Simulation of Polymer Molecular Weight Distributions in Industrial Reactors

Polyethylene is commonplace in the modern world; thus, manufacturers constantly search for improvements to their production processes. However, because of the exothermic nature of ethylene, process intensification poses both safety and financial risks. This encourages the use of simulation techniques for the improvement of these systems. However, due to their simplifying assumptions, software designed specifically for polymer reactors have limited usefulness. Computational Fluid Dynamics (CFD) is an attractive alternative, because it is much more rigorous. Although, implementing polymerization chemistry into CFD is not a trivial task. The Method of Moments makes this possible but necessarily removes the polymer\u27s Molecular Weight Distribution (MWD) from the simulation. The first few moments of the distribution can be used to approximate the MWD if the shape of the distribution is assumed, but this technique often fails to reproduce the bimodal distributions typical of industrial polymers. To better reconstruct the MWD, the distribution can be divided into various classes based on their degree of branching, each of which have their own MWD. These can then be summed to approximate the overall polymer distribution. This method was implemented into a simplified CFD reactor model and tested using 5 and 10 polymer classes. The number of classes, assumed distribution shape, and summation method all had a significant impact on the subsequent distribution. Ultimately, a multimodal polymer MWD was achieved that was qualitatively like distributions found in the literature. These results need to be compared to experimental data to determine the appropriate combination of classes, assumed shape, and summation methodology for reliable results in future studies

Need For Control: Sensitivity of Polymerization Reactors

Free radical polymerization of Polyethylene is highly exothermic, having the largest adiabatic temperature rise of all commercial monomers. At high temperatures, the monomeric unit Ethylene can decompose into various hydrocarbons, producing even more heat. This decomposition can create a vessel pressure thousands of times larger than earth’s atmosphere, potentially leading to reactor explosions on the scale of earthquakes. Obviously, it is very important to ensure Polyethylene reactors are bounded, so their safe operating limits need to be determined. Since this is dangerous to do in experiment, it is often performed using computer simulations. This work uses Computational Fluid Dynamics (CFD) to develop a model for a Low-Density Polyethylene (LDPE) Continuous Stirred Tank Reactor (CSTR), for the purpose of determining safe reactor operating conditions. Because of the numerical approximations CFD employs, it can be difficult to obtain a stable and accurate model. The sensitive LDPE chemistry further complicates the stability requirements of this model. After a host of tests covering numerical settings, startup processes, kinetic simplifications, and reactor design, it was determined that a passive LDPE CSTR cannot be achieved in CFD. To illustrate this, two reactors that only differed in initial temperature by 0.01 K were modeled and compared. The temperature response of these models diverged from each other without bound. Because of this extreme sensitivity, active PID control was necessary for a stable CFD solution. The addition of Fuzzy Logic to the PID control improved the speed and stability of the model. The now stable LDPE CSTR model can be leveraged to determine safe reactor operating conditions

Implementation of Complex Low-Density Polyethylene Chemistry into Rigorous Computational Fluid Dynamics Model

Graduate Applie

Hot Spots: Quantifying Risk for Reactor Failure and a Measure for the Validity of the Lumped Capacitance Assumption

Graduate Three Minute Thesi

Theory and Applications Surrounding Markov Chains

This capstone project explores the Markov Chain – a mathematical model used to describe systems that transition between states based on probabilities. It begins by introducing the fundamental concepts, including transition matrices, state classifications, and stationary distributions. The paper then applies Markov Chain theory to real-world scenarios, such as simulating Snakes and Ladders games, predicting soccer match outcomes for Manchester United, and generating texts from movie lines. Finally, it discusses key findings, challenges, and potential areas for future research in the field

Developing a vocabulary and ontology for modeling insect natural history data: example data, use cases, and competency questions

