Dissertations / Theses on the topic 'Gas'

A gradient-independent model of gas fluxes was formulated and tested. The model is built on the relationship between gas flux and the time history of surface gas concentration, known as half-order derivative (HOD), when the transport of the gas in the boundary layer is described by a diffusion equation. The eddy-diffusivity of gas is parameterized based on the similarity theory of boundary layer turbulence combined with the MEP model of surface heat fluxes. Test of the new model using in-situ data of CO2 concentration and fluxes at several locations with diverse vegetation cover, geographic and climatic conditions confirms its usefulness and potential for monitoring and modeling greenhouse gases. The proposed model may also be used for estimating other GHGS fluxes such as methane (CH4) and Water vapor flux. This proof-of-concept study justifies the proposed model as a practical solution for monitoring and modeling global GHGS budget over remote areas and oceans where ground observations of GHGS fluxes are limited or non-existent. One focus of the on-going research is to investigate its application to producing regional and global distributions of carbon fluxes for identifying sinks and sources of carbon and re-evaluating the regional and global carbon budget at monthly and annual time scales.

Currently, almost all new vehicles are equipped with airbags. A common type of airbag inflator is the Heated Gas Inflator (HGI). These inflators are cylindrical shaped canisters that are filled to very high pressures with a gaseous mixture of fuel and air. The mixture is ignited from one or both ends of the cylinder. The resulting high temperatures from combustion heats the excess air, which is then used to inflate the airbag. Once the mixture is ignited, large pressure waves form, traveling along the length of the tube. These waves, inherent to the design of the inflator, do not allow the use of a volume averaged assumption for the combustion chamber. Therefore, it is necessary to use a Computational Fluid Dynamics (CFD) code to model the dynamic nature of the inflator. Commercial CFD codes are readily available that could be used to model the HGI. These codes use the Ideal Gas Law to calculate the properties of the mixture. The high pressures in an HGI do allow for the use of an ideal gas assumption. Instead, a Real Gas equation of state must be used. An existing Airbag Inflator Model that was capable of Real Gas equation of state calculations had been previously created to simulate solid propellant inflators. In order to properly model the wave dynamics in an HGI and include Real Gas calculations, a CFD model has been added to the Airbag Inflator Model. The CFD model must be capable of handling multiple species of gases and be able to properly model the sharp gradients associated with large pressure waves and changes in chemical species. Therefore, a high-resolution shock capturing technique is used to handle the homogeneous part of the governing equations. The non-homogeneous terms of the governing equations are solved using an ordinary differential equations solver. In order to combine the solutions, a time splitting technique is used to combine the solutions from the homogeneous and non-homogeneous parts of the governing equations. The addition of the CFD model to an Airbag Inflator Model with Real Gas equation of state capabilities provides a very useful tool in the design of HGIs. The model can be used to ensure that a design does not produce unexpected large magnitude pressure waves that could possibly cause dangerous mechanical failures. Later models of HGIs have ignitors at each end of the cylinder. The secondary ignitor can be delayed to vary the production rate of the exhaust gasses, depending on the severity of the crash. This time delay is an additional parameter that can have an effect on the wave dynamics in the HGI. The addition of the CFD model to the Airbag Inflator Model provides a fast and economical way to predict the outcome of any change in the design parameters of an HGI.

Gas lift is one of the most common forms of artificial lift, particularly for offshore wells. This is due to its relative downhole simplicity, flexibility, reliability, and ability in operating over a wide range of flow rates with the limited well head space. Generally, Gas lift optimization can reduce the operating cost with increase in the Net Present Value (NPV) and maximization of the recovery from the asset. All of the previous researches have reported that conventional gas lift technologies’ designs have limitations on gas lift valve. Nonetheless, traditional gas lift technologies that were designed and developed in 1950’s do not have resistance when subjected to high temperature and high pressure in subsea wells. This therefore unable the flows of the gas lift to be coherently controlled. Moreover, gas-lifted oil wells can lead to failure unless a smart gas lift valve unit is used in the controlling the amount of the gas inside the tubing string. In this study, an automation gas lift valve unit with the corresponding control line was experimentally simulated on a dedicated apparatus. This enables real-time data on the gas lift valve to the surface to be demonstrated and accordingly analyzed. Under the conventional method of practice the injection pressure of the gas is normally used in operation of the valve. Whereas in this investigation the port size of the gas lift valve was remotely adjusted from the assumed surface using the apparatus. A devoted computer program LabVIEW was also used in determination of the gas passage through the smart gas lift valve, thus distilling the real time data. The results have shown those optimizations are achievable at high gas injection pressure when 87 psi is used and when the valve is 15% open (or 0.95mm port size diameter). Also, the wellhead pressure reaches to the minimum value of 0.9 psi in which high-pressure drop between the reservoir pressure and the top surface will occur. Throughout this investigation, water was used as a working fluid since the column of corresponding water in petroleum production tubing has the highest hydrostatic pressure of 2.8 psig compared with crude oil. Hence, during the gas lift process crude oil will be less cumbersome to produce than water. The results present the maximum production rate of 18.3 lit/min (with 83% improvement on production) could be achieved. The results obtained experimentally were also used in constructing an economic analysis from the use of smart gas lift valve for different scenarios namely: (i) in gas lift natural flow and (ii) the gas lift wells. It was demonstrated that the flow rate can be enhanced from 91bbl/day to 166.5 bbl/day for the gas lift natural flow, and from ‘Zero’ (or non-production) to165.6 bbl/day for the gas lift well. Based on these results, the NPV of the gas lift natural flow will be approximately $2793 on $37 per barrel and for the gas lift well will be about $6127.2.

In the last decade, shale reservoirs emerged as one of the fast growing hydrocarbon resources in the world unlocking vast reserves and reshaping the landscape of the oil and gas global market. Gas-condensate reservoirs represent an important part of these resources. The key feature of these reservoirs is the condensate banking which reduces significantly the well deliverability when the condensate forms in the reservoir below the dew point pressure. Although the condensate banking is a well-known problem in conventional reservoirs, the very low permeability of shale matrix and unavailability of proven pressure maintenance techniques make it more challenging in shale reservoirs. The nanoscale range of the pore size in the shale matrix affects the gas flow which deviates from laminar Darcy flow to Knudsen flow resulting in enhanced gas permeability. Furthermore, the phase behaviour of gas-condensate fluids is affected by the high capillary pressure in the matrix causing higher condensate saturation than in bulk conditions. A good understanding and an accurate evaluation of how the condensate builds up in the reservoir and how it affects the gas flow is very important to manage successfully the development of these high-cost hydrocarbon resources. This work investigates the gas Knudsen flow under condensate saturation effect and phase behaviour deviation under capillary pressure of gas-condensate fluids in shale matrix with pore size distribution; and evaluates their effect on well productivity. Supplementary MATLAB codes are provided elsewhere on OpenAIR: http://hdl.handle.net/10059/2145.

The research on Determination of Residual Gas Saturation and Gas-Water Relative Permeability in Water-Driven Gas Reservoirs is divided into four stages: literature research, core-flooding experiments, development and application of a new technique for reservoir simulation. Overall, all stages have been completed successfully with several breakthroughs in the areas of Special Core Analysis (SCAL), reservoir engineering and reservoir simulation technology.Initially, a literature research was conducted to survey all available core analysis techniques and their individual characteristics. The survey revealed that there are several core analysis techniques for measuring residual gas saturation (Sgr) and hence, the lack of a commonly agreed method for measuring Sgr. The often-used core analysis techniques are steady-state displacement, co-current imbibition, centrifuge and counter-current imbibition. In this research, all centrifuge tests were performed with a decane-brine system to investigate the possibility of replacing gas with a 'model fluid' to minimise errors due to gas compressibility. Furthermore, Sgr is a function of testing temperature and pressure, types of fluid, wettability, viscosity, flow rate and overburden pressure. Consequently, large uncertainties are associated with measured Sgr and the recoverable gas reserves for water-driven gas reservoirs.Due to the lack of a common method for measuring Sgr, the first important step is to clarify which is the most representative core analysis technique for measuring Sgr. In Stage 2 of the research, core analysis experiments were performed with uniform fluids and ambient temperature. In the core flooding experiments, four different sets of core plugs from various gas reservoirs were selected to cover a wide range of permeability and porosity. Finally, all measured Sgr from the various common core analysis techniques were compared.The evidence suggested that steady-state displacement and co-current imbibition tests are the most representative techniques for reservoir application. Steady-state displacement also yields the complete relative permeability (RP) data but it requires long stabilisation times and is costly.In the third stage, a new technique was successfully developed for determining both Sgr and gas-water RP data. The new method consists of an initial co-current imbibition experiment followed by the newly developed correlation (Mulyadi, Amin and Kennaird correlation). Co-current imbibition is used to measure the end-point data, for example, initial water saturation (Swi) and Sgr. The MAK correlation was developed to extend the co-current imbibition test by generating gas-water relative permeability data. Unlike previous correlations, MAK correlation is unique because it incorporates and exhibits the formation properties, reservoir conditions and fluid properties (for example, permeability, porosity, interfacial tension and gas density) to generate the RP curves. The accuracy and applicability of MAK correlations were investigated with several sets of gas-water RP data measured by steady-state displacement tests for various gas reservoirs in Australia, New Zealand, South-East Asia and U.S.A. The MAK correlation proved superior to previously developed correlations to demonstrate its robustness.The purpose of the final stage was to aggressively pursue the possibility of advancing the application of the new technique beyond special core analysis (SCAL). As MAK correlation is successful in describing gas water RP in a core plug scale, it is possible to extend its application to describe the overall reservoir flow behaviour. This investigation was achieved by implementing MAK correlation into a 3-D reservoir simulator (MoReS) and performing simulations on a producing field.The simulation studies were divided into two categories: pre and post upscaled application.The case studies were performed on two X gas-condensate fields: X1 (post upscaled) and X2 (pre upscaled) fields. Since MAK correlation was developed for gas-water systems, several modifications were required to account for the effect of the additional phase (oil) on gas and water RP in gas-condensate systems. In this case, oil RP data was generated by Corey's equations. Five different case studies were performed to investigate the individual and combination effect of implementing MAK correlation, alternative Swi and Sgr correlations and refining porosity and permeability clustering. Moreover, MAK correlation has proven to be effective as an approximation technique for cell by cell simulation to advance reservoir simulation technology.

