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This thesis offers modeling of a newly discovered gain mechanism for various photodetection applications. Conventional avalanche photodetectors have been in use for the past four decades with impact ionization being the underlying carrier multiplication mechanism.However, tradeoff between sensitivity, dynamic range and bandwidth are some of the drawbacks of the present day photodetection technology. The newly discovered cycling excitation process (CEP) can be a potential candidate to address these issues with linear photo response, single photon sensitivity and high gain bandwidth product. The key feature of CEP is introduction of counter dopants in p-n junction silicon diode, with which the efficiency of auger excitation can be enhanced to great extent by facilitating relaxation of k selection rule. Higher uncertainty in k spaces dictates localization of carriers in real space. Hence, an initial hot carrier can excite electron-hole pair between localized states (e.g. from states closer to valence band to states closer to conduction band) at much lower bias. Another essential component of CEP is phonon/field assisted tunneling from localized states to mobile bands. Contrary to other photodetectors, phonons, actually, play a positive role in achieving gain. Experimentally gain of ~4000 at only 4V have been achieved in the CEP test structure along with photo response dependence on input light power, which is helpful for photon number resolving. Temperature dependent measurement also shows the positive role of phonons. Density functional theory calculation shows the change in band structure with doping bulk crystalline silicon with boron (B) and phosphorous (P) simultaneously. Comparison of density of states exhibits existence of states inside band gap. Furthermore, charge density plot clearly demonstrates electron and hole localization centered around P and B atoms respectively. Hence, highly counter doping with BP atoms turns the crystalline silicon into a quasi-diso

This thesis offers modeling of a newly discovered gain mechanism for various photodetection applications. Conventional avalanche photodetectors have been in use for the past four decades with impact ionization being the underlying carrier multiplication mechanism.However, tradeoff between sensitivity, dynamic range and bandwidth are some of the drawbacks of the present day photodetection technology. The newly discovered cycling excitation process (CEP) can be a potential candidate to address these issues with linear photo response, single photon sensitivity and high gain bandwidth product. The key feature of CEP is introduction of counter dopants in p-n junction silicon diode, with which the efficiency of auger excitation can be enhanced to great extent by facilitating relaxation of k selection rule. Higher uncertainty in k spaces dictates localization of carriers in real space. Hence, an initial hot carrier can excite electron-hole pair between localized states (e.g. from states closer to valence band to states closer to conduction band) at much lower bias. Another essential component of CEP is phonon/field assisted tunneling from localized states to mobile bands. Contrary to other photodetectors, phonons, actually, play a positive role in achieving gain. Experimentally gain of ~4000 at only 4V have been achieved in the CEP test structure along with photo response dependence on input light power, which is helpful for photon number resolving. Temperature dependent measurement also shows the positive role of phonons. Density functional theory calculation shows the change in band structure with doping bulk crystalline silicon with boron (B) and phosphorous (P) simultaneously. Comparison of density of states exhibits existence of states inside band gap. Furthermore, charge density plot clearly demonstrates electron and hole localization centered around P and B atoms respectively. Hence, highly counter doping with BP atoms turns the crystalline silicon into a quasi-diso

Molecular motions of proteins and their flexibility induce conformational states required for enzyme catalysis, signal transduction, and protein-protein interactions. However, the mechanisms for protein transitions between conformational states are often poorly understood, especially in the millisecond to microsecond range where conventional optical techniques and computational modeling are most limited. To investigate the microsecond dynamics of enzymes, single-walled carbon nanotube – field-effect transistors (SWCNT-FETs) were used as single-molecule biosensors. The SWCNT-FETs have sufficient sensitivity and bandwidth to monitor the conformational motions and processivity of an individual cAMP-dependent protein kinase A (PKA) molecule. Protein attachment is accomplished by functionalizing a SWCNT-FET device with a single protein and measuring the conductance versus time through the device as it is submerged in an electrolyte solution. PKA-functionalized nanocircuits elucidated the time PKA spent traveling between three different conformational motions upon binding of its two substrates. To generalize this approach for the study of a wide variety of proteins at the single-molecule level, this dissertation investigates the bioconjugation process to determine and isolate the key parameters required for functionalizing a SWCNT with a single protein. Further analysis into the parameters implicated in the thiol-maleimide bioconjugation step of the SWCNT-FET device fabrication proved an exhausting effort. We developed improved linker molecules, anthracene maleimide, for attachment of three different proteins to the SWCNT and a new derivative of maleimide providing a solution to overcome side reactions associated with the reducing agent, tris(2-carboxyethyl)phosphine (TCEP). Protein purity and presence of detergent proved to play key roles in preventing nanocircuit surface fouling. An alternative bioconjugation method, utilizing an azide-functionalized hen egg-white lysoz

