Dynamic models of a reactive distillation column have been developed and implemented in this work. A model describing the steady state behavior of the system has been built in a first step. The results from this steady state model have been compared to data provided from an industrial collaborator and the reconciled model formed the basis for the development of a dynamic model. Four controlled and four manipulated variables have been determined in a subsequent step and step tests for the manipulated variables were simulated. The data generated by the step responses was used for fitting transfer functions between the manipulated and the controlled variables. RGA analysis was performed to find the optimal pairing for controller design. Feedback controllers of PID type were designed between the paired variables found from RGA and the controllers were implemented on the column model. Both servo and regulatory problems have been considered and tested.

There are many intensive researches for zinc compounds due to their wide band gaps and potential applications in visible and UV optoelectronic technologies. Zinc nitride is a n-type semiconductor material having a direct band gap, and is not widely studied. Previous papers reported that zinc nitride is a n-type semiconductor having low resistivity and high electron mobility. Its band gap varies from 1.23 eV to 3.2 eV depending on the process condition. In this work, we successfully fabricated zinc nitride p-n junction by heat treatment on zinc nitride films. The threshold voltage of p-n junction is about 1 V. The Zinc nitride films were prepared by reactive RF magnetron sputtering. The as-grown zinc nitride thin film is a n-type material. It is found that the film treated at 300¢J for 3 hours can be changed to a p-type material. The zinc nitride has a very low resistance (2.2¡Ñ10-2 £[-cm) and high carrier concentration (3.88¡Ñ1019 cm-3) after the heat treatment. The optical band gap of zinc nitride was determined as a direct band gap varying from 1.1 eV to 1.6 eV according to the temperature of heat treatment. The zinc nitride was successfully prepared with various electrical characteristics and band gaps by controlling the temperature of heat treatment.

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xi, 150 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Sputtering is a physical vapor deposition (PVD) process used to create thin films, i.e very thin layers of material. To form compounds, such as oxides and nitrides, it may be beneficial to add a reactive gas to the process which is known as reactive sputtering. This thesis focuses on the simulation of the reactive sputtering process and, more specifically, the effect of the process pressure. Two models have been developed. A Monte Carlo model simulates the distribution of sputtered material throughout the chamber. It is based on the binary collision model with initial conditions acquired from simulations in TRIM. The hard-sphere potential is used as interaction potential in the scattering calculations. The effect of the process pressure is studied for two different elements, sulfur and tungsten. It is found that the distribution of material is heavily influenced by the pressure. A high pressure gives a more diffusion-like distribution compared to a low pressure. As the pressure is increased the deposited material’s energy distribution is found to be shifted towards lower energies until it reaches the energy of thermalized atoms. The second model developed is an extended Berg model that incorporates the effect of redeposition of sputtered material on the target, implantation of reactive ions in the target and preferential sputtering. Using simulations the effect of these extensions is discussed. It is found that an increased pressure may eliminate the hysteresis region which has been observed experimentally. Finally an outline is presented on how the two models can be unified into a Berg-model that takes the non-uniform distribution of sputtered material into account.

Leakage of CO₂ saturated fluid along wellbores has critical implications for the feasibility of geologic CO₂ storage. Wells, which are ubiquitous in locations ideal for CO₂ storage, develop leaks (e.g. fractures) for many reasons and at different points in their age. Small leaks pose the most significant risk to geological CO₂ sequestration because they are difficult to detect and provide a direct pathway through which fluid can escape the storage formation. This dissertation shows that due to complex coupling between reaction and flow, leaking wells will tend to self-seal via secondary precipitation of calcium carbonate in the open pathway. Residence time, fluid reactivity, and initial fracture aperture all play a key role in determining the time required to seal the leakage pathway. To test the self-sealing hypothesis, laboratory experiments were conducted to inject reactive fluids into naturally fractured cement. Restriction of the leakage pathway, i.e., the fracture, was inferred from the relationship between flow rate and pressure differential. Precipitation was observed in both constant flow rate and constant pressure differential experiments. In the former precipitation resulted in an increasing pressure differential, while precipitation caused a decrease in flow rate in the latter. Analysis by electron microprobe and x-ray diffraction, and corroborated with effluent chemical analysis, showed that the reacted channel was depleted in calcium and enriched in silicon relative to the original material. The remaining silicon rich material prevents widening of the reacted channel and development a self-enhancing (e.g. wormhole) behavior. Self-limiting behavior is caused by calcium mixing with carbonate ions in high pH slow flow regions where local residence time is large and calcium carbonate is insoluble. Secondary precipitation initially develops next to the reacted channel and then across the fracture surface and is the source of pathway restriction and the self-sealing behavior. Results from the experiments are used to develop a simple analytical model to forecast well scale leakage. Future work is needed to test a broader range of experimental conditions (e.g. brine salinity, cement formulations, cement-earth interface, effect of CO₂ saturation, pressure, and temperature), to improve our understanding of both the fundamental behavior and the leakage model. / text