The research on Determination of Residual Gas Saturation and Gas-Water Relative Permeability in Water-Driven Gas Reservoirs is divided into four stages: literature research, core-flooding experiments, development and application of a new technique for reservoir simulation. Overall, all stages have been completed successfully with several breakthroughs in the areas of Special Core Analysis (SCAL), reservoir engineering and reservoir simulation technology.Initially, a literature research was conducted to survey all available core analysis techniques and their individual characteristics. The survey revealed that there are several core analysis techniques for measuring residual gas saturation (Sgr) and hence, the lack of a commonly agreed method for measuring Sgr. The often-used core analysis techniques are steady-state displacement, co-current imbibition, centrifuge and counter-current imbibition. In this research, all centrifuge tests were performed with a decane-brine system to investigate the possibility of replacing gas with a 'model fluid' to minimise errors due to gas compressibility. Furthermore, Sgr is a function of testing temperature and pressure, types of fluid, wettability, viscosity, flow rate and overburden pressure. Consequently, large uncertainties are associated with measured Sgr and the recoverable gas reserves for water-driven gas reservoirs.Due to the lack of a common method for measuring Sgr, the first important step is to clarify which is the most representative core analysis technique for measuring Sgr. In Stage 2 of the research, core analysis experiments were performed with uniform fluids and ambient temperature. In the core flooding experiments, four different sets of core plugs from various gas reservoirs were selected to cover a wide range of permeability and porosity. Finally, all measured Sgr from the various common core analysis techniques ++
were compared.The evidence suggested that steady-state displacement and co-current imbibition tests are the most representative techniques for reservoir application. Steady-state displacement also yields the complete relative permeability (RP) data but it requires long stabilisation times and is costly.In the third stage, a new technique was successfully developed for determining both Sgr and gas-water RP data. The new method consists of an initial co-current imbibition experiment followed by the newly developed correlation (Mulyadi, Amin and Kennaird correlation). Co-current imbibition is used to measure the end-point data, for example, initial water saturation (Swi) and Sgr. The MAK correlation was developed to extend the co-current imbibition test by generating gas-water relative permeability data. Unlike previous correlations, MAK correlation is unique because it incorporates and exhibits the formation properties, reservoir conditions and fluid properties (for example, permeability, porosity, interfacial tension and gas density) to generate the RP curves. The accuracy and applicability of MAK correlations were investigated with several sets of gas-water RP data measured by steady-state displacement tests for various gas reservoirs in Australia, New Zealand, South-East Asia and U.S.A. The MAK correlation proved superior to previously developed correlations to demonstrate its robustness.The purpose of the final stage was to aggressively pursue the possibility of advancing the application of the new technique beyond special core analysis (SCAL). As MAK correlation is successful in describing gas water RP in a core plug scale, it is possible to extend its application to describe the overall reservoir flow behaviour. This investigation was achieved by implementing MAK correlation into a 3-D reservoir simulator (MoReS) and performing simulations on a producing ++
field.The simulation studies were divided into two categories: pre and post upscaled application.The case studies were performed on two X gas-condensate fields: X1 (post upscaled) and X2 (pre upscaled) fields. Since MAK correlation was developed for gas-water systems, several modifications were required to account for the effect of the additional phase (oil) on gas and water RP in gas-condensate systems. In this case, oil RP data was generated by Corey's equations. Five different case studies were performed to investigate the individual and combination effect of implementing MAK correlation, alternative Swi and Sgr correlations and refining porosity and permeability clustering. Moreover, MAK correlation has proven to be effective as an approximation technique for cell by cell simulation to advance reservoir simulation technology.

For a natural gas importing country, &ldquo
take or pay&rdquo
approach creates problems since the demand for natural gas varies during the year and the excess amount of natural gas should be stored. In this study, an underground gas storage project is evaluated in a depleted gas Field M. After gathering all necessary reservoir, fluid, production and pressure data, the data were adapted to computer language, which was used in a commercial simulator software (IMEX) that is the CMG&rsquo
s (Computer Modelling Group) new generation adoptive simulator, to reach the history matching. The history matching which consists of the 4 year of production of the gas reservoir is the first step of this study. The simulation program was able to accomplish a good history match with the given parameters of the reservoir. Using the history match as a base, five different scenarios were created and forecast the injection and withdrawal performance of the reservoir. These scenarios includes 5 newly drilled horizontal wells which were used in combinations with the existing wells. With a predetermined injection rate of 13 MMcf/D was set for all the wells and among the 5 scenarios, 5 horizontal &ndash
6 vertical injectors &
5 horizontal - 6 vertical producers is the most successful in handling the gas inventory and the time it takes for a gas injection and production period. After the determination of the well configuration, the optimum injection rate for the entire field was obtained and found to be 130 MMcf/D by running different injection rates for all wells and then for only horizontal wells different injection rates were applied with a constant injection rate of 130 MMcf/d for vertical wells. Then it has been found that it is better to apply the 5th scenario which includes 5 horizontal &ndash
6 vertical injectors &
5 horizontal - 6 vertical producers having an injection rate of 130 MMcf/d for horizontal and vertical wells. Since within the 5th scenario, changing the injection rate to 1.3 Bcf/d and 13 Bcf/d, did not effect and change the average reservoir pressure significantly, it is best to carry out the project with the optimum injection rate which is 130 MMcf/d. The total gas produced untill 2012 is 394 BCF and the gas injected is 340 BCF where the maximum average reservoir pressure was recovered and set into a new value of 1881 psi by injection and cushion gas pressure as 1371 psi by withdrawal. If 5th scenario is compared with the others, there is an increase in injection and production performance about 90%.

The reliabilities of the gas-path components (compressor, burners and turbines) of a gas turbine (GT) are usually high when compared with those of other GT systems such as fuel supply and control. However, in the event of forced outage, downtimes are normally high, giving a relatively low availability. The purpose of condition monitoring and fault diagnostics is to detect, isolate and assess (i.e. estimate quantitatively the magnitude of) the faults within a system, which in this case is the gas turbine. An effective technique would provide a significant improvement in economic performance, reduce operational and maintenance costs, increase availability and improve the level of safety achieved. However, conventional analytical techniques such as gas-path analysis and its variants are limited in their applications to engine diagnostics due to several reasons that include their inability to:- operate effectively in the presence of noisy measurements; distinguish effectively sensor bias from component faults; preserve the nonlinearity in the gas-turbine parameter relationships; and the requirement for more sensors for achieving accurate diagnostics. The novelty of this research stems from its objective of overcoming most of these limitations and much more. In this thesis, we present the approach adopted in developing a diagnostic framework for the detection of faults in the gas-path of a gas turbine. The framework involves a large-scale integration of artificial neural networks (ANNs) designed and trained to detect, isolate and assess the faults in the gas-path components of the engine. Input to the diagnostic framework are engine measurements such as spool speeds, pressures, temperatures and fuel flow while outputs are either levels of changes in sensor(s) for the case of sensor fault(s) or the level of changes in efficiencies and flow capacities for the case of faulty components. The diagnostic framework has the capacity to assess both multiple component and multiple sensor faults over a range of operating points. In the case of component faults, the diagnostic system provides changes in efficiencies and flow capacities from which interpretations can be sought for the nature of the physical problem. The implication of this is that the diagnostic system covers a wide range of problems - both likely and unlikely-. The technique has been applied to several developed test cases, which are not only thermodynamically similar to operational engines, but also covers a range of engine configurations and operating conditions. The results obtained from the developed approach has been compared against those obtained from linear and nonlinear (recursive linear) gas-path analysis, as well as from the use of fuzzy logic. Analysis of the results demonstrates the promise of ANN applied to engine gas-path fault diagnostic activities. Finally, the limitations of this research and direction for future work are presented.

A study into potential gas shales is conducted to define the controlling factors of gas adsorption and evaluate gas adsorption capacity in shale gas reservoirs. The results from high-pressure adsorption experiment show that temperature, moisture and composition affect the gas adsorption in shale. In this study, a tool is introduced to predict gas adsorption capacity. This study helps to understand the mechanism of gas adsorption and evaluate gas storage in shale gas reservoirs.

