Matching Items (18)

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Simulation of Atomic Structure around Defects in Anatase

Description

Titanium dioxide is an essential material under research for energy and environmental applications, chiefly through its photocatalytic properties. These properties allow it to be used for water-splitting, detoxification, and photovoltaics, in addition to its conventional uses in pigmentation and

Titanium dioxide is an essential material under research for energy and environmental applications, chiefly through its photocatalytic properties. These properties allow it to be used for water-splitting, detoxification, and photovoltaics, in addition to its conventional uses in pigmentation and sunscreen. Titanium dioxide exists in several polymorphic structures, of which the most common are rutile and anatase. We focused on anatase for the purposes of this research, due to its promising results for hydrolysis.

Anatase exists often in its reduced form (TiO2-x), enabling it to perform redox reactions through the absorption and release of oxygen into/from the crystal lattice. These processes result in structural changes, induced by defects in the material, which can theoretically be observed using advanced characterization methods. In situ electron microscopy is one of such methods, and can provide a window into these structural changes. However, in order to interpret the structural evolution caused by defects in materials, it is often necessary and pertinent to use atomistic simulations to compare the experimental images with models.

In this thesis project, we modeled the defect structures in anatase, around oxygen vacancies and at surfaces, using molecular dynamics, benchmarked with density functional theory. Using a “reactive” forcefield designed for the simulation of interactions between anatase and water that can model and treat bonding through the use of bond orders, different vacancy structures were analyzed and simulated. To compare these theoretical, generated models with experimental data, the “multislice approach” to TEM image simulation was used. We investigated a series of different vacancy configurations and surfaces and generated fingerprints for comparison with TEM experiments. This comparison demonstrated a proof of concept for a technique suggesting the possibility for the identification of oxygen vacancy structures directly from TEM images. This research aims to improve our atomic-level understanding of oxide materials, by providing a methodology for the analysis of vacancy formation from very subtle phenomena in TEM images.

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Date Created
2019-05

Development of Case Material for Confederates in Arizona State University Nursing Simulations

Description

This paper reviews a creative project designed to enhance the simulation experience for College of Nursing and Health Innovation nursing students at Arizona State University. Simulation allows students to practice imperative skills in a safe environment, free from the risk

This paper reviews a creative project designed to enhance the simulation experience for College of Nursing and Health Innovation nursing students at Arizona State University. Simulation allows students to practice imperative skills in a safe environment, free from the risk of injury to patients and the consequences of making these errors, in order to master skills that are essential in the clinical setting. Students are able to practice a wide range of invasive and noninvasive skills and hone in on their clinical judgement and critical thinking to make decisions that may be life threatening in a clinical situation. The group members designed written training materials and created corresponding video vignettes that would be utilized to enhance the confederate role and provide the students a deeper understanding of their simulated patient and the simulation scenario. The written training materials that were developed include confederate background information, patient and family education, and guided questions and answers for the video vignettes. The written training materials will be used to guide the students that are portraying the family member during the simulation. Trained standardized patients were hired to play the confederate role in the four video vignettes. The video vignettes portrayed interviews with a family member of the patient that delved into how they felt about their family member's hospitalization and what they hoped to learn from the nurses during their family member's hospitalization. The vignettes will be used to guide students to the needs of the patients and families in the corresponding scenarios. These vignettes will be accessible by students before the start of simulation in order to enhance understanding of the patient and ultimately, the scenario.

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Date Created
2018-12

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Simulations of Pressure Swing Adsorption of Methane - Carbon Dioxide System

Description

Separation of carbon dioxide and methane for the upgrade of natural gas through use of pressure swing adsorption could potentially save large amounts of energy from the current, costly process of cryogenic distillation and provides greater cost effectiveness for carbon

Separation of carbon dioxide and methane for the upgrade of natural gas through use of pressure swing adsorption could potentially save large amounts of energy from the current, costly process of cryogenic distillation and provides greater cost effectiveness for carbon dioxide capture, and provide larger product flowrates than membrane permeation separation. The purpose of this study is to analyze the effects of varying initial conditions of a MatLab simulation, courtesy of Mai Xu, a graduate student at ASU, designed to use Langmuir isotherms, mass transfer equations, and adsorbent and gas properties to simulate a pressure swing adsorption process with a mixture of methane and carbon dioxide gas feed. The effects that will be varied are the adsorption/desorption time, pressurization/depressurization time, adsorption feed composition, desorption purge composition, adsorption pressure, desorption pressure, adsorption flow rate, and desorption flow rate. The study found that the trends in methane purity and production generally follow the trends predicted by literature and relevant equations, with pressure boundaries being the largest impacting factor. In addition there was a markedly inverse correlation between purity of methane product and the productivity of the system. This trend was only violated in one instance, at very low vacuum pressure during desorption, which could indicate an area that requires further study. Overall, the main areas of improvement in pressure swing adsorption for this system would be improving the selectivity of adsorption of carbon dioxide over methane, which requires improvement and change of the adsorbent, and more extreme vacuum pressures during desorption, both of which will increase methane yield and reduce operating costs.

