Radiative Transfer Using Path Integrals for Multiple Scattering in Participating Media

The theory of light transport forms the basis by which many computer graphic renderers are implemented. The more general theory of radiative transfer has applications in the wider scientific community, including ocean and atmospheric science, medicine, and even geophysics. Accurately capturing multiple scattering physics of light transport is an issue of great concern. Multiple scattering is responsible for indirect lighting, which is desired for images where high realism is the goal. Additionally, multiple scattering is quite important for scientific applications as it is a routine phenomenon. Computationally, it is a difficult process to model. Many have developed solutions for hard surface scenes where it is assumed that light travels in straight paths, for example, scenes without participating media. However, multiple scattering for participating media is still an open question, especially in developing robust and general techniques for particularly difficult scenes. Radiative transfer can be expressed mathematically as a Feynman path integral (FPI), and we give background on how the transport kernel of the volume rendering equation can be written in terms of a FPI. To move this model into a numerical setting, we need numerical methods to solve the model. We start by focusing on the spatial and angular integrals of the volume rendering equation, and show a way to generate seed paths without regard as to if they are cast from the emitter or the sensor. Seed paths are converted into a discretized form, and we use an existing numerical method to tackle the FPI. A modified version of this technique shows how to reduce the running time from a quadratic to a linear expression. We then perform experimental analysis of the path integral calculation. The entire numerical method is put to full scale test on a distributed computing platform to calculate beam spread functions and compare the results to experimental data. The dissertation is laid out as follows. In Chapter 1, we introduce the basic concepts of light propagation for computer graphics, multiple scattering, and volume rendering. Chapter 2 offers background on the subject of FPIs and some mathematical techniques used in their numerical integration for this work. Chapter 3 is a survey of radiative transfer and multiple scattering as it is studied in computer graphics and elsewhere. Chapter 4 is a full description of the current methodology. In Section 4.1 we describe sensor and emitter geometries used for our experiments. We propose a new algorithm for creating seed paths to use in the numerical integration of the FPI in Section 4.2. Section 4.3 introduces past work in the numerical integration, formalizes it, and improves upon its running time. Section 4.4 presents some analysis of the path weighting. In Chapters 5 and 6 we run experiments using the numerical methods. The first characterizes the calculation of the path integral itself using arbitrary spatial parameters, and shows repeatability and unbiased calculation given enough samples. In the second, we calculate beam spread functions, a basic property of scattering media, and compare the calculations to experimentally acquired data. Chapter 7 presents a summary of contributions, a summary of conclusions, and future directions for the research

Environmental Impact Predictions for Disposal of Emerging Energy Technologies in Solid Waste Landfills: Application to Lithium Ion Batteries and Photovoltaic Modules

As the use of photovoltaic (PV) modules and batteries rapidly increases to meet the growing worldwide energy demand, so does the waste stream of these products at end-of-life (EOL). In locations without sufficient recycling laws or take-back programs, these products could be landfilled with municipal solid waste (MSW). To determine the potential effects from landfill disposal of these products, metal leaching from PV modules and two types of batteries (Li-ion and nickel metal hydride (NiMH)) was studied using the regulatory Toxicity Characteristic Leaching Procedure (TCLP) as well as batch leaching and outdoor column testing. The data from the leaching tests were used to build waste scenarios utilizing life cycle assessment (LCA) software. The experimental data collected from the batch leaching tests and outdoor columns in Chapters 4, 5, and 7 demonstrate the complexity of characterizing PV and battery e-waste and developing EOL regulations and procedures that are applicable to each type of e-waste. In Chapter 4, the TCLP, the California Waste Extraction Test, and modified versions of both were performed on a multi-crystalline silicon module and cells and a copper indium gallium diselenide (CIGS) module. Metal leachate concentrations varied with changes in testing parameters, which raises doubt if regulatory methods can adequately characterize PV modules. In Chapter 5, the TCLP, microwave digestions, and batch leaching tests in two simulated leachates sampled over a period of 100 days were conducted for seven types of Li-ion batteries, one type of NiMH battery, and two types of PV modules. Additionally, one product of each type (Li-ion battery, NiMH battery, and PV module) was mixed with MSW components and a simulated landfill leachate to compare leaching in a more realistic waste matrix to the batch leaching tests. Results from the TCLP showed that one of the two PV modules and three of the eight batteries would be classified as hazardous waste in the US. For the batch tests with e-waste mixed with MSW, both lower (Pb and Hg) and higher (Co and Ni) metal leachate concentrations were observed than for the batch tests without MSW. Chapter 6 describes the design and build of the lysimeter test bed, which is utilized for column experiments in Chapter 7. Three columns were built to simulate the conditions within a bioreactor solid waste landfill and were subjected to outdoor temperature fluctuations. For the column with the c-Si module pieces, Pb was not detected in the leachate even though Pb was observed in the previous tests for this product described in Chapter 5. For the column with the NiMH power tool battery, Co, Cu, and Ni were measured in the leachate, but As, Hg, Pb, and Zn were not detected in the column leachate samples even though they were observed in the previous tests. For the column with the Li-ion laptop battery, Co, Cu, and Ni were measured in the leachate samples and were also found in the previous batch tests. Although As, Hg, and Pb were not found in the leachate samples, the other soluble and potentially mobile metals, including Co, Cu, and Ni, found in the leachate could be of concern in an improperly managed landfill and could cause contamination of soils and aquifers. In Chapter 8, the data gathered from the leaching tests were used to build EOL scenarios for metal emissions to groundwater using LCA software and characterization methods to determine potential human and eco-toxicity effects. Additionally, composition data from disassembly and digestions were used to build assemblies of the PV module and Li-ion and NiMH batteries. The results showed that the worst-case EOL scenario effects exceeded those of the assemblies of each product, and with notable effects for the other scenarios, the inclusion of the potential for EOL metal leaching is merited in LCAs of these products. Appropriate characterization tools and techniques to ensure adequate protection of the environment are necessary to avoid a growing e-waste problem while simultaneously promoting renewable energy sources