The reaction of Water Gas Shift (WGS) plays a key role in the production of H2 or syngas, widely employed in the chemical industry. More than 90% of the H2 is currently produced by Steam Reforming (SR) of the natural gas or low molecular weight hydrocarbons, with an increasing role of its production from alternative sources such as the clean biogas (CBG), mixture of CH4 and CO2 obtained by elimination of S- and N-containing compounds from the gas mixture obtained by anaerobic fermentation of biomass. Compared to the mixture obtained in the SR of the natural gas, that obtained from CBG shows more hard conditions related to a higher CO concentration and a lower Steam/Dry Gas (S/DG) ratio. By hypothesizing a 2 steps process, the tests at high temperature (HTS, 350-450 °C) performed feeding the mixture obtained from CBG showed that Cu/Zn/Al catalysts (Cu 4 wt%) doped with small amount of Ga (Al/Ga = 50) can be usefully employed considering the higher activity and stability in comparison to a reference un-doped catalyst. The H2/CO ratio depended on the amount of the CO in the feed mixture and amount of steam fed. The best performances of the catalyst doped by Ga can be attributed to a higher dispersion and stability of the active phase, such as evidenced by a study of model catalysts and by the DRIFTS analysis in the adsorption/desorption of CO. An alternative to the two steps process is a single step process operating at medium temperature (MTS, 250-350 °C) using only one reactor. On the basis of previous studies, Cu/Zn/Al catalysts (Cu 20 wt%) have been investigated doped with small amounts of promoters (Al/Ce or Al/Zr 50), using a S/DG = 0,55 ratio. At 350°C Ce and Zr improve the catalityc activity, with a deactivation in presence of Zr only of 4%. On the contrary the catalyst containing Ce was stable at increasing reaction temperature.

Natural gas hydrates are solid crystalline substances found in the subsurface. Since gas hydrates are stable at low temperatures and moderate pressures, gas hydrates are found either near the surface in arctic regions or in deep water marine environments where the ambient seafloor temperature is less than 10°C. This work addresses the important issue of geomechanical stability in hydrate bearing sediments during different perturbations. I analyzed extensive data collected from the literature on the types of sediments where hydrates have been found during various offshore expeditions. To better understand the hydrate bearing sediments in offshore environments, I divided these data into different sections. The data included water depths, pore water salinity, gas compositions, geothermal gradients, and sedimentary properties such as sediment type, sediment mineralogy, and sediment physical properties. I used the database to determine the types of sediments that should be evaluated in laboratory tests at the Lawrence Berkeley National Laboratory. The TOUGH+Hydrate reservoir simulator was used to simulate the gas production behavior from hydrate bearing sediments. To address some important gas production issues from gas hydrates, I first simulated the production performance from the Messsoyakha Gas Field in Siberia. The field has been described as a free gas reservoir overlain by a gas hydrate layer and underlain by an aquifer of unknown strength. From a parametric study conducted to delineate important parameters that affect gas production at the Messoyakha, I found effective gas permeability in the hydrate layer, the location of perforations and the gas hydrate saturation to be important parameters for gas production at the Messoyakha. Second, I simulated the gas production using a hydraulic fracture in hydrate bearing sediments. The simulation results showed that the hydraulic fracture gets plugged by the formation of secondary hydrates during gas production. I used the coupled fluid flow and geomechanical model "TOUGH+Hydrate- FLAC3D" to model geomechanical performance during gas production from hydrates in an offshore hydrate deposit. I modeled geomechanical failures associated with gas production using a horizontal well and a vertical well for two different types of sediments, sand and clay. The simulation results showed that the sediment and failures can be a serious issue during the gas production from weaker sediments such as clays.

Gas sensitive semiconductors have been known for many years and applied in static gas alarm systems for the monitoring of hazardous gases, however, their application has been limited by a lack of selectivity. In this work a semiconducting gas sensor has been configured for use as a gas chromatographic detector thus combining the sensitivity of semiconductor sensors with the selectivity of gas chromatography. The study has been confined to tin oxide devices, more specifically the Taguchi gas sensor (TGS) . The majority of this work has concentrated on the TGS 813 although the use of other TGS is described. The development of suitable instrumentation is described and rigorous optimisation of the operating parameters e.g. heater voltage and column temperature has been performed using the variable step size simplex technique. Attention was concentrated on the response of the TGS 813 to hydrogen which was used as a test gas. A novel figure of merit, response multiplied by retention time and divided by skew factor was designed so that optimum response was obtained whilst maintaining adequate chromatographic separation. Optimum conditions were verified by univariate searches and the response was observed to be most dependant upon heater voltage. A limit of detection of 20 ppb v/v of hydrogen in a 1 ml sample was obtained at optimal conditions. Illustrative analyses of hydrogen were performed in human breath and laboratory air with results found to be in close agreement with literature values. Calibration was found to be linear over at least three orders of magnitude. The response of the TGS 813 to low molecular weight alkanes has also been investigated. It was observed that different heater voltage optima existed for each of the C1-C5 alkanes and that the sensor was relatively more sensitive to the higher molecular weight compounds. As with hydrogen linear response was obtained over at least three orders of magnitude and an illustrative analysis of natural gas showed excellent agreement with known levels. A compromise optimum heater voltage was used to study the response of the TGS 813 to alcohols, aldehydes, ketones and some Cs hydrocarbons. Capillary columns were used in this investigation and it was noted that they had potentially wider application than packed columns due to the use of an inert carrier with an air make-up flow to the detector. This replaced the air carrier gas used previously which might degrade certain stationary phases. Three different types of TGS: the 813; 822 and 831 were used in a study of the response and skew factor for the detection of halogen-containing compounds. Very high skew factors were often observed, although, for some compounds it appeared that symmetrical peaks could be obtained within narrow heater voltage ranges. Skewed response was observed to be dependant upon sensor type, heater voltage and halogen proportion and type. Analysis of the three sensor types was performed and differences in potential surface area and tin oxide additives observed. The presence of additives was observed to adversely affect sensor recovery.

Thesis: S.M. in Technology and Policy, Massachusetts Institute of Technology, School of Engineering, Institute for Data, Systems, and Society, Technology and Policy Program, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 69-72).
Climate change is a major factor reforming the world's energy landscape today, and as electricity consumes 40% of total energy, huge efforts are being undertaken to reduce the carbon footprint within the electricity sector. The electric sector has been taking steps to reform the grid, retiring carbon-intensive coal plants, increasing renewable penetration, and introducing cyber elements end-to-end for monitoring, estimating, and controlling devices, systems, and markets. Due to retirements of coal plants, discovery of shale gas leading to low natural gas prices, and geopolitical motives to reduce dependence on foreign oil, natural gas is becoming a major fuel source for electricity around the United States. In addition, with increasingly intermittent renewable sources in the grid, there is a need for a readily available, clean, and flexible back-up fuel; natural gas is sought after in New England to serve this purpose as a reliable and guaranteed fuel in times when wind turbines and solar panels cannot produce. While research has been conducted advocating natural gas pipeline expansion projects to ensure this reliability, not enough attention has been paid to the overall market structure in the natural gas and electricity infrastructures which can also impact reliable delivery of gas and therefore efficient interdependency between the two infrastructures. This thesis explores the market structures in natural gas and electricity, the interdependence of natural gas and electricity prices with increasing reliance on natural gas as the penetration of renewable energy resources (RER) increases in order to complement their intermittencies, possible volatilities in these prices with varying penetration rates in RER, and alternatives to existing market structures that improve reliability and reduce volatility in electricity and gas prices. In particular, the thesis will attempt to answer the following two questions: What will the generation mix look like in 2030 and how will this impact gas and electricity prices? How do Gas-Fired Generator (GFG) bids for gas change between 2015 and 2030? In order to answer these questions, a computational model is determined using regression analysis tools and an auction model. Data from the New England region in terms of prices, generation, and demand is used to determine these models.
by Neha Nandakumar.
S.M. in Technology and Policy

An inter-laboratory study of high-pressure gas sorption measurements on two carbonaceous shales has been conducted to assess the reproducibility of sorption isotherms on shale and identify possible sources of error. The measurements were carried out by 7 different international research laboratories on either in-house or commercial sorption equipment using manometric as well as gravimetric methods. Excess sorption isotherms for methane, carbon dioxide and ethane were measured at 65°C and at pressures up to 25 MPa on two organic-rich shales at dry conditions. The inter-laboratory reproducibility of the methane excess sorption isotherms was better for the high-maturity shale (within 0.02 – 0.03 mmol g-1) than for the low-maturity sample (up to 0.1 mmol g-1), which is in agreement with results of earlier studies on coals. The procedures for sample conditioning prior to the measurement, the measurement procedures and the data reduction approach must be optimized to achieve higher accuracy. Unknown systematic errors in the measured quantities must be minimized first by applying standard calibration methods. Furthermore, the adsorption of methane on a dry, organic-rich, high-maturity Alum shale sample was studied at a wide temperature range (300 – 473 K) and pressures up to 14 MPa. These conditions are relevant to gas storage under geological conditions. Maximum methane excess uptake is 0.176 – 0.042 mmol g-1 (125 - 30 scf t-1) at 300 - 473 K. Supercritical adsorption was parameterized using the modified Dubinin-Radushkevich and the Langmuir equations. Gas in shales is stored in three different states: adsorbed, compressed (free) and dissolved; quantifying each underpins calculations of gas storage capacity and also the mechanisms by which gas must be transported from pore (surfaces), to fracture, to the well. While compressed gas dominates in meso- and macropores, it is often assumed that (a) sorbed gas occurs mainly in micropores (< 2nm) and (b) micropores are mainly associated with organic matter. In the third part of this thesis, those ideas are tested by characterising the porous structure of six shales and isolated kerogens from the Posidonia Formation in combination with high pressure methane sorption isotherms at 45, 65 and 85°C. Together, these data help us to understand the extent to which (a) small pores control CH4 sorption and (b) whether “sorption” pores are associated with the organic and inorganic phases within shales. Samples were selected with vitrinite reflectance of 0.6, 0.9 and 1.45%. Pore volumes – named sorption pore volumes here - were determined on dry shales and isolated kerogens by CO2 isotherms measured at -78°C and up to 0.1 MPa. These volumes include micropores (pore II width < 2nm) and narrow mesopores; according to the Gurvitch Rule this is the volume available for sorption of most gases. Sorption pore volumes of Posidoniashales range from 0.008 to 0.016 cm3 g-1, accounting for 21 - 66% of total porosity. Whilst sorption pore volumes of isolated kerogen are much higher, between 0.095 – 0.147 cm3 g-1, normalization by TOC shows that only half the sorption pore volume of the shales is located within the kerogen. Excess uptakes on dry Posidonia shales at 65°C and 11.5MPa range from 0.056−0.110 mmol g-1 (40−78 scf t-1) on dry shale, and from 0.36−0.70 mmol g-1 (253−499 scf t-1) on dry kerogen. Enthalpies of adsorption show no variation with TOC and maturity, respectively. The correlation between maximum CH4 sorption and CO2 sorption pore volume at 195 K is very strong and goes through the origin, suggesting that the vast majority of sorbed CH4 occurs in pores smaller than 6 nm. Approximately half the sorption pore volume and thus CH4 sorption potential of these dry shales is in organic matter, with the rest likely to be associated with clay minerals. Sorption mass balances using isotherms for kerogen and clay minerals do not always account for the total measured sorbed CH4 on dry shales, suggesting that some sorption may occur at interfaces between minerals and organic matter.