Molecular motions of proteins and their flexibility induce conformational states required for enzyme catalysis, signal transduction, and protein-protein interactions. However, the mechanisms for protein transitions between conformational states are often poorly understood, especially in the millisecond to microsecond range where conventional optical techniques and computational modeling are most limited. To investigate the microsecond dynamics of enzymes, single-walled carbon nanotube – field-effect transistors (SWCNT-FETs) were used as single-molecule biosensors. The SWCNT-FETs have sufficient sensitivity and bandwidth to monitor the conformational motions and processivity of an individual cAMP-dependent protein kinase A (PKA) molecule. Protein attachment is accomplished by functionalizing a SWCNT-FET device with a single protein and measuring the conductance versus time through the device as it is submerged in an electrolyte solution. PKA-functionalized nanocircuits elucidated the time PKA spent traveling between three different conformational motions upon binding of its two substrates. To generalize this approach for the study of a wide variety of proteins at the single-molecule level, this dissertation investigates the bioconjugation process to determine and isolate the key parameters required for functionalizing a SWCNT with a single protein. Further analysis into the parameters implicated in the thiol-maleimide bioconjugation step of the SWCNT-FET device fabrication proved an exhausting effort. We developed improved linker molecules, anthracene maleimide, for attachment of three different proteins to the SWCNT and a new derivative of maleimide providing a solution to overcome side reactions associated with the reducing agent, tris(2-carboxyethyl)phosphine (TCEP). Protein purity and presence of detergent proved to play key roles in preventing nanocircuit surface fouling. An alternative bioconjugation method, utilizing an azide-functionalized hen egg-white lysoz

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Fluid Catalytic Cracking (FCC) units are widely used in the oil refining industry to crack low value hydrocarbons into a range of higher value hydrocarbons including gasoline. Because of its feed processing flexibility, the FCC process is considered a primary conversion unit in an integrated refinery and optimal FCC operation can have a significant impact on the refinery profitability. Because of its important role in the refinery, the FCC process has recently attracted renewed interest both from academia and industry, with the main emphasis on better understanding and operating the process. In general, several possible alternatives can usually be postulated or envisioned to realize operational improvements, and the critical task is then to rank order these alternatives. Rank ordering the available alternatives requires the utilization of suitable: 1. process models describing each alternative, 2. tools to quantitatively assess the operational performance achievable with each alternative. "Operational performance" here refers to the quality of closed loop process response. The different alternatives have often been analyzed and compared through extensive simulations. However, because of stringent environmental and economic requirements, most industrial plants, including the FCC process have evolved into highly complex and integrated processes and ranking through simulation might be infeasible. In ranking design alternatives through simulation, two crucial factors must be considered if the conclusions drawn from such studies are to be reasonably reliable: • Detailed case studies need to be conducted for all the alternatives. These case studies typically require considering the effect of a wide range of disturbances, inputs, operating conditions, model structures and parameters, control structures and parameters. It might be necessary to examine many hund

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Fluid Catalytic Cracking (FCC) units are widely used in the oil refining industry to crack low value hydrocarbons into a range of higher value hydrocarbons including gasoline. Because of its feed processing flexibility, the FCC process is considered a primary conversion unit in an integrated refinery and optimal FCC operation can have a significant impact on the refinery profitability. Because of its important role in the refinery, the FCC process has recently attracted renewed interest both from academia and industry, with the main emphasis on better understanding and operating the process. In general, several possible alternatives can usually be postulated or envisioned to realize operational improvements, and the critical task is then to rank order these alternatives. Rank ordering the available alternatives requires the utilization of suitable: 1. process models describing each alternative, 2. tools to quantitatively assess the operational performance achievable with each alternative. "Operational performance" here refers to the quality of closed loop process response. The different alternatives have often been analyzed and compared through extensive simulations. However, because of stringent environmental and economic requirements, most industrial plants, including the FCC process have evolved into highly complex and integrated processes and ranking through simulation might be infeasible. In ranking design alternatives through simulation, two crucial factors must be considered if the conclusions drawn from such studies are to be reasonably reliable: • Detailed case studies need to be conducted for all the alternatives. These case studies typically require considering the effect of a wide range of disturbances, inputs, operating conditions, model structures and parameters, control structures and parameters. It might be necessary to examine many hund

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Fluid Catalytic Cracking (FCC) units are widely used in the oil refining industry to crack low value hydrocarbons into a range of higher value hydrocarbons including gasoline. Because of its feed processing flexibility, the FCC process is considered a primary conversion unit in an integrated refinery and optimal FCC operation can have a significant impact on the refinery profitability. Because of its important role in the refinery, the FCC process has recently attracted renewed interest both from academia and industry, with the main emphasis on better understanding and operating the process. In general, several possible alternatives can usually be postulated or envisioned to realize operational improvements, and the critical task is then to rank order these alternatives. Rank ordering the available alternatives requires the utilization of suitable: 1. process models describing each alternative, 2. tools to quantitatively assess the operational performance achievable with each alternative. "Operational performance" here refers to the quality of closed loop process response. The different alternatives have often been analyzed and compared through extensive simulations. However, because of stringent environmental and economic requirements, most industrial plants, including the FCC process have evolved into highly complex and integrated processes and ranking through simulation might be infeasible. In ranking design alternatives through simulation, two crucial factors must be considered if the conclusions drawn from such studies are to be reasonably reliable: • Detailed case studies need to be conducted for all the alternatives. These case studies typically require considering the effect of a wide range of disturbances, inputs, operating conditions, model structures and parameters, control structures and parameters. It might be necessary to examine many hund