This work presents a decision-making framework for global optimization of detailed renewable energy processes considering technological uncertainty. The critical uncertain sources are identified with an efficient computational method for global sensitivity analysis, and are obtained in two different ways, simultaneously and independently per product pathway respect to the objective function. For global optimization, the parallel stochastic response surface method developed by Regis & Shoemaker (2009) is employed. This algorithm is based on the multi-start local metric stochastic response surface method explored by the same authors (2007a). The aforementioned algorithm uses as response surface model a radial basis function (RBF) for approximating the expensive simulation model. Once the RBFs parameters are fitted, the algorithm selects multiple points to be evaluated simultaneously. The next point(s) to be evaluated in the expensive simulation are obtained based on their probability to attain a better result for the objective function. This approach represents a simplified oriented search. To evaluate the efficacy of this novel decision-making framework, a hypothetical multiproduct lignocellulosic biorefinery is globally optimized on its operational level. The obtained optimal points are compared with traditional optimization methods, e.g. Monte-Carlo simulation, and are evaluated for both proposed types of uncertainty calculated.

Adsorbent technology employing specificity towards a broad range of target molecules is becoming increasingly important for a variety of applications such as filtration, separation, purification and/or storage of fluids. The development of newer, more efficient adsorbent materials is a growing concern for civilian, first responder, and military uses. This dissertation is focused on the synthesis and characterization of novel, nanoporous adsorbents incorporated with metal salts either by further functionalization of pre-synthesized substrates or as precursors in the formation of porous composites like metal-organic frameworks (MOFs). The biphasic substrate primarily used in this work was made up of mesoporous silica derived from MCM-41 and a microporous carbon made from a polymerized alcohol. This carbon silica composite (CSC) was further functionalized by various water-soluble metal salts through single salt impregnations as well as dual salt incorporation. The effectiveness of salt-functionalized CSCs was measured via breakthrough capacities for low concentrations of NH3 and SO2. Materials with high adsorption performance for both of these targets, representative of acidic and basic gases, were obtained with potential broad-scale, commercial applicability for a diverse set of adsorbates. In brief, the incorporation of potassium carbonate increased the alkalinity of the adsorbent thereby promoting SO2 adsorption. Similarly, the incorporation of zinc chloride increased the acidity of the adsorbent resulting in enhanced NH3 adsorption. The addition of K2CO3 and ZnCl2 on the same adsorbent was shown to consolidate high adsorption performance for both of these toxic industrial chemicals (TICs). Interestingly, upon incorporation of the two water-soluble impregnants, a reaction to form an insoluble precipitate within the substrate via in-pore synthesis occurs. This dual salt functionalization leading to the in-pore synthesis of insoluble precipitates was also performed using various combinations of metal chlorides with potassium salts. Differences in the pH of salt-incorporated substrates provided an understanding of cation and anion dependence in functionalized materials for NH3 and SO2 adsorption. With MOFs, a characterization analysis was performed to interpret the degradation (or lack thereof) of chemical bonds within the framework that were susceptible to water adsorption.

No description available.

In this work, we probe the mechanisms of excitation and subsequent recombination of electron-hole pairs in the mixed bandgap perovskite crystal CH₃NH₃Pb(I_1-xBr_x)₃, x=0-0.33, using ultrafast spectroscopies. The perovskite grain size can be tuned to reflect the size of intrinsic iodide-rich nuclei, which depend strongly on coordination of PbI₂ with the deposition solvent prior to spin-casting. These iodide-rich nuclei, visualized for the first time in SEM and STEM-EDS, serve as low-bandgap recombination centers within the mixed crystal. Picosecond time-resolved photoluminescence (tr-PL) reveals that higher bromide compositions and smaller intrinsic nuclei maximize carrier lifetime. Introduction of bromide also affects absorbance: as bromide composition increases, the bulk bandgap increases, shifting the absorbance band edge into the visible range. While femtosecond transient absorption spectroscopy (TAS) reveals that lifetimes of carrier trapping and charge injection are independent of bromide content, the lifetime of electron thermalization shortens with added bromide, indicating that bromide introduction improves phonon transport as well as carrier transport. With an understanding of intrinsic compositional variations in mixed halide perovskites, the unique carrier transport properties of these material may be realized in future solar cells and light-emitting diodes.