Elevated concentrations of ground-gases (CH4 and CO2) and VOCs in contaminated soil and water around the world pose significant risk both to human health and the environment. There is, therefore, a requirement to monitor them for effective risk assessment and remediation. Current ground-gas monitoring is often ineffective for determining their representative concentrations and fluxes – the two most important parameters necessary for ground-gas risk assessment. These failures of current monitoring may arise from its low temporal resolution. The recent ability to monitor at high temporal resolution – using Gasclam - makes it possible to determine whether this is the case and whether high resolution monitoring can be more effective. CH4 and CO2 were monitored at several sites using Gasclam. This showed that in many cases concentrations were sufficiently variable that current sampling practices would be ineffective at detecting worst case concentrations. Furthermore, the time-series data produced by Gasclam allowed the predictive power of the established relationships between atmospheric pressure and gas concentration to be improved. The failures in the relationship could also be understood as hysteresis which gave an index of ground permeability and/or gas generation. These improvements in understanding could be used to improve the conceptual site models on which risk assessments are based. Similarly, high temporal resolution VOC measurement demonstrated the need for such measurement. The factors controlling VOC concentration were shown to be same to those controlling ground-gases; again this understanding of process would also improve the conceptual site model. A monitoring method that incorporated parallel non-specific real time measurement with a time integrated VOC measurement that identified specific VOC’s was tested. The method was an improvement on the separate methods as it could be used to reasonably infer the concentrations of specific VOC’s at high temporal resolution. The ability to monitor gas concentrations at high temporal resolution gave the potential for the rate of gas concentration recovery subsequent to purging of the borehole to be used as an index of gas flux. These tests proved to be practical, generally taking less than the time of a site visit, and reproducible. Variability in these recovery profiles was assessed at different sites, times and for different gases.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 24, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Jerry L. Atwood. Vita. Includes bibliographical references.

In this study, gas sensing systems that are based on piezoelectric smart material and structures are proposed, designed, developed, and tested, which are mainly aimed to address the temperature dependent CO2 gas sensing in a real environment. The state-of-the-art of gas sensing technologies are firstly reviewed and discussed for their pros and cons. The adsorption mechanisms including physisorption and chemisorption are subsequently investigated to characterize and provide solutions to various gas sensors. Particularly, a QCM based gas sensor and a C-axis inclined zigzag ZnO FBAR gas sensor are designed and analyzed for their performance on room temperature CO2 gas sensing, which fall into the scope of physisorption. In contrast, a Langasite (LGS) surface acoustic wave (SAW) based acetone vapor sensor is designed, developed, and tested, which is based on the chemisorption analysis of the LGS substrate. Moreover, solid state gas sensors are characterized and analyzed for chemisorption-based sensitive sensing thin film development, which can be further applied to piezoelectric-based gas sensors (i.e. Ca doped ZnO LGS SAW gas sensors) for performance enhanced CO2 gas sensing. Additionally, an innovative MEMS micro cantilever beam is proposed based on the LGS nanofabrication, which can be potentially applied for gas sensing, when combined with ZnO nanorods deposition. Principal component analysis (PCA) is employed for cross-sensitivity analysis, by which high temperature gas sensing in a real environment can be achieved. The proposed gas sensing systems are designated to work in a high temperature environment by taking advantage of the high temperature stability of the piezoelectric substrates.

Wet Gas Metering is becoming increasingly important to the Oil and Gas Industry. In this research a wet gas flow is defined as a liquid / gas two-phase flow that has a gas mass content greater then 50 %. The Venturi Meter is a favoured wet gas meter in the Oil and Gas Industry. However, industry's understanding of wet gas flow phenomena in such a meter is limited and is therefore forced to accept large metering errors when existing correlations are used to take account of the liquid presence. Furthermore, these correlations all require an input value for the liquid flowrate. This information is not readily available to natural gas production engineers. This research extensively discusses the current wet gas metering situation and then uses new independent data from the NEL Wet Gas Loop to compare the performance of existing correlations when used with a Venturi Meter. This new data is examined to determine parameters that effect the meter reading and then new correlations are presented. One new correlation offered uses the additional information from a downstream pressure tapping in conjunction with the traditional upstream pressure reading and the Venturi pressure differential to predict the gas flowrate without knowledge of the liquid flowrate.

Recent advances in using microscopes in ultracold atom experiment have allowed experimenters for the first time to directly observe and manipulate individual atoms in individual lattice sites. This technique enhances our capability to simulate strongly correlated systems such as Mott insulator and high temperature superconductivity. Currently, all ultracold atom experiments with high resolution imaging capability use bosonic atoms. In this thesis, I present our progress towards creating the fermionic version of the microscope experiment which is more suitable for simulating real condensed matter systems. Lithium is ideal due to the existence of both fermionic and bosonic isotopes, its light mass, which means faster experiment time scales that suppresses many sources of technical noise, and also due to the existence of a broad Feshbach resonance, which can be used to tune the inter-particle interaction strength over a wide range from attractive, non-interacting, and repulsive interactions. A high numerical aperture objective will be used to image and manipulate the atoms with single lattice site resolution. This setup should allow us to implement the Hubbard hamiltonian which could describe interesting quantum phases such as antiferromagnetism, d-wave superfluidity, and high temperature superconductivity. I will also discuss the feasibility of the Raman sideband cooling method for cooling the atoms during the imaging process. We have also developed a new electronic control system to control the sequence of the experiment. This electronic system is very scalable in order to keep up with the increasing complexity of atomic physics experiments. Furthermore, the system is also designed to be more precise in order to keep up with the faster time scale of lithium experiment.
Physics

Three heterocyclic systems were prepared along with derivatives. The thermal decompositions of these heterocycles was examined and their suitability as gas generators assessed, with respect to, melting point, decomposition temperature, volume and type of gases evolved, ease of hydrolysis, and ease of preparation. The preparation of 2-azido-5-phenyl-1,3,4-oxadiazole by a variety of routes is described. It was stable above its melting point and at higher temperatures decomposition was violent, evolving nitrogen, along with the formation of benzoyl cyanide. 1,2,4-Oxadiazolidine-3,5-dione melted at 103-105^oC and decomposed at ca 155^oC with gas evolution. 2,2'-Adipoyldi-1,2,4-oxadiazolidine-3,5-dione and the corresponding succinyl derivatives were prepared in good yield and decomposed on melting. The oxalyl and malonyl derivatives were more difficult to prepare due to their ease of hydrolysis. The oxalyl derivative decomposed ca 20^o above its melting point. Parabanic acid (2,4,5-triketoimidazolidine) was easily prepared in high yield and decomposed on melting. N,N'-Diacetyl- and N,N'-dibenzoyl-parabanic acids were prepared, via the disodium salt of parabanic acid, and decomposed on melting. Monoacetyl parabanic acid decomposed 20-30^o above its melting point. Hydrolysis of the acetyl derivatives was studied by ¹H nmr spectroscopy. In the presence of adventitious water in the solvent diacetylparabanic acid gives, initially, the monoacetyl derivative and acetic acid, followed by ring opening to N-acetyloxaluric acid. This ease of hydrolysis reduces its attractiveness as a potential gas generator. An X-ray crystallographic determination was carried out on diacetylparabanic acid and the significance of the bond lengths in the hydrolysis process is discussed. N,N'-Adipoyldi-parabanic acid was prepared in low yield and decomposed ca 20^o above its melting point.

