A novel technique by employing a capacitance displacement measurement system to measure the post-weld-shift (PWS) caused by laser welding in the butterfly-type laser diode module packaging process is proposed. Reduction of the PWS is an important issue in developing low-cost and high-performance semiconductor laser module. Prior to the reduction and compensation of the PWS, a measurement system of PWS must be constructed. In comparison to the high-magnification camera with image capturing system (HMCICS) limited in resolution of 0.07£gm due to its pixels, a measurement system with a higher resolution of 0.0254£gm is used. During the measurement procedure, the PWS of the ferrule probed by the sensors is converted into the fiber misalignment shifts. The coupling efficiency can be improved over 70% after compensation. The result indicates that the PWS can be qualitatively measured and quantitatively computed.

The existence of Room Temperature Ionic Liquids (RTILs) has been known for a long time, but only recently have they been pulled to the forefront of chemical research. This increase in attention can be attributed to a keen interest in their intrinsic properties for a wide variety of potential applications. RTILs have been used as alternative solvents for organic synthesis as well as catalysis, as well as supports for the purification or extraction of metals. Being ionic in nature and liquid at temperatures below 100°C, RTILs lend themselves to the electrochemist. As a result, they have been looked at for use in electrochemical systems such as high capacity batteries and supercapacitors. Due to their extremely high density of charge carriers relative to more well-known aqueous electrochemical systems, a new theoretical approach must be taken. Currently, a large gap exists between theoretical approaches and experimental results. The work contained within this thesis aims to provide insight into the interface between a RTIL and an electrified gold electrode.

Extraction of oil and gas can cause reduction in pore pressure, occasionally resulting in subsequent compaction that forms a surface subsidence bowl, especially in shallow reservoirs. In the last 10 years, there has been over 10 feet of subsidence in parts of the Lost Hills oil field in California (Bruno et al.,1992). The surface subsidence at Lost Hills not only causes damage to surface facilities and wells, but also reactivates faults and reduces rock permeability. Subsidence makes reservoir optimization difficult. Hence, it is important to assess or predict the surface subsidence and the reasons for subsidence early in the life of an oil field to make an optimization plan. We use jointly the capacitance resistance model (CRM) (Alberoni et al., 2002 and Yousef, et al., 2006) that relies only on injection and production data, and the InSAR satellite imagery of surface subsidence. From CRM simulations, we estimate the connectivity between injectors and producers as well as general water flow directions from individual injectors. We then superimpose well connectivity and InSAR imagery to diagnose the reasons for the subsidence. Using new surface subsidence models, which are based on the continuity equation of CRM and rock mechanics, we are able to predict the average surface subsidence at Lost Hills from the injection and production rates. Our work shows that there was significant volumetric rock damage at Lost Hills and the well connectivity changed dramatically with time because of reservoir compaction and the rock damage. We conclude that for a soft, fragile and nearly- impermeable rock such as the diatomite, high injection rate weakens the rock and creates dynamic water flow tubes or ‘channels’ without providing good pressure support to the reservoir. These high permeability ‘channels’ re-circulate most of the injected water between the injectors and producers. Our CRM/InSAR approach is new and gives insights into the time-dependent and spatially variable fluid flow fields in a relatively shallow waterflood. Consequently, we may be able to suggest optimum water injection strategies to enhance oil production, while minimizing rock damage and surface subsidence. In addition, the proposed surface subsidence models are convenient and reliable to predict the average surface subsidence. / text

Reservoir characterization is very important in reservoir management to plan, monitor, predict and optimize oil production. Reservoir simulation is well-accepted in reservoir management but it requires many inputs, needs months to set up and complete a set of simulation runs, and contains large uncertainty in physical and geological properties. Therefore, simpler methods that provide quick results to complement or substitute reservoir simulation are important in decision making. Capacitance resistance model (CRM) is one of the methods. CRM is an input-output model derived from a continuity equation to quantify producer-injector connection strength during waterflood using solely production data. This work improves the CRM application method for waterflood and develops CRM theories and application methods for other recovery periods such as primary recovery and water-CO2 flood. A West Texas field test was carried out to validate CRM for a waterflood. The CRM fit was evaluated and used to optimize the oil production by changing injection rates. Through this first field experiment, a CRM application procedure was developed. With the CRM optimized injection schedule, the field gained 5372 bbls of additional oil production increase after one year. This research also quantitatively validates the CRM gain and time constant using synthetic fields and compares them to parameters of the streamline model, a complex model with similar purposes to the CRM. The CRM provides similar results as the streamline model with fewer inputs. The CRM was extended to primary recovery and water-CO2 flood. A new CRM equation – the integrated CRM (ICRM) - for primary recovery was developed and validated on many synthetic fields and an Oman field. The model can estimate dynamic pore volume, productivity index and average reservoir pressure that compare closely to simulated values and field knowledge. Additionally, the ability of CRM to quantify injector-producer connection strength and predict fluid production was examined on a synthetic water-CO2 flood field. A new oil production model to be used with CRM application in water-CO2 flood was developed and validated on synthetic data. The model predicts oil production from injection rate and relative permeability. CRM has successfully optimized waterflood on a West Texas field by reallocating the water from ineffective to effective injectors. New interpretations of the CRM parameters enable quantitative validation and integration of the CRM results with other methods. In primary recovery, the ICRM can estimate reservoir properties without requiring well testing which can cause loss of production. The CRM and the new oil production model can quickly characterize water-CO2 flood for short term production monitoring. / text