<p>Visible light therapy (400-700 nm), i.e. photodynamic therapy, phototherapy, etc. has been used experimentally and clinically for treatment in acne, cancer, wounds, jaundiced neonates and other ailments. In the wake of increasing antibiotic resistance, the application of blue light (400-500 nm) as an antimicrobial strategy is appealing. Previous studies have elucidated differences on the responses of bacteria to irradiation with blue light (or blue light irradiation-BLI), ranging from a decrease in growth for some species, to stimulating proliferation in others. Although effective against a range of Gram-positive pathogens, BLI appears to be less effective at targeting Gram-negative bacteria and the basis of this phenomenon remains unknown.</p> <p>Studies evaluating the phototoxic effect of BLI on bacteria revealed that endogenous photosensitizers absorbing blue light lead to the formation of reactive oxygen species (ROS). In turn, these ROS, specifically singlet oxygen, can have a cytotoxic effect. Conversely, significant literature documents the ability of bacteria to sense and respond to blue light, via the use of BLUF (sensor of blue light using FAD-flavin adenine dinucleotide) domain-containing proteins. Much of the work that has been done has focused on bacteria early in its life cycle, but it is bacteria in later stages of growth that are responsible for causing infections and diseases.</p> <p>Through this work the growth phase dependencies on reductions in Gram-negative <i>Escherichia coli</i> were defined. The reduction differences between non-pathogenic and pathogenic <i>E. coli</i> strains were determined. The endogenous photosensitizer that is involved in the BLI-induced response at the 455 nm wavelength was also identified. Light parameters such as wavelength, energy dose, and the energy flux affect reductions in growth; findings from modulating these parameters were used to further enhance reductions in <i>E. coli</i> post-BLI. Through these studies and additional kinetic analysis, a proposed a model has been developed to describe the observed BLI reductions.</p>

<p> Virial coefficients are unique thermodynamic properties of a system owing to their link be- tween interactions at the molecular level to macroscopic quantities such as the pressure. In this work, we take advantage of this feature and compute virial coefficients of a variety of systems by performing simulation studies. The nature and quality of the interaction potential used in such studies highly affects the quality of the resulting virial coefficients. Therefore, we have employed <i>ab initio</i> based interaction potentials that are state-of-the-art and have been developed using high quality quantum chemistry calculations. Naturally, the complexity of such simulations is a strong motivator for the development of algorithms that are highly efficient and yield precise results. In this regard, we have developed two efficient and novel algorithms for use in Path Integral Monte Carlo (PIMC), a method used to incorporate nuclear quantum effects in virial coefficient calculations for diatomic molecules. We have successfully applied these algorithms to compute virial coefficients including quantum effects or, in short, quantum virial coefficients, for H₂, N₂ and O₂ sys- tems. In addition to applying these algorithms to study diatomic molecules, we have also investigated other algorithms like PIMC using semi-classical beads and compared them to conventional PIMC, for He as well as N₂ systems. Finally, we have also evaluated virial coefficients including quantum corrections, or, in short, semi-classical virial coefficients for a latest <i>ab initio </i> potential of water.</p>

Despite the popular belief that crude oil is a mixture of hydrocarbons that floats on the surface of water, tar balls continue to wash up on beaches from the sea floor years after the Deep Water Horizon oil spill. This is because of the rarely studied weathering effects that occur during deep sea spills. While the evaporative weathering process of oil at the waters surface has been studied, no currently implemented models assess the weathering effects of dissolution within the water column. The evaporative effects at the sea surface and the dissolution of soluble components within droplets located in the water column leave a heavy fraction of oil that may sink. Laboratory experiments from previous work used hydrocarbon-like chemicals to form binary model oils. In contrast, experiments presented in this work use crude oil amended model oil (COA-MO) mixtures where the sinking of heavy fractions of crude oil does occur. The evaporative weathering binary model, when applied to COA-MO mixtures, was able to predict the sinking times of oil droplets using physical data of the three individual components of the mixture (crude oil, a light volatile, and heavy non-volatile chemical). The dissolution bonary model was able to predict the sinking times of COA-MO mixtures while submerged under water. A range of experimentally derived dissolution time constant, K, was obtained which could be applied to a broad spectrum of real world oils where the solubility of individual crude oil components varies greatly.

Nanofiber particle/polymer cathode mats, with an average fiber diameter in the 400-600 nm range, were fabricated by electrospinning mixtures of a proton exchange polymer and commercial Pt/C catalyst particles, incorporated into membrane-electrode-assembles (MEAs), and evaluated in a fuel cell test fixture. Nanofiber cathodes with a commercial Pt/C catalyst and a binder of Nafion and poly(acrylic acid) (PAA) were shown to work extremely well in hydrogen/air fuel cell MEAs. As compared to conventional painted cathode MEAs, they had a higher electrochemical surface area (39-45 m2/g for nanofibers vs. 30-36 m2/g for painted), higher mass activity (~0.16 A/mgPt vs. 0.11 A/mgPt), and higher power output (e.g., 396 mW/cm2 at 0.65 V with H2/air at ambient pressure and a cathode Pt loading of 0.10 mg/cm2 vs. 292 mW/cm2). MEA power output with nanofiber cathodes was insensitive to changes in fiber diameter and Nafion/PAA binder composition, indicating that precise control of these parameters is not required for commercial scale-up. The nanofiber electrode architecture did not significantly change the way fuel cell cathodes degraded during load cycling tests (Pt dissolution tests), but the nanofibers had a clear advantage in power retention after accelerated durability tests that simulate start-stop cycling (carbon corrosion tests). A second generation of nanofiber cathodes was fabricated with a binder of Nafion and poly(vinylidene fluoride) (PVDF). The addition of PVDF altered the hydrophilicity/hydrophobicity of the cathode and slowed the deleterious effects of carbon corrosion. Carbon corrosion rates were the same for both nanofiber and painted Nafion/PVDF cathodes, but the effect of corrosion on power output was much less severe for nanofiber cathodes. Cathodes with a low Nafion/PVDF ratio produced low power initially but the power density increased over the course of a carbon corrosion test. This unusual result was associated with the formation of hydrophilic carbon oxidation species at the catalyst support surface, which increased the hydrophilicity of the cathode.