Amperometric gas sensors are widely used for environmental and industrial monitoring. They are sensitive and cheap but suffer from some significant limitations. The aim of the work undertaken in this thesis is the development of ‘intelligent’ gas sensors to overcome some of these limitations. Overall the thesis shows the value of ionic liquids as potential solvents for gas sensors, overcoming issues of solvent volatility and providing a wide potential range for electrochemical measurements. Methods have been developed for sensitive amperometry, the tuning of potentials and especially proof-of-concept (patents Publication numbers: WO2013140140 A3 and WO2014020347 A1) in respect of the intelligent self-monitoring of temperature and humidity by RTIL based sensors. Designs for practical electrodes are also proposed. The specific content is as follows. Chapter 1 outlines the fundamental principles of electrochemistry which are of importance for the reading of this thesis. Chapter 2 reviews the history and modern amperometric gas sensors. Limitations of present electrochemical approaches are critically established. Micro-electrodes and Room Temperature Ionic Liquids (RTILs) are also introduced in this chapter. Chapter 4 is focused on the study of analysing chronoamperometry using the Shoup and Szabo equation to simultaneously determine the values of concentration and diffusion coefficient of dissolved analytes in both non-aqueous and RTIL media. A method to optimise the chronoamperometric conditions is demonstrated. This provides an essential experimental basis for IL based gas sensor. Chapter 5 demonstrates how the oxidation potential of ferrocene can be tuned by changing the anionic component of room temperature ionic liquids. This ability to tune redox potentials has genetic value in gas sensing. Chapters 6 and 7 describe two novel patented approaches to monitor the local environment for amperometric gas detection. In Chapter 6, an in-situ voltammetric ‘thermometer’ is incorporated into an amperometric oxygen sensing system. The local temperature is measured by the formal potential difference of two redox couples. A simultaneous temperature and humidity sensor is reported in Chapter 7. This sensor shows advantageous features where the temperature sensor is humidity independent and vice versa. The Shoup and Szabo analysis (Chapter 4) requires ‘simple’ electron transfer and as such the reduction of oxygen in wet RTILs can be complicated by dissolved water. Chapter 8 proposes a method to stop oxygen reduction at the one electron transfer stage under humid conditions by using phosphonium based RTILs to ‘trap’ the intermediate superoxide ions. Chapters 9 and 10 report the fabrication of low cost disposable electrodes of various geometries and of different materials. The suitability of these electrode for use as working electrodes for electrochemical experiments in aqueous, non-aqueous and RTIL media is demonstrated. Their capability to be used as working probes for amperometric gas sensing systems is discussed.

The alchemical term solve et coagula describes the two stages of the refinement process that materials go through to transform into another form. This work is a result of an idea of how dissolution and coagulation can occur in painting and how it manifests physically. Each physical object, break it apart to its core and elements, and you will find it in the land. As a thought, a dream, or a memory, it is part of the landscape of your mind. And like a word that exists in our social landscape.

This investigation generated new experimental data on premixed gas/air vented explosions. A small (0.01 m3) and medium scale (0.2 m3) cylindrical vessels were used with L/D of 2.8 and 2 respectively, with range of vent area coefficients Kv of 2.7-21.7. The initial set of experiments considered free venting, so that the flame propagation during the venting process was laminar and also the short distance of the vessels would reduce the effects of flame self-accelleration. Covered vents were later used with vent static burst pressure Pstat from 35 to 450mb in the 10L vessel. Different gas mixtures were used throughout this work including methane-air (10%), propane-air (4 and 4.5%), ethylene-air (6.5 and 7.5%), and hydrogen-air (30 and 40%) gas mixtures. The ignition position at the far end opposite the vent and central location mid-way the length of the vessels were compared. Current venting guidance is based on experimental vented explosions with central ignition, but this work shows that end ignition opposite the vent is the worst case. The current design procedures for the protection of explosions using venting is shown to be inadequate for hydrogen-air explosions. New data has been presented which indicates that for hydrogen explosions, the vent flow behaves differently as compared to other gas mixtures investigated. Hence, the need for more research in hydrogen-air mixtures in order to have better understanding of hydrogen venting process. Experimental data from the current work also shows that multiple vents and vent shapes have significant effects on explosion overpressure and flame speeds. This is contrary to the assumption of the current venting standards. The effect of static burst pressure on explosion venting was shown to be quite different to that in the design standards, which is supported by other work in larger vessels. Other aspects of vent design that the standards say are not important were shown to be significant: the number of vents, the position of the vent, the shape of the vent, the ignition position. Laminar flame venting theory was shown to be a good predictor of the results and those from the literature where larger vessels were used.

Explosion venting technology is widely accepted as the effective constructional protection measures against gas and dust explosions.The key problem in venting is the appropriate design of the vent area necessary for an effective release of the material i.e. the pressure developed during explosion did not cause any damage to the plant protected.Current gas explosion vent design standards in the USA (NFPA68, 2002) and European (2007) rely on the vent correlation first published by Bartknecht in 1993 (Siwek, 1996).N FPA 68 also recommends the correlation of Swift (Swift,1983)at low overpressures. For a vent to give no increase in overpressure other than that due to the pressure difference created by the mass flow of unburnt gases through the vent, the vent mass flow rate is assumed to be equal to the maximum mass burning rate of the flame and this consideration should be used as the design mass flow through the vent. Two different methods ( Method I and Method 2) have been proposed based on the Sμ and Sμ (E-1) to describe the maximum mass burning rate given as, mb = ASμpμ=CdeA(2pPμred)o.5 mb =ASgPm =AgSμ(E-I)P μ=Cde4,(2pu Pred)0,5 (2) The equation given in (2) is slightly different from (1) as is about 6.5 times the mass flow of the first method as it takes the effect of (E-1) where E is the expansion ratio. A critical review were carried out for the applicability, validity and limitation on the venting correlations adopted in NFPA 68 and European Standard with 470 literature experimental data, covering a wide range of values for vessel volume and geometries, bursting vent pressure, Pv L/D ratio, maximum reduced pressure, Pred and ignition location. The fuels involved are methane, propane, hydrogen, town gas, ethylene, acetone/air mixtures with the most hazardous near-stoichiornetric fuel-air concentration. Besides, Molkov's equation (Molkov, 2001) which is regarded as alternative venting design offered in NFPA 68 and Bradley and Mitcheson's equation for safe venting design were also analysed on the experimental data for their validity and limitation as well as the proposed methods. From the results, it is clear that Bartknecht's equation gave a satisfactory result with experimental data for K <-5 and Swift's equation (Swift, 1983) can be extended to wider range for Pred> 200 mbar, providing the parameter PV is added into the equation. Method 2 gave a good agreement to most of the experimental data as it followed assumptions applied for correlations given by Bradley and Mitcheson for safe venting design (Bradley and Mitcheson, 1978a,B radley and Mitcheson, 1978b). It is also proven that the vent coefficient, K is confident to be used in quantifying the vessel's geometry for cubic vessel and the use of As/Av term is more favourable for non-cubic vessels. To justify the validity and applicability of the proposed methods, series of simply vented experiments were carried out, involving two different cylindrical volumes i.e. 0.2 and 0.0065 M3. It is found that self acceleration plays important role in bigger vessel in determining the final Pmax inside the vessel. Method 2 gave closer prediction on Pmax in respect with other studied correlations. The investigation of vented gas explosion is explored further with the relief pipe been connected to the vessel at different fuel/air equivalence ratios, ignition position and Pv. The results demonstrate that the magnitude of Pmax was increased corresponding to the increase of Pv- From the experiments,it is found that peak pressure with strong acoustic behaviour is observed related to increase in Pv and in some cases,significant detonation spike was also observed particularly in high burning velocity mixtures. It is found that substantial amount of unburnt gases left inside the vessel after the vent burst is the leading factor in increase of Pmax for high burning velocity mixtures at centrally ignited. The associate gas velocities ahead of the flame create high unburnt gas flows conditions at entry to the vent and this give rise to high back pressures which lead to the severity in final Pmax inside the vessel. It was observed that end ignition leads to a higher explosion severity than central ignition in most cases, implying that central ignition is not a worst-case scenario in gas vented explosions as reported previously.

Master Thesis Economic Analysis
This paper examines the effect of natural gas storage on natural gas prices. Using a comprehensive dataset containing daily data for the period 2010-2014 we estimate two specifications for the Dutch, German and British natural gas markets. We do not find evidence of a stabilising effect of natural gas storage on daily price changes. However we do find strong evidence of a positive effect of inventory levels of natural gas storage facilities on intertemporal price spreads