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Date Created
2018-05

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A Modelling Approach to Determine Gas and Temperature Profiles during Catalytic Reactions in Environmental Transmission Electron Microscopy

Description

A scheme has been developed for finding the gas and temperature profiles in an environmental transmission electron microscope (ETEM), using COMSOL Multiphysics and the finite element method (FEM). This model should permit better correlation between catalyst structure and activity, by

A scheme has been developed for finding the gas and temperature profiles in an environmental transmission electron microscope (ETEM), using COMSOL Multiphysics and the finite element method (FEM). This model should permit better correlation between catalyst structure and activity, by providing a more accurate understanding of gas composition than the assumption of homogeneity typically used. While more data is needed to complete the model, current progress has identified several details about the system and its ideal modeling approach.
It is found that at the low pressures and flowrates of catalysis in ETEM, natural and forced convection are negligible forms of heat transfer. Up to 250 °C, radiation is also negligible. Gas conduction, being enhanced at low pressures, dominates.
Similarly, mass transport is dominated by diffusion, which is most accurately described by the Maxwell-Stefan model. Bulk fluid flow is highly laminar, and in fact borders the line between continuum and molecular flow. The no-slip boundary condition does not apply here, and both viscous slip and thermal creep must be considered. In the porous catalyst pellet considered in this work, Knudsen diffusion dominates, with bulk flow being best described by the Darcy-Brinkman equation.
With these physics modelled, it appears as though the gas homogeneity assumption is not completely accurate, breaking down in the porous pellet where reactions occur. While these results are not yet quantitative, this trend is likely to remain in future model iterations. It is not yet clear how significant this deviation is, though methods are proposed to minimize it if necessary.
Some model-experiment mismatch has been found which must be further explored. Experimental data shows a pressure dependence on the furnace temperature at constant power, a trend as-yet unresolvable by the model. It is proposed that this relates to the breakdown of the assumption of fluid continuity at low pressures and small dimensions, though no compelling mathematical formulation has been found. This issue may have significant ramifications on ETEM and ETEM experiment design.

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Date Created
2017-05

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A Simulation Model of the Effect of Workplace Structure on Productivity

Description

Workplace productivity is a result of many factors, and among them is the setup of the office and its resultant noise level. The conversations and interruptions that come along with converting an office to an open plan can foster innovation

Workplace productivity is a result of many factors, and among them is the setup of the office and its resultant noise level. The conversations and interruptions that come along with converting an office to an open plan can foster innovation and creativity, or they can be distracting and harm the performance of employees. Through simulation, the impact of different types of office noise was studied along with other changing conditions such as number of people in the office. When productivity per person, defined in terms of mood and focus, was measured, it was found that the effect of noise was positive in some scenarios and negative in others. In simulations where employees were performing very similar tasks, noise (and its correlates, such as number of employees), was beneficial. On the other hand, when employees were engaged in a variety of different types of tasks, noise had a negative overall effect. This indicates that workplaces that group their employees by common job functions may be more productive than workplaces where the problems and products that employees are working on are varied throughout the workspace.

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Date Created
2017-05

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Blockchain Design and Simulation

Description

This paper details the specification and implementation of a single-machine blockchain simulator. It also includes a brief introduction on the history & underlying concepts of blockchain, with explanations on features such as decentralization, openness, trustlessness, and consensus. The introduction features

This paper details the specification and implementation of a single-machine blockchain simulator. It also includes a brief introduction on the history & underlying concepts of blockchain, with explanations on features such as decentralization, openness, trustlessness, and consensus. The introduction features a brief overview of public interest and current implementations of blockchain before stating potential use cases for blockchain simulation software. The paper then gives a brief literature review of blockchain's role, both as a disruptive technology and a foundational technology. The literature review also addresses the potential and difficulties regarding the use of blockchain in Internet of Things (IoT) networks, and also describes the limitations of blockchain in general regarding computational intensity, storage capacity, and network architecture. Next, the paper gives the specification for a generic blockchain structure, with summaries on the behaviors and purposes of transactions, blocks, nodes, miners, public & private key cryptography, signature validation, and hashing. Finally, the author gives an overview of their specific implementation of the blockchain using C/C++ and OpenSSL. The overview includes a brief description of all the classes and data structures involved in the implementation, including their function and behavior. While the implementation meets the requirements set forward in the specification, the results are more qualitative and intuitive, as time constraints did not allow for quantitative measurements of the network simulation. The paper concludes by discussing potential applications for the simulator, and the possibility for future hardware implementations of blockchain.

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Date Created
2017-12

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A Strategy for Improved Traffic Flow

Description

Commuting is a significant cost in time and in travel expenses for working individuals and a major contributor to emissions in the United States. This project focuses on increasing the efficiency of an intersection through the use of "light metering."

