Browsing by Subject "Framework"
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Item A declarative framework for modeling multi-agent systems(2007-05) Gelfond, Gregory; Watson, Richard; Cooke, Daniel E.; Rushton, J. NelsonCurrent work in answer-set programming with regards to its application in the development of reasoning agents has centered around single-agent systems. A well established body of research showing its applicability towards such domains has been developed, describing a thorough methodology for their development upon a theoretical foundation. This work hopes to expand the applicability of this field to the realm of multi-agent domains. In this work we present a general framework for reasoning about cooperative multi-agent systems. We begin with an overview of the current framework for representing single-agent systems as well as the syntax and semantics of the logic programming language CR-Prolog. Once this baseline has been established, we extend the fundamental notion of an agent to facilitate communication via the introduction of special named sets of fluents known as requests. We then define the notions of an agent's local and global perspectives and their respective diagrams which serve as the theoretical foundation of this work. Once the general framework has been discussed, a motivating example of a simple multi-agent domain is presented. This example is used to develop a methodology for representing agents capable of reasoning in such domains using the logic programming language of CR-Prolog, together with an axiomatization of multi-agent communication. Finally a series of results detailing some fundamental properties of the framework are presented.Item Developments in modeling and optimization of production in unconventional oil and gas reservoirs(2015-05) Yu, Wei; Sepehrnoori, Kamy, 1951-; Chin, Lee; Delshad , Mojdeh; Mohanty, Kishore K; Patzek, Tadeusz WThe development of unconventional resources such as shale gas and tight oil exploded in recent years due to two key enabling technologies of horizontal drilling and multi-stage fracturing. In reality, complex hydraulic fracture geometry is often generated. However, an efficient model to simulate shale gas or tight oil production from complex non-planar fractures with varying fracture width along fracture length is still lacking in the petroleum industry. In addition, the pore size distributions for shale gas reservoirs and conventional gas reservoirs are quite different. The diffusivity equation of conventional gas reservoirs is not adequate to describe gas flow in shale reservoirs. Hence, a new diffusivity equation including the important transport mechanisms such as gas slippage, gas diffusion, and gas desorption is required to model gas flow in shale reservoirs. Furthermore, there are high cost and large uncertainty in the development of shale gas and tight oil reservoirs because of many uncertain reservoir properties and fracture parameters. Therefore, an efficient and practical approach to perform sensitivity studies, history matching, and economic optimization for the development of shale gas and tight oil reservoirs is clearly desirable. For tight oil reservoirs, the primary oil recovery factor is very low and substantial volumes of oil still remain in place. Hence, it is important to investigate the potential of CO₂ injection for enhanced oil recovery, which is a new subject and not well understood in tight oil reservoirs. In this research, an efficient semi-analytical model was developed by dividing fractures into several segments to approximately represent the complex non-planar fractures. It combines an analytical solution for the diffusivity equation about fluid flow in shale and a numerical solution for fluid flow in fractures. For shale gas reservoirs, the diffusivity equation of conventional gas reservoirs was modified to consider the important flow mechanisms such as gas slippage, gas diffusion, and gas desorption. The key effects of non-Darcy flow and stress-dependent fracture conductivity were included in the model. We verified this model against a numerical reservoir simulator for both rectangular fractures and planar fracture with varying width. The well performance and transient flow regime analysis between single rectangular fracture, single planar fracture with varying width, and single curving non-planar fracture were compared and investigated. A well from Marcellus shale was analyzed by combining non-planar fractures, which were generated from a three-dimensional fracture propagation model developed by Wu and Olson (2014a), and the semi-analytical model. Contributions to gas recovery from each gas flow mechanism were analyzed. The key finding is that modeling gas flow from non-planar fractures as well as modeling the important flow mechanisms in shale gas reservoirs is significant. This work, for the first time, combines the complex non-planar fracture geometry with varying width and all the important gas flow mechanisms to efficiently analyze field production data from Marcellus shale. We analyzed several core measurements for methane adsorption from some area in Marcellus shale and found that the gas desorption behaviors of this case study deviate from the Langmuir isotherm, but obey the BET (Brunauer, Emmett and Teller) isotherm. To the best of our knowledge, such behavior has not been presented in the literature for shale gas reservoirs to behave like multilayer adsorption. The effect of different gas desorption models on calculation of original gas in place and gas recovery prediction was compared and analyzed. We developed an integrated reservoir simulation framework to perform sensitivity analysis, history matching, and economic optimization for shale gas and tight oil reservoirs by integrating several numerical reservoir simulators, the semi-analytical model, an economic model, two statistical methods, namely, Design of Experiment and Response Surface Methodology. Furthermore, an integrated simulation platform for unconventional reservoirs (ISPUR) was developed