The formation of Saccharomyces cerevisiae cell wall requires the coordinated activity of enzymes involved in the biosynthesis and modification of its components, such as glucans. The β-(1,3)-glucan synthase complexes, that have Fks proteins as putative catalytic subunits, use UDP-glucose as a substrate and catalyse the synthesis and vectorial extrusion of glucan chains into the outer space. Then, β-(1,3)-glucan chains are branched, elongated and remodelled in order to create a robust texture capable of counteracting the high internal pressure and determining cell morphology. β-(1,3)-glucan is the main component of the vegetative cell wall and one of the most abundant polymers of the spore wall. Several enzymes belonging to the family GH72 of glycosyl hydrolases have been identified in fungi. These enzymes are responsible of the lateral elongation of β-(1,3)-glucan, thus contributing to the assembly and organization of the glucan layer. The multigene GAS family of S. cerevisiae is composed of five members, GAS1-5, involved in cell wall maintenance. They share significant similarity with Aspergillus fumigatus GEL1 and GEL2, and with Candida albicans PHR1 and PHR2. Similar to the most extensively characterized member, Gas1p, the remaining Gas proteins are β-(1,3)-glucanosyltransferases involved in cell wall assembly and maintenance. Based on their expression patterns, they appear to play partially overlapping roles throughout the yeast life cycle: GAS1 and GAS5 are expressed during vegetative growth, whereas GAS2 and GAS4 are expressed exclusively during sporulation and required for normal spore wall formation, finally GAS3 is a weakly expressed gene. Thus these enzymes could satisfy the cellular needs to remodel β-(1,3)-glucan in different physiological conditions and in different conformations along the yeast life cell cycle. Moreover, considering its role in yeast cell biology, the GAS enzyme family represents a very promising molecular target for new antifungal drugs. During my PhD thesis I focused my interest on the functional characterization of GAS1, 2, 3 and 4 in various stages of the yeast life cycle: vegetative growth, meiosis, sporulation and spore germination. This study is aimed to understand the biological significance of the developmentally regulated requirement of the specific members of the GAS redundant family in the morphological stages of yeast life cycle. GAS2 and GAS4 genes are specifically induced during sporulation and encode for glycoproteins. The effects of the loss of Gas2 and Gas4 proteins on spore wall morphogenesis are dramatic. Synthesis of all the layers of the spore cell wall occurs, but the accumulation and organization of wall material is abnormal. The lack of the elongase activity of Gas2 and Gas4 proteins in the double mutant might cause the formation of shorter or less branched β(1,3)-glucan chains in the inner layer of the spore wall. Thus, the connection of the outermost layers to a less compact glucan network could make the spore wall more fragile and easily stripped under harsh conditions. These defects cause an increase in spore permeability to exogenous substances, a decrease in refractivity, and a marked decrease in spore viability. The possible execution point for GAS2 and GAS4 could be between the synthesis and organization of β(1,3)-glucan and, more specifically, in the elongation of the β(1,3)-glucan chains. Consistently with their role, during sporulation Gas2 and Gas4 proteins localize at the newly assembling prospore membrane during the meiotic divisions and in mature ascospore the proteins decorate the spore periphery. A slight difference in the protein patterns of fluorescence on the spore suggests that Gas2p and Gas4p final localization could be respectively the spore wall and the prospore membrane. In this work, an extensive study of the localization of the Gas1 protein during the yeast life cycle was performed, taking advantage of a GFP-tagged version of the protein. During vegetative growth Gas1p has a dual localization: in the plasma membrane and at the site of bud emergence, particularly in the neck, in the chitin ring that surrounds the neck region and in the bud scars where Gas1p remains after cytokinesis. At the neck region Gas1p appears to absolve important functions in yeast as a part of the mechanisms that ensure the resistance of the neck region and the morphogenesis of the septum. The size and morphology of the neck region is severely affected both in the gas1Δ and gas1Δ chs3Δ mutant, suggesting an involvement of the protein in the maintenance of the integrity of the mother-bud neck region. The presence of Gas1p in the chitin ring could be part of the mechanism necessary to prevent new incorporation of glucan chains into the neck region or alternatively the protein could be required for a particular type of remodelling necessary for the septum region in preparation to cell division. Additionally, Gas1p could act as landmark protein for the choice of the site of bud emergencee. As to Gas1p localization at the plasma membrane, our study supports the validity of Gas1p-GFP as a marker to follow the dynamics of lipid raft. At the induction of sporulation, GAS1 mRNA levels steadily decrease and by 10h it is completely declined. Surprisingly, Gas1p levels are roughly constant during the entire sporulation processs and the protein is very stable, being detectable also at 43h after the induction of sporulation. During spore development, a translocation event occurs through which at the completion of meiosis II, Gas1p, synthesized during vegetative growth, is removed from the plasma membrane and internalized. Later, Gas1p is detected associated to the nascent prospore membrane surrounding the nuclear lobes and finally in mature spores it localizes at the spore periphery. This translocation event suggests that Gas1p delivery to the spore surface is not part of the developmentally reprogramming of the secretory pathway from the trans Golgi to the prospore membrane, whereas it involves at least in part the endocytic pathway. We demonstrated that END3-mediated endocytosis is one of the mechanisms required for the removal of the Gas1p from the plasma membrane and its efficient re-localization at the prospore membrane. Moreover in a sps1Δ mutant, Gas1p remains localized at the plasma membrane and fails to reach the spore surface. Sps1p is a member of the Ste20 protein kinase family and regulates the trafficking to the prospore membrane of enzymes involved in spore wall synthesis, such as the glucan synthase Fks2p and chitin synthase Chs3p. Thus Sps1p could regulate the traffic of Gas1p most likely in an indirect way by interacting and modifying the components of the intracellular trafficking machinery. Gas1p translocation during sporulation To test a possible involvement of Gas1p in spore wall formation, in this study we tried to characterize the sporulation phenotype of a gas1Δ mutant. Unfortunately our analysis was complicated by the mutant reduced cell viability when grown in presence of a poor carbon source such as acetate. gas1Δ sporulation defect could rely in a unsatisfied energetic request as the cell wall perturbations, typical of a gas1Δ mutant, enhance carbon and energy mobilization to efficiently combat cell wall weakening and the metabolism of acetate as the sole carbon source could be not sufficient to satisfy this energetic request. Moreover the addition of sorbitol to the sporulation medium only partially rescues gas1Δ defective phenotype during spore development. Even though sorbitol can mitigate the gas1Δ cell wall damages, it has no buffering effect on the gas1Δ energetic request, thus the mutant cells remained substantially unable to sporulate. Consequently, gas1Δ sporulation defective phenotype appears to be reminiscent of the mutant defects during vegetative growth, even worsened in a poor carbon source. Even though we cannot exclude a role for Gas1p during spore morphogenesis, it is our consumption that the protein translocation to the spore represents a “storage”mechanisms to ensure the presence of the Gas1p during spore germination. At 3h after the shift to a rich medium, Gas1p exhibits a highly polarized distribution, decorating exclusively half of the germinating spore in its growing pole. The protein localization is consistent with its role in glucan layer remodelling of the cell wall at the growing portion of the germinating cell. Besides gas1Δ germinating spore inability to support the elongation during the polarized growth of the cell suggests that Gas1p is required for a very early step in germination. Besides the protein is involved in a post-germination stage to support the polarized growth of the newly emerging bud. Finally, in this study we reported the preliminary results about the functional characterization of GAS3. The gene is expressed at a very low level during the vegetative growth in glucose and acetate. Consistently with the GAS3 expression pattern, Gas3p appears as a highly polydispersed glycoprotein of high molecular weight that is present in vegetative growing cells and along the sporulation process. EndoH treatment reduces the size and the aspect of the protein to a sharp band, suggesting that Gas3p is a heavily N-glycosylated protein. The experiments indicated that neither the overexpression nor the deletion of the GAS3 gene, alone or in combination with GAS2 and GAS4, lead to relevant differences in sporulation with respect toh the wild type or with the defective phenotype of the gas2 gas4 null mutant strain . The construction of a tagged version of the Gas3 protein to determine its localization will be a useful tool to understand the function ofl Gas3p during yeast life cycle.

Gas flaring is the burning of unwanted produced natural gas, which cannot be processed or sold during oil and gas production and processing operations. In past decades, gas flaring was believed to be environmentally tolerable. However, scientists have found that the flaring of gas is an impediment to the environment; this has led to attempting to tackle the problem of gas flaring to advance it to an acceptable level worldwide. In this study, two options were investigated for the utilisation of natural gas that was previously flared. The first option was a theoretical investigation of the use of ceramic perovskite membranes in a tubular reactor for the partial oxidation of methane (flare gas) to syngas. The H2/C product ratio of partial oxidation of methane is 2:1, which is suitable for Fischer-Tropch technology or methanol synthesis. It was found that this option is ideal for converting natural gas into synthesis gas (CO + H2), and it reduces capital and running costs, as these membranes are able to separate oxygen from the air stream with no need for an oxygen separation plant. The novelty of this approach is that the production of syngas using oxygen selective membranes can be achieved at the “Wellhead” with no requirement for the gas to be transported and a consequent reduction in transport costs. The second option was an experimental investigation in using spraying and atomisation techniques for the generation of carbon nanotubes, by spraying simulated catalyst solution droplets into a hydrocarbon gas stream (methane as a carbon source) using a novel “atomiser device” incorporating pressure swirl atomisers. The second part of the investigation was divided into two phases: Phase-I, which was implemented at the Spray Research Group laboratory at the University of Salford, involved a series of experiments which were undertaken to produce fine aerosol droplets that have a number mean diameter of less than or equal to 5 μm, which was successfully achieved. In this phase, water and air were used to simulate the metal catalyst and methane, respectively, which were used in Phase-II. Phase-II trials were implemented at the University of Oxford on a collaborative basis. A furnace was installed underneath of the Phase-I “atomiser device” and the stream of droplet particles fell down through the furnace (400 - 800o C). Reaction inside the furnace occurred to produce the Single Wall Carbon Nanotubes (SWCNT) material. The preliminary results of the experiments in this Phase showed that it is possible to produce SWCNT. This investigation also considered an economic analysis of reducing gas flaring. A Visual Basic (VB) programme was developed to make a cost comparison between the proposed options and current conventional plants. The consideration of the economic analysis demonstrated that the cost of natural gas flaring exceeds those for syngas and Single-Walled Carbon Nanotubes production.