Commuting is a significant cost in time and in travel expenses for working individuals and a major contributor to emissions in the United States. This project focuses on increasing the efficiency of an intersection through the use of "light metering." Light metering involves a series of lights leading up to an intersection forcing cars to stop further away from the final intersection in smaller queues instead of congregating in a large queue before the final intersection. The simulation software package AnyLogic was used to model a simple two-lane intersection with and without light metering. It was found that light metering almost eliminates start-up delay by preventing a long queue to form in front of the modeled intersection. Shorter queue lengths and reduction in the start-up delays prevents cycle failure and significantly reduces the overall delay for the intersection. However, frequent deceleration and acceleration for a few of the cars occurs before each light meter. This solution significantly reduces the traffic density before the intersection and the overall delay but does not appear to be a better emission alternative due to an increase in acceleration. Further research would need to quantify the difference in emissions for this model compared to a standard intersection.

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Date Created
2018-05

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Cost Driven Agent Based Simulation of the Department of Defense Acquisition System

Description

The Department of Defense (DoD) acquisition system is a complex system riddled with cost and schedule overruns. These cost and schedule overruns are very serious issues as the acquisition system is responsible for aiding U.S. warfighters. Hence, if the acquisition

The Department of Defense (DoD) acquisition system is a complex system riddled with cost and schedule overruns. These cost and schedule overruns are very serious issues as the acquisition system is responsible for aiding U.S. warfighters. Hence, if the acquisition process is failing that could be a potential threat to our nation's security. Furthermore, the DoD acquisition system is responsible for proper allocation of billions of taxpayer's dollars and employs many civilians and military personnel. Much research has been done in the past on the acquisition system with little impact or success. One reason for this lack of success in improving the system is the lack of accurate models to test theories. This research is a continuation of the effort on the Enterprise Requirements and Acquisition Model (ERAM), a discrete event simulation modeling research on DoD acquisition system. We propose to extend ERAM using agent-based simulation principles due to the many interactions among the subsystems of the acquisition system. We initially identify ten sub models needed to simulate the acquisition system. This research focuses on three sub models related to the budget of acquisition programs. In this thesis, we present the data collection, data analysis, initial implementation, and initial validation needed to facilitate these sub models and lay the groundwork for a full agent-based simulation of the DoD acquisition system.

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Date Created
2016-05

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Scandal: An Ethics Game on the Importance of Accurate GAAP and FASB Reporting for Public Corporations

Description

Financial statements are one of the most important, if not the most important, documents for investors. These statements are prepared quarterly and yearly by the company accounting department, and are then audited in detail by a large external accounting firm.

Financial statements are one of the most important, if not the most important, documents for investors. These statements are prepared quarterly and yearly by the company accounting department, and are then audited in detail by a large external accounting firm. Investors use these documents to determine the value of the company, and trust that the company was truthful in its statements, and the auditing firm correctly audited the company's financial statements for any mistakes in their books and balances. Mistakes on a company's financial statements can be costly. However, financial fraud on the statements can be outright disastrous. Penalties for accounting fraud can include individual lifetime prison sentences, as well as company fines for billions of dollars. As students in the accounting major, it is our responsibility to ensure that financial statements are accurate and truthful to protect ourselves, other stakeholders, and the companies we work for. This ethics game takes the stories of Enron, WorldCom, and Lehman Brothers and uses them to help students identify financial fraud and how it can be prevented, as well as the consequences behind unethical decisions in financial reporting. The Enron scandal involved CEO Kenneth Lay and his predecessor Jeffery Skilling hiding losses in their financial statements with the help of their auditing firm, Arthur Andersen. Enron collapsed in 2002, and Lay was sentenced to 45 years in prison with his conspirator Skilling sentenced to 24 years in prison. In the WorldCom scandal, CEO Bernard "Bernie" Ebbers booked line costs as capital expenses (overstating WorldCom's assets), and created fraudulent accounts to inflate revenue and WorldCom's profit. Ebbers was sentenced to 25 years in prison and lost his title as WorldCom's Chief Executive Officer. Lehman Brothers took advantage of a loophole in accounting procedure Repo 105, that let the firm hide $50 billion in profits. No one at Lehman Brothers was sentenced to jail since the transaction was technically considered legal, but Lehman was the largest investment bank to fail and the only large financial institution that was not bailed out by the U.S. government.

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Date Created
2016-05

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Modeling of Engineered Shock Absorbing Materials

Description

The main field of study research through this project is to study the effect of history of deformation in materials subjected to complex loading, useful for producing lightweight alloys and composites optimized for absorbing shock and impact. This is accomplished

The main field of study research through this project is to study the effect of history of deformation in materials subjected to complex loading, useful for producing lightweight alloys and composites optimized for absorbing shock and impact. This is accomplished by creating a digital model of a system in which the material undergoes tension and compression through colliding bars. The results show that the system generated is accurate when compared to real tests, so the program used to create the model can be used in the future for simulated tests using different materials or applied loads.

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Date Created
2014-05