carbonaceous materials (tar), and metal oxides. The carbon content of the dried furnace dust was about 20% and the average manganese and zinc contents were 33.4 and 1.29%, respectively. Moisture content was 30-60%. - The tar components were aliphatic hydrocarbons and polyaromatic hydrocarbons, their derivatives, and sulphur- and oxygen-containing compounds with a wide range of carbon number (15-28) and boiling point (230-530oC). Light hydrocarbons were not detected. - If manganese furnace dust was recycled to ferroalloy furnaces through the sintering plant, the overall zinc input had increased by 51-143%. Sustainable utilisation of manganese furnace dust should include enhanced zinc removal. - Reduction of zinc oxide from manganese furnace dust pellets started at 800oC. Zinc oxide was reduced to zinc vapour by tar in the dust. Temperature and gas atmosphere were key parameters affecting the zinc removal from the dust. The zinc removal rate increased with increasing temperature and was close to completion at 1100oC. - Optimal conditions for removal of zinc from the furnace dust include: temperature in the range 1000-1150oC, inert gas atmosphere and furnace dust fraction in the furnace dust-manganese ore mixture above 60%. - Zinc removal in the processing of manganese furnace dust in the sinter plant was low because of zinc reoxidation in the sinter bed. This makes the sinter plant unsuitable for recycling of the dust. More suitable conditions for utilisation of manganese furnace dust exist in the rotary hearth furnace, which development is recommended for further study.

Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1999. / Bibliography: leaves 244-259.

Thesis (M.A.)--Bowling Green State University, 2009. / Document formatted into pages; contains vii, 71 p. Includes bibliographical references.

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1916. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed April 21, 2009)