Graphene has been extensively studied for possible future technical applications due to its unique electronic, transport, and mechanical properties. For practical applications, graphene often needs to be placed in a medium or on a substrate. The interfacial interaction between graphene and other materials can greatly affect the performance of graphene-based devices, but has not been well explored. My thesis research focused on developing a better understanding of the interface of pristine and chemically/mechanically modified graphene sheets with ionic liquids (ILs) as well as amorphous silica (a-SiO₂) surfaces using first principles-based atomistic modeling which combines density functional theory, classical molecular dynamics, and Metropolis Monte Carlo. The major focus of my thesis research was on investigating the interfacial structure and capacitance between graphene and ILs; graphene-based materials and ILs have been regarded as viable candidates for supercapacitor electrodes and electrolytes, respectively. Particular emphasis was placed on elucidating the relative contributions of the electric double layer (EDL) capacitance at the graphene/IL interface and the quantum capacitance of graphene-like electrodes. More specifically, we first determined the microstructure (such as orientation, packing density, cation-anion segregation) of chosen ILs near planar graphene electrodes with various surface charge densities. Based on the calculated IL microstructure for each system, the EDL capacitance was then evaluated with particular attention to the effect of cation-anion size difference. We also examined the influence of the chemical and mechanical modifications of graphene-like electrodes on the supercapacitor performance. Especially, mechanisms underlying chemical doping-induced enhancement of the total interfacial capacitance were addressed through analysis of electrode quantum capacitance changes resulting from electronic structure modifications. A part of my effort was also devoted to examining the binding interaction of graphene with a-SiO₂ (which is not yet clearly understood despite its scientific and technological importance). In particular, we attempted to evaluate quantitatively the adsorption strength of graphene on the a-SiO₂ surface, which has been under debate mainly due to the difficulty of direct measurement. / text

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This thesis reports on a design and modeling of a micro-machined gyroscope. The proposed sensor is a dual mass type, electro-statically driven to primary mode oscillation and senses, capacitively, the output signal. Full decoupling between drive and sense modes minimizes the mechanical crosstalk and based on this a novel gyroscope is designed and modeled which has separate sensing and driving masses. The dual mass gyroscope is designed such that driving and sensing resonant frequency is 23101 Hz with 0% mismatch (in simulation)with quality factor of 31.6227 and bandwidth of 730.51Hz. The gyroscope when actuated in simulation with 25V ac and 10V dc showed sensing capacitance variation of 126aF for 1 rad/s with base capacitance of 244.16fF. To the design of the gyroscope a new semi automatic tool was formulated for the noise analysis and noise based optimization of the resonant MEMS structures. Design of a sensitive gyroscope needs to take into account the noise shaping induced by damping phenomena at micro scale and is critical for optimization. The analysis was further extended to the design of the gyroscope and estimation shows that there is a trade of between the S/N ratio and the sensitivity and the design could be made much better in-terms of S/N by tuning its resonant frequency to 10⁶Hz.

This thesis reports on a design and modeling of a micro-machined gyroscope. The proposed sensor is a dual mass type, electro-statically driven to primary mode oscillation and senses, capacitively, the output signal. Full decoupling between drive and sense modes minimizes the mechanical crosstalk and based on this a novel gyroscope is designed and modeled which has separate sensing and driving masses. The dual mass gyroscope is designed such that driving and sensing resonant frequency is 23101 Hz with 0% mismatch (in simulation)with quality factor of 31.6227 and bandwidth of 730.51Hz. The gyroscope when actuated in simulation with 25V ac and 10V dc showed sensing capacitance variation of 126aF for 1 rad/s with base capacitance of 244.16fF. To the design of the gyroscope a new semi automatic tool was formulated for the noise analysis and noise based optimization of the resonant MEMS structures. Design of a sensitive gyroscope needs to take into account the noise shaping induced by damping phenomena at micro scale and is critical for optimization. The analysis was further extended to the design of the gyroscope and estimation shows that there is a trade of between the S/N ratio and the sensitivity and the design could be made much better in-terms of S/N by tuning its resonant frequency to 10⁶Hz.

Thesis (M.S.)--Ohio University, November, 1999. / Title from PDF t.p.