Insects are possibly the most taxonomically and ecologically diverse class of multicellular organisms on Earth. Consequently, they provide nearly unlimited opportunities to develop and test ecological and evolutionary hypotheses. Currently, however, large-scale studies of insect ecology, behavior, and trait evolution are impeded by the difficulty in obtaining and analyzing data derived from natural history observations of insects. These data are typically highly heterogeneous and widely scattered among many sources, which makes developing robust information systems to aggregate and disseminate them a significant challenge. As a step towards this goal, we report initial results of a new effort to develop a standardized vocabulary and ontology for insect natural history data. In particular, we describe a new database of representative insect natural history data derived from multiple sources (but focused on data from specimens in biological collections), an analysis of the abstract conceptual areas required for a comprehensive ontology of insect natural history data, and a database of use cases and competency questions to guide the development of data systems for insect natural history data. We also discuss data modeling and technology-related challenges that must be overcome to implement robust integration of insect natural history data

A hymenopterists' guide to the hymenoptera anatomy ontology: utility, clarification, and future directions

Hymenoptera exhibit an incredible diversity of phenotypes, the result of ~240 million years of evolution and the primary subject of more than 250 years of research. Here we describe the history, development, and utility of the Hymenoptera Anatomy Ontology (HAO) and its associated applications. These resourc¬es are designed to facilitate accessible and extensible research on hymenopteran phenotypes. Outreach with the hymenopterist community is of utmost importance to the HAO project, and this paper is a direct response to questions that arose from project workshops. In a concerted attempt to surmount barriers of understanding, especially regarding the format, utility, and development of the HAO, we discuss the roles of homology, “preferred terms”, and “structural equivalency”. We also outline the use of Universal Resource Identifiers (URIs) and posit that they are a key element necessary for increasing the objectivity and repeatability of science that references hymenopteran anatomy. Pragmatically, we detail a mechanism (the “URI table”) by which authors can use URIs to link their published text to the HAO, and we describe an associated tool (the “Analyzer”) to derive these tables. These tools, and others, are available through the HAO Portal website (http://portal.hymao.org). We conclude by discussing the future of the HAO with respect to digital publication, cross-taxon ontology alignment, the advent of semantic phenotypes, and community-based curation.Katja C. Seltmann... Andrew D. Austin... John T. Jennings... et al

Modeling the Bombardier Beetle Fire Extinguisher: Verifying Computational Results

Undergraduate Applie

Bombardier Beetle Fire Extinguisher

Undergraduate Theoretical Proposa

Paridris Kieffer of the New World (Hymenoptera, Platygastroidea, Platygastridae)

Paridris in the New World is revised (Hymenoptera: Platygastridae). Fifteen species are described, of which 13 are new. Paridris aenea (Ashmead) (Mexico (Tamaulipas) and West Indies south to Bolivia and southern Brazil (Rio de Janeiro state)), P. armata Talamas, sp. n. (Venezuela), P. convexa Talamas, sp. n. (Costa Rica, Panama), P. dnophos Talamas, sp. n. (Mexico (Vera Cruz) south to Bolivia and central Brazil (Goiás)), P. gongylos Talamas & Masner, sp. n. (United States: Appalachian Mountains of Virginia, Tennessee, South Carolina), P. gorn Talamas & Masner, sp. n. (United States: Ohio south to Alabama, Georgia), P. invicta Talamas & Masner, sp. n. (Brazil: São Paulo), P. isabelicae Talamas & Masner, sp. n. (Cuba, Dominican Republic), P. lemete Talamas & Masner, sp. n. (Puerto Rico), P. minor Talamas, sp. n. (Cuba), P. nayakorum Talamas, sp. n. (Costa Rica), P. pallipes (Ashmead) (southeastern Canada, United States south to Costa Rica, also Brazil (São Paulo), P. psydrax Talamas & Masner, sp. n. (Argentina, Mexico, Paraguay, United States, Venezuela), P. saurotos Talamas, sp. n. (Jamaica), P. soucouyant Talamas & Masner, sp. n. (Colombia, Trinidad and Tobago, Venezuela). Paridris brevipennis Fouts, P. laeviceps (Ashmead), and P. nigricornis (Fouts) are treated as junior synonyms of P. pallipes; Paridris opaca is transferred to Probaryconus. Lectotypes are designated for Idris aenea Ashmead and Caloteleia aenea Ashmead