The effect of carbonate karst terrain on water quality

The ever increasing use of water and unabated pollution of streams have made necessary increased research efforts into the quality and quantity of the available national water resources. Karst terrain is prevalent in several sections of the United States, however, little work has been done on the effect of this topography on water quality. The purpose of this investigation was to determine the effect of carbonate karst terrain on the quality of water. The Meramec spring area, east of Rolla, Missouri, was selected for study. This area was underlain with dolomite formations and contains both karst and non-karst drainage basins which made possible comparative studies. Stream, well, and spring waters from the study area were characterized using chemical, physical, and bacteriological determinations and the results obtained were evaluated. Water in carbonate karst terrain was found to contain primarily calcium and magnesium bicarbonate, with nitrate ions and iron often reaching significant concentrations in underground supplies. Increases in the mineral content of stream waters at some locations after rainfall indicated that subsurface discharges were feeding the streams. Direct pathways from the surface to the groundwater were established. when coliform organisms were found in the spring and well water samples --Abstract

Black, white, and blue : media and audience frames from visual news coverage of police use of force and unrest

This study advances visual framing theory by uncovering the relationship between media and audience frames. This work uses recent media coverage of police brutality and social unrest to understand how audiences interpreted visual messages and frames, highlighting the differences in these interpretations for Black and White audiences. A secondary content analysis explores how digital news outlets portrayed the issue visually. In addition, this dissertation examines the role social media audiences play in redistributing media content in social media venues through sharing features. These research objectives were tackled using a two-part, mixed-methods approach. The first study utilized think-aloud interviews with Black and White participants to examine how audiences understood visual information. Results show media frames help organize information for audiences, while interpretations and evaluations of visual messages were less uniform. White and Black participants treated visualizations of police with increased skepticism. Participants also noted small details that indicate criminality for Blacks. Visuals also play a critical role in interrogating structure of the protest paradigm. Yet, evaluations of images within this genre of news varied considerably between Black and White participants. For White participants, rioting and chaos are primarily negative, while Black participants position their evaluations in more sympathetic, understanding terms. Non-violent visualizations also lead to various assessments. Black participants were overly-cautious of White thinking, acknowledging and opposing perceived negativity as a way of challenging the discourse they expect to encounter. These interpretations are evidence of dual-consciousness and confirm the consistency of a contest-and-oppose approach to evaluations. Whites are less likely to battle stereotypes or to oppose them through empathetic responses than Blacks. The second study includes a content analysis of digital news coverage shared on social media. Overall results for protest images were more likely emphasize the written demands of protesters and non-violent action of protestors than violence or sensational behavior. Identifying photos are also more balanced than expected. Regarding shareworthiness, visual messages did not affect social media audiences’ sharing patterns, though visuals that included human emotion were more likely to be shared on Facebook and Twitter.Journalis

William Wallace Duncan, an Appreciation

FOREWORD President John C. Kilgo, of Trinity College, prepared the contents of this volume to be presented in manuscript form to the members of Bishop Duncan\u27s family. He was for many years closely associated with Bishop Duncan and between them there existed the warmest and most intimate friendship. A number of Bishop Duncan\u27s friends and admirers expressed a desire to have a copy of this appreciation in permanent form, and Dr. Kilgo has kindly given us permission to have the manuscript printed. We are issuing this volume as a tribute of respect to one whose life and labors have been the richest benediction, and whose memory we cherish as a priceless heritage. It is very fitting that this tribute should come from Trinity College. He was one of its most loyal and sincere friends, and was an alumnus in that he received the degree of Doctor of Laws from the institution.https://digitalcommons.wofford.edu/collegebooks/1012/thumbnail.jp

Some Things that Belong to Methodism

Summary of Methodist work in England and in the United States and in South Carolina

Total arch replacement using moderate hypothermic circulatory arrest and unilateral selective antegrade cerebral perfusion

ObjectiveTo examine the clinical outcomes and impact of using moderate hypothermic circulatory arrest (MHCA) and unilateral selective antegrade cerebral perfusion (uSACP) in the setting of total aortic arch replacement (TOTAL).MethodsFrom 2004 to 2012, 733 patients underwent open arch reconstruction with MHCA and SACP. Of these, 145 (20%) underwent TOTAL. Measured outcomes included death, stroke, temporary neurologic dysfunction (TND), and renal failure. Mean follow-up time was 33 months and ranged from 0 to 95 months.ResultsCore temperature at the onset of MHCA was 25.8°C. Cardiopulmonary bypass and myocardial ischemic times were 236 minutes and 181 minutes, respectively. Twenty-three patients (16%) underwent emergency repair of acute type A dissection. Fifty-four cases (37%) were reoperative and 52 (34%) were stage I elephant trunk procedures. Concomitant root replacement was performed in 50 (35%) patients, including 20 David V valve-sparing procedures. Mean duration of circulatory arrest was 55 minutes. Operative mortality was 9.7%. Overall incidence of stroke and TND was 2.8% and 5.6%, respectively. Four patients (2.8%) required postoperative dialysis. Seven-year survival was significantly reduced (P = .04) after repair of type A dissection (83.8%) compared with elective surgery (89.5%). Higher temperature during TOTAL was not found to be a significant risk factor for adverse events.ConclusionsTOTAL using MHCA and uSACP can be accomplished with excellent early and late results. MHCA was not associated with adverse neurologic outcomes or higher operative risk, despite prolonged periods of circulatory arrest