A reactive distillation column for the alkylation of benzene with long chain linear olefin was studied. The study involved design, construction, experimentation, and simulation of the column. Establishing the design required study of reaction rates, thermodynamic relationships, and packing structures. A heuristic was developed for the design of such columns. This heuristic involved estimating an amount of catalyst loading and subsequently determining the operating parameters for a column. This method is particularly applicable to systems with high concentrations of inert feeds. A column was constructed following the design. Data was collected from the column and compared to simulations. The simulations were performed with Aspen Plus RADFRAC. In this manner, the data was used to validate the commercial steady state models for reactive distillation. In addition, dynamic simulations of the system were performed. These dynamic simulations provided insight into more design considerations. For example, steady state simulations indicated an optimal feed stage based on steady state conversion of the olefin. However, the dynamic simulations showed a potential disadvantage to the utilization of the optimal feed stage. With some disturbances, a column configured with the feed stage with the highest steady state conversion also deviated from the steady state faster and with greater amplitude than other configurations. These considerations were further explored in developing a control scheme for reactive distillation columns. Control of reactive distillation differs from traditional distillation in that one control variable is conversion. Traditional distillation generally focuses on production rates and product purity. To this end, control schemes were analyzed and dynamic simulations were performed. These simulations showed an advantage to a variable pairing in which duty is paired with conversion. The conversion was inferred from a stage temperature in the reactive zone. In addition, distillate rate may be paired with product composition. In conclusion, the reactive distillation column design for long chain olefin alkylation of benzene requires careful estimation of catalyst requirements and valid simulation tools. In addition, dynamic response should be considered in the design. Finally, a simple inferential control scheme may be adequate. / text

Exploration into the use of aptamers as cross-reactive receptors was the focus of this work. Cross-reactivity is of interest for developing assays to identify complex targets and solutions. By exploiting the simple chemistries of aptamers, we hope to introduce a new class of receptors to the science of molecular discrimination. This manuscript first addresses the use designed aptamers for the identification of variants of HIV-1 reverse transcriptase. In this research aptamers were immobilized on a platform and were used to discriminate four variants of HIV-1 reverse transcriptase. It was found that not only could the array discriminate HIV-1 reverse transcriptase variants for which aptamers were designed, it would also discriminate variants for which no aptamers exist. A panel of aptamers was used to discriminate four separate cell lines, which were chosen as examples of complex targets. This aptamer panel was used to further explore the use of aptamers as cross-reactive sensors. Forty-six aptamers were selected from the literature that were designed to be specific to cells or molecules expected to be in the surface of cells. This panel showed differential binding patterns to each of the cell types, displaying cross-reactive behavior. During the course of this research, we also developed a novel ratiometric method of using aptamer count derived from next-generation sequencing as a method for discrimination. This is in lieu of the more commonly used fluorescent signals. Finally the use of multiple signals for pattern recognition routines was further explored by running various models using artificial data. Various situations were applied to replicate different possible situation which might arise when working with macromolecular interactions. The purpose of this was to advance the communities understanding and ability to interpret results from the pattern recognition methods of PCA and LDA. / text

Accurate models for the mixing of fuel and oxidizer at small, unresolved flow length scales are critical to the predictive skill of large eddy simulation (LES) of turbulent combustion. Subfilter scalar variance and subfilter scalar dissipation rate are important parameters in combustion modeling approaches based on a conserved scalar, but are prone to numerical and modeling errors due to the nature of practical LES computations. This work examines the errors incurred in these models using a novel method that couples LES scalar modeling with direct numerical simulation (DNS) of homogeneous isotropic turbulence and offers modeling and numerical techniques to address these errors. In the coupled DNS-LES method, DNS velocity fields are evolved simultaneously with LES scalar fields. The filtered DNS velocities are supplied to the LES scalar equations, instead of solving the LES momentum equations. This removes the effect of errors in the filtered scalar evolution from the scalar modeling analysis. Results obtained using the coupled DNS-LES approach, which permits detailed study of physics-related and numerical errors in scalar modeling, show that widely used algebraic dynamic models for subfilter scalar variance lack accuracy due to faulty equilibrium modeling assumptions and sensitivity to numerical error. Transport equation models for variance show superior performance, provided that the scalar dissipation rate model coefficient is set appropriately. For this purpose, a new dynamic approach for nonequilibrium modeling of subfilter scalar dissipation rate is developed and validated through a priori tests in an inhomogeneous jet flow and using the coupled DNS-LES method for assessment of numerical error effects. Explicit filtering is assessed as means to control numerical error in LES scalar modeling and the scalar equations are reformulated to account for the explicit filtering technique. Numerical convergence of the mean subfilter scalar variance prediction with increasing grid resolution is demonstrated. / text