The novel consumables studied were abrasive-free copper CMP slurries and high-pressure micro jet technology as an alternative to diamond pad conditioning. Abrasive-free slurries were found to be effective in copper removal and were shown to demonstrate similar removal rate and coefficient of friction (COF) trends as conventional abrasive slurry CMP, while possibly decreasing wafer defects. Fundamental information from the friction spectrum indicated that the periodicity of the cyclic passivation layer formation and removal in copper CMP may be on the order of 10 milliseconds. HPMJ technology was found to be a possible alternative to diamond conditioning with some decrease in removal rate.A controlled atmosphere polishing (CAP) system was used and demonstrated that gaseous additives can feasibly be introduced real-time during a polish. Addition of complexing agents were found to increase removal rates, however it was found that direct etching of copper oxide on the copper surface was not the primary mechanism responsible for removal rate increases during CMP with low oxidant concentrations. Alternatively, it was found that direct etching of the copper oxide is significant in systems containing much higher oxidant concentrations, 1 wt% hydrogen peroxide for example. It was for this reason that a third removal step, chemical dissolution, was added to the two-step removal rate model.The remainder of the work in this dissertation was concerned with characterizing and modeling the copper oxidation and copper oxide dissolution steps of the three-step model separately and applying the appropriate expressions into the CMP removal rate model. The copper oxidation process was found to demonstrate oxide growth, or passivation behavior, at pH of 5 and higher. The oxide growth process was governed by oxidized copper migration through the oxide film. The copper oxide dissolution process was controlled by dissolution of the complexing agent through a dissolution byproduct film. These steps were characterized and applied to the three-step removal rate and predicted removal rate data quite well with one fitting parameter that varied within one order of magnitude. Two real-time experimental measurements, COF and leading pad temperature, can be input into the model to predict removal rates during a polish.

Hafnium based oxides and silicates are promising high-κ dielectrics to replace SiO₂ as gate material for state-of-the-art semiconductor devices. However, integrating these new high-κ materials into the existing complementary metal-oxide semiconductor (CMOS) process remains a challenge. One particular area of concern is the use of large amounts of HF during wet etching of hafnium based oxides and silicates. The patterning of thin films of these materials is accomplished by wet etching in HF solutions. The use of HF allows dissolution of hafnium as an anionic fluoride complex. Etch selectivity with respect to SiO₂ is achieved by appropriately diluting the solutions and using slightly elevated temperatures. From an ESH point of view, it would be beneficial to develop methods which would lower the use of HF. The first objective of this study is to find new chemistries and developments of new wet etch methods to reduce fluoride consumption during wet etching of hafnium based high-κ materials. Another related issue with major environmental impact is the usage of large amounts of rinsing water for removal of HF in post-etch cleaning step. Both of these require a better understanding of the HF interaction with the high-κ surface during the etching, cleaning, and rinsing processes. During the rinse, the cleaning chemical is removed from the wafers. Ensuring optimal resource usage and cycle time during the rinse requires a sound understanding and quantitative description of the transport effects that dominate the removal rate of the cleaning chemicals from the surfaces. Multiple processes, such as desorption and re-adsorption, diffusion, migration and convection, all factor into the removal rate of the cleaning chemical during the rinse. Any of these processes can be the removal rate limiting process, the bottleneck of the rinse. In fact, the process limiting the removal rate generally changes as the rinse progresses, offering the opportunity to save resources. The second objective of this study is to develop new rinse methods to reduce water and energy usage during rinsing and cleaning of hafnium based high-κ materials in single wafer-cleaning tools. It is necessary to have a metrology method which can study the effect of all process parameters that affect the rinsing by knowing surface concentration of contaminants in patterned hafnium based oxides and silicate wafers. This has been achieved by the introduction of a metrology method at The University of Arizona which monitors the transport of contaminant concentrations inside micro- and nano- structures. This is the only metrology which will be able to provide surface concentration of contaminants inside hafnium based oxides and silicate micro-structures while the rinsing process is taking place. The goal of this research is to study the effect of various process parameters on rinsing of patterned hafnium based oxides and silicate wafers, and modify a metrology method for end point detection.