Modelling gas-solid two-phase flows using a two-fluid approach has two main difficulties: formulating constitutive laws for the particulate stresses and modelling the gas turbulence modulation. Due to the complex nature of the gas-particle interactions, there is no universal model covering every flow regime. In this thesis, three flow regimes with distinctive characteristics are studied, i.e. the very dense regime where the solid volume fraction, v₂>5%, the dense flow regime where 5%≥1%, and the relatively dilute regime where 1%≥v₂>0.1%. In the very dense flow regime, where the interstitial gas is normally neglected, the gas flow is assumed laminar and causes a viscous energy dissipation in the particulate phase. Numerical results for granular materials flowing down an inclined chute show that the interstitial gas may have a considerable effect in these flows. In the dense regime, where the inter-particle collisions are very important, a fluctuational energy transfer rate between the two phases is postulated, similar to that in a dilute Stokes flow. Consequently, the numerical solutions relax the restriction of elastic inter-particle collisions and show good agreement with experimental measurements. In the above two regimes, the kinetic theory of dry granular flow is adopted for the particulate stresses because the inter-particle collisions dominate the flows. The interstitial gas influence on the constitutive flow behaviour of the particulate phase is considered in the relatively dilute flow regime also, and a k-equation with a prescribed turbulent length scale is first used to address the gas turbulence modulation. Numerical results show that the gas turbulence has a significant effect on the microscopic flow behaviour of the particulate phase. The k-equation of Crowe & Gillandt (1998) has the best performance in predicting the experimentally observed phenomena. Finally, the influence of the particles on the k-^Ε model coefficients are studied and the turbulent motion is considered to be restricted by the particles, thereby reducing the turbulent length scale directly. The simulation results indicate that these coefficients should be modified in order to incorporate the effect of particles.

The ability to distinguish effectively between a range of gases in a reliable, repeatable manner is of major interest with both scientific and commercial relevance. Semiconducting metal oxide gas sensors have a long life-span, are inexpensive and are highly sensitive; however, they are generally found to lack a desired level of selectivity. One highly viable approach for enhancing the selective power of such devices is the addition of a transformation layer. This will typically be a micro- or meso-porous, solid which will act to transform the analyte gas stream by some means. Here the use of zeolite compounds for this purpose is investigated. Different theoretical models are used to probe the dependency of the response of a porous metal oxide sensor on the transport properties of gas through the device, including through an additional zeolite layer. Through the use of a force-field based method, shape and size selective adsorption is predicted and used to justify experimental results of zeolite modified sensors, for example, the reduction of response to linear hydrocarbons as the chain-length is increased. However, the limit of such calculations is also realised such that this approach is unlikely to provide an adequate predictive tool for selecting a suitable zeolite for a particular gas sensing task. Following this, a model based on the method of diffusion eigenstates has been developed to calculate bulk effective diffusivities and rate constants for porous systems representing both the sensor and zeolite porous layers. The effective properties are found to depend strongly on the microstructure, the partitioning between phases and diffusion coefficients of the different phases. The effective parameters are then interpreted in terms of sensor response by solving the one-dimensional diffusionreaction equation for a simple two-layered macroscopic geometry. The method of finite differences is used to find the concentration profile which generates a response on interaction with an electric field established between two electrodes. The concentration profile and hence the response depends on the balance of diffusion and reaction of the analyte gas within both the sensor and zeolite layers. It is shown how the response can be explored to expose such differences by firstly looking at both the steady state response and response time and also by varying the positioning of the electrodes used to measure the response. Good correlation with experimental response data is demonstrated, supporting the importance of the diffusion-reaction properties modelled to the sensing mechanism, and the potential of developing a predictive tool based on the models presented is discussed.

In this paper we report about the peculiarities of thermodynamic functions of quantum electron gas in layered crystals. In such materials the conductivity along the layers exceeds by several orders the conductivity across layers. To these structures depend layered materials: YTe3, LaTe3, CeTe3, InSe, which are considered at low temperatures, as well as a number of organic conductors. There are many theoretical and experimental papers, indicated coexistence of equipotential energy surfaces of electrons in the form of corrugated cylinders and corrugated sheets. The thermodynamic functions for quantum electron gas are evaluated and compared for two different dependences of energy on momentum. The same parameters are used in both models – they are effective masses and translation vectors for β - GaSe. Our investigations allowed explaining the temperature dependence of resistivity for strong anisotropic and isotropic crystals at law temperatures, received by experiment. We also analyzed the specific heat in such crystals and explained the anomaly, observed in such crystals and illustrated the imperfection of the Debye model.

Thesis (M.S.)--West Virginia University, 2009.
Title from document title page. Document formatted into pages; contains vii, 40 p. : col. ill. Includes abstract. Includes bibliographical references (p. 39-40).

The J-laying technique for the construction of offshore pipelines requires a fast welding process that can produce sound welds in the horizontal-vertical position. The suitability of narrow gap gas metal arc welding (NG-GMA W) process for this application was previously demonstrated. The present programme studied the influence of process parameters on the fusion characteristics of NG-GMA welding in a range of different shielding gas compositions and welding positions. Statistical techniques were employed for both designing the experimental programme and to process the data generated. A partial factorial design scheme was used to investigate the influence of input variables and their interaction in determining weld bead shape. Modelling equations were developed by multiple linear regression to represent different characteristics of the weld bead. Transformation of the response variable based on the Cox-Box method was commonly used to simplify the model format. Modelling results were analysed by graphical techniques including surface plots and a multiplot approach was developed in order to graphically assess the influence of up to four input variables on the bead shape. Conditions for acceptable bead formation were determined and the process sensitivity to minor changes in input parameters assessed. Asymmetrical base metal fusion in horizontalvertical welding is discussed and techniques to improve fusion presented. At the same time, the interaction between the power supply output characteristic and the bead geometry was studied for narrow gap joints and the effect of shielding gas composition on both process stability and fusion of the base metal was assessed. An arc instability mode that is strongly influenced by arc length, power supply characteristic and shielding gas composition was demonstrated and its properties investigated. An optimized shielding gas composition for narrow gap process was suggested.

The main hypothesis tested in this work is:

“It is possible to operate future Norwegian natural gas transportation systems at a level that is approximately optimal, technically and economically, with major stakeholders duly attending to requirements specified in the Norwegian statutory framework and in the implemented “Gas Directive.”

In order to test this hypothesis a multidisciplinary systems approach has been applied that includes analyses based on fluidmechanics and thermodynamics, economic theory and constrained by the prevailing and future legislative requirements. Operational experiences and empirical data also support the analyses.

It is assumed in this work that the introduction of the European Union’s Gas Directive will result in some new or altered legal requirements for how to conduct future Norwegian natural gas transport operations. The work has identified these new requirements and the work has suggested realistic solutions for how to conduct future operations. The author therefore concludes that the main hypothesis above is true provided five recommendations are observed.

The first recommendation is to implement into the Norwegian legislation provisions that make possible two core requirements of the Gas Directive. The first provision is to allow domestic gas sellers to compete in the downstream market by marketing and selling their gas individually. The second provision is to allow access to the transportation systems for those stakeholders who according to the Gas Directive are defined as “eligible customers” and “natural gas undertakings”, i.e. the future shippers.

The second recommendation follows as consequence of the latter provision and it recommends the future Norwegian regulatory regime to incorporate three main features. First, the transportation system is to be operated by an organization unit that has a transparent account on its transportation services or alternatively by an organization (i.e. the operator) that is functionally separated from and does not participate in any gas marketing and sales activities.

Secondly, and due to the fact that the Norwegian natural gas transportation systems are highly physically integrated it is recommended to have one and only one transportation system operator. Only one operator will be in the best position to enhance cost efficiency in daily operations, energy efficiency, resource management in daily operations, optimized utilization and optimized gas blending.

Thirdly, new and altered transportation services must be designed to meet the future needs and requirements of the shippers and these services must be offered to all shippers. The latter feature is elaborated in the third recommendation.

The third recommendation is to redefine and develop new transportation services that support shippers’ elastic demands for transportation services, both during periods of sufficient capacity as well as during peak load periods.

The above recommendation will imply that the future transportation services must comprise firm services i.e. booked and guaranteed transportation, and interruptible services i.e. transportation being interrupted either during off-peak periods or during peak periods as well as peak load services i.e. transportation services offered during peak load periods. The services must be offered to all shippers in an equal and impartial manner and be supported by a transparent and feasible tariff and toll regime. The toll regime must feature several properties that ensure recovery of fixed costs, cost efficiency in operations and maintenance, and rationing efficiency and this work recommends that the future toll regime shall be reasonable and fair and cost-based.

This work has identified that the existing toll regime does not feature all of the above properties and this work therefore suggests that the existing toll regime is re-designed and extended to include new elements. The first recommendation is to re-design the existing toll formula so that it acts as a two-part toll for firm capacity.

The fixed part of the toll shall act as a booking charge or capacity charge and it shall cover the financial costs based on the historic investment costs for the pipeline systems. It shall also include the fixed (annual) operations and maintenance costs, and any new costs for incremental new investments. The variable part of the toll may be set equal to average marginal costs per unit of gas, or be paid “in kind” as done in the current regime.

Further, a unitization of the fixed part of the firm toll is suggested here. The unitization shall include all pipelines that comprise the dry gas system. This means that the fixed part of the firm toll shall be calculated as an average fixed toll based on the historic investment costs for all the pipelines included. The unitization schema shall include the existing ship-or-pay contracts and any new firm contracts in the dry gas system.