Curcumin is one of the major curcuminoids produced by the ginger family Zingiberaceae. These curcuminoids possess pharmacological properties that include anticancer activities. We have evaluated some synthetic curcumin analogues that have shown potential as anticancer drugs. These antineoplastic agents bearing the 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore are electrophiles which are designed to preferentially react with sulfhydryl groups present in proteins as opposed to amino and hydroxyl groups present in DNA. In previous pilot studies, three derivatives examined in this thesis showed inhibition towards human cancer cell lines such as Molt 4/C8 and CEM T-lymphocytes. In this thesis work, I determined the cytotoxicity of these derivatives and curcumin towards human colon cancer (HCT-116) cells and also normal colon epithelial (CRL-1790) cells, and examined the possible mechanism(s) involved. I hypothesized that they act via induction of reactive oxygen species (ROS) which elicit a transient surge of mitochondrial ROS generation and a phenomenon known as ROS-induced ROS release (RIRR), along with the mitochondrial permeability transition (MPT) and mitochondrion –dependent apoptosis. I asked whether these agents react with some of the key protein thiols in the mitochondria whose oxidation/alkylation results in mitochondrion - dependent apoptosis. NC-2109 and NC-2346 were found to be potent cytotoxic agents based on their GI50 values of 0.87 ± 0.38 μM and 0.90 ± 0.22 μM, respectively, and were more potent than the anticancer drug 5-fluorouracil (GI50 = 5.47 ± 0.55 μM) and curcumin (GI50 = 3.50 ± 0.36 μM). However NC-2109 was found to have a better selectivity towards cancer cells over normal cells (a selectivity index of 18.81 versus 5-FU, curcumin and NC-2346 which had selectivity indices of 1.87, 16.75 and 4.61, respectively). In the investigations of the mechanisms involved, both curcumin and curcumin analogues were able to induce mitochondrial ROS production. Moreover, curcumin and its synthetic counterparts showed a biphasic ROS profile which is most characteristic of RIRR. Treatment with these agents also led to the disruption of the mitochondrial membrane potential, suggesting oxidation of protein thiols and the opening of the mitochondrial permeability transition pore which is an important step to initiate mitochondria-directed apoptosis. This possibility was confirmed based on GSSG/GSH ratios, since curcumin, NC-2346 and NC-2109 all produced a higher GSSG/GSH ratio than the controls. In addition to their ability to depolarize the mitochondrial membrane in HCT-116 cells, that these molecules acted via the mitochondrial pathway were further authenticated based on their ability to induce mitochondrial swelling in rat liver mitochondria. In another part of this thesis I evaluated the involvement of the critical thiol protein adenine nucleotide translocase (ANT), a bifunctional protein that plays a central role in mitochondrial apoptosis. ANT has four different isoforms; ANT1 and ANT3 are proapoptotic, while ANT2 and ANT4 are antiapoptotic and are overexpressed in cancer states. A combination approach using ANT2 siRNA however did not conclusively show whether these agents acted synergistically with ANT2 knockdown to potentiate mitochondria-mediated cell death. An alternative combination approach was the use of carboxyatractyloside (CAT) which binds to and retains ANT in its ‘c’ conformation, exposing thiols and potentially driving a cell towards programmed cell death. The presence of CAT enhanced the ability of curcumin and its synthetic analogs to collapse the mitochondrial membrane potential, an important step in mitochondrial-mediated apoptosis. In conclusion, curcumin and the curcumin analogue NC-2109 were found to be cytotoxic in vitro, towards HCT-116 cells and also showed good selectivity. In addition, these two molecules were found to be ROS inducers, and coincidentally oxidized cellular thiols and caused depolarization of the mitochondrial membrane potential. The results support a mechanism of mitochondrial-mediated cell death upon MPT pore formation (mitochondrial swelling), perhaps involving ANT2. This conclusion was further supported by the potentiation of cell death in the presence of the ANT2 inhibitor, CAT.