to generate multiple input files and choose a simulator to run the files more easily and more efficiently. The fracture cost was analyzed based on four different fracture designs in Marcellus shale. The applications of this framework to optimize fracture treatment design in Marcellus shale and optimize multiple well placement in Bakken tight oil reservoir were performed. This framework is effective and efficient for hydraulic fracture treatment design and production scheme optimization for single well and multiple wells in shale gas and tight oil reservoirs. We built a numerical reservoir model to simulate CO₂ injection using a huff-n-puff process with typical reservoir and fluid properties from the Bakken formation by considering the effect of CO₂ molecular diffusion. The simulation results show that the CO₂ molecular diffusion is an important physical mechanism for improving oil recovery in tight oil reservoirs. In addition, the tight oil reservoirs with lower permeability, longer fracture half-length, and more heterogeneity are more favorable for the CO₂ huff-n-puff process. This work can provide a better understanding of the key parameters affecting the effectiveness of CO₂ huff-n-puff in the tight oil reservoirs.Item Evaluating academic integrity and outreach efforts: changes in perceptions over a three-year period(Texas Tech University, 2008-05) Canham, Andrew A.; Shonrock, Michael D.; Wang, Eugene W.; Burkhalter, James P.This study had two purposes: to determine whether academic integrity outreach efforts at a large, comprehensive public research institution were positively impacting the campus community and to explore academic integrity outreach frameworks in an effort to inform best practices. The study was significant because limited data were available about whether suggested campus outreach models produce positive results in terms of reducing academic dishonesty. A thorough examination of existing literature revealed only one similar study, conducted at a small, East Coast liberal arts school; however, the research design of this study differed in important ways. These were as follows: this study surveyed students and faculty at a large public research university in the SACS accrediting region; it did not use “forced- choice” options when seeking data from participants to prevent bias; and the use of open-ended questions informed the researcher as to why participants perceived certain actions should occur. The population for this study was all university students and faculty. The sample consisted of faculty and students enrolled between 2004 and 2007, classified sophomore through senior, at a large public research institution located in the southwestern United States and accredited by the Southern Association of Colleges and Schools (SACS). This study approached its research from a post-positivist perspective, using ANOVA and Pearson’s chi- square as the primary quantitative research design tools. Two open-ended questions informed the researcher and were analyzed using open-coding based upon grounded theory. Data were collected from 4,345 student and faculty participants. Two ANOVAs produced significant results: (a) the average student’s understanding of university policies concerning cheating and (b) the average faculty member’s understanding of university policies concerning cheating. The dependent variables were the academic integrity perceptions of students and faculty (survey questions) and the independent variable was the survey year. The Pearson’s chi-square analysis also produced a significant result, indicating that student participants in 2007 were 1.5 times more likely to have been informed about academic integrity than were their peers who had completed the survey in 2004. In addition, analysis of the first open-ended question (what outreach efforts were perceived to already be taking place) yielded 544 valid and useable returns. From those, 956 responses were generated, resulting in 119 unique answer codes. The second openended question (what outreach efforts should be used) resulted in 532 valid and useable returns. There were 1,002 responses within those returns, which resulted in 166 unique answer codes. Codes were subsequently combined into 18 categories and later narrowed into eight themes. Those eight themes were further analyzed, culminating in a proposed academic integrity outreach model that institutions and future researchers may explore.Item Framework for Understanding the Relationship between Lean and Safety in Construction(2011-08-08) Prakash, RamyaLean construction borrows concepts from lean manufacturing and Toyota Production System in order to eliminate waste and add value to the construction process. Manufacturing processes utilizing lean principles have matured and developed a clear understanding of the relation between lean and safety. Because lean in construction is a relatively new phenomenon, there is not a completely developed understanding of how lean practices affect safety in construction. The Lean Construction Institute and the Academic Forum for Lean Construction has recently targeted this area for focused research. Since all safety incidents imply waste in time and resources, lean and safety have a common ground in the minimization of waste. This thesis researches the common ground of lean and safety in waste minimization and proposes a framework for understanding their relationship. This thesis also critically analyzes lean and safety principles to form an insight to the relationship between lean theories as well as practices and safety issues reported in construction literature. Further, literature also revealed the safety strategies and checklists that companies typically incorporate in their program. A comparative analysis of lean and safety is employed to understand their relations in a better way. This framework establishes that lean and safety have a strong relationship in the context of construction. Future work is needed to show that lean practices indeed strongly affect safety by reducing the number of incidents.