Matching Items (7)

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Squeezing Out Electricity: Computer-Aided Design and Optimization of Electrodes of Solid Oxide Fuel Cells

Description

Solid oxide fuel cells have become a promising candidate in the development of high-density clean energy sources for the rapidly increasing demands in energy and global sustainability. In order to

Solid oxide fuel cells have become a promising candidate in the development of high-density clean energy sources for the rapidly increasing demands in energy and global sustainability. In order to understand more about solid oxide fuel cells, the important step is to understand how to model heterogeneous materials. Heterogeneous materials are abundant in nature and also created in various processes. The diverse properties exhibited by these materials result from their complex microstructures, which also make it hard to model the material. Microstructure modeling and reconstruction on a meso-scale level is needed in order to produce heterogeneous models without having to shave and image every slice of the physical material, which is a destructive and irreversible process. Yeong and Torquato [1] introduced a stochastic optimization technique that enables the generation of a model of the material with the use of correlation functions. Spatial correlation functions of each of the various phases within the heterogeneous structure are collected from a two-dimensional micrograph representing a slice of a solid oxide fuel cell through computational means. The assumption is that two-dimensional images contain key structural information representative of the associated full three-dimensional microstructure. The collected spatial correlation functions, a combination of one-point and two-point correlation functions are then outputted and are representative of the material. In the reconstruction process, the characteristic two-point correlation functions is then inputted through a series of computational modeling codes and software to generate a three-dimensional visual model that is statistically similar to that of the original two-dimensional micrograph. Furthermore, parameters of temperature cooling stages and number of pixel exchanges per temperature stage are utilized and altered accordingly to observe which parameters has a higher impact on the reconstruction results. Stochastic optimization techniques to produce three-dimensional visual models from two-dimensional micrographs are therefore a statistically reliable method to understanding heterogeneous materials.

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Created

Date Created
  • 2016-05

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New Orleans and the Black Press: How New Orleans impacted Reconstruction Policy in America

Description

In the years after the American Civil War, New Orleans became an important city in regards to racial turmoil and political futures. Three separate riots, each taking place between the

In the years after the American Civil War, New Orleans became an important city in regards to racial turmoil and political futures. Three separate riots, each taking place between the years of 1866-1874, came to be defining moments in the greater pantheon of Reconstruction politics. Each of these riots had major impacts on the political climate of the day, with national implications that stretched far beyond just the city of New Orleans.

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Created

Date Created
  • 2013-12

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African American Experience During Texas Reconstruction: Analysis of Texas Institutions and the Political Career of George T. Ruby

Description

Analysis into the political career of Texas state senator George Ruby provides invaluable insight to the African American experience during Reconstruction in Texas as a whole. Juxtaposing the needs vocalized

Analysis into the political career of Texas state senator George Ruby provides invaluable insight to the African American experience during Reconstruction in Texas as a whole. Juxtaposing the needs vocalized by African American communities and the actions taken by Ruby, the Freedmen’s Bureau, and other Texas politicians, helps identify how racial politics dictated the lives of Texas African Americans. Ruby’s rise to power can also be utilized as a historical blueprint for how leaders in marginalized communities can become impactful and obtain power within a racially-biased societal structure. Ruby’s rise and fall in Texas politics is tragic as he finds himself forced to separate from his loyal African American support base—deciding to cater to the needs of elite white Texans to help ensure political favor on both sides of the political and racial spectrum. However, Ruby’s legacy remains one of great success as he managed to break the mold forced upon so many African Americans during Reconstruction and enact lasting change in the marginalized Texas African American communities.

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Created

Date Created
  • 2018-05

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Magnetic resonance parameter assessment from a second order time-dependent linear model

Description

This dissertation develops a second order accurate approximation to the magnetic resonance (MR) signal model used in the PARSE (Parameter Assessment by Retrieval from Single Encoding) method to recover information

This dissertation develops a second order accurate approximation to the magnetic resonance (MR) signal model used in the PARSE (Parameter Assessment by Retrieval from Single Encoding) method to recover information about the reciprocal of the spin-spin relaxation time function (R2*) and frequency offset function (w) in addition to the typical steady-state transverse magnetization (M) from single-shot magnetic resonance imaging (MRI) scans. Sparse regularization on an approximation to the edge map is used to solve the associated inverse problem. Several studies are carried out for both one- and two-dimensional test problems, including comparisons to the first order approximation method, as well as the first order approximation method with joint sparsity across multiple time windows enforced. The second order accurate model provides increased accuracy while reducing the amount of data required to reconstruct an image when compared to piecewise constant in time models. A key component of the proposed technique is the use of fast transforms for the forward evaluation. It is determined that the second order model is capable of providing accurate single-shot MRI reconstructions, but requires an adequate coverage of k-space to do so. Alternative data sampling schemes are investigated in an attempt to improve reconstruction with single-shot data, as current trajectories do not provide ideal k-space coverage for the proposed method.