Σε κάθε Σύστημα Ηλεκτρικής Ενέργειας η ηλεκτρική ισχύς έχει δύο συνιστώσες: Την ενεργό, η οποία σχετίζεται με το παραγόμενο έργο και την άεργο, η οποία δε σχετίζεται με την παραγωγή έργου, αλλά συνεισφέρει σε απώλειες και πτώση τάσεως. Για να αποφύγουμε αυτά τα αρνητικά, στοχεύουμε στη μείωση της αέργου ισχύος, επιτυγχάνοντας έτσι βελτίωση του συντελεστή ισχύος. Με την πάροδο του χρόνου, τα επίπεδα αρμονικών τάσεων και ρευμάτων αυξάνονται συνεχώς, δημιουργώντας έντονα προβλήματα στα Συστήματα Ηλεκτρικής Ενέργειας. Λαμβάνοντας υπ’ όψιν στην ανάλυση ροής ισχύος ενός κυκλώματος την επίδραση των ανώτερων αρμονικών τάσης και ρεύματος, η βελτίωση του συντελεστή ισχύος γίνεται πολύπλοκη διαδικασία, ειδικά στην περίπτωση μη ιδανικής πηγής (μη μηδενική εσωτερική σύνθετη αντίσταση). Σκοπός της διπλωματικής εργασίας είναι η αναζήτηση τεχνικών περιορισμού της αέργου ισχύος, αφού πρώτα συσχετισθεί με τις ανώτερες αρμονικές τάσεως και ρεύματος. Γενικά, το πρόβλημα περιγράφεται και αναλύεται με διάφορες θεωρίες ισχύος και λύνεται με την τοποθέτηση κυκλωμάτων που επιτυγχάνουν αντιστάθμιση της αέργου ισχύος. Αρχικά αναφέρεται η περίπτωση βελτίωσης του συντελεστή ισχύος θεωρώντας ιδανική πηγή (μηδενική εσωτερική σύνθετη αντίσταση) με ημιτονοειδή τάση εξόδου και γραμμικό φορτίο. Σε αυτή την απλή περίπτωση, ένας πυκνωτής είναι ικανός να αντισταθμίσει πλήρως την καταναλούμενη από το φορτίο άεργο ισχύ. Στη συνέχεια εξετάζονται τα περιθώρια βελτίωσης του συντελεστή ισχύος σε συστήματα με: • Ιδανική, μη ημιτονοειδή πηγή τροφοδοσίας και γραμμικό φορτίο • Μη ιδανική, μη ημιτονοειδή πηγή τροφοδοσίας και γραμμικό φορτίο Στην πρώτη περίπτωση, η τοποθέτηση απλά ενός πυκνωτή παράλληλα προς το φορτίο μπορεί να βελτιώσει το συντελεστή ισχύος του φορτίου μέχρι ενός σημείου, ο οποίος λαμβάνει εν γένει τιμές μικρότερες της μονάδας. Υπάρχει δυνατότητα βελτίωσης του συντελεστή ισχύος μέχρι και τη μονάδα, χρησιμοποιώντας έναν πιο πολύπλοκο αντισταθμιστή. Στην πρώτη αυτή περίπτωση, η τιμή του αντισταθμιστή μπορεί να βρεθεί και αναλυτικά, ενώ στη δεύτερη περίπτωση η τιμή του πυκνωτή αντιστάθμισης υπολογίζεται μόνο με τη βοήθεια ενός επαναληπτικού αλγορίθμου. / In any power system electrical power has two components: active, which is related to the work done and reactive, which is not associated with the production of work, but contribute to losses and voltage drop. To avoid these negative, we aim to reduce reactive power, thus improving the power factor. Over time, the levels of harmonic voltages and currents are growing, creating severe problems in power systems. Considering the power flow analysis of a circuit the influence of higher harmonic voltage and current, improving the power factor is a complex process, especially in the case of non-ideal source (non-zero internal impedance). The purpose of this thesis is to find mitigation techniques reactive power, after having been associated with higher voltage and current harmonics. Generally, the problem is described and analyzed with various theories of power and is solved by placing circuits achieve reactive power compensation. Initially, the case for improving the power factor assuming ideal source (zero internal impedance) with sinusoidal output voltage and linear load. In this simple case, a capacitor is able to compensate fully consumed by the load reactive power. Then examine the scope for improving the power factor systems: • Ideal, non-sinusoidal power and linear load • Not ideal, non-sinusoidal power and linear load In the first case, the simple placement of a capacitor in parallel to the load can improve the power factor of the load up to a point, which generally takes values ​​smaller unit. Is it possible to improve the power factor up to the unit, using a more complex equalizer. In the first case, the value of the compensator can be found analytically, while in the second case the value of the compensation capacitor is calculated only using an iterative algorithm.