The unitization will accomplish a possibility for eliminating specific shipper’s preferences for where to physically route gas in the dry gas system. This will subsequently improve rationing efficiency at high levels of utilization of the system when there is a concurrent need for auctioning of spare capacity. This is due to the physical behavior of the integrated system as any “internal” pre-booked routing in the system effectively may reduce the total throughput and thus a rationing efficient utilization of the system.

The above recommendations mean that the firm toll shall be charged as a “postage-stamp” toll for all pipeline systems comprising the dry gas systems. This means in practical terms that the dry gas system is to be considered as one zone only and pre-defined entry points and exit points must be established.

As a consequence of unitizing the toll for firm capacity either a unitization of the ownership structure must be done or a payment mechanism must be in force that secures the pipeline owners no extra profit or loss due to the introduction of unitization.

A new two-part toll formula that in its form is equal to the firm capacity toll is recommended for covering interruptible off-peak services. It is recommended to set the fixed part of the toll lower than the fixed part of the firm toll.

A new toll must be developed and be based on auctioning principles for allocation of spare capacity in the system during peak load periods. In order to facilitate the auction a tool is required for predicting the level of spare capacity that is available from time to time. This tool is also needed for optimizing the total throughput based on the different auction bids. In a similar manner as for the firm toll, the auction bids shall refer to a unitized dry gas system and the bids shall refer to transportation requests between any of the pre-defined entry and exits points. No shipper shall thus have a right to specify “internal” routing in the dry gas system.

The total revenues for the pipeline system owners shall not yield higher profits than the allowable regulated return and the balance shall be levied – at least in theory – the firm transportation shippers only. It is recommended to conduct such reallocations of revenues periodically.

The fourth recommendation is related to the necessity of changing documents and requirements, altering organizational forms and working processes, and how current incentive structures will be affected. All these issues will be influenced by an implementation of the Gas Directive. The work has briefly discussed these issues, but due to the many uncertainties no detailed assessments are conducted or recommendations given. The work has however indicated that a majority of the documents assessed in this work must be revised and updated to reflect the new requirements caused by liberalization. It is recommended here that the governing documents more clearly specify which new responsibilities the independent transportation system operator shall be assigned. A vital area of concern is how the transportation system operator and the shippers’ and sellers’ dispatching representatives shall communicate and perform their duties in the future. To day these functions are highly integrated, but liberalization will make them counterparts.

Further, a detailed specification of the future working processes for the independent transportation system operator must be clarified. This applies especially for the how to optimize the operations in a liberalized context. New and carefully designed incentives are needed for enhancing optimal usage of the network during capacity constraints.

The last recommendation regards allocative and dynamic efficiency in a liberalized context. In the prevailing regime the individual company acts normally both as shipper and pipeline system owner. This regime ensures proper incentives for cost efficient development of new capacity and cost efficient operations and this regime may continue to exist in a liberalized context. This regime will continue to create proper incentives for allocative and dynamic efficiently in a liberalized context as well.

Further, in order to enhance allocative and dynamic efficiency on the Norwegian Continental Shelf a centralized planning and development system must be in force in order to secure resource management and utilization of the significant conditions for economy of scale. The transportation system operator must have a close liaison with these functions in order to share information about operational experiences, capacity constraints and shadow prices on capacity of constraints.

Finally, the work has provided several observations that show how a systems approach is quite attractive for finding solutions to complex and multidisciplinary problems as considered in this work. The systems approach applied here consists of two engineering processes comprising well-defined activities. These activities comprise assessment of information, definition of effectiveness measures and creation of information models. Trade-offs are identified between contradicting requirements and the outcome of the processes is accurate descriptions of the systems operations in the prevailing context and to some extent also in a future context. The systems engineering processes have included several methodologies to solve specific tasks. Several analyses based on economic and technical theories are included, as imperative activities required for solving the problems.

The ultimate results of a systems approach are solutions that go beyond traditional and non-disciplinary approaches. This is particularly true if the objective is to find concrete and sound solutions applicable in a “real-world” context where specific stakeholders’ needs and legal requirements are present and well defined. Several observations are provided in the work showing how economic analyses are improved by combining them with technical theory, empirical data, operational experiences and last but not least: legal requirements.

More than 120 depleted natural gas reservoirs in Alberta, Canada have been identified as potential sites for CO₂ storage at temperature and pressure conditions at which CO₂ may form gas hydrate. Reservoir simulations presented in the literature have demonstrated the feasibility of storing CO₂ in such reservoirs. In this thesis, the injection of CO₂ in a laboratory size reservoir (packed bed of silica particles) serving as a physical model for a depleted reservoir was studied. The hypothesis was that injecting CO₂ into the reservoir at gas hydrate formation conditions will be beneficial in terms of increased CO₂ storage density. It is noted that CO₂ is stored not only as hydrate but also some is dissolved in the residual pore water (not converted to hydrate) and some as a gas in the remaining pore space. The results indicate that hydrate formation enhances the CO₂ storage density. The work also demonstrated that substances like tapioca starch added to the water in small quantities (1 wt %) delayed the onset of hydrate nucleation in the earlier stage but subsequently more CO₂ was stored as hydrate compared to the tapioca starch-free systems. The delay in nucleation decreases the risk to form a hydrate plug in the injection system. The injection of the CO₂-rich mixture (90 mol % CO₂/10 mol % N₂), which is a typical composition of a flue gas after CO₂ capture process, into a reservoir with CH4 (simulating residual natural gas) was also studied in the laboratory reservoir. It was found that the total CO₂ storage density (in hydrate, gaseous and dissolved state) decreased from 143 kg/m³ (the CO₂ injection into a CH₄ free reservoir) to 119 kg/m³. Finally, relevant phase equilibrium data were obtained in a constant volume high pressure vessel and by calorimetry. The results were found to be in good agreement with thermodynamic model calculated values within ± 40 kPa and ± 0.2 K, respectively.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate

This paper provides an update of our previous scaling relations between galaxy-integrated molecular gas masses, stellar masses, and star formation rates (SFRs), in the framework of the star formation main sequence (MS), with the main goal of testing for possible systematic effects. For this purpose our new study combines three independent methods of determining molecular gas masses from CO line fluxes, far-infrared dust spectral energy distributions, and similar to 1 mm dust photometry, in a large sample of 1444 star-forming galaxies between z = 0 and 4. The sample covers the stellar mass range log(M-*/M-circle dot) = 9.0-11.8, and SFRs relative to that on the MS, delta MS = SFR/SFR (MS), from 10(-1.3) to 10(2.2). Our most important finding is that all data sets, despite the different techniques and analysis methods used, follow the same scaling trends, once method-to-method zero-point offsets are minimized and uncertainties are properly taken into account. The molecular gas depletion time t(depl), defined as the ratio of molecular gas mass to SFR, scales as (1 + z)(-0.6) x (delta MS)(-0.44) and is only weakly dependent on stellar mass. The ratio of molecular to stellar mass mu(gas) depends on (1+ z)(2.5) x (delta MS)(0.52) x (M-*)(-0.36), which tracks the evolution of the specific SFR. The redshift dependence of mu(gas) requires a curvature term, as may the mass dependences of t(depl) and mu(gas). We find no or only weak correlations of t(depl) and mu(gas) with optical size R or surface density once one removes the above scalings, but we caution that optical sizes may not be appropriate for the high gas and dust columns at high z.

There is an ongoing interest in the use of metal oxides as regenerable sorbents for the removal of sulphur dioxide from flue gases. Cerium oxide on alumina has been suggested but few experimental data are available, particularly for the regeneration process. It has been shown that the overall stoichiometry of regeneration with hydrogen can be split into twelve reaction steps. These were deduced from an inspection of rate data and analysis of partially reduced samples by volumetric methods and using Fourier transform infra red spectroscopy. Below about 828 K, the hydrolysis of intermediate sulphides is rate limiting whilst, above that temperature, it is the formation of sulphides and/or the reduction of oxysulphates to cerium oxide which are important. The sulphation process has been investigated in the range 695 - 880 K. Observed reaction rates were interpreted both in terms of simple rate laws and using an adsorption/reaction mechanism. The latter was shown to be the most satisfactory for describing the reaction giving an activation energy of 46.5 kl/mol. The original diffuse - interface model for gas solid, non - catalytic reactions has been presented in dimensionless form and applied to reactions with various orders. This model was discussed in relation to the sharp - interface model. The effects of assuming different concentration profiles within the reaction zone were examined. Initial assumptions regarding the distribution of reactants in the reaction zone - whether linear or sigmoidal had little affect on the predictions of zone thicknesses and gaseous concentration profiles. No such agreement was found when exponential profiles were assumed. A new grain model has been developed in which it is assumed that a diffuse reacting interface, rather than a sharp - interface exists within the grains. Model equations were solved numerically and the effect of various reaction parameters on model predictions investigated. Some of the simplified techniques used previously to solve the grain model have been extended to the new model. A comparison of these with the numerical solution differed by a maximum of 12 %. Data relating to the regeneration in hydrogen of cerium sulphate on alumina, and also for the better known reaction with sulphur dioxide of copper oxide on alumina were analysed using the diffuse - interface shrinking core model and, for comparison, the volume reaction model. Both models provide a fairly good fit of the regeneration data. Energies of activation are in the range 190 to 210 kJ/moI. Both models fit data on the sulphation of copper oxide on alumina with reasonable accuracy with energies of activation ranging from 28 to 31.6 kJ/mol.