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Created

Date Created
  • 2019

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Alternative slaveries and American democracy: debt bondage and Indian captivity in the Civil War era Southwest

Description

This dissertation analyzes two regional systems of involuntary servitude (Indian captive slavery and Mexican debt peonage) over a period spanning roughly two centuries. Following a chronological framework, it examines the

This dissertation analyzes two regional systems of involuntary servitude (Indian captive slavery and Mexican debt peonage) over a period spanning roughly two centuries. Following a chronological framework, it examines the development of captive slavery in the Southwest beginning in the early 1700s and lasting through the mid-1800s, by which time debt peonage emerged as a secondary form of coerced servitude that augmented Indian slavery in order to meet increasing demand for labor. While both peonage and captive slavery had an indelible impact on cultural and social systems in the Southwest, this dissertation places those two labor systems within the context of North American slavery and sectional agitation during the antebellum period. The existence of debt bondage and Indian captivity in New Mexico had a significant impact on America's judicial and political institutions during the Reconstruction era.

Debt peonage and Indian slavery had a lasting influence on American politics during the period 1846 to 1867, forcing lawmakers to acknowledge the fact that slavery existed in many forms. Following the Civil War, legislators realized that the Thirteenth Amendment did not cast a wide enough net, because peonage and captive slavery were represented as voluntary in nature and remained commonplace throughout New Mexico. When Congress passed a measure in 1867 explicitly outlawing peonage and captive slavery in New Mexico, they implicitly acknowledged the shortcomings of the Thirteenth Amendment. The preexistence of peonage and Indian slavery in the Southwest inculcated a broader understanding of involuntary labor in post-Civil War America and helped to expand political and judicial philosophy regarding free labor. These two systems played a crucial role in America's transition from free to unfree labor in the mid-1800s and contributed to the judicial and political frameworks that undermined slavery.

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Created

Date Created
  • 2016

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The Pitfalls and Potholes of Reconstruction: Understanding the Role of Infrastructure in Post-Conflict Reconstruction

Description

National infrastructure form the bedrock for economic growth and social security, both of which lowers conflict risks. This encourages states and international organizations to invest heavily in post-conflict infrastructure reconstruction

National infrastructure form the bedrock for economic growth and social security, both of which lowers conflict risks. This encourages states and international organizations to invest heavily in post-conflict infrastructure reconstruction efforts, believing that infrastructure provision will reduce future political instability. This belief is based largely on the perceived successes of reconstruction efforts in prior eras, especially after World War II. Today, post-conflict reconstruction efforts are much less successful in this regard and, overall, are not reducing political instability---Iraq being the quintessential example of such policy failure. In the face of both ongoing conflict and persistent needs for infrastructure reconstruction after conflicts, therefore, there is a critical need to understand two questions: Why are current reconstruction efforts failing to reduce political instability or even, in some cases, increasing it? And, how can reconstruction efforts be organized to do better? To address these questions, this dissertation examines infrastructure reconstruction across a wide range of national contexts. In doing this, an updated viewpoint is provided on the role of infrastructure in conflict-prone areas to include a long-term perspective on infrastructure system's role in society, technological integration, and relationship between the state and conflicting groups. This dissertation finds that though provision of different types of infrastructure might increase conflict risks in the short term, such provision can reduce conflict in the long run depending on how and where infrastructure is provided vis-a-vis excluded populations. These results provide crucial input towards the redesign of reconstruction policies to limit future political instability risks through infrastructure.

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Created

Date Created
  • 2014

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3D rooftop detection and modeling using orthographic aerial images

Description

Detection of extruded features like rooftops and trees in aerial images automatically is a very active area of research. Elevated features identified from aerial imagery have potential applications in urban

Detection of extruded features like rooftops and trees in aerial images automatically is a very active area of research. Elevated features identified from aerial imagery have potential applications in urban planning, identifying cover in military training or flight training. Detection of such features using commonly available geospatial data like orthographic aerial imagery is very challenging because rooftop and tree textures are often camouflaged by similar looking features like roads, ground and grass. So, additonal data such as LIDAR, multispectral imagery and multiple viewpoints are exploited for more accurate detection. However, such data is often not available, or may be improperly registered or inacurate. In this thesis, we discuss a novel framework that only uses orthographic images for detection and modeling of rooftops. A segmentation scheme that initializes by assigning either foreground (rooftop) or background labels to certain pixels in the image based on shadows is proposed. Then it employs grabcut to assign one of those two labels to the rest of the pixels based on initial labeling. Parametric model fitting is performed on the segmented results in order to create a 3D scene and to facilitate roof-shape and height estimation. The framework can also benefit from additional geospatial data such as streetmaps and LIDAR, if available.

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Created

Date Created
  • 2013